J/ApJ/697/1842 zCOSMOS 10K sample group catalog to z=1 (Knobel+, 2009)
An optical group catalog to z = 1 from the zCOSMOS 10 K sample.
Knobel C., Lilly S.J., Iovino A., Porciani C., Kovac K., Cucciati O.,
Finoguenov A., Kitzbichler M.G., 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., Coppa G.,
de la Torre S., de Ravel L., Franzetti P., Garilli B., Kampczyk P.,
Lamareille F., Le Borgne J.-F., Le Brun V., Maier C., Mignoli M., Pello R.,
Peng Y., Montero E.P., Ricciardelli E., Silverman J.D., Tanaka M.,
Tasca L., Tresse L., Vergani D., Zucca E., Abbas U., Bottini D., Cappi A.,
Cassata P., Cimatti A., Fumana M., Guzzo L., Koekemoer A.M., Leauthaud A.,
Maccagni D., Marinoni C., McCracken H.J., Memeo P., Meneux B., Oesch P.,
Pozzetti L., Scaramella R.
<Astrophys. J., 697, 1842-1860 (2009)>
=2009ApJ...697.1842K 2009ApJ...697.1842K
ADC_Keywords: Galaxy catalogs ; Redshifts
Keywords: catalogs - galaxies: clusters: general - galaxies: high-redshift -
methods: data analysis
Abstract:
We present a galaxy group catalog spanning the redshift range
0.1≲z≲1 in the ∼1.7deg2 COSMOS field, based on the first ∼10000
zCOSMOS spectra. The performance of both the Friends-of-Friends (FOF)
and Voronoi-Delaunay method (VDM) approaches to group identification
has been extensively explored and compared using realistic mock
catalogs. We find that the performance improves substantially if
groups are found by progressively optimizing the group-finding
parameters for successively smaller groups, and that the highest
fidelity catalog, in terms of completeness and purity, is obtained by
combining the independently created FOF and VDM catalogs. The final
completeness and purity of this catalog, both in terms of the groups
and of individual members, compares favorably with recent results in
the literature. The current group catalog contains 102 groups with
N≥5 spectroscopically confirmed members, with a further ∼700 groups
with 2≤N≤4. Most of the groups can be assigned a velocity dispersion
and a dark-matter mass derived from the mock catalogs, with
quantifiable uncertainties. The fraction of zCOSMOS galaxies in groups
is about 25% at low redshift and decreases toward ∼15% at z∼0.8. The
zCOSMOS group catalog is broadly consistent with that expected from
the semianalytic evolution model underlying the mock catalogs.
Description:
zCOSMOS is a spectroscopic redshift survey (Lilly et al. 2007, cat.
J/ApJS/172/70; S. J. Lilly et al. 2009, Cat. J/ApJS/184/218) covering
the ∼1.7 deg2 COSMOS field (Scoville et al. 2007ApJS..172....1S 2007ApJS..172....1S). The
redshifts are measured with the VLT using the VIMOS spectrograph. The
mocks we use to calibrate and test our groupfinders are adapted from
the COSMOS mock light cones (Kitzbichler & White 2007MNRAS.376....2K 2007MNRAS.376....2K).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 48 800 Group catalog
table4.dat 38 2310 Group galaxies
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See also:
VII/256 : Groups of Galaxies from CfA2 Redshift Survey (Mahtessian++, 2010)
VII/86 : Groups of Galaxies. I. Nearby Groups (Huchra+ 1982)
J/A+A/520/A42 : Galaxy groups in the VIMOS-VLT Deep Survey (Cucciati+, 2010)
J/ApJS/184/218 : The zCOSMOS 10k-bright spectroscopic sample (Lilly+, 2009)
J/ApJS/172/70 : zCOSMOS-bright catalog (Lilly+, 2007)
J/ApJ/625/6 : Galaxy groups in the DEEP2 Galaxy Redshift Survey (Gerke+,
2005)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- GrpID Running identification number
5- 6 I2 --- N Group richness
8- 15 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 22 F6.4 deg DEdeg Declination in decimal degrees (J2000)
24- 29 F6.4 --- z Group redshift
31- 34 I4 km/s sigma Final velocity dispersion estimate σ
36- 43 E8.2 Msun Mfudge The "fudge" mass (1)
45- 48 F4.2 --- GRP1 [0,1] First Group purity parameter (2)
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Note (1): The mass for a group with observed richness N and redshift z is
simply given by: Mfudge=<Mhalo(N~,z)> where
Mhalo(N~,z) denotes the mass of a halo at redshift z
containing N∼ galaxies, N∼ is the observed richness of the
group corrected for sampling and redshift success rate, and the angle
brackets denote the average over the halos in the 24 mocks. We will
denote this mass as "fudge mass" to indicate that it is calibrated
with the mocks. See section 4.4 for further details.
Note (2): The group purity parameter (GRPi) for i=1,2 is defined by the
fraction of FOF members having a galaxy purity parameter GAP≥i (see
Note (1) of table 4). For i=1 this is the fraction of FOF members that
are also 1WM ("one-way-matched") members, and for i=2 that are also
2WM ("two-way-matched") members. See section 4.1 for further details.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- zCOSMOS Galaxy identification
8- 10 I3 --- GrpID Group identification; see Table 3
12- 13 I2 --- N Group richness
15- 22 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
24- 29 F6.4 deg DEdeg Declination in decimal degrees (J2000)
31- 36 F6.4 --- z zCOSMOS 10k-bright spectroscopic redshift
(Lilly et al. 2009, Cat. J/ApJS/184/218)
38 I1 --- GAP [0,2] Galaxy purity parameter (1)
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Note (1): GAP is a flag indicating if a certain group galaxy is contained
simultaneously in catalogs from FOF (Friends-of-Friends algorithm;
(Huchra & Geller 1982, Cat. VII/86)) and from VDM (Voronoi-Delaunay
method adapted by Gerke et al. (2005, Cat. J/ApJ/625/6). For a certain
FOF group galaxy GAP is defined as follows:
0 = If there is no VDM group containing this galaxy.
1 = If it is also contained in a VDM group, and the FOF group has a one-way
match to this VDM group or this VDM group exhibits a one-way match to the
FOF group.
2 = If it is contained in a VDM group, and the FOF group has a two-way match
to this VDM group.
See section 3.3.2 for further details.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Jun-2011