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ASCAEGCLUS - ASCA Elliptical Galaxies and Galaxy Clusters Catalog

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Overview

Utilizing ASCA archival data of about 300 objects - elliptical galaxies, groups, and clusters of galaxies - the authors performed systematic measurements of the X-ray properties of hot gas in their systems, and compiled them in this study. The steepness (power-law slope) of the luminosity-temperature (L-T) relation, LX ~ (kT)alpha, in the range of kT ~ 1.5 - 15 keV is alpha = 3.17 +/- 0.15, consistent with previous measurements. In the relation, the authors find two breaks at around intracluster medium (ICM) temperatures of 1 keV and 4 keV: alpha = 2.34 +/- 0.29 above 4 keV, 3.74 +/- 0.32 in the 1.5 to 5 keV range, and 4.03 +/- 1.07 below 1.5 keV. Two such breaks are also evident in the temperature and size relation. The steepness in the L-T relation at kT > 4 keV is consistent with the scale-relation derived from the CDM model, indicating that the gravitational effect is dominant in richer clusters, while poorer clusters suffer non-gravity effects. The steep L-T relation below 1 keV is mostly attributed to X-ray faint systems of elliptical galaxies and galaxy groups. The authors find that the ICM mass within the scaling radius R1500 (the radius within which the averaged mass density is 1500 times higher than the critical density) follows the relation of Mgas ~ T(2.33+/-0.07) from X-ray faint galaxies to rich clusters. Thus, the authors speculate that even such X-ray faint systems contain large-scale hot gas, which is too faint to detect.

For this project, the authors utilized all of the ASCA data of elliptical galaxies and clusters of galaxies. Several clusters were observed more than once, and they chose the observation with the longest exposure. The total number of objects that the authors identified as elliptical galaxies and clusters was 313, and these are listed in this table. Some of the objects could not be utilized for deriving various correlations, due to either having an unknown redshift (17 objects), an insignificant detection (13 objects listed below), or contamination of the environmental X-ray emission, such as cluster emission around non-cD elliptical galaxies (10 objects: NGC 4472, NGC 4406, NGC 4374, NGC 1404, NGC 499, NGC 6034, NGC 2865, NGC 4291, CL 2236-04 and RX J1031.6-2607). Thus, the authors analyzed the ASCA data for 292 objects, among which were ~ 50 elliptical galaxies and galaxy groups. In this study, the authors assumed the Hubble constant to be 50 h50 km s-1 Mpc-1 and q0 to be 0.

Table 1 of the reference paper (reproduced below) lists the 13 clusters for which only 90% confidence level upper limits to the flux in the observer's frame are available:

Name            Flux (0.5 - 2 keV) Upper Limit
                      (erg/s/cm2)

NGC 5018            9.8 x 1014
GHO 1322+3114       1.3 x 1013
J1888.16CL          5.9 x 1014
CL 0317+1521        4.5 x 1014
MS 1512.4+3647      1.0 x 1012
PRG 38              6.9 x 1014
SCGG 205            6.9 x 1014
RGH 101             9.1 x 1014
3C 184              8.5 x 1014
RX J1756.5+6512     1.6 x 1013
3C 324              5.4 x 1014
PDCS 01             2.8 x 1014
MS 0147.8-3941      5.0 x 1014

Catalog Bibcode

2004PASJ...56..965F

References

ASCA compilation of X-ray properties of hot gas in elliptical galaxies and
galaxy clusters: two breaks in the temperature dependences.
    Fukazawa Y., Makishima K., Ohashi T.
   <Publ. Astron. Soc. Jap., 56, 965-1009 (2004)>
   =2004PASJ...56..965F

Provenance

This table was created by the HEASARC in December 2011 based on CDA Catalog J/PASJ/56/965 files table3.dat, table4.dat, table5.dat, table6.dat and table7.dat.

Parameters

Name
The name of the object (elliptical galaxy or cluster of galaxies).

Sequence_Number
The ASCA observation sequence identifier.

Redshift_Flag
For 17 objects flagged by a value of 'E', no redshift was available and the authors had to estimate a value. Among the 17 objects without an available redshift, the Fe-K line was clearly detected in 3 clusters, and the authors obtained the redshift by fitting the spectra with the redshift parameter as a free parameter. For the remaining objects, they estimated the redshifts from the luminosity-temperature relation of Edge and Stewart (1991, MNRAS, 252, 414), LX = 1.0E43(kT /keV)2.79 erg s-11 (2-10 keV).

Redshift
The redshift z of the object.

Time
The date/time of the start of the ASCA observation.

End_Time
The date/time of the end of the ASCA observation.

RA
The Right Ascension of the ASCA pointing at the object in the selected equinox. This was given in J2000.0 decimal degrees to aprecision of 0.001 degrees (3.6") in the original table.

Dec
The Declination of the ASCA pointing at the object in the selected equinox. This was given in J2000.0 decimal degrees to aprecision of 0.001 degrees (3.6") in the original table.

LII
The Galactic Longitude of the ASCA pointing at the object.

BII
The Galactic Latitude of the ASCA pointing at the object.

Exposure
The exposure time of the ASCA observation, in seconds

Count_Rate
The X-ray count rate of the object, in ct s-1 1GIS-1.

Center_DetX
The x-coordinate of the center of the integration region for the spectra of the object, in units of DETX channels.

Center_DetY
The y-coordinate of the center of the integration region for the spectra of the object, in units of DETY channels.

Int_Inner_Radius
The inner radius of the integration region for the spectra of the objecy, in units of DETX/DETY channels.

Int_Outer_Radius
The outer radius of the integration region for the spectra of the object, in units of DETX/DETY channels.

NH
The adopted Galactic column density towards the object, in H atoms cm-2, taken from Stark et al. (1992, ApJS, 79, 77).

Spectral_Fit_Flag
This flag parameter indicates a note on the spectral fitting as follows:

        1 = result from fitting only the GIS spectrum
        2 = result from simultaneous fitting the GIS and SIS spectra
  

kT_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

kT
The inferred ICM temperature kT, in keV, from fitting the observed spectrum with a MEKAL plasma model with the Galactic column density towards the object. For objects with kT < 1.5 keV, the authors added a bremsstrahlung component to reproduce the emission from low-mass X-ray binaries in elliptical galaxies.

kT_Error
The 90% confidence uncertainty in kT, in keV.

Abundance_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

Abundance
The inferred metal abundance of the MEKAL plasma, relative to the solar metallicity of Anders and Grevesse (1989, GCA, 53, 197).

Abundance_Error
The 90% confidence uncertainty in the inferred metal abundance of the MEKAL plasma.

Thermal_Fraction
The fraction of observed flux due to the thermal MEKAL component inferred from the spectral fitting. The remaining flux is due to a bremsstrahlung component which was added for the low-temperature (kT < 1.5 keV) objects in order to reproduce the emission from low-mass X-ray binaries in elliptical galaxies

Radial_Flag
The meaning of this parameter is somewhat unclear to the HEASARC. The reference paper states that a flagged value for this parameter ('A' is used in this version) means that for this object the redshift was assumed in the radial fitting. It thus would seem to be similar to the redshift_flag parameter (q.v.): in fact, of the 17 objects with the redshift_flag set, 16 also have the radial_flag set, while, conversely, of the 25 objects which have the radial_flag set, 16 of them have the redshift_flag set.

Beta_1
The beta1 parameter value for the object's electron density dependence on radius, as inferred from the spatial fitting using a single-beta model. The authors represented the ICM density distribution with a standard single-beta model for all objects, as discussed in Section 3.5 of the reference paper.

Beta_1_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value.

Beta_1_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value.

Core_Radius
The core radius a1, in arcminutes, as inferred from the spatial fitting of the object's X-ray emission using a single-beta model. See Section 3.5 of the reference paper for more details

Core_Radius_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value.

Core_Radius_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Core_Radius_Kpc
The linear distance corresponding to the core radius a1, in (h50)-1 kpc, for the single-beta model fit.

Ne
The central value of the electron density n(0,1), in (h50)0.5 cm-3, as inferred from the spatial fitting of the object's X-ray emission using a single-beta model. See Section 3.5 of the reference paper for more details.

Ne_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Ne_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Total_Mass
The total mass within Rlimit, in (h50)-1 solar masses, as inferred from the spatial fitting of the object's X-ray emission using a single-beta model, where Rlimit (called detect_radius in this table) is the radius outside of which the ICM density is assumed to be zero. The authors determined Rlimit by increasing its value intil the radial-fitting chi-squared value did not significantly improve.

Gas_Mass
The gas mass within Rlimit, in (h50)-2.5 solar masses, as inferred from the spatial fitting of the object's X-ray emission using a single-beta model, where Rlimit (called detect_radius in this table) is the radius outside of which the ICM density is assumed to be zero. The authors determined Rlimit by increasing its value intil the radial-fitting chi-squared value did not significantly improve.

Gas_Mass_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Gas_Mass_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Detect_Radius_Limit
This limit parameter is set to '>=' if the corresponding parameter value might be a lower limit rather than an actual value.

Detect_Radius_Mpc
The Rlimit parameter, in (h50)-1 Mpc. This is the radius outside of which the ICM density is assumed to be zero, or, equivalently, the maximum radius out to which the ASCA GIS can detect X-ray emission. The authors determined its value by increasing it intil the radial-fitting chi-squared value did not significantly improve.

Detect_Radius
The Rlimit parameter, in arcminutes. This is the radius outside of which the ICM density is assumed to be zero, or, equivalently, the maximum radius out to which the ASCA GIS can detect X-ray emission. The authors determined its value by increasing it intil the radial-fitting chi-squared value did not significantly improve.

Flm_Flag
The meaning of this parameter is somewhat unclear to the HEASARC. The reference paper states that a flagged value for this parameter ('A' is used in this version) means that for this object the redshift was assumed in the flux, central surface brightness and luminosity calculation. It thus would seem to be similar to the redshift_flag parameter (q.v.): in fact, of the 17 objects with the redshift_flag set, 16 also have the flm_flag set, while, conversely, all 16 objects which have the flm_flag set also have the redshift_flag set.

Flux
The observed X-ray flux of the object in the 0.5 - 10 keV band in the observer's frame, in erg s-1 cm-2, obtained by integrating the simulated emission spectra of the best-fit single-beta model within the best-fit Rlimit value.

Central_SB
The central surface brightness of the object in the 0.5 - 10 keV band in the observer's frame, in erg s-1 cm-2 arcmin-2.

Central_SB_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Central_SB_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Lx_Tot
The bolometric X-ray luminosity of the object in the rest frame, in h50-2 erg s-1, defined as the emissivity of the single-beta plasma model in the 0.001 - 200 keV band in the rest frame.

Lx_Tot_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Lx_Tot_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Lx_Fraction
The fraction of the bolometric luminosity of the object for the single-beta plasma model that is emitted in the 0.5 - 10 keV band.

Lx_Tot_Inner_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

Lx_Tot_Inner
The bolometric X-ray luminosity in the rest frame, LX2, in h50-2 erg s-1, defined as the emissivity of the inner component in the double-beta plasma model for the emission from the object in the 0.001 - 200 keV band in the rest frame.

Lx_Tot_Inner_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Lx_Tot_Inner_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Lx_Tot_Outer
The bolometric X-ray luminosity in the rest frame, LX1, in h50-2 erg s-1, defined as the emissivity of the outer component in the double-beta plasma model for the emission from the object in the 0.001 - 200 keV band in the rest frame.

Lx_Tot_Outer_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

Lx_Tot_Outer_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Beta_1
The beta1 parameter value for the object's electron density dependence on radius, as inferred from the spatial fitting using a double-beta model, in which the core radius a_2_and beta value beta2 of the second, small-scale component are fixed at 10 (h50)-1 kpc and 0.7, respectively. This additional component is often required to fit poor clusters. 57 such clusters were fit using the double-beta model, the details of which are discussed in Section 3.5 of the reference paper.

DB_Beta_1_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value.

DB_Beta_1_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value.

DB_Core_Radius
The core radius a1, in arcminutes, as inferred from the spatial fitting of the object's X-ray emission using a double-beta model, in which the core radius a_2_and beta value beta2 of the second, small-scale component are fixed at 10 (h50)-1 kpc and 0.7, respectively. See Section 3.5 of the reference paper for more details.

DB_Core_Radius_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Core_Radius_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Core_Radius_Kpc
The linear distance corresponding to the core radius a1, in (h50)-1 kpc, for the double-beta model fit.

DB_Alt_Core_Radius_Kpc
The linear distance corresponding to the core radius in an alternate double-beta model in which the authors assumed beta1 = 0.6 for the outer beta-model component.

DB_Inner_Ne
The central value of the electron density for the inner component n(0,2), in (h50)0.5 cm-3, as inferred from the spatial fitting of the object's X-ray emission using a double-beta model. See Section 3.5 of the reference paper for more details.

DB_Inner_Ne_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Inner_Ne_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Outer_Ne
The central value of the electron density for the outer component n(0,1), in (h50)0.5 cm-3, as inferred from the spatial fitting of the object's X-ray emission using a double-beta model. See Section 3.5 of the reference paper for more details.

DB_Outer_Ne_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Outer_Ne_Pos_Err
The upper (positive) 90% confidence error in the ] corresponding parameter value, in the same units as the latter.

DB_Alt_Outer_Ne
The central value of the electron density n(0,1) for the outer component n0,1, in (h50)0.5 cm-3, as inferred from the spatial fitting of the object's X-ray emission using an alternate double-beta model in which beta1 = 0.6 is assumed for the outer component. See Section 3.5 of the reference paper for more details.

DB_Gas_Mass
The gas mass within Rlimit, in (h50)-2.5 solar masses, as inferred from the spatial fitting of the object's X-ray emission using a double-beta model, where Rlimit (called detect_radius in this table) is the radius outside of which the ICM density is assumed to be zero. The authors determined Rlimit by increasing its value intil the radial-fitting chi-squared value did not significantly improve.

DB_Gas_Mass_Neg_Err
The lower (negative) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Gas_Mass_Pos_Err
The upper (positive) 90% confidence error in the corresponding parameter value, in the same units as the latter.

DB_Alt_Gas_Mass
The gas mass within Rlimit, in (h50)-2.5 solar masses, as inferred from the spatial fitting of the object's X-ray emission using an alternate double-beta model in which beta1 = 0.6 for the outer beta-model component, where Rlimit (called detect_radius in this table) is the radius outside of which the ICM density is assumed to be zero. The authors determined Rlimit by increasing its value intil the radial-fitting chi-squared value did not significantly improve.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 9-Dec-2011