Day 427

Monday.

1305.0558
Gas surface density, star formation rate surface density, and the maximum mass of young star clusters in a disk galaxy. II. the grand-design galaxy M51
Gonzalez-Lopezlira, Pflamm-Altenburg, Kroupa

Relationshop between maximum cluster mass and surface density of total gas, molecular gas, neutral gas, and SFR of M51, using published gas data and a catalog of masses, ages, and reddening of more than 1800 star clusters in its disk of which 223 are above the cluster mass distribution function completeness limit.  For clusters older than 25 Myr, the median of the 5 most massive clusters is proportional to Simga_HI^0.4; no correlation with Sigma_gas, Sigma_H2 or Sigma_SFR.  For clusters younger than 10 Myr, M is proportional to Sigma_HI^0.6, Sigma_gas^0.5, but no correlation with H2 or SFR.  Very different from M33. 

1305.0560
On the stark difference in satellite distributions around the Milky Way and Andromeda
Yniguez, Garrison-Kimmel, Boylan-Kolchin, Bullock

Compare number counts of bright (>1e5 Lsun) dwarf satellite galaxies within 400 kpc of MW and M31; find MW satellites much more centrally concentrated.  Identical at the central 100 kpc, but M31 satellites outnumber MW satellites by about 4x at deprojected distances spanning 100-400 kpc.  Compare the observed distributions of those predicted for LCDM sub haloes using a suite of 44 high-res 1e12 halo zoom simulations, 22 of which are in pairs like MW and M31.  Find: radial distribution of satellites around M31 is fairly typical of those predicted for sub haloes, while the MW's distribution is more centrally concentrated than any of the simulated LCDM haloes.  Possible explanation: census of bright MW dwarf galaxies is significantly incomplete beyond ~100 kpc of the Sun.  Need 8~20 more satellite galaxies at the 100-400 kpc range to meet expectations.  Enough area left unexplored by SDSS and its extensions that the discovery of ~10 new bright dwarfs not implausible.

1305.0562
Nurturing Lyman break galaxies: observed link between environment and spectroscopic features
Cooke, Omori, Ryan-Weber

Examine effects of magnitude, color and Lya EW on the spatial distribution of z~3 LBGs and report significant differences on their auto-correlation functions (ACFs).  Use 10k-57k LBGs from CFHTLS.  Find: magnitude has a large effect on the ACF on small (<1 Mpc) scales; color more influential on large (>1Mpc) scales [what does color mean in LBGs?].  Find the most significant differences between ACFs for LBGs with dominant net Lya EW in absorption LBGs versus emission LBGs.  the aLBG ACF one-halo term departs from a power law fit near ~1 Mpc, corresponding to the virial radii of M_DM~1e13 Msun haloes, and shows a strong two-halo term amplitude.  In contrast, the eLBG ACF one-halo term departs at ~0.12 Mpc, suggesting parent haloes of M_DM ~1e11 Msun, and a two-halo term that exhibits a 'hump' on intermediate scales that are localized to the faintest, bluest members.  Find that the 'hump' can be well fit with a model in which a significant fraction of eLBGs reside on shells.  The auto- and cross-correlation functions indicate that aLBGs are found in massive, group-like haloes and that eLBGs are found largely on group outskirts and in the field [isolated LBGs glow in Lya emission; clustered LBGs have enough neutral H that we see absorption.  Makes sense if the baryon is proportional to DM (constant baryon fraction) in the Universe].  Lya is a tracer of several intrinsic LBG properties, including morphology, implying that the mechanisms behind the morphology-density relation are in place at z~3 and that Lya EW may be a key environment diagnostic.  Finally, results show that the mass of LBGs has been underestimated because the LBG ACF amplitude is lower than the true average as a result of the spatial anti-correlation of the spectral sub-types.

1305.0563
Anisotropic halo model
Sgro, Paz, Merchan

Include triaxial halo model for profiles and their alignments, to the classic halo model of LSS distribution.  From numerical integration, obtain instances of the cross-correlation function depending on the directions given by halo shape axes.  These functions are called anisotropic cross-correlations.  Compare theoretical results with simulations: compute averaged anisotropic correlations in cones with their symmetry axis along each shape direction of the centre halo.  From these comparisons, characterise and quantify the alignment of DM haloes on the LCDM context by means of the presented anisotropic halo model.  Model requires multidimensional integral computation; implement a MC method on GPU hardware that allows increase in precision.

1305.0607
CANDELS observations of the environmental dependence of the color-mass-morphology relation at z=1.6
Bassett, ... Bell, Newman, Tran, ... Koekemoer, Koo, Wechsler, et al

Environmental dependence of color, stellar mass, and morphology from comparison of galaxies in a forming cluster to those in the field at z=1.6 with HST NIR imaging in CANDELS/UDS field.  Quantify morphology of galaxies using effective radius, reff, and Sersic index, n.  In both the cluster and field, approximately half of the bulge-dominated galaxies (n>2) reside on the red sequence for the color-magnitude diagram, and most disk-dominated galaxies (n<2) have colors expected for SF galaxies.  Weak evidence that cluster galaxies have redder rest-frame U_B colors and higher stellar masses compared to the field.  SF galaxies in both the cluster and field show no significant differences in their morphologies.  In contrast, there is evidence that quiescent galaxies in the cluster have larger median effective radii and smaller Sersic indices compared to the field with a significance of 2 [sigma?].  [Are there field quiescent galaxies?... I guess so, according to the recent Wetzel+ paper, the 'ejected' satellites.  But why are they more disk-like (smaller n) in the cluster?]  These differences are most pronounced for galaxies at cluster centric distances 1Mpc < R_proj < 1.5 Mpc, which have low Sersic indices and possibly larger effective radii, more consistent with SF galaxies at this epoch and in contrast to other quiescent galaxies.  Argue that SF galaxies are processed under the influence of the cluster environment at distances greater than the cluster-halo virial radius.  Results are consistent with models where gas accretion onto these galaxies is suppressed from processes associated with the cluster environment.

1305.0724
The excursion set approach in non-Gaussian random fields
Musso, Sheth

Study first-crossing distributions of physically motivated barriers by random walks with correlated steps: higher mass objects are associated with walks that take fear steps before crossing the barrier.  Show how to write the first crossing distribution as a formal series, ordered by the minimum number of times a walk upcrosses the barrier.  The leading order term in the series is the most relevant for understanding massive objects of interest in cosmology.  This first term only requires knowledge of the bivariate distribution of the walk height and slope, and provides an excellent approximation to the first crossing distribution for all barriers and smoothing filters of current interest.  Simplicity survives when extending to non-G random fields.

1305.0793
The effective number density of galaxies for weak lensing measurements in the LSST project
Chang, Jarvis, Jain, Kahn, Kirkby, Connolly, ... et al

Statistical power of WL survey is determined by the sky coverage, the inverse of the noise in shape measurements, and the galaxy number density.  The combination of the latter two factors is often expressed in terms of n_eff.  Estimate n_eff for LSST.  Investigate how the following factors affect the resulting n_eff of the survey with detailed simulations: (1) survey time, (2) shear measurement algorithm, (3) algorithm for combining multiple exposures, (4) inclusion of data from multiple filter bands, (5) redshift distribution of the galaxies, and (6) masking and blending.  For the first time, quantify in a general WL analysis pipeline the sensitivity of n_eff to the above factors.  Find that with current WL algorithms, expected distributions of observing parameters, and all lensing data (r- and i-band, covering 18k deg^2 of sky) for LSST, n_eff~37 gal/arcmin^2 before considering blending and masking, n_eff~31 gal/arcmin^2 when rejecting seriously blended galaxies and n_eff~26 gal/arcmin^2 when considering an additional 15% loss of galaxies due to masking.  With future improvements in WL algorithms, these values could be expected to increase by up to 20%.  Throughout the paper, also stressed the ways in which n_eff depends on the ability to understand and control systematic effects in the measurements.

1305.0819
AGN and QSOs in the eROSITA All-sky survey -- Part II: studies of large-scale structure
Kolodzig, Gilfanov, Hütsi, Sunyaev

The 4 year x-ray all-sky survey (eRASS) of eROSITA on Spektrum-Roentgen-Gamma satellite will detect 3 million AGN with a median redshift of z~1 and L(0.5-2.0 keV)~1e44 erg/s.  This will supply us with LSS structure research: redshift and luminosity resolved studies of the bias factor for X-ray selected AGN will be possible; the eRASS AGN sample will not only improve the redshift and L resolution of these studies but will also expand their L range, thus making possible direct comparison of clustering properties of luminous X-ray AGN and optical quasars.  These studies will dramatically improve the understanding of AGN environment, triggering mechanisms, growth of SMBH and their co-evolution with DM haloes. The eROSITA AGN sample will be a powerful cosmological probe.  It will make possible detection of BAO with X-ray selected AGN.  With the data from the entire extragalactic sky, BAO will be detected at ~10 sigma CL in full redshift range and with ~8sigma CL in the 0.8<z<2.0 range.  For full potential of eRASS AGN sample, photometric and spectroscopic surveys of large area and sufficient depth will be needed.