Astrophysics

New submissions

• New submissions
• Cross-lists
• Replacements

New submissions for Wed, 18 Nov 09

[1]  arXiv:0911.3143 [pdf, other]

Title: Epsilon Indi Ba, Bb: a detailed study of the nearest known brown dwarfs

Authors: Robert R. King (1), Mark J. McCaughrean (1 and 2), Derek Homeier (3), France Allard (4), Ralf-Dieter Scholz (5), Nicolas Lodieu (6) ((1) University of Exeter, (2) RSSD, ESA ESTEC (3) Georg-August-Universität, Göttingen, (4) CRAL, Lyon, (5) Astrophysikalisches Institut Potsdam, (6) IAC, Tenerife)

Comments: 27 pages, 30 figures, 9 tables, accepted for publication in Astronomy and Astrophysics

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The discovery of epsilon Indi Ba, Bb, a binary brown dwarf system very close to the Sun, makes possible a concerted campaign to characterise the physical parameters of two T dwarfs. Recent observations suggest substellar atmospheric and evolutionary models may be inconsistent with observations, but there have been few conclusive tests to date. We therefore aim to characterise these benchmark brown dwarfs to place constraints on such models. We have obtained high angular resolution optical, near-infrared, and thermal-infrared imaging and medium-resolution (up to R~5000) spectroscopy of epsilon Indi Ba, Bb with the ESO VLT and present VRIzJHKL'M' broad-band photometry and 0.63--5.1 micron spectroscopy of the individual components. Furthermore, we use deep AO-imaging to place upper limits on the (model-dependent) mass of any further system members. We derive luminosities of log L/L_sun = -4.699+/-0.017 and -5.232+/-0.020 for epsilon Indi Ba, Bb, respectively, and using the dynamical system mass and COND03 evolutionary models predict a system age of 3.7--4.3 Gyr, in excess of previous estimates and recent predictions from observations of these brown dwarfs. Moreover, the effective temperatures of 1352--1385 K and 976--1011 K predicted from the COND03 evolutionary models, for epsilon Indi Ba and Bb respectively, are in disagreement with those derived from the comparison of our data with the BT-Settl atmospheric models where we find effective temperatures of 1300--1340 K and 880--940 K, for epsilon Indi Ba and Bb respectively, with surface gravities of log g=5.25 and 5.50. Finally, we show that spectroscopically determined effective temperatures and surface gravities for ultra-cool dwarfs can lead to underestimated masses even where precise luminosity constraints are available.

[2]  arXiv:0911.3145 [ps, pdf, other]

Title: On the circular polarisation of light from axion-photon mixing

Authors: A. Payez, J.R. Cudell, D. Hutsemékers

Comments: Contributed to "Invisible Universe International Conference", Paris, June 29 - July 3 2009. To be published in AIP proceedings

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the sky has been reported. Here, we show that this can be explained by the mixing of the incoming photons with nearly massless pseudoscalar (axion-like) particles in extragalactic magnetic fields. We present a new treatment in terms of wave packets and discuss its implications for the circular polarisation.

[3]  arXiv:0911.3146 [ps, pdf, other]

Title: A Chandra X-ray Observatory Study of PSR J1740--5340 and Candidate Millisecond Pulsars in the Globular Cluster NGC 6397

Authors: Slavko Bogdanov, Maureen van den Berg, Craig O. Heinke, Haldan N. Cohn, Phyllis M. Lugger, Jonathan E. Grindlay

Comments: 10 pages, 6 figures, 3 tables; accepted for publication in The Astrophysical Journal

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a deep Chandra X-ray Observatory study of the peculiar binary radio millisecond pulsar PSR J1740--5340 and candidate millisecond pulsars (MSPs) in the globular cluster NGC 6397. The X-rays from PSR J1740--5340 appear to be non-thermal and exhibit variability at the binary period. These properties suggest the presence of a relativistic intrabinary shock formed due to interaction of a relativistic rotation-powered pulsar wind and outflow from the unusual "red-straggler/sub-subgiant" companion. We find the X-ray source U18 to show similar X-ray and optical properties to those of PSR J1740--5340, making it a strong MSP candidate. It exhibits variability on timescales from hours to years, also consistent with an intrabinary shock origin of its X-ray emission. The unprecedented depth of the X-ray data allows us to conduct a complete census of MSPs in NGC 6397. Based on the properties of the present sample of X-ray--detected MSPs in the Galaxy we find that NGC 6397 probably hosts no more than 6 MSPs.

[4]  arXiv:0911.3147 [ps, pdf, other]

Title: The Degeneracy of Galaxy Formation Models

Authors: Eyal Neistein, Simone M. Weinmann (MPA Garching)

Comments: Submitted to MNRAS

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)

We develop a new formalism for modeling the formation and evolution of galaxies within a hierarchical universe. Similarly to standard semi-analytical models we trace galaxies inside dark-matter merger-trees. The formalism includes treatment of feedback, star-formation, cooling, smooth accretion, gas stripping in satellite galaxies, and merger-induced star bursts. However, unlike in other models, each process is assumed to have an efficiency which depends only on the host halo mass and redshift. This allows us to describe the various components of the model in a simple and transparent way. By allowing the efficiencies to have any value for a given halo mass and redshift, we can easily encompass a large range of scenarios. To demonstrate this point, we examine several different galaxy formation models, which are all consistent with the observational data. Each model is characterized by a different unique feature: cold accretion in low mass haloes, zero feedback, stars formed only in merger-induced bursts, and shutdown of star-formation after mergers. Using these models we are able to examine the degeneracy inherent in galaxy formation models, and look for observational data that will help to break this degeneracy. We show that the full distribution of star-formation rates in a given stellar mass bin is promising in constraining the models. We compare our approach in detail to the semi-analytical model of De Lucia & Blaizot. It is shown that our formalism is able to produce a very similar population of galaxies once the same median efficiencies per halo mass and redshift are being used. We provide a public version of the model galaxies on our web-page, along with a tool for running models with user-defined parameters. Our model is able to provide results for a 62.5 h^{-1} Mpc box within just a few seconds.

[5]  arXiv:0911.3148 [ps, pdf, other]

Title: The CRIRES Search for Planets Around the Lowest-Mass Stars. I. High-Precision Near-Infrared Radial Velocities with an Ammonia Gas Cell

Authors: Jacob L. Bean, Andreas Seifahrt, Henrik Hartman, Hampus Nilsson, Guenter Wiedemann, Ansgar Reiners, Stefan Dreizler, Todd J. Henry

Comments: Submitted to ApJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Radial velocities measured from near-infrared spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields near-infrared radial velocity precision comparable to that which is routinely obtained in the visible. We describe a method for measuring high-precision relative radial velocities of cool stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the iodine cell technique that has been used so successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneously as well using spectrum synthesis with a time-resolved model of the atmosphere over the observatory. The free parameters in the complete model are the wavelength scale of the spectrum, the instrumental profile, adjustments to the water and methane abundances in the atmospheric model, telluric spectrum Doppler shift, and stellar Doppler shift. Tests of the method based on the analysis of hundreds of spectra obtained for late M dwarfs over six months demonstrate that precisions of ~ 5 m/s are obtainable over long timescales, and precisions of better than 3 m/s can be obtained over timescales up to a week. The obtained precision is comparable to the predicted photon-limited errors, but primarily limited over long timescales by the imperfect modeling of the telluric lines. (Abridged)

[6]  arXiv:0911.3149 [ps, pdf, other]

Title: On the magnetic field of off-limb spicules

Authors: R. Centeno (1), J. Trujillo Bueno (2 and 3), A. Asensio Ramos (2) ((1) High Altitude Observatory - NCAR, (2) Instituto de Astrofisica de Canarias, (3) Consejo Superior de Investigaciones Cientificas - Spain)

Comments: Accepted for publication in ApJ, 24 pages, 5 Figures

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Determining the magnetic field related to solar spicules is vital for developing adequate models of these plasma jets, which are thought to play a key role in the thermal, dynamic and magnetic structure of the Chromosphere. Here we report on the magnetic properties of off-limb spicules in a very quiet region of the solar atmosphere, as inferred from new spectropolarimetric observations in the He I 10830 A triplet obtained with the Tenerife Infrared Polarimeter. We have used a novel inversion code for Stokes profiles caused by the joint action of atomic level polarization and the Hanle and Zeeman effects (HAZEL) to interpret the observations. Magnetic fields as strong as ~40G were detected in a very localized area of the slit, which could represent a possible lower value of the field strength of organized network spicules.

[7]  arXiv:0911.3150 [ps, pdf, other]

Title: Unveiling the Origin of GRB 090709A: Lack of Periodicity in a Reddened Cosmological Long-Duration Gamma-Ray Burst

Authors: S. B. Cenko, N. R. Butler, E. O. Ofek, D. A. Perley, A. N. Morgan, D. A. Frail, J. Gorosabel, J. S. Bloom, A. J. Castro-Tirado, J. Cepa, P. C. Chandra, A. de Ugarte Postigo, A. V. Filippenko, C. R. Klein, S. R. Kulkarni, A. A. Miller, P. E. Nugent, D. L. Starr

Comments: 12 pages; 6 figures; Submitted to AJ; Comments welcome

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present broadband (gamma-ray, X-ray, near-infrared, optical, and radio) observations of the gamma-ray burst (GRB) 090709A and its afterglow in an effort to ascertain the origin of this high-energy transient. Previous analyses suggested that GRB 090709A exhibited quasi-periodic oscillations with a period of 8.06 s, a trait unknown in long-duration GRBs but typical of flares from soft gamma-ray repeaters. When properly accounting for the underlying shape of the power-density spectrum of GRB 090709A, we find no conclusive (> 3 sigma) evidence for the reported periodicity. In conjunction with the location of the transient (far from the Galactic plane and absent any nearby host galaxy in the local universe) and the evidence for extinction in excess of the Galactic value, we consider a magnetar origin relatively unlikely. A long-duration GRB, however, can account for the majority of the observed properties of this source. GRB 090709A is distinguished from other long-duration GRBs primarily by the large amount of obscuration from its host galaxy (A_K,obs >~ 2 mag).

[8]  arXiv:0911.3151 [ps, pdf, other]

Title: The propagation of uncertainties in stellar population synthesis modeling III: model calibration, comparison, and evaluation

Authors: Charlie Conroy, James E. Gunn

Comments: 26 pages, 16 figures, submitted to ApJ. The FSPS code can be downloaded at this http URL

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Stellar population synthesis (SPS) provides the link between the stellar and dust content of galaxies and their observed spectral energy distributions. In the present work we perform a comprehensive calibration of our own flexible SPS (FSPS) model against a suite of data. Several public SPS models are intercompared, including the models of Bruzual & Charlot (BC03), Maraston (M05) and FSPS. The relative strengths and weaknesses of these models are evaluated, with the following conclusions: 1) The FSPS and BC03 models compare favorably with MC data at all ages, whereas M05 colors are too red and the age-dependence is incorrect; 2) All models yield similar optical and near-IR colors for old metal-poor systems, and yet they all provide poor fits to the integrated J-K and V-K colors of both MW and M31 star clusters; 4) All models predict ugr colors too red, D4000 strengths too strong and Hdelta strengths too weak compared to massive red sequence galaxies, under the assumption that such galaxies are composed solely of old metal-rich stars; 5) FSPS and, to a lesser extent, BC03 can reproduce the optical and near-IR colors of post-starburst galaxies, while M05 cannot. Reasons for these discrepancies are explored. The failure at predicting the ugr colors, D4000, and Hdelta strengths can be explained by some combination of a minority population of metal-poor stars, young stars, blue straggler and/or blue horizontal branch stars, but not by appealing to inadequacies in either theoretical stellar atmospheres or canonical evolutionary phases (e.g., the main sequence turn-off). We emphasize that due to a lack of calibrating star cluster data in regions of the metallicity-age plane relevant for galaxies, all of these models continue to suffer from serious uncertainties that are difficult to quantify. (ABRIDGED)

[9]  arXiv:0911.3153 [ps, pdf, other]

Title: High resolution X-ray spectroscopy of the Seyfert 1 Mrk841: insights on the warm absorber and warm emitter gas

Authors: A.L. Longinotti, E. Costantini, P.O. Petrucci, C. Boisson, M. Mouchet, M. Santos-Lleo, G. Matt, G. Ponti, A. C. Goncalves

Comments: Accepted by Astronomy & Astrophysics, 9 pages, 6 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The Seyfert 1 galaxy Mrk841 was observed five times between 2001 and 2005 by the XMM-Newton X-ray observatory. The source is well known for showing spectral complexity in the variable iron line and in the soft X-ray excess. This paper reports on the first study of Mrk841 soft X-ray spectrum at high spectral resolution. The availability of multiple exposures obtained by the Reflection Grating Spectrometer (RGS) cameras allows a thorough study of the complex absorption and emission spectral features in the soft X-ray band.The three combined exposures obtained in January 2001 and the two obtained in January and July 2005 were analysed using the SPEX software. We detect a two-phase warm absorber: a medium ionisation component (logxi~1.5-2.2 ergs s cm^{-1}) is responsible for a deep absorption feature in the Unresolved Transition Array of the Fe M-shell and for several absorption lines in the OVI-VIII band; a higher ionisation phase with logxi~3 ergs s cm^{-1} is required to fit absorption in the NeIX-X band. The ionisation state and the column density of the gas present moderate variation from 2001 to 2005 for both phases. The high ionisation component of the warm absorber has no effect in the Fe K band. No significant velocity shift of the absorption lines is measured in the RGS data. Remarkably, the 2005 spectra show emission features consistent with photoionisation in a high density (n_e>10^{11} cm^{-3}) gas: a prominent OVII line triplet is clearly observed in January 2005 and narrow Radiative Recombination Continua (RRC) of OVII and CVI are observed in both 2005 data sets. A broad Gaussian line around 21.7 Angstrom is also required to fit all the data sets. The derived radial distance for the emission lines seems to suggest that the photoionisation takes place within the optical Broad Line Region of the source.

[10]  arXiv:0911.3154 [ps, pdf, other]

Title: Giant Planet Interior Structure and Thermal Evolution

Authors: Jonathan J. Fortney, Isabelle Baraffe, Burkhard Militzer

Comments: Invited chapter, in press for the Arizona Space Science Series book "Exoplanets," edited by S. Seager

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We discuss the interior structure and composition of giant planets, and how this structure changes as these planets cool and contract over time. Here we define giant planets as those that have an observable hydrogen-helium envelope, which includes Jupiter-like planets, which are predominantly H/He gas, and Neptune-like planets which are predominantly composed of elements heavier than H/He. We describe the equations of state of planetary materials and the construction of static structural models and thermal evolution models. We apply these models to transiting planets close to their parent stars, as well as directly imaged planets far from their parent stars. Mechanisms that have been postulated to inflate the radii of close-in transiting planets are discussed. We also review knowledge gained from the study of the solar system's giant planets. The frontiers of giant planet physics are discussed with an eye towards future planetary discoveries.

[11]  arXiv:0911.3155 [ps, pdf, other]

Title: The Quasar Mass-Luminosity Plane II: High Mass Turnoff Evolution and a Synchronization Puzzle

Authors: Charles L. Steinhardt, Martin Elvis

Comments: 10 pages, submitted to MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Galaxy Astrophysics (astro-ph.GA)

We use 62,185 quasars from the Sloan Digital Sky Survey DR5 sample and standard virial mass scaling laws based on the widths of H beta, Mg II, and C IV lines and adjacent continuum luminosities to explore the maximum mass of quasars as a function of redshift, which we find to be sharp and evolving. This evolution is in the sense that high-mass black holes cease their luminous accretion at higher redshift than lower-mass black holes. Further, turnoff for quasars at any given mass is more highly synchronized than would be expected given the dynamics of their host galaxies. We investigate potential signatures of the quasar turnoff mechanism, including a dearth of high-mass quasars at low Eddington ratio. These new results allow a closer examination of several common assumptions used in modeling quasar accretion and turnoff.

[12]  arXiv:0911.3156 [ps, pdf, other]

Title: Fake star formation bursts: blue horizontal branch stars masquerade as young stars in optical integrated light spectroscopy

Authors: P. Ocvirk

Comments: 14 pages, 6 figures, accepted for publication in ApJ

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Model color magnitude diagrams of low-metallicity globular clusters usually show a deficit of hot evolved stars with respect to observations. We investigate quantitatively the impact of such modelling inaccuracies on the significance of star formation history reconstructions obtained from optical integrated spectra. To do so, we analyse the sample of spectra of galactic globular clusters of Schiavon et al. with STECKMAP (Ocvirk et al.) and the stellar population models Vazdekis et al. and Bruzual & Charlot, and focus on the reconstructed stellar age distributions. Firstly, we show that background/foreground contamination correlates with E(B-V), which allows us to define a clean subsample of uncontaminated GCs, on the basis of a E(B-V) filtering.
We then identify a "confusion zone" where fake young bursts of star formation pop up in the star formation history although the observed population is genuinely old. These artifacts appear for 70-100% of cases depending on the population model used, and contribute up to 12% of the light in the optical. Their correlation with the horizontal branch ratio indicates that the confusion is driven by HB morphology: red horizontal branch clusters are well fitted by old stellar population models while those with a blue HB require an additional hot component. The confusion zone extends over [Fe/H]=[-2,-1.2], although we lack the data to probe extreme high and low metallicity regimes. As a consequence, any young starburst superimposed on an old stellar population in this metallicity range could be regarded as a modeling artifact, if it weighs less than 12% of the optical light, and if no emission lines typical of an HII region are present.

[13]  arXiv:0911.3161 [pdf, other]

Title: An analytic parameterization of self-gravity wakes in Saturn's rings, with application to occultations and propellers

Authors: Matthew S. Tiscareno, Randall P. Perrine, Derek C. Richardson, Matthew M. Hedman, John W. Weiss, Carolyn C. Porco, Joseph A. Burns

Comments: 28 pages, 9 figures; submitted to AJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We have developed a semi-analytic method of parameterizing N-body simulations of self-gravity wakes in Saturn's rings, describing their properties by means of only 6 numbers: 3 optical depths and 3 weighting factors. These numbers are obtained using a density-estimation procedure that finds the frequencies of various values of local density within a simulated ring patch.
Application of our parameterization to a suite of N-body simulations implies that the distribution of local optical depths is trimodal, rather than bimodal as previous authors have assumed. Rings dominated by self-gravity wakes appear to be mostly empty space.
The implications of this result for the analysis of occultation data are more conceptual than practical. The only adjustment needed is that the model parameter $\tau_{gap}$ should be interpreted as representing the area-weighted average optical depth within the gaps (or inter-wake regions).
The most significant consequence of our results applies to the question of why "propeller" structures observed in the mid-A ring are seen as relative-bright features, even though the most prominent features of simulated propellers are regions of relatively low density. We find preliminary quantitative support for the hypothesis that propellers would be bright if they involve a local and temporary disruption of self-gravity wakes, flooding the region with more "photometrically active" material (i.e., material that can contribute to the rings' local optical depth) even though the overall density is lower, and thus raising their apparent brightnesses in agreement with observations. We suggest that this mechanism be tested by future detailed numerical models.

[14]  arXiv:0911.3163 [ps, pdf, other]

Title: The Unifying Dark Fluid Model

Authors: Alexandre Arbey

Comments: 8 pages, 4 figures, contribution to the proceedings of the conference "Invisible Universe", Paris, June 29 - July 3, 2009, France

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

The standard model of cosmology relies on the existence of two components, "dark matter" and "dark energy", which dominate the expansion of the Universe. There is no direct proof of their existence, and their nature is still unknown. Many alternative models suggest other cosmological scenarios, and in particular the dark fluid model replace the dark matter and dark energy components by a unique dark component able to mimic the behaviour of both components. The current cosmological constraints on the unifying dark fluid model is discussed, and a dark fluid model based on a complex scalar field is presented. Finally the consequences of quantum corrections on the scalar field potential are investigated.

[15]  arXiv:0911.3166 [ps, pdf, other]

Title: An HST/WFPC2 survey of bright young clusters in M31. IV. Ages and mass estimates

Authors: S. Perina (UniBO/OABO), J.G. Cohen (CalTech), P. Barmby (Univ. W. Ontario), M.A. Beasley (UCO/Lick), M. Bellazzini (INAF-OABO), J.P. Brodie (UCO/Lick), L. Federici (INAF-OABO), F. Fusi Pecci (INAF-OABO), S. Galleti (INAF-OABO), P.W. Hodge (Univ. of Washington), J.P. Huchra (CfA), M. Kissler-Patig (ESO), T.H. Puzia (Herzberg Inst.), J. Strader (CfA)

Comments: 31 pages, 21 figures (quality of Figures 1 and 2 reduced), uses longtable.sty. Accepted for publication in Astronomy and Astrophysics. A high-resolution version of the paper is available at this http URL

Subjects: Galaxy Astrophysics (astro-ph.GA)

{Aims.} We present the main results of an imaging survey of possible young massive clusters (YMC) in M31 performed with the Wide Field and Planetary Camera2 (WFPC2) on the Hubble Space Telescope (HST). We present the images and color magnitude diagrams (CMDs) of all of our targets. {Methods.} The reddening, age and, metallicity of the clusters were estimated by comparing the observed CMDs and luminosity functions with theoretical models. Stellar masses were estimated by comparison with theoretical models in the log(Age) vs. absolute integrated magnitude plane. {Results.} Nineteen of the twenty surveyed candidates were confirmed to be real star clusters. Three of the clusters were found not to be good YMC candidates from newly available integrated spectroscopy and were in fact found to be old from their CMD. Of the remaining sixteen clusters, fourteen have ages between 25 Myr and 280 Myr, two have older ages than 500 Myr (lower limits). By including ten other YMC with HST photometry from the literature we have assembled a sample of 25 clusters younger than 1 Gyr, with mass ranging from 0.6 x 10^4 M_sun to 6 x 10^4 M_sun, with an average of ~ 3 x 10^4 M_sun. {Conclusions.} The clusters considered here are confirmed to have masses significantly higher than Galactic open clusters in the same age range. Our analysis indicates that YMCs are relatively common in all the largest star-forming galaxies of the Local Group.

[16]  arXiv:0911.3170 [pdf, other]

Title: Atmospheric Circulation of Exoplanets

Authors: Adam P. Showman, James Y-K. Cho, Kristen Menou

Comments: In EXOPLANETS, edited by S. Seager, to be published in the Spring of 2010 in the Space Science Series of the University of Arizona Press (Tucson, AZ) (refereed; accepted for publication)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We survey the basic principles of atmospheric dynamics relevant to explaining existing and future observations of exoplanets, both gas giant and terrestrial. Given the paucity of data on exoplanet atmospheres, our approach is to emphasize fundamental principles and insights gained from Solar-System studies that are likely to be generalizable to exoplanets. We begin by presenting the hierarchy of basic equations used in atmospheric dynamics, including the Navier-Stokes, primitive, shallow-water, and two-dimensional nondivergent models. We then survey key concepts in atmospheric dynamics, including the importance of planetary rotation, the concept of balance, and scaling arguments to show how turbulent interactions generally produce large-scale east-west banding on rotating planets. We next turn to issues specific to giant planets, including their expected interior and atmospheric thermal structures, the implications for their wind patterns, and mechanisms to pump their east-west jets. Hot Jupiter atmospheric dynamics are given particular attention, as these close-in planets have been the subject of most of the concrete developments in the study of exoplanetary atmospheres. We then turn to the basic elements of circulation on terrestrial planets as inferred from Solar-System studies, including Hadley cells, jet streams, processes that govern the large-scale horizontal temperature contrasts, and climate, and we discuss how these insights may apply to terrestrial exoplanets. Although exoplanets surely possess a greater diversity of circulation regimes than seen on the planets in our Solar System, our guiding philosophy is that the multi-decade study of Solar-System planets reviewed here provides a foundation upon which our understanding of more exotic exoplanetary meteorology must build.

[17]  arXiv:0911.3172 [ps, pdf, other]

Title: Power for Dry BL Lacs

Authors: A. Paggi, A. Cavaliere, V. Vittorini, M. Tavani

Comments: 4 pages, 3 figures, accepted by A&A

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

Is it significant that the intrinsic outputs of several BL Lacs are observed to top at about ({10}^{46}{erg}{s}^{-1})? Toward an answer, we compare recent observations in (\gamma) rays with the \emph{AGILE} satellite of the BL Lac S5 0716+714 with those of Mrk 421 and Mrk 501. The former are particularly marked by intense flares up to fluxes of (2\times{10}^{-6}{photons}{cm}^{-2}{s}^{-1}) in the (0.1-10{GeV}) energy range.
These "dry" BL Lacs show no evidence of thermal disk emissions nor emission lines signaling any accreting or surrounding gas; the spectral distributions of their pure non-thermal radiations are effectively represented in terms of the synchrotron-self Compton process.
With source parameters so derived, focused and tuned with simultaneous multi-wavelength observations, we find for S5 0716+714 a total jet power of about (3\times{10}^{45}{erg}{s}^{-1}), that makes it one of the brightest dry BL Lacs so far detected in (\gamma) rays.
With a mass for the associated Kerr hole that we evaluate at around (5\times{10}^8 M_{\tiny{\astrosun}}), the source is significantly benchmarked by the maximal power around (4\times{10}^{45}{erg}{s}^{-1}) extractable via the Blandford-Znajek electrodynamic mechanism; other dry BL Lacs observed in (\gamma) rays remain well below that threshold. These findings and those coming from \emph{Fermi}-LAT will provide a powerful test of electrodynamics in the hole surroundings dominated by GR effects.

[18]  arXiv:0911.3176 [ps, pdf, other]

Title: The Taurus Spitzer Survey: New Candidate Taurus Members Selected Using Sensitive Mid-Infrared Photometry

Authors: L. M. Rebull (Spitzer Science Center), D. L. Padgett (Spitzer Science Center), C.-E. McCabe (Spitzer Science Center), L. A. Hillenbrand (Caltech), K. R. Stapelfeldt (Jet Propulsion Laboratory), A. Noriega-Crespo (Spitzer Science Center), S. J. Carey (Spitzer Science Center), T. Brooke (Spitzer Science Center), T. Huard (University of Maryland, College Park), S. Terebey (California State University, Los Angeles), M. Audard (ISDC Data Center for Astrophysics and Observatoire de Geneve), J.-L. Monin (LAOG), M. Fukagawa (Osaka University), M. Guedel (ETH Zurich, Institute of Astronomy), G. R. Knapp (Princeton University), F. Menard (LAOG), L. E. Allen (NOAO), J. R. Angione (JPL and CSULA), C. Baldovin-Saavedra (ISDC Data Center for Astrophysics and Observatoire de Geneve), J. Bouvier (LAOG), et al. (14 additional authors not shown)

Comments: Accepted to ApJS. Two large online-only figures available with the preprint here: this http URL

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We report on the properties of pre-main-sequence objects in the Taurus molecular clouds as observed in 7 mid- and far-infrared bands with the Spitzer Space Telescope. There are 215 previously-identified members of the Taurus star-forming region in our ~44 square degree map; these members exhibit a range of Spitzer colors that we take to define young stars still surrounded by circumstellar dust (noting that ~20% of the bonafide Taurus members exhibit no detectable dust excesses). We looked for new objects in the survey field with similar Spitzer properties, aided by extensive optical, X-ray, and ultraviolet imaging, and found 148 candidate new members of Taurus. We have obtained follow-up spectroscopy for about half the candidate sample, thus far confirming 34 new members, 3 probable new members, and 10 possible new members, an increase of 15-20% in Taurus members. Of the objects for which we have spectroscopy, 7 are now confirmed extragalactic objects, and one is a background Be star. The remaining 93 candidate objects await additional analysis and/or data to be confirmed or rejected as Taurus members. Most of the new members are Class II M stars and are located along the same cloud filaments as the previously-identified Taurus members. Among non-members with Spitzer colors similar to young, dusty stars are evolved Be stars, planetary nebulae, carbon stars, galaxies, and AGN.

[19]  arXiv:0911.3177 [ps, pdf, other]

Title: A Star in the M31 Giant Stream: the Highest Negative Stellar Velocity Known

Authors: N. Caldwell (CfA), H. Morrison (Case), S.J. Kenyon (CfA), R. Schiavon (Gemini), P. Harding (Case), J.A. Rose (UNC)

Comments: to appear in AJ

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Solar and Stellar Astrophysics (astro-ph.SR)

We report on a single star, B030D, observed as part of a large survey of objects in M31, which has the unusual radial velocity of -780 km/s. Based on details of its spectrum, we find that the star is an F supergiant, with a circumstellar shell. The evolutionary status of the star could be one of a post-mainsequence close binary, a symbiotic nova, or less likely, a post-AGB star, which additional observations could help sort out. Membership of the star in the Andromeda Giant Stream can explain its highly negative velocity.

[20]  arXiv:0911.3180 [ps, pdf, other]

Title: The Distance to NGC 5128 (Centaurus A)

Authors: Gretchen L. H. Harris, Marina Rejkuba, William E. Harris

Comments: in press PASA

Subjects: Galaxy Astrophysics (astro-ph.GA)

In this paper we review the various high precision methods that are now available to determine the distance to NGC 5128. These methods include: Cepheids, TRGB (tip of the red giant branch), PNLF (planetary nebula luminosity function), SBF (surface brightness fluctuations) and Long Period Variable (LPV) Mira stars. From an evaluation of these methods and their uncertainties, we derive a best-estimate distance of 3.8 +- 0.1 Mpc to NGC 5128 and find that this mean is now well supported by the current data. We also discuss the role of NGC 5128 more generally for the extragalactic distance scale as a testbed for the most direct possible comparison among these key methods.

[21]  arXiv:0911.3198 [ps, pdf, other]

Title: Constraining the Dark Energy Equation of State using Alternative High-z Cosmic Tracers

Authors: M. Plionis, R. Terlevich, S. Basilakos, F. Bressolin, E. Terlevich, J. Melnick, R. Chavez

Comments: 10 pages, 5 figures, "Dark Universe" conference (Paris, July 2009)

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We propose to use alternative cosmic tracers to measure the dark energy equation of state and the matter content of the Universe [w(z) & Omega_m]. Our proposed method consists of two components: (a) tracing the Hubble relation using HII galaxies which can be detected up to very large redshifts, z~4, as an alternative to supernovae type Ia, and (b) measuring the clustering pattern of X-ray selected AGN at a median redshift of z~1. Each component of the method can in itself provide interesting constraints on the cosmological parameters, especially under our anticipation that we will reduce the corresponding random and systematic errors significantly. However, by joining their likelihood functions we will be able to put stringent cosmological constraints and break the known degeneracies between the dark energy equation of state (whether it is constant or variable) and the matter content of the universe and provide a powerful and alternative route to measure the contribution to the global dynamics and the equation of state of dark energy. A preliminary joint analysis of X-ray selected AGN (based on the largest to-date XMM survey; the 2XMM) and the currently largest SNIa sample (Hicken et al.), using as priors a flat universe and the WMAP5 normalization of the power-spectrum, provides: Omega_m=0.27 +- 0.02 and w=-0.96 +- 0.07.

[22]  arXiv:0911.3200 [pdf]

Title: Terrestrial Planet Finder Coronagraph (TPF-C) Flight Baseline Concept

Authors: Marie Levine, D. Lisman, S. Shaklan, J. Kasting, W. Traub, J. Alexander, R. Angel, C. Blaurock, M. Brown, R. Brown, C. Burrows, M. Clampin, E. Cohen, D. Content, L. Dewell, P. Dumont, R. Egerman, H. Ferguson, V. Ford, J. Greene, O. Guyon, H. Hammel, S. Heap, T. Ho, S. Horner, S. Hunyadi, S. Irish, C. Jackson, J. Kasdin, A. Kissil, M. Krim, M. Kuchner, E. Kwack, C. Lillie, D. Lin, A. Liu, L. Marchen, M. Marley, V. Meadows, G. Mosier, P. Mouroulis, M. Noecker, R. Ohl, B. Oppenheimer, J. Pitman, S. Ridgway, E. Sabatke, S. Seager, M. Shao, A. Smith, R. Soummer, K. Stapelfeldt, D. Tenerell, J. Trauger, R. Vanderbei

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The Terrestrial Planet Finder Coronagraph (TPF-C) mission presented here is an existence proof for a flagship-class internal coronagraph space mission capable of detecting and characterizing Earth-like planets and planetary systems at visible wavelengths around nearby stars, using an existing launch vehicle. TPF-C will use spectroscopy to measure key properties of exoplanets including the presence of atmospheric water or oxygen, powerful signatures in the search for habitable worlds.

[23]  arXiv:0911.3216 [ps, pdf, other]

Title: Optical Characteristics of the Astrometric Radio Sources

Authors: Zinovy Malkin, Oleg Titov

Comments: 6 pp., presented at the 5th IVS General Meeting, St. Petersburg, Russia, 3-6 March 2007

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

A new list of physical characteristics of 3914 astrometric radio sources, including all 717 ICRF-Ext.2 sources, observed during IVS and NRAO VCS sessions have been compiled. The list includes source type, redshift and visual magnitude (if available). In case of doubt detailed comment is provided. The list of sources with their positions was taken from the Goddard VLBI astrometric catalog with addition of two ICRF-Ext.2 sources. At this stage the source characteristics were mainly taken from the NASA/IPAC Extragalactic Database (NED). 667 sources from our list are included into the IERS list. Comparison has shown a significant difference in characteristics for about half of these 667 common sources. We compiled a list of frequently observed sources without known physical characteristics for urgent optical identification and spectrophotometric observations with large optical telescopes. This presented list of physical characteristics can be used as a supplement material for the ICRF-2, as well as a database for kinematic studies of the Universe and other related works, including scheduling of dedicated IVS programs.

[24]  arXiv:0911.3221 [ps, pdf, other]

Title: Effect of asymmetry of the radio source distribution on the apparent proper motion kinematic analysis

Authors: Oleg Titov, Zinovy Malkin

Comments: 9 pages

Journal-ref: Astron. Astrophys., 2009, v. 506, No. 3, 1477-1485

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

A new list of physical characteristics of 4261 astrometric radio sources, including all 717 ICRF-Ext.2 sources has been compiled. Comparison of our data of optical characteristics with the official International Earth Rotation and Reference Systems Service (IERS) list showed significant discrepancies for about half of 667 common sources. We also found that asymmetry in the radio sources distribution between hemispheres could cause significant correlation between the vector spherical harmonics, especially if the case of sparse distribution of the sources with high redshift. We identified radio sources having many-year observation history and lack redshift. This sources should be urgently observed at large optical telescopes. The list of optical characteristics created in this paper is recommended for use as a supplement material for the next International Celestial Reference Frame (ICRF) realization. It can be also effectively used for cosmological studies and planning of observing programs both in radio and optics.

[25]  arXiv:0911.3222 [ps, pdf, other]

Title: Simulations of the Magneto-rotational Instability in Core-Collapse Supernovae

Authors: M. Obergaulinger, P. Cerdà-Duràn, E. Müller, M.A. Aloy

Comments: 6 pages, 1 figure. To appear in Proceedings of 4th International Conference on Numerical Modeling of Space Plasma Flows (Chamonix 2009)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We assess the importance of the magneto-rotational instability in core-collapse supernovae by an analysis of the growth rates of unstable modes in typical post-collapse systems and by numerical simulations of simplified models. The interplay of differential rotation and thermal stratification defines different instability regimes which we confirm in our simulations. We investigate the termination of the growth of the MRI by parasitic instabilities, establish scaling laws characterising the termination amplitude, and study the long-term evolution of the saturated turbulent state.

[26]  arXiv:0911.3232 [ps, pdf, other]

Title: AMiBA: scaling relations between the integrated Compton-y and X-ray derived temperature, mass, and luminosity

Authors: Chih-Wei Locutus Huang (1,2), Jiun-Huei Proty Wu (1,2), Paul T. P. Ho (3,4), Patrick M. Koch (3), Yu-Wei Liao (1,2), Kai-Yang Lin (1,3), Guo-Chin Liu (3,5), Sandor M. Molnar (3), Hiroaki Nishioka (3), Keiichi Umetsu (2,3), Fu-Cheng Wang (1,2), Pablo Altamirano (3), Mark Birkinshaw (6), Chia-Hao Chang (3), Shu-Hao Chang (3), Su-Wei Chang (3), Ming-Tang Chen (3), Tzihong Chiueh (1,2), Chih-Chiang Han (3), Yau-De Huang (3), Yuh-Jing Hwang (3), Homin Jiang (3), Michael Kesteven (7), Derek Kubo (3), Chao-Te Li (3), Pierre Martin-Cocher (3), Peter Oshiro (3), Philippe Raffin (3), Tashun Wei (3), Warwick Wilson (7) ((1)Department of Physics, Institute of Astrophysics, & Center for Theoretical Sciences, National Taiwan University, (2)LeCosPA Center, National Taiwan University, (3)Institute of Astronomy and Astrophysics, Academia Sinica, (4)Harvard-Smithsonian Center for Astrophysics, (5)Department of Physics, Tamkang University, (6)Department of Physics, University of Bristol, (7)Australia Telescope National Facility)

Comments: Accepted by ApJ; 8 pages, 3 figures, 5 tables

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We investigate the scaling relations between the X-ray and the thermal Sunyaev-Zel'dovich Effect (SZE) properties of clusters of galaxies, using data taken during 2007 by the Y.T. Lee Array for Microwave Background Anisotropy (AMiBA) at 94 GHz for the six clusters A1689, A1995, A2142, A2163, A2261, and A2390. The scaling relations relate the integrated Compton-y parameter Y_{2500} to the X-ray derived gas temperature T_{e}, total mass M_{2500}, and bolometric luminosity L_X within r_{2500}. Our results for the power-law index and normalization are both consistent with the self-similar model and other studies in the literature except for the Y_{2500}-L_X relation, for which a physical explanation is given though further investigation may be still needed. Our results not only provide confidence for the AMiBA project but also support our understanding of galaxy clusters.

[27]  arXiv:0911.3240 [ps, pdf, other]

Title: Large prebiotic molecules in space: photo-physics of acetic acid and its isomers

Authors: Fabrizio Puletti, Giuliano Malloci, Giacomo Mulas, Cesare Cecchi-Pestellini

Comments: 8 pages, 5 figures

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Chemical Physics (physics.chem-ph)

An increasing number of large molecules have been positively identified in space. Many of these molecules are of biological interest and thus provide insight into prebiotic organic chemistry in the protoplanetary nebula. Among these molecules, acetic acid is of particular importance due to its structural proximity to glycine, the simplest amino acid. We compute electronic and vibrational properties of acetic acid and its isomers, methyl formate and glycolaldehyde, using density functional theory. From computed photo-absorption cross-sections, we obtain the corresponding photo-absorption rates for solar radiation at 1 AU and find them in good agreement with previous estimates. We also discuss glycolaldehyde diffuse emission in Sgr B2(N), as opposite to emissions from methyl formate and acetic acid that appear to be concentrate in the compact region Sgr B2(N-LMH).

[28]  arXiv:0911.3243 [ps, pdf, other]

Title: A re--analysis of the iron line in the XMM-Newton data from the low/hard state in GX339--4

Authors: Chris Done, Maria Diaz Trigo

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The detection of an extremely broad iron line in XMM-Newton MOS data from the low/hard state of the black hole binary GX339-4 is the only piece of evidence which unambiguously conflicts with the otherwise extremely successful truncated disc interpretation of this state. However, it also conflicts with some aspect of observational data for all other alternative geometries of the low/hard state, including jet models, making it very difficult to understand. We reanalyse these data and show that they are strongly affected by pileup as the source is ~200x brighter than the recommended maximum countrate. Instead, we extract the simultaneous PN timing mode data which should not be affected by pileup. These show a line which is significantly narrower than in the MOS data. Thus these data are easily consistent with a truncated disc, and indeed, strongly support such an interpretation.

[29]  arXiv:0911.3247 [pdf, other]

Title: The formation of disks in massive spiral galaxies

Authors: F. Hammer, M. Puech, H. Flores

Comments: AIP Proceedings of a review given at the "Invisible Universe International Conference" held in Paris, June 2009. 16 pages, 9 Figures

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

The flatness of the rotation curve inside spiral galaxies is interpreted as the imprint of a halo of invisible matter. Using the deepest observations of distant galaxies, we have investigated how large disks could have been formed. Observations include spatially resolved kinematics, detailed morphologies and photometry from UV to mid-IR. Six Giga-years ago, half of the present-day spirals had anomalous kinematics and morphologies that considerably affect the scatter of the Tully Fisher relation. All anomalous galaxies can be modelled through gas-rich, major mergers that lead to a rebuilt of a new disk. The spiral-rebuilding scenario is proposed as a new channel to form large disks in present-day spirals and it accounts for all the observed evolutions since the last 6 Giga-years. A large fraction of the star formation is linked to merging events during their whole durations.

[30]  arXiv:0911.3269 [ps, pdf, other]

Title: Instabilities in dark coupled models and constraints from cosmological data

Authors: L. Lopez Honorez, 0. Mena

Comments: To be published in the proceedings of the Invisible Universe International Conference (Paris, 29 June - 3 July 2009)

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Coupled dark matter-dark energy systems can suffer from non-adiabatic instabilities at early times and large scales. In these proceedings, we consider two parameterizations of the dark sector interaction. In the first one the energy-momentum transfer 4-vector is parallel to the dark matter 4-velocity and in the second one to the dark energy 4-velocity. In these cases, coupled models which suffer from non-adiabatic instabilities can be identified as a function of a generic coupling Q and of the dark energy equation of state. In our analysis, we do not refer to any particular cosmic field. We confront then a viable class of models in which the interaction is directly proportional to the dark energy density and to the Hubble rate parameter to recent cosmological data. In that framework, we show that correlations between the dark coupling and several cosmological parameters allow for a larger neutrino mass than in uncoupled models.

[31]  arXiv:0911.3271 [ps, pdf, other]

Title: How Common are Extrasolar, Late Heavy Bombardments?

Authors: Mark Booth (1), Mark C. Wyatt (1), Alessandro Morbidelli (2), Amaya Moro-Martín (3 and 4), Harold F. Levison (5) ((1) IoA, (2) OCA, (3) CAB, (4) Princeton, (5) SWRI)

Comments: 2 pages, 1 figure. Contribution to the conference proceedings for 'Pathways towards habitable planets'

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The habitability of planets is strongly affected by impacts from comets and asteroids. Indications from the ages of Moon rocks suggest that the inner Solar System experienced an increased rate of impacts roughly 3.8 Gya known as the Late Heavy Bombardment (LHB). Here we develop a model of how the Solar System would have appeared to a distant observer during its history based on the Nice model of Gomes et al. (2005). We compare our results with observed debris discs. We show that the Solar System would have been amongst the brightest of these systems before the LHB. Comparison with the statistics of debris disc evolution shows that such heavy bombardment events must be rare occurring around less than 12% of Sun-like stars.

[32]  arXiv:0911.3272 [ps, pdf, other]

Title: On high brightness temperature of pulsar giant pulses

Authors: V.M.Kontorovich

Comments: 18 pages, 2 Postscript figures; The 8th International Conference on Physics of Neutron Stars - 2008 in Saint-Petersburg, Ioffe Physical-Technical Institute, eds.D. A. Varshalovich, A. I. Chugunov,A. Y. Potekhin and D. G. Yakovlev, Saint-Petersburg: Saint-Petersburg State Polytechnical University Publishing, p.52 (2008)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

Giant pulses observed in a number of pulsars show a record brightness temperature which corresponds to the high energy density of 10^15 erg/cm^3. Comparable densities of energy in the radio-frequency region are attainable in a cavity-resonator being the pulsar internal vacuum gap. Energy emission through the breaks accidentally appearing in the magnetosphere of open field lines corresponds to the giant pulses. The emitted energy is defined by the break area, which causes a power dependence of break occurrence probability. The observed localization of giant pulses as to the average pulse is explained by radiation through a waveguide near the magnetic axis or through a slot on the border of the open field lines. Separate discharges may be superimposed on the radiation through the breaks forming the fine structure of giant pulses with duration up to some nanoseconds. Coulomb repulsion of particles in the puncture spark in the gap leads to spark rotation around its axis in the crossed fields, which provokes the appearance of observed circular polarization of giant pulses. The correlation between GP phase and the phase of the hard pulsar radiation (X-ray and gamma) also is naturally explained.
Thus, a wide range of events observed at giant pulses can be explained from the viewpoint, that the internal vacuum gap is a cavity-resonator stimulated by discharges and radiating through the breaks in the magnetosphere.

[33]  arXiv:0911.3279 [ps, pdf, other]

Title: A new method for computing the eigenfunctions and their adjoints of the dynamo operator

Authors: M. Schrinner, D. Schmitt, J. Jiang, P. Hoyng

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We present a new method to determine the eigensolutions of the induction and the dynamo equation in a fluid embedded in vacuum. The magnetic field is expanded in a complete set of functions. The new method is based on the biorthogonality of the adjoint electric current and the vector potential with an inner product defined by a volume integral over the fluid domain. The advantage of this method is that the velocity and the dynamo coefficients of the induction and the dynamo equation do not have to be differentiated and thus even numerically determined tabulated values of the coefficients produce reasonable results. We provide test calculations and compare with published results obtained by the classical treatment based on the biorthogonality of the magnetic field and its adjoint. We especially consider dynamos with mean-field coefficients determined from direct numerical simulations of the geodynamo and compare with initial value calculations and the full MHD simulations.

[34]  arXiv:0911.3281 [ps, pdf, other]

Title: Limits on spin determination from disc spectral fitting in GX 339-4

Authors: Mari Kolehmainen, Chris Done

Comments: 6 pages, submitted to MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We attempt to constrain the black hole spin in GX339-4 from spectral fitting of disc dominated data using RXTE spectra from the three most recent outbursts. We use the best current models for the disc emission, including full radiative transfer through the photosphere rather than assuming that the intrinsic emission from each radius has a (colour temperature corrected) blackbody spectrum. The results strongly depend on the poorly known binary system parameters, but we find a strict upper limit of a < 0.9 for any distance greater than 6kpc assuming that the orbital inclination is the same as that of the inner disc. By contrast, the higher spin of 0.935 +/- 0.01 (statistical) +/-0.01 (systematic) claimed from fitting the iron line profile in this object requires that the inner disc is misaligned by over 20 degrees from the orbital inclination. Such a large misalignment seems unlikely, and is also at odds with the higher inclination suggested by the presence of absorption lines from a disc wind. Instead, recent results have shown that these line profiles in GX339-4 are potentially distorted by instrumental effects. Thus there is no strong requirement to modify models of supernovae collapse which predict maximum black hole spin of ~0.8.

[35]  arXiv:0911.3285 [ps, pdf, other]

Title: A 3D radiative transfer framework: VI. PHOENIX/3D example applications

Authors: Peter H. Hauschildt, E. Baron

Comments: A&amp;A, in press (Ref: AA/2009/13064)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We demonstrate the application of our 3D radiative transfer framework in the model atmosphere code PHOENIX/3D for a number of spectrum synthesis calculations for very different conditions. The 3DRT framework discussed in the previous papers of this series was added to our general-purpose model atmosphere code PHOENIX/1D and an extended 3D version PHOENIX/3D was created. The \phxT code is parallelized via the MPI library using a hierarchical domain decomposition and displays very good strong scaling. We present the results of several test cases for widely different atmosphere conditions and compare the 3D calculations with equivalent 1D models to assess the internal accuracy of the 3D modeling. In addition, we show the results for a number of parameterized 3D structures. With presently available computational resources it is possible to solve the full 3D radiative transfer (including scattering) problem with the same micro-physics as included in 1D modeling.

[36]  arXiv:0911.3302 [ps, pdf, other]

Title: LoCuSS: First Results from Strong-lensing Analysis of 20 Massive Galaxy Clusters at z~0.2

Authors: Johan Richard (Durham), Graham Smith (Birmingham), Jean-Paul Kneib (Marseille), Richard Ellis (Caltech), Alastair Sanderson (Birmingham), Liuyi Pei (Caltech), Thomas Targett (UBC), David Sand (Harvard), Mark Swinbank (Durham), Helmut Dannerbauer (Heidelberg), Pascuale Mazzotta (Roma), Marceau Limousin (Marseille), Eiichi Egami (Tucson), Eric Jullo (JPL), Victoria Hamilton-Morris (Birmingham), Sean Moran (Johan Hopkins)

Comments: 26 pages, 14 figures, resubmitted to MNRAS, including response to the referee

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We present a statistical analysis of a sample of 20 strong lensing clusters drawn from the Local Cluster Substructure Survey (LoCuSS), based on high resolution Hubble Space Telescope imaging of the cluster cores and follow-up spectroscopic observations using the Keck-I telescope. We use detailed parameterized models of the mass distribution in the cluster cores, to measure the total cluster mass and fraction of that mass associated with substructures within R<250kpc.These measurements are compared with the distribution of baryons in the cores, as traced by the old stellar populations and the X-ray emitting intracluster medium. Our main results include: (i) the distribution of Einstein radii is log-normal, with a peak and 1sigma width of <log(RE(z=2))>=1.16+/-0.28; (ii) we detect an X-ray/lensing mass discrepancy of <M_SL/M_X>=1.3 at 3 sigma significance -- clusters with larger substructure fractions displaying greater mass discrepancies, and thus greater departures from hydrostatic equilibrium; (iii) cluster substructure fraction is also correlated with the slope of the gas density profile on small scales, implying a connection between cluster-cluster mergers and gas cooling. Overall our results are consistent with the view that cluster-cluster mergers play a prominent role in shaping the properties of cluster cores, in particular causing departures from hydrostatic equilibrium, and possibly disturbing cool cores. Our results do not support recent claims that large Einstein radius clusters present a challenge to the CDM paradigm.

[37]  arXiv:0911.3313 [ps, pdf, other]

Title: Short-duration gamma-ray bursts from off-axis collapsars

Authors: Davide Lazzati (NCSU), Brian J. Morsony (UW Madison), Mitchell C. Begelman (JILA)

Comments: 5 pages, 6 color figures, submitted to ApJL. Comments welcome

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We present 2D high resolution hydrodynamic simulations of the relativistic outflows of long-duration gamma-ray burst progenitors. We analyze the properties of the outflows at wide off-axis angles, produced by the expansion of the hot cocoon that surrounds the jet inside the progenitor star. We find that the cocoon emission at wide angles has properties that are strikingly similar to the properties of the subclass of short-duration gamma-ray bursts with persistent X-ray emission. We compute the predicted duration distribution, redshift distribution, and afterglow brightness and we find that they are all in agreement with the observed properties of short GRBs with persistent emission. We suggest that late afterglow observations can be used as a crucial test to verify this model.

[38]  arXiv:0911.3316 [ps, pdf, other]

Title: Companion stars of Type Ia supernovae and hypervelocity stars

Authors: Bo Wang, Zhanwen Han

Comments: 4 pages, 5 figures, accepted for publication in A&amp;A letters

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

{Context} Recent investigations on the white dwarf (WD) + He star channel of Type Ia supernovae (SNe Ia) imply that this channel can produce SNe Ia with short delay times. The companion stars in this channel would survive and be potentially identifiable. {Aims} In this Letter, we study the properties of the companion stars of this channel at the moment of SN explosion, which can be verified by future observations. {Methods} According to SN Ia production regions of the WD + He star channel (Wang et al. 2009a) and three formation channels of WD + He star systems (Wang et al. 2009b), we performed a detailed binary population synthesis study to obtain the properties of the surviving companions. {Results} We obtained the distributions of many properties of the companion stars of this channel at the moment of SN explosion. We find that the surviving companion stars have a high spatial velocity (>400 km/s) after SN explosion, which could be an alternative origin for hypervelocity stars (HVSs), especially for HVSs such as US 708.

[39]  arXiv:0911.3319 [ps, pdf, other]

Title: On the power spectrum of solar surface flows

Authors: M. Rieutord, T. Roudier, F. Rincon, J.-M. Malherbe, N. Meunier, T. Berger, Z. Frank

Comments: 10 p., 6., abridged abstract, accepted in Astronomy and Astrophysics

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The aim of this work is to give new observational constraints on solar surface flows by determining the horizontal scale dependence of the velocity and intensity fields, as represented by their power spectra, and to offer some theoretical guidelines to interpret these spectra. We use long time series of images taken by SOT/Hinode and reconstruct both horizontal (by granule tracking) and vertical (by Doppler effect) velocity fields in a field of view 75x75Mm^2. At small sub-granulation scales, the kinetic energy spectral density associated with vertical motions exhibits a k^{-13/3}-like spectrum, while the intensity fluctuation spectrum follows a k^{-17/3}-like spectrum. We discuss the physical origin of these scalings and argue that they provide a direct observational signature of buoyancy-driven turbulent dynamics in a strongly thermally diffusive regime. In the mesogranulation range and up to a scale of 25Mm, we find that the vertical velocity field amplitude decreases like L^{-3/2} with the horizontal scale L. This behaviour corresponds to a k^2 spectral power law. Still in the mesoscale range, [2.5, 10]Mm, we find that intensity fluctuations follow a power law in k^{1.7}. We show that granule tracking cannot sample scales below 2.5Mm. We locate the supergranulation energy peak around 30Mm and show that the emergence of a pore erases this spectral peak. Thanks to a scale height estimate, we find that supergranular flows are shallow (abridged abstract).

[40]  arXiv:0911.3320 [ps, pdf, other]

Title: Timescale of Mass Accretion in Pre-Main-Sequence Stars

Authors: D. Fedele (MPIA), M. E. van den Ancker (ESO), Th. Henning (MPIA), R. Jayawardhana (University of Toronto), J. M. Oliveira (Keele University)

Comments: Accepted for publication

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

We present initial result of a large spectroscopic survey aimed at measuring the timescale of mass accretion in young, pre-main-sequence stars in the spectral type range K0 - M5. Using multi-object spectroscopy with VIMOS at the VLT we identified the fraction of accreting stars in a number of young stellar clusters and associations of ages between 1 - 50 Myr. The fraction of accreting stars decreases from ~60% at 1.5 - 2 Myr to ~2% at 10 Myr. No accreting stars are found after 10 Myr at a sensitivity limit of $10^{-11}$ Msun yr-1. We compared the fraction of stars showing ongoing accretion (f_acc) to the fraction of stars with near-to-mid infrared excess (f_IRAC). In most cases we find f_acc < f_IRAC, i.e., mass accretion appears to cease (or drop below detectable level) earlier than the dust is dissipated in the inner disk. At 5 Myr, 95% of the stellar population has stopped accreting material at a rate of > 10^{-11} Msun yr-1, while ~20% of the stars show near-infrared excess emission. Assuming an exponential decay, we measure a mass accretion timescale (t_acc) of 2.3 Myr, compared to a near-to-mid infrared excess timescale (t_IRAC) of 2.9 Myr. Planet formation, and/or migration, in the inner disk might be a viable mechanism to halt further accretion onto the central star on such a short timescale.

[41]  arXiv:0911.3327 [ps, pdf, other]

Title: Simulating magnetic fields in the Antennae galaxies

Authors: H. Kotarba, S. Karl, T. Naab, P. H. Johansson, K. Dolag, H. Lesch

Comments: 13 pages, 10 figures

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We present self-consistent high-resolution simulations of NGC4038/4039 (the "Antennae galaxies") including star formation, supernova feedback and magnetic fields performed with the N-body/SPH code Gadget, in which hydrodynamics and magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 1 nG to 1 muG. At the time of the best match with the central region of the Antennae system the magnetic field has been amplified by compression and shear flows to an equilibrium field of approximately 10 muG, independent of the initial seed field. This simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of regular magnetic fields between the cores and at the root of the southern tidal arm develop naturally in our simulations. This indicates that the simulations are capable of realistically following the evolution of the magnetic fields in a highly non-linear environment. We also discuss the relevance of the amplification effect for present day magnetic fields in the context of hierarchical structure formation.

[42]  arXiv:0911.3332 [ps, pdf, other]

Title: Quasar Outflow Contribution to AGN Feedback: Observations of QSO SDSS J0838+2955

Authors: Maxwell Moe, Nahum Arav, Manuel A. Bautista, Kirk T. Korista

Comments: 28 pages, 7 figures, 4 tables, published in Astrophysical Journal

Journal-ref: 2009 ApJ 706 525-534

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)

We present a detailed analysis of the Astrophysical Research Consortium 3.5 m telescope spectrum of QSO SDSS J0838+2955. The object shows three broad absorption line (BAL) systems at 22,000, 13,000, and 4900 km s^-1 blueshifted from the systemic redshift of z=2.043. Of particular interest is the lowest velocity system that displays absorption from low-ionization species such as Mg II, Al II, Si II, Si II*, Fe II and Fe II*. Accurate column densities were measured for all transitions in this lowest velocity BAL using an inhomogeneous absorber model. The ratio of column densities of Si II* and Fe II* with respect to their ground states gave an electron number density of log n_e (cm^-3) = 3.75 +/- 0.22 for the outflow. Photoionization modeling with careful regards to chemical abundances and the incident spectral energy distribution predicts an ionization parameter of log U_H = -1.93 +/- 0.21 and a hydrogen column density of log N_H (cm^-2) = 20.80 +/- 0.28. This places the outflow at 3.3+1.5-1.0 kpc from the central AGN. Assuming that the fraction of solid angle subtended by the outflow is 0.2, these values yield a kinetic luminosity of (4.5+3.1-1.8) x 10^45 erg s^-1, which is (1.4+1.1-0.6)% the bolometric luminosity of the QSO itself. Such large kinetic luminosity suggests that QSO outflows are a major contributor to AGN feedback mechanisms.

[43]  arXiv:0911.3348 [ps, pdf, other]

Title: Spitzer-IRS high resolution spectroscopic survey of the 12 micron Seyfert galaxies: II. Results for the Complete Dataset

Authors: Silvia Tommasin (1), Luigi Spinoglio (1), Matthew A. Malkan (2), Giovanni Fazio (3) ((1) IFSI-INAF, Italy, (2) UCLA, USA, (3) CfA, USA)

Comments: Accepted in The Astrophysical Journal Part 1 on November 15, 2009. 58 pages

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We present the Spitzer 10-37um IRS high resolution (R~600) spectroscopic survey of the Seyfert galaxies of the 12 micron Galaxy Sample. The new spectra of 61 galaxies, with those already published, gives us a total of 91 12micron Seyfert galaxies observed, out of 112. We use an improved AGN classification for Seyfert galaxies: instead of the type 1 and 2 classes, we use the spectropolarimetric data to divide them into "AGN 1" and "AGN 2", where AGN 1's include all broad-line objects, including the Seyfert 2's showing hidden broad lines in polarized light, while AGN 2's contains only Seyferts with no detectable broad lines at all. We present various mid-IR observables and we find that these properties characterize the AGN 1's objects as a single family, with strongly AGN-dominated spectra. In contrast, the AGN 2's can be divided in two groups, the first one with properties similar to the AGN 1's and the second similar to the non-Seyfert galaxies, such as LINERs or starburst galaxies. We computed a semianalytical model to estimate the AGN and the starburst contributions to the mid-IR galaxy emission at 19um. We find that AGN 1 have an AGN contribution >73% and AGN 2 >45% of their total emission at 19um. The detection of [NeV] lines is an almost perfect signature of energy production by an AGN. We present mean spectra of the various AGN categories. We derive the first local luminosity functions for the mid-infrared lines and the PAH feature. No statistical difference is found in the space densities for Seyfert 1's and 2's, nor for the new classes of AGN 1's and 2's. The global output of accretion-powered galactic nuclei in the local universe is derived from the correlation between [NeV] line and the nonstellar IR continuum luminosity.

[44]  arXiv:0911.3349 [pdf]

Title: Seeing Science

Authors: Alyssa Goodman

Comments: 4 pages, including 3 figures. To appear in Proceedings of the International Festival of Scientific Visualization, held in Tokyo, Japan, March 2009. Publisher will be Universal Academy Press

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The ability to represent scientific data and concepts visually is becoming increasingly important due to the unprecedented exponential growth of computational power during the present digital age. The data sets and simulations scientists in all fields can now create are literally thousands of times as large as those created just 20 years ago. Historically successful methods for data visualization can, and should, be applied to today's huge data sets, but new approaches, also enabled by technology, are needed as well. Increasingly, "modular craftsmanship" will be applied, as relevant functionality from the graphically and technically best tools for a job are combined as-needed, without low-level programming.

[45]  arXiv:0911.3353 [ps, pdf, other]

Title: 3D stellar atmospheres for stellar structure models and asteroseismology

Authors: F. Kupka

Comments: 10 pages, 4 figures, appears in Memorie della Societa Astronomica Italiana

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Convection is the most important physical process that determines the structure of the envelopes of cool stars. It influences the surface radiation flux and the shape of observed spectral line profiles and is responsible for both generating and damping solar-like oscillations, among others. 3D numerical simulations of stellar surface convection have developed into a powerful tool to model and analyse the physical mechanisms operating at the surface of cool stars. This review discusses the main principles of 3D stellar atmospheres used for such applications. The requirements from stellar structure and evolution theory to use them as boundary conditions are analysed as well as the capabilities of using helio- and asteroseismology to reduce modelling uncertainties and probing the consistency and accuracy of 3D stellar atmospheres as part of this process. Simulations for the solar surface made by different teams are compared and some issues concerning the uncertainties of this modelling approach are discussed.

[46]  arXiv:0911.3360 [ps, pdf, other]

Title: Mapping the Asymmetric Thick Disk I. A Search for Triaxiality

Authors: J.A. Larsen, J.E. Cabanela, R.M. Humphreys, A.P. Haviland

Comments: 36 pages, 8 figures. Accepted by Astronomical Journal

Subjects: Galaxy Astrophysics (astro-ph.GA)

A significant asymmetry in the distribution of faint blue stars in the inner Galaxy, Quadrant 1 (l = 20 to 45 degrees) compared to Quadrant 4 was first reported by Larsen & Humphreys (1996). Parker et al (2003, 2004) greatly expanded the survey to determine its spatial extent and shape and the kinematics of the affected stars. This excess in the star counts was subsequently confirmed by Juric et al. (2008) using SDSS data. Possible explanations for the asymmetry include a merger remnant, a triaxial Thick Disk, and a possible interaction with the bar in the Disk. In this paper we describe our program of wide field photometry to map the asymmetry to fainter magnitudes and therefore larger distances. To search for the signature of triaxiality, we extended our survey to higher Galactic longitudes. We find no evidence for an excess of faint blue stars at l > 55 degrees including the faintest magnitude interval. The asymmetry and star count excess in Quadrant 1 is thus not due to a triaxial Thick Disk.

[47]  arXiv:0911.3361 [ps, pdf, other]

Title: Mass loss from inhomogeneous hot star winds I. Resonance line formation in 2D models

Authors: J.O. Sundqvist, J. Puls, A. Feldmeier

Comments: 14 pages (+2 appendices), 13 (+2) figures, accepted for publication in A&amp;A

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Small-scale clumping in the winds of hot, massive stars is conventionally included in spectral analyses by assuming optically thin clumps, a void inter-clump medium, and a smooth velocity field. To reconcile investigations of different diagnostics within such models, a highly clumped wind with very low mass-loss rates needs to be invoked. Particularly, unsaturated UV resonance lines seem to indicate rates an order of magnitude (or even more) lower than previously accepted values. We investigate resonance line formation in inhomogeneous hot star winds with non-monotonic velocity fields by means of 2D stochastic and pseudo-2D radiation-hydrodynamic wind models. A Monte-Carlo radiative transfer code is presented and used to produce synthetic line spectra. Results: The optically thin clumping limit is only valid for very weak lines. For intermediate strong lines, the velocity spans of the clumps are of central importance. Current hydrodynamical models predict spans that are too large to reproduce observed profiles unless a very low mass-loss rate is invoked. By simulating lower spans in 2D stochastic models, the profile strengths become drastically reduced, and are consistent with higher mass-loss rates. To simultaneously meet the constraints from strong lines, the inter-clump medium must be non-void. A first comparison to the observed PV doublet in the O6 supergiant lam Cep confirms that a stochastic 2D model reproduces observations with a mass-loss rate roughly ten times higher than that derived from the same lines but assuming optically thin clumping. Tentatively this may resolve discrepancies between theoretical predictions, evolutionary constraints, and recent derived mass-loss rates, and suggests a re-investigation of the structure predicted by current hydrodynamical models.

[48]  arXiv:0911.3368 [ps, pdf, other]

Title: The clustering properties of the first galaxies

Authors: M. Stiavelli (STScI), M. Trenti (U. Colorado)

Comments: 11 pages including 4 figures. Originally submitted to ApJL on Sept. 11, 2009. Resubmittted on Nov.17, 2009

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We consider the clustering properties of the first galaxies formed in the Universe. Due to the chemical enrichment of the inter-stellar medium by isolated Population III stars formed in minihalos at redshift z >~ 30, the chronologically first galaxies are composed of metal-poor Population II stars and are highly clustered. Chemically pristine galaxies in halos with mass M ~ 10^8 M_sun may form instead at z<20 in relatively underdense regions of the Universe once self-enrichment by Population III in minihalos is quenched by the build-up of an H_2 photo-dissociating radiative background in the Lyman-Werner bands. We find that these chemically pristine galaxies are essentially uncorrelated so we expect that deep fields with the James Webb Space Telescope will not be seriously affected by cosmic variance for these objects. We predict that 10 <~ z <~ 15 metal-free galaxies have area densities of about 80 per arcmin square and per unit redshift but most of them will be too faint even for JWST. However, the predicted density makes these objects interesting targets for searches behind lensing clusters.

[49]  arXiv:0911.3369 [ps, pdf, other]

Title: The JCMT Nearby Galaxies Legacy Survey III: Comparisons of cold dust, polycyclic aromatic hydrocarbons, molecular gas, and atomic gas in NGC 2403

Authors: G. J. Bendo, C. D. Wilson, B. E. Warren, E. Brinks, H. M. Butner, P. Chanial, D. L. Clements, S. Courteau, J. Irwin, F. P. Israel, J. H. Knapen, J. Leech, H. E. Matthews, S. Muehle, G. Petitpas, S. Serjeant, B. K. Tan, R. P. J. Tilanus, A. Usero, M. Vaccari, P. van der Werf, C. Vlahakis, T. Wiegert, M. Zhu

Comments: Accepted to MNRAS

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We used 3.6, 8.0, 70, 160 micron Spitzer Space Telescope data, James Clerk Maxwell Telescope HARP-B CO J=(3-2) data, National Radio Astronomy Observatory 12 meter telescope CO J=(1-0) data, and Very Large Array HI data to investigate the relations among PAHs, cold (~20 K) dust, molecular gas, and atomic gas within NGC 2403, an SABcd galaxy at a distance of 3.13 Mpc. The dust surface density is mainly a function of the total (atomic and molecular) gas surface density and galactocentric radius. The gas-to-dust ratio monotonically increases with radius, varying from ~100 in the nucleus to ~400 at 5.5 kpc. The slope of the gas-to-dust ratio is close to that of the oxygen abundance, suggesting that metallicity strongly affects the gas-to-dust ratio within this galaxy. The exponential scale length of the radial profile for the CO J=(3-2) emission is statistically identical to the scale length for the stellar continuum-subtracted 8 micron (PAH 8 micron) emission. However, CO J=(3-2) and PAH 8 micron surface brightnesses appear uncorrelated when examining sub-kpc sized regions.

[50]  arXiv:0911.3383 [pdf]

Title: A Vigorous Explorer Program

Authors: Martin Elvis (SAO), Matthew Beasley (U. CO, Boulder), Roger Brissenden (SAO), Supriya Chakrabarti (Boston U.), Michael Cherry (Louisiana State U.), Mark Devlin (U. Penn), Jerry Edelstein (UC Berkeley), Peter Eisenhardt (JPL/Caltech), Paul Feldman (Johns Hopkins U.), Holland Ford (Johns Hopkins U), Neil Gehrels (NASA/GSFC), Leon Golub (SAO), Herman Marshall (MIT), Christopher Martin (Caltech), John Mather (NASA/GSFC), Stephan McCandliss (Johns Hopkins U.), Mark McConnell (U. New Hampshire), Jonathan McDowell (SAO), David Meier (JPL/Caltech), Robyn Millan (Dartmouth), John Mitchell (NASA/GSFC), Warren Moos (Johns Hopkins U.), Steven S. Murray (SAO), John Nousek (Penn State U), William Oegerle (NASA/GSFC), Brian Ramsey (NASA/MSFC), James Green (U.CO, Boulder), Jonathan Grindlay (Harvard), Philip Kaaret (U.Iowa), et al. (21 additional authors not shown)

Comments: 18 pages, no figures. An Activities/Program White Paper submitted to the Astro2010 NAS/NRC Decadal Review of Astronomy and Astrophysics

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Explorers have made breakthroughs in many fields of astrophysics. The science from both these missions contributed to three Nobel Prizes - Giacconi (2002), Mather, and Smoot (2006). Explorers have: marked the definitive beginning of precision cosmology, discovered that short gamma-ray bursts are caused by compact star mergers and have measured metalicity to redshifts z>6. NASA Explorers do cutting-edge science that cannot be done by facility-class instruments. The Explorer program provides a rapid response to changing science and technology, to enable cutting-edge science at moderate cost. Explorers also enable innovation, and engage & train scientists, managers and engineers, adding human capital to NASA and the nation. The astrophysics Explorer launch rate now being achieved is 1 per 3 years, and budget projections are in the $150M/year range for the next five years. A newly Vigorous Explorer Program should be created to: 1. Reach the long-stated goal of annual astrophysics launches; 2. Find additional launch options for Explorers and actively encourage cost savings in launchers and spacecraft, such as new commercial vehicles and innovative partnerships. 3. Mitigate risk via stronger technical development and sub-orbital programs, and through longer, more thorough, Phase A programs, potentially reducing the need for a 30% contingency; 4. Strive to protect the funding for missions that have reached Phase B, to prevent significant launch slips and cancellations, with a goal of 4 to 5 years from Phase B to launch; 5. Review the project management procedures and requirements to seek cost reductions, including the risk management strategy and the review and reporting process; 6. Review and possibly modify the cost caps for all Explorer classes to optimize scientific returns per dollar. [ABRIDGED]

[51]  arXiv:0911.3390 [ps, pdf, other]

Title: Do we expect to find the Super-Earths close to the gas giants?

Authors: E. Podlewska (CASA* and Institute of Physics, University of Szczecin, Poland)

Comments: 7 pages, to appear in the proceedings of the conference "Extra-solar Planets in Multi-body Systems: Theory and Observations"; eds. K. Gozdziewski, A. Niedzielski and J. Schneider, EAS Publication Series

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We have investigated the evolution of a pair of interacting planets embedded in a gaseous disc, considering the possibility of the resonant capture of a Super-Earth by a Jupiter mass gas giant. First, we have examined the situation where the Super-Earth is on the internal orbit and the gas giant on the external one. It has been found that the terrestrial planet is scattered from the disc or the gas giant captures the Super-Earth into an interior 3:2 or 4:3 mean-motion resonance. The stability of the latter configurations depends on the initial planet positions and on eccentricity evolution. The behaviour of the system is different if the Super-Earth is the external planet. We have found that instead of being captured in the mean-motion resonance, the terrestrial planet is trapped at the outer edge of the gap opened by the gas giant. This effect prevents the occurrence of the first order mean-motion commensurability. These results are particularly interesting in light of recent exoplanet discoveries and provide predictions of what will become observationally testable in the near future.

Cross-lists for Wed, 18 Nov 09

[52]  arXiv:0911.2502 (cross-list from math.PR) [ps, pdf, other]

Title: Ergodicity and Gaussianity for Spherical Random Fields

Authors: Domenico Marinucci (DIPMAT), Giovanni Peccati (MODAL'X)

Comments: 25 pages; PACS : 02.50-r, 98.70-Vc, 98.80-k

Subjects: Probability (math.PR); Cosmology and Extragalactic Astrophysics (astro-ph.CO); Statistics (math.ST)

We investigate the relationship between ergodicity and asymptotic Gaussianity of isotropic spherical random fields, in the high-resolution (or high-frequency) limit. In particular, our results suggest that under a wide variety of circumstances the two conditions are equivalent, i.e. the sample angular power spectrum may converge to the population value if and only if the underlying field is asymptotically Gaussian, in the high frequency sense. These findings may shed some light on the role of Cosmic Variance in Cosmic Microwave Background (CMB) radiation data analysis.

[53]  arXiv:0911.2912 (cross-list from physics.plasm-ph) [ps, pdf, other]

Title: Wave instabilities of a collisionless plasma in the fluid approximation

Authors: N. S. Dzhalilov (1, 2, and 3), V. D. Kuznetsov (1), J. Staude (3) ((1) Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk/Moscow, Russia, (2) Shamakhy Astrophysical Observatory, Baku, Azerbaidjan, (3) Astrophysikalisches Institut Potsdam, Germany)

Comments: 12 pages, 11 figures

Subjects: Plasma Physics (physics.plasm-ph); Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

In this paper we study the wave properties and instabilities in a magnetized, anisotropic, collisionless, rarefied hot plasma in the fluid approximation. We use the 16-moments set of the transport equations obtained from the Vlasov kinetic equations by the fast gyromotion ordering technique. These equations are first order equations and they differ from the usual CGL- MHD fluid model equations by including two anisotropic heat flux evolution equations. The general dispersion relation for the linear compressible wave modes is derived. The included heat fluxes invalidate the double polytropic CGL laws. Besides the classic incompressible fire hose modes there appear four types of compressible wave modes: two fast and slow mirror modes - strongly modified compared to the CGL model - and two thermal modes. In the presence of initial heat fluxes along the magnetic field the wave properties become different for the waves running forward and backward with respect to the magnetic field. Instability develops at such positions where two and more wave modes are coupled resonantly. It is shown that the well known discrepancies between the results of the CGL-MHD fluid model and the kinetic theory are removed: i) The mirror slow mode instability criterion is now the same as that in the kinetic theory. ii) Similarly, in kinetic studies there appear two kinds of fire hose instabilities - incompressible and compressible ones. These two instabilities can arise for the same plasma parameters, and the instability of the new compressible oblique fire hose modes can become dominant. The results can be applied to the theory of solar and stellar coronal and wind models.

[54]  arXiv:0911.2946 (cross-list from gr-qc) [ps, pdf, other]

Title: Non-minimal coupling of photons and axions

Authors: Alexander B. Balakin, Wei-Tou Ni

Comments: 31 pages, 2 Tables

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We establish a new self-consistent system of equations accounting for a non-minimal interaction of gravitational, electromagnetic and axion fields. The procedure is based on a non-minimal extension of the standard Einstein-Maxwell-axion action. General properties of a ten-parameter family of non-minimal linear models are discussed. We apply this theory to the models with pp-wave symmetry, and consider propagation of electromagnetic waves non-minimally coupled to the gravitational and axion fields. We focus on exact solutions of electrodynamic equations, which describe quasi-minimal and non-minimal optical activity induced by axion field. We also discuss empirical constraints on coupling parameters from astrophysical birefringence and polarization rotation observations.

[55]  arXiv:0911.2997 (cross-list from gr-qc) [ps, pdf, other]

Title: Dynamics driven by the Trace Anomaly in FLRW Universes

Authors: J.F. Koksma (Utrecht University)

Comments: Conference proceedings of the "Invisible Universe Conference" in Paris (2009)

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

By means of a semiclassical analysis we show that the trace anomaly does not affect the cosmological constant. We calculate the evolution of the Hubble parameter in quasi de Sitter spacetime, where the Hubble parameter varies slowly in time, and in FLRW spacetimes. We show dynamically that a Universe consisting of matter with a constant equation of state, a cosmological constant and the quantum trace anomaly evolves either to the classical de Sitter attractor or to a quantum trace anomaly driven one. There is no dynamical effect that influences the effective value of the cosmological constant.

[56]  arXiv:0911.3041 (cross-list from nucl-ex) [ps, pdf, other]

Title: Semi-empirical calculation of quenching factors for ions in scintillators

Authors: V.I. Tretyak

Comments: 32 pages; accepted in Astropart. Phys

Subjects: Nuclear Experiment (nucl-ex); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Semi-empirical method of calculation of quenching factors for scintillators is described. It is based on classical Birks formula with the total stopping powers for electrons and ions which are calculated with the ESTAR and SRIM codes, respectively. Method has only one fitting parameter (the Birks factor kB) which can have different values for the same material in different conditions of measurements and data treatment. A hypothesis is used that, once the kB value is obtained by fitting data for particles of one kind and in some energy region (e.g. for a few MeV alpha particles from internal contamination of a detector), it can be applied to calculate quenching factors for particles of another kind and for another energies (e.g. for low energy nuclear recoils) if all data are measured in the same experimental conditions and are treated in the same way. Applicability of the method is demonstrated on many examples including materials with different mechanisms of scintillation: organic scintillators (solid C8H8, and liquid C16H18, C9H12); crystal scintillators (pure CdWO4, PbWO4, ZnWO4, CaWO4, CeF3, and doped CaF2(Eu), CsI(Tl), CsI(Na), NaI(Tl)); liquid noble gases (LXe). Estimations of quenching factors for nuclear recoils are also given for some scintillators where experimental data are absent (CdWO4, PbWO4, CeF3, Bi4Ge3O12, LiF, ZnSe).

[57]  arXiv:0911.3089 (cross-list from gr-qc) [ps, pdf, other]

Title: Quintessence with quadratic coupling to dark matter

Authors: Christian G. Boehmer, Gabriela Caldera-Cabral, Nyein Chan, Ruth Lazkoz, Roy Maartens

Comments: 11 pages, 8 figures, revtex

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We introduce a new form of coupling between dark energy and dark matter that is quadratic in their energy densities. Then we investigate the background dynamics when dark energy is in the form of exponential quintessence. The three types of quadratic coupling all admit late-time accelerating critical points, but these are not scaling solutions. We also show that two types of coupling allow for a suitable matter era at early times and acceleration at late times, while the third type of coupling does not admit a suitable matter era.

[58]  arXiv:0911.3118 (cross-list from hep-th) [ps, pdf, other]

Title: Non-topological Cycloops

Authors: M. Lake, S. Thomas, J. Ward

Comments: 28 pages, 4 figures

Subjects: High Energy Physics - Theory (hep-th); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We propose a mechanism for the creation of cosmic string loops with dynamically stabilised windings in the internal space. Assuming a velocity correlations regime in the post-inflationary epoch, such windings are seen to arise naturally in string networks prior to loop formation. The angular momentum of the string in the compact space may then be sufficient to ensure that the windings remain stable after the loop chops off from the network, even if the internal manifold is simply connected. For concreteness we embed our model in the Klebanov-Strassler geometry, which provides a natural mechanism for brane inflation, as well a being one of the best understood compactification schemes in type IIB string theory. We see that the interaction of angular momentum with the string tension causes the loop to oscillate between phases of expansion and contraction. This, in principle, should give rise to a distinct gravitational wave signature, the future detection of which could provide indirect evidence for the existence of extra dimensions.

Replacements for Wed, 18 Nov 09

[59]  arXiv:0804.1854 (replaced) [ps, pdf, other]

Title: Self-interacting fermionic dark matter with axis of locality

Authors: D. V. Ahluwalia, Cheng-Yang Lee, D. Schritt (University of Canterbury, New Zealand)

Comments: Completely revised

Subjects: High Energy Physics - Theory (hep-th); Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); Mathematical Physics (math-ph)

[60]  arXiv:0810.2827 (replaced) [ps, pdf, other]

Title: Influence of Dark Matter on Light Propagation in Solar System

Authors: Hideyoshi Arakida

Comments: 18 pages, 4 figures, accepted for publication in Advances in Space Research

Subjects: Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc)

[61]  arXiv:0810.5076 (replaced) [ps, pdf, other]

Title: Phantom without phantom or how the PT symmetry saves us from the Big Rip

Authors: A.A. Andrianov, F. Cannata, A.Y. Kamenshchik, D. Regoli

Comments: revised and enlarged version, to be published in Int. J. Mod. Phys. D, the title is changed

Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics - Theory (hep-th)

[62]  arXiv:0901.4380 (replaced) [ps, pdf, other]

Title: Unconventional rotational responses of hadronic superfluids in a neutron star caused by strong entrainment and a $\Sigma^-$ hyperon gap

Authors: Egor Babaev

Comments: replaced with the version in print in Phys. Rev. Lett.(various improvements of presentation, no changes in the results)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Superconductivity (cond-mat.supr-con)

[63]  arXiv:0903.4458 (replaced) [ps, pdf, other]

Title: Are symmetric tidal streams possible with long-range dark-matter forces?

Authors: Michael Kesden

Comments: 11 pages, 4 figures, final PRD version

Journal-ref: Phys.Rev.D80:083530,2009

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)

[64]  arXiv:0905.3008 (replaced) [ps, pdf, other]

Title: Secular increase of the Astronomical Unit: a possible explanation in terms of the total angular momentum conservation law

Authors: Takaho Miura, Hideyoshi Arakida, Masumi Kasai, Shuichi Kuramata

Comments: 4 pages, accepted for publication in PASJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[65]  arXiv:0906.2193 (replaced) [pdf]

Title: Detecting planetary geochemical cycles on exoplanets: Atmospheric signatures and the case of SO2

Authors: L. Kaltenegger, D. Sasselov

Comments: 9 pages, 6 figures, ApJ accepted - detailed discussion added

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

[66]  arXiv:0906.3347 (replaced) [ps, pdf, other]

Title: The Last Eight-Billion Years of Intergalactic CIV Evolution

Authors: Kathy L. Cooksey (1), Christopher Thom (2), J. Xavier Prochaska (1,3), Hsiao-Wen Chen (2) ((1) UC Santa Cruz; (2) U Chicago; (3) UCO/Lick Observatory)

Comments: 61 pages; accepted by ApJ; includes changes based on referee report

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[67]  arXiv:0906.5127 (replaced) [ps, pdf, other]

Title: Stochastic model of optical variability of BL Lacertae

Authors: D. A. Blinov, V. A. Hagen-Thorn

Comments: 4 pages, 10 figures, published by Astronomy and Astrophysics; v2: typos corrected

Journal-ref: A&A 503, 103-106 (2009)

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[68]  arXiv:0908.0224 (replaced) [ps, pdf, other]

Title: The X-ray Binary Analogy to the First AGN QPO

Authors: M. Middleton, C. Done

Comments: 9 pages, 12 figures, to be published in MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[69]  arXiv:0908.3678 (replaced) [ps, pdf, other]

Title: Modeling the Very Small-Scale Clustering of Luminous Red Galaxies

Authors: Douglas F. Watson, Andreas A. Berlind, Cameron K. McBride, Morad Masjedi

Comments: 6 pages, 2 figures, Accepted to ApJ

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[70]  arXiv:0909.0011 (replaced) [ps, pdf, other]

Title: Magnetohydrodynamic Simulations of Gamma-Ray Burst Jets: Beyond the Progenitor Star

Authors: Alexander Tchekhovskoy (1), Ramesh Narayan (1), Jonathan C. McKinney (2) ((1) Harvard-CfA, (2) Department of Physics and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University)

Comments: 5 pages (emulateapj), 3 figures. Submitted to ApJL. Changes in v.2: added analytic solution (eq. 5) that reproduces the numerical results

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Galaxy Astrophysics (astro-ph.GA)

[71]  arXiv:0909.0266 (replaced) [ps, pdf, other]

Title: Relic density and future colliders: inverse problem(s)

Authors: A. Arbey, F. Mahmoudi

Comments: 8 pages, 5 figures, contribution to the proceedings of the conference "Invisible Universe", Paris, June 29 - July 3, 2009, France

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

[72]  arXiv:0909.3776 (replaced) [ps, pdf, other]

Title: Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction

Authors: G.W. Pratt (CEA Saclay and MPE), M. Arnaud, R. Piffaretti, H. Boehringer, T.J. Ponman, J.H. Croston, G.M. Voit, S. Borgani, R.G. Bower

Comments: 14 pages, 9 figures, A&amp;A, in press. Final version corrects Eqn. 3 and columns 5-8 in Table 1 and has additional minor text clarifications

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[73]  arXiv:0910.1615 (replaced) [ps, pdf, other]

Title: The early history of protostellar disks, outflows, and binary stars

Authors: Dennis F. Duffin, Ralph E. Pudritz

Comments: 12 pages, 3 figures, accepted by ApJ Letters; corrected text to match journal version; movies can be found at this http URL

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

[74]  arXiv:0910.1870 (replaced) [ps, pdf, other]

Title: Gravitino Dark Matter

Authors: Wilfried Buchmuller

Comments: 10 pages, 6 figures, Talk at SUSY09, Boston

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

[75]  arXiv:0910.2418 (replaced) [ps, pdf, other]

Title: X-ray reflection in a sample of X-ray bright Ultraluminous X-ray sources

Authors: M. D. Caballero-Garcia (1), A. C. Fabian (1) ((1) IoA, U. of Cambridge)

Comments: Accepted for publication in MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[76]  arXiv:0910.5372 (replaced) [ps, pdf, other]

Title: Exploring the Luminosity Evolution and Stellar Mass Assembly of 2SLAQ Luminous Red Galaxies Between Redshift 0.4 and 0.8

Authors: Manda Banerji (IoA, Cambridge/UCL), Ignacio Ferreras (MSSL-UCL), Filipe B. Abdalla (UCL), Paul Hewett (IoA, Cambridge), Ofer Lahav (UCL)

Comments: 17 pages, 15 figures, Accepted for publication in MNRAS, Some changes to match accepted version

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[77]  arXiv:0911.0474 (replaced) [ps, pdf, other]

Title: The X-ray Energy Dependence of the Relation between Optical and X-ray Emission in Quasars

Authors: M. Young, M. Elvis, G. Risaliti

Comments: 27 pages preprint style, 10 figures. New material added to section 4.3 (Fig. 11) regarding hard X-ray bolometric corrections. Accepted for publication in Astrophysical Journal

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[78]  arXiv:0911.1356 (replaced) [ps, pdf, other]

Title: The evolution of z=7-8 galaxies from IRAC observations of the deep/wide-area WFC3/IR ERS and ultradeep WFC3/IR HUDF

Authors: I. Labbe, V. Gonzalez, R. J. Bouwens, G. D. Illingworth, M. Franx, M. Trenti, P. A. Oesch, P. G. van Dokkum, M. Stiavelli, C. M. Carollo, M. Kriek, D. Magee

Comments: 6 pages, 4 figures, 1 table, emulateapj, submitted to ApJL: minor changes to match submitted version, added table, added references

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

[79]  arXiv:0911.1659 (replaced) [ps, pdf, other]

Title: XMM-Newton and Swift observations prove GRB 090709A to be a distant, standard, long GRB

Authors: A. De Luca, P. Esposito, G. L. Israel, D. Götz, G. Novara, A. Tiengo, S. Mereghetti

Comments: 7 pages, 7 figures, 2 tables; accepted for publication in MNRAS. (V2: a typo corrected in the author list.)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[80]  arXiv:0911.3111 (replaced) [ps, pdf, other]

Title: The 400d Galaxy Cluster Survey Weak Lensing Programme: I: MMT/Megacam Analysis of CL0030+2618 at z=0.50

Authors: Holger Israel (1), Thomas Erben (1), Thomas H. Reiprich (1), Alexey Vikhlinin (2), Hendrik Hildebrandt (3), Daniel S. Hudson (1), Brian A. McLeod (2), Craig L. Sarazin (4), Peter Schneider (1), Yu-Ying Zhang (1) ((1) Argelander-Institut für Astronomie, Univ. Bonn, Germany, (2) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA, (3) Leiden Observatory, Leiden University, Leiden, The Netherlands, (4) Department of Astronomy, University of Virginia, Charlottesville, VA, USA)

Comments: 32 pages, 24 figures, submitted to Astronomy &amp; Astrophysics; fixed some LaTeX issues, now 30 pages

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

• New submissions
• Cross-lists
• Replacements