J/A+A/588/A14 Friends-of-friends galaxy group finder (Tempel+, 2016)
Friends-of-friends galaxy group finder with membership refinement.
Application to the local Universe.
Tempel E., Kipper R., Tamm A., Gramann M., Einasto M., Sepp T., Tuvikene T.
<Astron. Astrophys. 588, A14 (2016)>
=2016A&A...588A..14T 2016A&A...588A..14T (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Fundamental catalog
Keywords: catalogs - galaxies: groups: general -
large-scale structure of Universe - methods: data analysis
Abstract:
We improve the widely used friends-of-friends (FoF) group finding
algorithm with membership refinement procedures and apply the method
to a combined dataset of galaxies in the local Universe. A major aim
of the refinement is to detect subgroups within the FoF groups,
enabling a more reliable suppression of the fingers-of-God effect. The
FoF algorithm is often suspected of leaving subsystems of groups and
clusters undetected. We used a galaxy sample built of the 2MRS, CF2,
and 2M++ survey data comprising nearly 80000 galaxies within the
local volume of 430Mpc radius to detect FoF groups. We conducted a
multimodality check on the detected groups in search for subgroups. We
furthermore refined group membership using the group virial radius and
escape velocity to expose unbound galaxies. We used the virial theorem
to estimate group masses. The analysis results in a catalogue of 6282
galaxy groups in the 2MRS sample with two or more members, together
with their mass estimates. About half of the initial FoF groups with
ten or more members were split into smaller systems with the
multimodality check.
Description:
To delineate galaxy groups in the local Universe, we used galaxy data
from the extragalactic distance database (EDD2; Tully et al.,
2009AJ....138..323T 2009AJ....138..323T). The sample encompasses three datasets. As the
main source, we used the Two Micron All Sky Survey (Skrutskie et al.
2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233) Redshift Survey (2MRS) galaxies
brighter than 11.75 mag in the Ks band (for a description of the
catalogue, see Huchra et al., 2012, Cat. J/ApJS/199/26). We only used
galaxies that are securely off the Galactic plane: Galactic latitude
|b|>5°. Since the galaxy sample becomes extremely sparse farther
away, we only used galaxies with a cosmic microwave background (CMB)
corrected redshift z=0...0.1 (up to 430Mpc). This selection restricts
our 2MRS sample to 43480 galaxies.
For our analysis, we complemented the main 2MRS sample with two other
sources. From the CosmicFlows-2 survey that contains 8198 galaxies
with redshift-independent distance estimates (CF2; Tully et al., 2013,
Cat. J/AJ/146/86), we added 3627 (of these, 2799 galaxies do not have
a measured Ks magnitude). In addition, we made use of the 2M++
catalogue Lavaux & Hudson (2011, Cat. J/MNRAS/416/2840), which
combines elements from the 2MRS, the 6DF Galaxy Survey (Jones et al.
2009MNRAS.399..683J 2009MNRAS.399..683J, Cat. VII/259), and the Sloan Digital Sky Survey
(York et al., 2000AJ....120.1579Y 2000AJ....120.1579Y). Of the 64745 galaxies of the 2M++,
we added 31271 galaxies down to Ks<12.54, which extends the sample
well beyond the 2MRS magnitude limit.
Our final galaxy dataset includes 78378 galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 179 43480 Catalog of 2mrs galaxies
table2.dat 179 78378 Catalog of combined dataset galaxies
table3.dat 149 6282 Catalog of 2mrs groups
table4.dat 149 12106 Catalog of combined dataset groups
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
VII/256 : CfA2 Redshift Survey groups of galaxies (Mahtessian++, 2010)
VII/259 : 6dF galaxy survey final redshift release (Jones+, 2009)
J/A+A/381/420 : Group of Galaxies in the SSRS2 catalog (Adami+, 2002)
J/A+A/391/35 : Compact Groups in the UZC galaxy sample (Focardi+, 2002)
J/A+A/520/A42 : Galaxy groups in the VIMOS-VLT Deep Survey (Cucciati+, 2010)
J/MNRAS/416/2840 : The 2M++ galaxy redshift catalogue (Lavaux+, 2011)
J/A+A/540/A106 : SDSS-DR8 groups and clusters of galaxies (Tempel+, 2012)
J/ApJ/749/150 : Group galaxies in the RCS (Li+, 2012)
J/ApJ/751/50 : DEEP2 Redshift Survey Catalog of galaxy groups (Gerke+ 2012)
J/MNRAS/422/25 : SDSS DR7 groups, clusters and filaments (Smith+, 2012)
J/MNRAS/426/296 : Compact Groups of galaxies from 2MASX (Diaz-Gimenez+, 2012)
J/ApJS/199/26 : The 2MASS Redshift Survey (2MRS) (Huchra+, 2012)
J/AJ/146/86 : Cosmicflows-2 catalog (CF2) (Tully+, 2013)
J/MNRAS/443/2679 : GEEC2 spectroscopic survey of Galaxy groups (Balogh+, 2014)
J/A+A/565/A25 : Hickson compact groups Herschel obs. (Bitsakis+, 2014)
J/A+A/578/A61 : Galaxy groups in the 2M++ (Diaz-Gimenez+, 2015)
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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2- 8 I7 --- PGC Identification number in PGC
11- 15 I5 --- Group Group id given galaxy belongs to
18- 20 I3 --- Ngal Richness of the group galaxy belongs to
22- 29 F8.4 Mpc DistG Comoving distance to the group centre
31- 39 F9.6 --- zobs Observed redshift
42- 49 F8.6 --- zcmb Redshift, corrected to the CMB restframe
52- 59 F8.6 --- e_zobs Error of the observed redshift
61- 68 F8.4 Mpc Dist Comoving distance
70- 77 F8.4 Mpc Distc Comoving distance, finger-of-god corrected
79- 87 F9.5 deg RAdeg Right ascension of the galaxy (J2000)
89- 97 F9.5 deg DEdeg Declination of the galaxy (J2000)
99-107 F9.5 deg GLON Galactic longitude of the galaxy
109-117 F9.5 deg GLAT Galactic latitude of the galaxy
119-127 F9.5 deg SGLON Supergalactic longitude
129-137 F9.5 deg SGLAT Supergalactic latitude
139-147 F9.4 Mpc XSG Supergalactic cartesian coordinate
149-157 F9.4 Mpc YSG Supergalactic cartesian coordinate
159-167 F9.4 Mpc ZSG Supergalactic cartesian coordinate
170-176 F7.4 mag Ext Galactic extinction corrected Ks magnitude
179 I1 --- Source [1/3] Source of the galaxy (1)
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Note (1): Source of the galaxy as follows:
1 = 2MRS, Huchra et al., 2012, Cat. J/ApJS/199/26
2 = CF2, Tully et al., 2013, Cat. J/AJ/146/86
3 = 2M++, Diaz-Gimenez et al., 2015, Cat. J/A+A/578/A61
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Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
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3- 7 I5 --- Group Group id
10- 12 I3 --- Ngal Richness of the group
14- 22 F9.5 deg RAdeg Right ascension of the group centre (J2000)
24- 32 F9.5 deg DEdeg Declination of the group centre (J2000)
34- 42 F9.5 deg GLON Galactic longitude of the group centre
44- 52 F9.5 deg GLAT Galactic latitude of the group centre
54- 62 F9.5 deg SGLON Supergalactic longitude of the group centre
64- 72 F9.5 deg SGLAT Supergalactic latitude of the group centre
74- 82 F9.5 --- zcmb CMB-corrected redshift of the group
84- 91 F8.4 Mpc DistG Comoving distance to the group centre
93-101 F9.3 km/s sigmav rms deviation of the radial velocities
102-110 F9.4 Mpc sigmasky rms deviation of the sky-projected distances
112-119 F8.4 Mpc rmax Distance from group center to farthest member
121-131 F11.5 10+12Msun Mass200 Estimated mass of the NFW profile group
133-140 F8.4 kpc R200 Radius, where mean density is 200 the
Universe average density
143-149 F7.4 mag magG Observed magnitude of the group
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Acknowledgements:
Elmo Tempel, elmo.tempel(at)to.ee
(End) Patricia Vannier [CDS] 22-Jan-2016