------------------------------------------------------------ COSMOS X-RAY GROUP MEMBERSHIP CATALOG - cosmos_xgroups_20110914a_public.fits 2011 September 14, updated 2011 November 15 (v20110914a) Matt George and Alexie Leauthaud mgeorge@astro.berkeley.edu, asleauthaud@lbl.gov ------------------------------------------------------------ This is a COSMOS X-ray group membership catalog, combining X-ray group properties from Finoguenov et al. in prep. (also 2007) (catalog Xmass_chaxmm10_mie_ext6_id_update1010_zupdate.cat) with estimates for masses and radii calibrated from weak lensing (Leauthaud et al. 2010), and member galaxy information (George et al. 2011, ApJ 742, 125. arxiv:1109.6040). Group redshifts have been determined by searching for red sequence overdensities within 500 kpc of the X-ray centers and are refined by using spectroscopic redshifts when available. We use groups with z<1 to ensure good optical identifications and small photoz uncertainties. There are slight differences between masses and radii in Alexis' X-ray catalog and Alexie's lensing values that stem from differences in the cosmological parameters used and perhaps rounding issues when storing variables and converting from linear to log units. Alexis uses OmegaM=0.25, Alexie uses OmegaM=0.258 (WMAP5). We expect that this is the version of the catalog that will be made publicly available. Please let us know if you find problems or have suggested changes to be made. ----------BASIC PROPERTIES AND X-RAY MEASUREMENTS---------- GROUP_ID - Group ID from X-ray catalog REDSHIFT - Group redshift (specz when available, red sequence otherwise) REDSHIFT_ERR - Group redshift uncertainty LX - log10[X-ray luminosity 0.1-2.4 keV], from Alexis' catalog LX_ERR - log10[uncertainty in LX], from Alexis' catalog LX_SCALE - log10[X-ray luminosity/E(z)], from Alexis' catalog XRAY_FLUX - log10[extrapolated flux (0.5-2 keV band) within R500 in ergs/s/cm^2], from Alexis' catalog XRAY_FLUX_ERR - log10[error on the flux], from Alexis' catalog RA - X-ray RA from Sextractor ellipse (cosmos_m46finalmie_ext5.txt) DEC - X-ray Dec from Sextractor ellipse (cosmos_m46finalmie_ext5.txt) XRAY_POS_ERR - X-ray position uncertainty (32" for XFLAG>1, 32"/significance for XFLAG=1) NAME - IAU formatted name COSMOS CL JHHMMSS.S+DDMMSS using coordinates from Alexis' catalog ----------GROUP QUALITY FLAGS---------- Alexis' catalog includes a quality flag based on the confidence in the optical identification. We include a few additional flags to identify cases where two groups are overlapping and membership identification is unclear (FLAG_MERGER), where we do not find a significant concentration of photoz members (FLAG_POOR), and where member selection may be affected by masks (FLAG_MASK). FLAG_INCLUDE is meant to combine these quality flags into a single selection. XFLAG - quality flag from X-ray catalog 1 - can use X-ray center, all good 2 - good ID, but cannot use X-ray center 3 - ID needs to be checked spectroscopically (Higher flags not included in this catalog) 4 - projection effects, no unique ID 5 - ID is potentially wrong 6 - ID is ok, but this is not a group 7 - no ID possible 8 - no photometry is available FLAG_MERGER - merger flag 1 - LENSING_R200 overlaps by more than 25% in radius and dz<0.01 with another group FLAG_POOR - poorness flag 1 if N_MEM <= 3 FLAG_MASK - mask flag 1 - >10% of area within LENSING_R200 or area within Rscale masked by stars, image defects, or edge of ACS coverage (ACS + Subaru B, V, I, z masks) FLAG_INCLUDE - combined quality flag 1 - good, FLAG1<3, FLAG_MERGER=0, FLAG_POOR=0, FLAG_PROJECTION=0, FLAG_MASK=0 ----------LENSING-CALIBRATED PROPERTIES---------- M200c - log10[M200] from WL-calibrated LX-M scaling relation (mass within radius where mean density is 200 times critical density) R200_MPC - R200 in Mpc R200_AS - R200 in arcsec, at group redshift CONC200c - C200 concentration from Zhao 2009 M-c (C=R200/Rscale) ----------MEMBER STATISTICS---------- NMEM - Number of objects in galaxy catalog with P_MEM > 0.5 for this group NMEM_W - Sum of P_MEM for objects in galaxy catalog for this group ----------GROUP CENTERS---------- Multiple "centers" are defined, and corresponding positions, galaxy IDs, stellar masses, and positional uncertainties are saved. From the lensing signals stacked on these centers, MMGGs appears to be the best tracer of the center of mass. These results are preliminary and do not imply that MMGGs is at the center of mass of each group. To study central galaxies, one may wish to confirm that a galaxy is both the most massive within the scale radius as well as the most massive in the group. MMGGs - most massive group galaxy within Rscale + X-ray positional error of X-ray center, using photoz selection only MMGGs_ZBEST - most massive group galaxy within Rscale + X-ray positional error of X-ray center, using speczs when available, else photozs Each center has a position associated with it, e.g ALPHA_MMGGs - RA (J2000) of MMGGs DELTA_MMGGs - Dec (J2000) of MMGGs ... We save the object ID in the galaxy catalog and the galaxy stellar mass, e.g. ID_MMGGs - ID for MMGGs galaxy from galaxy catalog SM_MMGGs - stellar mass for MMGGs galaxy ... ----------COSMOLOGICAL PARAMETERS (WMAP5)---------- Omega b 0.0438000 Omega m 0.258000 Omega l 0.742000 H0 72.0000 Sigma_8 0.796000 ----------EXTERNAL FILES USED---------- X-ray catalog - Xmass_chaxmm10_mie_ext6_id_update1010_zupdate.cat X-ray SExtractor coords - cosmos_m46finalmie_ext5.txt Photoz catalog - photoz_vers1.7_010809 Photoz PDFs - pdzBay_v1.7_010809.out.gz Image mask (FLAG_MASK) - COSMOS_borders_F814W_mask.fits Spectroscopic catalog - observed_targets_20110513.dat ----------VERSION HISTORY---------- 20101006 - initial release (beta version) 20110209 - fixed bug in field density estimate, shifting membership threshold from P>0.7 to 0.5. Minor fix replacing a small number of missing photozs for bright sources with speczs. Replaced X-ray catalog Xmass_cha54xmm_mie_ext5_zupdate0510_zerr.cat with Xmass_chaxmm10_mie_ext6_id_update1010_zupdate.cat 20110914 - modified field names and null values. updated spectroscopic catalog to include zCOSMOS 20k and exclude IMACS spectra. Trimmed catalogs to groups with XFLAG<=3, and galaxies with a stellar mass. Removed some fields for streamlining. 20110914a - modified field names again to follow IRSA guidelines. Added MMGGS_ZBEST column to galaxy catalog. The data should be unchanged from 20110914.