J/MNRAS/422/25 SDSS DR7 groups, clusters and filaments (Smith+, 2012)
Multiscale probability mapping: groups, clusters and an algorithmic search for
filaments in SDSS.
Smith A.G., Hopkins A.M., Hunstead R.W., Pimbblet K.A.
<Mon. Not. R. Astron. Soc., 422, 25-43 (2012)>
=2012MNRAS.422...25S 2012MNRAS.422...25S
ADC_Keywords: Surveys ; Clusters, galaxy ; Morphology ; Redshifts
Keywords: methods: statistical - catalogues - surveys -
galaxies: clusters: general - galaxies: groups: general -
large-scale structure of Universe
Abstract:
We have developed a multiscale structure identification algorithm for
the detection of overdensities in galaxy data that identifies
structures having radii within a user-defined range. Our "multiscale
probability mapping" technique combines density estimation with a
shape statistic to identify local peaks in the density field. This
technique takes advantage of a user-defined range of scale sizes,
which are used in constructing a coarse-grained map of the underlying
fine-grained galaxy distribution, from which overdense structures are
then identified. In this study we have compiled a catalogue of groups
and clusters at 0.025<z<0.24 based on the Sloan Digital Sky Survey
(SDSS), Data Release 7, quantifying their significance and comparing
with other catalogues. Most measured velocity dispersions for these
structures lie between 50 and 400km/s. A clear trend of increasing
velocity dispersion with radius from 0.2 to 1Mpc/h is detected,
confirming the lack of a sharp division between groups and clusters. A
method for quantifying elongation is also developed to measure the
elongation of group and cluster environments. By using our group and
cluster catalogue as a coarse-grained representation of the galaxy
distribution for structure sizes of ≲1Mpc/h, we identify 53
filaments (from an algorithmically derived set of 100 candidates) as
elongated unions of groups and clusters at 0.025<z<0.13. These
filaments have morphologies that are consistent with previous samples
studied.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 70 10443 *Catalogue of MSPM groups and clusters in SDSS DR7
table5.dat 42 53 *Catalogue of MSPM filaments in SDSS DR7
void.dat 30 47 *Catalogue of MSPM voids in SDSS DR7
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Note on table1.dat and table5.dat: Entries are ordered by P-S within slices of
ascending redshift, where each slice has a width 0.025 in z.
Note on void.dat: Data to accompany "something, not sure yet" the paper, and
perhaps others. Locations of 40Mpc/h diameter MSPM voids.
Entries are ordered by redshift.
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See also:
II/294 : SDSS Photometric Catalog, DR7 (Adelman-McCarthy+, 2009)
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
J/A+A/514/A102 : SDSS DR7 groups of galaxies (Tago+, 2010)
J/MNRAS/418/1409 : Compact groups of galaxies in SDSS DR7 (Mendel+, 2011)
J/A+A/539/A80 : SDSS DR7 superclusters. The catalogues (Liivamagi+, 2012)
http://www.sdss.org : SDSS Home Page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [1/10443] Identification number of MSPM group
or cluster (MultiScale Probability Mapping)
7- 14 F8.4 deg RAdeg Right Ascension (J2000) (deg)
16- 23 F8.4 deg DEdeg Declination (J2000) (deg)
25- 31 F7.5 --- z [0.025/0.24] Redshift
33- 37 F5.3 --- P [0.5/1] Overdensity probability at peak P-S (1)
39- 41 I3 --- N [4/157] Count of galaxies with r<17.77
43- 47 F5.3 Mpc R Radius in Mpc/h enclosing region with P-S>0.5 (1)
49- 53 F5.1 --- LDCa ? Local density contrast (LDC) with radii
[0.4,2]Mpc/h
54 A1 --- n_LDCa [i] 'i' for infinity
55- 58 F4.1 --- LDCb ? Local density contrast (LDC) with radii
[1,2]Mpc/h
59 A1 --- n_LDCb [i] 'i' for infinity
60- 63 I4 km/s sigma Velocity dispersion σ
65- 70 F6.1 --- Dens ?=-1 Galaxy density within 0.4Mpc/h in units
of the background density
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Note (1):
* P is the overdensity probability, and P>0.5 designates a location
denser than average
* S is the shape statistic, and S<0.5 designates a location denser than
surrounding locations
* P-S>0.5 designates therefore locations denser than average and denser than
surrounding locations, guaranteeing P > 0.5 and S < 0.5
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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- 5 I5 --- ID [1/10443] Identification number
(from central group or cluster)
7- 14 F8.4 deg RAdeg Right Ascension (J2000) (deg)
16- 22 F7.4 deg DEdeg Declination (J2000) (deg)
24- 30 F7.5 --- z Redshift
32- 36 F5.3 --- Pe Highest elongation probability within 10Mpc/h
38- 39 I2 --- N [3/15] Count of groups and clusters within a
10Mpc/h radius on the sky and 10Mpc/h in the
line of sight (cylindrical aperture)
41- 42 A2 --- Mph [I II V] Morphology of the filament (1)
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Note (1): the morphology class is based on the appearance in two
orthogonal planes: the sky, and a plane perpendicular to the
sky and aligned with the the filament:
I = Type I (straight). Both are straight
II = Type II (warped). At least one is curved, with neither being
uniform or irregular
V = Type IV (uniform). Both are uniform
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Byte-by-byte Description of file: void.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number (from a lattice of
sampling positions formed by spectroscopic
plate centres and a uniform redshift interval)
7- 14 F8.4 deg RAdeg Centre Right Ascension (J2000)
16- 22 F7.4 deg DEdeg Centre Declination (J2000)
24- 30 F7.5 --- z Centre Redshift
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History:
* 27-Nov-2012: Copied at http://www.physics.usyd.edu.au/~asmith/MSPM/
* 14-Jan-2013: In table1, first 331 lines omitted added
(End) Patricia Vannier [CDS] 27-Nov-2012