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J/ApJ/721/98        Morphology of 70um COSMOS galaxies       (Kartaltepe+, 2010)

A multiwavelength study of a sample of 70 µm selected galaxies in the COSMOS field. II. The role of mergers in galaxy evolution. Kartaltepe J.S., Sanders D.B., Le Floc'h E., Frayer D.T., Aussel H., Arnouts S., Ilbert O., Salvato M., Scoville N.Z., Surace J., Yan L., Capak P., Caputi K., Carollo C.M., Cassata P., Civano F., Hasinger G., Koekemoer A.M., Le Fevre O., Lilly S., Liu C.T., McCracken H.J., Schinnerer E., Smolcic V., Taniguchi Y., Thompson D.J., Trump J., Baldassare V.F., Fiorenza S.L. <Astrophys. J., 721, 98-123 (2010)> =2010ApJ...721...98K
ADC_Keywords: Galaxies, IR ; Redshifts ; Morphology ; Surveys Keywords: cosmology: observations - galaxies: active - galaxies: evolution - galaxies: high-redshift - infrared: galaxies - surveys Abstract: We analyze the morphological properties of a large sample of 1503 70um selected galaxies in the COSMOS field spanning the redshift range 0.01<z<3.5 with a median redshift of 0.5 and an infrared luminosity range of 108<LIR(8-1000um)<1014L with a median luminosity of 1011.4L. In general, these galaxies are massive, with a stellar mass range of 1010-1012M, and luminous, with -25<MK←20. The precise fraction of mergers in any given LIR bin varies by redshift due to sources at z>1 being difficult to classify and subject to the effects of bandpass shifting; therefore, these numbers can only be considered lower limits. At z<1, where the morphological classifications are most robust, major mergers clearly dominate the ULIRG population (∼50%-80%) and are important for the LIRG population (∼25%-40%). At z>1, the fraction of major mergers is lower, but is at least 30%-40% for ULIRGs. In a comparison of our visual classifications with several automated classification techniques we find general agreement; however, the fraction of identified mergers is underestimated due to automated classification methods being sensitive to only certain timescales of a major merger. The distribution of the U-V color of the galaxies in our sample peaks in the green valley (<U-V≥1.1) with a large spread at bluer and redder colors and with the major mergers peaking more strongly in the green valley than the rest of the morphological classes. Description: The 70um sample used in this study was selected from the Spitzer-MIPS coverage of the COSMOS field taken during cycles 2 and 3. The main optical imaging data used for this study were obtained as a part of the COSMOS Treasury project with HST using the Advanced Camera for Surveys (ACS) and the F814W filter (FWHM=0.09"). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 138 1503 Morphological catalog of COSMOS 70um sources
See also: B/hst : HST Archived Exposures Catalog (STScI, 2007) VII/265 : COSMOS Morphological Catalog (V1.1) (Tasca+ 2009) II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007) J/ApJ/709/572 : COSMOS 70um sources (Kartaltepe+, 2010) J/AJ/138/1261 : Spitzer/MIPS observations of the COSMOS field (Frayer+, 2009) J/ApJ/680/939 : Optical spectra of 24um galaxies in COSMOS. I. (Caputi+, 2008) J/ApJS/172/70 : zCOSMOS-bright catalog (Lilly+, 2007) J/ApJ/696/1195 : COSMOS AGN spectroscopic survey. I. (Trump+, 2009) J/ApJS/172/383 : AGN candidates in the COSMOS field (Trump+, 2007) J/A+A/468/937 : K-band AO imaging in COSMOS deep field (Huertas-Company+, 2007) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 4 I4 --- Seq [1017/5401] Source identification number (as in Paper I) (1) 6- 11 A6 --- --- [COSMOS] 13- 33 A21 --- COSMOS Source name ( 35- 39 F5.2 [Lsun] LIR Log of total IR luminosity (1) 41- 44 F4.2 [Lsun] e_LIR Uncertainty in LIR 46- 50 F5.3 --- z [0.01/3.5] Redshift 52- 54 A3 --- f_z Origin of z (P=photometric) (2) 56- 64 A9 --- Class Morphological classification (3) 66- 71 F6.2 kpc Sep ?=-99 Nuclear separation between galaxy pairs and double nuclei 73- 79 F7.2 --- Ratio [1,]?=-99 Mass ratio (4) 81- 85 F5.2 [Msun] Mass Log of stellar mass (5) 87- 93 F7.2 mag KMag [-120.56/-12.94] Rest-frame absolute K band magnitude 95- 99 F5.2 mag U-V Rest-frame (U-V) color index 101-106 F6.2 --- C ?=-99 Concentration parameter 108-113 F6.2 --- A ?=-99 Rotational asymmetry parameter 115-120 F6.2 --- Clump ?=-99 Clumpiness parameter 122-127 F6.2 --- Gini ?=-99 Gini coefficient 129-134 F6.2 --- M20 ?=-99 M20 brightness measure 136-138 I3 --- Acl [1/3]?=-99 Automated classification (1=early, 2=late, 3=irregular) (6)
Note (1): Derived from SED template fitting described in Paper I (Kartaltepe et al., 2010, Cat. J/ApJ/709/572). Note (2): Flag as follows: D = DEIMOS spectroscopy on Keck II; Z = zCOSMOS spectroscopy from VLT/VIMOS; I = IMACS spectroscopy from Magellan; S = SDSS spectroscopy; 2dF = 2dFGRS spectroscopy; F = FORS1 spectroscopy; M = Hectospec spectroscopy from MMT; P = Photometric redshift from Ilbert et al. (2009ApJ...690.1236I) or Salvato et al. (2009ApJ...690.1250S). Note (3): Morphological classification and interaction class as follows: S = spiral (this category includes barred and edge on spirals); E = elliptical (S0 galaxies are included in this category with the usual caveat that it can be difficult to distinguish between spirals and S0s, especially at large inclinations); Q = QSO (galaxy with a central point source. In most cases, the QSO overwhelms the host galaxy such that no other information can be discerned about its structure); U = unknown (galaxies in this category are too faint or small to classify into any of the other categories or are irregular but not clearly mergers); m = minor merger (galaxies with a slightly disturbed morphology (e.g., warped disks, asymmetric spiral arms, etc.) and no evidence for a large companion (and therefore not likely to be early stage major mergers) or a small companion at the same redshift); M = Major merger; I-V = interaction classes : Stage I, the galaxy has a companion at the same redshift; stage II, the two galaxies overlap but have not yet formed strong tidal features; stage III, the galaxy is either a member of a pair or a single system with two nuclei (a: nuclear separation>10kpc or b: nuclear separations<10kpc); stage IV, after the coalescence of the two objects into a single nucleus; and stage V, these objects have no tidal features but do still have disturbed central morphologies and possibly knots of star formation and surrounding debris. G = group (a small fraction of the galaxies in our sample appear to be a member of a close group of three or more objects. All of these objects are also classified into one of the above interaction classes, but we include this category to note which are part of a larger group). See section 3.1 for further details. Note (4): Ratio of the galaxy stellar masses for galaxy pairs with resolved optical photometry. Note (5): Determined from the photometry. For galaxy pairs that are resolved in the optical photometry catalog, this mass refers to the optical counterpart whose coordinates are given. For those that are not resolved, the mass is the combined mass of the system. The combined mass for the resolved pairs can be obtained using the mass ratio given. Note (6): From Cassata et al. (2010ApJ...714L..79C) as follows: 1 = early type; 2 = late type; 3 = irregular;
History: From electronic version of the journal References: Kartaltepe et al. Paper I. 2010ApJ...709..572K Cat. J/ApJ/709/572
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Jul-2012
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