J/A+A/700/A98ivo://CDS.VizieR/J/A+A/700/A98doi:10.26093/cds/vizier/bc-nw/ljiCDSKosowski J.Finoguenov A.Tempel E.Mamon G.A.2026-09-04T07:56:03Z2025-08-08T09:03:02ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxy-clustersgalaxiescatalogsx-ray-sourcesredshiftedThe identification of X-ray and CMB sources as galaxy groups and clusters is a prerequisite for cluster cosmology. But the identification of groups, especially nearby ones, suffers from projection effects which in turn affect the purity of the sample. In X-rays, the position of the cluster can be given either by the peak of the emission, or by the full information content of the cluster image. Similarly, the optical center, or its member galaxies, can describe the optical counterpart. With the progress of numerical simulations, it is currently feasible to reproduce both the optical group membership assignment and the behavior of the group outskirts in X-rays, and therefore there is an opportunity to define a reproducible group identification procedure. We performed two-way matching between X-ray contours, drawn at a fixed surface brightness level corresponding to a baryonic overdensity of ~500, to the projected galaxy positions using a modified Hausdorff distance (MHD). We used the volume-limited SDSS group catalog to evaluate the purity and completeness of the procedure, maintaining the constant performance of the optical group finder with redshift. We find that an MHD of 0.631 Mpc provides 90% purity. This is a clear improvement over the methods that rely on the optical counterparts' distance and richness. We study the purity versus MHD and the completeness versus redshift and velocity dispersion. Over half of nearby groups have X-ray emission, even those with velocity dispersions as low as 200km/s; this has never previously been demonstrated. The bulk of these groups follow the same scaling relations as the groups with a small separation between the optical and X-ray centers, removing feedback as an explanation for the lack of matches in previous studies. Instead, the problem is caused by over-merging in the optical group catalog construction and source confusion in X-rays.2025A&A...700A..98Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/700/A98CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/566/A1 : Flux- and volume-limited groups for SDSS galaxieshttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/700/A98https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/700/A98http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/700/A98https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/700/A98https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/700/A98http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/700/A98GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/700/A98/v180mpc (X-ray properties of the AXES-SDSS 180Mpc group catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/700/A98/v180mpc?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/700/A98/v180mpc?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/700/A98/v180mpc?GETtext/xml+votable180.050000true247.1475139.147920.005555555555555556Cone search capability for table J/A+A/700/A98/v195mpc (X-ray properties of the AXES-SDSS 195Mpc group catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/700/A98/v195mpc?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/700/A98/v195mpc?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/700/A98/v195mpc?GETtext/xml+votable180.050000true247.1475139.147920.0055555555555555566/4340 4373 4488 4491 4534 4750 4932 4952 4992 5012 5030 5153 5229 5305 5311 5370 5373 5383 5436 5508 5524 5616 5689 5716 5739 5824 5894 5935 5974 5978 5980 5990 6001-6002 6039-6040 6045 6057 6069 6222-6223 6247 6436 6549 6741 7190 7198 7254 7271 7337 7340 7354 7681 8220 8261 8264 8266 8268 8270 8290 8418 8442 8512 8514 8537 8545 8555 8561 8574 8648 8693 8735 8746 8788 8852 8891 8926 8938 8961 9009 9013 9018 9026 9036 9048 9073 9162 9264 9287 9309 9332 9345 9368 9371 9443 9453 9468 9486 9504 9516 9519 9605-9606 9612 9632 9776 9793 9815 9827 9890 9983 9987 10154 10271 10285 10306 10311 10313 10340 10360 10438-10439 10442 10456 10617 10679 10684 10716 10822 10865 10901 11101 11158 11182 11279 11285 11341 11435 11809 11811 21971 25849 25981-25982 26031 26075 26109 26169 26184 26186 26188-26189 26271 26302 26432 26990 27045 27060 27079 27081 27218 27406 27417 27448 27486 27576 27606 27676 27685 27761 27775 27838 27851 27865 27943 27951 27966 28005 28016 28181 28294 28345 28360 28376 28402 28408-28409 28413-28414 28471 28491 28498 28529 28571 28597 28620 28663 31354 31407 31459 31693 32445-32446 32683https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/700/A98?format=asciiX-raydefaultJ/A+A/700/A98/v180mpcX-ray properties of the AXES-SDSS 180Mpc group catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGroupIDSDSS group identification number (GROUP_ID) (1)meta.id;meta.mainintXCIDExtended X-ray contour ID (XC_ID)meta.idlongRAJ2000Median right ascension of the matched part of X-ray contour (J2000) (RA_X)degpos.eq.ra;meta.mainDEJ2000Median declination of the matched part of X-ray contour (J2000) (DEC_X)degpos.eq.dec;meta.mainRAOdegMedian right ascension of the matched part of the optical group (J20 (RA_OPT)degpos.eq.raDEOdegMedian declination of the matched part of the optical group (J2000) (DEC_OPT)degpos.eq.decNmembNumber of spectroscopic members in SDSS group catalog (NMEM)meta.numberintzspecSDSS group redshift (ZSPEC)src.redshiftfloatCluVdispGapGapper estimate of the cluster velocity dispersion (CLUVDISP_GAP)km/sphys.veloc.dispersionfloatLX0.1-2.4Luminosity in the (0.1-2.4)keV band of the cluster, aperture R500c (LX0124)1e-07Wphys.luminosity;em.X-raydoublee_LX0.1-2.4Uncertainty on LX0124 (ELX0124)1e-07Wstat.errordoubleFlux0.5-2Galaxy cluster X-ray flux in the 0.5-2.0keV band (FLUX052)mW.m**-2phot.flux;em.X-raydoublee_Flux0.5-2Uncertainty on FLUX052 (EFLUX052)mW.m**-2stat.errordoubleRaeApparent radial extent of X-ray emission at the contour level (RA_E)arcminphys.angSizedoubleJ/A+A/700/A98/v195mpcX-ray properties of the AXES-SDSS 195Mpc group catalogCluVdispGapGapper estimate of the cluster velocity dispersion (CLUVDISP_GAP)km/sphys.veloc.dispersionfloatLX0.1-2.4Luminosity in the (0.1-2.4)keV band of the cluster, aperture R500c (LX0124)1e-07Wphys.luminosity;em.X-raydoublee_LX0.1-2.4Uncertainty on LX0124 (ELX0124)1e-07Wstat.errordoubleFlux0.5-2Galaxy cluster X-ray flux in the 0.5-2.0keV band (FLUX052)mW.m**-2phot.flux;em.X-raydoublee_Flux0.5-2Uncertainty on FLUX052 (EFLUX052)mW.m**-2stat.errordoubleRaeApparent radial extent of X-ray emission at the contour level (RA_E)arcminphys.angSizedoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGroupIDSDSS group identification number (GROUP_ID) (1)meta.id;meta.mainintXCIDExtended X-ray contour ID (XC_ID)meta.idlongRAJ2000Median right ascension of the matched part of X-ray contour (J2000) (RA_X)degpos.eq.ra;meta.mainDEJ2000Median declination of the matched part of X-ray contour (J2000) (DEC_X)degpos.eq.dec;meta.mainRAOdegMedian right ascension of the matched part of the optical group (J20 (RA_OPT)degpos.eq.raDEOdegMedian declination of the matched part of the optical group (J2000) (DEC_OPT)degpos.eq.decNmembNumber of spectroscopic members in SDSS group catalog (NMEM)meta.numberintzspecSDSS group redshift (ZSPEC)src.redshiftfloat