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A2PIC - HEAO 1 A-2 Piccinotti Catalog

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Overview

The HEAO 1 A-2 experiment's operations began on day 224 of 1977 (12 August 1977) and ended on day 739 of 1977 (9 January 1979). The A-2 experiment performed two independent, low-background, high-sensitivity surveys of the entire sky 6 months apart, the first scan during days 248 to 437 of 1977 (5 September 1977 - 13 March 1978) and the second scan during days 73 to 254 of 1978 (14 March 1978 - 11 September 1978). The authors analysed the A-2 data in order to obtain a complete flux-limited sample of extragalactic X-ray sources. The region between galactic latitudes of -20 and +20 degrees was excluded to minimize contamination from galactic sources. A circle of 6 degrees radius around the Large Magellanic Cloud sources was also excluded to prevent confusion problems. Therefore, there remained 65.5% of the sky (8.23 steradians) covered by this survey. The lowest statistical significance for the existence of the sources included in this catalog is 5 sigma, as required by the maximum likelihood methods used by the authors to determine the log N - log S parameters. Taking into account this statistical significance requirement, the authors estimated the completeness level of the first and second scans to be 1.25 and 1.8 R15 ct/s, respectively. 1 R15 ct/s is approximately 2.17 x 10^-11 erg/cm^2/s in the 2-10 keV energy band for a power-law spectyrum with a photon index of 1.65. This catalog contains data for 68 nongalactic sources (61 extragalactic and 7 unidentified sources) which were listed in Table 1 of the published catalog. The identified sources fall into several categories, including narrow emission line galaxies, broad emission line galaxies, BL Lacertae objects, and clusters of galaxies.

Catalog Bibcode

1982ApJ...253..485P

References

The Piccinotti et al Catalog is available in "A Complete X-Ray Sample of the High-Latitude Sky From HEAO A-2: LOG N - LOG S and Luminosity Functions", G. Piccinotti, et al., Ap.J., 253:485-503, 1982 February. The HEASARC table is similar but not identical to Table 1 in this publication.

Provenance

This table was last revised by the HEASARC in November 2004 when 2 sources (H1257-042 and H1325-020) which had for some reason been omitted from the previous HEASARC version (the provenance of which is somewhat uncertain) were added back in to the table.

Description

The A-2 experiment consisted of six mechanically collimated, gas-filled, multilayer, multiwire proportional counters. The detectors are described in R. Rothchild, et al., Space Sci. Instr., 4, 265, 1979.

Parameters

A1name
The HEAO A1 catalog source name. The Naval Research Lab 1H catalog name.

BII
The galactic latitude corresponding to the given sky position.

Catalog_Designation
The HEAO A2 catalog source name, i.e., the Catalog name for the entry taken from the HEAO 1 Large Area Sky Survey (Wood, et al 1984).

Class
The HEASARC Browse classification assigned to the object.

Conversion
The count rate to flux conversion factor, in units of 10^-11 ergs/s/cm^2 per R15 ct/s. When spectral information was lacking, the authors assumed a 6 keV thermal bremsstrahlung spectrum for all sources identified with clusters and a 1.65 photon index power law spectrum for all sources identified with active galaxies. An average conversion factor of 2.5 x 10^-11 erg/s/cm^2 per R15 ct/s was assumed for the few unidentified sources.

Count_Rate
The count rate in R15 ct/s for the 1st scan flux. R15 is the counting rate derived using the 1.5 X 3 degree FWHM FOV of the 2nd layer of the argon counter and both layers of a xenon counter. One R15 ct/s equals about 2.17x10^-11 ergs/cm^2/sec in the 2-10 keV band, although different conversion factors (as given by the conversion parameter) were used for different classes of sources.

Count_Rate_Error
The 1-sigma error in the count rate for the 1st scan flux, in R15 ct/s.

Dec
The declination of the center of best fit A2 error box, in the selected equinox.

LII
The galactic longitude corresponding to the given sky position.

Lumin1
The X-ray luminosity in units of 10^44 erg/s of the source measured in the 1st 6-month pass of the survey, calculated for a Hubble Constant H_0 of 50 km/s/Mpc and a deceleration parameter q_0 of 0.5.

Lumin2
The X-ray luminosity in units of 10^44 erg/s of the source measured in the 2nd 6-month pass of the survey, calculated for a Hubble Constant H_0 of 50 km/s/Mpc and a deceleration parameter q_0 of 0.5.

Name
A commonly used source name, or optical identification, of the X-ray source.

Notes
Notes 1-3 were in the original data table and are not applicable here.

  4.  Two clusters at same z; IPC data give flux ratios of 2:1
  5.  Weak contribution from 0328-5244 cluster
  6.  Two sources in Piccinotti error box; Remillard (A3) ID used in table
  7.  Two clusters in same fov (A 3391, z= 0.0531)
  8.  M81 and M82 in FOV.  Best fit position is consistent with M82 having most
      of the flux.
  9.  MKN 766 in FOV.  Spectra indicates that 1215+30 has most of the flux.
  10. NGC4696 also noted in Jahoda list
  11. >2 clusters in FOV; Abell 3562 z=0.050
  12. Many Abell clusters in field (e.g. A 3572).  No IPC image.  Piccinotti
      redshift for different cluster (SC 1345-301).
  13. Possible confusion with A2063 (1521+083)and MKW3s(1519+0752)
  14. Abell 3827 nearby; z=0.0993.  ID based on richness and z, although both
      could be significant X-ray emitters.
  15. A 2440 (z = 0.0904) also in FOV.  Einstein images and EXOSAT/GINGA
      spectra have shown that the cluster is softer and would not lie above
      Piccinotti limit.
  16. S1101 (z = 0.0564) also in FOV.  Einstein images and EXOSAT/GINGA
      spectra have shown that the cluster is softer and would not lie above
      Piccinotti limit.
  

RA
The right ascension of the center of best fit A2 error box, in the selected equinox.

Redshift
The redshift of the source. References for these redshifts are available in Table 1 of the published catalog.

Second_Count_Rate
The count rate in R15 ct/s for the 2nd scan flux. R15 is the counting rate derived using the 1.5 X 3 degree FWHM FOV of the 2nd layer of the argon counter and both layers of a xenon counter. One R15 ct/s equals about 2.17x10^-11 ergs/cm^2/sec in the 2-10 keV band, although different conversion factors (as given by the conversion parameter) were used for different classes of sources. Notice that a small number of the sources were not detected in the second pass and have been assigned second_count_rate values of 0, and in such cases the second_count_rate_error parameter contains the upper limit to the R15 count rate.

Second_Count_Rate_Error
The 1-sigma error in the count rate for the 2nd scan flux, in R15 ct/s. Notice that a small number of the sources were not detected in the second pass and have been assigned second_count_rate values of 0, and in such cases the second_count_rate_error parameter contains the upper limit to the R15 count rate.


Contact Person

Questions regarding the A2PIC database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 2-Dec-2005