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NGC4472CXO - NGC 4472 Chandra X-Ray Point Source Catalog

HEASARC
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Overview

The Chandra X-Ray Point Source Catalog of the giant elliptical galaxy NGC 4472 contains the results of a Chandra ACIS-S/Hubble Space Telescope (HST) study of the point sources of this Virgo Cluster galaxy. The authors ran WAVDETECT from the CIAO 2.2 software package using wavelet scales from 1 to 16 pixels spaced by factors of 2, setting a false-source probability detection threshold of 10^-6, which should yield an expectation value of slightly less than one false source over the entire ACIS-S chip. They identify 144 X-ray point sources outside the nuclear region, 72 of which are located within the HST fields. An additional 3 sources are within 8" of the center of the galaxy and appear to be associated either with a weak active galactic nucleus or with brightness enhancements in the hot interstellar gas. One additional source (not included in this table) appears to be a spurious detection, as WAVDETECT assigns it a count rate of 1.5 counts, and visual inspection fails to find evidence of a source at that location. The optical data show 1102 sources whose half-light radii are small enough to be globular cluster candidates, 829 of which also have colors consistent with being globular clusters (with only four in the restricted central 10" region). 30 X-ray sources within 0.7" of an optical source with optical colors consistent with being globular clusters were found. Two additional sources show optical colors outside the globular cluster color range and are likely to be either foreground or background objects. The thirty globular cluster matches are likely to be low-mass X-ray binaries (LMXBs) associated with the globular clusters, while ~ 42 of the X-ray sources have no optical counterparts to V <~ 25 and I <~ 24, indicating that they are likely to be predominantly LMXBs in the field star population with a small amount of possible contamination from background active galactic nuclei. Thus approximately 40% of the X-ray sources are in globular clusters and ~ 4% of the globular clusters contain X-ray sources.

This HEASARC table contains the X-ray data for the above-mentioned 147 detected X-ray sources, and the correlative optical data for the 30 optical counterparts which have colors consistent with being globular clusters. It does not contain the data from the full list of optical sources which were given in Table 2 of the reference paper.


Catalog Bibcode

2003ApJ...586..814M

References

The low-mass X-ray binary-globular connection.
II. NGC 4472 X-ray source properties and source catalogs.
    Maccarone T.J., Kundu A., Zepf S.E.
   <Astrophys. J. 586, 814 (2003)>
   =2003ApJ...586..814M

Provenance

This table was created by the HEASARC in May 2007 based on CDS table J/ApJ/586/814 files table1.dat and table3.dat.

Parameters

Source_Number
A running X-ray source number in order of increasing J2000.0 Right Ascension.

Alt_Name
An alternative name for the X-ray source using the '[MKZ2003] XID' prefix (for Maccarone, Kundu, Zepf 2003 X-ray identification), and the X-ray source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

Name
The name for the X-ray source using the 'CXOMKZ' prefix (for Chandra X-Ray Observatory, Maccarone, Kundu, Zepf) and the J2000.0 equatorial coordinates (JHHHMMSSs+DDMMSS), as registered with the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the X-ray source in the selected equinox. This was obtained from the RA part of the position of the source given in the name field, which was in J2000.0 coordinates to a precision of 0.1 seconds of time. All positions reported in the tables are in the USNO-A2.0 coordinate frame.

Dec
The Declination of the X-ray source in the selected equinox. This was obtained from the Dec part of the position of the source given in the name field, which was in J2000.0 coordinates to a precision of 1 arcsecond. All positions reported in the tables are in the USNO-A2.0 coordinate frame.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source

Spectral_Index
The X-ray spectral index of the source. The X-ray spectra were binned so that at least 20 photons from the source region (which includes some background photons) are in each channel so as to allow reliable chi-squared fitting, although the highest and lowest energy bins may have fewer than 20 photons. The X-ray spectral index, Gamma, where dN/dE = E^(-Gamma), was found from fitting the Chandra spectrum in the 0.5 to 8.0 keV energy range with an absorbed power-law model, or when there were fewer than four channels from 0.5 to 8.0 keV for the spectral fit, was assumed to have a value of 2.0. In all cases, the neutral hydrogen column was frozen to the Galactic value in the direction of NGC 4472 of 1.6 x 10^20 cm^-2.

Spectral_Index_Pos_Err
The 90% error in the positive direction for the X-ray spectral index, Gamma. For spectra having a small number of spectral bins, Gamma was frozen to 2.0 and no errors are given. There are also no errors quoted for sources with Chi^2/DOF > 2.0.

Spectral_Index_Neg_Err
The 90% error in the negative direction for the X-ray spectral index, Gamma. For spectra having a small number of spectral bins, Gamma was frozen to 2.0 and no errors are given. There are also no errors quoted for sources with Chi^2/DOF > 2.0.

SB_Flux
The observed (absorbed) soft-band (0.5 - 2.0 keV) X-ray model flux of the source, in erg/s/cm^2. This flux was obtained using the 'flux' command in XSPEC.

HB_Flux
The observed (absorbed) hard-band (2.0 - 8.0 keV) X-ray model flux of the source, in erg/s/cm^2. This flux was obtained using the 'flux' command in XSPEC.

Lx
The full-band (0.5 - 8.0 keV) X-ray luminosity of the source. This comes from assuming the spectral model of an absorbed power-law, isotropic emission, a distance to NGC 4472 of 16 Mpc, and correcting the X-ray flux for the adopted Galactic absorption.

Chi_Squared
The chi^2 value of the model fit to the observed X-ray spectrum.

DoF
The number of degrees of freedom for the model fit to the observed X-ray spectrum.

Good_Region_Flag
This parameter, the good region flag, is set to 'Y' if the source is outside the central 8" region , or is set to 'N' if the source is inside this central region and appears to be associated either with a weak active galactic nucleus or with brightness enhancements in the hot interstellar gas.

HST_Region_Flag
This parameter, the HST region flag, is set to 'Y' if the source in one or more of the HST observation regions, else is set to 'N'.

Optical_Source_Number
A running optical source number in order of increasing J2000.0 Right Ascension.

Optical_Name
The name for the optical source identified as the counterpart to the X-ray source, using the '[MKZ2003] OID' prefix (for Maccarone, Kundu, Zepf 2003 optical identification) and the optical source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

Spectral_Index_Flag
This parameter flags badly fit ('b') or fixed ('f') values of the X-ray spectral index, Gamma. The HEASARC notes that there are many sources (those with no optical counterparts) for which this parameter value was not expicitly set to 'f', but which have spectral index values of 2.0 and no quoted errors, implying that the values were indeed fixed.

RA_Optical_J2000
The J2000.0 Right Ascension of the optical source identified as the counterpart to the X-ray source. Sources within 10" of the center of NGC 4472, where the brightness of the hot gas and the possible weak AGN activity make the X-ray detection procedure likely to find sources that are not X-ray binaries, were not matched.

Dec_Optical_J2000
The J2000.0 Declination of the optical source identified as the counterpart to the X-ray source. Sources within 10" of the center of NGC 4472, where the brightness of the hot gas and the possible weak AGN activity make the X-ray detection procedure likely to find sources that are not X-ray binaries, were not matched.

Vmag
The V magnitude of the optical source identified as the counterpart to the X-ray source.

Vmag_Error
The RMS uncertainty in the V magnitude of the optical source.

Imag
The I magnitude of the optical source identified as the counterpart to the X-ray source.

Imag_Error
The RMS uncertainty in the I magnitude of the optical source.

VI_Color
The V-I color index of the optical source identified as the counterpart to the X-ray source.

VI_Color_Error
The RMS uncertainty in the V-I color index of the optical source.

Half_Light_Radius
The half-light radius of the optical counterpart to the X-ray source, in arcseconds.

Half_Light_Radius_Error
The RMS uncertainty in the half-light radius of the optical counterpart to the X-ray source, in arcseconds.


Contact Person

Questions regarding the NGC4472CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 8-Jun-2007