J/ApJ/765/117 X-ray group of galaxies in AEGIS (Erfanianfar+, 2013) ================================================================================ X-ray groups of galaxies in the AEGIS deep and wide fields. Erfanianfar G., Finoguenov A., Tanaka M., Lerchster M., Nandra K., Laird E., Connelly J.L., Bielby R., Mirkazemi M., Faber S.M., Kocevski D., Cooper M., Newman J.A., Jeltema T., Coil A.L., Brimioulle F., Davis M., McCracken H.J., Willmer C., Gerke B., Cappelluti N., Gwyn S. =2013ApJ...765..117E ================================================================================ ADC_Keywords: Galaxy catalogs ; X-ray sources ; Redshifts ; Surveys Keywords: catalogs; cosmology: observations; dark matter; large-scale structure of universe; surveys Abstract: We present the results of a search for extended X-ray sources and their corresponding galaxy groups from 800ks Chandra coverage of the All-wavelength Extended Groth Strip International Survey (AEGIS). This yields one of the largest X-ray-selected galaxy group catalogs from a blind survey to date. The red-sequence technique and spectroscopic redshifts allow us to identify 100% of reliable sources, leading to a catalog of 52 galaxy groups. These groups span the redshift range z~0.066-1.544 and virial mass range M_200_~1.3-13.3x10^13^^M_{sun}_. For the 49 extended sources that lie within DEEP2 and DEEP3 Galaxy Redshift Survey coverage, we identify spectroscopic counterparts and determine velocity dispersions. We select member galaxies by applying different cuts along the line of sight or in projected spatial coordinates. A constant cut along the line of sight can cause a large scatter in scaling relations in low-mass or high-mass systems depending on the size of the cut. A velocity-dispersion-based virial radius can cause a larger overestimation of velocity dispersion in comparison to an X-ray-based virial radius for low-mass systems. There is no significant difference between these two radial cuts for more massive systems. Independent of radial cut, an overestimation of velocity dispersion can be created in the case of the existence of significant substructure and compactness in X-ray emission, which mostly occur in low-mass systems. We also present a comparison between X-ray galaxy groups and optical galaxy groups detected using the Voronoi-Delaunay method for DEEP2 data in this field. Description: Our very deep Chandra survey used the Advanced CCD Imaging Spectrometer (ACIS-I) in three contiguous fields covering a total area of 0.25deg^2^ (K. Nandra et al., in preparation) and a series of eight pointings covering a total area of approximately 0.67deg^2^ in EGS. Laird et al. (2009, J/ApJS/180/102) provided the details for the latter survey and the X-ray point source catalog. We also used the XMM-Newton observations of the field (ObsIDs 0127921001, 0127921101, 0127921201, and 0503960101). The EGS field is located at the center of the third wide field of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS-Wide3, W3), which is covered in u*, g', r', i', and z' filters down to i'=24.5. In this work, we have used the T0006 release of the CFHTLS Deep data. The DEEP2 Redshift Survey has targeted ~3.5deg^2^ within four fields on the sky using the DEIMOS multi-object spectrograph on the Keck II Telescope. All the DEEP2 targets have 18.5<=R<=24.1. The EGS is one of these four fields. See section 2.3. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 97 52 AEGIS X-ray galaxy groups table2.dat 54 387 Group member galaxies -------------------------------------------------------------------------------- See also: B/chandra : The Chandra Archive Log (CXC, 1999-2014) B/cfht : Log of CFHT Exposures (CADC, 1979-) III/268 : DEEP2 Redshift Survey, Data Release 4 (Matthews+ 2013) II/317 : The CFHTLS Survey (T0007 release) (Hudelot+ 2012) VII/84 : Groups of Galaxies. III. The CfA Survey (Geller+ 1983) J/ApJ/756/139 : Spectrosc. redshifts of galaxies in groups (Connelly+, 2012) J/ApJ/753/121 : zCOSMOS 20k sample group catalog to z<~1.2 (Knobel+, 2012) J/ApJ/751/50 : Galaxy groups cat. from DEEP2 Redshift Survey (Gerke+ 2012) J/MNRAS/426/296 : Compact Groups of galaxies from 2MASX (Diaz-Gimenez+, 2012) J/ApJS/193/14 : DEEP3 Galaxy Redshift Survey: GOODS-N field (Cooper+, 2011) J/MNRAS/403/2063 : SXDF X-ray groups and galaxy clusters (Finoguenov+, 2010) J/ApJS/180/102 : AEGIS-X: Chandra deep survey (Laird+, 2009) J/ApJ/697/1842 : zCOSMOS 10K sample group catalog to z=1 (Knobel+, 2009) J/ApJ/684/905 : Galaxy clusters from IRAC Shallow Survey (Eisenhardt+, 2008) J/ApJS/172/182 : XMM Clusters of galaxies in COSMOS field (Finoguenov+ 2007) J/ApJS/157/1 : Red-Sequence Cluster Survey (Gladders+, 2005) J/AJ/130/968 : SDSS-C4 cluster catalog (Miller+, 2005) J/ApJS/139/369 : Chandra Deep Field South. 1 Ms catalog (Giacconi+, 2002) J/ApJS/129/435 : NORAS galaxy cluster survey. I. (Bohringer+, 2000) J/ApJ/496/39 : Properties of poor groups of galaxies. I. (Zabludoff+ 1998) http://www.sdss.org/ : SDSS home page Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 A5 --- --- [EGSXG] 7- 18 A12 --- ID Group identifier (JHHMM.m+DDMM) 20 A1 --- f_ID [a] a: galaxy group previously reported in Jeltema et al. (2009MNRAS.399..715J) 22- 30 F9.5 deg RAdeg Right ascension (J2000) (1) 32- 39 F8.5 deg DEdeg Declination (J2000) (1) 41- 45 F5.3 --- z [0.06/1.6] Redshift (2) 47- 50 F4.2 10-17W/m2 Fx [0.06/4.3] 0.5-2keV flux (10-^14^erg/cm^2^/s) 52- 55 F4.2 10-17W/m2 e_Fx [0.02/0.5] 1{sigma} error on Fx 57- 61 F5.2 10+35W Lx [0.5/63.6] Rest-frame luminosity in the 0.1-2.4keV (10^42^erg/s) 63- 67 F5.2 10+35W e_Lx [0.04/13.2] Lx uncertainty 69- 73 F5.2 10+13Msun M200 [1.3/13.4] Estimated total mass M_200_ (3) 75- 78 F4.2 10+13Msun e_M200 [0.06/1.6] M200 uncertainty 80- 82 F3.1 arcmin r200 [0.9/6.5] X-ray radial cut r_200_ (4) 84 I1 --- q_ID [1/4] Flag from our identification, 1=best (5) 86- 87 I2 --- Nz [0/28] Number of spectroscopic member galaxies inside r200 89- 93 F5.2 --- Sig [1.9/16.3] Flux significance 95- 97 I3 km/s sigX [202/503] Velocity dispersion estimated from X-ray luminosity {sigma}_X_ -------------------------------------------------------------------------------- Note (1): RA and DEC of the peak of X-ray emission in Equinox J2000.0. Note (2): The mean of the red-sequence redshifts, which is substituted with the median of the spectroscopic redshifts in cases where there is a spectroscopic redshift determination for the group member galaxies. Note (3): The estimated total mass, M_200_, computed following Leauthaud et al. (2010ApJ...709...97L) and assuming a standard evolution of scaling relations: M_200_E_z_=f(L_x_E^-1^_z_) where E_z_=({Omega}_M_(1+z)^3^+{Omega}_{Lambda}_)^1/2^. Note (4): The corresponding r_200_: M_200_=(4/3){pi}r^3^_200_(200{rho}_critical_). Note (5): Flag to each extended source that describes the quality of the identification (see section 3): 1 = confident redshift assignment, significant X-ray emission, and good centering, 2 = the centering has a large uncertainty. In the cases where a single X-ray source has been matched to several optical counterparts, the assigned flag is equal to 2 or larger. 3 = no spectroscopic confirmation but good centering, 4 = unlikely redshifts due to the lack of spectroscopic objects and red galaxies and also a large uncertainty in centering. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 A5 --- --- [EGSXG] 7- 18 A12 --- ID Group identifier (JHHMM.m+DDMM) 20- 32 F13.9 deg RAdeg Right Ascension in decimal degrees (J2000) 34- 45 F12.9 deg DEdeg Declination in decimal degrees (J2000) 47- 54 F8.6 --- z [0.06/1.6] Redshift -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Nov-2014