J/AJ/147/52 Structures in the Chandra Deep Field-South (Dehghan+, 2014)
Clusters, groups, and filaments in the Chandra Deep Field-South up to
redshift 1.
Dehghan S., Johnston-Hollitt M.
<Astron. J., 147, 52 (2014)>
=2014AJ....147...52D 2014AJ....147...52D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Redshifts ; Velocity dispersion
Keywords: galaxies: clusters: general - galaxies: distances and redshifts -
galaxies: groups: general
Abstract:
We present a comprehensive structure detection analysis of the
0.3deg2 area of the MUSYC-ACES field, which covers the Chandra Deep
Field-South (CDFS). Using a density-based clustering algorithm on the
MUSYC and ACES photometric and spectroscopic catalogs, we find 62
overdense regions up to redshifts of 1, including clusters, groups,
and filaments. We also present the detection of a relatively small
void of ∼10Mpc2 at z∼0.53. All structures are confirmed using the
DBSCAN method, including the detection of nine structures previously
reported in the literature. We present a catalog of all structures
present, including their central position, mean redshift, velocity
dispersions, and classification based on their morphological and
spectroscopic distributions. In particular, we find 13 galaxy clusters
and 6 large groups/small clusters. Comparison of these massive
structures with published XMM-Newton imaging (where available) shows
that 80% of these structures are associated with diffuse, soft-band
(0.4-1keV) X-ray emission, including 90% of all objects classified as
clusters. The presence of soft-band X-ray emission in these massive
structures (M200≥4.9x1013M☉) provides a strong
independent confirmation of our methodology and classification scheme.
In the closest two clusters identified (z<0.13) high-quality optical
ur photometric sample contains 5522 galaxies
imaging from the Deep2c field of the Garching-Bonn Deep Survey reveals
the cD galaxies and demonstrates that they sit at the center of the
detected X-ray emission. Nearly 60% of the clusters, groups, and
filaments are detected in the known enhanced density regions of the
CDFS at z≃0.13, 0.52, 0.68, and 0.73. Additionally, all of the
clusters, bar the most distant, are found in these overdense redshift
regions. Many of the clusters and groups exhibit signs of ongoing
formation seen in their velocity distributions, position within the
detected cosmic web, and in one case through the presence of tidally
disrupted central galaxies exhibiting trails of stars. These results
all provide strong support for hierarchical structure formation up to
redshifts of 1.
Description:
We constructed a spectroscopic and a photometric sample, in order to
identify and verify the high-density regions in the extended Chandra
Deep Field-South (ECDFS).
The ACES catalog contains 7277 unique heliocentric redshifts, of which
5080 have secure redshifts within the ECDFS region. The spectroscopic
sample used herein is made of 4692 objects with z<0.1, R<24, extracted
from the preliminary ACES data set.
The photometric sample was extracted from the MUSYC catalog, which
provides photometric redshifts for ∼80000 galaxies in the ECDFS down
to R∼27. Our photometric sample contains 5522 galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 105 124 Catalog of overdensities in the Chandra Deep
Field-South (CDFS)
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See also:
II/253 : Chandra Deep Field South: multi-colour data (Wolf+, 2008)
VII/177 : Redshifts and Velocity Dispersions for Abell Clusters (Struble+ 1991)
J/A+A/555/A42 : The XMM-CDFS catalogues (Ranalli+, 2013)
J/MNRAS/425/2116 : Arizona CDFS Environment Survey, ACES (Cooper+, 2012)
J/ApJS/189/270 : MUSYC optical imaging in ECDF-S (Cardamone+, 2010)
J/ApJS/139/369 : Chandra Deep Field South. 1 Ms catalog (Giacconi+, 2002)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Running sequence number of the structure
4 A1 --- f_Seq Flag about the structure (1)
6 A1 --- Type Type of eclipse (p=primary, s=secondary)
8- 9 I2 h RAh ? Hour of Right Ascension (J2000) (2)
11- 12 I2 min RAm ? Minute of Right Ascension (J2000) (2)
14- 17 F4.1 s RAs ? Second of Right Ascension (J2000) (2)
19 A1 --- DE- Sign of the Declination (J2000) (2)
20- 21 I2 deg DEd ? Degree of Declination (J2000) (2)
23- 24 I2 arcmin DEm ? Arcminute of Declination (J2000) (2)
26- 27 I2 arcsec DEs [0/60]? Arcsecond of Declination (J2000) (2)
29- 30 I2 --- Ng ? Number of galaxies
32- 37 F6.4 --- z1 ? Redshift
39- 44 F6.4 --- z2 ? Second redshift value (if any)
46- 51 F6.4 --- e_z1 ? Uncertainty in z1 (3)
53- 58 F6.4 --- e_z2 ? Uncertainty in z2 (3)
60 A1 --- f_sig1 [f] Unreliable velocity dispersion (4)
62- 65 I4 km/s sig1 ? Spectroscopic velocity dispersion σv
67- 69 I3 km/s E_sig1 ? Upper uncertainty in sig1 (3)
71- 73 I3 km/s e_sig1 ? Lower uncertainty in sig1 (3)
75- 77 I3 km/s sig2 ? Second spectroscopic velocity dispersion value
(if any)
79- 81 I3 km/s E_sig2 ? Upper uncertainty in sig2 (3)
83- 84 I2 km/s e_sig2 ? Lower uncertainty in sig2 (3)
86- 89 F4.2 Mpc Eps ? Value of the distance factor Eps (5)
91- 95 F5.3 --- zbin0 ? Lower value of the specified redshift bin range
97-101 F5.3 --- zbin1 ? Upper value of the specified redshift bin range
103-105 A3 --- Cl Designated class (1-5) (6)
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Note (1): Flag as follows:
d = Structure is detected along with a significant (N≥3) spectroscopic
substructure. The first and second redshift and velocity dispersion values
correspond to the structure and its sub-structure, respectively.
e = We do not present velocity dispersion and classification, since the
structure is not spectroscopically detected.
Note (2): Coordinates of the midpoint.
Note (3): This is merely a statistical error due to the sampling error and
deviance from the normal distribution. Note that the intrinsic photometric
errors and possible contaminations from other populations are not included.
Note (4): Velocity dispersion is unreliable, since the structure is located on
the edge of the spectroscopic frame.
Note (5): The clustering algorithm DBSCAN utilizes two user-defined factors, a
distance factor (Eps) and a minimum number of points (MinPts), in order to
classify all the data points as either core, border, or noise points with
respect to a detected structure (see additional details in Section 3.2).
Note (6): We define five classes among the detected overdensities as follows:
1 = Radial filaments or fake structures: class 1 objects have very broad
velocity distribution (vd≫400km/s) without any significant peak in their
velocity distribution. Occasionally, class 1 objects consist of a number of
very small groups lined up in the redshift distribution.
2 = Filaments on the plane of sky: class 2 objects have filamentary
morphologies in the plane of sky often with low velocity dispersions.
3 = Groups: structures of nearly Gaussian redshift distribution with
vd<400km/s are classified as groups.
4 = Massive groups or small clusters: class 4 objects consist of structures
with vd≳400km/s, though with insufficient spectroscopic sampling rate to
be considered as clusters (Ns<Nc(z)).
5 = Clusters: structures conforming to vd≳400km/s and Ns≥Nc(z) are
classified as clusters.
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 08-Sep-2014