ETGALXRAY - Early-Type Galaxies X-Ray Luminosities Catalog

Overview

This table contains a catalog of X-ray luminosities for 401 early-type galaxies (and 24 other galaxies which were listed in previuous studies as early but which have LEDA T-types >= -1.5), of which 136 are based on newly analysed ROSAT PSPC pointed observations. The remaining luminosities are taken from the literature and converted to a common energy band, spectral model and distance scale. In their paper, the authors use this sample to fit the L_X/L_B relation for early-type galaxies and find a best-fit slope for the catalog of ~ 2.2. The authors demonstrate the influence of group-dominant galaxies on the fit and present evidence that the relation is not well modeled by a single power-law fit. They also derive estimates of the contribution to galaxy X-ray luminosities from discrete-sources and conclude that they provide L_{(discrete-source-contribution)}/L_B ~ 29.5 erg s^-1/L_Bsun. The authors compare this result with luminosities from their catalog. Lastly, they examine the influence of environment on galaxy X-ray luminosity and on the form of the L_X/L_B relation. They conclude that although environment undoubtedly affects the X-ray properties of individual galaxies, particularly those in the centres of groups and clusters, it does not change the nature of whole populations.

The sample of early-type galaxies was selected from the Lyon-Meudon Extragalactic Data Archive (LEDA). This catalog at that time contained information on ~ 100,000 galaxies, of which ~ 40,000 had redshift and morphological data. Galaxies were selected using the following criteria:

(i) Morphological Type T < -1.5 (i.e. E, E-S0 and S0 galaxies).

(ii) Virgo-corrected recession velocity V <= 9,000 km s^-1.

(iii) Apparent Magnitude B_T <= 13.5.

The redshift and apparent magnitude restrictions were chosen in order to minimize the effects of incompleteness on their sample. The LEDA catalogue is known to be 90 per cent complete at B_T = 14.5, so the selection should be close to statistical completeness. The selection process produced ~ 700 objects. The authors then cross-correlated this list with a list of public ROSAT PSPC pointings. Only pointings within 30 arcminutes of the target were accepted, as, further off-axis, the PSPC point-spread function becomes large enough to make analysis problematic. This left 209 galaxies with X-ray data available.

The authors also added data from previously published catalogs, ROSAT PSPC All-Sky Survey values from Beuing et al. (1999, MNRAS, 302, 209), and Einstein IPC values from Fabbiano et al. (1992, ApJS, 80, 531) and Roberts et al. (1991, ApJS, 75, 751). These other references use a range of models to fit the data, different wavebands, distances and blue luminosities. O'Sullivan et al. corrected for these differences by converting the catalogs to a common set of values, as used for their own results.

All of the X-ray luminosities have been converted to a common format based on a reliable distance scale (assuming H₀ = 75 km s^-1 Mpc^-1), and correcting for differences in spectral fitting techniques and waveband.

Catalog Bibcode

2001MNRAS.328..461O

References

A catalogue and analysis of X-ray luminosities of early-type galaxies.
    O'Sullivan E., Forbes D.A., Ponman T.J.
   <Mon. Not. R. Astron. Soc. 328, 461 (2001)>
   =2001MNRAS.328..461O

Provenance

This table was created by the HEASARC in October 2010 based on CDS catalog J/MNRAS/328/461 file table3.dat.

HEASARC Implementation

The HEASARC added positions to this table using the NED name resolver. Two of the original object names, 'ESO-LV 109-0221' and 'ESO-LV 92-0130', were changed (to 'ESO-LV 1090221' and 'ESO-LV 0920130', respectively) to conform to the current NED name standards. The HEASARC also notes that the names in the original Table 3 as published and in the CDS table from which this HEASARC table is based are different: e.g., in the paper, these 2 objects are called 'E1090221' and 'E920130', respectively.

Parameters

Name
The name of the galaxy. Two of the original object names, 'ESO-LV 109-0221' and 'ESO-LV 92-0130', were changed (to 'ESO-LV 1090221' and 'ESO-LV 0920130', respectively) to conform to the current NED name standards. The HEASARC also notes that the names in the original Table 3 as published and in the CDS table from which this HEASARC table is based are different: e.g., in the paper, these 2 objects are called 'E1090221' and 'E920130', respectively.

Alt_Name
An alternate name for the galaxy.

RA
The Right Ascension of the galaxy in the selected equinox. The HEASARC added positions to this table using the NED name resolver.

Dec
The Declination of the galaxy in the selected equinox. The HEASARC added positions to this table using the NED name resolver.

LII
The Galactic Longitude of the galaxy.

BII
The Galactic Latitude of the galaxy.

Distance
The distance to the galaxy, in Mpc. Where possible, the authors take the distances from Prugniel and Simien (1996, A&A, 309, 749). These are computed using the model of Faber and Burstein (1988), which accounts for the influence of the Great Attractor and Virgocentric flow. For galaxies not listed in Prugniel & Simien they used distances from LEDA, which are corrected only for Virgocentric motion.

Log_Lb
The logarithm of the B-band luminosity of the galaxy, in units of the solar B-band luminosity of 5.2 x 10³² erg s^-1. This parameter is based on the B_T magnitude given in Prugniel and Simien, where possible. When these were unavailable, the authors used B_T values, or in some cases (indicated by log_lb_flag = 'Y') m_B values, from NED.

Log_Lb_Flag
This flag parameter is set to 'Y' to indicates that the log_lb value (the logarithm of the B-band luminosity of the galaxy) is based on an m_B magnitude rather than a B_T magnitude.

Log_Lx_Limit
This limit parameter is set to '<' if the corresponding log_lx parameter value is an upper limit rather than a detection.

Log_Lx
The logarithm of the X-ray luminosity of the galaxy, in erg s^-1. This is given in a pseudo-bolometric broad band in order to properly normalize the IPC and PSPC measurements.

Ref_Log_Lx
This parameter contains a reference code which indicates the source of the log_lx value as follows:

        B = Beuing et al. 1999, MNRAS, 302, 209
        F = Fabianno et al. 1992, ApJS, 80, 531
        R = Roberts et al. 1991, ApJS, 75, 751
        N = new values from this paper

T_Type
The galaxy's T-type (Hubble stage), as taken from LEDA.

Class
The HEASARC Browse object classification for the galaxy, based on the value of the t_type parameter, as follows:

        -5    < t_type < -3    = Elliptical Galaxy
        -2.99 < t_type < -1.5  = Lenticular (S0) Galaxy
        -1.49 < t_type < 8     = Spiral Galaxy

Contact Person

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

Page Author: Browse Software Development Team
Last Modified: Tuesday, 28-Aug-2012 16:44:25 EDT