COSMOS Morphological Classification with the Zurich Estimator of Structural Types (ZEST) and the Evolution Since z = 1 of the Luminosity Function of Early, Disk, and Irregular Galaxies

By Claudia Scarlata, C. Carollo, S. Lilly, M. Sargent, Robert Feldmann, P. Kampczyk, C. Porciani, A. Koekemoer, N. Scoville, Jean-Paul Kneib and 19 more. 2006

205 citations recorded by the source corpus.

Motivated by the desire to reliably and automatically classify structure of thousands of COSMOS galaxies, we present ZEST, the Zurich Estimator of Structural Types. To classify galaxy structure, ZEST uses (1) five nonparametric diagnostics: asymmetry, concentration, Gini coefficient, second-order moment of the brightest 20% of galaxy pixels, and ellipticity; and (2) the exponent n of single-Sérsic fits to the two-dimensional surface brightness distributions. To fully exploit the wealth of information while reducing the redundancy present in these diagnostics, ZEST performs a principal component (PC) analysis. We use a sample of ~56,000 IAB ≤ 24 COSMOS galaxies to show that the first three PCs fully describe the key aspects of the galaxy structure, i.e., to calibrate a three-dimensional classification grid of axes PC1, PC2, and PC3. We demonstrate the robustness of the ZEST grid on the z = 0 sample of Frei et al. The ZEST classification breaks most of the degeneracy between different galaxy populations that affects morphological classifications based on only some of the diagnostics included in ZEST. As a first application, we present the evolution since z ~ 1 of the luminosity functions (LFs) of COSMOS galaxies of early, disk, and irregular galaxies and, for disk galaxies, of different bulge-to-disk ratios. Overall, we find that the LF up to a redshift z = 1 is consistent with a pure luminosity evolution (of about 0.95 mag at z ~ 0.7). We highlight, however, two trends that are in general agreement with a downsizing scenario for galaxy formation, i.e., (1) a deficit of a factor of about 2 at z ~ 0.7 of MB > -20.5 structurally classified early-type galaxies and (2) an excess of a factor of about 3, at a similar redshift, of irregular galaxies.

Subfields: Astronomy and Astrophysics, Ecology, Instrumentation

View Paper: https://www.semanticscholar.org/paper/151e27b9df825fcca2625c27f12e7ffa4b252075

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Citations in the corpus

THE BULK OF THE BLACK HOLE GROWTH SINCE z ∼ 1 OCCURS IN A SECULAR UNIVERSE: NO MAJOR MERGER–AGN CONNECTION (2010, methodology): “As a second test, we look up the results for our comparison sample from the Zurich Estimator of Structural Types (ZEST, see Scarlata et al. 2007 for details), in which the structure of thousands of COSMOS galaxies was quantified through a principal component analysis over a combination of Sérsic…”
Galaxy morphology and star formation in the Illustris Simulation at z = 0 (2015, methodology): “We show data from Scarlata et al. (2007), who computed morphologies with the Zurich Estimator of Structural Types (ZEST), and show the full samples in the black contours which represent 68% and 95% of the populations.”
Photometric Redshifts of Galaxies in COSMOS (2006, background): “…2007), to study the evolution of density-morphology relation (Capak et al. 2007a), to study dependence of the star formation activity on the environment (Mobasher et al. 2007) and to study morphologies and rest-frame properties of individual galaxies (Scarlata et al. 2007; Zamojski et al. 2007).”
HiZELS:a high-redshift survey of Hα emitters - II. the nature of star-forming galaxies at z = 0.84 (2009, methodology): “In order to compare those results with morphologies obtained in an automated way (by ZEST, kindly supplied by Claudia Scarlata, Scarlata et al. (2007)), 4 morphological classes were used: 1) Earlytypes, 2) Disks/spirals, 3) Irregulars, and 4) Unclassified.”
zCOSMOS – 10k-bright spectroscopic sample - The bimodality in the galaxy stellar mass function: exploring its evolution with redshift (2009, methodology): “…multiband photometric coverage (from UV to IRAC) and morphological classifications, along with morphological parameters from both the Zurich Estimator of Structural Types (ZEST; Scarlata et al. 2007a) and estimates obtained in Marseille (Cassata et al. 2008, Tasca et al. 2009, MRS hereafter).”
Bolometric luminosities and Eddington ratios of X-ray selected active galactic nuclei in the XMM-COSMOS survey (2012, methodology): “We use secure morphological information for 144 Type-2 AGN obtained from the updated Zurich Estimator of Structural Types (ZEST; Scarlata et al. 2007), known as ZEST+ (Carollo et al. 2012, in preparation).”
Tracking the impact of environment on the galaxy stellar mass function up to z ~ 1 in the 10 k zCOSMOS sample (2009, methodology): “As morphological classification we adopted the one presented in Scarlata et al. (2007): the availability of deep F814band ACS@HST images over the whole COSMOS field (Koekemoer et al. 2007) allows a good determination of the structural parameters on which the morphology derived with the software…”
NEWLY QUENCHED GALAXIES AS THE CAUSE FOR THE APPARENT EVOLUTION IN AVERAGE SIZE OF THE POPULATION (2013, methodology): “Morphological Classification The morphological classifications were derived with the Zurich Estimator of Structural Types Plus (ZEST+), an upgraded version of the ZEST approach described in detail in Scarlata et al. (2007a).”
CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. I. DETAILED REST-FRAME OPTICAL MORPHOLOGIES ON KILOPARSEC SCALE OF z ∼ 2 STAR-FORMING GALAXIES (2010, background): “…and disk-like types at higher redshift compared to the local galaxy population (e.g., Lotz, Primack, & Madau 2004; Lotz et al. 2006; Law et al. 2007a; Scarlata et al. 2007a,b; Elmegreen et al. 2007; Pannella et al. 2009), hinting at the diversity of processes driving early galaxy evolution.”
Galaxy Zoo: morphologies derived from visual inspection of galaxies from the Sloan Digital Sky Survey (2008, methodology): “…based on galaxy properties such as colour, concentration index, spectral features, surface brightness profile, structural parameters or some combination of these are used (e.g. Strateva et al. 2001; Abraham, van den Bergh & Nair 2003; Kauffmann et al. 2004; Conselice 2006; Scarlata et al. 2007).”
The Herschel* PEP/HerMES luminosity function - I. Probing the evolution of PACS selected Galaxies to z ≃ 4 (2013, result): “…∼2.5 between z=0 and z=1 for the spiral LF, in good agreement with previous results, either empirical (for morphologically classified disky galaxies; Scarlata et al. 2007) or c© 2012 RAS, MNRAS 000, 2–29 theoretical (from chemical evolution models of Milky Waylike galaxies; Colavitti, Matteucci…”
Galaxy Zoo: Disentangling the Environmental Dependence of Morphology and Colour ⋆ (2008, background): “…or structural properties of galaxies, such as Sersic index, surface brightness, r90/r50 concentration, and their combinations (Blanton et al. 2005, Christlein & Zabludoff 2005, Conselice 2006, Scarlata et al. 2007, Park et al. 2007, van den Bosch et al. 2008a, Ball et al. 2008, van der Wel 2008).”
Physical properties and environments of nearby galaxies (2009, methodology): “…with simple cuts in parameter space (e.g., Choi, Park & Vogeley 2007), with the aid of dimensionality reduction techniques like principal component analysis (e.g., Ellis et al. 2005; Scarlata et al. 2007), or using artificial neural networks (e.g., Storrie-Lombardi et al. 1992; Ball et al. 2004).”
The dependence of star formation activity on environment and stellar mass at z∼ 1 from the HiZELS-Hα survey (2010, methodology): “Visual classifications were also obtained by S09a for Hα emitters at z = 0.84; the authors find that the two agree very well, with only small differences arising from the use of colour information in S09a (from Subaru data), while ZEST uses the HST F814W imaging only.”
THE RADIAL AND AZIMUTHAL PROFILES OF Mg ii ABSORPTION AROUND 0.5 < z < 0.9 zCOSMOS GALAXIES OF DIFFERENT COLORS, MASSES, AND ENVIRONMENTS (2011, methodology): “To study the azimuthal dependence on Mg II absorption line strength, we use the ZEST morphological classification (Scarlata et al. 2007) for each potential foreground galaxy.”