Hickson Group ivo://nasa.heasarc/hcg NASA/GSFC HEASARC Hickson, Kindl, Auman; Hickson 2026-04-17 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Cluster of Galaxies The HCG database table is based on the Hickson Catalog, which is a list of 100 compact groups of galaxies that were identified by a systematic search of the Palomar Observatory Sky Survey red prints. Each group contains four or more galaxies, has an estimated mean surface brightness brighter than 26.0 magnitude per arcsec<sup>2</sup> and satisfies an isolation criterion. Dynamical parameters which were derived for 92 of the 100 groups are also included in the database. (Note that the Hubble constant was assumed to be Ho = 100 km/s/Mpc.) This database table essentially contains the information given in Table 1 of Hickson, P. (1982, ApJ, 255, 382) and Table 3 of Hickson, P. et al. (1992, ApJ, 399, 353). Consequently, the information on individual galaxies in the Hickson groups that is also given in these references, e.g., in Table 2 of Hickson, P. et al. (1992, ApJ, 399, 353), is not in the HCG database table; however, the latter data can be found in the related HEASARC database table HCGGALAXY. This online catalog was created by the HEASARC in August, 1999, based on machine-readable tables obtained from the ADC/CDS data centers (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/VII/213:">CDS catalog VII/213:</a> files groups.dat and dynamics.dat). The HEASARC refined the coordinates, corrected the dynamics_flag values, and updated the table's metadata in August, 2005. This is a service provided by NASA HEASARC . 1982ApJ...255..382H https://heasarc.gsfc.nasa.gov/W3Browse/all/hcg.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=hcg& GET text/xml 180 99999 true 195.54158001 -32.76815749 0.0833333333333333 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=hcg GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_hcg&Action=More+Options&Action=Parameter+Search&ConeAdd=1 GALAXY CATALOG 0.0833333333333333 Optical public hcg Hickson Compact Groups of Galaxies (HCG) Catalog name HCG Catalog Compact Group Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable member_count Number of Galaxies in Group short nullable brightest_mag Brightest Member Red Magnitude mag float nullable redshift Group Redshift Derived from the Median Galaxy Heliocentric Velocity src.redshift double nullable alt_name3 Alternative Designation 3 char nullable log_virial_mass Log10 of Virial Mass of Group (in grams) log(g) float nullable log_crossing_time Log10 of Crossing Time (in 1/H_0 Units) log(1/Ho) float nullable group_type Group Type Classification char nullable log_tot_luminosity Log10 of Total Blue Luminosity of the Accordant Galaxies (in W) log(W) float nullable angular_size Group Angular Diameter (arcmin) arcmin float nullable lii Galactic Longitude degree pos.galactic.lon double nullable number_galaxies Number of Galaxies with Accordant Velocities short nullable log_mass_density Log10 of Mass Density (in g/cm^3) log(g/cm^3) float nullable log_average_mass Log10 of Average Mass (in grams) log(g) float nullable log_vel_dispersion Log10 of Estimated Intrinsic 3D Velocity Dispersion (in km/s) log(km/s) float nullable log_projected_mass Log10 of Projected Mass (in grams) log(g) float nullable log_median_mass Log10 of Median Mass (in grams) log(g) float nullable dynamics_flag Flag Indicates Dynamics Info Present char nullable log_sigma_vrad Log10 of Radial Velocity Dispersion (in km/s) log(km/s) float nullable brightest_redshift Redshift of Brightest Galaxy double nullable log_mass_to_light Log10 of Mass-to-Light Ratio (in Solar Units) log(Sun) float nullable alt_name4 Alternative Designation 4 char nullable bii Galactic Latitude degree pos.galactic.lat double nullable hcg Hickson Compact Group Number short nullable log_adopted_mass Log10 of Adopted Mass (in grams) log(g) float nullable log_median_sep Log10 of Median Projected Separation (in kpc) log(kpc) float nullable alt_name2 Alternative Designation 2 char nullable alt_name1 Alternative Designation 1 char nullable tot_mag_group Total Red Magnitude of Group mag float nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable