Day 645

Friday.

1405.0008
The SLUGGS survey: HST/ACS mosaic imaging of the NGC 3115 Globular cluster system
Jennings et al

Present gand z photometry and HLR Rh measurements of 360 GC candidates around the nearby S0 galaxy NGC 3115.  Also include Subary gri photometry of 421 additional candidates.  The well established color bimodality of the GC system is obvious in the HST photometry.  Find evidence for a "blue tilt" in the blue GCs, wherein the blue GCs get redder as luminosity increases, indicative of a mass-metallicity relationship.  Find a color gradient in both the red and blue subpopulations, with each group of clusters becoming bluer at larger distances from NGC 3115.  The gradient is of similar strength in both subpopulations, but is monotonic and more significant for the blue clusters.  On average, the blue clusters have ~10% larger Rh than the red clusters.  This average difference is less than is typically observed for early-type galaxies but does match that measured in the literature for M104, suggesting that morphology and inclination may affect the measured size difference between the red and blue clusters.  However, the scatter on the Rh measurements is large.  Also identify 31 clusters more extended than typical GCs, which are considered UCD (ultra-compact dwarf) candidates.  Many of these objects are fainter than typical UCDs.  While it is likely that a significant number will be BG contaminants, 6 of these UCD candidates are spectroscopically confirmed.  To explore low-mass X-ray binaries in the GC system, match ACS and Suprime-Cam detections to corresponding Chandra X-ray sources.  Identify 45 X-ray-GC matches, 16 among the blue subpopulation and 29 among the red subpopulation.  These X-ray/GC coincidence fractions are larger than is typical for most GC systems, probably due to the increased depth of the X-ray data compared to previous studies of GC systems.

1405.0011
Frontier Fields: high-redshift predictions and early results
Coe, Bradley, Zitrin

The Frontier Fields program is obtaining deep Hubble and Spitzer images of new "blank" fields and nearby fields gravitationally lensed by massive galaxy clusters.  The Hubble images of the lensed fields are revealing nJy sources (ABmag>31), the faintest galaxies yet observed.  In this paper, present high-z (>6) number count predictions for the full program and candidates in 3 of the first Hubble FF images.  The full program will transform the understanding of galaxy evolution in the first 600 million years (z>9).  Where previous programs yielded perhaps a dozen z>9 candidates, the FF may yield ~70 (~6 per field).  Base this estimate on an extrapolation of luminosity functions observed between 4<z<8 and gravitational lensing models submitted by the community.  However, in the first 2 deep IR Hubble images obtained to date, find z~8 candidates but no strong candidates at z>9.  This might suggest a deficit of faint z>9 galaxies as also reported in the UDF (even while excesses of brighter z>9 galaxies were reported in shallower fields).  A these z, cosmic variance (field-to-field variation) is expected to be significant (>pm50%) and include clustering of early galaxies formed in over densities.  The full FF program will significantly mitigate this uncertainty by observing 6 independent sight lines each with a lensing cluster and nearby blank field.

1405.0016
The origin of the atomic and molecular gas contents of early-type galaxies.  I.  A new test of galaxy formation physics
Lagos, Davis, Lacey, Zwaan, Baugh, Gonzalez-Perez, Padilla 

Study the HI and H2 gas contents of ETGs and their gas soured using GALFORM model of galaxy formation, which is set in the LCDM framework.  This model uses a self-consistent calculation of the SFR, which depends on the H2 content of the galaxies.  First present a new analysis of HIPASS and ATLAS3D surveys, which special emphasis on ETGs.  The model predictions for the HI and H2 gas contents of ETGs agree with the observations from these surveys only if partial ram pressure stripping of the hot gas is included.  Find that the neutral gas content of ETGs is much more sensitive to the way environmental quenching proceeds than the colors of galaxies.  Show how observations of HI and H2 in different galaxy populations place stringent constraints on the treatment of the hot gas content of satellites.  Find that ~90% of ETGs at z=0 have their neutral gas content mainly supplied by radiative cooling from their hot haloes, 8% have been supplied by gas accretion from minor mergers that took place in the last 1 Gyr, while 2% were supplied by mass loss from intermediate and low-mass stars.  In galaxy clusters, the percentage of ETGs with HI and H2 contents supplied by mass loss from old stars increases to >7%.  Show how the neutral gas fraction in galaxies strongly decreases with increasing bulge fraction, evidencing the connection between bulge fraction and quenching of SF.  This is due to the absence of disk regeneration in ETGs as a result of AGN feedback and environmental quenching by partial ram pressure stripping of the hot gas.

1405.0222
Lens models and magnification maps of the six Hubble Frontier Fields clusters
Johnson, .. Gladders, Coe, Ebeling et al

Present SL models, as well as mass and magnification maps, fro the cores of the 6 HST FF galaxy clusters.  Use available data for A2744 and AS1063.  Then (1) Compare the derived mass distribution of each cluster to its light distribution, (2) quantify the cumulative magnification power of the HFF clusters, (3) describe how the models can be used to estimate the magnification and image multiplicity of lensed BG sources at all redshifts and at any position within the cluster cores, and (4) discuss systematic effects and caveats resulting from the modeling methods.  Specifically investigate the effect of the use of spectroscopic and photometric z constraints on the uncertainties of the resulting models.  Find that the photometric z estimates of lensed galaxies are generally in excellent agreement with spectroscopic z, where available.  However, the flexibility associated with relaxed redshift priors may cause the complexity of large-scale structure that is needed to account for the lensing signal to be underestimated.  Findings thus underline the importance of spectroscopic arc redshifts, or tight photometric z constrains, for high precision lens models. All products from the best-fit lens models (magnification, convergence, shear, deflection field) and model simulations for estimating errors are made available via the Mikulski Archive for Space Telescopes.