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EXSS: Help

EXSS - Einstein Extended Source Survey


Overview

The Einstein Extended Source Survey (EXSS) catalog contains a list of extended sources found in the Einstein Observatory Imaging Proportional Counter (IPC) Database. The source detection algorithm was substantially improved over that used for the Einstein Medium Sensitivity Survey (EMSS). Sources were searched for using circular apertures with variable radii of up to 6.1 arcminutes. Criteria were constructed so as to ascertain which of the detections were truly diffuse and which of the sizes best approximated each detection. Using these criteria, a catalog of 1325 extended source candidates at high galactic latitude (more than 20 degrees from the Galactic Equator) was produced. Cross-correlating this list with existing source catalogs yielded a reasonably comprehensive set of identifications for the sources in this list: over 400 were identified with known clusters of galaxies, while other objects were identified with galaxies, supernova remnants (SNR), active galactic nuclei (AGN), and stars. Whereas galaxies and SNR are often truly extended objects, AGN and stars can appear as extended ojects as a consequence of their soft X-ray spectra coupled with the broad point-spread function of the IPC at low energies. A total of 321 objects remain completely unidentified. Some of these may be heretofore uncatalogued clusters and groups of galaxies at moderate redshifts.

Catalog Bibcode

1997AJ....113.2134O

References

Oppenheimer, B.R., Helfand, D.J., and Gaidos, E.J., 1997, Astronomical Journal, 113, 2134.

Provenance

The data used to construct this database table were obtained from the first author's Web site on 12 December 1997.

Parameters

RA
Right Ascension of the X-ray source. This corresponds to the weighted average of the positions of the all of the detections of this source in the different apertures. The weighting factor is (radius squared/SNR squared) for each aperture.

Dec
Declination of the X-ray source. This corresponds to the weighted average of the positions of the all of the detections of this source in the different apertures. The weighting factor is (radius squared/SNR squared) for each aperture.

LII
Galactic longitude of the X-ray source.

BII
Galactic latitude of the X-ray source.

Name
The adopted name of the X-ray source using the recommendation from the CDS Dictionary of Nomenclature of Celestial Objects. Notice that this field was not present in the original database but was constructed by by the HEASARC.

Count_Rate_1
IPC photon counts per second for the aperture 1 (1.25 arcmin radius) detection.

Count_Rate_2
IPC photon counts per second for the aperture 2 (2.35 arcmin radius) detection.

Count_Rate_3
IPC photon counts per second for the aperture 3 (4.20 arcmin radius) detection.

Count_Rate_4
IPC photon counts per second for the aperture 4 (6.10 arcmin radius) detection.

SNR_1
Signal to noise ratio for the aperture 1 detection.

SNR_2
Signal to noise ratio for the aperture 2 detection.

SNR_3
Signal to noise ratio for the aperture 3 detection.

SNR_4
Signal to noise ratio for the aperture 4 detection.

RA_Offset_1
The offset in right ascension of the aperture 1 detection from the adopted object RA found using the technique described in the paper, in units of arcseconds.

Dec_Offset_1
The offset in declination of the aperture 1 detection from the adopted object declination (Dec) found using the technique described in the paper, in units of arcseconds.

RA_Offset_2
The offset in right ascension of the aperture 2 detection from the adopted object RA found using the technique described in the paper, in units of arcseconds.

Dec_Offset_2
The offset in declination of the aperture 2 detection from the adopted object declination (Dec) found using the technique described in the paper, in units of arcseconds.

RA_Offset_3
The offset in right ascension of the aperture 3 detection from the adopted object RA found using the technique described in the paper, in units of arcseconds.

Dec_Offset_3
The offset in declination of the aperture 3 detection from the adopted object declination (Dec) found using the technique described in the paper, in units of arcseconds.

RA_Offset_4
The offset in right ascension of the aperture 4 detection from the adopted object RA found using the technique described in the paper, in units of arcseconds.

Dec_Offset_4
The offset in declination of the aperture 4 detection from the adopted object declination (Dec) found using the technique described in the paper, in units of arcseconds.

Ppm_Number
Star number from the Positions and Proper Motions (PPM) Catalog for the star which is identified with the EXSS source. A null value means that no PPM star was identified with the EXSS source.)

Vmag
The V band magnitude of the PPM star identified with the EXSS source. A null value means that no PPM star was identified with the EXSS source.

Delta_RA_Ppm
The right ascension difference between the PPM star's position and the EXSS position in arcseconds.

Delta_Dec_Ppm
The declination difference between the PPM star's position and the EXSS position in arcseconds.

Emss_Name
The name of the EMSS source identified with the EXSS source

Emss_Type
The type of the EMSS source (from the EMSS catalog): AGN, CL (cluster of galaxies), BL (BL Lac-type object), GAL ("normal galaxy), or STAR.

Emss_SNR
The signal to noise ratio of the EMSS source with the EMSS detection algorithm.

Delta_RA_Emss
The right ascension difference between the EMSS position and the EXSS position in arcseconds.

Delta_Dec_Emss
The declination difference between the EMSS position and the EXSS position in arcseconds.

Zwicky_Name
The name of the Zwicky cluster of galaxies identified with the EXSS source

Zwicky_Size
The approximate size of the Zwicky cluster in arcseconds (from the Zwicky catalog)

Delta_RA_Zwicky
The right ascension difference between the Zwicky cluster's position and the EXSS position in arcseconds.

Delta_Dec_Zwicky
The declination difference between the Zwicky cluster's position and the EXSS position in arcseconds.

Abell_Name
The name of the Abell cluster of galaxies identified with the EXSS source

Delta_RA_Abell
The right ascension difference between the Abell cluster's position and the EXSS position in arcseconds.

Delta_Dec_Abell
The declination difference between the Abell cluster's position and the EXSS position in arcseconds.

Einline_Type
The type of the corresponding source in the EINLINE database that is identified with the EXSS source. (See EINLINE for an explanation of the abbreviations.)

Delta_RA_Einline
The right ascension difference between the EINLINE position and the EXSS position in arcseconds.

Delta_Dec_Einline
The declination difference between the EINLINE position and the EXSS position in arcseconds.

Delta_Tot_Einline
The quadrature sum the RA and Declination differences between the EINLINE position and the EXSS position, in arcseconds.


Contact Person

Questions regarding the EXSS database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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