Astrophysics
New submissions
[ showing up to 2000 entries per page: fewer | more ]
New submissions for Mon, 23 Nov 09
- [1] arXiv:0911.3896 [ps, pdf, other]
-
Title: The Quasar Outflow Contribution to AGN Feedback: VLT Measurements of SDSS J0318-0600Authors: Jay P. Dunn, Manuel A. Bautista, Nahum Arav, Maxwell Moe, Kirk T. Korista, Elisa Costantini, Chris Benn, Sara Ellison, Doug EdmondsComments: Accepted for publication in ApJ, 57 pages, 14 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We present high spectral resolution VLT observations of the BAL quasar SDSS J0318-0600. This high quality data set allows us to extract accurate ionic column densities and determine an electron number density of n_e=10^3.3 +/- 0.2 cm^-3 for the main outflow absorption component. The heavily reddened spectrum of SDSS J0318-0600 requires purely silicate dust with a reddening curve characteristic of predominately large grains, from which we estimate the bolometric luminosity. We carry out photoionization modeling to determine the total column density, ionization parameter and distance of the gas and find that the photionization models suggest abundances greater than solar. Due to the uncertainty in the location of the dust extinction, we arrive at two viable distances for the main ouflow component from the central source, 6 and 18 kpc, where we consider the 6 kpc location as somewhat more physically plausable. Assuming the canonical global covering of 20% for the outflow and a distance of 6 kpc, our analysis yields a mass flux of 120 M_sun yr^-1 and a kinetic luminosity that is ~0.1% of the bolometric luminosity of the object. Should the dust be part of the outflow, then these values are ~4x larger. The large mass flux and kinetic luminosity make this outflow a significant contributor to AGN feedback processes.
- [2] arXiv:0911.3897 [ps, pdf, other]
-
Title: Neutral Gas Outflows and Inflows in Infrared-Faint Seyfert GalaxiesComments: 50 pages, 12 figures, accepted for publication in ApJSubjects: Galaxy Astrophysics (astro-ph.GA)
Previous studies of the Na I D interstellar absorption line doublet have shown that galactic winds occur in most galaxies with high infrared luminosities. However, in infrared-bright composite systems where a starburst coexists with an active galactic nucleus (AGN), it is unclear whether the starburst, the AGN, or both are driving the outflows. The present paper describes the results from a search for outflows in 35 infrared-faint Seyferts with 10^9.9 < L_IR/L_sun < 10^11, or, equivalently, star formation rates (SFR) of ~0.4 -- 9 solar masses per year, to attempt to isolate the source of the outflow. We find that the outflow detection rates for the infrared-faint Seyfert 1s (6%) and Seyfert 2s (18%) are lower than previously reported for infrared-luminous Seyfert 1s (50%) and Seyfert 2s (45%). The outflow kinematics of infrared-faint and infrared-bright Seyfert 2 galaxies resemble those of starburst galaxies, while the outflow velocities in Seyfert 1 galaxies are significantly larger. Taken together, these results suggest that the AGN does not play a significant role in driving the outflows in most infrared-faint and infrared-bright systems, except the high-velocity outflows seen in Seyfert 1 galaxies. Another striking result of this study is the high rate of detection of inflows in infrared-faint galaxies (39% of Seyfert 1s, 35% of Seyfert 2s), significantly larger than in infrared-luminous Seyferts (15%). This inflow may be contributing to the feeding of the AGN in these galaxies, and potentially provides more than enough material to power the observed nuclear activity over typical AGN lifetimes.
- [3] arXiv:0911.3900 [ps, pdf, other]
-
Title: Mapping the stellar structure of the Milky WayAuthors: Jelte T. A. de Jong (1), Brian Yanny (2), Hans-Walter Rix (1), Andrew E. Dolphin (3), Nicolas F. Martin (1), Timothy C. Beers (4) ((1) Max-Planck-Institut fuer Astronomie, (2) Fermi National Accelerator Laboratory, (3) Raytheon Company, (4) Michigan State University)Comments: 12 pages, 10 figures, submitted to Astrophysical JournalSubjects: Galaxy Astrophysics (astro-ph.GA)
We map the stellar structure of the Galaxy by applying color-magnitude diagram (CMD) fitting to photometric data from the SEGUE survey allowing, for the first time, a comprehensive analysis of Milky Way structure at both high and low latitudes using uniform SDSS photometry. The advantage of CMD fitting is that it incorporates photometry of all relevant stars simultaneously, bypassing the need to choose single tracer populations. Using three template stellar populations we obtain a sparse 3-D map of the stellar mass distribution. Fitting a smooth Milky Way model, comprised of exponential thin and thick disks and an axisymmetric power-law halo, allows us to constrain the structural parameters of the thick disk and halo. The thick disk scale height and length of such models are well constrained at 0.75+-0.07 kpc and 4.1+-0.4 kpc, respectively. We find a stellar halo flattening within ~25 kpc of c/a=0.88+-0.03 and a power-law index of 2.75+-0.07. The model fits yield densities at the solar location of rho_{thick,0}=10^{-2.3+-0.1} M_\sun pc^{-3} and rho_{halo,0}=10^{-4.20+-0.05} M_\sun pc^{-3}. We detect in-situ evidence for a metallicity gradient in the stellar halo: within R<~15 kpc the stellar halo has a mean metallicity of [Fe/H]=-1.6, which shifts to [Fe/H]=-2.2 at larger radii. Subtraction of the best-fit smooth and symmetric model from the density maps reveals a wealth of substructures at all latitudes, some attributable to known streams and overdensities, and some new. A simple warp cannot account for the low latitude substructure, as overdensities occur simultaneously above and below the Galactic plane. (abridged)
- [4] arXiv:0911.3901 [ps, pdf, other]
-
Title: GRB 090313: X-shooter's first shot at a GRBAuthors: A. de Ugarte Postigo, V. D'Elia, P. Goldoni, C.C. Thöne, S. Piranomonte, S.D. Vergani, D. Malesani, S. Covino, H. Flores, J.P.U. Fynbo, J. Hjorth, R.A.M.J. Wijers, S. D'Odorico, F. Hammer, L. Kaper, P. Kjærgaard, S. Randich, M.I. Andersen, L.A. Antonelli, L. Christensen, P. D'Avanzo, F. Fiore, P.J. Groot, E. Maiorano, E. Palazzi, E. Pian, G. Tagliaferri, M.E. van den Ancker, J. Vernet, P.M. VreeswijkComments: Submitted to Astronomy and Astrophysics on the 12 August. Version includes referee comments. 8 pages, 5 figures, 4 tablesSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Context. X-shooter is the first second-generation instrument of ESO's Very Large Telescope (VLT), a spectrograph designed with gamma-ray burst (GRB) afterglow spectroscopy as one of its main scientific drivers.
Aims. During the first commissioning night on sky with the instrument fully assembled, X-shooter observed the afterglow of GRB 090313 as a demonstration of the instrument's capabilities.
Methods. GRB 090313 was observed almost two days after the burst onset, when the object had already faded to R~21.6. Furthermore, the 90% illuminated Moon was just 30 degrees away from the field. In spite of the adverse conditions, we obtained a spectrum that for the first time in GRB research, covers simultaneously the range from 5,700 to 23,000 Angstroms.
Results. The spectrum shows multiple absorption features at a redshift of 3.3736, which we identify as the redshift of the GRB. These features are composed of 3 components with different ionisation levels and velocities. Some of the features have never been observed before in a GRB at such a high redshift. Furthermore, we detect two intervening systems at redshifts of 1.8005 and 1.9597.
Conclusions. These results demonstrate the potential of X-shooter in the GRB field, as it was capable of observing a GRB down to a magnitude limit that would include 75% of all GRB afterglows 2 hours after the burst onset. Coupled with the rapid response mode available at VLT, that allows reaction times of just a few minutes, it implies an important leap forward on medium resolution spectroscopic studies of GRBs. - [5] arXiv:0911.3902 [ps, pdf, other]
-
Title: Impact of string and monopole-type junctions on domain wall dynamics: implications for dark energyComments: 4 pages, 1 figureSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We investigate the potential role of string and monopole-type junctions in the frustration of domain wall networks using a velocity-dependent one-scale model for the characteristic velocity, $v$, and the characteristic length, $L$, of the network. We show that, except for very special network configurations, $v^2 \lsim (HL)^2 \lsim (\rho_\sigma + \rho_\mu)/\rho_m$ where $H$ is the Hubble parameter and $\rho_\sigma$, $\rho_\mu$ and $\rho_m$ are the average density of domain walls, strings and monopole-type junctions. We further show that if domain walls are to provide a significant contribution to the dark energy without generating exceedingly large CMB temperature fluctuations then, at the present time, the network must have a characteristic length $ L_0 \lsim 10 \Omega_{\sigma 0}^{-2/3} {\rm kpc}$ and a characteristic velocity $v_0 \lsim 10^{-5} \Omega_{\sigma 0}^{-2/3}$ where $\Omega_{\sigma 0}=\rho_{\sigma 0}/\rho_{c 0}$ and $\rho_c$ is the critical density. In order to satisfy these constraints with $\Omega_{\sigma 0} \sim 1$, $\rho_{m 0}$ would have to be at least 10 orders of magnitude larger than $\rho_{\sigma 0}$, which would be in complete disagreement with observations. This result provides very strong additional support for the conjecture that no natural frustration mechanism, which could lead to a significant contribution of domain walls to the dark energy budget, exists.
- [6] arXiv:0911.3904 [ps, pdf, other]
-
Title: Booms and Busts: the Burstiness of Star Formation in Nearby Dwarf GalaxiesAuthors: Andrew A. Cole (University of Tasmania)Comments: Accepted by the Publications of the Astronomical Society of Australia (PASA). Summary of a review talk given at the Southern Cross Astrophysics Conference on "Galaxy Metabolism" held in Sydney, 22-26 June 2009. 9 pages, 2 figuresSubjects: Galaxy Astrophysics (astro-ph.GA)
In this review I summarise recent advances in our understanding of the importance of starburst events to the evolutionary histories of nearby galaxies. Ongoing bursts are easily diagnosed in emission-line surveys, but assessing the timing and intensity of fossil bursts requires more effort, usually demanding color-magnitude diagrams or spectroscopy of individual stars. For ages older than ~1 Gyr, this type of observation is currently limited to the Local Group and its immediate surroundings. However, if the Local Volume is representative of the Universe as a whole, then studies of the age and metallicity distributions of star clusters and resolved stellar populations should give statistical clues as to the frequency and importance of bursts to the histories of galaxies in general. Based on starburst statistics in the literature and synthetic colour-magnitude diagram studies of Local Group galaxies, I attempt to distinguish between systemic starbursts that strongly impact galaxy evolution and stochastic bursts that can appear impressive but are ultimately of little significance on gigayear timescales. As a specific case, it appears as though IC 10, the only starburst galaxy in the Local Group, falls into the latter category and is not fundamentally different from other nearby dwarf irregular galaxies.
- [7] arXiv:0911.3905 [ps, pdf, other]
-
Title: Non-parametric modeling of the intra-cluster gas using APEX-SZ bolometer imaging dataAuthors: K. Basu, Y.-Y. Zhang, M.W. Sommer, A.N. Bender, F. Bertoldi, M. Dobbs, H. Eckmiller, N.W. Halverson, W.L. Holzapfel, C. Horellou, V. Jaritz, D. Johansson, B. Johnson, J. Kennedy, R. Kneissl, T. Lanting, A.T. Lee, J. Mehl, K.M. Menten, F.P. Navarrete, F. Pacaud, C.L. Reichardt, T.H. Reiprich, P.L. Richards, D. Schwan, B. WestbroockComments: Submitted to Astronomy and Astrophysics; 14 pages, 13 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We demonstrate the usability of mm-wavelength imaging data obtained from the APEX-SZ bolometer array to derive the radial temperature profile of the hot intra-cluster gas out to radius r_500 and beyond. The goal is to study the physical properties of the intra-cluster gas by using a non-parametric de-projection method that is, aside from the assumption of spherical symmetry, free from modeling bias. We use publicly available X-ray imaging data from the XMM-Newton observatory and our Sunyaev-Zel'dovich Effect (SZE) imaging data from the APEX-SZ experiment at 150 GHz to de-project the density and temperature profiles for the relaxed cluster Abell 2204. We derive the gas density, temperature and entropy profiles assuming spherical symmetry, and obtain the total mass profile under the assumption of hydrostatic equilibrium. For comparison with X-ray spectroscopic temperature models, a re-analysis of the recent Chandra observation is done with the latest calibration updates. Using the non-parametric modeling we demonstrate a decrease of gas temperature in the cluster outskirts, and also measure the gas entropy profile. These results are obtained for the first time independently of X-ray spectroscopy, using SZE and X-ray imaging data. The contribution of the SZE systematic uncertainties in measuring T_e at large radii is shown to be small compared to the Chandra systematic spectroscopic errors. The upper limit on M_200 derived from the non-parametric modeling is consistent with the NFW model prediction from weak lensing analysis. (Abridged)
- [8] arXiv:0911.3909 [ps, pdf, other]
-
Title: Understanding the Geometry of Astrophysical Magnetic FieldsComments: 13 pages, 5 figures, submitted to ApJSubjects: Galaxy Astrophysics (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
Faraday rotation measurements have provided an invaluable technique with which to measure the properties of astrophysical magnetized plasmas. Unfortunately, typical observations provide information only about the density-weighted average of the magnetic field component parallel to the line of sight. As a result, the magnetic field geometry along the line of sight, and in many cases even the location of the rotating material, is poorly constrained. Frequently, interpretations of Faraday rotation observations are dependent upon underlying models of the magnetic field being probed (e.g., uniform, turbulent, equipartition). However, we show that at sufficiently low frequencies, specifically below roughly 13 (RM/rad m^-2)^(1/4) (B/G)^(1/2) MHz, the character of Faraday rotation changes, entering what we term the ``super-adiabatic regime'' in which the rotation measure is proportional to the integrated absolute value of the line-of-sight component of the field. As a consequence, comparing rotation measures at high frequencies with those in this new regime provides direct information about the geometry of the magnetic field along the line of sight. Furthermore, the frequency defining the transition to this new regime, nu_SA, depends directly upon the local electron density and magnetic field strength where the magnetic field is perpendicular to the line of sight, allowing the unambiguous distinction between Faraday rotation within and in front of the emission region. Typical values of nu_SA range from 10 kHz to 10 GHz, depending upon the details of the Faraday rotating environment. In particular, for resolved AGN, including the black holes at the center of the Milky Way (Sgr A*) and M81, nu_SA ranges from roughly 10 MHz to 10 GHz, and thus can be probed via existing and up-coming ground-based radio observatories.
- [9] arXiv:0911.3911 [ps, pdf, other]
-
Title: Identifying the Obscured Black-Hole Growth Phase of Distant Massive GalaxiesAuthors: D.M. Alexander (Durham)Comments: 8 pages, 2 figures. Contribution to the "Galaxy Evolution: Emerging Insights and Future Challenges", conference in Austin, Texas on November 11-14, 2008Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
It is well established that a dominant phase in the growth of massive galaxies occurred at high redshift and was heavily obscured by gas and dust. Many studies have explored the stellar growth of massive galaxies but few have combined these constraints with the growth of the supermassive black hole (SMBH; i.e., identified as AGN activity). In this brief contribution we highlight our work aimed at identifying AGNs in z~2 luminous dust-obscured galaxies. Using both sensitive X-ray and infrared (IR)-submillimeter (submm) observations, we show that AGN activity is common in z~2 dust-obscured systems. With a variety of techniques we have found that the majority of the AGN activity is heavily obscured, and construct diagnostics based on X-ray-IR data to identify some of the most heavily obscured AGNs in the Universe (i.e., AGNs obscured by Compton-thick material; N_H>1.5x10^24 cm^-2). On the basis of these techniques we show that SMBH growth was typically heavily obscured (N_H>10^23 cm^-2) at z~2, and find that the growth of the SMBH and spheroid was closely connected, even in the most rapidly evolving systems.
- [10] arXiv:0911.3914 [ps, pdf, other]
-
Title: The [OIII] emission line luminosity function of optically selected type-2 AGN from zCOSMOSAuthors: A. Bongiorno, M. Mignoli, G. Zamorani, F. Lamareille, G. Lanzuisi, T. Miyaji, M. Bolzonella, C. M. Carollo, T. Contini, J. P. Kneib, O. Le Fevre, S. J. Lilly, V. Mainieri, A. Renzini, M. Scodeggio, S. Bardelli, M. Brusa, K. Caputi, F. Civano, G. Coppa, O. Cucciati, S. de la Torre, L. de Ravel, P. Franzetti, B. Garilli, C. Halliday, G. Hasinger, A. M. Koekemoer, A. Iovino, P. Kampczyk, C. Knobel, K. Kovac, J.-F. Le Borgne, V. Le Brun, C. Maier, A. Merloni, P. Nair, R. Pello, Y. Peng, E. Perez Montero, E. Ricciardelli, M. Salvato, J. Silverman, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, E. Zucca, U. Abbas, D. Bottini, A. Cappi, P. Cassata, A. Cimatti, L. Guzzo, A. Leauthaud, D. Maccagni, C. Marinoni, H. J. McCracken, P. Memeo, B. Meneux, P. Oesch, C. Porciani, L. Pozzetti, R. ScaramellaComments: 20 pages, 11 figures, accepted for publication in Astronomy and AstrophysicsSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We present a catalog of 213 type-2 AGN selected from the zCOSMOS survey. The selected sample covers a wide redshift range (0.15<z<0.92) and is deeper than any other previous study, encompassing the luminosity range 10^{5.5} < Lsun< L[OIII] < 10^{9.1} Lsun. We explore the intrinsic properties of these AGN and the relation to their X-ray emission (derived from the XMM-COSMOS observations). We study their evolution by computing the [OIII]5007A line luminosity function (LF) and we constrain the fraction of obscured AGN as a function of luminosity and redshift. The sample was selected on the basis of the optical emission line ratios, after applying a cut to the signal-to-noise ratio (S/N) of the relevant lines. We used the standard diagnostic diagrams [OIII]/Hbeta versus [NII]/Halpha and ([OIII]/Hbeta versus [SII]/Halpha) to isolate AGN in the redshift range 0.15<z<0.45 and the diagnostic diagram [OIII]/Hbeta versus [OII]/Hbeta to extend the selection to higher redshift (0.5<z<0.92). Combining our sample with one drawn from SDSS, we found that the best description of the evolution of type-2 AGN is a luminosity-dependent density evolution model. Moreover, using the type-1 AGN LF we were able to constrain the fraction of type-2 AGN to the total (type-1 + type-2) AGN population. We found that the type-2 fraction decreases with luminosity, in agreement with the most recent results, and shows signs of a slight increase with redshift. However, the trend with luminosity is visible only after combining the SDSS+zCOSMOS samples. From the COSMOS data points alone, the type-2 fraction seems to be quite constant with luminosity.
- [11] arXiv:0911.3922 [ps, pdf, other]
-
Title: The Initial Conditions of Clustered Star Formation. II. N2H+ Observations of the Ophiuchus B CoreComments: 55 pages (manuscript), 15 figures, ApJ acceptedSubjects: Galaxy Astrophysics (astro-ph.GA)
We present a Nobeyama 45 m Radio Telescope map and Australia Telescope Compact Array pointed observations of N2H+ 1-0 emission towards the clustered, low mass star forming Oph B Core within the Ophiuchus molecular cloud. We compare these data with previously published results of high resolution NH3 (1,1) and (2,2) observations in Oph B. We use 3D Clumpfind to identify emission features in the single-dish N2H+ map, and find that the N2H+ `clumps' match well similar features previously identified in NH3 (1,1) emission, but are frequently offset to clumps identified at similar resolution in 850 micron continuum emission. Wide line widths in the Oph B2 sub-Core indicate non-thermal motions dominate the Core kinematics, and remain transonic at densities n ~ 3 x 10^5 cm^-3 with large scatter and no trend with N(H2). Non-thermal motions in Oph B1 and B3 are subsonic with little variation, but also show no trend with H2 column density. Over all Oph B, non-thermal N2H+ line widths are substantially narrower than those traced by NH3, making it unlikely NH3 and N2H+ trace the same material, but the v_LSR of both species agree well. We find evidence for accretion in Oph B1 from the surrounding ambient gas. The NH3/N2H+ abundance ratio is larger towards starless Oph B1 than towards protostellar Oph B2, similar to recent observational results in other star-forming regions. Small-scale structure is found in the ATCA N2H+ 1-0 emission, where emission peaks are again offset from continuum emission. In particular, the ~1 M_Sun B2-MM8 clump is associated with a N2H+ emission minimum and surrounded by a broken ring-like N2H+ emission structure, suggestive of N2H+ depletion. We find a strong general trend of decreasing N2H+ abundance with increasing N(H2) in Oph B which matches that found for NH3.
- [12] arXiv:0911.3928 [ps, pdf, other]
-
Title: Evolution of AGN Space Densities and the FR DichotomyComments: IAU Symposium 267 Proceeding - 1 pageSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We focus on a comparison of the space densities of FRI and FRII extended radio sources at different epochs, and find that FRI and FRII sources show similar space density enhancements in various redshift ranges, possibly implying a common evolution.
- [13] arXiv:0911.3937 [ps, pdf, other]
-
Title: Fragment properties at the catastrophic disruption threshold: The effect of the parent body's internal structureComments: 18 pages, 19 Figures. Accepted for publication in IcarusSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
Numerical simulations of asteroid break-ups, including both the fragmentation of the parent body and the gravitational interactions between the fragments, have allowed us to reproduce successfully the main properties of asteroid families formed in different regimes of impact energy, starting from a non-porous parent body. In this paper, using the same approach, we concentrate on a single regime of impact energy, the so-called catastrophic threshold usually designated by Q*D, which results in the escape of half of the target's mass. Thanks to our recent implementation of a model of fragmentation of porous materials, we can characterize Q*D for both porous and non-porous targets with a wide range of diameters. We can then analyze the potential influence of porosity on the value of Q*D, and by computing the gravitational phase of the collision in the gravity regime, we can characterize the collisional outcome in terms of the fragment size and ejection speed distributions, which are the main outcome properties used by collisional models to study the evolutions of the different populations of small bodies. We also check the dependency of Q*D on the impact speed of the projectile. In the strength regime, which corresponds to target sizes below a few hundreds of meters, we find that porous targets are more difficult to disrupt than non-porous ones. In the gravity regime, the outcome is controlled purely by gravity and porosity in the case of porous targets. In the case of non-porous targets, the outcome also depends on strength. We then propose some power-law relationships between Q*D and both target's size and impact speed that can be used in collisional evolution models.
- [14] arXiv:0911.3942 [ps, pdf, other]
-
Title: Correcting for the ionosphere in the uv-planeComments: 20 pages, 19 figures and tablesSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Extragalactic Astrophysics (astro-ph.CO)
In radio astronomy, the correlator measures intensity in visibility space. In addition, the EoR power spectrum measured by an experiment such as the MWA is constructed in visibility space. Thus, correcting for the ionosphere in the uv-plane instead of real space could potentially save computation. In this paper, we study this technique. The mathematical formula for obtaining the unperturbed data from the ionospherically reflected data is non-local in the uv-plane. Moreover, an analytic solution for the unperturbed intensity may only be obtained for a limited number of expansions of the ionospheric perturbations. We numerically study one of these expansions (with perturbations as sinusoidal modes). Obtaining an analytic solution for this expansion required a Taylor expansion, and we investigate the optimal order of this expansion. We also propose a number of potential computation saving techniques, and evaluate their pros and cons.
- [15] arXiv:0911.3965 [ps, pdf, other]
-
Title: Introduction to nuclear astrophysicsAuthors: Christian IliadisComments: Proceedings of the 5th European Summer School on Experimental Nuclear Astrophysics, Santa Tecla, Italy, 2009, 20 pages, 4 figures, 1 tableSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
In the first lecture of this volume, we will present the basic fundamental ideas regarding nuclear processes occurring in stars. We start from stellar observations, will then elaborate on some important quantum-mechanical phenomena governing nuclear reactions, continue with how nuclear reactions proceed in a hot stellar plasma and, finally, we will provide an overview of stellar burning stages. At the end, the current knowledge regarding the origin of the elements is briefly summarized. This lecture is directed towards the student of nuclear astrophysics. Our intention is to present seemingly unrelated phenomena of nuclear physics and astrophysics in a coherent framework.
- [16] arXiv:0911.3966 [ps, pdf, other]
-
Title: Non-axisymmetric low frequency oscillations of rotating and magnetized neutron starsAuthors: Umin LeeComments: 15pages, 7 figuresSubjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)
We investigate non-axisymmetric low frequency modes of a rotating and magnetized neutron star, assuming that the star is threaded by a dipole magnetic field whose strength at the stellar surface, $B_0$, is less than $\sim 10^{12}$G, and whose magnetic axis is aligned with the rotation axis. For modal analysis, we use a neutron star model composed of a fluid ocean, a solid crust, and a fluid core, where we treat the core as being non-magnetic assuming that the magnetic pressure is much smaller than the gas pressure in the core. Here, we are interested in low frequency modes of a rotating and magnetized neutron star whose oscillation frequencies are similar to those of toroidal crust modes of low spherical harmonic degree and low radial order. For a magnetic field of $B_0\sim 10^7$G, we find Alfv\'en waves in the ocean have similar frequencies to the toroidal crust modes, and we find no $r$-modes confined in the ocean for this strength of the field. We calculate the toroidal crustal modes, the interfacial modes peaking at the crust/core interface, and the core inertial modes and $r$-modes, and all these modes are found to be insensitive to the magnetic field of strength $B_0\ltsim10^{12}$G. We find the displacement vector of the core $l^\prime=|m|$ $r$-modes have large amplitudes around the rotation axis at the stellar surface even in the presence of a surface magnetic field $B_0\sim10^{10}$G, where $l^\prime$ and $m$ are the spherical harmonic degree and the azimuthal wave number of the $r$-modes, respectively. We suggest that millisecond X-ray variations of accretion powered X-ray millisecond pulsars can be used as a probe into the core $r$-modes destabilized by gravitational wave radiation.
- [17] arXiv:0911.3968 [ps, pdf, other]
-
Title: The pasta structure in the hadron-quark phase transition and the effects on magnetized compact starsComments: 7 pages, 3 figures, Compact stars in the QCD phase diagram IISubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
We report the effects of quark-hadron phase transition on the structures of general relativistic stars with purely toroidal magnetic field. For the mixed phase, we take into account of the finite-size effects, which lead to non-uniform "Pasta" structures. Our study is based on axisymetric and stationary formalism including purely toroidal magnetic field. For hybrid stars, we find the characteristic distribution of magnetic field, which has a discontinuity originated in the quark-hadron mixed phase. These distributions of magnetic field will change astrophysical phenomena, such as cooling processes.
- [18] arXiv:0911.3974 [ps, pdf, other]
-
Title: Studies of Expolanets and Solar Systems with SPICAAuthors: Michihiro Takami (1), Motohide Tamura (2), Keigo Enya (3), Takafumi Ootsubo (3), Misato Fukagawa (4), Mitsuhiko Honda (5), Yoshiko Okamoto (6), Shigehisa Sako (7), Takuya Yamashita (2), Sunao Hasegawa (3), Hirokazu Kataza (3), Hideo Matsuhara (3), Takao Nakagawa (3), Javier R. Goicoechea (8), Kate Isaak (9), Bruce Swinyard (10) ((1) Institute of Astronomy and Astrophysics, Academia Sinica, (2) National Astronomical Observatory of Japan, (3) Japan Aerospace Exploration Agency, (4) Osaka University, (5) Kanagawa University, (6) Ibaraki University, (7) University of Tokyo, (8) Centro de Astrobiologia (CSIC-INTA), (9) Cardiff University, (10) Rutherford Appleton Laboratory)Comments: 17 pages, 4 figures, 1 table, accepted for Advances in Space Research (conference proceeding of 37th COSPAR Scientific Assembly)Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
The SPace Infrared telescope for Cosmology and Astrophysics (SPICA) is a proposed mid-to-far infrared (4-200 um) astronomy mission, scheduled for launch in 2017. A single, 3.5m aperture telescope would provide superior image quality at 5-200 um, and its very cold (~5 K) instrumentation would provide superior sensitivity in the 25-200 um wavelength regimes. This would provide a breakthrough opportunity for studies of exoplanets, protoplanetary and debris disk, and small solar system bodies. This paper summarizes the potential scientific impacts for the proposed instrumentation.
- [19] arXiv:0911.3976 [pdf]
-
Title: Testing SETI Message DesignsComments: The first 8 pages of the document contain the abstract, paper, and references. The remainder is supplementary materialSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Popular Physics (physics.pop-ph)
Much work in SETI has focused on detecting radio broadcasts due to extraterrestrial intelligence, but there have been limited efforts to transmit messages over interstellar distances. As a check if such messages can be interpreted once received, we conducted a blind test. One of us coded a 75-kilobit message, which the other then attempted to decipher. The decryption was accurate, supporting the message design as a general structure for communicating with aliens capable of detecting narrow-band radio transmissions.
- [20] arXiv:0911.3994 [ps, pdf, other]
-
Title: Is Non-minimal Inflation Eternal?Comments: 9 pages, 2 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
The possibility that the non-minimal coupling inflation could be eternal is investigated. We calculate the quantum fluctuation of the inflaton in a Hubble time and find that it has the same value as in the minimal case in the slow-roll limit. Armed with this result, we have studied some concrete non-minimal inflationary models including the chaotic inflation and the natural inflation while the inflaton is non-minimally coupled to the gravity and we find that these non-minimal inflations could be eternal in some parameter regions.
- [21] arXiv:0911.4002 [ps, pdf, other]
-
Title: Towards a long-term record of solar total and spectral irradianceSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
The variation of total solar irradiance (TSI) has been measured since 1978 and that of the spectral irradiance for an even shorter amount of time. Semi-empirical models are now available that reproduce over 80% of the measured irradiance variations. An extension of these models into the more distant past is needed in order to serve as input to climate simulations. Here we review our most recent efforts to model solar total and spectral irradiance on time scales from days to centuries and even longer. Solar spectral irradiance has been reconstructed since 1947. Reconstruction of solar total irradiance goes back to 1610 and suggests a value of about 1-1.5 Wm$^{-2}$ for the increase in the cycle-averaged TSI since the end of the Maunder minimum, which is significantly lower than previously assumed but agrees with other modern models. First steps have also been made towards reconstructions of solar total and spectral irradiance on time scales of millennia.
- [22] arXiv:0911.4004 [pdf, other]
-
Title: Cosmic Ray Acceleration in Active Galactic Nuclei - On Centaurus A as a possible UHECR SourceAuthors: Frank M. RiegerComments: 8 pages, one figure; based on invited talk at the JEM-EUSO Workshop, Torino/Italy, December 2008. To appear in Proceedings of the JEM-EUSO Workshop, under publication by UAP Tokyo, JapanSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
We discuss a representative selection of particle acceleration mechanisms believed to be operating in Active Galactic Nuclei. Starting from direct electrostatic field acceleration in the vicinity of the black hole up to Fermi-type particle acceleration in the jet and beyond, possible efficiency constraints on the energization of ultra-high energy cosmic rays (UHECR) are evaluated. When paradigmatically applied to Cen A, the following results are obtained: (i) Proton acceleration to energies of $E_c = 5\times 10^{19}$ eV and beyond remains challenging and most likely requires the operation of an additional mechanism capable of boosting energetic seed protons up by a factor of $\sim$ten. It is argued that shear acceleration along the large-scale jet in Cen A could be a promising candidate for this. (ii) Heavier elements, like iron nuclei, are more easily accelerated (by, e.g., shocks or direct electrostatic fields) and may not need additional boosting to reach $E \geq E_c$; (iii) If Cen A indeed proves to be an UHECR source, the cosmic ray composition might thus be expected to become heavier above energies of a few times $10^{19}$ eV.
- [23] arXiv:0911.4012 [pdf, other]
-
Title: Magnetic fields in nearby galaxiesComments: In proceedings of "Panoramic Radio Astronomy" conference held 2-5 June 2009, Groningen, the Netherlands. 6 pages, 2 figuresSubjects: Galaxy Astrophysics (astro-ph.GA)
We describe a recent full-polarization radio continuum survey, performed using the Westerbork Synthesis Radio Telescope (WSRT), of several nearby galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The WSRT-SINGS survey has been utilized to study the polarized emission and Faraday rotation measures (RMs) in the targets, and reveals an important new observational trend. The azimuthal distribution of polarized flux seems to be intimately related to the kinematic orientation of galaxies, such that in face-on galaxies the lowest level of polarized flux is detected along the kinematic major axis. In highly inclined galaxies, the polarized flux is minimized on both ends of the major axis, and peaks near the minor axis. Using models of various three-dimensional magnetic field geometries, and including the effects of turbulent depolarization in the midplane, we are able to reproduce the qualitative distribution of polarized flux in the target galaxies, its variation with inclination, and the distribution of RMs, thereby constraining the global magnetic field structure in galaxies. Future radio telescope facilities, now being planned and constructed, will have properties making them extremely well-suited to perform vastly larger surveys of this type, and are thereby poised to significantly increase our understanding of the global structure of galactic magnetic fields. We discuss progress that can be made using surveys which will be realized with these new facilities, focusing in particular on the Aperture Tile in Focus (APERTIF) and Australian Square Kilometre Array Pathfinder (ASKAP) telescopes, both based on Focal Plane Array (FPA) designs, which are expected to be particularly useful for wide-field polarization applications.
- [24] arXiv:0911.4018 [pdf, other]
-
Title: Panoramic Radio AstronomyComments: Overview contribution for proceedings of "Panoramic Radio Astronomy", held 2-5 June 2009, Groningen, the Netherlands. The proceedings are available online at this http URLSubjects: Galaxy Astrophysics (astro-ph.GA)
In this contribution we give a brief overview of the Panoramic Radio Astronomy (PRA) conference held on 2-5 June 2009 in Groningen, the Netherlands. The conference was motivated by the on-going development of a large number of new radio telescopes and instruments which, within a few years, will bring a major improvement over current facilities. Interferometers such as the EVLA, ASKAP, ATA, MeerKAT, and APERTIF will provide a combination of larger field of view and increased simultaneous bandwidth, while maintaining good collecting area and angular resolution. They will achieve a survey speed 10-50 times larger at 1-2 GHz than the current possibilities, allowing for the first time optical-like all-sky extra-galactic surveys at these frequencies.
Significant progress will be made in many fields of radio astronomy. In this conference we focused on research into the evolution of galaxies over the past few Gyr. In particular, wide-field observations at 1-2 GHz will provide an unprecedented panoramic view of the gas properties and star formation in galaxies, embedded in their environment, from z~0.2-0.5 to the present. Within the framework of our current knowledge of the galaxy population at z<0.5, we discussed: the key science questions that the new telescopes will permit us to answer in combination with complimentary work at other wavelengths; the observing modes and analysis strategies which will allow us to most efficiently exploit the data; and the techniques for most effectively coping with the huge volume of survey products, so far unusual for the radio community. Emphasis was placed on the complementarity of the upcoming facilities and on their role in paving the way for the technological development and science goals of the Square Kilometre Array. - [25] arXiv:0911.4019 [ps, pdf, other]
-
Title: The chemical composition of TS 01, the most oxygen-deficient planetary nebula. AGB nucleosynthesis in a metal-poor binary starAuthors: G. Stasinska, C. Morisset, G. Tovmassian, T. Rauch, M. G. Richer, M. Pena, R. Szczerba, T. Decressin, C. Charbonnel, L. Yungelson, R. Napiwotzki, S. Simon-Diaz, L. JametComments: to appear in Astronomy and AstrophysicsSubjects: Galaxy Astrophysics (astro-ph.GA)
The planetary nebula TS 01 (also called PN G 135.9+55.9 or SBS 1150+599A), with its record-holding low oxygen abundance and its double degenerate close binary core (period 3.9 h), is an exceptional object located in the Galactic halo. We have secured observational data in a complete wavelength range in order to pin down the abundances of half a dozen elements in the nebula. The abundances are obtained via detailed photoionization modelling taking into account all the observational constraints (including geometry and aperture effects) using the pseudo-3D photoionization code Cloudy_3D. The spectral energy distribution of the ionizing radiation is taken from appropriate model atmospheres. Both stellar components contribute to the ionization: the ``cool'' one provides the bulk of hydrogen ionization, and the ``hot'' one is responsible for the presence of the most highly charged ions, which explains why previous attempts to model the nebula experienced difficulties. The nebular abundances of C, N, O, and Ne are found to be respectively, 1/3.5, 1/4.2, 1/70, and 1/11 of the Solar value, with uncertainties of a factor 2. Thus the extreme O deficiency of this object is confirmed. The abundances of S and Ar are less than 1/30 of Solar. Standard models of stellar evolution and nucleosynthesis cannot explain the abundance pattern observed in the nebula. To obtain an extreme oxygen deficiency in a star whose progenitor has an initial mass of about 1 msun requires an additional mixing process, which can be induced by stellar rotation and/or by the presence of the close companion. We have computed a stellar model with initial mass of 1 msun, appropriate metallicity, and initial rotation of 100 kms, and find that rotation greatly improves the agreement between the predicted and observed abundances.
- [26] arXiv:0911.4036 [ps, pdf, other]
-
Title: Mechanism of very high energy radiation in BL Lacertae object 3C 66AComments: 5 pages, 3 figures. accepted for publication in A&ASubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Our goal is to understand the nature of blazars and the mechanisms for the generation of high-energy $\gamma$-rays, through the investigation of the blazar 3C 66A. We model the high energy spectrum of 3C 66A, which has been observed recently with the Fermi-LAT and VERITAS telescope. The spectrum has a hard change from the energy range of 0.2-100 GeV to 200-500 GeV in recent almost contemporaneous observations of two telescopes. The de-absorbed VERITAS spectrum greatly depends on the redshift, which is highly uncertain. If z=0.444 is adopted, we are able to use the SSC model to produce the Fermi-LAT component and the EC model to the VERITAS component. However, if z=0.1, the intrinsic VERITAS spectrum will be softer, there will be a smooth link between the Fermi-LAT and VERITAS spectra which can be explained using a SSC model.
- [27] arXiv:0911.4052 [ps, pdf, other]
-
Title: The properties of the stellar populations in ULIRGs II: the star formation histories and evolutionComments: Accepted for publication in MNRAS. The paper contains 16 pages, 6 figures and 7 tablesSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
This is the second of two papers presenting a detailed long-slit spectroscopic study of the stellar populations in a sample of 36 ULIRGs. In the previous paper we presented the sample, the data and the spectral synthesis modelling while in this paper, we carry out a detailed analysis of the modelling results. We find that the star formation histories of ULIRGs are complex, with at least two epochs of star formation activity and that the charcteristic timescale of the star formation acivity is <100Myr. These results are consistent with models that predict an epoch of enhanced star formation coinciding with the first pass of the merging nuclei, along with a further, more intense, episode of star formation occurring as the nuclei finally merge together. It is also found that the young stellar populations (YSPs) tend to be younger and more reddened in the nuclear regions of the galaxies. This is in good agreement with the merger simulations, which predict that the bulk of the star formation activity in the final stages of mergers will occur in the nuclear regions of the merging galaxies. In addition, our results show that ULIRGs have total stellar masses that are similar to, or smaller than, the break of the galaxy mass function (m* = 1.4 x 10^{11} Msolar). Finally, we find no significant differences between the ages of the YSP in ULIRGs with and without optically detected Seyfert nuclei, nor between those with warm and cool mid- to far-IR colours. While this results do not entirely rule out the idea that cool ULIRGs with HII/LINER spectra evolve into warm ULIRGs with Seyfert-like spectra, it is clear that the AGN activity in local Seyfert-like ULIRGs has not been triggered a substantial period (>=100 Myr) after the major merger-induced starbursts in the nuclear regions.
- [28] arXiv:0911.4063 [ps, pdf, other]
-
Title: New evidence for lack of CMB power on large scalesComments: 9 pages, 3 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum is derived. The amplitudes of the low multipoles measured from the preliminary Planck power spectrum are significantly lower than that reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.
- [29] arXiv:0911.4072 [ps, pdf, other]
-
Title: Three intermediate-mass YSOs with different properties emerging from the same natal cloud in IRAS 00117+6412Authors: Aina Palau, A. Sanchez-Monge, G. Busquet, R. Estalella, Q. Zhang, P. T. P. Ho, M. T. Beltran, H. BeutherComments: accepted to Astronomy and AstrophysicsSubjects: Galaxy Astrophysics (astro-ph.GA)
We observed with the VLA, PdBI, and SMA the centimeter and millimeter continuum, N2H+(1-0), and CO(2-1) emission associated with a dusty cloud harboring a nascent cluster with intermediate-mass protostars. At centimeter wavelengths we found a strong source, tracing a UCHII region, at the eastern edge of the dusty cloud, with a shell-like structure, and with the near-infrared counterpart falling in the center of the shell. This is presumably the most massive source of the forming cluster. About 15'' to the west of the UCHII region and well embedded in the dusty cloud, we detected a strong millimeter source, MM1, associated with centimeter and near-infrared emission. MM1 seems to be driving a prominent high-velocity CO bipolar outflow, and is embedded in a ridge of dense gas traced by N2H+. We estimated that MM1 is an intermediate-mass source in the Class 0/I phase. About 15'' to the south of MM1, and still more deeply embedded in the dusty cloud, we detected a compact millimeter source, MM2, with neither centimeter nor near-infrared emission, but with water maser emission. MM2 is associated with a clump of N2H+, whose kinematics reveal a clear velocity gradient and additionally we found signposts of infall motions. MM2, being deeply embedded within the dusty cloud, with an associated water maser but no hints of CO outflow emission, is an intriguing object, presumably of intermediate mass. In conclusion, the UCHII region is found at the border of a dusty cloud which is currently undergoing active star formation. Two intermediate-mass protostars in the dusty cloud seem to have formed after the UCHII region and have different properties related to the outflow phenomenon.
- [30] arXiv:0911.4085 [ps, pdf, other]
-
Title: Coronal emission lines as thermometersAuthors: Philip G JudgeComments: Accepted by ApJ, November 2009Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Coronal emission line intensities are commonly used to measure electron temperatures using emission measure and/or line ratio methods. In the presence of systematic errors in atomic excitation calculations and data noise, the information on underlying temperature distributions is fundamentally limited. Increasing the number of emission lines used does not necessarily improve the ability to discriminate between different kinds of temperature distributions.
- [31] arXiv:0911.4086 [ps, pdf, other]
-
Title: Directional detection as a strategy to discover galactic Dark MatterComments: 4 pages, 4 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Directional detection of galactic Dark Matter is a promising search strategy for discriminating geniune WIMP events from background ones. Technical progress on gaseous detectors and read-out has permitted the design and construction of competitive experiments. However, to take full advantage of this powerful detection method, one need to be able to extract information from an observed recoil map to identify a WIMP signal. We present a comprehensive formalism, using a map-based likelihood method allowing to recover the main incoming direction of the signal and its significance, thus proving its galactic origin. Systematic studies are presented in order to show that, using this analysis tool, unambiguous dark matter detection can be achieved on a large range of exposures and background levels.
- [32] arXiv:0911.4107 [ps, pdf, other]
-
Title: Cosmic Evolution of Black Holes and Spheroids. IV. The BH Mass - Spheroid Luminosity RelationAuthors: Vardha Nicola Bennert (1), Tommaso Treu (1), Jong-Hak Woo (2), Matthew A. Malkan (3), Alexandre Le Bris (1), Matthew W. Auger (1), Sarah Gallagher (4), Roger D. Blandford (5) ((1) UCSB; (2) Seoul National University; (3) UCLA; (4) UWO; (5) KIPAC, Stanford)Comments: 39 pages, 11 figures. Accepted for publication in the Astrophysical JournalSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
From high-resolution images of 23 Seyfert-1 galaxies at z=0.36 and z=0.57 obtained with the Near Infrared Camera and Multi-Object Spectrometer on board the Hubble Space Telescope (HST), we determine host-galaxy morphology, nuclear luminosity, total host-galaxy luminosity and spheroid luminosity. Keck spectroscopy is used to estimate black hole mass (M_BH). We study the cosmic evolution of the M_BH-spheroid luminosity (L_sph) relation. In combination with our previous work, totaling 40 Seyfert-1 galaxies, the covered range in BH mass is substantially increased, allowing us to determine for the first time intrinsic scatter and correct evolutionary trends for selection effects. We re-analyze archival HST images of 19 local reverberation-mapped active galaxies to match the procedure adopted at intermediate redshift. Correcting spheroid luminosity for passive luminosity evolution and taking into account selection effects, we determine that at fixed present-day V-band spheroid luminosity, M_BH/L_sph \propto (1+z)^(2.8+/-1.2). When including a sample of 44 quasars out to z=4.5 taken from the literature, with luminosity and BH mass corrected to a self-consistent calibration, we extend the BH mass range to over two orders of magnitude, resulting in M_BH/L_sph \propto (1+z)^(1.4+/-0.2). The intrinsic scatter of the relation, assumed constant with redshift, is 0.3+/-0.1 dex (<0.6 dex at 95% CL). The evolutionary trend suggests that BH growth precedes spheroid assembly. Interestingly, the M_BH-total host-galaxy luminosity relation is apparently non-evolving. It hints at either a more fundamental relation or that the spheroid grows by a redistribution of stars. However, the high-z sample does not follow this relation, indicating that major mergers may play the dominant role in growing spheroids above z~1.
Cross-lists for Mon, 23 Nov 09
- [33] arXiv:0911.3717 (cross-list from cs.NE) [ps, pdf, other]
-
Title: Artificial Neural Network-based error compensation procedure for low-cost encodersComments: 16 pages, 4 figures. Accepted for Publication in Measurement Science and Technology (MST)Subjects: Neural and Evolutionary Computing (cs.NE); Instrumentation and Methods for Astrophysics (astro-ph.IM); Computational Physics (physics.comp-ph)
An Artificial Neural Network-based error compensation method is proposed for improving the accuracy of resolver-based 16-bit encoders by compensating for their respective systematic error profiles. The error compensation procedure, for a particular encoder, involves obtaining its error profile by calibrating it on a precision rotary table, training the neural network by using a part of this data and then determining the corrected encoder angle by subtracting the ANN-predicted error from the measured value of the encoder angle. Since it is not guaranteed that all the resolvers will have exactly similar error profiles because of the inherent differences in their construction on a micro scale, the ANN has been trained on one error profile at a time and the corresponding weight file is then used only for compensating the systematic error of this particular encoder. The systematic nature of the error profile for each of the encoders has also been validated by repeated calibration of the encoders over a period of time and it was found that the error profiles of a particular encoder recorded at different epochs show near reproducible behavior. The ANN-based error compensation procedure has been implemented for 4 encoders by training the ANN with their respective error profiles and the results indicate that the accuracy of encoders can be improved by nearly an order of magnitude from quoted values of ~6 arc-min to ~0.65 arc-min when their corresponding ANN-generated weight files are used for determining the corrected encoder angle.
- [34] arXiv:0911.3745 (cross-list from gr-qc) [ps, pdf, other]
-
Title: Loop quantum gravity and the CMB: toward pre-Big Bounce cosmologyAuthors: Aurelien BarrauComments: Proceedings of the 12th Marcel Grossman Meeting on General Relativity. 3 pages, no figureSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
This brief article sums up the possible imprints of loop quantum gravity effects on the cosmological microwave background. We focus on semi-classical terms and show that "Big Bounce" corrections, together with the "pre Big Bounce" state, could modify the observed spectrum.
- [35] arXiv:0911.3795 (cross-list from hep-ph) [ps, pdf, other]
-
Title: Potentially Large One-loop Corrections to WIMP AnnihilationComments: 19 pages, 6 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Extragalactic Astrophysics (astro-ph.CO)
We compute one--loop corrections to the annihilation of non--relativistic particles $\chi$ due to the exchange of a (gauge or Higgs) boson $\varphi$ with mass $\mu$ in the initial state. In the limit $m_\chi \gg \mu$ this leads to the "Sommerfeld enhancement" of the annihilation cross section. However, here we are interested in the case $\mu \lsim m_\chi$, where the one--loop corrections are well--behaved, but can still be sizable. We find simple and accurate expressions for annihilation from both $S-$ and $P-$wave initial states; they differ from each other if $\mu \neq 0$. In order to apply our results to the calculation of the relic density of Weakly Interacting Massive Particles (WIMPs), we describe how to compute the thermal average of the corrected cross sections. We show that these corrections can decrease the relic density of neutralinos in the Minimal Supersymmetric extension of the Standard Model by more than 1%, if the lightest neutralino is a strongly mixed state.
- [36] arXiv:0911.3805 (cross-list from gr-qc) [ps, pdf, other]
-
Title: Simple Types of Anisotropic InflationComments: 8pages, 3 figsSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
We display some simple cosmological solutions of gravity theories with quadratic Ricci curvature terms added to the Einstein-Hilbert lagrangian which exhibit anisotropic inflation. The Hubble expansion rates are constant and unequal in three orthogonal directions. We describe the evolution of the simplest of these homogeneous and anisotropic cosmological models from its natural initial state and evaluate the deviations they will create from statistical isotropy in the fluctuations produced during a period of anisotropic inflation. The anisotropic inflation is not a late-time attractor in these models but the rate of approach to a final isotropic de Sitter state is slow and is conducive to the creation of observable anisotropic statistical effects in the microwave background. The statistical anisotropy would not be scale invariant and the level of statistical anisotropy will grow with scale.
- [37] arXiv:0911.3889 (cross-list from gr-qc) [ps, pdf, other]
-
Title: Understanding possible electromagnetic counterparts to loud gravitational wave events: Binary black hole effects on electromagnetic fieldsComments: 12 pagesSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
In addition to producing loud gravitational waves (GW), the dynamics of a binary black hole system could induce emission of electromagnetic (EM) radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We here study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as an enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.
Replacements for Mon, 23 Nov 09
- [38] arXiv:0901.4566 (replaced) [ps, pdf, other]
-
Title: Cosmological background solutions and cosmological backreactionsComments: 14 pages, 5 figures; major changes, replaced to match the version published in General Relativity and GravitationSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
- [39] arXiv:0902.0131 (replaced) [ps, pdf, other]
-
Title: Search for high-energy muon neutrinos from the "naked-eye" GRB 080319B with the IceCube neutrino telescopeComments: 26 pages, 8 figures, version 3 corrects some typos in the formulae A2 and A5. The errors are not present in the code used in the analysis and hence none of the plots or results is affectedJournal-ref: Astrophys.J.701:1721-1731,2009Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [40] arXiv:0904.0809 (replaced) [pdf, other]
-
Title: Aether UnleashedComments: 41 pages, 1 figure and 4 tables. v2: Minor changes and added references, matches version accepted for publicationSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [41] arXiv:0905.1948 (replaced) [ps, pdf, other]
-
Title: Gamma-rays from dark matter annihilations strongly constrain the substructure in halosAuthors: Anders Pinzke (1), Christoph Pfrommer (2), Lars Bergstrom (1), ((1) Stockholm University, (2) CITA)Comments: 5 pages, 2 figures (published version; minor corrections to figures and result, equation added)Journal-ref: Phys.Rev.Lett.103:181302,2009Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [42] arXiv:0905.2417 (replaced) [ps, pdf, other]
-
Title: On the generation of high energy photons detected by the Fermi Satellite from gamma-ray burstsComments: 5 pages, 3 figures: Expanded introduction and added Figure 3. Accepted for publication in MNRAS LettersJournal-ref: MNRAS Letters 400 (2009) L75-L79Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [43] arXiv:0906.0905 (replaced) [ps, pdf, other]
-
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)
- [44] arXiv:0906.1578 (replaced) [ps, pdf, other]
-
Title: GRB 090423 at a redshift of z~8.1Authors: R. Salvaterra, M. Della Valle, S. Campana, G. Chincarini, S. Covino, P. D'Avanzo, A. Fernandez-Soto, C. Guidorzi, F. Mannucci, R. Margutti, C.C. Thoene, L.A. Antonelli, S.D. Barthelmy, M. De Pasquale, V. D'Elia, F. Fiore, D. Fugazza, L.K. Hunt, E. Maiorano, S. Marinoni, F.E. Marshall, E. Molinari, J. Nousek, E. Pian, J.L. Racusin, L. Stella, L. Amati, G. Andreuzzi, G. Cusumano, E.E. Fenimore, P. Ferrero, P. Giommi, D. Guetta, S.T. Holland, K. Hurley, G.L. Israel, J. Mao, C.B. Markwardt, N. Masetti, C. Pagani, E. Palazzi, D.M. Palmer, S. Piranomonte, G. Tagliaferri, V. TestaComments: Published in Nature. The astro-ph paper includes the main text (8 pages, 2 figures) and supplementary material (13 pages, 6 figures)Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
- [45] arXiv:0906.4119 (replaced) [ps, pdf, other]
-
Title: Constraints on Inelastic Dark Matter Signal using ZEPLIN-II ResultsComments: 4 pages, 2 figuresSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
- [46] arXiv:0907.0246 (replaced) [pdf, other]
-
Title: The destruction and survival of dust in the shell around SN 2008SAuthors: R. Wesson, M. J. Barlow, B. Ercolano, J. E. Andrews, Geoffrey C. Clayton, J. Fabbri, Joseph S. Gallagher, M. Meixner, B. E. K. Sugerman, D. L. Welch, D. J. StockComments: 9 pages, 7 figures, 3 tables. Revised version. To appear in MNRASSubjects: Galaxy Astrophysics (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
- [47] arXiv:0908.0245 (replaced) [ps, pdf, other]
-
Title: Structure and Population of the Andromeda Stellar Halo from a Subaru/Suprime-Cam SurveyComments: 40 pages, 44 figures, accepted for publication in the ApJ. High resolution version available at this http URLSubjects: Galaxy Astrophysics (astro-ph.GA); Cosmology and Extragalactic Astrophysics (astro-ph.CO)
- [48] arXiv:0908.1887 (replaced) [ps, pdf, other]
-
Title: Spin susceptibility of degenerate quark matterComments: 15 pages, 2 figures, New section added, published in Physical Review C,80,054911Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
- [49] arXiv:0908.4179 (replaced) [ps, pdf, other]
-
Title: Compressed sensing reconstruction of a string signal from interferometric observations of the cosmic microwave backgroundComments: 11 pages, 6 figures. Version 2 matches version accepted for publication in MNRAS. Changes include minor clarificationsSubjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)
- [50] arXiv:0911.2338 (replaced) [ps, pdf, other]
-
Title: Extending the search for neutrino point sources with IceCube above the horizonComments: 6 pages, 4 figures. Updated to match version published in Phys. Rev. LettSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [51] arXiv:0911.3285 (replaced) [ps, pdf, other]
-
Title: A 3D radiative transfer framework: VI. PHOENIX/3D example applicationsComments: fixed PDF generation problem. Also available at tp://ftp.hs.uni-hamburg.de/pub/outgoing/phoenix/preprints/3DRT_paper6.pdf A&A, in press (Ref: AA/2009/13064)Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Methods for Astrophysics (astro-ph.IM)
- [52] arXiv:0911.3883 (replaced) [ps, pdf, other]
-
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)
[ showing up to 2000 entries per page: fewer | more ]