Day 411

Saturday.


1304.2939
The two regimes of the cosmic sSFR evolution are due to spheroids and discs
Pipino, Calura, Matteucci

Aim to explain the two phases in the observed sSFR, namely the high (>3/Gyr) values at z>2 and the smooth decrease since z=2.  In order to do this, compare to observations the sSFR evolution predicted by well calibrated models of chemical evolution for elliptical and spiral galaxies, using the additional constraints on the mean stellar ages of these galaxies (at a given mass).  Conclude that the two phases of the sSFR evolution across cosmic time are due to different populations of galaxies.  At z>2 the contribution comes from spheroids: the progenitors of present-day massive ellipticals (which feature the highest sSFR) as well as haloes and bulges in spirals (which contribute with average and lower-than-average sSFR).  In each single galaxy the sSFR decreases rapidly and the SF stops in <1Gyr.  However the combination of different generations of ellipticals in formation might result in an apparent lack of strong evolution of the sSFR (averaged over a population) at high redshift.  The z<2 decrease is due to the slow evolution of the gas fraction in discs, modulated by the gas accretion history and regulated by the Schmidt law.  The MW makes no exception to this behavior.  

1304.2963
Observational evidence that massive cluster galaxies were forming stars at z~2.5 and did not grow in mass at later times
Andreon

As the title says.  Related to subject above.  Data from Spitzer and LF, MF of galaxies in five z>1.4 clusters.  L* does not evolve between z=1 and 1.8.  z>1.8 as the remaining epoch for the mass build up.

1304.3124
The impact of global environment of galaxy mass functions at low redshift
Calvi, Poggianti, Vulcani, Fasano

Study the galaxy stellar mass function in different environments in the local Universe, considering both the total mass function and that of individual galaxy morphological types.  Compare the MF of galaxies with M*>1e10.25 in the general field and in galaxy groups, binary and single galaxy systems from Padova-Millennium Galaxy and Group Catalog at z=0.04-0.1 with the MF of galaxy clusters of the Wide Field NEarby Galaxy-Cluster Survey at z=0.04-0.07.  The variations of the MF with global environment overall are small and subtle.  The shapes of the MF of the general field and clusters are indistinguishable (some variation in groups).  On the MF of single galaxies, representing the least massive haloes and comprising less than a third of the general field population, is proportionally richer in low-mass galaxies than other environments.  The most notable environmental effect is a progressive change in the upper galaxy mass, with very massive galaxies found only in the most massive environments.  This environment-dependent mass cut-off is unable to affect the Schechter parameters and the K-S test, and can only be revealed by an ad-hoc analysis.  Show how in each given environment, the MF changes with morphological type, and that galaxies of the same morphological type can have different MF in different environments.

1304.3127
A new approach to identifying the most powerful gravitational lensing telescopes
Wong, Zabludoff, Ammons, Keeton, Hogg, Gonzalez

Best GL's for detecting distant galaxies are those with the largest mass concentrations and the most advantageous configurations of that mass along the LoS.  New method for finding such GL telescopes uses optical data to identify projected concentrations of LRGs.  LRGs are biased tracers of the underlying mass distribution, so LoS with the highest total luminosity in LRGs are likely to contain the largest total mass.  Apply this selection technique to the SDSS and identify the 200 fields with the highest total LRG luminosities projected within a 3.5' radius over 0.1<z<0.7.  The redshift and angular distributions of LRGs in these fields trace the concentrations of non-LRG galaxies.  These fields are diverse; 22.5% contain one known galaxy cluster and 56% contain multiple known clusters previously identified in the literature.  Thus, results confirm that these LRGs trace massive structures and that selection technique identifies fields with large total masses.  These fields contain 2-3 times higher total LRG luminosities than most known SL clusters and will be among the best GL fields for the purpose of detetcing the highest z galaxies.

1304.3171
Exploring the interstellar media of optically compact dwarf galaxies
Most, Cannon, Salzer, Rosenberg, Engstrom, Fliss

Present 8 SF blue compact dwarf galaxies selected to be optically compact (<1 kpc optical radii), with HI spectral data, with archival SDSS and Spizter data.  These systems have faint blue absolute magnitudes (M_B>=-17), ongoing SF (based on emission-line selection by the Ha or [OIII] lines), and are nearby (45 Mpc).  One sample found to have an HI halo that extends 58 r-band scale lengths from its stellar body.  In contrast, the rest of the sample galaxies have HI radii to optical-scale-length ratios ranging from 9.3 to 26.  The size of the HI disk in the "giant disk" dwarf galaxy ADBS113845+2008 appears to be unusual as compared to similarly compact stellar populations.

1304.3174
The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the commissioning observations and the pilot surveys
Huo et al

Present 509 new quasars discovered during the 2010 and 2011 observational seasons in ~135 sq. deg, and 17 new in ~100 sq. deg.  These bright quasars provide an opportunity to probe the kinematics and chemistry of the ISM/IGM in the Local Group of galaxies, providing a perfect astrometric reference frame to measure the proper motions of M31 and M33, as well as substructures of LG.

1304.3230
FIR-detected Lyman break galaxies at z~3: dust attenuation and dust correction factors at high redshift
Oteo et al

LBGs are SF galaxies in high-z; detection of LBGs in FIR provide clues on their dust attenuation and total SFR.  Explore the FIR emission of a sample of 16 LBGs at z~3 in the GOODS-North and GOODS-South fields that are individually detected in PACS-100um or PACS-160um.  These detections demonstrate the possibility of measuring the dust emission of LBGs at high redshift.  Find that PACS-detected LBGs at z~3 are highly obscured galaxies which belong to the ULIRG or HLIRG class.  Their total SFR cannot be recovered with the dust attenuation factors obtained from their UV continuum slope of their SED-derived dust attenuation employing Bruzual & Charlot (2003) templates.  Both methods underestimate the results [SFR results?] for most of the galaxies.  Comparing with a sample of PACS-detected LBGs at z~1, find evidences that the FIR emission of LBGs might have changed with redshift in the sense that the dustiest LBGs found at z~3 have more prominent FIR emission, are dustier for a given UV slope, and have higher SFR for a given stellar mass than the dustiest LBGs found at z~1.  

1304.3335
The evolution of dusty star formation in galaxy clusters to z=1: Spitzer IR observations of the first red-sequence cluster survey
Webb,..  Yee, ... Gladders, et al

From 42 clusters of 1e14-15 Msun in 0.3<z<1.0 from RCS-1, show number of IR luminous galaxies in clusters per unit cluster mass evolves as (1+z)^(5 pm 2); these results assume a single SF galaxy template; the presence of AGN, and an evolution in their relative contribution to the MIR galaxy emission, will alter the overall number counts per cluster and their rate of evolution.  Evolution of total SFR per unit cluster mass can be attributed entirely to the change in the in-falling field galaxy population.  The SFR per unit cluster mass (binned over all redshift) decreases with increasing cluster mass, consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally.  The inferred SF seen here could produce 5-10% of the total stellar mass in massive clusters at z=0.  Finally, show a clear decrease in the number of IR-bright galaxies per unit optical galaxy in the cluster cores, confirming SF continues to avoid the highest density regions of the universe at z~0.75 (the avg. z of the high-z clusters).  While several previous studies appear to show enhanced SF in high-redshift clusters relative to the field, note that these papers have not accounted for the overall increase in galaxy or DM density at the location of clusters.  Once this is done, clusters at z~0.75 have the same or less SF per unit mass or galaxy as the field.