Date: Thu, 29 Oct 09 00:00:53 GMT Subject: astro-ph daily 42 new + 5 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 27 Oct 09 20:00:02 GMT to Wed 28 Oct 09 20:00:01 GMT ------------------------------------------------------------------------------ \\ arXiv:0910.5218 Date: Tue, 27 Oct 2009 20:16:45 GMT (189kb) Title: O-V-S-Z and friends: Non-Gaussianity from inhomogeneous reionization Authors: Rishi Khatri, Benjamin D. Wandelt Categories: astro-ph.CO Comments: Submitted \\ We calculate the cosmic microwave background (CMB) bispectrum due to inhomogeneous reionization. We calculate all the terms that can contribute to the bispectrum that are products of first order terms on all scales in conformal Newtonian gauge. We also correctly account for the de-correlation between the matter density and initial conditions using perturbation theory up to third order. We find that the bispectrum is of local type as expected. For a reasonable model of reionization, in which the Universe is completely ionized by redshift z_{ri} ~ 8 with optical depth to the last scattering surface \tau_0=0.087 the signal to noise for detection of the CMB temperature bispectrum is S/N ~ 0.02 and confusion in the estimation of primordial non-Gaussianity is f_{NL} ~ -0.1. For an extreme model with z_{ri} ~ 12.5, \tau_0=0.14 we get S/N ~ 0.3 and f_{NL} ~ -0.2. \\ ( http://arxiv.org/abs/0910.5218 , 189kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5219 Date: Wed, 28 Oct 2009 18:47:19 GMT (1284kb,D) Title: A Weak Lensing Study of X-ray Groups in the COSMOS survey: Form and Evolution of the Mass-Luminosity Relation Authors: A. Leauthaud, A. Finoguenov, J. E. Taylor, R. Massey, J. Rhodes, O. Ilbert, K. Bundy, J. Tinker, M. R. George, P. Capak, A. M. Koekemoer, D. E. Johnston, N. Cappelluti, R. S. Ellis, M. Elvis, C. Heymans, O. Le Fevre, S. Lilly, H. J. McCraken, Y. Mellier, A. Refregier, M. Salvato, N. Scoville, G. Smoot, M. Tanaka, L. Van Waerbeke, M. Wolk Categories: astro-ph.CO Comments: 20 pages, 9 figures, 1 table. Submitted to ApJ. Including referee's comments \\ Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray selected galaxy groups to investigate the scaling relation between X-ray luminosity (Lx) and halo mass (M00) where M200 is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 square degrees of contiguous imaging with the Advanced Camera for Surveys (ACS) and deep XMM-Newton/Chandra imaging. The combined depth of these two data-sets allows us to probe the lensing signals of X-ray detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law, M200 ~ Lx^a, with a slope of a=0.66+-0.14. These results significantly extend the dynamic range for which the halo masses of X-ray structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-Lx relation. The combination of our group data with previously published cluster data demonstrates that the M-Lx relation is well described by a single power law, a=0.64+-0.03, over two decades in mass, 10^13.5-10^15.5 h72^-1 Msun. These results are inconsistent at the 3.7 level with the self-similar prediction of a=0.75. We examine the redshift dependence of the M-Lx relation and find little evidence for evolution beyond the rate predicted by self-similarity from z ~ 0.25 to z ~ 0.8. \\ ( http://arxiv.org/abs/0910.5219 , 1284kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5220 Date: Wed, 28 Oct 2009 11:44:36 GMT (804kb) Title: Cosmological perturbation theory for baryons and dark matter I: one-loop corrections in the RPT framework Authors: Gabor Somogyi (DESY, UZurich) and Robert E. Smith (UZurich) Categories: astro-ph.CO Comments: 37 pages, 14 figures. Submitted for publication in PRD \\ We generalize the `renormalized' perturbation theory (RPT) formalism of Crocce & Scoccimarro (2006a) to deal with multiple fluids in the Universe and here we present calculations up to the one-loop level. We apply the approach to the non-linear evolution of baryon and cold dark matter (CDM) perturbations, evolving from distinct sets of initial conditions. In current models of structure formation, it is standard practice to treat baryons and CDM as an effective single component fluid. In this approximation, one uses a weighed sum of late-time baryon and CDM transfer functions to set initial conditions. Here, we explore whether this approach can be used for high precision work. We show that, even for a pure linear treatment, there is a large-scale scale-dependent bias between baryons and CDM for WMAP5 cosmology. This bias is >1% until the present day, when it is driven towards unity through gravitational relaxation. Using the RPT formalism we test this approximation in the non-linear regime, and show that the CDM power spectrum in the 2-component fluid differs from that obtained from a 1-component fluid by ~3% on scales of order k~0.05 h/Mpc at z=10, and by ~0.5% at z=0. However, for the case of baryons the situation is worse and we find that the power spectrum is suppressed by ~15% on scales k~0.05 h/Mpc at z=10, and by ~3-5% at z=0, relative to the total matter. Importantly, besides the suppression of the spectrum, baryonic acoustic oscillations (BAO) are amplified for baryon and damped for CDM spectra. Thus, high precision modeling of baryons can not be probed through CDM only simulations; detection significance of BAO will be amplified in probes that study baryonic matter. Total mass can be modeled accurately using a 1-component fluid approach at all times. (Abridged) \\ ( http://arxiv.org/abs/0910.5220 , 804kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5221 Date: Wed, 28 Oct 2009 10:02:34 GMT (917kb) Title: Relic density and CMB constraints on dark matter annihilation with Sommerfeld enhancement Authors: Jesus Zavala (1), Mark Vogelsberger (1,2) and Simon D. M. White (1) ((1) MPA, (2) Harvard/CfA) Categories: astro-ph.CO Comments: 9 pages, 6 figures, submitted to Physical Review D. Website with online tools for Sommerfeld-related calculations can be found at http://www.mpa-garching.mpg.de/~vogelsma/sommerfeld/ \\ We calculate how the relic density of dark matter particles is altered when their annihilation is enhanced by the Sommerfeld mechanism due to a Yukawa interaction between the annihilating particles. Maintaining a dark matter abundance consistent with current observational bounds requires the normalization of the s-wave annihilation cross section to be decreased compared to a model without enhancement. The level of suppression depends on the specific parameters of the particle model, with the kinetic decoupling temperature having the most effect. We find that the cross section can be reduced by as much as an order of magnitude for extreme cases. We also compute the mu-type distortion of the CMB energy spectrum caused by energy injection from such Sommerfeld-enhanced annihilation. Our results indicate that in the vicinity of resonances, associated with bound states, distortions can be large enough to be excluded by the upper limit |mu|<9.0x10^(-5) found by the COBE/FIRAS experiment. \\ ( http://arxiv.org/abs/0910.5221 , 917kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5223 Date: Tue, 27 Oct 2009 23:31:29 GMT (971kb) Title: Hubble Space Telescope Optical Imaging of the Eroding Debris Disk HD 61005 Authors: H. L. Maness, P. Kalas, K. M. G. Peek, E. I. Chiang, K. Scherer, M. P. Fitzgerald, James R. Graham, D. C. Hines, G. Schneider, S. A. Metchev Categories: astro-ph.EP Comments: 18 pages, 17 figures; Accepted to ApJ: 26 October 2009 \\ We present Hubble Space Telescope optical coronagraphic polarization imaging observations of the dusty debris disk HD 61005. The scattered light intensity image and polarization structure reveal a highly inclined disk with a clear asymmetric, swept back component, suggestive of significant interaction with the ambient interstellar medium. The combination of our new data with the published 1.1 micron discovery image shows that the grains are blue scattering with no strong color gradient as a function of radius, implying predominantly sub-micron sized grains. We investigate possible explanations that could account for the observed swept back, asymmetric morphology. Previous work has suggested that HD 61005 may be interacting with a cold, unusually dense interstellar cloud. However, limits on the intervening interstellar gas column density from an optical spectrum of HD 61005 in the Na I D lines render this possibility unlikely. Instead, HD 61005 may be embedded in a more typical warm, low-density cloud that introduces secular perturbations to dust grain orbits. This mechanism can significantly distort the ensemble disk structure within a typical cloud crossing time. For a counterintuitive relative flow direction--parallel to the disk midplane--we find that the structures generated by these distortions can very roughly approximate the HD 61005 morphology. Future observational studies constraining the direction of the relative interstellar medium flow will thus provide an important constraint for future modeling. Independent of the interpretation for HD 61005, we expect that interstellar gas drag likely plays a role in producing asymmetries observed in other debris disk systems, such as HD 15115 and Delta-Velorum. \\ ( http://arxiv.org/abs/0910.5223 , 971kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5224 Date: Tue, 27 Oct 2009 20:02:23 GMT (2210kb) Title: Baryon Acoustic Oscillations Authors: Bruce A. Bassett (SAAO & UCT), Ren\'ee Hlozek (Oxford) Categories: astro-ph.CO Comments: 42 Pages, 21 colour figures. Extended version of chapter contributed to the book "Dark Energy", Ed. P. Ruiz-Lapuente, Cambridge University Press. Comments and suggested references welcomed. Supplementary slides available at http://cosmology.org.za/BAO_review_slides.ppt Journal-ref: Dark Energy, Ed. P. Ruiz-Lapuente (2010, ISBN-13: 9780521518888) \\ Baryon Acoustic Oscillations (BAO) are frozen relics left over from the pre-decoupling universe. They are the standard rulers of choice for 21st century cosmology, providing distance estimates that are, for the first time, firmly rooted in well-understood, linear physics. This review synthesises current understanding regarding all aspects of BAO cosmology, from the theoretical and statistical to the observational, and includes a map of the future landscape of BAO surveys, both spectroscopic and photometric. \\ ( http://arxiv.org/abs/0910.5224 , 2210kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5225 Date: Tue, 27 Oct 2009 20:23:39 GMT (96kb) Title: V371 Per - A Thick-Disk, Short-Period F/1O Cepheid Authors: Patrick Wils, Arne A. Henden, Stelios Kleidis, E.G. Schmidt, Doug L. Welch Categories: astro-ph.SR Comments: Accepted for publication in MNRAS \\ V371 Per was found to be a double-mode Cepheid with a fundamental mode period of 1.738 days, the shortest among Galactic beat Cepheids, and an unusually high period ratio of 0.731, while the other Galactic beat Cepheids have period ratios between 0.697 and 0.713. The latter suggests that the star has a metallicity [Fe/H] between -1 and -0.7. The derived distance from the Galactic Plane places it in the Thick Disk or the Halo, while all other Galactic beat Cepheids belong to the Thin Disk. There are indications from historical data that both the fundamental and first overtone periods have lengthened. \\ ( http://arxiv.org/abs/0910.5225 , 96kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5227 Date: Tue, 27 Oct 2009 20:10:10 GMT (333kb) Title: Effects of the Non-Equipartition of Electrons and Ions in the Outskirts of Relaxed Galaxy Clusters Authors: Ka-Wah Wong, Craig L. Sarazin (Univ. of Virginia) Categories: astro-ph.CO astro-ph.HE Comments: 28 pages, 19 figures, accepted for publication in the Astrophysical Journal \\ (abridged) We have studied the effects of electron-ion non-equipartition in the outer regions of relaxed clusters for a wide range of masses in the \LambdaCDM cosmology using one-dimensional hydrodynamic simulations. The effects of the non-adiabatic electron heating efficiency, \beta, on the degree of non-equipartition are also studied. Using the gas fraction f_gas = 0.17 (which is the upper limit for a cluster), we give a conservative lower limit of the non-equipartition effect on clusters. Beyond the virial radius, the non-equipartition effect depends rather strongly on \beta, and such a strong dependence at the shock radius can be used to distinguish shock heating models or constrain the shock heating efficiency of electrons. We have also studied systematically the signatures of non-equipartition on X-ray and SZ observables. We have calculated the effect of non-equipartition on the projected temperature and X-ray surface brightness profiles using the MEKAL emission model. The non-equipartition effect can introduce a ~10% bias in the projected temperature at R_vir for a wide range of \beta. We also found that the effect of non-equipartition on the projected temperature profiles can be enhanced by increasing metallicity. We found that for our model in the \LambdaCDM Universe, the integrated SZ bias, Y_{non-eq}/Y_{eq}, evolves slightly (at a percentage level) with redshift, which is in contrast to the self-similar model in the Einstein-de Sitter Universe. This may introduce biases in cosmological studies using the f_gas technique. We discussed briefly whether the equipartition and non-equipartition models near the shock region can be distinguished by future radio observations with, for example, ALMA. \\ ( http://arxiv.org/abs/0910.5227 , 333kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5233 Date: Wed, 28 Oct 2009 04:42:56 GMT (2427kb) Title: Hydrogen Self Shielding in a Quasar Proximity Zone Authors: Gabriel Altay, Rupert A. C. Croft, Tiziana Di Matteo Categories: astro-ph.CO astro-ph.GA Comments: 15 pages, 16 figures. High resolution figures available at http://gabriel-altay.wikidot.com/quasprox. Comments welcome \\ We calculate the distribution of HI within 750 proper kpc/h of a quasar, Lbol = 1.62e13 Lsun, powered by an SMBH, Mbh = 4.47e8 Msun, at z = 3. Our numerical model includes a cosmological hydrodynamic simulation that tracks the self consistent growth and thermal feedback of black holes calculated using GADGET-3 as well as a detailed post-processing ray tracing treatment of the non-uniform ionizing radiation field calculated using SPHRAY, which naturally accounts for the self shielding of optically thick systems. We show that the correct treatment of self shielding introduces a flattening feature into the neutral column density distribution around Log NHI = 20 and that regions with the lowest neutral fractions are not those with the highest density gas. For comparison, we solve a Ricatti equation which determines the equilibrium Hydrogen ionization fractions in the presence of a radiation field that falls off as 1/r^2 with regions above a given gas density threshold completely shielded from ionizing radiation. We demonstrate that these semi analytic models cannot reproduce the HI field calculated using SPHRAY. We conclude by comparing our models of this single proximity zone to observations by Hennawi and Prochaska of the absorption spectra of background quasars which are coincident on the sky with foreground quasars in their Quasars Probing Quasars (QPQ) series of papers. Compared to the QPQ sample, we find a factor of 3 fewer optically thick (Log NHI > 17.2) systems around our quasar, however the dark matter halo that hosts our simulated quasar, Mhalo = 5.25e12 Msun, is less massive than the typical QPQ host halo by a factor of four. Allowing for a linear scaling between halo mass, baryonic overdensity and number of absorbers, we estimate the typical host halo mass in the QPQ sample as 1.92e13 Msun. \\ ( http://arxiv.org/abs/0910.5233 , 2427kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5246 Date: Tue, 27 Oct 2009 21:47:21 GMT (57kb) Title: Large-Scale Fluctuations in the HeII Lyman-alpha Forest and HeII Reionization Authors: Steven Furlanetto, Keri Dixon (UCLA) Categories: astro-ph.CO Comments: 11 pages, 4 figures, submitted to ApJ \\ We examine large-scale fluctuations in the HeII Lyman-alpha forest transmission during and after HeII reionization. We use a simple Monte Carlo model to distribute quasars throughout a large volume and compute the resulting radiation field along one-dimensional skewers. In agreement with previous studies, we find that the rarity of these sources induces order unity fluctuations in the mean optical depth after reionization, even when averaged over large segments (~10-100 Mpc across). We compare our models to existing data along five HeII Lyman-alpha forest lines of sight spanning z~2-3.2. The large cosmic variance contained in our model plausibly explains many of the observed fluctuations at z<2.5. But our models cannot accommodate the large fluctuations toward high optical depths on ~30 Mpc scales observed at z~2.7-2.9, and the measured optical depths (tau>4) at z>2.9 are difficult to explain with a smoothly-evolving mean radiation field. In order to better understand this data, we construct a toy model of HeII reionization, in which we assume that regions with the smallest radiation fields in a post-reionization Universe (or farthest from strong ionizing sources) are completely dark during reionization. The observed fluctuations fit much more comfortably into this model, and we therefore argue that, according to present data, HeII reionization does not complete until z<2.9. \\ ( http://arxiv.org/abs/0910.5246 , 57kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5248 Date: Tue, 27 Oct 2009 21:33:03 GMT (871kb) Title: The Origin of Magnetic Fields in Galaxies Authors: Rafael da Silva de Souza, Reuven Opher Categories: astro-ph.CO astro-ph.GA Comments: 18 pages, 3 figures \\ Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We showed that the natural plasma fluctuations in the primordial universe, produces random dipole magnetic fields of comoving size $\sim 1$ pc and intensity $\sim 0.1 \mu G$ at a redshift \emph{z} $\sim$ 10. The theory predicts an average magnetic field $\sim 0.003 ~ nG$ over a 2 kpc region at \emph{z} $\sim 10$. We assume this seed field and examine its amplification by a turbulent dynamo in a protogalaxy. Whereas the standard $\alpha-\Omega$ dynamo for a typical disk galaxy creates only a 2 e-fold amplification of the field in $\sim 10^{9}$ years, the turbulent dynamo has a much shorter amplification time. Starting with the average seed magnetic field of $B\sim 0.003 nG$ over $\sim 2$ kpc at \emph{z} = 10, we find that in $10^{9}$ years, $B$ is amplified to $\sim 1 nG$. This corresponds to a $\sim 6$ e-fold amplification of the field. In the process of collapsing to form galaxies at $\emph{z}\sim10$, the plasma density rises by a factor of $\sim 200$ and the magnetic fields, by a factor of $\sim 34$. Thus, $0.03 \mu G$ fields over 0.34 kpc regions in galaxies are predicted. If the dipole magnetic fields predicted by the Fluctuation-Dissipation-Theorem are not completely random, microgauss fields over regions $\gtrsim 0.34$ kpc are easily obtained. The model is thus a strong candidate for resolving the problem of the origin of magnetic fields in $\lesssim 10^{9}$ years in high redshift galaxies. \\ ( http://arxiv.org/abs/0910.5248 , 871kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5253 Date: Tue, 27 Oct 2009 21:57:43 GMT (81kb) Title: The first accurate parallax distance to a black hole Authors: J. C. A. Miller-Jones (1), P. G. Jonker (2,3), V. Dhawan (1), W. Brisken (1), M. P. Rupen (1), G. Nelemans (4), E. Gallo (5) ((1) NRAO, (2) SRON, (3) CfA, (4) Nijmegen, (5) MIT) Categories: astro-ph.HE Comments: Accepted for publication in ApJ Letters. 6 pages, 2 figures \\ Using astrometric VLBI observations, we have determined the parallax of the black hole X-ray binary V404 Cyg to be 0.418 +/- 0.024 milliarcseconds, corresponding to a distance of 2.39 +/- 0.14 kpc, significantly lower than the previously accepted value. This model-independent estimate is the most accurate distance to a Galactic stellar-mass black hole measured to date. With this new distance, we confirm that the source was not super-Eddington during its 1989 outburst. The fitted distance and proper motion imply that the black hole in this system likely formed in a supernova, with the peculiar velocity being consistent with a recoil (Blaauw) kick. The size of the quiescent jets inferred to exist in this system is less than 1.4 AU at 22 GHz. Astrometric observations of a larger sample of such systems would provide useful insights into the formation and properties of accreting stellar-mass black holes. \\ ( http://arxiv.org/abs/0910.5253 , 81kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5256 Date: Tue, 27 Oct 2009 22:03:25 GMT (1687kb) Title: The power output of local obscured and unobscured AGN: crossing the absorption barrier with Swift/BAT and IRAS Authors: R. V. Vasudevan, A. C. Fabian, P. Gandhi, L. M. Winter, R. F. Mushotzky Categories: astro-ph.GA astro-ph.HE Comments: 19 pages, 16 figures, 2 tables. Accepted for publication in MNRAS \\ The Swift/BAT 9-month catalogue of active galactic nuclei (AGN) provides an unbiased census of local supermassive black hole accretion, and probes to all but the highest levels of absorption in AGN. We explore a method for characterising the bolometric output of both obscured and unobscured AGN by combining the hard X-ray data from Swift/BAT (14-195keV) with the reprocessed IR emission as seen with the IRAS all-sky surveys. This approach bypasses the complex modifications to the SED introduced by absorption in the optical, UV and 0.1-10 keV regimes and provides a long-term, average picture of the bolometric output of these sources. We broadly follow the approach of Pozzi et al. for calculating the bolometric luminosities by adding nuclear IR and hard X-ray luminosities, and consider different approaches for removing non-nuclear contamination in the large-aperture IRAS fluxes. Using mass estimates from the M_BH-L_bulge relation, we present the Eddington ratios \lambda_Edd and 2-10 keV bolometric corrections for a subsample of 63 AGN (35 obscured and 28 unobscured) from the Swift/BAT catalogue, and confirm previous indications of a low Eddington ratio distribution for both samples. Importantly, we find a tendency for low bolometric corrections (typically 10-30) for the obscured AGN in the sample (with a possible rise from ~15 for \lambda_Edd<0.03 to ~32 above this), providing a hitherto unseen window onto accretion processes in this class of AGN. This finding is of key importance in calculating the expected local black hole mass density from the X-ray background since it is composed of emission from a significant population of such obscured AGN. Analogous studies with high resolution IR data and a range of alternative models for the torus emission will form useful future extensions to this work. (Abridged) \\ ( http://arxiv.org/abs/0910.5256 , 1687kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5258 Date: Tue, 27 Oct 2009 22:06:26 GMT (39kb) Title: Origin of $10^{15}-10^{16}$G Magnetic Fields in the Central Engine of Gamma Ray Bursts Authors: Rafael da Silva de Souza, Reuven Opher Categories: astro-ph.HE Comments: 9 pages \\ Various authors have suggested that the gamma-ray burst (GRB) central engine is a rapidly rotating, strongly magnetized, $(\sim 10^{15}-10^{16}$ G) compact object. The strong magnetic field can accelerate and collimate the relativistic flow and the rotation of the compact object can be the energy source of the GRB. The major problem in this scenario is the difficulty of finding an astrophysical mechanism for obtaining such intense fields. Whereas, in principle, a neutron star could maintain such strong fields, it is difficult to justify a scenario for their creation. If the compact object is a black hole, the problem is more difficult since, according to general relativity it has "no hair" (i.e., no magnetic field). Schuster, Blackett, Pauli, and others have suggested that a rotating neutral body can create a magnetic field by non-minimal gravitational-electromagnetic coupling (NMGEC). The Schuster-Blackett form of NMGEC was obtained from M{\o}ller's tetrad theory of gravitation (MTTG). We call the general theory NMGEC-MTTG. We investigate here the possible origin of the intense magnetic fields $\sim 10^{15}-10^{16}$ G in GRBs by NMGEC-MTTG. Whereas these fields are difficult to explain astrophysically, we find that they are easily explained by NMGEC-MTTG. It not only explains the origin of the $\sim 10^{15}-10^{16}$G fields when the compact object is a neutron star, but also when it is a black hole. \\ ( http://arxiv.org/abs/0910.5258 , 39kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5267 Date: Wed, 28 Oct 2009 17:12:13 GMT (225kb) Title: Continuum Observations at 350 Microns of High-Redshift Molecular Emission Line Galaxies Authors: Jingwen Wu (CFA), Paul Vanden Bout (NRAO), Neal Evans, Michael Dunham (UTexas, Austin) Categories: astro-ph.CO Comments: 17 pages, 8 figures. Accepted by ApJ \\ We report observations of 15 high redshift (z = 1-5) galaxies at 350 microns using the Caltech Submillimeter Observatory and SHARC-II array detector. Emission was detected from eight galaxies, for which far-infrared luminosities, star formation rates, total dust masses, and minimum source size estimates are derived. These galaxies have star formation rates and star formation efficiencies comparable to other high redshift molecular emission line galaxies. The results are used to test the idea that star formation in these galaxies occurs in a large number of basic units, the units being similar to star-forming clumps in the Milky Way. The luminosity of these extreme galaxies can be reproduced in a simple model with (0.9-30) *10^6 dense clumps, each with a luminosity of 5 *10^5 Lsun, the mean value for such clumps in the Milky Way. Radiative transfer models of such clumps can provide reasonable matches to the overall SEDs of the galaxies. They indicate that the individual clumps are quite opaque in the far-infrared. Luminosity to mass ratios vary over two orders of magnitude, correlating strongly with the dust temperature derived from simple fits to the SED. The gas masses derived from the dust modeling are in remarkable agreement with those from CO luminosities, suggesting that the assumptions going into both calculations are reasonable. \\ ( http://arxiv.org/abs/0910.5267 , 225kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5268 Date: Wed, 28 Oct 2009 00:22:28 GMT (1160kb) Title: Monte Carlo simulations of air showers in atmospheric electric fields Authors: S. Buitink, T. Huege, H. Falcke, D. Heck and J. Kuijpers Categories: astro-ph.HE Comments: 24 pages, 19 figures, accepted for publication in Astroparticle Physics \\ The development of cosmic ray air showers can be influenced by atmospheric electric fields. Under fair weather conditions these fields are small, but the strong fields inside thunderstorms can have a significant effect on the electromagnetic component of a shower. Understanding this effect is particularly important for radio detection of air showers, since the radio emission is produced by the shower electrons and positrons. We perform Monte Carlo simulations to calculate the effects of different electric field configurations on the shower development. We find that the electric field becomes important for values of the order of 1 kV/cm. Not only can the energy distribution of electrons and positrons change significantly for such field strengths, it is also possible that runaway electron breakdown occurs at high altitudes, which is an important effect in lightning initiation. \\ ( http://arxiv.org/abs/0910.5268 , 1160kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5269 Date: Wed, 28 Oct 2009 00:23:11 GMT (520kb) Title: IRAS 16293: A "Magnetic" Tale of Two Cores Authors: Ramprasad Rao (ASIAA), Josep Miquel Girart (CSIC-IEEC), Daniel P. Marrone (NRAO Jansky Fellow/U. Chicago), Shih-Ping Lai (National Tsing-Hua University) and Scott Schnee (NRC-HIA) Categories: astro-ph.GA Comments: Accepted by The Astrophysical Journal (ApJ). Consists of 37 pages with 9 figures and 5 tables. Abstract below is abridged \\ We present polarization observations of the dust continuum emission from IRAS 16293 which is a Class 0 protostar and is known to have at least two components, source A and B. These measurements were conducted by the Submillimeter Array (SMA) at a frequency of ~341 GHz and with high angular resolution (~2-3 arcseconds). We find that the large scale global direction of the field, which is perpendicular to the observed polarization, appears to be along the dust ridge where the emission peaks. On smaller scales we find that the field structure is significantly different for the two components of the binary. The first component, source A, shows a magnetic field structure which is "hourglass" shaped as predicted from theoretical models of low mass star formation in the presence of strong magnetic fields. However, the other component, source B, shows a relatively ordered magnetic field with no evidence of any deformation. There is an observed decrease in polarization towards the center. Our calculations show that in IRAS 16293 the magnetic energy is stronger than the turbulent energy but is approximately similar to the centrifugal energy. Our results provide additional evidence to show that the two protostars appear to be in different stages during their evolution. \\ ( http://arxiv.org/abs/0910.5269 , 520kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5274 Date: Wed, 28 Oct 2009 01:32:29 GMT (1918kb) Title: A General Catalogue of Molecular Hydrogen Emission-Line Objects (MHOs) in Outflows from Young Stars Authors: Christopher J. Davis, Ryan Gell, Tigran Khanzadyan, Michael D. Smith, Tim Jenness Categories: astro-ph.SR Comments: 8 Pages, 5 figures. Also 23 appendix pages containing 15 landscape appendix tables (uses rotate.sty). Searchable catalogue/Data tables available from http://www.jach.hawaii.edu/UKIRT/MHCat/ \\ We present a catalogue of Molecular Hydrogen emission-line Objects (MHOs) in outflows from embedded young stars. All objects are identified in the near-infrared lines of molecular hydrogen, all reside in the Milky Way, and all are associated with jets or molecular outflows from young stars. Objects in both low and high-mass star forming regions are included. This catalogue complements the existing database of Herbig-Haro objects; indeed, for completeness, HH objects that are detected in H2 emission are included in the MHO catalogue. \\ ( http://arxiv.org/abs/0910.5274 , 1918kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5280 Date: Wed, 28 Oct 2009 19:47:48 GMT (77kb) Title: Non-Gaussian Probability Distribution for the CMB Angular Power Spectra? Authors: Alexey Golovnev Categories: astro-ph.CO Comments: A contribution to Proceedings of the International Workshop on Cosmic Structure and Evolution, September 23-25, 2009, Bielefeld, Germany. 6 pages, 1 figure \\ This is my contribution to Proceedings of the International Workshop on Cosmic Structure and Evolution, September 23-25, 2009, Bielefeld, Germany. In my talk I presented some non-Gaussian features of the foreground reduced WMAP five year full sky temperature maps, which were recently reported in arXiv:0906.4954 paper by V.Vanchurin. And in these notes I first discuss the statistics behind this analysis in some detail. Then I describe invaluable insights which I got from discussions after my talk on the Workshop. And finally I explain why, in my current opinion, the signal detected in arXiv:0906.4954 can hardly have something to do with cosmological perturbations, but rather it presents a fancy measurement of the Milky Way angular width in the microwave frequency range. \\ ( http://arxiv.org/abs/0910.5280 , 77kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5282 Date: Wed, 28 Oct 2009 03:09:18 GMT (675kb) Title: Upper Limits on the Number of Small Bodies in Sedna-Like Orbits by the TAOS Project Authors: J.-H. Wang, M. J. Lehner, Z.-W. Zhang, F. B. Bianco, C. Alcock, W.-P. Chen, T. Axelrod, Y.-I. Byun, N. K. Coehlo, K. H. Cook, R. Dave, I. de Pater, R. Porrata, D.-W. Kim, S.-K. King, T. Lee, H.-C. Lin, J. J. Lissauer, S. L. Marshall, P. Protopapas, J. A. Rice, M. E. Schwamb, S.-Y. Wang and C.-Y. Wen Categories: astro-ph.EP Comments: 25 pages, 13 figures \\ We present the results of a search for occultation events by objects at distances between 100 and 1000 AU in lightcurves from the Taiwanese-American Occultation Survey (TAOS). We searched for consecutive, shallow flux reductions in the stellar lightcurves obtained by our survey between 7 February 2005 and 31 December 2006 with a total of $\sim4.5\times10^{9}$ three-telescope simultaneous photometric measurements. No events were detected, allowing us to set upper limits on the number density as a function of size and distance of objects in Sedna-like orbits, using simple models. \\ ( http://arxiv.org/abs/0910.5282 , 675kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5291 Date: Wed, 28 Oct 2009 05:02:23 GMT (50kb) Title: The newly born magnetars powering gamma-ray burst internal-plateau emission: are there strange stars? Authors: Yun-Wei Yu, Xiao-Feng Cao, Xiao-Ping Zheng Categories: astro-ph.HE Comments: 5 pages, 2 figures, accepted for publication in ApJ Letters \\ The internal-plateau X-ray emission of gamma-ray bursts (GRBs) indicates that a newly born magnetar could be the central object of some GRBs. The observed luminosity and duration of the plateaus suggest that, for such a magnetar, a rapid spin with a sub- or millisecond period is sometimes able to last thousands of seconds. In this case, the conventional neutron star (NS) model for the magnetar may be challenged, since the rapid spin of nascent NSs would be remarkably decelerated within hundreds of seconds due to r-mode instability. In contrast, the r-modes can be effectively suppressed in nascent strange stars (SSs). In other words, to a certain extent, only SSs can keep nearly-constant extremely-rapid spin for a long period of time during the early ages of the stars. We thus propose that the sample of the GRB rapidly-spinning magnetars can be used to test the SS hypothesis based on the distinct spin limits of NSs and SSs. \\ ( http://arxiv.org/abs/0910.5291 , 50kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5292 Date: Wed, 28 Oct 2009 05:04:10 GMT (115kb) Title: Probing spectral properties of radio-quiet quasars searched for optical microvariability Authors: Hum Chand (1), Paul J. Wiita (2,3), Alok C. Gupta (1)((1) ARIES, Nainital, India; (2) GSU, Atlanta, USA; (3) School of Natural Sciences, Institute for Advanced Study, Princeton, USA) Categories: astro-ph.CO Comments: 15 pages, 8 figures, 5 table, accepted for publication in MNRAS \\ We obtained SDSS spectra for a set of 37 radio-quiet quasars (RQQSOs) that had been previously examined for rapid small scale optical variations, or microvariability. Their H-beta and Mg II emission lines were carefully fit to determine line widths (FWHM) as well as equivalent widths (EW) due to the broad emission line components. The line widths were used to estimate black hole masses and Eddington ratios, ell. Both EW and FWHM are anticorrelated with ell. The EW distributions provide no evidence for the hypothesis that a weak jet component in the RQQSOs is responsible for their microvariability. \\ ( http://arxiv.org/abs/0910.5292 , 115kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5293 Date: Wed, 28 Oct 2009 05:14:27 GMT (883kb) Title: Monte Carlo Simulations of Globular Cluster Evolution. VI. The Influence of an Intermediate Mass Black Hole Authors: Stefan Umbreit, John M. Fregeau, Frederic A. Rasio Categories: astro-ph.GA Comments: 45 pages, 9 figures, submitted to ApJ \\ We present results of a series of Monte Carlo simulations investigating the imprint of a central intermediate-mass black hole (IMBH) on the structure of a globular cluster. We investigate the three-dimensional and projected density profiles, and stellar disruption rates for idealized as well as realistic cluster models, taking into account a stellar mass spectrum and stellar evolution, and allowing for a larger, more realistic, number of stars than was previously possible with direct N-body methods. We compare our results to other N-body and Fokker-Planck simulations published previously. We find, in general, very good agreement for the overall cluster structure and dynamical evolution between direct $N$-body simulations and our Monte Carlo simulations. Significant differences exist in the number of stars that are tidally disrupted by the IMBH, which is most likely an effect of the wandering motion of the IMBH, not included in the Monte Carlo scheme. These differences, however, are negligible for the final IMBH masses in realistic cluster models as the disruption rates are generally much lower than for single-mass clusters. As a test to observations we model the cluster NGC 5694, which is known to possess a central surface brightness cusp consistent with the presence of an IMBH. We find that not only the inner slope but also the outer part of the surface brightness profile agrees with corresponding observations. This provides further evidence for the possible existence of a central IMBH in NGC5694. \\ ( http://arxiv.org/abs/0910.5293 , 883kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5299 Date: Wed, 28 Oct 2009 07:35:31 GMT (905kb) Title: On the formation of hot Neptunes and super-Earths Authors: D.S. McNeil, R.P. Nelson Categories: astro-ph.EP Comments: 19 pages, 18 figures. Final version accepted to MNRAS 30 September 2009 \\ The discovery of short-period Neptune-mass objects, now including the remarkable system HD69830 (Lovis et al. 2006) with three Neptune analogues, raises difficult questions about current formation models which may require a global treatment of the protoplanetary disc. Several formation scenarios have been proposed, where most combine the canonical oligarchic picture of core accretion with type I migration (e.g. Terquem & Papaloizou 2007) and planetary atmosphere physics (e.g. Alibert et al. 2006). To date, published studies have considered only a small number of progenitors at late times. This leaves unaddressed important questions about the global viability of the models. We seek to determine whether the most natural model -- namely, taking the canonical oligarchic picture of core accretion and introducing type I migration -- can succeed in forming objects of 10 Earth masses and more in the innermost parts of the disc. This problem is investigated using both traditional semianalytic methods for modelling oligarchic growth as well as a new parallel multi-zone N-body code designed specifically for treating planetary formation problems with large dynamic range (McNeil & Nelson 2009). We find that it is extremely difficult for oligarchic tidal migration models to reproduce the observed distribution. Even under many variations of the typical parameters, we form no objects of mass greater than 8 Earth masses. By comparison, it is relatively straightforward to form icy super-Earths. We conclude that either the initial conditions of the protoplanetary discs in short-period Neptune systems were substantially different from the standard disc models we used, or there is important physics yet to be understood. \\ ( http://arxiv.org/abs/0910.5299 , 905kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5305 Date: Wed, 28 Oct 2009 08:28:49 GMT (19kb) Title: VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars Authors: Akihiro Doi, Noriyuki Kawaguchi, Yusuke Kono, Tomoaki Oyama, Kenta Fujisawa, Hiroshi Takaba, Hiroshi Sudou, Ken-ichi Wakamatsu, Aya Yamauchi, Yasuhiro Murata, Nanako Mochizuki, Kiyoaki Wajima, Toshihiro Omodaka, Takumi Nagayama, Naomasa Nakai, Kazuo Sorai, Eiji Kawai, Mamoru Sekido, Yasuhiro Koyama, the VLBI group at GSI, Shoichiro Asano, and Hisao Uose Categories: astro-ph.CO astro-ph.HE Comments: 10 pages, no figure, 3 tables, accepted for publication in PASJ \\ We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey (SDSS) Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network (JVN). We aimed at selecting BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10^5 K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars. \\ ( http://arxiv.org/abs/0910.5305 , 19kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5312 Date: Wed, 28 Oct 2009 09:15:19 GMT (68kb) Title: Higgs mass from cosmological and astrophysical measurements Authors: L. A. Popa (Institute of Space Science, Bucharest) Categories: astro-ph.CO astro-ph.HE Comments: 17 pages, 3 figures \\ For a robust interpretation of upcoming observations from Planck and LHC experiments it is imperative to understand how the inflationary dynamics of a non-minimally coupled Higgs scalar field may affect the degeneracy of the inflationary observables. We constrain the inflationary observables and the Higgs boson mass during observable inflation by fitting the the Higgs inflationary potential directly to WMAP5+BAO+SN data. We obtain a Higgs mass a value of 143.73+14.97/-6.31 GeV at 95% CL for the central value of top quark mass. We also show that the inflation driven by a non-minimally coupled scalar field leads to significant changes of the inflationary parameters when compared with the similar constraints from the standard inflation. \\ ( http://arxiv.org/abs/0910.5312 , 68kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5325 Date: Wed, 28 Oct 2009 10:11:13 GMT (139kb) Title: Long-term gamma-ray and multiwavelength observations of 3C 454.3 (a.k.a. the Crazy Diamond) Authors: S. Vercellone (INAF/IASF Palermo), for the AGILE Team Categories: astro-ph.HE Comments: Invited Talk presented at the Conference "Accretion and Ejection in AGN: A Global View" (Como, June 22-26, 2009) \\ During the period July 2007 - January 2009, the AGILE satellite, together with several other space- and ground-based observatories monitored the activity of the flat-spectrum radio quasar 3C 454.3, yielding the longest multiwavelength coverage of this gamma-ray quasar so far. The source underwent an unprecedented period of very high activity above 100 MeV, a few times reaching gamma-ray flux levels on a day time scale higher than F=400 x 10^-8 ph cm^-2 s^-1, in conjunction with an extremely variable behavior in the optical R-band, even of the order of several tenth of magnitude in few hours, as shown by the GASP-WEBT light curves. We present the results of this long term multiwavelength monitoring campaign, with particular emphasis on the study of possible lags between the different wavebands, and the results of the modeling of simultaneous spectral energy distributions at different levels of activity. \\ ( http://arxiv.org/abs/0910.5325 , 139kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5328 Date: Wed, 28 Oct 2009 10:22:33 GMT (920kb) Title: Multiwavelength behavior of blazars in the AGILE era Authors: S. Vercellone (INAF/IASF Palermo), for the AGILE Team Categories: astro-ph.HE Comments: Invited Talk presented at the "Frascati Workshop 2009: Multifrequency behaviour of High Energy Cosmic Sources" (Vulcano, May 25 - 30, 2009) \\ The AGILE gamma-ray satellite accumulated data over two years on several blazars. Moreover, for all of the sources detected by AGILE, we exploited multiwavelength observations involving both space and ground based telescopes and consortia, obtaining in several cases broad-band spectral energy distributions (SEDs) which span from the radio wavelengths up to the TeV energy band. I will review both published and yet unpublished AGILE results on gamma-ray blazars, discussing their time variability, their gamma-ray flare durations and the theoretical modeling of the SEDs. I will also highlight the GASP-WEBT and Swift fundamental contributions to the simultaneous and long-term studies of gamma-ray blazars. \\ ( http://arxiv.org/abs/0910.5328 , 920kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5336 Date: Wed, 28 Oct 2009 10:42:47 GMT (3282kb) Title: HINODE Observations of Coherent Lateral Motion of Penumbral Filaments during a X-class Flare Authors: S. Gosain, P. Venkatakrishnan and Sanjiv Kumar Tiwari Categories: astro-ph.SR Comments: 20 pages, 3 figures, Accepted for publication in Astrophysical Journal Letters \\ The X-3.4 class flare of 13 December 2006 was observed with a high cadence of 2 minutes at 0.2 arc-sec resolution by HINODE/SOT FG instrument. The flare ribbons could be seen in G-band images also. A careful analysis of these observations after proper registration of images show flare related changes in penumbral filaments of the associated sunspot, for the first time. The observations of sunspot deformation, decay of penumbral area and changes in magnetic flux during large flares have been reported earlier in the literature. In this Letter, we report lateral motion of the penumbral filaments in a sheared region of the delta-sunspot during the X-class flare. Such shifts have not been seen earlier. The lateral motion occurs in two phases, (i) motion before the flare ribbons move across the penumbral filaments and (ii) motion afterwards. The former motion is directed away from expanding flare ribbons and lasts for about four minutes. The latter motion is directed in the opposite direction and lasts for more than forty minutes. Further, we locate a patch in adjacent opposite polarity spot moving in opposite direction to the penumbral filaments. Together these patches represent conjugate foot-points on either side of the polarity inversion line (PIL), moving towards each other. This converging motion could be interpreted as shrinkage of field lines. \\ ( http://arxiv.org/abs/0910.5336 , 3282kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5344 Date: Wed, 28 Oct 2009 11:13:48 GMT (1077kb) Title: Discovery of extreme particle acceleration in the microquasar Cygnus X-3 Authors: M. Tavani, A. Bulgarelli, G. Piano, S. Sabatini, E. Striani, Y. Evangelista, A. Trois, G. Pooley, S. Trushkin, N.A. Nizhelskij, M. McCollough, K.I.I. Koljonen, G. Pucella, A. Giuliani, A.W. Chen, E. Costa, V. Vittorini, M. Trifoglio, F. Gianotti, A. Argan, G. Barbiellini, P. Caraveo, P.W. Cattaneo, V. Cocco, T. Contessi, F. D'Ammando, E. Del Monte, G. De Paris, G. Di Cocco, G. Di Persio, I. Donnarumma, M. Feroci, A. Ferrari, F. Fuschino, M. Galli, C. Labanti, I. Lapshov, F. Lazzarotto, P. Lipari, F. Longo, E. Mattaini, M. Marisaldi, M. Mastropietro, A. Mauri, S. Mereghetti, E. Morelli, A. Morselli, L. Pacciani, A. Pellizzoni, F. Perotti, P. Picozza, M. Pilia, M. Prest, M. Rapisarda, A. Rappoldi, E. Rossi, A. Rubini, E. Scalise, P. Soffitta, E. Vallazza, S. Vercellone, A. Zambra, D. Zanello, et al. (7 additional authors not shown) Categories: astro-ph.HE astro-ph.CO Comments: 29 pages (including Supplementary Information), 8 figures, 2 tables version submitted to Nature on August 7, 2009 (revised version accepted by Nature on October 8, 2009) \\ The study of relativistic particle acceleration is a major topic of high-energy astrophysics. It is well known that massive black holes in active galaxies can release a substantial fraction of their accretion power into energetic particles, producing gamma-rays and relativistic jets. Galactic microquasars (hosting a compact star of 1-10 solar masses which accretes matter from a binary companion) also produce relativistic jets. However, no direct evidence of particle acceleration above GeV energies has ever been obtained in microquasar ejections, leaving open the issue of the occurrence and timing of extreme matter energization during jet formation. Here we report the detection of transient gamma-ray emission above 100 MeV from the microquasar Cygnus X-3, an exceptional X-ray binary which sporadically produces powerful radio jets. Four gamma-ray flares (each lasting 1-2 days) were detected by the AGILE satellite simultaneously with special spectral states of Cygnus X-3 during the period mid-2007/mid-2009. Our observations show that very efficient particle acceleration and gamma-ray propagation out of the inner disk of a microquasar usually occur a few days before major relativistic jet ejections. Flaring particle energies can be thousands of times larger than previously detected maximum values (with Lorentz factors of 105 and 102 for electrons and protons, respectively). We show that the transitional nature of gamma-ray flares and particle acceleration above GeV energies in Cygnus X-3 is clearly linked to special radio/X-ray states preceding strong radio flares. Thus gamma-rays provide unique insight into the nature of physical processes in microquasars. \\ ( http://arxiv.org/abs/0910.5344 , 1077kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5355 Date: Wed, 28 Oct 2009 11:54:24 GMT (747kb) Title: High-contrast coronagraph for ground-based imaging of Jupiter-like planets Authors: Jiangpei Dou, Deqing Ren, Yongtian Zhu Categories: astro-ph.IM astro-ph.SR \\ We propose a high-contrast coronagraph for direct imaging of young Jupiter-like planets orbiting nearby bright stars. The coronagraph employs a step-transmission filter in which the intensity is apodized with a finite number of steps of identical transmission in each step. It should be installed on a large ground-based telescope equipped with state-of-the-art adaptive optics systems. In that case, contrast ratios around 10^-6 should be accessible within 0.1 arc seconds of the central star. In recent progress, a coronagraph with circular apodizing filter has been developing, which can be used for a ground-based telescope with central obstruction and spider structure. It is shown that ground-based direct imaging of Jupiter-like planets is promising with current technology. \\ ( http://arxiv.org/abs/0910.5355 , 747kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5359 Date: Wed, 28 Oct 2009 12:03:17 GMT (411kb) Title: Test of hadronic interaction models with air shower data Authors: J.R. Hoerandel Categories: astro-ph.HE Comments: Invited talk at the 13th International Conference on Elastic & Diffractive Scattering, CERN, 2009 \\ The description of high-energy hadronic interactions plays an important role in the (astrophysical) interpretation of air shower data. The parameter space important for the development of air showers (energy and kinematical range) extends well beyond todays accelerator capabilities. Therefore, accurate measurements of air showers are used to constrain modern models to describe high-energy hadronic interactions. The results obtained are complementary to information gained at accelerators and add to our understanding of high-energy hadronic interactions. \\ ( http://arxiv.org/abs/0910.5359 , 411kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5362 Date: Wed, 28 Oct 2009 13:49:21 GMT (343kb) Title: Relativistic tidal compressions of a star by a massive black hole Authors: M. Brassart, J.-P. Luminet Categories: astro-ph.CO astro-ph.HE Comments: 8 pages, 11 figures, submitted to Astron. Astrophys \\ Aims: We investigate the stellar pancake mechanism during which a solar-type star is tidally flattened within its orbital plane passing close to a 10^6 solar masses black hole. We simulate the relativistic orthogonal compression process and follow the associated shock waves formation. Methods: We consider a one-dimensional hydrodynamical stellar model moving in the relativistic gravitational field of a non-rotating black hole. The model is numerically solved using a Godunov-type shock-capturing source-splitting method in order to correctly reproduce the shock waves profiles. Results: Simulations confirm that the space-time curvature can induce several successive orthogonal compressions of the star which give rise to several strong shock waves. The shock waves finally escape from the star and repeatedly heat up the stellar surface to high energy values. Such a shock-heating could interestingly provide a direct observational signature of strongly disruptive star - black hole encounters through the emission of hard X or soft gamma-ray bursts. Timescales and energies of such a process are consistent with some observed events such as GRB 970815. \\ ( http://arxiv.org/abs/0910.5362 , 343kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5365 Date: Wed, 28 Oct 2009 15:31:22 GMT (86kb) Title: A correlation between the spectral and timing properties of AGN Authors: I. E. Papadakis, M. Sobolewska, P. Arevalo, A. Markowitz, I. M. McHardy, L. Miller, J. N. Reeves, and T.J. Turner Categories: astro-ph.CO Comments: 10 pages, 3 figures Journal-ref: 2009, A&A, 494, 905 \\ We present the results from a combined study of the average X-ray spectral and timing properties of 14 nearby AGN. For 11 of the sources in the sample, we used all the available data from the RXTE archive, which were taken until the end of 2006. There are 7795 RXTE observations in total for these AGN, obtained over a period of ~7-11 years. We extracted their 3-20 keV spectra and fitted them with a simple power-law model, modified by the presence of a Gaussian line (at 6.4 keV) and cold absorption, when necessary. We used these best-fit slopes to estimate the mean spectral slope for each object, while we used results from the literature to estimate the average spectral slope of the three objects without archival, monitorin RXTE data. Our results show that the AGN average spectral slopes are not correlated either with the black hole mass or the characteristic frequencies that were detected in the power spectra.They are positively correlated, though, with the characteristic frequency when normalised to the sources black hole mass. This is similar to the spectral-timing correlation that has been observed in Cyg X-1, but not the same.The AGN spectral-timing correlation can be explained if we assume that the accretion rate determines both the average spectral slope and the characteristic time scales in AGN. The spectrum should steepen and the characteristic frequency should increase, proportionally, with increasing accretion rate. We also provide a quantitative expression between spectral slope and accretion rate. Thermal Comptonisation models are broadly consistent with our result, but only if the ratio of the soft photons' luminosity to the power injected to the hot corona is proportionally related to the accretion rate. \\ ( http://arxiv.org/abs/0910.5365 , 86kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5372 Date: Wed, 28 Oct 2009 13:34:41 GMT (894kb) Title: Exploring the Luminosity Evolution and Stellar Mass Assembly of 2SLAQ Luminous Red Galaxies Between Redshift 0.4 and 0.8 Authors: Manda Banerji (IoA, Cambridge/UCL), Ignacio Ferreras (MSSL-UCL), Filipe B. Abdalla (UCL), Paul Hewett (IoA, Cambridge), Ofer Lahav (UCL) Categories: astro-ph.CO Comments: 17 pages, 15 figures, MNRAS \\ We present an analysis of the evolution of 8625 Luminous Red Galaxies between z = 0.4 and z = 0.8 in the 2dF and SDSS LRG and QSO (2SLAQ) survey. The LRGs are split into redshift bins and the evolution of both the luminosity and stellar mass function with redshift is considered and compared to the assumptions of a passive evolution scenario. We draw attention to several sources of systematic error that could bias the evolutionary predictions made in this paper. While the inferred evolution is found to be relatively unaffected by the exact choice of spectral evolution model used to compute K+e corrections, we conclude that photometric errors could be a source of significant bias in colour-selected samples such as this, in particular when using parametric maximum likelihood based estimators. We find that the evolution of the most massive LRGs is consistent with the assumptions of passive evolution and that the stellar mass assembly of the LRGs is largely complete by z ~ 0.8. Our findings suggest that massive galaxies with stellar masses above 10^11 solar masses must have undergone merging and star formation processes at a very early stage (z > 1). This supports the emerging picture of downsizing in both the star formation as well as the mass assembly of early type galaxies. Given that our spectroscopic sample covers an unprecedentedly large volume and probes the most massive end of the galaxy mass function, we find that these observational results present a significant challenge for many current models of galaxy formation \\ ( http://arxiv.org/abs/0910.5372 , 894kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5392 Date: Wed, 28 Oct 2009 14:54:43 GMT (1986kb) Title: Fluctuation dynamo based on magnetic reconnections Authors: Andrew W. Baggaley, Carlo F. Barenghi, Anvar Shukurov, Kandaswamy Subramanian Categories: astro-ph.SR Comments: 17 pages \\ We develop a new model of the fluctuation dynamo in which the magnetic field is confined to thin flux ropes advected by a multi-scale flow which models turbulence. Magnetic dissipation occurs only via reconnections of flux ropes. The model is particularly suitable for rarefied plasma, such as the Solar corona or galactic halos. We investigate the kinetic energy release into heat, mediated by dynamo action, both in our model and by solving the induction equation with the same flow. We find that the flux rope dynamo is more than an order of magnitude more efficient at converting mechanical energy into heat. The probability density of the magnetic energy released during reconnections has a power-law form with the slope -3, consistent with the Solar corona heating by nanoflares. We also present a nonlinear extension of the model. This shows that a plausible saturation mechanism of the fluctuation dynamo is the suppression of turbulent magnetic diffusivity, due to suppression of random stretching at the location of the flux ropes. We confirm that the probability distribution function of the magnetic line curvature has a power-law form suggested by (Schekochihin et al., 2002). We argue, however, using our results that this does not imply a persistent folded structure of magnetic field, at least in the nonlinear stage. \\ ( http://arxiv.org/abs/0910.5392 , 1986kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5400 Date: Wed, 28 Oct 2009 15:10:03 GMT (94kb) Title: Optical linear polarization in ultra cool dwarfs: A tool to probe dust in the ultra cool dwarf atmospheres Authors: R. Tata, E. L. Martin, S. Sengupta, N. Phan-Bao, M. R. Zapatero Osorio, H. Bouy Categories: astro-ph.SR Comments: 7 pages, 2 figures \\ Aims.Recent studies have detected linear polarization in L dwarfs in the optical I band. Theoretical models have been developed to explain this polarization. These models predict higher polarization at shorter wavelengths. We discuss the polarization in the R and I band of 4 ultra cool dwarfs. Methods.We report linear polarization measurements of 4 ultra cool dwarfs in the R and I bands using the Intermediate dispersion Spectrograph and Imaging System (ISIS) mounted on the 4.2m William Herschel Telescope (WHT). Results.As predicted by theoretical models, we find a higher degree of polarization in the R band when compared to polarization in the I band for 3/4 of these ultra cool dwarfs. This suggests that dust scattering asymmetry is caused by oblateness >.We also show how these measurements fit the theoretical models. A case for variability of linear polarization is found, which suggests the presence of randomly distributed dust clouds. We also discuss one case for the presence of a cold debris disk. \\ ( http://arxiv.org/abs/0910.5400 , 94kb) ------------------------------------------------------------------------------ \\ arXiv:0910.5418 Date: Wed, 28 Oct 2009 16:30:36 GMT (915kb) Title: Photometric redshifts and cluster tomography in the ESO Distant Cluster Survey Authors: R. Pello, G. Rudnick, G. De Lucia, L. Simard, D. I. Clowe, P. Jablonka, B. Milvang-Jensen, R. P. Saglia, S. D. M. White, A. Aragon-Salamanca, C. Halliday, B. Poggianti, P. Best, J. Dalcanton, M. Dantel-Fort, B. Fort, A. von der Linden, Y. Mellier, H. Rottgering, and D. Zaritsky Categories: astro-ph.CO Comments: 26 pages, 22 figures, accepted for publication in A&A High-resolution version of the paper and figures can be found at http://www.ast.obs-mip.fr/users/roser/photoz_EDISCS/ \\ This paper reports the results obtained on the photometric redshifts measurement and accuracy, and cluster tomography in the ESO Distant Cluster Survey (EDisCS) fields. Photometric redshifts were computed using two independent codes (Hyperz and G. Rudnick's code). The accuracy of photometric redshifts was assessed by comparing our estimates with the spectroscopic redshifts of ~1400 galaxies in the 0.3