J/ApJ/753/121 zCOSMOS 20k sample group catalog to z≲1.2 (Knobel+, 2012)
The zCOSMOS 20k group catalog.
Knobel C., Lilly S.J., Iovino A., Kovac K., Bschorr T.J., Presotto V.,
Oesch P.A., Kampczyk P., Carollo C.M., Contini T., Kneib J.-P.,
Le Fevre O., Mainieri V., Renzini A., Scodeggio M., Zamorani G.,
Bardelli S., Bolzonella M., Bongiorno A., Caputi K., Cucciati O.,
de la Torre S., de Ravel L., Franzetti P., Garilli B., Lamareille F.,
Le Borgne J.-F., Le Brun V., Maier C., Mignoli M., Pello R., Peng Y.,
Perez Montero E., Silverman J., Tanaka M., Tasca L., Tresse L., Vergani D.,
Zucca E., Barnes L., Bordoloi R., Cappi A., Cimatti A., Coppa G.,
Koekemoer A.M., Lopez-Sanjuan C., McCracken H.J., Moresco M., Nair P.,
Pozzetti L., Welikala N.
<Astrophys. J., 753, 121 (2012)>
=2012ApJ...753..121K 2012ApJ...753..121K
ADC_Keywords: Galaxy catalogs ; Redshifts
Keywords: catalogs; cosmology: observations; galaxies: evolution;
galaxies: groups: general; large-scale structure of universe;
methods: data analysis
Abstract:
We present an optical group catalog between 0.1≲z≲1 based on 16500
high-quality spectroscopic redshifts in the completed zCOSMOS-bright
survey. The catalog published herein contains 1498 groups in total and
192 groups with more than five observed members. The catalog includes
both group properties and the identification of the member galaxies.
Based on mock catalogs, the completeness and purity of groups with
three and more members should be both about 83% with respect to all
groups that should have been detectable within the survey, and more
than 75% of the groups should exhibit a one-to-one correspondence to
the "real" groups. Particularly at high redshift, there are apparently
more galaxies in groups in the COSMOS field than expected from mock
catalogs. We detect clear evidence for the growth of cosmic structure
over the last seven billion years in the sense that the fraction of
galaxies that are found in groups (in volume-limited samples)
increases significantly with cosmic time. In the second part of the
paper, we develop a method for associating galaxies that only have
photo-z to our spectroscopically identified groups. We show that this
leads to improved definition of group centers, improved identification
of the most massive galaxies in the groups, and improved
identification of central and satellite galaxies, where we define the
former to be galaxies at the minimum of the gravitational potential
wells. Subsamples of centrals and satellites in the groups can be
defined with purities up to 80%, while a straight binary
classification of all group and non-group galaxies into centrals and
satellites achieves purities of 85% and 75%, respectively, for the
spectroscopic sample.
Description:
In this paper we present a new group catalog produced with the
zCOSMOS-bright survey (Lilly et al. 2007, Cat. J/ApJS/172/70), which
now contains about 16500 high-quality spectroscopic galaxies with
IAB≤22.5 in the redshift range 0.1≲z≲1.2 (the "20k sample").
zCOSMOS-bright covers the ∼1.7deg2 of the COSMOS field which was
fully observed by the Hubble Space Telescope down to IAB<28
(5σ) and followed up in more than 30 bands by several telescopes
from radio to X-ray wavelengths (Capak et al. 2007, Cat. II/284).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 57 1498 The zCOSMOS 20k group catalog
table5.dat 63 19810 Spec-z and photo-z group galaxies
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See also:
VII/265 : COSMOS Morphological Catalog (V1.1) (Tasca+ 2009)
II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)
J/A+A/510/A56 : zCOSMOS type-2 AGN (Bongiorno, 2010)
J/ApJ/721/98 : Morphology of 70um COSMOS galaxies (Kartaltepe+, 2010)
J/ApJ/709/572 : COSMOS 70um sources (Kartaltepe+, 2010)
J/ApJ/697/1842 : zCOSMOS 10K sample group catalog to z=1 (Knobel+, 2009)
J/ApJS/184/218 : The zCOSMOS 10k-bright spectroscopic sample (Lilly+, 2009)
J/AJ/138/1261 : Spitzer/MIPS observations of the COSMOS field (Frayer+, 2009)
J/ApJS/172/70 : zCOSMOS-bright catalog (Lilly+, 2007)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- GrpID [0/1497]? Group running identification number
6- 7 I2 --- Nm [2/33] Number of spectroscopic members
9- 10 I2 --- Nc [2/97] Corrected richness (1)
12- 20 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000) (2)
22- 28 F7.5 deg DEdeg Declination in decimal degrees (J2000) (2)
30- 35 F6.4 --- [0.04/1.2] Mean redshift of spec-z group members
37- 41 F5.3 Mpc rad [0.1/1] Physical fudge radius (3)
43- 46 I4 km/s Disp [0/1147]?=-1 Velocity dispersion (4)
48- 52 F5.2 [Msun] logM [11.7/14.3] Log of DM halo fudge mass;
Sec. 4.2 (3)
54- 57 F4.2 --- GRP2 [0/1] Group purity parameter (5)
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Note (1): With respect to the flux limit (see Sec. 6.1).
Note (2): Improved group centers defined in Sec. 6.3.
Note (3): All values assume a Hubble constant of h=0.7.
Note (4): For groups with Nm≥5 (see Sec. 4.2).
Note (5): We define the group purity parameter, GRPi, i={1,2} of a group
to be the fraction of galaxies in that group that have GAPi=1 (see
Note (1) of table 5). See section 3.3 for further explanations.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- zCOSMOS [700014/960006] Galaxy identifier
8- 11 I4 --- GrpID [0/1497]? Group running identification number
13 I1 --- 20k [0/1] The 20k flag (1=spec-z available)
15- 16 I2 --- GAP2 [-1/1] Galaxy purity parameter (1)
18- 27 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
29- 35 F7.5 deg DEdeg Declination in decimal degrees (J2000)
37- 42 F6.4 --- z [0.008/1.3] Redshift (2)
44- 48 F5.2 [Msun] logM [0/12.1] Log of stellar mass (3)
50- 53 F4.2 --- PAs [0/1] Association probability (4)
55- 58 F4.2 --- PMa [0/1] Probability to be most massive (5)
60- 63 F4.2 --- PAd [0/1] Additional probability (6)
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Note (1): As in Knobel, 2009, Cat. J/ApJ/697/1842, we take the FOF
(Friends-of-Friends algorithm; (Huchra & Geller 1982, Cat. VII/86))
multi-run group catalog to be the main group catalog and use the
VDM (Voronoi-Delaunay method adapted by Gerke et al. 2005,
Cat. J/ApJ/625/6) multi-run catalog to define the galaxy purity
parameter, GAPi, for i={1,2} as follows: if an FOF group galaxy is
also in a VDM group such that there is a 1WM between the FOF and
the VDM group, the GAP1 of this galaxy is set to 1, and to 0
otherwise. Similarly, if there is a 2WM between these groups, then the
GAP2 is 1, and 0 otherwise. See section 3.3 for further explanations.
-1 = photo-z member.
Note (2): Spec-z if available ("1" in col. "20k"),
otherwise photo-z ("-1" in col. "GAP2", and "0" in col. "20k").
Note (3): Computed without considering mass return, see Sec. 2.2.
All values assume a Hubble constant of h=0.7.
Note (4): We attempt to quantify the probability that galaxies are associated
with a given group. See section 5.1.
Note (5): We introduce the probability pM of a galaxy to be the most massive
(in terms of stellar mass) of a given group. This is done by sorting
all the members - spectroscopic as well as photometric - in descending
order of mass such that Mi-1≥Mi for i=2, ..., Ntot, where
Ntot is the number of spectroscopic and photometric members. See
section 6.2 for further explanations.
Note (6): We introduce another probability pMA which is computed similarly
tp pM, but instead of ranking the group galaxies by their stellar mass
M* we rank them by M*/A with A being the area of the projected Voronoi
cell of the galaxy and thus includes directly information on the local
galaxy density. See section 6.4 for further explanations.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 17-Feb-2014