Day 336

Tuesday.


1211.3741
The clustering of galaxies in the SDSS-III baryon oscillation spectroscopic survey: weighing the neutrino mass using the galaxy power spectrum of the CMASS sample
Zhao, Saito, Percival, Ross, ...

Measure neutrino mass using 3d galaxy power spectra of SDSS BOSS DR9 CMASS galaxy sample.  Combine with CMB, SN and other BAO data: Sum m_nu < 0.340 eV with flat LCDM, or <0.821 eV for a more general cosmological background.  N_eff = 4.308 or 4.032, respectively.  Effects of: galaxy power spectrum bias model, effect of z-space distortion, the cutoff scale of power spectrum, and the choice of additional data.  Impact of neutrinos with unknown masses on other cosmo parameter measurements investigated.  ... Other cosmo params constrained.

1211.3743
Global 21cm signal experiments: a designer's guide
Liu, Pritchard, Tegmark, Loeb

21cm: potentially a direct probe of EoR and Dark Ages.  Signal = purely spectral signature; have little angular sensitivity; difficult to distinguish from FG (galactic synchrotron radiation, much brighter).  Optimal FG removal (mathematical framework); complement spectra with angular information.  (1) with spectral-only methods, it is impossible to mitigate errors that arise from uncertainties in FG modeling, (2) FG contamination can be significantly reduced for experiments with fine angular resolution, (3) most of the statistical significance in a positive detection during the Dark Ages comes from a characteristic high-z trough in the 21cm brightness temperature; and (4) measurement errors decrease more rapidly with integration time for instruments with fine angular resolution.  An instrument with 5 degree beam can achieve highly significant detection (>5 sigma) of extended reionization scenarios after integrating for 500 hrs.  No angular resolution means no detection of gradual reionization.  Abrupt ionization histories can be detected at the level of 10-100's of sigma.  

1211.3752
Massive black hole seeds born via direct gas collapse in galaxy mergers: their properties, statistics and environment
Bonoli, Mayer, Callegari

Study the statistics and cosmic evolution of SMBH seeds formed during major mergers of gas-rich late-type galaxies with hydro-sims.  Envision a scenario in which a supermassive star can form at the center of galaxies that just experienced a major merger owing to a multi-scale powerful gas inflow, provided that such galaxies live in haloes with masses above 1e11 Msun, are gas-rich and disc-dominated, and do not already host a massive black hole.  Assume: ultimate collapse of the SM star leads to the rapid formation of BH of 1e5 Msun following a quasi-star stage.  Using a model for galaxy formation applied to the outputs of the Millennium Simulation, we show that the conditions required for this massive BH formation route to take place in the LCDM model are actually common at high z, and can be realized even at low redshift.  Most major mergers above z~4 in haloes with >1e11 Msun can lead to fromation of a massive seed and, at z~2, the fraction of favrouable mergers decreases to 1/2.  Find that even in the local universe a fraction (~20%) of major mergers in massive haloes still satisfy the conditions of our massive black hole formation route.  These late events take place in galaxies with a markedly low clustering amplitude, that have lived in isolation for most of their life, and that are experiencing a major merger for the first time.  We predict that massive black hole seeds from galaxy mergers can dominate the massive end of the mass function at z>4 and z~2 relative to lighter seeds formed at higher z (e.g. collapse of Pop III stars).  A fraction of these massive seeds could lie, soon after formation, above the MBH-MBulge relation.

1211.3771
The size and mass evolution of the massive galaxies over cosmic time
Trujillo

Passively evolving objects: which mechanism has made galaxies grow large in size without altering their stellar population properties dramatically?  Most likely minor mergers...  but: (1) insufficient number of satellites, and (2) the presence of a population of nearby massive compact galaxies with mixture of stellar properties is another piece of the puzzle that still does not nicely fit within a comprehensive scheme.

1211.3774
Modeling the distribution of Mg II absorbers around galaxies using background galaxies & quasars
Bordoloi, Lilly, Kacprzak, Churchill

Joint constraints on the distribution of MgIi absorption around galaxies: combine MgII absorption in stacked BG galaxy spectra and the distribution of host galaxies of strong MgII systems from the spectra of background quasars.  Present a suite of models that predict the dependence of MgII absorption on a galaxy's apparent inclination, impact parameter and azimuthal angle.  The variations in the absorption strength with azimuthal angles provide much stronger constraints on the intrinsic geometry of the MgII absorption than the dependence on the galaxy's inclination.  Strong absorbers are asymmatrically distributed in azimuth around their host galaxies: located within 50 deg of the host galaxy's projected minor axis.  Simple bipolar component plus a spherical or disk component, or a single highly softened bipolar distribution, can well represent the azimuthal dependencies observed in both the datasets.  Simultaneously fitting both datasets to the composite model, bipolar cone is confined to 50 deg of the minor axis and contains 2/3 of the total MgII absorption.  The single softened cone model has an exponential fall off with azimuth with an exponential scale-length in opening angle of 45 deg.  Conclude that the distribution of MgII gas at low impact parameters is not the same as that found at high impact parameters.  MgII absorption within 40 kpc primarily arises from cool MgII gas entrained in winds.  Beyond 40 kpc, there is evidence for a more symmetric distribution, significantly different from that closer into the galaxies; a significant component appears aligned more with the disk and is possibly inflowing, perhaps as part of a galactic fountain or the inflow of material from further out in the system.

1211.3973
What determines the sizes of red early-type galaxies?
Lee, Kim, Ree, ...

Investigate the origin of size dispersions, after their M, L, z and morphologies are set.  Find: sizes of faint galaxies are affected more significantly by L, while for bright galaxies, by dynamical mass.  At fixed M and L, the sizes of low-mass gals are less sensitive to their colors, color gradients and axis ratios.  On the other hand, the sizes of intermediate-mass and high-mass galaxies significantly depends on color, gradients, and axis ratios: larger red E galaxies have bluer colors [?!], more negative color gradients (bluer outskirts) and smaller axis ratios.  Results indicate that the sizes of intermediate- and high-mass red early-type galaxies are significantly affected by their recent minor mergers or rotations, whereas the sizes of low-mass red early-type galaxies are affected by some other mechanisms.  Major dry mergers also seem to have influenced on the size growth of high-mass red early-type galaxies.

1211.3976
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic survey: the low redshift sample
Parejko, Sunayama, Padmanabhan, ... et al

Small scale clustering (0.5<r< 40 Mpc/h) of 78k massive (>1e11.3Msun) galaxies at 0.2<z<0.4 from BOSS; describe the sample selection, properties of galaxies, caveats for working with the data.  Calculate the real-and z-space 2-pt correlation functions of these galaxies, fit these measurements using HOD modeling within DM cosmo sims, and estimate the errors using mocks.