Astrophysics
New submissions
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New submissions for Fri, 20 Nov 09
- [1] arXiv:0911.3651 [ps, pdf, other]
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Title: The age of cataclysmic variables: a kinematical studyComments: 32 pages, 11 figures and 4 tables, accepted for publication in New AstronomySubjects: Galaxy Astrophysics (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Using available astrometric and radial velocity data, the space velocities of cataclysmic variables (CVs) with respect to Sun were computed and kinematical properties of various sub-groups of CVs were investigated. Although observational errors of systemic velocities ($\gamma$) are high, propagated errors are usually less than computed dispersions. According to the analysis of propagated uncertainties on the computed space velocities, available sample is refined by removing the systems with the largest propagated uncertainties so that the reliability of the space velocity dispersions was improved. Having a dispersion of $51\pm7$ km s$^{-1}$ for the space velocities, CVs in the current refined sample (159 systems) are found to have $5\pm1$ Gyr mean kinematical age. After removing magnetic systems from the sample, it is found that non-magnetic CVs (134 systems) have a mean kinematical age of $4\pm1$ Gyr. According to $5\pm1$ and $4\pm1$ Gyr kinematical ages implied by $52\pm8$ and $45\pm7$ km s$^{-1}$ dispersions for non-magnetic systems below and above the period gap, CVs below the period gap are older than systems above the gap, which is a result in agreement with the standard evolution theory of CVs. Age difference between the systems below and above the gap is smaller than that expected from the standard theory, indicating a similarity of the angular momentum loss time scales in systems with low-mass and high-mass secondary stars. Assuming an isotropic distribution, $\gamma$ velocity dispersions of non-magnetic CVs below and above the period gap are calculated $\sigma_\gamma=30\pm5$ km s$^{-1}$ and $\sigma_\gamma=26\pm4$ km s$^{-1}$.
- [2] arXiv:0911.3652 [ps, pdf, other]
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Title: Characterizing Magnetohydrodynamic Turbulence in the Small Magellanic CloudSubjects: Galaxy Astrophysics (astro-ph.GA)
We investigate the nature and spatial variations of turbulence in the Small Magellanic Cloud (SMC) by applying several statistical methods on the neutral hydrogen (HI) column density image of the SMC and a database of isothermal numerical simulations. By using the 3rd and 4th statistical moments we derive the spatial distribution of the sonic Mach number (M_s) across the SMC. We find that about 90% of the HI in the SMC is subsonic or transonic. However, edges of the SMC `bar' have M_s=4 and may be tracing shearing or turbulent flows. Using numerical simulations we also investigate how the slope of the spatial power spectrum depends on both sonic and Alfven Mach numbers. This allows us to gauge the Alfven Mach number of the SMC and conclude that its gas pressure dominates over the magnetic pressure. The super-Alfvenic nature of the HI gas in the SMC is also highlighted by the bispectrum, a three-point correlation function which characterizes the level of non-Gaussianity in wave modes. We find that the bispectrum of the SMC HI column density displays similar large-scale correlations as numerical simulations, however it has localized enhancements of correlations. In addition, we find a break in correlations at a scale of 160 pc. This may be caused by numerous expanding shells of a similar size.
- [3] arXiv:0911.3653 [pdf, other]
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Title: Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R CrAComments: 17 pages; 15 figures; Accepted by A&ASubjects: Solar and Stellar Astrophysics (astro-ph.SR)
Models predict that in the innermost AU of the disk around Herbig Ae/Be star, the dust disk forms a "puffed-up" inner rim, which should result in a strongly asymmetric brightness distribution for disks seen under intermediate inclination. Using the VLTI/AMBER long-baseline interferometer, we obtained 24 near-infrared (H- and K-band) spectro-interferometric observations on the Herbig Ae star R CrA. In the derived visibility function, we detect the signatures of an extended (25 mas) and a compact component (5.8 mas), with the compact component contributing about 2/3 of the total flux. The brightness distribution is highly asymmetric, as indicated by the strong closure phases (up to 40 deg) and the detected position angle dependence of the visibilities and closure phases. To interpret these asymmetries, we employ geometric as well as physical models, including a binary model, a skewed ring model, and a puffed-up inner rim model with a vertical or curved rim shape. Our curved puffed-up rim model can reasonably well reproduce the interferometric observables and the SED simultaneously and suggests a luminosity of 29 L_sun and the presence of relatively large (> 1.2 micron) Silicate dust grains. Perpendicular to the disk, two bow shock-like structures appear in the associated reflection nebula NGC 6729, suggesting that the resolved sub-AU size disk is the driving engine of a large-scale outflow. Detecting, for the first time, strong non-localized asymmetries in the inner regions of a Herbig Ae disk, our study supports the existence of a puffed-up inner rim in YSO disks.
- [4] arXiv:0911.3654 [ps, pdf, other]
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Title: Local Group Dwarf Elliptical Galaxies: II. Stellar Kinematics to Large Radii in NGC 147 and NGC 185Comments: 16 pages, 7 figures. submitted to AJ, minor revisions made in response to refereeSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We present kinematic and metallicity profiles for the M31 dwarf elliptical (dE) satellite galaxies NGC 147 and NGC 185. The profiles represent the most extensive spectroscopic radial coverage for any dE galaxy, extending to a projected distance of eight half-light radii (8 r_eff = 14'). We achieve this coverage via Keck/DEIMOS multislit spectroscopic observations of 520 and 442 member red giant branch stars in NGC 147 and NGC 185, respectively. Contrary to previous studies, we find that both dEs have significant internal rotation. We measure a maximum rotational velocity of 17+/-2 km/s for NGC 147 and 15+/-5 km/s for NGC 185. The velocity dispersions decrease gently with radius with an average dispersion of 16+/-1 km/s for NGC 147 and 24+/-1 km/s for NGC 185. Both dEs have internal metallicity dispersions of 0.5 dex, but show no evidence for a radial metallicity gradient. We construct two-integral axisymmetric dynamical models and find that the observed kinematical profiles cannot be explained without modest amounts of non-baryonic dark matter. We measure central mass-to-light ratios of ML_V = 4.2+/-0.6 and ML_V = 4.6+/-0.6 for NGC 147 and NGC 185, respectively. Both dE galaxies are consistent with being primarily flattened by their rotational motions, although some anisotropic velocity dispersion is needed to fully explain their observed shapes. The velocity profiles of all three Local Group dEs (NGC 147, NGC 185 and NGC 205) suggest that rotation is more prevalent in the dE galaxy class than previously assumed, but is often manifest only at several times the effective radius. Since all dEs outside the Local Group have been probed to only inside the effective radius, this opens the door for formation mechanisms in which dEs are transformed or stripped versions of gas-rich rotating progenitor galaxies.
- [5] arXiv:0911.3657 [ps, pdf, other]
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Title: Magnetic field evolution of white dwarfs in strongly interacting binary star systemsComments: 14 pages, 7 figures. Accepted for publication in MNRASSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
The surface magnetic field strength of white dwarfs is observed to vary from very little to around 10^9 G. Here we examine the proposal that the strongest fields are generated by dynamo action during the common envelope phase of strongly interacting stars that leads to binary systems containing at least one white dwarf. The resulting magnetic field depends strongly on the electrical conductivity of the white dwarf, the lifetime of the convective envelope and the variability of the magnetic dynamo. We assess the various energy sources available and estimate necessary lifetimes of the common envelope. In the case of a dynamo that leads a randomly oriented magnetic field we find that the induced field is confined to a thin boundary layer at the surface of the white dwarf. This then decays away rapidly upon dispersal of the common envelope. The residual field is typically less than 10^-8 times the strength of the external field. Only in the case where there is some preferential direction to the dynamo-generated field can an induced field, that avoids rapid decay, be produced. We show that a surface field of magnitude a few per cent of the external field may be produced after a few Myr. In this case the residual field strength is roughly proportional to the lifetime of the dynamo activity.
- [6] arXiv:0911.3658 [ps, pdf, other]
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Title: Screening and Antiscreening of the MOND field in Perturbed Spherical SystemsComments: 7 pages, 6 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
In the context of Modified Newtonian Dynamics (MOND), we study how perturbation of a spherically symmetric system would affect the gravitational field. In particular, we study systems of perturbed and unperturbed spherical shells. For a single perturbed shell, we show that the field inside the shell is much smaller than what would be expected from a naive scaling formula. The strength of the perturbation field within the shell is screened by the spherically symmetric component of the mass, and is reduced as the spherically symmetric component is increased. For a two-shell system, we again show that the perturbed field is screened by the shells, no matter which shell's mass distribution is perturbed. The field within the inner shell is most suppressed when the inner and outer shells coincide. However, for a very light inner shell, the perturbation to the field can be enhanced. The enhancement is typically larger for smaller inner shells, and the perturbed field can be amplified by almost a factor of 2. The relevance to the effect of external fields on galaxy dynamics is discussed.
- [7] arXiv:0911.3659 [ps, pdf, other]
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Title: Derivation of a Relation for the Steepening of TeV Selected Blazar Gamma-ray Spectra with Energy and RedshiftComments: 10 pages, 2 eps figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
We derive a relation for the steepening of blazar gamma-ray spectra between the multi-GeV Fermi energy range and the TeV energy range observed by atmospheric Cerenkov telescopes. The change in spectral index is produced by two effects: (1) an intrinsic steepening, independent of redshift, owing to the properties of emission and absorption in the source, and (2) a redshift-dependent steepening produced by intergalactic pair production interactions of blazar gamma-rays with low energy photons of the intergalactic background light (IBL). Given this relation, with good enough data on the mean gamma-ray SED of TeV selected BL Lacs, the redshift evolution of the IBL can, in principle, be determined independently of stellar evolution models. We apply our relation to the results of new Fermi observations of TeV selected blazars.
- [8] arXiv:0911.3662 [ps, pdf, other]
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Title: Brown dwarfs forming in discs: where to look for them?Comments: To appear in the proceedings of the conference "New technologies for probing the diversity of brown dwarfs and exoplanets", Shanghai 2009Subjects: Galaxy Astrophysics (astro-ph.GA)
A large fraction of the observed brown dwarfs may form by gravitational fragmentation of unstable discs. This model reproduces the brown dwarf desert, and provides an explanation the existence of planetary-mass objects and for the binary properties of low-mass objects. We have performed an ensemble of radiative hydrodynamic simulations and determined the statistical properties of the low-mass objects produced by gravitational fragmentation of discs. We suggest that there is a population of brown dwarfs loosely bound on wide orbits (100-5000 AU) around Sun-like stars that surveys of brown dwarf companions should target. Our simulations also indicate that planetary-mass companions to Sun-like stars are unlikely to form by disc fragmentation.
- [9] arXiv:0911.3665 [ps, pdf, other]
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Title: Slow Diffusive Gravitational Instability Before DecouplingAuthors: Todd A. ThompsonComments: 6 pages, 1 figure, emulateapj, comments welcomeSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Radiative diffusion damps acoustic modes at large comoving wavenumber (k) before decoupling (``Silk damping''). In a simple WKB analysis, neglecting moments of the temperature distribution beyond the quadrupole, damping appears in the acoustic mode as a term of order ik^2/(taudot) where taudot is the scattering rate per unit conformal time. Although the Jeans instability is stabilized on scales smaller than the adiabatic Jeans length, I show that the medium is linearly unstable to first order in (1/taudot) to a slow diffusive mode. At large comoving wavenumber, the characteristic growth rate becomes independent of spatial scale and constant: (t_{KH}a)^-1 ~ (128 pi G/9 kappa_T c)(rho_m/rho_b), where "a" is the scale factor, rho_m and rho_b are the matter and baryon energy density, respectively, and kappa_T is the Thomson opacity. This is the characteristic timescale for a fluid parcel to radiate away its thermal energy content at the Eddington limit, analogous to the Kelvin-Helmholz (KH) time for a massive star or the Salpeter time for black hole growth. Although this mode grows at all times prior to decoupling and on scales smaller than the horizon, the growth time is long, about 100 times the age of the universe at decoupling. Thus, it modifies the density and temperature perturbations on small scales only at the percent level. The physics of this mode is already accounted for in the popular codes CMBFAST and CAMB, but is typically neglected in analytic studies of the growth of primordial perturbations. This work clarifies the physics of this instability in the epoch before decoupling, and emphasizes that the universe is formally unstable on scales below the horizon, even in the limit of large taudot. Analogous instabilities at yet earlier epochs are also mentioned. (Abridged)
- [10] arXiv:0911.3666 [ps, pdf, other]
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Title: Revealing an Energetic Galaxy-Wide Outflow in a z~2 Ultraluminous Infrared GalaxyComments: 6 pages, 3 figures, to appear in Proceedings of "Accretion and Ejection in AGN: A Global View", Lake Como, Italy, June 22-26, 2009, ASP conference series. Based on arXiv:0911.0014 which is now MNRAS, in pressSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Leading models of galaxy formation require large-scale energetic outflows to regulate the growth of distant galaxies and their central black holes. However, current observational support for this hypothesis at high redshift is mostly limited to rare z>2 radio galaxies. Here we present Gemini-North NIFS Intregral Field Unit (IFU) observations of the [O III]5007 emission from a z~2 ultraluminous infrared galaxy (ULIRG; L_IR>10^12 L_sol) with an optically identified Active Galactic Nucleus (AGN). The spatial extent (~4-8 kpc) of the high velocity and broad [O III] emission are consistent with that found in z>2 radio galaxies, indicating the presence of a large-scale energetic outflow in a galaxy population potentially orders of magnitude more common than distant radio galaxies. The low radio luminosity of this system indicates that radio-bright jets are unlikely to be responsible for driving the outflow. However, the estimated energy input required to produce the large-scale outflow signatures (of order ~10^59 ergs over ~30 Myrs) could be delivered by a wind radiatively driven by the AGN and/or supernovae winds from intense star formation. The energy injection required to drive the outflow is comparable to the estimated binding energy of the galaxy spheroid, suggesting that it can have a significant impact on the evolution of the galaxy. We argue that the outflow observed in this system is likely to be comparatively typical of the high-redshift ULIRG population and discuss the implications of these observations for galaxy formation models.
- [11] arXiv:0911.3667 [ps, pdf, other]
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Title: Dissecting the Lyman Alpha Emission Halo of LAB1Authors: A. Weijmans (1,2), R.G. Bower (3), J.E. Geach (3), A.M. Swinbank (3), R.J. Wilman (4), P.T. de Zeeuw (5,1), S.L. Morris (3) ((1) Sterrewacht Leiden, (2) Dunlap Institute, (3) Durham, (4) Swinburne, (5) ESO)Comments: 9 pages, 5 figures, accepted for publication in MNRASSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We report observations of Lyman Alpha Blob 1 (LAB1) in the SSA 22 protocluster region (z=3.09) with the integral-field spectrograph SAURON. We increased the signal-to-noise in the spectra by more than a factor three compared to our previous observations. This allows us to probe the structure of the LAB system in detail, examining its structure in the spatial and wavelength dimensions. We find that the emission from the system comes largely from five distinct blobs. Two of the emission regions are associated with Lyman Break Galaxies, while a third appears to be associated with a heavily obscured submillimeter galaxy. The fourth and fifth components do not appear to be associated with any galaxy despite the deep imaging that is available in this field. If we interpret wavelength shifts in the line centroid as velocity structure in the underlying gas, many of these emission systems show evidence of velocity shear. It remains difficult to distinguish between an underlying rotation of the gas and an outflow driven by the central object. We have examined all of the line profiles for evidence of strong absorption features. While several systems are better fitted by the inclusion of a weak absorption component, we do not see evidence for a large-scale coherent absorption feature such as that seen in LAB2.
- [12] arXiv:0911.3689 [ps, pdf, other]
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Title: An Evaluation of the Excitation Class Parameter for the Central Stars of Planetary NebulaeComments: 14 pages, 18 figure. This peer reviewed paper has been accepted for publication in PASASubjects: Solar and Stellar Astrophysics (astro-ph.SR)
The three main methods currently in use for estimating the excitation class of planetary nebulae (PNe) central stars are compared and evaluated using 586 newly discovered and previously known PNe in the Large Magellanic Cloud (LMC). In order to achieve this we ran a series of evaluation tests using line ratios derived from de-reddened, flux calibrated spectra. Pronounced differences between the methods are exposed. Diagrams were created by comparing excitation classes with H-beta line fluxes. The best methods are then compared to published temperatures using the Zanstra method and assessed for their ability to reflect central star effective temperatures and evolution. As a result we call for a clarification of the term `excitation class' according to the different input parameters used. The first method, which we refer to as Exneb relies purely on the ratios of certain key emission lines. The second method, which we refer to as Ex* includes modeling to create a continuous variable and, for optically thick PNe in the Magellanic Clouds, is designed to relate more closely to intrinsic stellar parameters. The third method, we refer to as Ex [OIII]/H-beta since the [OIII]/H-beta ratio is used in isolation to other temperature diagnostics. Each of these methods is shown to have serious drawbacks when used as an indicator for central star temperature. Finally, we suggest a new method (Exrho) for estimating excitation class incorporating both the [OIII]/H-beta and the HeII4686 /H-beta ratios. Although any attempt to provide accurate central star temperatures using the excitation class derived from nebula lines will always be limited, we show that this new method provides a substantial improvement over previous methods with better agreement to temperatures derived through the Zanstra method.
- [13] arXiv:0911.3699 [ps, pdf, other]
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Title: Planetary Formation and Evolution Revealed with a Saturn Entry Probe: The Importance of Noble GasesAuthors: Jonathan J. Fortney, Kevin Zahnle, Isabelle Baraffe, Adam Burrows, Sarah E. Dodson-Robinson, Gilles Chabrier, Tristan Guillot, Ravit Helled, Franck Hersant, William B. Hubbard, Jack J. Lissauer, Mark S. MarleyComments: 7 pages. Submitted to the Giant Planets panel of the 2013-2022 Planetary Science Decadal SurveySubjects: Earth and Planetary Astrophysics (astro-ph.EP)
The determination of Saturn's atmospheric noble gas abundances are critical to understanding the formation and evolution of Saturn, and giant planets in general. These measurements can only be performed with an entry probe. A Saturn probe will address whether enhancement in heavy noble gases, as was found in Jupiter, are a general feature of giant planets, and their ratios will be a powerful constraint on how they form. The helium abundance will show the extent to which helium has phase separated from hydrogen in the planet's deep interior. Jupiter's striking neon depletion may also be tied to its helium depletion, and must be confirmed or refuted in Saturn. Together with Jupiter's measured atmospheric helium abundance, a consistent evolutionary theory for both planets, including "helium rain" will be possible. We will then be able to calibrate the theory of the evolution of all giant planets, including exoplanets. In addition, high pressure H/He mixtures under giant planet conditions are an important area of condensed matter physics that are beyond the realm of experiment.
- [14] arXiv:0911.3709 [ps, pdf, other]
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Title: Simulating X-ray Supercavities and Their Impact on Galaxy ClustersComments: Submitted to ApJ. 11 pages, 6 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
Recent X-ray observations of hot gas in the galaxy cluster MS 0735.6+7421 reveal huge radio-bright, quasi-bipolar X-ray cavities having a total energy ~10^{62} ergs, the most energetic AGN outburst currently known. We investigate the evolution of this outburst with two-dimensional axisymmetric gasdynamical calculations in which the cavities are inflated by relativistic cosmic rays. Many key observational features of the cavities and associated shocks are successfully reproduced. The radial elongation of the cavities indicates that cosmic rays were injected into the cluster gas by a (jet) source moving out from the central AGN. AGN jets of this magnitude must be almost perfectly identically bipolar. The relativistic momentum of a single jet would cause a central AGN black hole of mass 10^9 M_{sun} to recoil at ~6000 km s^{-1}, exceeding kick velocities during black hole mergers, and be ejected from the cluster-center galaxy. When the cavity inflation is complete, 4PV underestimates the total energy received by the cluster gas. Deviations of the cluster gas from hydrostatic equilibrium are most pronounced during the early cavity evolution when the integrated cluster mass found from the observed gas pressure gradient can have systematic errors near the cavities of ~10-30%. The creation of the cavity with cosmic rays generates a long-lasting global cluster expansion that reduces the total gas thermal energy below that received from the cavity shock. One Gyr after this single outburst, a gas mass of ~ 6 \times 10^{11} M_{sun} is transported out beyond a cluster radius of 500 kpc. Such post-cavity outflows can naturally produce the discrepancy observed between the cluster gas mass fraction and the universal baryon fraction inferred from WMAP observations. (Abridged)
- [15] arXiv:0911.3728 [ps, pdf, other]
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Title: The Role of Starburst-AGN composites in Luminous Infrared Galaxy Mergers: Insights from the New Optical Classification SchemeComments: 30 pages, 19 figures, 10 tables, ApJ acceptedSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We investigate the fraction of starbursts, starburst-AGN composites, Seyferts, and LINERs as a function of infrared luminosity (L_IR) and merger progress for ~500 infrared-selected galaxies. Using the new optical classifications afforded by the extremely large data set of the Sloan Digital Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare (< 5%) compared with other spectral types. The lack of strong infrared emission in LINERs is consistent with recent optical studies suggesting that LINERs contain AGN with lower accretion rates than in Seyfert galaxies. Most previously classified infrared-luminous LINERs are classified as starburst-AGN composite galaxies in the new scheme. Starburst-AGN composites appear to "bridge" the spectral evolution from starburst to AGN in ULIRGs. The relative strength of the AGN versus starburst activity shows a significant increase at high infrared luminosity. In ULIRGs (L_IR >10^12 L_odot), starburst-AGN composite galaxies dominate at early--intermediate stages of the merger, and AGN galaxies dominate during the final merger stages. Our results are consistent with models for IR-luminous galaxies where mergers of gas-rich spirals fuel both starburst and AGN, and where the AGN becomes increasingly dominant during the final merger stages of the most luminous infrared objects.
- [16] arXiv:0911.3732 [ps, pdf, other]
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Title: Search for chameleon-like scalar fields with the ammonia methodComments: 23 pages, 11 figures, 6 tables. Accepted for publication in A&ASubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
(Abridged) The ammonia method, recently proposed to explore the electron-to-proton mass ratio, mu = m_e/m_p, is applied to nearby dark clouds in the Milky Way. This ratio, being measured in essentially different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models which predict strong dependence of masses and coupling constants on the local matter density. High resolution spectral observations of molecular cores in lines of NH3 (J,K) = (1,1), HC3N J = 2-1, and N2H+ J = 1-0 have been carried out at three radio telescopes in order to measure the radial velocity offsets, DeltaV = V_rot - V_inv, between the inversion transition of NH3 (1,1) and rotational transitions of other molecules having different sensitivities to the parameter dmm = (mu_obs - mu_lab)/mu_lab. The measured values of DeltaV show a statistically significant velocity offset of 23 +/- 4_stat +/- 3_sys m/s. Being interpreted in terms of mu-variation, this gives dmm = (2.2 +/- 0.4_stat +/- 0.3_sys)x10^{-8}. If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |DeltaV| <= 30 m/s. This gives the most accurate reference point at z = 0 for dmm: |dmm| <= 3x10^{-8}.
- [17] arXiv:0911.3734 [ps, pdf, other]
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Title: Dust tori in radio galaxiesComments: 17 pages, 9 figures, accepted for publication in Astronomy and AstrophysicsSubjects: Galaxy Astrophysics (astro-ph.GA)
We investigate the validity of the quasar - radio galaxy unification scenario and determine the presence of dust tori among radio galaxies of various types. Actively accreting supermassive black holes in the centres of radio galaxies may be uncovered through their dust tori reradiating the optical and ultraviolet continuum in mid-infrared bands. Using VISIR on the VLT, we have obtained sub-arcsecond (~0.40") resolution N-band images, at a wavelength of 11.85 micron, of the nuclei of a sample of 27 radio galaxies of four types in the redshift range z=0.006-0.156. The sample consists of 8 edge-darkened, low-power Fanaroff-Riley class I (FR-I) radio galaxies, 6 edge-brightened, class II (FR-II) radio galaxies displaying low-excitation optical emission, 7 FR-IIs displaying high-excitation optical emission, and 6 FR-II broad emission line radio galaxies. Out of the sample of 27 objects, 10 nuclei are detected and several have constraining non-detections at 10 sigma sensitivities of 7 mJy. On the basis of the core spectral energy distributions of this sample we find clear indications that many FR-I and several low-excitation FR-II radio galaxies lack warm dust tori. At least 57+-19 percent of the high-excitation FR-IIs and almost all broad line radio galaxies display excess infrared emission, which must be attributed to warm dust reradiating accretion activity. The FR-I and low-excitation FR-II galaxies all possess low efficiencies, calculated as the ratio of bolometric and Eddington luminosity log (L_bol/L_Edd) < -3. This suggests that thick tori are absent at low accretion rates and/or low efficiencies. We argue that the unification viewing angle range 0-45 degrees of quasars should be increased to ~60 degrees, at least at lower luminosities.
- [18] arXiv:0911.3740 [ps, pdf, other]
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Title: The VIMOS VLT Deep Survey: the group catalogueAuthors: O. Cucciati, C. Marinoni, A. Iovino, S. Bardelli, C. Adami, A. Mazure, M. Scodeggio, D. Maccagni, S. Temporin, E. Zucca, G. De Lucia, J. Blaizot, B. Garilli, B. Meneux, G. Zamorani, O. Le Fèvre, A. Cappi, L. Guzzo, D. Bottini, V. Le Brun, L. Tresse, G. Vettolani, A. Zanichelli, S. Arnouts, M. Bolzonella, S. Charlot, P. Ciliegi, T. Contini, S. Foucaud, P. Franzetti, I. Gavignaud, O. Ilbert, F. Lamareille, H.J. McCracken, B. Marano, R. Merighi, S. Paltani, R. Pellò, A. Pollo, L. Pozzetti, D. Vergani, E. Pérez-MonteroComments: Submitted to A&A, revised version after referee commentsSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
[Abridged] We used the purely flux limited (17.5<=I<=24.0) VIMOS-VLT Deep Survey (VVDS) sample to produce a homogeneous and complete optically-selected group catalogue, with reliable group properties. Using mock catalogues extracted from the MILLENNIUM simulations, we first studied how many groups can potentially be found in a survey with the same sampling rate as the VVDS, and then we tested how well the virial line of sight velocity dispersion (s_los) of such groups can be measured using galaxy velocities. We verified that, given VVDS observational strategy, we are able to recover s_los when s_los >= 350 km/s. We then optimized our group-finding algorithm, based on the Voronoi-Delaunay method, training it on mocks mimicking all the VVDS survey strategies: we required the redshift and s_los distributions of the output groups (n(z) and n(s_los)) to be in agreement with those given by the group halos defined in the simulations. We also maximized the completeness (C) and purity (P) of the output group catalogue. We then applied the algorithm to VVDS real data. We obtained a catalogue of 318 groups of galaxies within 0.2 <= z <= 1.0, globally with C=60% and P=50% and with n(z) and n(s_los>= 350 km/s) in agreement with those present in the simulations. Finally, we studied the fraction f_b of blue galaxies (U-B <= 1), for a complete subsample of galaxies in the range 0.2 <= z <= 1, and we found that f_b in groups is always significantly lower than f_b when considering all galaxies irrespectively of their environment: both f_b increase significantly with redshift, with a possibly steeper increase for group galaxies. We also found a general trend for f_b decreasing for increasing group richness, at any redshift explored.
- [19] arXiv:0911.3741 [ps, pdf, other]
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Title: Catalog of Radio Galaxies with z>0.3. I:Construction of the SampleComments: 9 pages, 6 figures, 2 tablesJournal-ref: Astrophys. Bull., 64, No 3, 263, 2009Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
The procedure of the construction of a sample of distant ($z>0.3$) radio galaxies using NED, SDSS, and CATS databases for further application in statistical tests is described. The sample is assumed to be cleaned from objects with quasar properties. Primary statistical analysis of the list is performed and the regression dependence of the spectral index on redshift is found.
- [20] arXiv:0911.3743 [ps, pdf, other]
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Title: Temporal properties of GX 301-2 over a year-long observation with SuperAGILEAuthors: Y. Evangelista, M. Feroci, E. Costa, E. Del Monte, I. Donnarumma, I. Lapshov, F. Lazzarotto, L. Pacciani, M. Rapisarda, P. Soffitta, A. Argan, G. Barbiellini, F. Boffelli, A. Bulgarelli, P. Caraveo, P.W. Cattaneo, A. Chen, F. D'Ammando, G. Di Cocco, F. Fuschino, M. Galli, F. Gianotti, A. Giuliani, C. Labanti, P. Lipari, F. Longo, M. Marisaldi, S. Mereghetti, E. Moretti, A. Morselli, A. Pellizzoni, F. Perotti, G. Piano, P. Picozza, M. Pilia, M. Prest, G. Pucella, A. Rappoldi, S. Sabatini, E. Striani, M. Tavani, M. Trifoglio, A. Trois, E. Vallazza, S. Vercellone, V. Vittorini, A. Zambra, L. A. Antonelli, S. Cutini, C. Pittori, B. Preger, P. Santolamazza, F. Verrecchia, P. Giommi, L. SalottiComments: 10 pages, 7 figures, 3 tables, accepted for publication in ApJSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
We present the long-term monitoring of the High Mass X-ray Binary GX 301-2 performed with the SuperAGILE instrument on-board the AGILE mission. The source was monitored in the 20-60 keV energy band during the first year of the mission from 2007 July 17 to 2008 August 31, covering about one whole orbital period and three more pre-periastron passages for a total net observation time of about 3.7 Ms. The SuperAGILE dataset represents one of the most continuous and complete monitoring at hard X-ray energies of the 41.5 day long binary period available to date. The source behaviour was characterized at all orbital phases in terms of hard X-ray flux, spectral hardness, spin period history, pulsed fraction and pulse shape profile. We also complemented the SuperAGILE observations with the soft X-ray data of the RossiXTE/ASM. Our analysis shows a clear orbital modulation of the spectral hardness, with peaks in correspondence of the pre-periastron flare and near phase 0.25. The hardness peaks we found could be related with the wind-plus-stream accretion model proposed in order to explain the orbital light curve modulation of GX 301-2. Timing analysis of the pulsar spin period shows that the secular trend of the about 680 s pulse period is consistent with the previous observations, although there is evidence of a slight decrease in the spin-down rate. The analysis of the hard X-ray pulsed emission also showed a variable pulse shape profile as a function of the orbital phase, with substructures detected near the passage at the periastron, and a clear modulation of the pulsed fraction, which appears in turn strongly anti-correlated with the source intensity.
- [21] arXiv:0911.3747 [ps, pdf, other]
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Title: Catalog of Radio Galaxies with z>0.3. II: Photometric DataComments: 8 pages, 5 figures, 2 tablesJournal-ref: Astrophys. Bull., 64, No 3, 276, 2009Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
We describe the procedure of the construction of a sample of distant ($z>0.3$) radio galaxies using the NED, SDSS, and CATS databases. We believe the sample to be free of objects with quasar properties. This paper is the second part of the description of the radio galaxies catalog we plan to use for cosmological tests. We report the photometric parameters for the objects of the list, and perform its preliminary statistical analysis including the construction of the Hubble diagrams.
- [22] arXiv:0911.3752 [ps, pdf, other]
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Title: Catalog of Radio Galaxies with z>0.3. III: Angular Sizes and Flux Density According to the NVSS DataComments: 6 pages, 4 figures, 1 tableSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
We describe the procedure of the construction of a sample of distant ($z>0.3$) radio galaxies using the NED, CATS and SDSS databases for further use in various statistical tests. We believe the sample to be free of objects with quasar properties. This paper is the third part of the description of the radio galaxies catalog that we plan to use for cosmological tests. We report the results of the sample of angular sizes for the NVSS survey list objects, and its preliminary statistical analysis. Three-parameter diagrams "angular size-redshift-flux density" and "angular size-redshift-spectral index", and their two-parameter projections are constructed. Three subsamples of radio galaxies are separated in the "source size--flux density" diagram.
- [23] arXiv:0911.3763 [ps, pdf, other]
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Title: Metallicity gradients in the Milky WayComments: 8 pages, 3 figures, uses iaus.cls, in press, IAU Symp. 265, Chemical abundances in the Universe: Connecting the first Stars to Planets, Ed. K. Cunha, M. Spite, B. BarbuySubjects: Galaxy Astrophysics (astro-ph.GA)
Radial metallicity gradients are observed in the disks of the Milky Way and in several other spiral galaxies. In the case of the Milky Way, many objects can be used to determine the gradients, such as HII regions, B stars, Cepheids, open clusters and planetary nebulae. Several elements can be studied, such as oxygen, sulphur, neon, and argon in photoionized nebulae, and iron and other elements in cepheids, open clusters and stars. As a consequence, the number of observational characteristics inferred from the study of abundance gradients is very large, so that in the past few years they have become one of the main observational constraints of chemical evolution models. In this paper, we present some recent observational evidences of abundance gradients based on several classes of objects. We will focus on (i) the magnitude of the gradients, (ii) the space variations, and (iii) the evidences of a time variation of the abundance gradients. Some comments on recent theoretical models are also given, in an effort to highlight their predictions concerning abundance gradients and their variations.
- [24] arXiv:0911.3772 [ps, pdf, other]
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Title: Molecular Gas in NUclei of GAlaxies (NUGA) XIII. The interacting Seyfert 2/LINER galaxy NGC 5953Authors: V. Casasola (1,2), L.K. Hunt (1), F. Combes (3), S. Garcia-Burillo (4), F. Boone (3), A. Eckart (5), R. Neri (6), E. Schinnerer (7) ((1) INAF-Osservatorio Astrofisico di Arcetri, Firenze, (2) INAF-IRA Bologna, (3) Obs. de Paris LERMA, (4) OAN-Obs. de Madrid, (5) I. Physikalisches Institut, Un. zu Koln, (6) IRAM St.Mt.d`Heres, (7) MPIA Heidelberg)Comments: 21 pages, 23 figures, 2 tables, accepted for publication in Astronomy and AstrophysicsSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We present $^{12}$CO(1--0) and $^{12}$CO(2--1) maps of the interacting Seyfert 2/LINER galaxy NGC 5953 obtained with the IRAM interferometer at resolutions of 2\farcs1 $\times$ 1\farcs4 and 1\farcs1 $\times$ 0\farcs7, respectively. The CO emission is distributed over a disk of diameter $\sim$16\arcsec ($\sim$2.2 kpc), within which are several, randomly distributed peaks. The strongest peak does not coincide with the nucleus, but is instead offset from the center, $\sim2-3^{\prime\prime}$ ($\sim$340 pc) toward the west/southwest. The kinematics of the molecular component are quite regular, as is typical of a rotating disk. We also compared the $^{12}$CO distribution of NGC 5953 with observations at other wavelengths in order to study correlations between different tracers of the interstellar medium. Using NIR images, we computed the gravity torques exerted by the stellar potential on the gas. The torques are predominantly positive in both $^{12}$CO(1--0) and $^{12}$CO(2--1), suggesting that gas is not flowing into the center, and less than 5% of the gas angular momentum is exchanged in each rotation. This comes from the regular and almost axisymmetric total mass and gas distributions in the center of the galaxy. In NGC 5953, the AGN is apparently not being actively fueled in the current epoch.
- [25] arXiv:0911.3774 [pdf, other]
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Title: Characteristic velocities of stripped-envelope core-collapse supernova coresAuthors: I. Maurer, P. A. Mazzali, J. Deng, A. V. Filippenko, M. Hamuy, R. P. Kirshner, T. Matheson, M. Modjaz, E. Pian, M. Stritzinger, S. Taubenberger, S. ValentiComments: 14 pages, 10 figures, MNRAS acceptedSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
The velocity of the inner ejecta of stripped-envelope core-collapse supernovae (CC-SNe) is studied by means of an analysis of their nebular spectra. Stripped-envelope CC-SNe are the result of the explosion of bare cores of massive stars ($\geq 8$ M$_{\odot}$), and their late-time spectra are typically dominated by a strong [O {\sc i}] $\lambda\lambda$6300, 6363 emission line produced by the innermost, slow-moving ejecta which are not visible at earlier times as they are located below the photosphere. A characteristic velocity of the inner ejecta is obtained for a sample of 56 stripped-envelope CC-SNe of different spectral types (IIb, Ib, Ic) using direct measurements of the line width as well as spectral fitting. For most SNe, this value shows a small scatter around 4500 km s$^{-1}$. Observations ($< 100$ days) of stripped-envelope CC-SNe have revealed a subclass of very energetic SNe, termed broad-lined SNe (BL-SNe) or hypernovae, which are characterised by broad absorption lines in the early-time spectra, indicative of outer ejecta moving at very high velocity ($v \geq 0.1 c$). SNe identified as BL in the early phase show large variations of core velocities at late phases, with some having much higher and some having similar velocities with respect to regular CC-SNe. This might indicate asphericity of the inner ejecta of BL-SNe, a possibility we investigate using synthetic three-dimensional nebular spectra.
- [26] arXiv:0911.3778 [pdf, other]
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Title: The circumnuclear environment of the peculiar galaxy NGC 3310Authors: Guillermo F. Hagele, Angeles I. Diaz, Monica V. Cardaci, Elena Terlevich, Roberto TerlevichComments: 24 pages, accepted by MNRASSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Gas and star velocity dispersions have been derived for eight circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC3310 using high resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet in the near-IR, using cross-correlation techniques, while gas velocity dispersions have been measured by Gaussian fits to the Hb 4861A and [OIII]5007A emission lines.
The CNSFRs stellar velocity dispersions range from 31 to 73 km/s. These values, together with the sizes measured on archival HST images, yield upper limits to the dynamical masses for the individual star clusters between 1.8 and 7.1 x 10$^6$ M$_\odot$, for the whole CNSFR between 2 x 10$^7$ and 1.4 x 10$^8$ M$_\odot$, and 5.3 x 10$^7$ M$_\odot$ for the nucleus inside the inner 14.2 pc. The masses of the ionizing stellar population responsible for the HII region gaseous emission have been derived from their published Ha luminosities and are found to be between 8.7 x 10$^5$ and 2.1 x 10$^6$ M$_\odot$ for the star-forming regions, and 2.1 x 10$^5$ M$_\odot$ for the galaxy nucleus; they therefore constitute between 1 and 7 per cent of the total dynamical mass.
The ionized gas kinematics is complex; two different kinematical components seem to be present as evidenced by different line widths and Doppler shifts. - [27] arXiv:0911.3779 [ps, pdf, other]
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Title: The Skeleton: Connecting Large Scale Structures to Galaxy FormationAuthors: Christophe Pichon, Christophe Gay, Dmitry Pogosyan, Simon Prunet, Thierry Sousbie, Stephane Colombi, Adrianne Slyz, Julien DevriendtComments: 10 pages, 8 figures; proceedings of the "Invisible Universe" 2009Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
We report on two quantitative, morphological estimators of the filamentary structure of the Cosmic Web, the so-called global and local skeletons. The first, based on a global study of the matter density gradient flow, allows us to study the connectivity between a density peak and its surroundings, with direct relevance to the anisotropic accretion via cold flows on galactic halos.
From the second, based on a local constraint equation involving the derivatives of the field, we can derive predictions for powerful statistics, such as the differential length and the relative saddle to extrema counts of the Cosmic web as a function of density threshold (with application to percolation of structures and connectivity), as well as a theoretical framework to study their cosmic evolution through the onset of gravity-induced non-linearities. - [28] arXiv:0911.3785 [ps, pdf, other]
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Title: Spiral-like structure in nearby clusters of galaxiesComments: 14 pages, 3 figures, accepted for publication in A&A (Nov 17, 2009)Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
X-ray data analysis have recently revealed fairly complex structures in cluster centres to be more common than expected. Besides, great part of these structures resemble in morphology, presenting a spiral-like substructure. It is not yet well known how this specific pattern is formed or maintained. In particular, understanding the nature of these spiral-like feature at the centre of some clusters is the major motivation of this work. We analyse Chandra deep observation data of 15 nearby galaxy clusters (0.01 < z < 0.06). We used X-ray temperature and substructure maps to detect small features in the core of the clusters. We detect a spiral-like feature in the centre of 7 clusters: A85, A426, A496, Hydra A cluster, Centaurus, Ophiuchus and A4059. This particular pattern is similar to those found in numerical hydrodynamic simulations of cluster merger with non-zero impact parameter. In some clusters of our sample a strong radio source also occupies the inner region of the cluster, suggesting a possible connection between the two. Our investigation lends support to the fact that these spiral-like structures are due to off-axis minor mergers. Since these features are regions of high density they may confine radio emission from the central galaxy producing, in some cases, unusual radio morphology.
- [29] arXiv:0911.3790 [ps, pdf, other]
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Title: Large-scale magnetic fields in cosmologyAuthors: Christos G. TsagasComments: Invited Talk (36th EPS Conference on Plasma Physics, 2009)Journal-ref: Plasm.Phys.Control.Fus. 51:124013,2009Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Despite the widespread presence of magnetic fields, their origin, evolution and role are still not well understood. Primordial magnetism sounds appealing but is not problem free. The magnetic implications for the large-scale structure of the universe still remain an open issue. This paper outlines the advantages and shortcomings of early-time magnetogenesis and the typical role of B-fields in linear structure-formation scenarios.
- [30] arXiv:0911.3791 [ps, pdf, other]
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Title: Surface structure of the CoRoT CP2 target star HD 50773Authors: T. Lüftinger, H.-E. Fröhlich, W. Weiss, P. Petit, M. Aurière, N. Nesvacil, M. Gruberbauer, D. Shulyak, E. Alecian, A. Baglin, F. Baudin, C. Catala, J.-F. Donati, O. Kochukhov, E. Michel, N. Piskunov, T. Roudier, R. SamadiComments: 12 pages, 9 figuresSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
We compare surface maps of the chemically peculiar star HD 50773 produced with a Bayesian technique and based on high quality CoRoT photometry with those derived from rotation phase resolved spectropolarimetry. The goal is to investigate the correlation of surface brightness with surface chemical abundance distribution and the stellar magnetic field.
The rotational period of the star was determined from a nearly 60 day long continuous light curve obtained during the initial run of CoRoT. Using a Bayesian approach to star-spot modelling, which in this work is applied for the first time for the photometric mapping of a CP star, we derived longitudes, latitudes and radii of four different spot areas. Additional parameters like stellar inclination and the spot's intensities were also determined. The CoRoT observations triggered an extensive ground-based spectroscopic and spectropolarimetric observing campaign and enabled us to obtain 19 different high resolution spectra in Stokes parameters I and V with NARVAL, ESPaDOnS, and SemelPol spectropolarimeters.
Doppler and Magnetic Doppler imaging techniques allowed us to derive the magnetic field geometry of the star and the surface abundance distributions of Mg, Si, Ca, Ti, Cr, Fe, Ni, Y, and Cu. We find a dominant dipolar structure of the surface magnetic field. The CoRoT light curve variations and abundances of most elements mapped are correlated with the aforementioned geometry: Cr, Fe, and Si are enhanced around the magnetic poles and coincide with the bright regions on the surface of HD 50773 as predicted by our light curve synthesis and confirmed by photometric imaging. - [31] arXiv:0911.3798 [ps, pdf, other]
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Title: Rotational asymmetry of pulsar profilesComments: 12 pages, 7 figures, submitted to MNRASSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
We analyse the influence of rotation on shapes of pulse profiles of fast-rotating (millisecond) pulsars. Corotation has two opposing effects: 1) the caustic enhancement of the trailing side (TS) by aberration and retardation (AR), which squeezes the emission into a narrower phase interval; 2) the weakening of the TS caused by the asymmetry of curvature radiation about the dipole axis. Analysis of the radii of curvature of electron trajectories in the inertial observer's frame (IOF) enables these two effects to be considered together. We demonstrate that for dipolar magnetic field lines on the TS there exists a `caustic phase' beyond which no emission can be observed. This phase corresponds to the zero (or minimum) curvature of the IOF trajectories and maximum bunching of the emission. The maximum gradient of polarisation angle (PA) in the S-shaped PA curve is also associated with the curvature minimum and occurs at exactly the same phase. The asymmetry of trajectory curvature with respect to the dipole axis affects the curvature emissivity and the efficiency of pair production, suggesting a minimum at the caustic phase. Emission over a fixed range of altitudes, as expected in millisecond pulsars, leads to broad leading profiles and sharp peaks with a cutoff phase on the TS. We apply our results to the main pulse of the 5 ms pulsar J1012+5307.
- [32] arXiv:0911.3804 [ps, pdf, other]
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Title: Searching for flickering statistics in T CrBComments: 9 pages, 10 figures, accepted for publication in MNRASSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
We analyze $V$-band photometry of the aperiodic variability in T CrB. By applying a simple idea of angular momentum transport in the accretion disc, we have developed a method to simulate the statistical distribution of flare durations with the assumption that the aperiodic variability is produced by turbulent elements in the disc. Both cumulative histograms with Kolmogorov-Smirnov tests, and power density spectra are used to compare the observed data and simulations. The input parameters of the model $R_{\rm in}$ and $\alpha$ are correlated on a certain interval and the most probable values are an inner disc radius of $R_{\rm in} \simeq 4 \times 10^9$ cm and a viscosity of $\alpha \simeq 0.9$. The disc is then weakly truncated. We find that the majority of turbulent events producing flickering activity are concentrated in the inner parts of the accretion disc.
- [33] arXiv:0911.3809 [ps, pdf, other]
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Title: The discovery of a massive white dwarf in the peculiar binary system HD 49798/RX J0648.0-4418Authors: S.Mereghetti, A.Tiengo, P.Esposito, N.La Palombara (1), G.L.Israel, L.Stella (2) ((1) INAF-IASF Milano, (2) INAF, Oss. Astron. Roma)Comments: Proceedings of the conference X-Ray Astronomy 2009, Present Status, multiwavelength approach and future perspectives, September 7 - 11, 2009, Bologna, ItalySubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
An XMM-Mewton observation performed in May 2008 has confirmed that the 13 seconds pulsations in the X-ray binary HD 49798/RX J0648.0-4418 are due to a rapidly rotating white dwarf. From the pulse time delays induced by the 1.55 days orbital motion, and the system's inclination, constrained by the duration of the X-ray eclipse discovered in this observation, we could derive a mass of 1.28+/-0.05 M_sun for the white dwarf. The future evolution of this post common envelope binary system will likely involve a new phase of mass accretion through Roche-lobe overflow that could drive the already massive white dwarf above the Chandrasekhar limit and produce a Type Ia supernova.
- [34] arXiv:0911.3817 [ps, pdf, other]
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Title: ACRIM-gap and total solar irradiance revisited: Is there a secular trend between 1986 and 1996?Comments: 4 figuresJournal-ref: Geophys. Res. Lett., 36, L20101, doi:10.1029/2009GL040707Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
A gap in the total solar irradiance (TSI) measurements between ACRIM-1 and ACRIM-2 led to the ongoing debate on the presence or not of a secular trend between the minima preceding cycles 22 (in 1986) and 23 (1996). It was recently proposed to use the SATIRE model of solar irradiance variations to bridge this gap. When doing this, it is important to use the appropriate SATIRE-based reconstruction, which we do here, employing a reconstruction based on magnetograms. The accuracy of this model on months to years timescales is significantly higher than that of a model developed for long-term reconstructions used by the ACRIM team for such an analysis. The constructed `mixed' ACRIM - SATIRE composite shows no increase in the TSI from 1986 to 1996, in contrast to the ACRIM TSI composite.
- [35] arXiv:0911.3820 [ps, pdf, other]
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Title: Bayesian coherent analysis of in-spiral gravitational wave signals with a detector networkComments: 22 pages, submitted to Phys. Rev. DSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)
The present operation of the ground-based network of gravitational-wave laser interferometers in "enhanced" configuration brings the search for gravitational waves into a regime where detection is highly plausible. The development of techniques that allow us to discriminate a signal of astrophysical origin from instrumental artefacts in the interferometer data and to extract the full range of information are some of the primary goals of the current work. Here we report the details of a Bayesian approach to the problem of inference for gravitational wave observations using a network of instruments, for the computation of the Bayes factor between two hypotheses and the evaluation of the marginalised posterior density functions of the unknown model parameters. The numerical algorithm to tackle the notoriously difficult problem of the evaluation of large multi-dimensional integrals is based on a technique known as Nested Sampling, which provides an attractive alternative to more traditional Markov-chain Monte Carlo (MCMC) methods. We discuss the details of the implementation of this algorithm and its performance against a Gaussian model of the background noise, considering the specific case of the signal produced by the in-spiral of binary systems of black holes and/or neutron stars, although the method is completely general and can be applied to other classes of sources. We also demonstrate the utility of this approach by introducing a new coherence test to distinguish between the presence of a coherent signal of astrophysical origin in the data of multiple instruments and the presence of incoherent accidental artefacts, and the effects on the estimation of the source parameters as a function of the number of instruments in the network.
- [36] arXiv:0911.3825 [ps, pdf, other]
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Title: Intrinsic colors and ages of extremely red elliptical galaxies at high redshiftAuthors: Martin Lopez-CorredoiraComments: accepted to be published in AJSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
In order to know the formation epoch of the oldest elliptical galaxies as a function of mass and observed redshift, a statistical analysis for 333 extremely red objects (EROs) classified as old galaxies (OGs) at 0.8<z<2.3 is carried out. Once we get M_V and (B-V) at rest for each galaxy, we calculate the average variation of this intrinsic color with redshift and derive the average age through a synthesis model (the code for the calculation of the age has been made publicly available). The average gradient of the (B-V) color at rest of EROs/OGs is 0.07-0.10 Gyr^{-1} for a fixed luminosity. The stars in these extremely red elliptical galaxies were formed when the Universe was ~2 Gyr old on average. We have not found a significant enough dependence on the observed redshift and stellar mass: dt_{formation}/dt_{observed}=-0.46+/-0.32, dt_{formation}/(d log_10 M_*)=-0.81+/-0.98 Gyr. This fits a scenario in which the stellar formation of the objects that we denominate as EROs-OGs is more intense at higher redshifts, at which the stellar populations of the most massive galaxies form earlier than or at the same time as less massive galaxies.
- [37] arXiv:0911.3826 [pdf]
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Title: Extent radiation in different types of radio sourcesAuthors: Alla P. MiroshnichenkoComments: 4 pages, 6 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
The contribution of an extent component of source radio emission is estimated for quasars and galaxies. The consideration of source radio structures at kiloparsec scales is used at the decameter and the higher frequency bands. The determination of the contribution of an extent component to source radio emission as well as main physical parameters of sample sources is carried out. We found that especially extent sources, giant radio galaxies, have smaller luminosity of core region, weaker magnetic field and greater characteristic age in comparison with compact radio galaxies and quasars. As it follows from our examination, the extent component contribution to source emission may be the indicator of the radio source age.
- [38] arXiv:0911.3841 [pdf, other]
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Title: Advanced Technology Large-Aperture Space Telescope (ATLAST): Characterizing Habitable WorldsAuthors: M. Postman, W. Traub, J. Krist, K. Stapelfeldt, R. Brown, W. Oegerle, A. Lo, M. Clampin, R. Soummer, J. Wiseman, M. MountainComments: 6 pages, 4 figures, Proceedings submitted for "Pathways towards Habitable Planets" Symposium, Barcelona, Spain, Sept 14-19, 2009Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
The Advanced Technology Large Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation UV-Optical-Near Infrared space telescope with an aperture size of 8 to 16 meters. ATLAST, using an internal coronagraph or an external occulter, can characterize the atmosphere and surface of an Earth-sized exoplanet in the Habitable Zone of long-lived stars at distances up to ~45 pc, including its rotation rate, climate, and habitability. ATLAST will also allow us to glean information on the nature of the dominant surface features, changes in cloud cover and climate, and, potentially, seasonal variations in surface vegetation. ATLAST will be able to visit up to 200 stars in 5 years, at least three times each, depending on the technique used for starlight suppression and the telescope aperture. More frequent visits can be made for interesting systems.
- [39] arXiv:0911.3844 [ps, pdf, other]
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Title: Physical Properties of Young Brown Dwarfs and Very Low-Mass Stars Inferred from High-Resolution Model SpectraComments: Accepted to the Astrophysical Journal Supplement SeriesSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
By comparing near-infrared spectra with atmosphere models, we infer the effective temperature, surface gravity, projected rotational velocity, and radial velocity for 21 very-low-mass stars and brown dwarfs. The unique sample consists of two sequences in spectral type from M6-M9, one of 5-10 Myr objects and one of >1 Gyr field objects. A third sequence is comprised of only ~M6 objects with ages ranging from <1 Myr to >1 Gyr. Spectra were obtained in the J band at medium (R~2,000) and high (R~20,000) resolutions with NIRSPEC on the Keck II telescope. Synthetic spectra were generated from atmospheric structures calculated with the PHOENIX model atmosphere code. Using multi-dimensional least-squares fitting and Monte Carlo routines we determine the best-fit model parameters for each observed spectrum and note which spectral regions provide consistent results. We identify successes in the reproduction of observed features by atmospheric models, including pressure-broadened KI lines, and investigate deficiencies in the models, particularly missing FeH opacity, that will need to be addressed in order to extend our analysis to cooler objects. The precision that can be obtained for each parameter using medium- and high- resolution near-infrared spectra is estimated and the implications for future studies of very low mass stars and brown dwarfs are discussed.
- [40] arXiv:0911.3852 [ps, pdf, other]
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Title: Light-cone observations and cosmological models: implications for inhomogeneous models mimicking dark energyComments: 18 pages, 13 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Cosmological observables are used to construct cosmological models. Since cosmological observations are limited to the light cone, a fixed number of observables (even measured to arbitrary accuracy) may not uniquely determine a cosmological model without additional assumptions or considerations. A prescription for constructing a spherically symmetric, inhomogeneous cosmological model that exactly reproduces the luminosity-distance as a function of redshift and the light-cone mass density as a function of redshift of a $\Lambda$CDM model is employed to gain insight into how an inhomogeneous cosmological model might mimic dark energy models.
- [41] arXiv:0911.3853 [ps, pdf, other]
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Title: Spatial and temporal variations of fundamental constantsComments: 9 pages, 6 figures. IAU 2009 JD9 conference proceedings, Mem. S. A. It., vol. 80, in press, eds. Paolo Molaro and Elisabeth VangioniSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Spatial and temporal variations in the electron-to-proton mass ratio, mu, and in the fine-structure constant, alpha, are predicted in non-Standard models aimed to explain the nature of dark energy. Among them the so-called chameleon-like scalar field models predict strong dependence of masses and coupling constants on the local matter density. To explore such models we estimated the parameters Delta mu/mu = (mu_obs - mu_lab)/mu_lab and Delta alpha/alpha = (alpha_obs - alpha_lab)/alpha_lab in two essentially different environments, - terrestrial (high density) and interstellar (low density), - from radio astronomical observations of cold prestellar molecular cores in the disk of the Milky Way. We found that Delta mu/mu = (22 +/- 4_stat +/- 3_sys)x10^{-9}, and |Delta alpha/alpha| < 1.1x10^{-7}. If only a conservative upper limit is considered, then |Delta mu/mu| <= 3x10^{-8}. We also reviewed and re-analyzed the available data on the cosmological variation of alpha obtained from FeI and FeII systems in optical spectra of quasars. We show that statistically significant evidence for the changing alpha at the level of 10^{-6} has not been provided so far. The most stringent constraint on |Delta alpha/alpha| < 2x10^{-6} was found from the FeII system at z = 1.15 towards the bright quasar HE0515-4414. The limit of 2x10^{-6} corresponds to the utmost accuracy which can be reached with available to date optical facilities.
- [42] arXiv:0911.3873 [ps, pdf, other]
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Title: The Formation of Uranus and Neptune in Solid-Rich Feeding Zones: Connecting Chemistry and DynamicsAuthors: Sarah E. Dodson-Robinson (1), Peter Bodenheimer (2) ((1) University of Texas, (2) UCO/Lick Observatory)Comments: Accepted for publication in Icarus. 9 pages, including 3 figuresSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
The core accretion theory of planet formation has at least two fundamental problems explaining the origins of Uranus and Neptune: (1) dynamical times in the trans-Saturnian solar nebula are so long that core growth can take > 15 Myr, and (2) the onset of runaway gas accretion that begins when cores reach 10 Earth masses necessitates a sudden gas accretion cutoff just as the ice giant cores reach critical mass. Both problems may be resolved by allowing the ice giants to migrate outward after their formation in solid-rich feeding zones with planetesimal surface densities well above the minimum-mass solar nebula. We present new simulations of the formation of Uranus and Neptune in the solid-rich disk of Dodson-Robinson et al. (2009) using the initial semimajor axis distribution of the Nice model (Gomes et al. 2005; Morbidelli et al. 2005; Tsiganis et al. 2005), with one ice giant forming at 12 AU and the other at 15 AU. The innermost ice giant reaches its present mass after 3.8-4.0 Myr and the outermost after 5.3-6 Myr, a considerable time decrease from previous one-dimensional simulations (e.g. Pollack et al. 1996). The core masses stay subcritical, eliminating the need for a sudden gas accretion cutoff. Our calculated carbon mass fractions of 22% are in excellent agreement with the ice giant interior models of Podolak et al. (1995) and Marley et al. (1995). Based on the requirement that the ice giant-forming planetesimals contain >10% mass fractions of methane ice, we can reject any solar system formation model that initially places Uranus and Neptune inside the orbit of Saturn. We also demonstrate that a large population of planetesimals must be present in both ice giant feeding zones throughout the lifetime of the gaseous nebula.
- [43] arXiv:0911.3879 [ps, pdf, other]
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Title: Star Formation in Dwarf Galaxies of the Nearby Centaurus A GroupAuthors: Stephanie Cote (1), Adam Draginda (1,2), Evan D. Skillman (3), Bryan W. Miller (4) ((1) Canadian Gemini Office, HIA, NRC, (2) CFHT, (3) U. of Minnesota, (4) AURA/Gemini Observatory, Chile)Comments: 57 pages, 10 fi5guresJournal-ref: Published in The Astronomical Journal, Volume 138, Issue 4, pp. 1037-1061 (2009)Subjects: Galaxy Astrophysics (astro-ph.GA)
We present Halpha narrow-band imaging of 17 dwarf irregular galaxies (dIs) in the nearby Centaurus A Group. Although all large galaxies of the group have a current or recent enhanced star formation episode, the dIs have normal star formation rates and do not contain a larger fraction of dwarf starbursts than other nearby groups. Relative distances between dIs and larger galaxies of the group can be computed in 3D since most of them have now fairly accurately known distances. We find that the dI star formation rates do not depend on local environment, and in particular they do not show any correlation with the distance of the dI to the nearest large galaxy of the group. There is a clear morphology-density relation in the Centaurus A Group, similarly to the Sculptor and Local Groups, in the sense that dEs/dSphs tend to be at small distances from the more massive galaxies of the group, while dIs are on average at larger distances. We find four transition dwarfs in the Group, dwarfs that show characteristics of both dE/dSphs and dIs, and which contain cold gas but no current star formation. Interestingly the transition dwarfs have an average distance to the more massive galaxies which is intermediate between those of the dEs/dSphs and dIs, and which is quite large: 0.54 +- 0.31 Mpc. This large distance poses some difficulty for the most popular scenarios proposed for transforming a dI into a dE/dSph (ram-pressure with tidal stripping or galaxy harassment). If the observed transition dwarfs are indeed missing links between dIs and dE/dSphs, their relative isolation makes it less likely to have been produced by these mechanisms. We propose that an inhomogeneous IGM containing higher density clumps would be able to ram-pressure stripped the dIs at such large distances.
- [44] arXiv:0911.3883 [ps, pdf, other]
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Title: Metal Enrichment via Ram Pressure Stripping in the IGM of the Compact Galaxy Group RGH 80Authors: Haijuan Cui (1), Haiguang Xu (1), Junhua Gu (1), Jingying Wang (1), Liyi Gu (1), Yu Wang (1), Zhenzhen Qin (1) ((1) Shanghai Jiao Tong University)Comments: Submitted to RAA, and revisedSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
By creating and analyzing the two dimensional gas temperature and abundance maps of the RGH 80 compact galaxy group with the high-quality Chandra data, we detect a high-abundance ($\simeq 0.7$ $Z_\odot$) arc, where the metal abundance is significantly higher than the surrounding regions by $\simeq 0.3$ Z_\odot$. This structure shows tight spatial correlations with the member galaxy PGC 046529, as well as with the arm-like feature identified on the X-ray image in the previous work of Randall et al. (2009). Since no apparent signature of AGN activity is found associated with PGC 046529 in multi-band observations, and the gas temperature, metallicity, and mass of the high-abundance arc resemble those of the ISM of typical early-type galaxies, we conclude that this high-abundance structure is the remnant of the ISM of PGC 046529, which was stripped out of the galaxy by ram pressure stripping due to the motion of PGC 046529 in RGH 80. This novel case shows that ram pressure stripping can work efficiently in the metal enrichment process in galaxy groups, as it can in galaxy clusters.
Cross-lists for Fri, 20 Nov 09
- [45] arXiv:0911.2781 (cross-list from hep-th) [ps, pdf, other]
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Title: Is the future universe singular: Dark Matter versus modified gravity?Comments: LaTeX 9 pagesSubjects: High Energy Physics - Theory (hep-th); Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
The fundamental problem of the occurrence/removal of finite-time future singularity in the universe evolution for coupled dark energy (DE) is addressed. It is demonstrated the existence of the (instable or local minimum) de Sitter space solution which may cure the Type II or Type IV future singularity for DE coupled with DM as the result of tuning the initial conditions. In case of phantom DE, the corresponding coupling may help to resolve the coincidence problem but not the Big Rip (Type I) singularity issue. We show that modified gravity of special form or inhomogeneous DE fluid may offer the universal scenario to cure the Type I,II,III or IV future singularity of coupled (fluid or scalar) DE evolution.
- [46] arXiv:0911.3380 (cross-list from hep-th) [ps, pdf, other]
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Title: Quasi-Single Field Inflation and Non-GaussianitiesComments: 56 pagesSubjects: High Energy Physics - Theory (hep-th); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
In quasi-single field inflation models, massive isocurvature modes, that are coupled to the inflaton and have mass of order the Hubble parameter, can have nontrivial impacts on density perturbations, especially non-Gaussianities. We study a simple example of quasi-single field inflation in terms of turning inflaton trajectory. Large bispectra with a one-parameter family of novel shapes arise, lying between the well-known local and equilateral shape. The trispectra can also be very large and its magnitude tNL can be much larger than fNL squared.
Replacements for Fri, 20 Nov 09
- [47] arXiv:0706.3050 (replaced) [ps, pdf, other]
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Title: Cold dark matter from "strong gravity"Authors: T. R. MonganComments: Shortened, with added remarks on the relation of the dark matter candidate to a minimum mass for black holes, DAMA/LIBRA results and dark matter production at acceleratorsSubjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics - Theory (hep-th)
- [48] arXiv:0812.1020 (replaced) [ps, pdf, other]
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Title: Sensitivity of cosmic-ray experiments to ultra-high-energy photons: reconstruction of the spectrum and limits on the superheavy dark matterComments: 18 pages, 7 figuresJournal-ref: Phys.Rev.D80:103006,2009Subjects: Astrophysics (astro-ph)
- [49] arXiv:0901.4325 (replaced) [ps, pdf, other]
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Title: Angular Momentum and the Formation of Stars and Black HolesAuthors: Richard B. LarsonComments: Accepted by Reports on Progress in PhysicsSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [50] arXiv:0905.2176 (replaced) [ps, pdf, other]
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Title: Electric dipole moments and disalignment of interstellar dust grainsComments: 12 pages, 9 figures, submitted to MNRASJournal-ref: MNRAS Volume 400,Issue 1,Date: November 2009,Pages: 536-547Subjects: Galaxy Astrophysics (astro-ph.GA)
- [51] arXiv:0906.0905 (replaced) [ps, pdf, other]
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Title: A (giant) void is not mandatory to explain away dark energy with a Lemaitre -- Tolman modelComments: 21 pages, 20 figures, version extended to match the submitted articleSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [52] arXiv:0906.0933 (replaced) [ps, pdf, other]
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Title: The Nova Shell and Evolution of the Recurrent Nova T PyxidisComments: Astrophysical Journal in press, 62 pages, 11 figures (accepted version; minor changes and shortening)Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [53] arXiv:0906.1200 (replaced) [ps, pdf, other]
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Title: Reynolds stresses from hydrodynamic turbulence with shear and rotationAuthors: J. E. Snellman (1), P. J. Käpylä (1,2), M. J. Korpi (1), A. J. Liljeström (1) ((1) University of Helsinki, (2) NORDITA)Comments: 19 pages, 12 figures, published versionJournal-ref: Astron. Astrophys. 505, 955-968 (2009)Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [54] arXiv:0907.4145 (replaced) [ps, pdf, other]
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Title: COSMOS 5921+0638: Characterization and analysis of a new strong gravitationally lensed AGNAuthors: T. Anguita (1), C. Faure (2), J.-P. Kneib (3), J. Wambsganss (1), C. Knobel (4), A. M. Koekemoer (5), M. Limousin (3,6) ((1) ARI/Zentrum fuer Astronomie, University of Heidelberg, Germany (2) EPFL, Switzerland (3) LAM, France (4) ETH, Switzerland (5) STScI, USA (6) Dark Cosmology Centre, University of Copenhagen, Denmark)Comments: 12 pages, 12 figures. Updated to match A&A published versionJournal-ref: A&A 507, 35-46 (2009)Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [55] arXiv:0908.2423 (replaced) [ps, pdf, other]
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Title: The alpha effect in rotating convection with sinusoidal shearAuthors: P. J. Käpylä (1,2), M. J. Korpi (1,2), A. Brandenburg (2,3) ((1) University of Helsinki, (2) NORDITA, (3) University of Stockholm)Comments: 9 pages, 10 figures, accepted for publication in MNRASSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [56] arXiv:0908.2757 (replaced) [ps, pdf, other]
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Title: Tunneling and propagation of vacuum bubbles on dynamical backgroundsComments: 29 pages, 8 figures, typos corrected, matches published versionJournal-ref: JCAP 0911:008,2009Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
- [57] arXiv:0909.1317 (replaced) [ps, pdf, other]
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Title: The impact of a strongly first-order phase transition on the abundance of thermal relicsComments: 22 pages, 6 figures Included a discussion of the dilution in the MSSM in Sec IV C and slightly expanded the discussion of thermodynamics in Sec II, in addition to other minor changes. This version published in PRDJournal-ref: Phys. Rev. D 80, 103517 (2009)Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
- [58] arXiv:0909.4307 (replaced) [ps, pdf, other]
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Title: Precise mass and radius values for the white dwarf and low mass M dwarf in the pre-cataclysmic binary NN SerpentisAuthors: S. G. Parsons, T. R. Marsh, C. M. Copperwheat, V. S. Dhillon, S. P. Littlefair, B. T. Gansicke, R. HickmanComments: 20 pages, 17 figures, 8 tables, minor changes, accepted for publication in MNRASSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [59] arXiv:0909.5251 (replaced) [ps, pdf, other]
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Title: Entropy Perturbations in N-flationComments: References added, some typos corrected and figures adjusted. Accepted by Phys. Rev. DSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
- [60] arXiv:0910.3698 (replaced) [pdf, other]
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Title: Constraints on inelastic dark matter from XENON10Authors: XENON10 CollaborationComments: 8 pages, 4 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [61] arXiv:0911.1173 (replaced) [ps, pdf, other]
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Title: Implications of infalling Fe II - emitting clouds in active galactic nuclei: anisotropic propertiesAuthors: Gary J. Ferland, Chen Hu, Jian-Min Wang, Jack A. Baldwin, Ryan L. Porter, Peter A. M. van Hoof, R.J.R. WilliamsComments: 5 figures, Accepted for publication in ApJ (Letters)Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [62] arXiv:0911.2949 (replaced) [ps, pdf, other]
- [63] arXiv:0911.3198 (replaced) [ps, pdf, other]
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Title: Constraining the Dark Energy Equation of State using Alternative High-z Cosmic TracersComments: 10 pages, 5 figures, "Dark Universe" conference (Paris, July 2009)Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [64] arXiv:0911.3316 (replaced) [ps, pdf, other]
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Title: Companion stars of Type Ia supernovae and hypervelocity starsComments: 4 pages, 5 figures, accepted for publication in A&A LettersSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [65] arXiv:0911.3332 (replaced) [ps, pdf, other]
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Title: Quasar Outflow Contribution to AGN Feedback: Observations of QSO SDSS J0838+2955Comments: 28 pages, 7 figures, 4 tables, published in Astrophysical JournalJournal-ref: 2009 ApJ 706 525-534Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
- [66] arXiv:0911.3587 (replaced) [ps, pdf, other]
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Title: A Photometric Transit Search for Planets around Cool Stars from the Italian Alps: Results from a Feasibility StudyAuthors: M. Damasso, P. Calcidese, A. Bernagozzi, E. Bertolini, P. Giacobbe, M.G. Lattanzi, R. Smart, A. SozzettiComments: Two-page contribution to the International Conference "Pathways towards habitable planets" (included 2 eps figures, asp2006.sty, psfig.sty)Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
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