RASSCALS - ROSAT All-Sky Survey CALS Galaxy Groups Catalog

Overview

This table contains the catalog from the ROSAT All-Sky Survey (RASS) Center for Astrophysics (CfA) Loose Systems, or RASSCALS, the largest X-ray and optical survey of low-mass galaxy groups as of its publication date in 2000. The authors drew 260 groups from the combined Center for Astrophysics and Southern Sky Redshift Surveys, covering one-quarter of the sky to a limiting Zwicky magnitude of m_z = 15.5. They detected 61 groups (23%) as extended X-ray sources. The X-ray detections have a median membership of nine galaxies, a median recession velocity cz = 7250 km/s, a median projected velocity dispersion sigma(p) = 400 km/s, and a median X-ray luminosity L(x) = 3 x 10⁴² /h(100)² erg/s, where the Hubble constant is H(0) = 100 h(100) km/s/Mpc.

The data in this table replace the preliminary analysis of the X-ray data which was presented in Mahdavi et al., 1999, ApJ, 518, 69 (CDS Cat. <J/ApJ/518/69>.

Catalog Bibcode

2000ApJ...534..114M

References

The RASSCALS: an X-ray and optical study of 260 galaxy groups.
    Mahdavi A., Bohringer H., Geller M.J., Ramella M.
   <Astrophys. J. 534, 114 (2000)>
   =2000ApJ...534..114M

Provenance

This table was created by the HEASARC in September 2005 based on CDS tables J/ApJ/534/114/table2.dat & table3.dat.

Parameters

Name
The RASSCALS object designation. The authors assigned each system a 7-character name, beginning with 'NRG', 'SRG', or 'SS2', followed by 'b' or 's' (specifying the angular size of the system as 'big', with cz < 8500 km/s, or 'small', with cz > 8500 km/s, respectively), followed by a 3-digit number.

RA
The Right Ascension of the galaxy group in the selected equinox. For the 59 groups with a listed X-ray luminosity, the position reported is the X-ray centroid, while for the others it is the mean position of the galaxies in the group. This was given in J2000.0 equatorial coordinates to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the galaxy group in the selected equinox. For the 59 groups with a listed X-ray luminosity, the position reported is the X-ray centroid, while for the others it is the mean position of the galaxies in the group. This was given in J2000.0 equatorial coordinates to a precision of 1 arcsecond in the original table.

LII
The Galactic Longitude of the galaxy group.

BII
The Galactic Latitude of the galaxy group.

N_Group
The number of known group members.

N_17
The number of group members brighter than an absolute magnitude M_z = -17, corresponding to an apparent Zwicky magnitude m_z = 15.5 for a group at cz = 3200 km/s. To calculate n₁₇, the authors assumed that the galaxies in groups have the same luminosity function as the CfA Redshift Survey (Marzke, Huchra and Geller 1994, ApJ, 428, 43), reconvolved with the magnitude errors. The resulting distribution is well-represented by a Schechter (1976, ApJ, 203, 297) function with a characteristic absolute magnitude M(*) = -19.1 and a faint-end slope alpha = -1. The median value of n₁₇ is 44.

Radial_Velocity
The recession velocity of the galaxy group, in km/s.

Radial_Velocity_Error
The RMS uncertainty in the recession velocity of the galaxy group, in km/s.

Log_Sigma_P
The log10 of the projected velocity dispersion of the galaxy group, in km/s.

Log_Sigma_P_Error
The RMS uncertainty in log10 of the projected velocity dispersion, in km/s.

Log_Lx_P5_Limit
The limit flag for the X-ray luminosity in the 0.1 - 2.4 keV band within an aperture of 0.5 h(100)^-1 Mpc.

Log_Lx_P5
The log10 of the X-ray luminosity of the galaxy group in the 0.1 - 2.4 keV band within an aperture of 0.5 h(100)^-1 Mpc, in h(100)^-2 erg/s.

Log_Lx_P5_Error
The RMS uncertainty in the log10 of the X-ray luminosity of the galaxy group in the 0.1 - 2.4 keV band within an aperture of 0.5 h(100)^-1 Mpc, in h(100)^-2 erg/s.

Log_Lx_P5_Flag
This parameter is a flag which is set to 'd' to indicate two X-ray luminous Abell clusters (NRGs372 and NRGs392) which the optical group finding algorithm has confused with the field. The authors counted these as detections, but did not calculate their other X-ray properties.

Alt_Names
Other identifications for the galaxy group, by no means complete:

         A: Abell (CDS Cat. <VII/4>) cluster
       AWM: Albert et al. (1977ApJ...211..309A) Groups
       HCG: Hickson Compact Groups (Hickson, 1982, CDS Cat. <VII/213>)
      MGBR: Studied in greater detail in Mahdavi et al. 1999
       MKW: Morgan, Kayser, & White (1975ApJ...199..545M) Groups
       PPS: Loose Groups in the Perseus-Pisces Survey
            (Trasarti-Battistoni, 1998, CDS Cat. <J/A+AS/130/341>)
        ZM: Zabludoff & Mulchaey (1998, CDS Cat. <J/ApJ/496/39>) Poor Groups

Log_Lx_P25
The log10 of the X-ray luminosity of the galaxy group in the 0.1 - 2.4 keV band within an aperture of 0.25 h(100)^-1 Mpc, in h(100)^-2 erg/s.

Log_Lx_P25_Error
The RMS uncertainty in the log10 of the X-ray luminosity of the galaxy group in the 0.1 - 2.4 keV band within an aperture of 0.25 h(100)^-1 Mpc, in h(100)^-2 erg/s.

Log_Lx_R_Xi
The log10 of the X-ray luminosity of the galaxy group in the 0.1 - 2.4 keV band within the NOCORE radius, R(xi), in h(100)^-2 erg/s.

Log_Lx_R_Xi_Error
The RMS uncertainty in the log10 of the X-ray luminosity of the galaxy group in the 0.1 - 2.4 keV band within the NOCORE radius, R(xi), in h(100)^-2 erg/s.

R_Xi
The NOCORE radius, R(xi), of the X-ray-detected galaxy group, in Mpc. R(xi) provides a characteristic scale for the X-ray emission, and, hence, for for the gravitational potential of the galaxy group. The procedure for estimating this quantity is discussed in Section 2.4 of the reference paper.

R_Xi_Error
The RMS uncertainty in the NOCORE radius, R(xi), in Mpc.

Log_Time_Cross
The log10 of the system's crossing time, in units of the Hubble time (H₀^-1), defined as R(xi)*H₀/sigma(p).

Log_Time_Cross_Error
The RMS uncertainty in log10 of the crossing time, in units of the Hubble time (H₀^-1).

F_Spiral
The fraction of group members that are spiral galaxies.

Contact Person

Questions regarding the RASSCALS database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: Friday, 20-Mar-2015 18:52:10 EDT