Date: Thu, 25 Feb 10 01:00:18 GMT Subject: astro-ph daily 37 new + 4 crosses received by eprepget ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ Send any comments regarding submissions directly to submitter. ------------------------------------------------------------------------------ Archives at http://arxiv.org/ To unsubscribe, e-mail To: astro-ph@arXiv.org, Subject: cancel ------------------------------------------------------------------------------ received by eprepget from Tue 23 Feb 10 21:00:02 GMT to Wed 24 Feb 10 21:00:01 GMT ------------------------------------------------------------------------------ \\ arXiv:1002.4405 Date: Tue, 23 Feb 2010 21:00:05 GMT (319kb,D) Title: Distinguishing standard reionization from dark matter models Authors: Aravind Natarajan, Dominik J. Schwarz Categories: astro-ph.CO Comments: 15 pages, 5 figures, submitted to Physical Review D \\ The WMAP experiment has detected reionization at the $5.5 \sigma$ level and has reported a mean optical depth of $0.088 \pm 0.015$. A powerful probe of reionization is the large-angle $EE$ polarization power spectrum, which is now (since the first five years of data from WMAP) cosmic variance limited for $2\le l \le6$. Here we consider partial reionization caused by WIMP dark matter annihilation, and calculate the expected polarization power spectrum. We compare the dark matter models with a standard 2-step reionization theory, and examine whether the models may be distinguished using current, and future CMB observations. We consider dark matter annihilation at intermediate redshifts ($z<60$) due to halos, as well as annihilation at higher redshifts due to free particles. In order to study the effect of high redshift dark matter annihilation on CMB power spectra, it is essential to include the contribution of residual electrons (left over from recombination) to the ionization history. Dark matter halos at redshifts $z<60$ influence the low multipoles $l<20$ in the $EE$ power spectrum, while the annihilation of free particle dark matter at high redshifts $z>100$ mainly affects multipoles $l>10$. \\ ( http://arxiv.org/abs/1002.4405 , 319kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4406 Date: Tue, 23 Feb 2010 21:00:11 GMT (308kb) Title: p3d: a general data-reduction tool for fiber-fed integral-field spectrographs Authors: C. Sandin, T. Becker, M. M. Roth, J. Gerssen, A. Monreal-Ibero, P. B\"ohm, P. Weilbacher Categories: astro-ph.IM Comments: 18 pages, 15 figures, 3 tables, accepted for publication in A&A \\ The reduction of integral-field spectrograph (IFS) data is demanding work. Many repetitive operations are required in order to convert raw data into, typically a large number of, spectra. This effort can be markedly simplified through the use of a tool or pipeline, which is designed to complete many of the repetitive operations without human interaction. Here we present our semi-automatic data-reduction tool p3d that is designed to be used with fiber-fed IFSs. Important components of p3d include a novel algorithm for automatic finding and tracing of spectra on the detector, and two methods of optimal spectrum extraction in addition to standard aperture extraction. p3d also provides tools to combine several images, perform wavelength calibration and flat field data. p3d is at the moment configured for four IFSs. In order to evaluate its performance we have tested the different components of the tool. For these tests we used both simulated and observational data. We demonstrate that for three of the IFSs a correction for so-called cross-talk due to overlapping spectra on the detector is required. Without such a correction spectra will be inaccurate, in particular if there is a significant intensity gradient across the object. Our tests showed that p3d is able to produce accurate results. p3d is a highly general and freely available tool. It is easily extended to include improved algorithms, new visualization tools and support for additional instruments. The program code can be downloaded from the p3d-project web site http://p3d.sourceforge.net \\ ( http://arxiv.org/abs/1002.4406 , 308kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4412 Date: Tue, 23 Feb 2010 21:34:11 GMT (111kb) Title: A NLTE analysis of boron abundances in metal-poor stars Authors: Kefeng Tan, Jianrong Shi, Gang Zhao Categories: astro-ph.SR Comments: accepted for publication in ApJ \\ The non-local thermodynamic equilibrium (NLTE) line formation of neutral boron in the atmospheres of cool stars are investigated. Our results confirm that NLTE effects for the B I resonance lines, which are due to a combination of overionization and optical pumping effects, are most important for hot, metalpoor, and low-gravity stars; however, the amplitude of departures from LTE found by this work are smaller than that of previous studies. In addition, our calculation shows that the line formation of B I will get closer to LTE if the strength of collisions with neutral hydrogen increases, which is contrary to the result of previous studies. The NLTE line formation results are applied to the determination of boron abundances for a sample of 16 metal-poor stars with the method of spectrum synthesis of the B I 2497 A resonance lines using the archived HST/GHRS spectra. Beryllium and oxygen abundances are also determined for these stars. The abundances of the nine stars which are not depleted in Be or B show that, no matter the strength of collisions with neutral hydrogen may be, both Be and B increase with O quasi-linearly in the logarithmic plane, which confirms the conclusions that Be and B are mainly produced by primary process in the early Galaxy. The most noteworthy result of this work is that B increases with Fe or O at a very similar speed as, or a bit faster than Be does, which is in accord with the theoretical models. The B/Be ratios remain almost constant over the metallicity range investigated here. Our average B/Be ratio falls in the interval [13+-4, 17+-4], which is consistent with the predictions of spallation process. The contribution of B from the nu-process may be required if the 11B/10B isotopic ratios in metal-poor stars are the same as the meteoric value. \\ ( http://arxiv.org/abs/1002.4412 , 111kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4413 Date: Tue, 23 Feb 2010 21:30:38 GMT (1350kb) Title: AGN activity: Self-regulation from backflow Authors: V. Antonuccio-Delogu (INAF) and J. Silk (Oxford) Categories: astro-ph.CO Comments: 13 pages, 11 figures. Accepted for publication by MNRAS \\ We study the internal circulation within the cocoon carved out by the relativistic jet emanating from an AGN within the ISM of its host galaxy. Firstly, we develop a model for the origin of the internal flow, noticing that a significant increase of large scale velocity circulation within the cocoon arises as significant gradients in the density and entropy are created near the hot spot (a consequence of Crocco's vorticity generation theorem). We find simple and accurate approximate solutions for the large scale flow,showing that a backflow towards the few inner parsec region develops. We solve the appropriate fluid dynamic equations, and we use these solutions to predict the mass inflow rates towards the central regions. We then perform a series of 2D simulations of the propagation of jets using FLASH 2.5, in order to validate the predictions of our model. The backflows which arise supply the central AGN region with very low angular momentum gas, at average rates of the order of $0.1-0.8 \rm{M}_{\odot} \rm{yr.}^{-1}$, the exact value seen to be strongly dependent on the central ISM density (for fixed input jet power). The time scales of these inflows are apparently weakly dependent on the jet/ISM parameters, and are of the order of $3-5\times 10^{7} \rm{yrs}$. We then argue that these backflows could (at least partially) feed the AGN, and provide a self-regulatory mechanism of AGN activity, that is not directly controlled by, but instead controls, the star formation rate within the central circumnuclear disk. \\ ( http://arxiv.org/abs/1002.4413 , 1350kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4414 Date: Tue, 23 Feb 2010 21:05:33 GMT (840kb) Title: The mass assembly of galaxy groups and the evolution of the magnitude gap Authors: Ali A. Dariush, Somak Raychaudhury, Trevor J. Ponman, Habib G. Khosroshahi, Andrew J. Benson, Richard G. Bower, Frazer Pearce Categories: astro-ph.CO Comments: 16 pages, 11 figures, 2 tables. Accepted for publication in MNRAS \\ We investigate the assembly of groups and clusters of galaxies using the Millennium dark matter simulation and the associated gas simulations and semi-analytic catalogues of galaxies. In particular, in order to find an observable quantity that could be used to identify early-formed groups, we study the development of the difference in magnitude between their brightest galaxies to assess the use of magnitude gaps as possible indicators. We select galaxy groups and clusters at redshift z=1 with dark matter halo mass M(R200) > 1E13/h Msun, and trace their properties until the present time (z=0). We consider only the systems with X-ray luminosity L_X> 0.25E42/h^2 erg/s at z=0. While it is true that a large magnitude gap between the two brightest galaxies of a particular group often indicates that a large fraction of its mass was assembled at an early epoch, it is not a necessary condition. More than 90% of fossil groups defined on the basis of their magnitude gaps (at any epoch between 0 2 (in the R-band, within 0.5R200 of the centre of the group), an alternative criterion Delta m(14)>2.5 (within the same radius) finds 50% more early-formed systems, and those that on average retain their fossil phase longer. However, the conventional criterion performs marginally better at finding early-formed groups at the high-mass end of groups. Nevertheless, both criteria fail to identify a majority of the early-formed systems. \\ ( http://arxiv.org/abs/1002.4414 , 840kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4415 Date: Wed, 24 Feb 2010 20:41:15 GMT (2424kb,D) Title: Constraints on Cosmological Dark Matter Annihilation from the Fermi-LAT Isotropic Diffuse Gamma-Ray Measurement Authors: The Fermi-LAT collaboration: A. A. Abdo, M. Ackermann, M. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, A. Bouvier, J. Bregeon, A. Brez, M. Brigida, P. Bruel, T. H. Burnett, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, S. Carrigan, J. M. Casandjian, C. Cecchi, O. C. Elik, A. Chekhtman, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, S. Cutini, C. D. Dermer, A. de Angelis, F. de Palma, S. W. Digel, E. do Couto e Silva, P. S. Drell, R. Dubois, D. Dumora, Y. Edmonds, C. Farnier, C. Favuzzi, S. J. Fegan, W. B. Focke, P. Fortin, M. Frailis, Y. Fukazawa, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, N. Giglietto, F. Giordano, T. Glanzman, et al. (89 additional authors not shown) Categories: astro-ph.CO astro-ph.HE Comments: 29 pages, 7 figures, to be published in JCAP. Corresponding authors: Jan Conrad, Michael Gustafsson, Alexander Sellerholm, Gabrijela Zaharijas \\ The first published Fermi large area telescope (Fermi-LAT) measurement of the isotropic diffuse gamma-ray emission is in good agreement with a single power law, and is not showing any signature of a dominant contribution from dark matter sources in the energy range from 20 to 100 GeV. We use the absolute size and spectral shape of this measured flux to derive cross section limits on three types of generic dark matter candidates: annihilating into quarks, charged leptons and monochromatic photons. Predicted gamma-ray fluxes from annihilating dark matter are strongly affected by the underlying distribution of dark matter, and by using different available results of matter structure formation we assess these uncertainties. We also quantify how the dark matter constraints depend on the assumed conventional backgrounds and on the Universe's transparency to high-energy gamma-rays. In reasonable background and dark matter structure scenarios (but not in all scenarios we consider) it is possible to exclude models proposed to explain the excess of electrons and positrons measured by the Fermi-LAT and PAMELA experiments. Derived limits also start to probe cross sections expected from thermally produced relics (e.g. in minimal supersymmetry models) annihilating predominantly into quarks. For the monochromatic gamma-ray signature, the current measurement constrains only dark matter scenarios with very strong signals. \\ ( http://arxiv.org/abs/1002.4415 , 2424kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4418 Date: Tue, 23 Feb 2010 21:10:51 GMT (256kb) Title: Galaxy Pairs in the Sloan Digital Sky Survey - II: The Effect of Environment on Interactions Authors: Sara L. Ellison, David R. Patton, Luc Simard, Alan W. McConnachie, Ivan K. Baldry Categories: astro-ph.CO Comments: Submitted to MNRAS, 16 pages \\ We use a sample of close galaxy pairs selected from the SDSS DR4 to investigate in what environments galaxy mergers occur and how the results of these mergers depend on differences in local galaxy density. Lower density environments have fractionally more galaxy pairs with small projected separations (r_p) and relative velocities (Delta V), but even high density environments contain significant populations of pairs with parameters that should be conducive to interactions. The connection between environment and Delta V also implies that the velocity selection of a pairs sample affects (biases) the environment from which the pairs are selected. Metrics of asymmetry and colour are used to identify merger activity and triggered star formation. The location of star formation is inferred by distinguishing bulge and disk colours and calculating bulge fractions from the SDSS images. Considering only pairs with Delta V < 200 km/s, we show that the asymmetry of galaxies with a close companion increases at all local densities at r_p < 30 kpc. However, of these closely separated pairs, galaxies in the lowest density environments exhibit the most significant trends towards increased star formation rates and bluer bulge colours. We interpret these results as evidence that whilst interactions occur at all densities, triggered star formation is seen only in low-to-intermediate density environments. We argue that this is likely due to the typically higher gas fractions of galaxies in low density environments. Finally, by cross-correlating our sample of galaxy pairs with a cluster catalogue, we find evidence for galaxy-galaxy interactions only at the cluster periphery. \\ ( http://arxiv.org/abs/1002.4418 , 256kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4421 Date: Tue, 23 Feb 2010 21:27:55 GMT (361kb) Title: A Catalog of MIPSGAL Disk and Ring Sources Authors: D.R. Mizuno (1), K. E. Kraemer (2), N. Flagey (3), N. Billot (4), S. Shenoy (5), R. Paladini (3), E. Ryan (6), A. Noriega-Crespo (3), S. J. Carey (3). ((1) Institute for Scientific Research, (2) Air Force Research Laboratory, (3) Spitzer Science Center, (4) NASA Herschel Science Center, (5) Ames Research Center, (6) University of Minnesota) Categories: astro-ph.GA \\ We present a catalog of 416 extended, resolved, disk- and ring-like objects as detected in the MIPSGAL 24 micron survey of the Galactic plane. This catalog is the result of a search in the MIPSGAL image data for generally circularly symmetric, extended "bubbles" without prior knowledge or expectation of their physical nature. Most of the objects have no extended counterpart at 8 or 70 micron, with less than 20% detections at each wavelength. For the 54 objects with central point sources, the sources are nearly always seen in all IRAC bands. About 70 objects (16%) have been previously identified, with another 35 listed as IRAS sources. Among the identified objects, those with central sources are mostly listed as emission-line stars, but with other source types including supernova remnants, luminous blue variables, and planetary nebulae. The 57 identified objects (of 362) without central sources are nearly all PNe (~90%).which suggests that a large fraction of the 300+ unidentified objects in this category are also PNe. These identifications suggest that this is primarily a catalog of evolved stars. Also included in the catalog are two filamentary objects that are almost certainly SNRs, and ten unusual compact extended objects discovered in the search. Two of these show remarkable spiral structure at both 8 and 24 micron. These are likely background galaxies previously hidden by the intervening Galactic plane. \\ ( http://arxiv.org/abs/1002.4421 , 361kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4434 Date: Tue, 23 Feb 2010 23:02:21 GMT (254kb,D) Title: Magnetic Field Effects near the launching region of Astrophysical Jets Authors: E. M. de Gouveia Dal Pino, G. Kowal, L. H. S. Kadowaki, P. Piovezan, A. Lazarian Categories: astro-ph.HE Comments: 9 pages, 3 figures, invited paper for the Procs. of the Conference on High Energy Phenomena in Relativistic Outflows II, Buenos Aires, October 2009. Submitted to International Journal of Modern Physics D \\ One of the fundamental properties of astrophysical magnetic fields is their ability to change topology through reconnection and in doing so, to release magnetic energy, sometimes violently. In this work, we review recent results on the role of magnetic reconnection and associated heating and particle acceleration in jet/accretion disk systems, namely young stellar objects (YSOs), microquasars, and active galactic nuclei (AGNs). \\ ( http://arxiv.org/abs/1002.4434 , 254kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4447 Date: Wed, 24 Feb 2010 01:41:02 GMT (43kb) Title: Interior structure models of GJ 436b Authors: N. Nettelmann, U. Kramm, R. Redmer, and R. Neuhaeuser Categories: astro-ph.EP Comments: submitted to A&A \\ GJ436b is the first extrasolar planet discovered that resembles Neptune in mass and radius, two more are known (HAT-P-11b and Kepler-4b), and many more are expected to be found in the upcoming years. The particularly interesting property of Neptune-sized planets is that their mass Mp and radius Rp are close to theoretical M-R relations of water planets. Given Mp, Rp, and equilibrium temperature however, various internal compositions are possible. A broad set of interior structure models is presented here that illustrates the dependence of internal composition and possible phases of water in presumably water-rich planets such as GJ436b on the uncertainty in atmospheric temperature profile and mean density. We model the interior by assuming either three layers (hydrogen-helium envelope, water layer, rock core) or two layers (H/He/H2O envelope, rocky core). For water we use the equation of state H2O-REOS based on FT-DFT-MD. Some admixture of H/He appears mandatory for explaining the measured radius. In case of the warmest models considered, the H/He mass fraction can reduce to 0.1%, yet extending over 0.7 Rearth. If water occurs, it will be essentially in the plasma phase or in the superionic phase, but not in an ice phase. Metal-free envelope models have 0.020.3, and further to 0.2 Mp, if k2>0.5, and core mass and Z1 become a sensitive function of k2. \\ ( http://arxiv.org/abs/1002.4447 , 43kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4469 Date: Wed, 24 Feb 2010 05:16:59 GMT (174kb) Title: Can cold quark matter be solid? Authors: Renxin Xu (PKU) Categories: astro-ph.HE astro-ph.SR Comments: Submitted to Proceedings of IWARA2009 \\ The state of cold quark matter really challenges both astrophysicists and particle physicists, even many-body physicists. It is conventionally suggested that BCS-like color superconductivity occurs in cold quark matter; however, other scenarios with a ground state rather than of Fermi gas could still be possible. It is addressed that quarks are dressed and clustering in cold quark matter at realistic baryon densities of compact stars, since a weakly coupling treatment of the interaction between constituent quarks would not be reliable. Cold quark matter is conjectured to be in a solid state if thermal kinematic energy is much lower than the interaction energy of quark clusters, and such a state could be relevant to different manifestations of pulsar-like compact stars. \\ ( http://arxiv.org/abs/1002.4469 , 174kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4472 Date: Wed, 24 Feb 2010 05:42:04 GMT (4103kb,D) Title: The Wide Field Spectrograph (WiFeS): Performance and Data Reduction Authors: Michael Dopita, Jonghwan Rhee, Catherine Farage, Peter McGregor, Gabe Bloxham, Anthony Green, Bill Roberts, Jon Nielson, Greg Wilson, Peter Young Categories: astro-ph.IM Comments: Accepted for publication in Astrophysics & Space Science, 15pp, 11 figures DOI: 10.1007/s10509-010-0335-9 \\ This paper describes the on-telescope performance of the Wide Field Spectrograph (WiFeS). The design characteristics of this instrument, at the Research School of Astronomy and Astrophysics (RSAA) of the Australian National University (ANU) and mounted on the ANU 2.3m telescope at the Siding Spring Observatory has been already described in an earlier paper (Dopita et al. 2007). Here we describe the throughput, resolution and stability of the instrument, and describe some minor issues which have been encountered. We also give a description of the data reduction pipeline, and show some preliminary results. \\ ( http://arxiv.org/abs/1002.4472 , 4103kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4474 Date: Wed, 24 Feb 2010 06:03:17 GMT (48kb) Title: Thick gas disks in faint dwarf galaxies Authors: Sambit Roychowdhury, Jayaram N. Chengalur, Ayesha Begum, Igor D. Karachentsev Categories: astro-ph.CO Comments: 5 pages, 4 figures. Accepted for publication in MNRAS Letters \\ We determine the intrinsic axial ratio distribution of the 'gas' disks of extremely faint M_B < -14.5 dwarf irregular galaxies. We start with the measured (beam corrected) distribution of apparent axial ratios in the HI 21cm images of dwarf irregular galaxies observed as part of the Faint Irregular Galaxy GMRT Survey (FIGGS). Assuming that the disks can be approximated as oblate spheroids, the intrinsic axial ratio distribution can be obtained from the observed apparent axial ratio distribution. We use a variety of methods to do this, and our final results are based on using Lucy's deconvolution algorithm. This method is constrained to produce physically plausible distributions, and also has the added advantage of allowing for observational errors to be accounted for. While one might a priori expect that gas disks would be thin (because collisions between gas clouds would cause them to quickly settle down to a thin disk), we find that the HI disks of faint dwarf irregulars are quite thick, with mean axial ratio ~ 0.6. While this is substantially larger than the typical value of ~ 0.2 for the 'stellar' disks of large spiral galaxies, it is consistent with the much larger ratio of velocity dispersion to rotational velocity (sigma/v_c) in dwarf galaxy HI disks as compared to that in spiral galaxies. Our findings have implications for studies of the mass distribution in and the Tully - Fisher relation for faint dwarf irregular galaxies, where it is often assumed that the gas is in a thin disk. \\ ( http://arxiv.org/abs/1002.4474 , 48kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4475 Date: Wed, 24 Feb 2010 06:18:33 GMT (41kb) Title: Chemodynamical simulations with variable IMF Authors: Chiaki Kobayashi Categories: astro-ph.CO astro-ph.GA Comments: 4 pages, 3 figures, to appear in "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P. Debattista and C.C. Popescu, AIP Conf. Ser., in press \\ Using self-consistent chemodynamical simulations including star formation, supernova feedback, and chemical enrichment, I show the dependence of cosmic star formation and chemical enrichment histories on the initial mass function (IMF). The effects of Pop-III IMF can be only seen in the elemental abundance ratios at z>4 or [Fe/H]<-2. The preferable IMF has a flatter slope in the case of high star formation rate (SFR) and smaller upper-mass (~20Msun) in the case of low SFR, which is consistent with the observed elemental abundances of dwarf spheroidal galaxies. However, the [alpha/Fe] problem of elliptical galaxies may require other solutions. \\ ( http://arxiv.org/abs/1002.4475 , 41kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4477 Date: Wed, 24 Feb 2010 07:07:32 GMT (126kb) Title: HD 209621: Abundances of neutron-capture elements Authors: Aruna Goswami (1), Wako Aoki (2) ((1) Indian Institute of Astrophysics, Bangalore, (2) National Astronomical Observatory, Mitaka, Tokyo) Categories: astro-ph.SR Comments: 16 pages,8 figures. Accepted for publication in MNRAS \\ High resolution spectra obtained from the Subaru Telescope High Dispersion Spectrograph have been used to update the stellar atmospheric parameters and metallicity of the star HD 209621. We have derived a metallicity of [Fe/H] = -1.93 for this star, and have found a large enhancement of carbon and of heavy elements, with respect to iron. Updates on the elemental abundances of four s-process elements (Y, Ce, Pr, Nd) along with the first estimates of abundances for a number of other heavy elements (Sr, Zr, Ba, La, Sm, Eu, Er, Pb) are reported. The stellar atmospheric parameters, the effective temperature, Teff, and the surface gravity, log g (4500 K, 2.0), are determined from LTE analysis using model atmospheres. Estimated [Ba/Eu] = +0.35, places the star in the group of CEMP-(r+s) stars; however, the s-elements abundance pattern seen in HD 209621 is characteristic of CH stars; notably, the 2nd-peak s-process elements are more enhanced than the first peak s-process elements. HD 209621 is also found to show a large enhancement of the 3rd-peak s-process element lead (Pb) with [Pb/Fe] = +1.88. The relative contributions of the two neutron-capture processes, r- and s- to the observed abundances are examined using a parametric model based analysis, that hints that the neutron-capture elements in HD 209621 primarily originate in s-process. \\ ( http://arxiv.org/abs/1002.4477 , 126kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4479 Date: Wed, 24 Feb 2010 06:18:22 GMT (916kb) Title: On the coldness of the local Hubble flow: the role of baryons Authors: S\'ebastien Peirani (IAP) Categories: astro-ph.CO Comments: Submitted to MNRAS, 11 pages, 7 figures \\ (Abridged) Our aim is to investigate whether the presence of baryons can have any significant influence on the properties of the local Hubble flow which has proved to be "cold". We use two cosmological zoom simulations in the standard LCDM cosmology with the same set of initial conditions to study the formation of a local group-like system within a sphere of ~7 Mpc/h. The first one is a pure dark matter simulation (runDM) while a complete treatment of the physics of baryons is introduced in the second one (runB). We found that galaxies identified in runB and their corresponding dark matter haloes in runDM have very similar spatial distributions and dynamical properties on large scales. Then, when analyzing the velocity field and the deviation from a pure Hubble flow in both simulations, namely when computing the dispersion of peculiar velocities of galaxies ?*(R) and those of their corresponding dark matter haloes in runDM, we found no particular differences for distances R=1 to 8 Mpc from the local group mass center. The results indicate that the "true" ?*(R) values can be estimated from the pure dark matter simulation with a mean error of 3 km/s when dark matter haloes are selected with maximum circular velocities of Vc?30 km/s, corresponding to a population of dark matter haloes in runB that host galaxies. By investigating the properties of the Hubble flow at distances R~0.7 to 3 Mpc, we also found that the estimation of the total mass enclosed at the radius of the zero-velocity surface R0, using the spherical infall model adapted to LCDM, can be underestimated by at least 50%. \\ ( http://arxiv.org/abs/1002.4479 , 916kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4480 Date: Wed, 24 Feb 2010 06:21:23 GMT (462kb) Title: X-ray views of neutron star low-mass X-ray binaries Authors: Sudip Bhattacharyya (TIFR, India) Categories: astro-ph.HE astro-ph.GA Comments: 21 pages, 13 figures, An Invited Review, published in Current Science Journal-ref: Current Science.97:804-820,2009 \\ A neutron star low-mass X-ray binary is a binary stellar system with a neutron star and a low-mass companion star rotating around each other. In this system the neutron star accretes mass from the companion, and as this matter falls into the deep potential well of the neutron star, the gravitational potential energy is released primarily in the X-ray wavelengths. Such a source was first discovered in X-rays in 1962, and this discovery formally gave birth to the "X-ray astronomy". In the subsequent decades, our knowledge of these sources has increased enormously by the observations with several X-ray space missions. Here we give a brief overview of our current understanding of the X-ray observational aspects of these systems. \\ ( http://arxiv.org/abs/1002.4480 , 462kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4497 Date: Wed, 24 Feb 2010 09:31:30 GMT (120kb) Title: On the maximum and minimum mass of protoneutron stars in the Brueckner theory Authors: G.F. Burgio and H.-J. Schulze (INFN Catania, Italy) Categories: astro-ph.SR Comments: 8 pages, 7 figures \\ We study the structure of protoneutron stars within the finite-temperature Brueckner-Bethe-Goldstone theoretical approach, paying particular attention to the joining with a low-density nuclear equation of state (EOS). We find a slight sensitivity of the minimum value of the protoneutron star mass on the low-density EOS, whereas the maximum mass is hardly affected. \\ ( http://arxiv.org/abs/1002.4497 , 120kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4503 Date: Wed, 24 Feb 2010 09:50:19 GMT (361kb) Title: A statistical method to determine open cluster metallicities Authors: Harald Poehnl, Ernst Paunzen Categories: astro-ph.GA astro-ph.SR Comments: 14 pages, 6 figures, accepted for publication in Astronomy & Astrophysics \\ The study of open cluster metallicities helps to understand the local stellar formation and evolution throughout the Milky Way. Its metallicity gradient is an important tracer for the Galactic formation in a global sense. Because open clusters can be treated in a statistical way, the error of the cluster mean is minimized. Our final goal is a semi-automatic statistical robust method to estimate the metallicity of a statistically significant number of open clusters based on Johnson BV data of their members, an algorithm that can easily be extended to other photometric systems for a systematic investigation. This method incorporates evolutionary grids for different metallicities and a calibration of the effective temperature and luminosity. With cluster parameters (age, reddening and distance) it is possible to estimate the metallicity from a statistical point of view. The iterative process includes an intrinsic consistency check of the starting input parameters and allows us to modify them. We extensively tested the method with published data for the Hyades and selected sixteen open clusters within 1000pc around the Sun with available and reliable Johnson BV measurements. In addition, Berkeley 29, with a distance of about 15kpc was chosen. For several targets we are able to compare our result with published ones which yielded a very good coincidence (including Berkeley 29). \\ ( http://arxiv.org/abs/1002.4503 , 361kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4514 Date: Wed, 24 Feb 2010 10:31:47 GMT (88kb) Title: Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics Authors: Poul E. Nissen and William J. Schuster Categories: astro-ph.GA Comments: Accepted for publication in A&A as a four-page Letter with five pages of online material \\ Precise abundance ratios are determined for 94 dwarf stars with 5200 < Teff < 6300 K, -1.6 < [Fe/H] < -0.4, and distances D < 335 pc. Most of them have halo kinematics, but 16 thick-disk stars are included. Equivalent widths of atomic lines are measured from VLT/UVES and NOT/FIES spectra with resolutions R = 55000 and R = 40000, respectively. An LTE abundance analysis based on MARCS models is applied to derive precise differential abundance ratios of Na, Mg, Si, Ca, Ti, Cr, and Ni with respect to Fe. The halo stars fall into two populations, clearly separated in [alpha/Fe], where alpha refers to the average abundance of Mg, Si, Ca, and Ti. Differences in [Na/Fe] and [Ni/Fe] are also present with a remarkably clear correlation between these two abundance ratios. The `high-alpha' stars may be ancient disk or bulge stars `heated' to halo kinematics by merging satellite galaxies or they could have formed as the first stars during the collapse of a proto-Galactic gas cloud. The kinematics of the `low-alpha' stars suggest that they have been accreted from dwarf galaxies, and that some of them may originate from the omega Cen progenitor galaxy. \\ ( http://arxiv.org/abs/1002.4514 , 88kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4521 Date: Wed, 24 Feb 2010 11:09:15 GMT (1343kb) Title: Large-scale distributions of mid- and far-infrared emission from the center to the halo of M82 revealed with AKARI Authors: H. Kaneda, D. Ishihara, T.Suzuki, N. Ikeda, T. Onaka, M. Yamagishi, Y. Ohyama, T. Wada, A. Yasuda Categories: astro-ph.GA Comments: 12 pages, 8 figures, accepted for publication in A&A \\ The edge-on starburst galaxy M82 exhibits complicated distributions of gaseous materials in its halo, which include ionized superwinds driven by nuclear starbursts, neutral materials entrained by the superwinds, and large-scale neutral streamers probably caused by a past tidal interaction with M81. We investigate detailed distributions of dust grains and polycyclic aromatic hydrocarbons (PAHs) around M82 to understand their interplay with the gaseous components. We performed mid- (MIR) and far-infrared (FIR) observations of M82 with the Infrared Camera and Far-Infrared Surveyor on board AKARI. We obtain new MIR and FIR images of M82, which reveal both faint extended emission in the halo and very bright emission in the center with signal dynamic ranges as large as five and three orders of magnitude for the MIR and FIR, respectively. We detect MIR and FIR emission in the regions far away from the disk of the galaxy, reflecting the presence of dust and PAHs in the halo of M82. We find that the dust and PAHs are contained in both ionized and neutral gas components, implying that they have been expelled into the halo of M82 by both starbursts and galaxy interaction. In particular, we obtain a tight correlation between the PAH and H$\alpha$ emission, which provides evidence that the PAHs are well mixed in the ionized superwind gas and outflowing from the disk. \\ ( http://arxiv.org/abs/1002.4521 , 1343kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4523 Date: Wed, 24 Feb 2010 11:21:22 GMT (24kb) Title: Have Cherenkov telescopes detected a new light boson? Authors: Marco Roncadelli, Alessandro De Angelis, Oriana Mansutti Categories: astro-ph.HE astro-ph.CO Comments: 3 pages, 1 figure, Proceeding of the "Eleventh International Workshop on Topics in Astroparticle and Underground Physics" (TAUP), Roma, Italy, 1 - 5 July 2009 (to be published in the Proceedings) \\ Recent observations by H.E.S.S. and MAGIC strongly suggest that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with standard blazar emission models provided that photon oscillations into a very light Axion-Like Particle occur in extragalactic magnetic fields. A quantitative estimate of this effect indeed explains the observed data and in particular the spectrum of blazar 3C279. \\ ( http://arxiv.org/abs/1002.4523 , 24kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4524 Date: Wed, 24 Feb 2010 11:37:46 GMT (45kb) Title: The compact radio structure of the high-redshift blazar J1430+4204 before and after a major outburst Authors: P\'eter Veres, S\'andor Frey, Zsolt Paragi, Leonid I. Gurvits Categories: astro-ph.CO Comments: Proceedings of the 5th Workshop of Young Researchers in Astronomy and Astrophysics, Budapest, 2009; to be published in J. Phys.: Conf. Series (JPCS); 4 pages, 3 figures \\ The high-redshift (z=4.72) blazar J1430+4204 produced an exceptional radio outburst in 2006. We analyzed 15-GHz radio interferometric images obtained with the Very Long Baseline Array (VLBA) before and after the outburst, to search for possible structural changes on milli-arcsecond angular scales and to determine physical parameters of the source. \\ ( http://arxiv.org/abs/1002.4524 , 45kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4528 Date: Wed, 24 Feb 2010 11:49:08 GMT (708kb) Title: Varying Constants: Constraints from Seasonal Variations Authors: Douglas J. Shaw, John D. Barrow Categories: astro-ph.CO physics.atom-ph Comments: 4 pages, 1 figure. Contribution to the proceedings of the Joint Discussion 9, XXVIIth IAU, General Assembly, Rio de Janeiro :"Are the fundamental constants varying with spacetime?" Journal-ref: Memorie della Societa Astronomica Italiana, 80, 640-643, (2009) \\ We analyse the constraints obtained from new atomic clock data on the possible time variation of the fine structure `constant' and the electron-proton mass ratio and show how they are strengthened when the seasonal variation of Sun's gravitational field at the Earth's surface is taken into account. \\ ( http://arxiv.org/abs/1002.4528 , 708kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4539 Date: Wed, 24 Feb 2010 15:47:27 GMT (179kb) Title: The evolution of galaxy cluster X-ray scaling relations Authors: C. J. Short (1), P. A. Thomas (1), O. E. Young (1), F. R. Pearce (2), A. Jenkins (3), O. Muanwong (4) ((1)University of Sussex, UK, (2)University of Nottingham, UK, (3)University of Durham, UK, (4)Khon Kaen University, Thailand) Categories: astro-ph.CO Comments: 21 pages, 13 figures, 3 tables. Submitted to MNRAS \\ We use numerical simulations to investigate, for the first time, the joint effect of feedback from supernovae (SNe) and active galactic nuclei (AGN) on the evolution of galaxy cluster X-ray scaling relations. Our simulations are drawn from the Millennium Gas Project and are some of the largest hydrodynamical N-body simulations ever carried out. Feedback is implemented using a hybrid scheme, where the energy input into intracluster gas by SNe and AGN is taken from a semi-analytic model of galaxy formation. This ensures that the source of feedback is a population of galaxies that closely resembles that found in the real universe. We show that our feedback model is capable of reproducing observed local X-ray scaling laws, at least for non-cool core clusters, but that almost identical results can be obtained with a simplistic preheating model. However, we demonstrate that the two models predict opposing evolutionary behaviour. We have examined whether the evolution predicted by our feedback model is compatible with observations of high-redshift clusters. Broadly speaking, we find that the data seems to favour the feedback model for z<0.5, and the preheating model at higher redshift. However, a statistically meaningful comparison with observations is impossible, because the large samples of high-redshift clusters currently available are prone to strong selection biases. As the observational picture becomes clearer in the near future, it should be possible to place tight constraints on the evolution of the scaling laws, providing us with an invaluable probe of the physical processes operating in galaxy clusters. \\ ( http://arxiv.org/abs/1002.4539 , 179kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4555 Date: Wed, 24 Feb 2010 14:45:56 GMT (2113kb) Title: On the chains of star complexes and superclouds in spiral arms Authors: Yuri N.Efremov Categories: astro-ph.CO Comments: 20 pages, 12 figures, accepted for publication in MNRAS \\ The relation is studied between occurrence of a regular chain of star complexes and superclouds in a spiral arm, and other properties of the latter. A regular string of star complexes is located in the north-western arm of M31; they have about the same size 0.6 kpc with spacing of 1.1 kpc. Within the same arm segment the regular magnetic field with the wavelength of 2.3 kpc was found by Beck et al. (1989). We noted that this wavelength is twice as large as the spacing between complexes and suggested that they were formed in result of magneto-gravitational instability developed along the arm. In this NW arm, star complexes are located inside the gas-dust lane, whilst in the south-western arm of M31 the gas-dust lane is upstream of the bright and uniform stellar arm. Earlier, evidence for the age gradient has been found in the SW arm. All these are signatures of a spiral shock, which may be associated with unusually large (for M31) pitch-angle of this SW arm segment. Such a shock may prevent the formation of the regular magnetic field, which might explain the absence of star complexes there. Anti-correlation between shock wave signatures and presence of star complexes is observed in spiral arms of a few other galaxies. Regular chains of star complexes and superclouds in spiral arms are rare, which may imply that a rather specific mechanism is involved in their formation, and the most probable one is the Parker-Jeans instability. The spiral pattern of our Galaxy is briefly discussed; it may be of M101 type in the outer parts. The regular bi-modal spacing of HI superclouds is found in Carina and Cygnus (Outer) arms, which may be an indirect evidence for the regular magnetic field along these arms. \\ ( http://arxiv.org/abs/1002.4555 , 2113kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4562 Date: Wed, 24 Feb 2010 15:22:10 GMT (427kb) Title: 3D simulations of wind-jet interaction in massive X-ray binaries Authors: M. Perucho, V. Bosch-Ramon and D. Khangulyan Categories: astro-ph.HE astro-ph.GA Comments: Accepted for publication in A&A Letters \\ High-mass microquasars may produce jets that will strongly interact with surrounding stellar winds on binary system spatial scales. We study the dynamics of the collision between a mildly relativistic hydrodynamical jet of supersonic nature and the wind of an OB star. We performed numerical 3D simulations of jets that cross the stellar wind with the code Ratpenat. The jet head generates a strong shock in the wind, and strong recollimation shocks occur due to the initial overpressure of the jet with its environment. These shocks can accelerate particles up to TeV energies and produce gamma-rays. The recollimation shock also strengthens jet asymmetric Kelvin-Helmholtz instabilities produced in the wind/jet contact discontinuity. This can lead to jet disruption even for jet powers of several times $10^{36}$ erg s$^{-1}$. High-mass microquasar jets likely suffer a strong recollimation shock that can be a site of particle acceleration up to very high energies, but also eventually lead to the disruption of the jet. \\ ( http://arxiv.org/abs/1002.4562 , 427kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4565 Date: Wed, 24 Feb 2010 15:46:21 GMT (127kb) Title: The Masses of the Milky Way and Andromeda galaxies Authors: L.L. Watkins (1), N.W. Evans (1), J. An (2) ((1)IoA, Cambridge, (2)NAO, Beijing, China) Categories: astro-ph.GA astro-ph.CO Comments: 15 pages, submitted to MNRAS \\ We present a family of robust tracer mass estimators to compute the enclosed mass of galaxy haloes from samples of discrete positional and kinematical data of tracers, such as halo stars, globular clusters and dwarf satellites. The data may be projected positions, distances, line of sight velocities or proper motions. Forms of the estimator tailored for the Milky Way galaxy and for M31 are given. Monte Carlo simulations are used to quantify the uncertainty as a function of sample size. For the Milky Way, the satellite sample consists of 26 galaxies with line-of-sight velocities. We find that the mass of the Milky Way within 300 kpc is ~ 0.9 x 10^12 solar masses assuming velocity isotropy. However, the mass estimate is sensitive to the anisotropy and could plausibly lie between 0.7 - 3.4 x 10^12 solar masses. Incorporating the proper motions of 6 Milky Way satellites into the dataset, we find ~ 1.4 x 10^12 solar masses. The range here if plausible anisotropies are used is still broader, from 1.2 - 2.7 x 10^12 solar masses. For M31, there are 23 satellite galaxies with measured line-of-sight velocities, but only M33 and IC 10 have proper motions. We use the line of sight velocities and distances of the satellite galaxies to estimate the mass of M31 within 300 kpc as ~ 1.4 x 10^12 solar masses assuming isotropy. There is only a modest dependence on anisotropy, with the mass varying between 1.3 -1.6 x 10^12 solar masses. Given the uncertainties, we conclude that the satellite data by themselves yield no reliable insights into which of the two galaxies is actually the more massive. \\ ( http://arxiv.org/abs/1002.4565 , 127kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4578 Date: Wed, 24 Feb 2010 16:37:44 GMT (4397kb,D) Title: Spatial distribution of interstellar dust in the Sun vicinity, comparison with neutral sodium-bearing gas Authors: Jean-Luc Vergely, Bernard Valette, Rosine Lallement, Severine Raimond Categories: astro-ph.GA Comments: 13 pages, 12 figures \\ 3D tomography of the interstellar dust and gas may be useful in many respects, from the physical and chemical evolution of the ISM itself to foreground decontamination of the CMB, or various studies of the environments of specific objects. Our goal here is to bring more precise information on the distance to nearby interstellar dust and gas clouds within 250 pc. We apply the best available calibration methods to a carefully screened set of stellar Stromgren photometry data for targets possessing a Hipparcos parallax and spectral type classification. We combine the derived interstellar extinctions and the parallax distances for about 6,000 stars to build a 3D tomography of the local dust. We use an inversion method based on a regularized Bayesian approach and a least squares criterion. We obtain 3D maps of the opacity and the distance to the main dust-bearing clouds with 250 pc. We calculate the integrated extinction between the Sun and the cube boundary and compare with the total galactic extinction derived from infrared 2D maps. We also compare the opacity distribution with the 3D distribution of interstellar neutral sodium resulting from the inversion of sodium columns towards about 1,700 target stars. Our maps show a larger high latitude dust opacity in the North compared to the South, while gas maps do not show the same asymmetry, suggesting a polar asymmetry of the dust to gas ratio at small distances. \\ ( http://arxiv.org/abs/1002.4578 , 4397kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4586 Date: Wed, 24 Feb 2010 17:05:40 GMT (3757kb,D) Title: Mathematical properties of the SimpleX algorithm Authors: C. J. H. Kruip, J.-P. Paardekooper, B. J. F. Clauwens, V. Icke Categories: astro-ph.IM astro-ph.CO physics.comp-ph Comments: 18 pages, 17 figures, accepted for publication in A&A \\ Context. Analytical and numerical analysis of the SimpleX radiative transfer algorithm, which features transport on a Delaunay triangulation. Aims. Verify whether the SimpleX radiative transfer algorithm conforms to mathematical expectations, to develop error analysis and present improvements upon earlier versions of the code. Methods. Voronoi-Delaunay tessellation, classical Markov theory. Results. Quantitative description of the error properties of the SimpleX method. Numerical validation of the method and verification of the analytical results. Improvements in accuracy and speed of the method. Conclusions. It is possible to transport particles such as photons in a physically correct manner with the SimpleX algorithm. This requires the use of weighting schemes or the modification of the point process underlying the transport grid. We have explored and applied several possibilities. \\ ( http://arxiv.org/abs/1002.4586 , 3757kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4588 Date: Wed, 24 Feb 2010 17:31:23 GMT (54kb) Title: Comment on Calculation of Positron Flux from Galactic Dark Matter Authors: Maxim Perelstein and Bibhushan Shakya Categories: astro-ph.HE astro-ph.CO hep-ph Comments: 18 pages, 6 figures \\ Energetic positrons produced in annihilation or decay of dark matter particles in the Milky Way can serve as an important indirect signature of dark matter. Computing the positron flux expected in a given dark matter model involves solving transport equations, which account for interaction of positrons with matter and galactic magnetic fields. Existing calculations solve the equations inside the diffusion zone, where galactic magnetic fields confine positrons, and assume vanishing positron density on the boundaries of this zone. However, in many models, a substantial fraction of the dark matter halo lies outside the diffusion zone. Positrons produced there can then enter the diffusion zone and get trapped, potentially reaching the Earth and increasing the expected flux. We calculate this enhancement for a variety of models. We also evaluate the expected enhancement of the flux of energetic photons produced by the inverse Compton scattering of the extra positrons on starlight and cosmic microwave background. We find maximal flux enhancements of order 20% in both cases. \\ ( http://arxiv.org/abs/1002.4588 , 54kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4605 Date: Wed, 24 Feb 2010 19:08:35 GMT (12kb,D) Title: Calculating the Hubble diagram by perturbation theory Authors: Gyula Bene Categories: astro-ph.CO \\ The effect of density fluctuations upon light propagation is calculated perturbatively in a matter dominated irrotational universe. The starting point is the perturbed metric (second order in the perturbation strength), while the output is the Hubble diagram. Density fluctuations cause this diagram to broaden to a strip. Moreover, the shift of the diagram mimics accelerated expansion. \\ ( http://arxiv.org/abs/1002.4605 , 12kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4608 Date: Wed, 24 Feb 2010 19:45:53 GMT (155kb) Title: WASP-12b as a prolate, inflated and disrupting planet from tidal dissipation Authors: Shu-lin Li (1,2), Neil Miller (3), Douglas N. C. Lin (1,3), and Jonathan J. Fortney (3) ((1) Kavli Institude for Astronomy and Astrophysics, Peking University Beijing, (2) Department of Astronomy, Peking University, Beijing, (3) UCSC) Categories: astro-ph.EP Comments: Accepted to Nature, 14 pages, 1 figure \\ The class of exotic Jupiter-mass planets that orbit very close to their parent stars were not explicitly expected before their discovery. The recently found transiting planet WASP-12b has a mass Mp = 1.4(+/-0.1) Jupiter masses (MJ), a mean orbital distance of only 3.1 stellar radii (meaning it is subject to intense tidal forces), and a period of 1.1 days. Its radius 1.79(+/- 0.09) RJ is unexpectedly large and its orbital eccentricity 0.049(+/-0:015) is even more surprising as such close orbits are in general quickly circularized. Here we report an analysis of its properties, which reveals that the planet is losing mass to its host star at a rate ~ 10^-7 MJ yr^-1. The planets surface is distorted by the stars gravity and the light curve produced by its prolate shape will differ by about ten per cent from that of a spherical planet. We conclude that dissipation of the stars tidal perturbation in the planets convective envelope provides the energy source for its large volume. We predict up to 10mJy CO band-head (2.292 micron) emission from a tenuous disk around the host star, made up of tidally stripped planetary gas. It may also contain a detectable resonant super-Earth, as a hypothetical perturber that continually stirs up WASP-12b's eccentricity. \\ ( http://arxiv.org/abs/1002.4608 , 155kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4610 Date: Wed, 24 Feb 2010 19:27:37 GMT (34kb,D) Title: Accelerating expansion in the swisscheese model Authors: Gyula Bene and Adelinda Csapo Categories: astro-ph.CO \\ A version of the swisscheese model is investigated. Nonoverlapping spheres are cut from a flat Friedmann-Robertson-Walker (FRW) universe. The mass they contained before is compressed within each sphere to a smaller sphere with homogeneous density distribution. Hence the inner spheres form sections of some closed FRW model. Between the outer and inner spheres there is a vacuum, where, due to spherical symmetry, the Schwarzschield metric describes the gravitational field. Within the inner spheres the closed FRW metric is valid, while outside the cut spheres the flat FRW metric is relevant. The metric and its first derivatives are continuous across the bordering surfaces of the different regions. We discuss this model in detail, and show that such a model universe can have a realistic density distribution on large scales, and exhibits accelerating expansion for a limited period of time. Especially, we determine the Hubble diagram and discuss its properties. \\ ( http://arxiv.org/abs/1002.4610 , 34kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4611 Date: Wed, 24 Feb 2010 19:28:35 GMT (84kb) Title: Barred Galaxies in the Coma Cluster Authors: Irina Marinova (UT Austin), Shardha Jogee (UT Austin), Neil Trentham (Cambridge), Henry C. Ferguson (STScI), Tim Weinzirl (UT Austin), Marc Balcells (Tenerife), David Carter (Liverpool), Mark den Brok (Kapteyn), Peter Erwin (MPIA), Alister W. Graham (Swinburne), Paul Goudfrooij (STScI), Rafael Guzman (Florida), Derek Hammer (Johns Hopkins), Carlos Hoyos (Florida), Reynier F. Peletier (Kapteyn), Avon P. Huxor (Bristol), Erik Peng (Peking University) and Gijs Verdoes Kleijn (Kapteyn) Categories: astro-ph.CO Comments: Proceedings of the Bash symposium, to appear in the Astronomical Society of the Pacific Conference Series, eds. L. Stanford, L. Hao, Y. Mao, J. Green \\ We use ACS data from the HST Treasury survey of the Coma cluster (z~0.02) to study the properties of barred galaxies in the Coma core, the densest environment in the nearby Universe. This study provides a complementary data point for studies of barred galaxies as a function of redshift and environment. From ~470 cluster members brighter than M_I = -11 mag, we select a sample of 46 disk galaxies (S0--Im) based on visual classification. The sample is dominated by S0s for which we find an optical bar fraction of 47+/-11% through ellipse fitting and visual inspection. Among the bars in the core of the Coma cluster, we do not find any very large (a_bar > 2 kpc) bars. Comparison to other studies reveals that while the optical bar fraction for S0s shows only a modest variation across low-to-intermediate density environments (field to intermediate-density clusters), it can be higher by up to a factor of ~2 in the very high-density environment of the rich Coma cluster core. \\ ( http://arxiv.org/abs/1002.4611 , 84kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4612 Date: Wed, 24 Feb 2010 19:29:03 GMT (1900kb) Title: Ionized gas, molecules, and dust in Sh2-132 Authors: J. Vasquez, C.E. Cappa, S. Pineault and N.U. Duronea Categories: astro-ph.GA Comments: 11 figures and 5 tables, accepted in MNRAS \\ We analyze the various interstellar components of the HII region Sh2-132. The main stellar source is the double binary system that includes the Wolf-Rayet star WR153ab. We use radio continuum images at 408 and 1420 MHz, and HI 21cm line data taken from the Canadian Galactic Plane Survey, molecular observations of the 12CO(1-0) line at 115 GHz from the Five College Radio Astronomy Observatory, and available mid and far IR observations obtained with the MSX and IRAS satellites, respectively. Sh2-132 is composed of two shells showing radio continuum counterparts at both frequencies. The emission is thermal in nature. The estimated rms electron density and ionized mass of the nebula are n_e = 20 cm^{-3} and M_HII = 1500 Mo. The distribution of the CO emission shows molecular gas bordering the ionized nebula and interacting with it. The velocities of the molecular gas is in the range --38 to --53 km/s, similar to the velocity of the ionized gas. The emission at 8.3 mic. reveals a ring like feature of about 15' that encircles the bright optical regions. This emission is due to the PAHs and marks the location of photodissociation regions. The gas distribution in the environs of Sh2-132 can be explained in a scenario where the massive stars in the region photodissociated, ionized, and swept-up the dense molecular material from the parental cloud through their strong stellar winds and intense UV photon flux. \\ ( http://arxiv.org/abs/1002.4612 , 1900kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4617 Date: Wed, 24 Feb 2010 20:52:29 GMT (363kb) Title: Coorbital Satellites of Saturn: Congenital Formation Authors: A. Izidoro, O.C. Winter, M. Tsuchida Categories: astro-ph.EP Comments: 10 pages, 9 figures, 4 tables \\ Saturn is the only known planet to have coorbital satellite systems. In the present work we studied the process of mass accretion as a possible mechanism for coorbital satellites formation. The system considered is composed of Saturn, a proto-satellite and a cloud of planetesimals distributed in the coorbital region around a triangular Lagrangian point. The adopted relative mass for the proto-satellite was 10^-6 of Saturn's mass and for each planetesimal of the cloud three cases of relative mass were considered, 10^-14, 10^-13 and 10^-12 masses of Saturn. In the simulations each cloud of planetesimal was composed of 10^3, 5 x 10^3 or 10^4 planetesimals. The results of the simulations show the formation of coorbital satellites with relative masses of the same order of those found in the saturnian system (10^-13 - 10^-9). Most of them present horseshoe type orbits, but a significant part is in tadpole orbit around L_4 or L_5. Therefore, the results indicate that this is a plausible mechanism for the formation of coorbital satellites. \\ ( http://arxiv.org/abs/1002.4617 , 363kb) %-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%- ------------------------------------------------------------------------------ \\ arXiv:0911.0288 (*cross-listing*) Date: Mon, 2 Nov 2009 10:59:21 GMT (751kb,D) Date (revised v2): Wed, 24 Feb 2010 14:43:03 GMT (905kb,D) Title: Classifying LISA gravitational wave burst signals using Bayesian evidence Authors: Farhan Feroz, Jonathan R. Gair, Philip Graff, Michael P Hobson and Anthony Lasenby Categories: gr-qc astro-ph.CO Comments: 21 pages, 11 figures, accepted by CQG; v2 has minor changes for consistency with accepted version \\ We consider the problem of characterisation of burst sources detected with the Laser Interferometer Space Antenna (LISA) using the multi-modal nested sampling algorithm, MultiNest. We use MultiNest as a tool to search for modelled bursts from cosmic string cusps, and compute the Bayesian evidence associated with the cosmic string model. As an alternative burst model, we consider sine-Gaussian burst signals, and show how the evidence ratio can be used to choose between these two alternatives. We present results from an application of MultiNest to the last round of the Mock LISA Data Challenge, in which we were able to successfully detect and characterise all three of the cosmic string burst sources present in the release data set. We also present results of independent trials and show that MultiNest can detect cosmic string signals with signal-to-noise ratio (SNR) as low as ~7 and sine-Gaussian signals with SNR as low as ~8. In both cases, we show that the threshold at which the sources become detectable coincides with the SNR at which the evidence ratio begins to favour the correct model over the alternative. \\ ( http://arxiv.org/abs/0911.0288 , 905kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4230 (*cross-listing*) Date: Tue, 23 Feb 2010 07:31:00 GMT (171kb) Title: A Couple of Issues Concerning Spinor Dark Energy Authors: Hao Wei Categories: gr-qc astro-ph.CO hep-ph hep-th Comments: 15 pages, 2 figures, revtex4 \\ Recently, the so-called Elko spinor field has been proposed to be a candidate of dark energy. It is a non-standard spinor and has unusual properties. When the Elko spinor field is used in cosmology, its unusual properties could bring some interesting consequences. In the present work, we consider two different issues concerning the dark energy model described by the Elko spinor fields. Firstly, we discuss the cosmological coincidence problem in the spinor dark energy model by using the dynamical system method. Our results show that the coincidence problem should be taken to heart in the investigations of spinor dark energy models. Next, we turn to another issue. In this work, we propose a simple method to reconstruct spinor dark energy from the cosmological observations. We find that this reconstruction method works fairly well. \\ ( http://arxiv.org/abs/1002.4230 , 171kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4278 (*cross-listing*) Date: Tue, 23 Feb 2010 09:27:12 GMT (149kb,D) Title: Entropic Accelerating Universe Authors: Damien A. Easson, Paul H. Frampton and George F. Smoot Categories: hep-th astro-ph.CO hep-ph Comments: 10 pages, 1 figure Report-no: IPMU 10-0036 \\ To accommodate the observed accelerated expansion of the universe, one popular idea is to invoke a driving term in the Friedmann-Lema\^{i}tre equation of dark energy which must then comprise 70% of the present cosmological energy density. We propose an alternative interpretation which takes into account the temperature intrinsic to the information holographically stored on the screen which is the surface of the universe. Dark energy is thereby obviated and the acceleration is due to an entropic force naturally arising from the information storage on a surface screen. We consider an additional quantitative approach based upon the entropy and surface terms usually neglected in General Relativity and show that this leads to the entropic accelerating universe. \\ ( http://arxiv.org/abs/1002.4278 , 149kb) ------------------------------------------------------------------------------ \\ arXiv:1002.4584 (*cross-listing*) Date: Wed, 24 Feb 2010 20:13:34 GMT (5kb) Title: On the Sackur-Tetrode equation of an expanding universe Authors: S. H. Pereira Categories: physics.gen-ph astro-ph.CO Comments: 7 pages \\ In this work we investigate the thermodynamic properties satisfied by an expanding universe filled with a monoatomic ideal gas. We show that the equations for the energy density, entropy density and chemical potential remain the same as the ideal gas. \\ ( http://arxiv.org/abs/1002.4584 , 5kb) %%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%% ------------------------------------------------------------------------------ \\ arXiv:0810.4852 replaced with revised version Wed, 24 Feb 2010 02:14:10 GMT (175kb) Title: Nearby Spiral Galaxy Globular Cluster Systems II: Globular Cluster Abundances in NGC 300 Authors: J. B. Nantais, J. P. Huchra, P. Barmby, K. A. G. Olsen Categories: astro-ph Comments: 36 pages, 15 figures, accepted to AJ; altered a second time according to referee-report so as to slightly change the criteria for GC selection \\ ( http://arxiv.org/abs/0810.4852 , 175kb) ------------------------------------------------------------------------------ \\ arXiv:0903.5308 replaced with revised version Wed, 24 Feb 2010 18:25:02 GMT (767kb) Title: Dynamical inference from a kinematic snapshot: The force law in the Solar System Authors: Jo Bovy (NYU), Iain Murray (Toronto), David W. Hogg (NYU, MPIA) Categories: astro-ph.EP astro-ph.GA gr-qc physics.class-ph physics.data-an Journal-ref: Astrophys.J.711:1157-1167,2010 DOI: 10.1088/0004-637X/711/2/1157 \\ ( http://arxiv.org/abs/0903.5308 , 767kb) ------------------------------------------------------------------------------ \\ arXiv:0906.4069 replaced with revised version Tue, 23 Feb 2010 21:17:22 GMT (2256kb) Title: Characterization of the BICEP Telescope for High-Precision Cosmic Microwave Background Polarimetry Authors: Y. D. Takahashi, P. A. R. Ade, D. Barkats, J. O. Battle, E. M. Bierman, J. J. Bock, H. C. Chiang, C. D. Dowell, L. Duband, E. F. Hivon, W. L. Holzapfel, V. V. Hristov, W. C. Jones, B. G. Keating, J. M. Kovac, C. L. Kuo, A. E. Lange, E. M. Leitch, P. V. Mason, T. Matsumura, H. T. Nguyen, N. Ponthieu, C. Pryke, S. Richter, G. Rocha, and K. W. Yoon Categories: astro-ph.CO Comments: 16 pages, 22 figures, updated to reflect published version Journal-ref: Astrophysical Journal 711 (2010) 1141-1156 DOI: 10.1088/0004-637X/711/2/1141 \\ ( http://arxiv.org/abs/0906.4069 , 2256kb) ------------------------------------------------------------------------------ \\ arXiv:0907.2941 (*cross-listing*) replaced with revised version Wed, 24 Feb 2010 17:57:16 GMT (609kb) Title: Tracking Quintessence and Cold Dark Matter Candidates Authors: S. Lola, C. Pallis and E. Tzelati Categories: hep-ph astro-ph.CO Comments: Final version Journal-ref: JCAP 0911:017,2009 DOI: 10.1088/1475-7516/2009/11/017 \\ ( http://arxiv.org/abs/0907.2941 , 609kb) ------------------------------------------------------------------------------ \\ arXiv:0908.4091 replaced with revised version Wed, 24 Feb 2010 03:04:10 GMT (430kb) Title: Star Cluster Candidates in M81 Authors: J. B. Nantais, J. P. Huchra, B. McLeod, J. Strader, J. P. Brodie Categories: astro-ph.CO Comments: 35 pages, 11 figures, submitted to AJ \\ ( http://arxiv.org/abs/0908.4091 , 430kb) ------------------------------------------------------------------------------ \\ arXiv:0909.2043 replaced with revised version Wed, 24 Feb 2010 17:09:42 GMT (375kb) Title: Models of Neptune-Mass Exoplanets: Emergent Fluxes and Albedos Authors: David S. Spiegel (1), Adam Burrows (1), Laurent Ibgui (1), Ivan Hubeny (2), and John A. Milsom (3) ((1)Princeton University, (2)Steward Observatory, (3)The University of Arizona) Categories: astro-ph.EP Comments: Accepted and Published in ApJ (2010 ApJ,709,149) \\ ( http://arxiv.org/abs/0909.2043 , 375kb) ------------------------------------------------------------------------------ \\ arXiv:0909.3026 (*cross-listing*) replaced with revised version Wed, 24 Feb 2010 18:17:11 GMT (685kb) Title: Cold Dark Matter in non-Standard Cosmologies, PAMELA, ATIC and Fermi LAT Authors: C. Pallis Categories: hep-ph astro-ph.CO Comments: Final version Journal-ref: Nucl.Phys.B831:217-247,2010 DOI: 10.1016/j.nuclphysb.2010.01.015 \\ ( http://arxiv.org/abs/0909.3026 , 685kb) ------------------------------------------------------------------------------ \\ arXiv:0909.4268 replaced with revised version Wed, 24 Feb 2010 20:14:33 GMT (67kb) Title: A NLTE model atmosphere analysis of the pulsating sdO star SDSS J1600+0748 Authors: M. Latour, G. Fontaine, P. Brassard, P. Chayer, E. M. Green Categories: astro-ph.SR Comments: 4 pages, 4 figures, accepted in Astrophysics and Space Science (24/02/2010), Special issue Hot sudbwarf stars \\ ( http://arxiv.org/abs/0909.4268 , 67kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5218 replaced with revised version Wed, 24 Feb 2010 00:26:44 GMT (190kb) Title: O-V-S-Z and friends: Non-Gaussianity from inhomogeneous reionization Authors: Rishi Khatri, Benjamin D. Wandelt Categories: astro-ph.CO Comments: Published version Journal-ref: ApJ 711 (2010) 1310 DOI: 10.1088/0004-637X/711/2/1310 \\ ( http://arxiv.org/abs/0910.5218 , 190kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5248 replaced with revised version Wed, 24 Feb 2010 09:57:11 GMT (867kb) Title: The Origin of Magnetic Fields in Galaxies Authors: Rafael S. de Souza, R. Opher Categories: astro-ph.CO astro-ph.GA Comments: 10 pages, 3 figures \\ ( http://arxiv.org/abs/0910.5248 , 867kb) ------------------------------------------------------------------------------ \\ arXiv:0911.0687 (*cross-listing*) replaced with revised version Wed, 24 Feb 2010 19:55:49 GMT (290kb) Title: Semi-Analytic Calculation of the Gravitational Wave Signal From the Electroweak Phase Transition for General Quartic Scalar Effective Potentials Authors: John Kehayias and Stefano Profumo Categories: hep-ph astro-ph.CO hep-th Comments: accepted by JCAP, revisions: removed turbulence contribution, minor changes to experimental sensitivity, fixed various minor typos and text revisions, added references, made it clear we consider only detonations; 17 pages, 4 figures, revtex4 \\ ( http://arxiv.org/abs/0911.0687 , 290kb) ------------------------------------------------------------------------------ \\ arXiv:0911.1274 (*cross-listing*) replaced with revised version Wed, 24 Feb 2010 02:39:27 GMT (40kb) Title: The importance of precession in modelling the direction of the final spin from a black-hole merger Authors: Enrico Barausse Categories: gr-qc astro-ph.CO astro-ph.GA Comments: 6 pages, 2 figures. Panel added to fig 2, discussion extended to comply with referee's comments. Version accepted for publication as proceeding of the 8th Amaldi International Conference on Gravitational Waves, NYC, 21-26 June 2009 \\ ( http://arxiv.org/abs/0911.1274 , 40kb) ------------------------------------------------------------------------------ \\ arXiv:0911.3327 replaced with revised version Wed, 24 Feb 2010 15:44:08 GMT (3527kb) Title: Simulating magnetic fields in the Antennae galaxies Authors: H. Kotarba, S. J. Karl, T. Naab, P. H. Johansson, K. Dolag, H. Lesch, F. A. Stasyszyn Categories: astro-ph.CO Comments: 16 pages, 13 figures, resubmitted after referee report \\ ( http://arxiv.org/abs/0911.3327 , 3527kb) ------------------------------------------------------------------------------ \\ arXiv:0912.2094 replaced with revised version Tue, 23 Feb 2010 22:44:26 GMT (309kb) Title: Cold Fronts from Shock Collisions Authors: Yuval Birnboim, Uri Keshet and Lars Hernquist Categories: astro-ph.CO astro-ph.HE Comments: 5 pages, 4 figures, Revised version \\ ( http://arxiv.org/abs/0912.2094 , 309kb) ------------------------------------------------------------------------------ \\ arXiv:0912.2119 replaced with revised version Wed, 24 Feb 2010 00:38:25 GMT (193kb) Title: Spectroscopy of M81 Globular Clusters Authors: Julie B. Nantais, John P. Huchra Categories: astro-ph.CO Comments: 46 pages, 15 figures, submitted to AJ \\ ( http://arxiv.org/abs/0912.2119 , 193kb) ------------------------------------------------------------------------------ \\ arXiv:0912.3385 replaced with revised version Wed, 24 Feb 2010 18:52:02 GMT (141kb) Title: Revised Results for Non-thermal Recombination Flare Hard X-Ray Emission Authors: J. C. Brown, P. C. V. Mallik, N. R. Badnell Categories: astro-ph.SR Comments: 6 pages, 8 figures, 1 table \\ ( http://arxiv.org/abs/0912.3385 , 141kb) ------------------------------------------------------------------------------ \\ arXiv:1001.1171 replaced with revised version Wed, 24 Feb 2010 02:42:15 GMT (2408kb) Title: A time-dependent radiative model for the atmosphere of the eccentric exoplanets Authors: N. Iro L. D. Deming Categories: astro-ph.EP Comments: Accepted for publication in the Astrophysical Journal (In Press) \\ ( http://arxiv.org/abs/1001.1171 , 2408kb) ------------------------------------------------------------------------------ \\ arXiv:1001.3140 replaced with revised version Wed, 24 Feb 2010 19:13:19 GMT (1810kb) Title: The Simultaneous Optical-to-X-ray Spectral Energy Distribution of Soft X-ray Selected AGN observed by Swift Authors: Dirk Grupe (PSU), S. Komossa (MPE), Karen M. Leighly (University of Oklahoma), and Kim L. Page (University of Leicester) Categories: astro-ph.CO Comments: 76 pages, 25 figures, 7 tables Journal-ref: 2010, ApJ Suppl, 187, 64 \\ ( http://arxiv.org/abs/1001.3140 , 1810kb) ------------------------------------------------------------------------------ \\ arXiv:1001.4580 replaced with revised version Wed, 24 Feb 2010 11:49:23 GMT (31kb) Title: Quasar variability limits on cosmological density of cosmic strings Authors: Artem Tuntsov (Sternberg Astronomical Institute), Maxim Pshirkov (Pushchino Radio Astronomy Observatory) Categories: astro-ph.CO gr-qc hep-ph Comments: 7 pages, 2 figures, accepted to Phys.Rev.D, no essential changes from v1. Based on the referee's feedback, a paragraph is added that emphasizes the value of the obtained limits to constrain the abundance and reconnection probabilities of fundamental (rather than topological) strings \\ ( http://arxiv.org/abs/1001.4580 , 31kb) ------------------------------------------------------------------------------ \\ arXiv:1001.4742 replaced with revised version Wed, 24 Feb 2010 17:51:50 GMT (223kb) Title: Searching for the inverse-Compton emission from bright cluster-centre radio galaxies Authors: M. J. Hardcastle and J. H. Croston Categories: astro-ph.CO astro-ph.HE Comments: 10 pages, 1 figure. Accepted for MNRAS. Updated version provides some missing references, no change to paper content \\ ( http://arxiv.org/abs/1001.4742 , 223kb) ------------------------------------------------------------------------------ \\ arXiv:1002.0150 replaced with revised version Tue, 23 Feb 2010 22:20:13 GMT (233kb) Title: The First Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope Authors: A. A. Abdo, for the Fermi-LAT Collaboration Categories: astro-ph.HE astro-ph.CO Comments: 68 pages, 28 figures; submitted to ApJ; electronic tables available by clicking the link in the top left of http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermilac.html \\ ( http://arxiv.org/abs/1002.0150 , 233kb) ------------------------------------------------------------------------------ \\ arXiv:1002.0723 replaced with revised version Wed, 24 Feb 2010 10:57:42 GMT (68kb) Title: A revision of the X-ray absorption nature of the BALQSOs Authors: A. Streblyanska, X. Barcons, F. J. Carrera and R. Gil-Merino Categories: astro-ph.CO astro-ph.HE Comments: Accepted by A&A. 12 pages, 8 figures. Added references and corrected typos \\ ( http://arxiv.org/abs/1002.0723 , 68kb) ------------------------------------------------------------------------------ \\ arXiv:1002.1080 replaced with revised version Wed, 24 Feb 2010 15:47:50 GMT (860kb) Title: J0454-0309: Evidence for a strong lensing fossil group falling into a poor galaxy cluster Authors: Mischa Schirmer (1), Sherry Suyu (1), Tim Schrabback (2), Hendrik Hildebrandt (2), Aleksi Halkola (3,4), Thomas Erben (1) ((1)Argelander-Institut fuer Astronomie, (2)Leiden Observatory, (3)University of Tuorla Observatory, (4)Excellence Cluster Universe Technische Universitaet Muenchen) Categories: astro-ph.CO Comments: 20 pages, 17 figures; Identical to the publication in A+A. Small language corrections. Minor additions: We check the influence of individual galaxy haloes to the external shear (Sect. 8.1.1). Alternative interpretation of the data: Galaxies ina filament projected along the l.o.s. fall into the fossil group (Section 8.1.2) \\ ( http://arxiv.org/abs/1002.1080 , 860kb) ------------------------------------------------------------------------------ \\ arXiv:1002.3966 replaced with revised version Tue, 23 Feb 2010 21:20:06 GMT (265kb,D) Title: Why all these prejudices against a constant? Authors: Eugenio Bianchi, Carlo Rovelli Categories: astro-ph.CO gr-qc hep-th Comments: 9 pages, 4 figures \\ ( http://arxiv.org/abs/1002.3966 , 265kb) %%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%--- For subscribe options to combined physics archives, e-mail To: physics@arXiv.org, Subject: subscribe ----------------------------------------------------------------------------- For help on viewing and making submissions, see http://arXiv.org/help/ For a list of archive mirror sites, see http://arXiv.org/servers.html ----------------------------------------------------------------------------- Third-party submissions cause excessive problems. Author self-submissions are exceedingly preferred. E-mail submissions have been discontinued in favor of better support for Web submissions. See http://arXiv.org/help/uploads