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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 (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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 105 124 Catalog of overdensities in the Chandra Deep Field-South (CDFS)
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
Bytes Format Units Label Explanations
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)
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.
History: From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 08-Sep-2014
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