Day 606

Thursday.

1403.2720
Measuring the power spectrum of dark matter substructure using strong gravitational lensing
Hezaveh, Dalal, Holder, Kisner, Kuhlen

It has become possible to detect individual DM sub haloes near SLs.  Typically, only the most massive subhaloes in the SL region may be detected this way.  In this work, show that strong lenses may also be used to constrain the much more numerous population of lower mass subhaloes that are too small to be detected individually.  In particular, show that the PS of projected density fluctuations in galaxy haloes can be measured using SL.  Develop the mathematical framework of PS estimation, and test method on mock observations.  Use results to determine the types of observations required to measure the substructure PS with high significance.  Predict that deep observations with current facilities (in particular ALMA) can measure this PS, placing strong constraints on the abundance of DM sub haloes and the underlying particle nature of DM.

1403.2725
AzTEC/ASTE 1.1 mm survey of SSA22: counterpart identification and photometric redshift survey of sub millimeter galaxies
Umehata, et al

Present the results from 1.1 mm imaging survey of SSA22 field, known for having an overdensity of z=3.1 LAEs.  950 arcmin^2 down to 0.7-1.3 mJy/beam, find 125 sub millimeter galaxies (SMGs) with S/N>3.5.  Counterpart identification using radio and near/mid-IR data was performed and one or more counterpart candidates were found for 59 SMGs.  Photo-z's based on optical to NIR images were evaluated for 45 SMGs of these SMGs with Spitzer/IRAC data, and the median value is found to be z=2.4.  By combining these estimation with estimates from the literature, determine that 10 SMGs might lie within the LSS at z=3.1.  The 2pt angular cross-correlation function between LAEs and SMGs indicates that the positions of the SMGs are correlated with the z=3.1 protocluster.  These results suggest that the SMGs were formed and evolved selectively in the high density environment of the high-z universe.  This picture is consistent with the predictions of the standard model of hierarchical structure formation.

1403.2728
Mergers drive spin swings along the cosmic web
Welker et al

The close relationship between mergers and the reorientation of the spin for galaxies and their host dark haloes is investigated using cosmo hydrosims (Horizon-AGN).  Through a statistical analysis of merger trees, show that spin swings are mainly driven by mergers along the filamentary structure of the cosmic web, and that these events account for the preferred perpendicular orientation of massive galaxies with respect to their nearest filament.  By contrast, low-mass galaxies (Ms<1e10Msun at z~1.5) undergoing very few mergers, if at all, tend to possess a spin well assigned with their filament.  [makes sense.]  Haloes follow the same trend as galaxies but display a greater sensitivity to smooth anisotropic accretion.  The relative effect of mergers on spin magnitude is qualitatively different for minor and major mergers: mergers (and diffuse accretion) generally increase the magnitude of the angular momentum, but the most massive major mergers also give rise to a population of objects with less spin left.  Without mergers secular accretion builds up the spin of galaxies but not that of haloes.  It also (re)aligns galaxies with their filament.

1403.2783
The evolution of galaxy structure over cosmic time
Conselice

[Review article] …of the evolution of galaxy structure from z~6 to 0.  Pedagogical.  Sersic fitting to measure galaxy sizes and surface brightness profile shapes; non-parametric structural methods including concentration (C), asymmetry (A), clumpiness (S) (CAS) method, as well as newer structural indices.  How these structural indices measure fundamental properties of galaxies such as their scale, SFR, and ongoing merger activity.  Extensive observational results are shown demonstrating how broad galaxy morphologies and structures change with time up to z~3, from small, compact and peculiar systems in the distant universe to the formation of the Hubble sequence found today.  Structural methods accurately measure the merger history out to z~3.  The properties and evolution of bulges, disks, bars and at z>1 large SF clumps are also described, along with how morphologically galaxy quenching occurs.  Furthermore, the role of environment in producing structure in galaxies over cosmic time is treated.  Alongside the evolution of general structure, also delineate how galaxy sizes changes with time, with measured sizes up to a factor of 2-5 smaller at high z at a given stellar mass.  This review concludes with a discussion of how galaxy structure reveals the formation mechanism behind galaxies, providing a new and unique way to test theories of galaxy formation.

1403.2927
The extended ROSAT-ESO flux limited X-ray galax cluster survey (REFLEX II) IV.  X-ray luminosity function and first constraints on cosmological parameters
Böhringer, Chon, Collins

The X-ray LF is a statistic of the census of galaxy clusters and an important means to probe the cosmological model of the Universe.  Construct the X-ray LF for several redshift slices from z=0 to 0.4 and discuss its implications.  Find no significant signature of z evolution of the LF in the redshift interval.  Provide the results of fits of a parameterized Schechter function and extensions of it which provide a reasonable characterization of the data.  Using a model for structure formation and galaxy cluster evolution, compare the observed X-ray LF with predictions for different cosmological models.  THe most interesting constraints for the cosmo parameters Omega_m and sigma_8 are 0.27pm0.03 and 0.80pm0.03, respectively, based on the statistical uncertainty alone.  Marginalizing over the most important uncertainties, the normalization and slope of the L_X-M scaling relation, find 0.28pm0.04 and 0.77pm0.07 (1sigma CL) respectively.  Compare results using PLANCK clusters as cosmo probes, but have some tension from CMB anisotropies.  Also make a comparison with other cluster surveys.  Find good agreement with previous results and show that the REFLEX II survey provides a significant reduction in the uncertainties compared to earlier measurements.

1403.2994
Herschel-ATLAS: properties of dusty massive galaxies at low and high redshifts
Rowlands et al

Present a comparison of physical properties of a rest-fram 250um selected sample of massive, dusty galaxies from 0<z<5.3.  Sample of 29 high-z SMGs from literature, 843 dusty galaxies at z<0.5 from Herschel-ATLAS, selected to have similar stellar mass to the SMGs.  The z>1 SMGs have an average SFR of 390 Msun/yr which is 120 times that of the low-z sample matched in stellar mass to the SMGs (SFR=3.3 Msun/yr).  The SMGs harbor a substantial mass of dust (1.2e9 Msun), compared to 1.6e8 Msun for low-z dusty galaxies.  At low z the dust luminosity is dominated by the diffuse ISM, whereas a large fraction of the dust luminosity in SMGs originates from SF regions.  At the same dust mass SMGs are offset towards a higher SFR compared to the low-z H-ATLAS galaxies.  This is not only due to the higher gas fraction in SMGs but also because they are undergoing a more efficient mode of SF, which is consistent with their bursty SFHs.  The offset in SFR between SMGs and low-z galaxies is similar to that found in CO studies, suggesting that dust mass is as good a tracer of molecular gas as CO.

1403.2995
The dust budget crisis in high-redshift submillimetre galaxies
Rowlands et al

Apply a chemical evolution model to investigate the sources and evolution of dust in a sample of 26 high-z (z>1) SMGs from the literature, with complete photometer from UV to the sub millimeter.  Show that dust produced only by low-intermediate mass stars falls a factor 240 short of the observed dust masses of SMGs, the well-known 'dust-budget crisis'.  Adding an extra source of dust from SNe can account for the dust mass in 19% of the SMG sample.  Even accounting for dust produced by SNe the remaining deficit in the dust mass budget provides support for higher SN yields, substantial grain growth in the ISM or a top-heavy IMF.  Including efficient destruction of dust by SN shocks increases the tension between model and observed SMG dust masses.  The models which best reproduce the physical properties of SMGs have a rapid build-up of dust from both stellar and interstellar sources and minimal dust destruction.  Alternatively, invoking a top-heavy IMF or significant changes in the dust grain properties can solve the dust budget crisis only if dust is produced by both low mass stars and SNe and is not efficiently destroyed by SN shocks.

1403.3063
Major cluster mergers and the location of the brightest cluster galaxy
Martel, Robichaud, Barai

Using N-body cosmo sim with subgrid treatment of galaxy formation, study the formation and evolution of the galaxy and cluster population in a comoving volume (100 Mpc)^3 in a LCDM universe.  At z=0, computational volume contains 1788 clusters with mass M_cl > 1.1e12 Msun, including 18 massive clusters with M_cl>1e14 Msun.  It also contains 1M galaxies with mass M_gal>2e9 Msun and luminosity L>9.5e5 Lsun.  For each cluster, identify the BCG, then compute the fraction f_BNC of clusters in which the BCG is not the closest galaxy to the center of the cluster in projection, and the ratio Dv/s, where Dv is the difference in radial velocity between the BCG and the whole cluster, and s is the radial velocity dispersion of the cluster.  Fraction f_BNC increases from 0.05 for low-mass clusters (M_cl~1e12 Msun) to 0.5 for high-mass ones (M_cl>1e14 Msun), with no dependence on cluster redshift.  The values of Dv/s vary from 0 to 1.8.  These results are consistent with previous observational studies, and indicate that the central galaxy paradigm, which states the the BCG should be at rest at the center of the cluster, is usually valid, but exceptions are too common to be ignored.  Analysis of the merger trees for the 18 most massive clusters in the simulation reveals that 16 of these clusters have experienced major mergers in the past.  These mergers leave each cluster in a non-equilibrium state, but eventually the cluster settles into an equilibrium configuration, unless it is disturbed by another major merger.  Found evidence that these mergers are responsible for the off-center positions and peculiar velocities of some BCGs.  Results thus support the merging-group scenario, in which some clusters form by the merger of smaller groups in which the galaxies have already formed.