J/MNRAS/440/1248 SDSS DR7 voids and superclusters (Nadathur+, 2014)
A robust public catalogue of voids and superclusters in the SDSS Data Release 7
galaxy surveys.
Nadathur S., Hotchkiss S.
<Mon. Not. R. Astron. Soc., 440, 1248-1262 (2014)>
=2014MNRAS.440.1248N 2014MNRAS.440.1248N (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Clusters, galaxy
Keywords: catalogues - surveys - cosmology: observations -
large-scale structure of Universe
Abstract:
The study of the interesting cosmological properties of voids in the
Universe depends on the efficient and robust identification of such
voids in galaxy redshift surveys. Recently, Sutter et al. have
published a public catalogue of voids in the Sloan Digital Sky Survey
Data Release 7 main galaxy and luminous red galaxy samples, using the
void-finding algorithm ZOBOV, which is based on the watershed
transform. We examine the properties of this catalogue and show that
it suffers from several problems and inconsistencies, including the
identification of some extremely overdense regions as voids. As a
result, cosmological results obtained using this catalogue need to be
reconsidered. We provide instead an alternative, self-consistent,
public catalogue of voids in the same galaxy data, obtained from using
an improved version of the same watershed transform algorithm. We
provide a more robust method of dealing with survey boundaries and
masks, as well as with a radially varying selection function, which
means that our method can be applied to any other survey. We discuss
some basic properties of the voids thus discovered, and describe how
further information may be obtained from the catalogue. In addition,
we apply an inversion of the algorithm to the same data to obtain a
corresponding catalogue of large-scale overdense structures, or
`superclusters'. Our catalogues are available for public download on
the journal website.
Description:
This is a public catalogue of voids and superclusters identified in
the SDSS DR7 main galaxy and luminous red galaxy samples. This version
is dated 04.11.2013.
We make the catalogues available for general use. If you use them for
your own work, we ask that you cite the original paper, Nadathur &
Hotchkiss (2014MNRAS.440.1248N 2014MNRAS.440.1248N).
The top-level directory cat_v11.11.13 contains an example python
script called postproc.py, and two folders called comovcoords and
redshiftcoords containing two versions of the catalogue in different
coordinate systems. The comoving coordinate system is pretty
self-explanatory, for a description of the other one please refer to
the paper.
Each of these directories is further divided into six folders
containing the Type1 and Type2 void catalogues and the supercluster
catalogue for each of the galaxy samples analysed here, and a folder
called tools, which contains data useful for users wishing to apply
their own selection criteria. The basic information provided includes
the location of the barycentre of each structure, its volume,
effective radius, average density and minimum or maximum density, its
core galaxy and seed zone, the total number of galaxies in the seed
zone, the number of zones merged to form the structure, the total
number of particles in the structure, and its density ratio. These are
split between two files for each structure type and each sample, named
xxx_info.txt and xxx_list.txt, where xxx refers to the structure type.
It is also possible to extract lists of member galaxies of each
structure and their magnitudes. An example python script, postproc.py,
demonstrates how to access this information and how to build
alternative catalogues using user-defined selection criteria.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
samples.dat 115 6 Details of the galaxy samples (table 1), numbers of
structures identified (table 2) and survey volumes
and void volume fraction (table 3)
bri1bt.dat 100 712 BasicType voids from bright1 in comoving coordinates
bri1t1c.dat 100 896 Type1 clusters from bright1 in comoving coordinates
bri1t1v.dat 100 262 Type1 voids from bright1 in comoving coordinates
bri1t2v.dat 100 163 Type2 voids from bright1 in comoving coordinates
bri2bt.dat 100 398 BasicType voids from bright2 in comoving coordinates
bri2t1c.dat 100 325 Type1 clusters from bright2 in comoving coordinates
bri2t1v.dat 100 112 Type1 voids from bright2 in comoving coordinates
bri2t2v.dat 100 70 Type2 voids from bright2 in comoving coordinates
dim1bt.dat 100 262 BasicType voids from dim1 in comoving coordinates
dim1t1c.dat 100 419 Type1 clusters from dim1 in comoving coordinates
dim1t1v.dat 100 80 Type1 voids from dim1 in comoving coordinates
dim1t2v.dat 100 53 Type2 voids from dim1 in comoving coordinates
dim2bt.dat 100 676 BasicType voids from dim2 in comoving coordinates
dim2t1c.dat 100 1192 Type1 clusters from dim2 in comoving coordinates
dim2t1v.dat 100 271 Type1 voids from dim2 in comoving coordinates
dim2t2v.dat 100 199 Type2 voids from dim2 in comoving coordinates
lrgbribt.dat 100 193 BasicType voids from lrgbright in comoving coordinates
lrgbt1c.dat 100 39 Type1 clusters from lrgbright in comoving coordinates
lrgbt1v.dat 100 13 Type1 voids from lrgbright in comoving coordinates
lrgbt2v.dat 100 1 Type2 voids from lrgbright in comoving coordinates
lrgdimbt.dat 100 349 BasicType voids from lrgdim in comoving coordinates
lrgdt1c.dat 100 196 Type1 clusters from lrgdim in comoving coordinates
lrgdt1v.dat 100 70 Type1 voids from lrgdim in comoving coordinates
lrgdt2v.dat 100 19 Type2 voids from lrgdim in comoving coordinates
info.txt 121 201 All information the use of the data in cat_files
subdirectory (Version 11/11/2013)
cat_files/* . 4 All files
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Byte-by-byte Description of file: samples.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Sample Sample name
11- 21 A11 --- Type Galaxy type
23 A1 --- --- [M]
24 A1 --- Band [rg] band for magnitude limit
25 A1 --- l_MAGlim Limit flag on MAGlim
26- 31 F6.2 mag MAGlim Absolute magnitude limit
34- 37 F4.2 --- b_z Lower value of redshift extent
38- 40 A3 --- --- [<z<]
41- 44 F4.2 --- B_z Upper value of redshift extent
46- 51 I6 --- Ngal Number of galaxies in the sample
53- 58 E6.2 Mpc-1 n Mean number density (Mpc/h)-3)
60- 62 I3 --- NB Number of Basic type structures identified in
the sample
64- 66 I3 --- NBz Number of Basic type structures identified in
the sample found in the redshift coordinates
of equation (2) of the paper
68- 70 I3 --- NT1 Number of Type1 type voids identified in the
sample
72- 74 I3 --- NT1z Number of Type1 type svoids identified in the
sample found in the redshift coordinates of
equation (2) of the paper
76- 78 I3 --- NT2 Number of Type2 type voids identified in the
sample
80- 82 I3 --- NT2z Number of Type2 type voids identified in the
sample found in the redshift coordinates of
equation (2) of the paper
84- 87 I4 --- NSC Number of Superclusters identified in the sample
89- 92 I4 --- NSCz Number of Superclusters identified in the sample
found in the redshift coordinates of
equation (2) of the paper
94- 99 F6.1 10+6Mpc3 SamVol Sample volume (106Mpc3/h3)
101-104 F4.2 --- FB Basic type void volume fraction
106-109 F4.2 --- FT1 Type1 void volume fraction
111-115 F5.3 --- FT2 Type2 void volume fraction
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Byte-by-byte Description of file: bri* dim* lrg*
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Bytes Format Units Label Explanations
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1- 6 I6 --- Zone Zone number
8- 17 F10.6 deg RAdeg Right ascension (J2000)
19- 28 F10.6 deg DEdeg Declination (J2000)
30- 37 F8.6 --- z Redshift
39- 48 F10.6 Mpc Reff Effective radius (Mpc/h)
50- 58 F9.6 deg thetaeff Effective angular separation
60- 69 F10.6 --- AvgDens Void average density
71- 85 F15.8 --- MDens Void minimal density for voids and
maximal density for Type 1 clusters
87 I1 --- Flag [0/1] Edge Flag
89-100 F12.6 --- VDR Void density ratio
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 04-Feb-2016