2] arXiv:0802.0002 [ps, pdf, other] Title: The Third Image of the Large-Separation Lensed Quasar SDSS J1029+2623 Authors: Masamune Oguri, Eran O. Ofek, Naohisa Inada, Tomoki Morokuma, Emilio E. Falco, Christopher S. Kochanek, Issha Kayo, Tom Broadhurst, Gordon T. Richards Comments: 5 pages, 3 figures, accepted for publication in ApJ Letters Subjects: Astrophysics (astro-ph) We identify a third image in the unique quasar lens SDSS J1029+2623, the second known quasar lens produced by a massive cluster of galaxies. The spectrum of the third image shows similar emission and absorption features, but has a redder continuum than the other two images which can be explained by differential extinction or microlensing. We also identify several lensed arcs. Our observations suggest a complicated structure of the lens cluster at z~0.6. We argue that the three lensed images are produced by a naked cusp on the basis of successful mass models, the distribution of cluster member galaxies, and the shapes and locations of the lensed arcs. Lensing by a naked cusp is quite rare among galaxy-scale lenses but is predicted to be common among large-separation lensed quasars. Thus the discovery can be viewed as support for an important theoretical prediction of the standard cold dark matter model. [32] arXiv:0802.0149 [ps, pdf, other] Title: Spectroscopy of clusters in the ESO distant cluster survey (EDisCS).II. Redshifts, velocity dispersions, and substructure for clusters in the last 15 fields Authors: Bo Milvang-Jensen, Stefan Noll, Claire Halliday, Bianca M. Poggianti, Pascale Jablonka, Alfonso Aragon-Salamanca, Roberto P. Saglia, Nina Nowak, Anja von der Linden, Gabriella De Lucia, Roser Pello, John Moustakas, Sebastien Poirier, Steven P. Bamford, Douglas I. Clowe, Julianne J. Dalcanton, Gregory H. Rudnick, Luc Simard, Simon D. M. White, Dennis Zaritsky Comments: 31 pages, 23 figures, accepted for publication in A&A Subjects: Astrophysics (astro-ph) AIMS. We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. METHODS. We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. RESULTS. The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise for spectra from tilted slits. Redshifts for individual galaxies are presented and redshifts and velocity dispersions are presented for 21 galaxy clusters. For the 9 clusters with at least 20 spectroscopically confirmed members, we present the statistical significance of the presence of substructure obtained from the Dressler-Shectman test, and substructure is detected in two of the clusters. CONCLUSIONS. Together with data from our previous paper, spectroscopy and spectroscopic velocity dispersions are now available for 26 EDisCS clusters with redshifts in the range 0.40-0.96 and velocity dispersions in the range 166-1080 km/s. [1] arXiv:0802.0198 [ps, pdf, other] Title: Merger Rates of Dark-Matter Haloes Authors: Eyal Neistein, Avishai Dekel Comments: 11 pages, 9 figures Subjects: Astrophysics (astro-ph) We derive analytic merger rates for dark-matter haloes within the framework of the Extended Press-Schechter (EPS) formalism. These rates become self-consistent within EPS once we realize that the typical merger in the limit of a small time-step involves more than two progenitors, contrary to the assumption of binary mergers adopted in earlier studies. We present a general method for computing merger rates that span the range of solutions permitted by the EPS conditional mass function, and focus on a specific solution that attempts to match the merger rates in N-body simulations. The corrected EPS merger rates are more accurate than the earlier estimates of Lacey & Cole, by ~20% for major mergers and by up to a factor of ~3 for minor mergers of mass ratio 1:10^4. Based on the revised merger rates, we provide a new algorithm for constructing Monte-Carlo EPS merger trees, that could be useful in Semi-Analytic Modeling. We provide analytic expressions and plot numerical results for several quantities that are very useful in studies of galaxy formation. This includes (a) the rate of mergers of a given mass ratio per given final halo, (b) the fraction of mass added by mergers to a halo, and (c) the rate of mergers per given main progenitor. We also compute the creation and destruction rates of haloes as a self-consistency check. Our method for computing merger rates can be applied to conditional mass functions beyond EPS, such as those obtained by the ellipsoidal collapse model or extracted from N-body simulations. [7] arXiv:0802.0210 [ps, pdf, other] Title: Equal- and unequal-mass mergers of disk and elliptical galaxies with black holes: The M_BH-sigma and M_BH-M_* relations Authors: Peter H. Johansson, Thorsten Naab, Andreas Burkert (USM, Munich) Comments: 21 pages, 13 figures, submitted to ApJ License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) We present binary galaxy merger simulations with varying mass ratios and different progenitor morphologies. The simulations include mergers of gas-rich disks (Sp-Sp), of early-type galaxies and disks (E-Sp, mixed mergers), and mergers of early-type galaxies (E-E, dry mergers). We follow the dynamics of gas, stars and dark matter, and include radiative cooling, star formation and black hole (BH) accretion and the associated feedback processes as in Springel et al. We study the mass assembly of the BHs and discuss technical issues of the implemented model in detail. For Sp-Sp mergers, the peak star formation rate and BH accretion rate decrease and the growth timescales of the central black holes and newly formed stars increase with higher progenitor mass ratios. The peak BH accretion rate typically occurs shortly after the time of BH merging for low progenitor mass ratios (e.g. 3:1 and lower), whereas for higher progenitor mass ratios there is no clear correlation between the peak BH accretion rate and BH merging time. The termination of star formation by BH feedback in disk mergers is significantly less important for higher progenitor mass ratios (e.g. 3:1 and higher). In addition, the inclusion of BH feedback suppresses efficiently star formation in dry E-E mergers and mixed E-Sp mergers. All merger remnants, independent of their progenitors, follow the observed relations between the central BH mass and the stellar velocity dispersion M_BH-sigma and the bulge mass M_BH-M_*, with the dominant source of scatter arising from variations in the initial gas mass fraction. The normalizations for both relations and the simulated slope of the M_BH-sigma relation are in good agreement, whereas the simulated slope of the M_BH-M_* relation is slightly steeper compared to the observations (abridged). [10] arXiv:0802.0228 [ps, pdf, other] Title: Lyman-alpha Emitters and Lyman-break Galaxies at z=3-6 in Cosmological SPH Simulations Authors: Kentaro Nagamine (UNLV), Masami Ouchi (OCIW), Volker Springel (MPA), Lars Hernquist (Harvard) Comments: 17 pages, 9 figures, emulateapj Subjects: Astrophysics (astro-ph) We study the properties of Lyman-alpha emitters (LAEs) and Lyman-break galaxies (LBGs) at z=3-6 using cosmological SPH simulations. We investigate two simple scenarios for explaining the observed Ly-a and rest-frame UV luminosity functions (LFs) of LAEs: (i) the ``escape fraction'' scenario, in which the effective escape fraction (including the IGM attenuation) of Ly-a photons is \fLya ~0.1 (0.15) at z=3 (6), and (ii) the ``duty cycle'' scenario, in which the fraction of LAEs that are turned on at z=3 (6) is \Cduty ~0.07 (0.2) after correcting for the IGM attenuation. Our comparisons with a number of different observations suggest that the duty cycle scenario is preferred over the escape fraction scenario. We find that the mean values of stellar mass, metallicity and black hole mass hosted by LAEs are all smaller in the duty cycle scenario than in the escape fraction scenario. In our simulations, the galaxy stellar mass function evolves rapidly, as expected in hierarchical structure formation. However, its evolution is largely compensated by a beginning decline in the specific star formation rate, resulting in little evolution of the rest-frame UV LF from z=6 to 3. The rest-frame UV LF of both LAEs and LBGs at z=3 & 6 can be described well by the duty cycle scenario provided the extinction is moderate, E(B-V)~0.15, for both populations, although our simulation might be overpredicting the number of bright LBGs at z=6. We also discuss the correlation length and bias of LAEs. The Ly-a LFs at z=6 in a field-of-view of 0.2 deg^2 show a significantly larger scatter owing to cosmic variance relative to that in a 1 deg^2 field, and the scatter seen in the current observational estimates of the Ly-a LF can be accounted for by cosmic variance. 30] arXiv:0802.0370 [ps, pdf, other] Title: Integral field spectroscopy of four lensed quasars: analysis of their neighborhood and evidence for microlensing Authors: T. Anguita (1), C. Faure (1), A. Yonehara (1,2), J. Wambsganss (1), J.-P. Kneib (3), G. Covone (4), D. Alloin (5) ((1) ARI/Zentrum fuer Astronomie, University of Heidelberg, (2) JSPS Fellowships for Research Abroad, (3) Laboratoire d'Astrophysique de Marseille, (4) INAF, Naples, (5) AIM, CEA/DSM-CNRS-Universite Paris 7) Comments: 13 pages, 18 figures. Accepted for publication in A&A: January 7, 2008 Subjects: Astrophysics (astro-ph) CONTEXT: Gravitationally lensed quasars constitute an independent tool to derive H0 through time-delays; they offer as well the opportunity to study the mass distribution and interstellar medium of their lensing galaxies and, through microlensing they also allow one to study details of the emitting source. AIMS: For such studies, one needs to have an excellent knowledge of the close environment of the lensed images in order to model the lensing potential: this means observational data over a large field-of-view and spectroscopy at high spatial resolution. METHODS: We present VIMOS integral field observations around four lensed quasars: HE 0230-2130, RX J0911.4+0551, H 1413+117 and B 1359+154. Using the low, medium and high resolution modes, we study the quasar images and the quasar environments, as well as provide a detailed report of the data reduction. RESULTS: Comparison between the quasar spectra of the different images reveals differences for HE 0230-2130, RX J0911.4+0551 and H 1413+117: flux ratios between the images of the same quasar are different when measured in the emission lines and in the continuum. We have also measured the redshifts of galaxies in the neighborhood of HE 0230-2130 and RX J0911.4+0551 which possibly contribute to the total lensing potential. CONCLUSIONS: A careful analysis reveals that microlensing is the most natural explanation for the (de)magnification of the continuum emitting region of the background sources. In HE 0230-2130, image D is likely to be affected by microlensing magnification; in RX J0911.4+0551, images A1 and A3 are likely to be modified by microlensing de-magnification and in H 1413+117, at least image D is affected by microlensing. arXiv:0802.0497 [ps, pdf, other] Title: The SCUBA HAlf Degree Extragalactic Survey (SHADES) - VII. Optical/IR photometry and stellar masses of sub-millimeter galaxies Authors: Simon Dye, S. A. Eales, I. Aretxaga, S. Serjeant, J. S. Dunlop, T. S. R. Babbedge, S. C. Chapman, M. Cirasuolo, D. L. Clements, K. E. K. Coppin, L. Dunne, E. Egami, D. Farrah, R. J. Ivison, E. van Kampen, A. Pope, R. Priddey, G. H. Rieke, A. M. Schael, D. Scott, C. Simpson, T. Takagi, T. Takata, M. Vaccari Comments: 27 pages, 23 figures. Refereed resubmission to MNRAS. 5 figures containing postage stamp images have been placed in separate files due to upload limit Subjects: Astrophysics (astro-ph) We present estimates of the photometric redshifts, stellar masses and star formation histories of sources in the SCUBA HAlf Degree Extragalactic Survey (SHADES). This paper describes the 60 SCUBA sources detected in the Lockman Hole covering an area of ~320 square arcmin. Using photometry spanning the B band to 8um, we find that the average SCUBA source forms a significant fraction of its stars in an early period of star formation and that most of the remainder forms in a shorter more intense burst around the redshift it is observed. This trend does not vary significantly with source redshift but the exact ratio of early to late mass is quite sensitive to the way extinction is treated in the modelling. However, the sources show a clear increase in stellar mass with redshift, consistent with downsizing. In terms of SED types, only two out of the 51 sources we have obtained photometric redshifts for are best fit by a quasar-like spectral energy distribution, with approximately 80 per cent of the sources being best fit with late-type spectra (Sc, Im and starburst). By including photometry at 850um, we conclude that the average SCUBA source is forming stars at a rate somewhere between 6 and 30 times the rate implied from the rest-frame optical in a dust obscured burst and that this burst creates 15-65 per cent of the total stellar mass. Using a simplistic calculation, we estimate from the average star formation history that between one in five and one in 15 bright (L_* +2 mag < L_optical < L_* -1 mag) galaxies in the field over the interval 0 < z < 3 will at some point in their lifetime experience a similar energetic dusty burst of star formation. Finally, we compute the evolution of the star formation rate density and find it peaks around z=2. [12] arXiv:0802.0508 [ps, pdf, other] Title: Dissipation and Extra Light in Galactic Nuclei: I. Gas-Rich Merger Remnants Authors: Philip F. Hopkins (1), Lars Hernquist (1), Thomas J. Cox (1), Suvendra N. Dutta (1), Barry Rothberg (2) ((1) CfA, (2) STScI) Comments: 35 pages, 36 figures, submitted to ApJ License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) We study the origin and properties of 'extra' or 'excess' central light in the surface brightness profiles of gas-rich merger remnants. Combining a large set of hydrodynamical simulations with data on observed mergers (spanning a broad range of profiles at various masses and degrees of relaxation), we show how to robustly separate the physically meaningful extra light -- stellar populations formed in a compact central starburst during a gas-rich merger -- from the outer profile established by violent relaxation acting on stars already present in the progenitors prior to the final merger. This separation is sensitive to the profile treatment, and we demonstrate that certain fitting procedures can yield physically misleading results. We show that our method reliably recovers the younger starburst population, and examine how the properties of this component scale with mass, gas content, and other aspects of the progenitors. We consider the time evolution of profiles in different bands, and estimate biases introduced by observational studies at different times and wavelengths. We show that extra light is ubiquitous in observed and simulated gas-rich merger remnants, with sufficient mass (~3-30% of the stellar mass) to explain the discrepancy in the maximum phase-space densities of ellipticals and their progenitor spirals. The nature of this central component provides powerful new constraints on the formation histories of observed systems. [4] arXiv:0802.0877 [ps, pdf, other] Title: The shapes of galaxies in the Sloan Digital Sky Survey Authors: Nelson D. Padilla (1), Michael A. Strauss (2) ((1) Pontificia Universidad Catolica de Chile, (2) Princeton University) Comments: 17 page, 14 figures, submitted to MNRAS License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) We determine the underlying shapes of spiral and elliptical galaxies in the Sloan Digital Sky Survey Data Release 6 from the observed distribution of projected galaxy shapes, taking into account the effects of dust extinction and reddening. We assume that theunderlying shapes of spirals and ellipticals are well approximated by triaxial ellipsoids. The elliptical galaxy data are consistent with oblate spheroids, with a correlation between roundness and ellipticity: the mean values of minor to middle axis ratios are 0.41+-0.03 for faint ellipticals and 0.76+-0.04 for bright ellipticals. Ellipticals show almost no dependence of axial ratio on galaxy colour, implying a negligible dust optical depth. There is a strong variation of spiral galaxy shapes with colour indicating the presence of dust. The intrinsic shapes of spiral galaxies in the SDSS-DR6 are consistent with flat disks with a mean and dispersion of thickness to diameter ratio of (21+-5)%, and a face-on ellipticity, e, of ln(e)=-1.85+-1.04. Not including the effects of dust in the model leads to disks that are systematically rounder by >10%. More luminous spiral galaxies tend to have thicker and rounder disks than lower-luminosity spirals. Both elliptical and spiral galaxies tend to be rounder for larger galaxies. The marginalised value of the edge-on r-band dust extinction E_0 in spiral galaxies is E_0 ~ 0.5 magnitudes for galaxies of median colours, increasing to E_0=1 magnitudes for g-r>0.9 and E_0>2 for the luminous and most compact galaxies, with half-light radii <2kpc/h. [5] arXiv:0802.0879 [ps, pdf, other] Title: Kinemetry of SINS High-Redshift Star-Forming Galaxies: Distinguishing Rotating Disks from Major Mergers Authors: K. L. Shapiro, R. Genzel, N. M. Forster Schreiber, L. J. Tacconi, N. Bouche, G. Cresci, R. Davies, F. Eisenhauer, P. H. Johansson, D. Krajnovic, D. Lutz, T. Naab, N. Arimoto, S. Arribas, A. Cimatti, L. Colina, E. Daddi, O. Daigle, D. Erb, O. Hernandez, X. Kong, M. Mignoli, M. Onodera, A. Renzini, A. Shapley, C. Steidel Comments: Accepted for publication in the Astrophysical Journal. 24 pages, 14 figures Subjects: Astrophysics (astro-ph) We present a simple set of kinematic criteria that can distinguish between galaxies dominated by ordered rotational motion and those involved in major merger events. Our criteria are based on the dynamics of the warm ionized gas (as traced by H-alpha) within galaxies, making this analysis accessible to high-redshift systems, whose kinematics are primarily traceable through emission features. Using the method of kinemetry (developed by Krajnovic and co-workers), we quantify asymmetries in both the velocity and velocity dispersion maps of the warm gas, and the resulting criteria enable us to empirically differentiate between non-merging and merging systems at high redshift. We apply these criteria to 11 of our best-studied rest-frame UV/optical-selected z~2 galaxies for which we have near infrared integral field spectroscopic data from SINFONI on the VLT. Of these 11 systems, we find that >50% have kinematics consistent with a single rotating disk interpretation, while the remaining systems are more likely undergoing major mergers. This result, combined with the short formation timescales of these systems, provides evidence that rapid, smooth accretion of gas plays a significant role in galaxy formation at high redshift. 38] arXiv:0802.1050 [ps, pdf, other] Title: HST NICMOS imaging of z~2, 24 micron selected Ultraluminous Infrared Galaxies Authors: Kalliopi M. Dasyra, Lin Yan, George Helou, Jason Surace, Anna Sajina, James Colbert Comments: Accepted for publication in ApJ License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Subjects: Astrophysics (astro-ph) We present Hubble Space Telescope NICMOS H-band imaging of 33 Ultraluminous Infrared Galaxies (ULIRGs) at z~2 that were selected from the 24 micron catalog of the Spitzer Extragalactic First Look Survey. The images reveal that at least 17 of the 33 objects are associated with interactions. Up to one fifth of the sources in our sample could be minor mergers whereas only 2 systems are merging binaries with luminosity ratio <=3:1, which is characteristic of local ULIRGs. The rest-frame optical luminosities of the sources are of the order 10^10-10^11 L_sun and their effective radii range from 1.4 to 4.9 kpc. The most compact sources are either those with a strong active nucleus or those with a heavy obscuration in the mid-infrared regime, as determined from Spitzer Infra-Red Spectrograph data. The luminosity of the 7.7 micron feature produced by Polycyclic Aromatic Hydrocarbon molecules varies significantly amongst compact systems whereas it is typically large for extended systems. A bulge-to-disk decomposition performed for the 6 brightest (m_H<20) sources in our sample indicates that they are best fit by disk-like profiles with small or negligible bulges, unlike the bulge-dominated remnants of local ULIRGs. Our results provide evidence that the interactions associated with ultraluminous infrared activity at z~2 can differ from those at z~0.