arXiv:0807.3966 [ps, pdf, other] Title: Near- and mid-infrared photometry of high-redshift 3CR sources Authors: M. Haas, S.V.P. Willner, F. Heymann, M.L.N. Ashby, G.G. Fazio, B.J. Wilkes, R. Chini, R. Siebenmorgen Comments: 11 pages, 5 figures, accepted by ApJ Subjects: Astrophysics (astro-ph) Using the Spitzer Space Telescope, we have obtained 3.6--24 micron photometry of 38 radio galaxies and 24 quasars from the 3CR catalog at redshift 110^11 M_sun) galaxies at 1.72, confirming the extreme compactness of these galaxies. We split our sample into disk-like (n<2) and spheroid-like (n>2) galaxies based on their Sersic indices, and find that at a given stellar mass disk-like galaxies at z~2.3 are a factor of 2.6+/-0.3 smaller than present day equal mass systems, and spheroid-like galaxies at the same redshifts are 4.3+/-0.7 smaller than comparatively massive elliptical galaxies today. At z>2 our results are compatible with both a leveling off, or a mild evolution in size. Furthermore, the high density (~2x10^10 M_sun kpc^-3) of massive galaxies at these redshifts, which are similar to present day globular clusters, possibly makes any further evolution in sizes beyond z=3 unlikely. arXiv:0807.4508 [ps, pdf, other] Title: Constraints on large scale voids from WMAP-5 and SDSS Authors: Paul Hunt, Subir Sarkar Comments: 15 pages (RevTex), 28 figures Subjects: Astrophysics (astro-ph) Measurements of the SNe Ia Hubble diagram which suggest that the universe is accelerating due to the effect of dark energy may be biased because we are located in a 200-300 Mpc underdense "void" which is expanding 20-30% faster than the average rate. With the smaller global Hubble parameter, the WMAP-5 data on cosmic microwave background anisotropies can be fitted without requiring dark energy if there is some excess power in the spectrum of primordial perturbations on 100 Mpc scales. The SDSS data on galaxy clustering can also be fitted if there is a 10% component of hot dark matter in the form of 0.5 eV mass neutrinos. We find however that if the primordial fluctuations are gaussian, the expected variance of the Hubble parameter and the matter density are too small to allow such a large void. Nevertheless similar voids are seen in the SDSS LRG survey, in conflict with the same expectation, so the local void hypothesis cannot be dismissed on these grounds and must be tested observationally. The origin of such voids remains an open question. arXiv:0807.4532 [ps, pdf, other] Title: Satellite Kinematics II: The Halo Mass-Luminosity Relation of Central Galaxies in SDSS Authors: Surhud More, Frank C. van den Bosch, Marcello Cacciato, Houjun Mo, Xiahou Yang, Ran Li Comments: 17 pages, 12 figures, MNRAS submitted Subjects: Astrophysics (astro-ph) The kinematics of satellite galaxies reflect the masses of the extended dark matter haloes in which they orbit, and thus shed light on the mass-luminosity relation (MLR) of their corresponding central galaxies. In this paper we select a large sample of centrals and satellites from the Sloan Digital Sky Survey (SDSS) and measure the kinematics (velocity dispersions) of the satellite galaxies as a function of the $r$-band luminosity of the central galaxies. Using the analytical framework presented in Paper I, we use these data to infer {\it both} the mean and the scatter of the MLR of central galaxies, carefully taking account of selection effects and biases introduced by the stacking procedure. As expected, brighter centrals on average reside in more massive haloes. In addition, we find that the scatter in halo masses for centrals of a given luminosity, $\sigma_{\log M}$, also increases with increasing luminosity. As we demonstrate, this is consistent with $\sigma_{\log L}$, which reflects the scatter in the conditional probability function $P(L_c|M)$, being independent of halo mass. Our analysis of the satellite kinematics yields $\sigma_{\log L}=0.16\pm0.04$, in excellent agreement with constraints from clustering and group catalogues, and with predictions from a semi-analytical model of galaxy formation. We thus conclude that the amount of stochasticity in galaxy formation, which is characterized by $\sigma_{\log L}$, is well constrained, is independent of halo mass, and is in good agreement with current models of galaxy formation. arXiv:0807.4549 [ps, pdf, other] Title: The Structure of Active Merger Remnant NGC 6240 from IRAC Observations Authors: Stephanie J. Bush, Zhong Wang, Margarita Karovska, Giovanni G. Fazio (Harvard-Smithsonian Center for Astrophysics) Comments: Accepted for publication in ApJ Subjects: Astrophysics (astro-ph) NGC 6240 is a rare object in the local universe: an active merger remnant viewed at the point of merging where two active galactic nuclei are visible. We present IRAC data of this object, providing high sensitivity maps of the stellar and PAH distribution in this complicated system. We use photometry to analyze the variation in these distributions with radius and provide an SED in the four IRAC bands: 3.6 microns, 4.5 microns, 5.8 microns and 8.0 microns. We fit the radial profiles of the 3.6 micron band to r^.25 and exponential profiles to evaluate the structure of the remnant. Finally, we compare the IRAC images with multi-wavelength data and examine how outflows in the X-ray, Halpha and CO correlate with 8 micron emission. The results support the general picture of NGC 6240 as a system experiencing a major merger and transitioning from a disk galaxy to a spheroid. The sensitivity of IRAC to low surface brightness mid-infrared features provides detailed information on the extended distributions of stars and dust in this rare system. [19] arXiv:0807.4615 [ps, pdf, other] Title: Discovery of Hot Gas in Outflow in NGC3379 Authors: G. Trinchieri, S. Pellegrini, G. Fabbiano, R. Fu, N. J. Brassington, A. Zezas, D.-W. Kim, J. Gallagher, L. Angelini, R. L. Davies, V. Kalogera, A. R. King, S. Zepf Comments: Accepted for publication in The Astrophysical Journal Subjects: Astrophysics (astro-ph) We report the discovery of a faint (L_x ~ 4 10^37 erg/s, 0.5-2 keV), out-flowing gaseous hot interstellar medium (ISM) in NGC 3379. This represents the lowest X-ray luminosity ever measured from a hot phase of the ISM in a nearby early type galaxy. The discovery of the hot ISM in a very deep Chandra observation was possible thanks to its unique spectral and spatial signatures, which distinguish it from the integrated stellar X-ray emission, responsible for most of the unresolved emission in the Chandra data. This hot component is found in a region of about 800 pc in radius at the center of the galaxy and has a total mass M~ 3 10^5 solar masses. Independent theoretical prediction of the characteristics of an ISM in this galaxy, based on the intrinsic properti es of NGC 3379, reproduce well the observed luminosity, temperature, and radial distribution and mass of the hot gas, and indicate that the gas is in an outflowing phase, predicted by models but not observed in any system so far. arXiv:0807.4636 [ps, pdf, other] Title: The VVDS-SWIRE-GALEX-CFHTLS surveys: Physical properties of galaxies at z below 1.2 from photometric data Authors: C. J. Walcher, F. Lamareille, D. Vergani, S. Arnouts, V. Buat, S. Charlot, L. Tresse, O. Le Fevre, M. Bolzonella, J. Brinchmann, L. Pozzetti, G. Zamorani, D. Bottini, B. Garilli, V. Le Brun, D. Maccagni, B. Milliard, R. Scaramella, M. Scodeggio, G. Vettolani, A. Zanichelli, C. Adami, S. Bardelli, A. Cappi, P. Ciliegi, T. Contini, P. Franzetti, S. Foucaud, I. Gavignaud, L. Guzzo, O. Ilbert, A. Iovino, H.J. McCracken, B. Marano, C. Marinoni, A. Mazure, B. Meneux, R. Merighi, S. Paltani, R. Pello, A. Pollo, M. Radovich, E. Zucca, C. Lonsdale, D.C. Martin Comments: Submitted to A&A Subjects: Astrophysics (astro-ph) We intend to show that it is possible to derive the physical parameters of galaxies from their broad-band spectral energy distribution out to a redshift of 1.2. This method has the potential to yield the physical parameters of all galaxies in a single field in a homogeneous way. We use an extensive dataset, assembled in the context of the VVDS survey, which reaches from the UV to the IR and covers a sample of 84073 galaxies over an area of 0.89 deg$^2$. We also use a library of 100000 model galaxies with a large variety of star formation histories (in particular including late bursts of star formation). We find that we can determine the physical parameters stellar mass, age and star formation rate with good confidence. We validate the star formation rate determinations in particular by comparing it to a sample of spectroscopically observed galaxies with an emission line measurement. We use our sample to build the number density function of galaxies as a function of stellar mass, specific star formation rate and redshift. We then study whether the stellar mass function at a later time can be predicted from the stellar mass function and star formation rate distribution at an earlier time. We find that the predicted growth in stellar mass from star formation agrees with the observed one. However, the predicted stellar mass density for massive galaxies is lower than observed, while the mass density of intermediate mass galaxies is overpredicted. When comparing with a direct measurement of the major merger rate from the VVDS survey we find that major mergers are sufficient to explain about a third of the mass build-up at the massive end, while the rest is likely contributed through minor mergers. arXiv:0807.4932 [ps, pdf, other] Title: Galaxy Clustering & Galaxy-Galaxy Lensing: A Promising Union to Constrain Cosmological Parameters Authors: Marcello Cacciato, Frank C. van den Bosch, Surhud More, Ran Li, H.J. Mo, Xiaohu Yang Comments: 20 pages, 11 figures, submitted to MNRAS Subjects: Astrophysics (astro-ph) Galaxy clustering and galaxy-galaxy lensing probe the connection between galaxies and their dark matter haloes in complementary ways. On one hand, the halo occupation statistics inferred from the observed clustering properties of galaxies are degenerate with the adopted cosmology. Consequently, different cosmologies imply different mass-to-light ratios for dark matter haloes. On the other hand, galaxy-galaxy lensing yields direct constraints on the actual mass-to-light ratios and it can be used to break this degeneracy, and thus to constrain cosmological parameters. In this paper we establish the link between galaxy luminosity and dark matter halo mass using the conditional luminosity function (CLF). We constrain the CLF parameters using the galaxy luminosity function and the luminosity dependence of the correlation lengths of galaxies. The resulting CLF models are used to predict the galaxy-galaxy lensing signal. For a cosmology with $(\Omega_{\rm m},\sigma_8)=(0.238,0.734)$, the model accurately fits the galaxy-galaxy lensing data obtained from the SDSS. For a comparison cosmology with $(\Omega_{\rm m},\sigma_8)=(0.3,0.9)$, however, we can accurately fit the luminosity function and clustering properties of the galaxy population, but the model predicts mass-to-light ratios that are too high, resulting in a strong overprediction of the galaxy-galaxy lensing signal. We conclude that the combination of galaxy clustering and galaxy-galaxy lensing is a powerful probe of the galaxy-dark matter connection, with the potential to yield tight constraints on cosmological parameters. Since this method mainly probes the mass distribution on non-linear scales, it is complementary to constraints obtained from the galaxy power-spectrum, which mainly probes the large-scale (linear) matter distribution. arXiv:0807.4934 [ps, pdf, other] Title: Modeling Galaxy-Galaxy Weak Lensing with SDSS Groups Authors: Ran Li, H.J. Mo, Zuihui Fan, Marcello Cacciato, Frank C. van den Bosch, Xiaohu Yang, Surhud More Comments: 16 pages, 8 figures, submitted to MNRAS Subjects: Astrophysics (astro-ph) We use galaxy groups selected from the Sloan Digital Sky Survey (SDSS) together with mass models for individual groups to study the galaxy-galaxy lensing signals expected from galaxies of different luminosities and morphological types. We compare our model predictions with the observational results obtained from the SDSS by Mandelbaum et al. (2006) for the same samples of galaxies. The observational results are well reproduced in a $\Lambda$CDM model based on the WMAP 3-year data, but a $\Lambda$CDM model with higher $\sigma_8$, such as the one based on the WMAP 1-year data,significantly over-predicts the galaxy-galaxy lensing signal. We model, separately, the contributions to the galaxy-galaxy lensing signals from different galaxies: central versus satellite, early-type versus late-type, and galaxies in halos of different masses. We also examine how the predicted galaxy-galaxy lensing signal depends on the shape, density profile, and the location of the central galaxy with respect to its host halo.