J/A+A/618/A81 Bayesian group finder applied to the 2MRS data (Tempel+, 2018)
Bayesian group finder based on marked point processes.
Method and feasibility study using the 2MRS data set.
Tempel E., Kruuse M., Kipper R., Tuvikene T., Sorce J.G., Stoica R.S.
<Astron. Astrophys. 618, A81 (2018)>
=2018A&A...618A..81T 2018A&A...618A..81T (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxy catalogs
Keywords: methods: data analysis - methods: statistical -
galaxies: groups: general - galaxies: clusters: general - catalogs -
large-scale structure of Universe
Abstract:
We propose a probabilistic galaxy group detection algorithm based on
marked point processes with interactions. The pattern of galaxy groups
in a catalogue is seen as a random set of interacting objects. The
positions and the interactions of these objects are governed by a
probability density. The parameters of the probability density are
chosen using a priori knowledge. The estimator of the unknown cluster
pattern is given by the configuration of objects maximising the
proposed probability density. Adopting the Bayesian framework, the
proposed probability density is maximised using a simulated annealing
(SA) algorithm. At fixed temperature, the SA algorithm is a Monte
Carlo sampler of the probability density. Hence, the method provides
"for free" additional information such as the probabilities that a
point or two points in the observation domain belong to the cluster
pattern, respectively. These supplementary tools allow the
construction of tests and techniques to validate and to refine the
detection result. To test the feasibility of the proposed methodology,
we applied it to the well-studied 2MASS Redshift Survey (2MRS) data
set. Compared to previously published Friends-of-Friends (FoF) group
finders, the proposed Bayesian group finder gives overall similar
results. However, for specific applications, like the reconstruction
of the local Universe, the details of the grouping algorithms are
important.
Description:
The catalogue of galaxy groups and clusters consists of two tables.
The first table lists galaxies that were used to generate the group
catalogue, the second describes the group properties. Galaxy data are
based on the 2MRS (Huchra et al., 2012, Cat. J/ApJS/199/26),
downloaded from the extragalactic distance database (EDD2; Tully et
al., 2009AJ....138..323T 2009AJ....138..323T). This data set includes galaxies brighter
than 11.75mag in the Ks band. For group extraction, the galaxy sample
was restricted to galaxies closer than 300Mpc. Due to the
probabilistic nature of the group finder algorithm, probabilities that
a galaxy belongs to a specific group or whether the galaxy is a field
galaxy were derived. The individual probabilities are presented in the
galaxy catalogue.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
2mrs_gal.dat 236 43526 Catalogue of galaxies
2mrs_gr.dat 156 7755 Catalogue of galaxy groups
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See also:
J/A+A/588/A14 : Friends-of-friends galaxy group finder (Tempel+, 2016)
Byte-by-byte Description of file: 2mrs_gal.dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- PGCID Identification number in PGC
9- 12 I4 --- GroupID ?=0 Primary group ID the galaxy belongs to (1)
14- 16 I3 --- Ngal Richness of the primary group the galaxy
belongs to
18- 25 F8.4 Mpc DistG Comoving distance to the primary group centre
27- 35 F9.6 --- zobs Observed redshift
37- 45 F9.6 --- zcmb Redshift, corrected to the CMB rest frame
47- 54 F8.6 --- e_zobs Error of the observed redshift
56- 63 F8.4 Mpc Dist Comoving distance
65- 73 F9.5 deg RAdeg Right ascension of the galaxy (J2000)
75- 83 F9.5 deg DEdeg Declination of the galaxy (J2000)
85- 93 F9.5 deg GLON Galactic longitude of the galaxy
95-103 F9.5 deg GLAT Galactic latitude of the galaxy
105-113 F9.5 deg SGLON Supergalactic longitude of the galaxy
115-123 F9.5 deg SGLAT Supergalactic latitude of the galaxy
125-133 F9.4 Mpc XSG Supergalactic cartesian x coordinate
135-143 F9.4 Mpc YSG Supergalactic cartesian y coordinate
145-153 F9.4 Mpc ZSG Supergalactic cartesian z coordinate
155-160 F6.3 mag Ksmag Galactic-extinction-corrected Ks magnitude
from the source catalogue
162-165 I4 --- GID.FoF Group ID in the FoF group catalogue (2)
167-168 I2 --- Ngal.FoF Group richness in the FoF group catalogue (2)
170 I1 --- Ngr [0-5] Number of groups the galaxy is
associated with
172-175 I4 --- GID1 ?=0 The 1st associated group ID (1)
177-180 I4 --- GID2 ?=0 The 2nd associated group ID
182-185 I4 --- GID3 ?=0 The 3rd associated group ID
187-190 I4 --- GID4 ?=0 The 4th associated group ID
192-194 I3 --- GID5 ?=0 The 5th associated group ID
196-201 F6.4 --- pfield Probability that the galaxy is a field galaxy
203-208 F6.4 --- p1 Probability that the galaxy belongs to group 1
210-215 F6.4 --- p2 Probability that the galaxy belongs to group 2
217-222 F6.4 --- p3 Probability that the galaxy belongs to group 3
224-229 F6.4 --- p4 Probability that the galaxy belongs to group 4
231-236 F6.4 --- p5 Probability that the galaxy belongs to group 5
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Note (1): Group ID may be different in the GroupID and GID1 columns due to the
group membership refinement procedure.
Note (2): Tempel et al., 2016, Cat. J/A+A/588/A14
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Byte-by-byte Description of file: 2mrs_gr.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- GroupID Group or cluster ID
6- 8 I3 --- Ngal Richness of the group
10- 18 F9.5 deg RAdeg Right ascension of the group centre (J2000)
20- 28 F9.5 deg DEdeg Declination of the group centre (J2000)
30- 38 F9.5 deg GLON Galactic longitude of the group centre
40- 48 F9.5 deg GLAT Galactic latitude of the group centre
50- 58 F9.5 deg SGLON Supergalactic longitude of the group centre
60- 68 F9.5 deg SGLAT Supergalactic latitude of the group centre
70- 76 F7.5 --- zcmb CMB-corrected redshift of the group
78- 85 F8.4 Mpc DistG Comoving distance to the group centre
87- 94 F8.3 km/s sigmav RMS deviation of the radial velocities
96-101 F6.4 Mpc sigmasky RMS deviation of the sky-projected distances
103-108 F6.4 Mpc Rmax Distance from group centre to the farthest
member
110-119 F10.5 10+12Msun M200 Estimated mass of the group assuming the
NFW density profile
121-126 F6.4 Mpc R200 Radius where the group mean density is
200 times the Universe average density
128-136 F9.4 Mpc XSG Supergalactic cartesian x coordinate
138-146 F9.4 Mpc YSG Supergalactic cartesian y coordinate
148-156 F9.4 Mpc ZSG Supergalactic cartesian z coordinate
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Acknowledgements:
Taavi Tuvikene, taavi.tuvikene(at)to.ee
(End) Patricia Vannier [CDS] 26-Jul-2018