Browsing by Subject "galaxies : fundamental"

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The Hubble Space Telescope Advanced Camera for Surveys Coma Cluster Survey. I. Survey Objectives and Design
(2008-06) Carter, David; Goudfrooij, Paul; Mobasher, Bahram; Ferguson, Henry C.; Puzia, Thomas H.; Aguerri, Alfonso L.; Balcells, Marc; Batcheldor, Dan; Bridges, Terry J.; Davies, Jonathan I.; Erwin, Peter; Graham, Alister W.; Guzman, Rafael; Hammer, Derek; Hornschemeier, Ann; Hoyos, Carlos; Hudson, Michael J.; Huxor, Avon; Jogee, Shardha; Komiyama, Yutaka; Lotz, Jennifer; Lucey, John R.; Marzke, Ronald O.; Merritt, David; Miller, Bryan W.; Miller, Neal A.; Mouhcine, Mustapha; Okamura, Sadanori; Peletier, Reynier F.; Phillipps, Steven; Poggianti, Bianca M.; Sharples, Ray M.; Smith, Russell J.; Trentham, Neil; Tully, R. Brent; Valentijn, Edwin; Kleijn, Gijs Verdoes; Jogee, Shardha
We describe the HST ACS Coma Cluster Treasury survey, a deep two-passband imaging survey of one of the nearest rich clusters of galaxies, the Coma Cluster (Abell 1656). The survey was designed to cover an area of 740 arcmin(2) in regions of different density of both galaxies and intergalactic medium within the cluster. The ACS failure of 2007 January 27 leaves the survey 28% complete, with 21 ACS pointings (230 arcmin(2)) complete, and partial data for a further four pointings (44 arcmin(2)). The predicted survey depth for 10 sigma detections for optimal photometry of point sources is g' = 27.6 in the F475W filter and I-C = 26.8 mag in F814 (AB magnitudes). Initial simulations with artificially injected point sources show 90% recovered at magnitude limits of g' = 27.55 and I-C = 26.65. For extended sources, the predicted 10 sigma limits for a 1 arcsec(2) region are g' = 25.8 mag arcsec(-2) and I-C = 25.0 mag arcsec(-2). We highlight several motivating science goals of the survey, including study of the faint end of the cluster galaxy luminosity function, structural parameters of dwarf galaxies, stellar populations and their effect on colors and color gradients, evolution of morphological components in a dense environment, the nature of ultracompact dwarf galaxies, and globular cluster populations of cluster galaxies of a range of luminosities and types. This survey will also provide a local rich cluster benchmark for various well-known global scaling relations and explore new relations pertaining to the nuclear properties of galaxies.
The Munich Near-Infrared Cluster Survey. II. The K-Band Luminosity Function Of Field Galaxies To Z Similar To 1.2
(2003-10) Drory, Niv; Bender, Ralf; Feulner, G.; Hopp, Ulrich; Maraston, C.; Snigula, J.; Hill, Gary J.; Drory, Niv; Hill, Gary J.
We present a measurement of the evolution of the rest-frame K-band luminosity function to z similar to 1.2 using a sample of more than 5000 K-selected galaxies drawn from the Munich Near- Infrared Cluster Survey (MUNICS) data set. Distances and absolute K-band magnitudes are derived using photometric redshifts from spectral energy distribution fits to BVRIJK photometry. These are calibrated using more than 500 spectroscopic redshifts. We obtain redshift estimates having an rms scatter of 0.055 and no mean bias. We use Monte Carlo simulations to investigate the influence of the errors in distance associated with photometric redshifts on our ability to reconstruct the shape of the luminosity function. Finally, we construct the rest-frame K-band LF in four redshift bins spanning 0.4 < z < 1.2 and compare our results to the local luminosity function. We discuss and apply two different estimators to derive likely values for the evolution of the number density, Phi*, and characteristic luminosity, M*, with redshift. While the first estimator relies on the value of the luminosity function binned in magnitude and redshift, the second estimator uses the individually measured {M, z} pairs alone. In both cases we obtain a mild decrease in number density by similar to25% to z = 1, accompanied by brightening of the galaxy population by 0.5 - 0.7 mag. These results are fully consistent with an analogous analysis using only the spectroscopic MUNICS sample. The total K-band luminosity density is found to scale as d log rhoL/dz = 0.24. We discuss possible sources of systematic errors and their influence on our parameter estimates. By comparing the luminosity density and the cumulative redshift distributions of galaxies in single survey fields to the sample averages, we show that cosmic variance is likely to significantly influence infrared selected samples on scales of similar to 100 arcmin(2).
The Structure Of Classical Bulges And Pseudobulges: The Link Between Pseudobulges And Sersic Index
(2008-08) Fisher, David B.; Drory, Niv; Fisher, David B.
In this paper, we study the properties of pseudobulges (bulges that appear similar to disk galaxies) and classical bulges (bulges which appear similar to E-type galaxies) in bulge-disk decompositions. We show that the distribution of bulge Sersic indices, (n)b, is bimodal, and this bimodality correlates with the morphology of the bulge. Pseudobulges have n(b) less than or similar to 2 and classical bulges have n(b) less than or similar to 2 with little to no overlap. Also, pseudobulges do not follow the correlations of Sersic index with structural parameters or the photometric projections of the fundamental plane in the same way that classical bulges and elliptical galaxies do. We find that pseudobulges are systematically flatter than classical bulges and thus more disk-like in both their morphology and shape. We do not find significant differences between different bulge morphologies which we are collectively calling pseudobulges (nuclear spirals, nuclear rings, nuclear bars, and nuclear patchiness); they appear to behave similarly in all parameter correlations. In the Sersic index, flattening, and bulge-to-total ratio, the distinction appears to be between classical bulges and pseudobulges, not between different pseudobulge morphologies. The Sersic index of the pseudobulges does not correlate with B/T, in contrast to classical bulges. Also, the half-light radius of the pseudobulge correlates with the scale length of the disk; this is not the case for classical bulges. The correlation of Sersic index and scale lengths with bulge morphology suggests that secular evolution is creating pseudobulges with low-Sersic index and that other processes (e. g., major mergers) are responsible for the higher Sersic index in classical bulges and elliptical galaxies.