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ROSNEPOID - ROSAT North Ecliptic Pole Survey Optical Identifications

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Overview

This table contains the ROSAT North Ecliptic Pole (NEP) Survey list of optical identifications. The X-ray data around the NEP from the ROSAT All-Sky Survey (RASS) were used to construct a contiguous area survey which consisted of a sample of 445 individual X-ray sources with fluxes more than ~2x10^-14 erg/cm^2/s in the 0.5 - 2.0 keV energy band. The NEP survey is centered at RA= 18hr 00min Dec= +66deg 33', and covers a region of 80.7 square degrees at a moderate Galactic latitude b= 29.8 degrees. Hence, the NEP survey is as deep as and covers a comparable solid angle to the ROSAT serendipitous surveys but is also contiguous. The authors identified 99.6% of the sources and determined redshifts for the extragalactic objects.

This table contains the optical identifications for the NEP catalog of X-ray sources, including basic X-ray data and properties of the sources. The classification of the optical counterparts to the NEP sources is very similar to that of previous surveys, in particular the Einstein Extended Medium Sensitivity Survey (EMSS). The main constituents of the catalog are active galactic nuclei (AGN) (~49%), either type 1 or type 2 according to the broadness of their permitted emission lines. Stellar counterparts are the second most common identification class (~34%). Clusters and groups of galaxies comprise 14%, and BL Lacertae objects 2%. One non-AGN galaxy and one planetary nebula have also been found. The NEP catalog of X-ray sources is a homogeneous sample of astronomical objects featuring complete optical identification.

The data on AGN in this catalog are essentially superceded by the data in the more recent catalog of Mullis et al. (2004, ApJ, 617, 192), available in HEASARC Browse as the ROSNEPOID table (q.v.), in which, inter alia, a corrected count rate to flux conversion and a different cosmology were used.


Catalog Bibcode

2003ApJS..149...29G

References

The ROSAT North Ecliptic Pole Survey: the optical identifications.
    Gioia I.M., Henry J.P., Mullis C.R., Bohringer H., Briel U.G., Voges W.,
    Huchra J.P.
   <Astrophys. J. Suppl. Ser. 149, 29 (2003)>
   =2003ApJS..149...29G

Provenance

This table was created by the HEASARC in April 2005 based on CDS table J/ApJS/149/29/table3.dat

Description

The NEP region was observed many times by the ROSAT satellite since the RASS scan pattern overlapped at the ecliptic poles. While the mean RASS exposure time across the entire sky is approximately 400s, the NEP region exposure time approaches 40ks at the pole. The minimum, median, and maximum exposure times in the NEP survey regions are 1.7, 4.8, and 38ks, respectively.

Parameters

Name
The source name as given in the published paper, formed using the prefix 'RX J' (for ROSAT X-ray source, Julian 2000 position), and the Xray centroid position truncated to 0.1 minutes of time in RA and 1 arcmin in Declination. The Dictionary of Nomenclature of Celestial Objects suggests using an initial prefix of '[GHM2003]', notice, which we have chosen not to include herein.

Nep_Scan
The North Ecliptic Pole Scan source number, an internal source identification number which runs between 10 and 6570.

RA_Xray
The Right Ascension of the X-Ray source centroid in fixed J2000 coordinates. This was given to a precision of 0.1 seconds of time in the original table.

Dec_Xray
The Declination of the X-Ray source centroid in fixed J2000 coordinates. This was given to a precision of 1 arcsecond in the original table.

RA
The Right Ascension of the optical object associated with the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.1 seconds of time in the original table. Notice that two objects in this catalog, 'RX J1719.8+6457' and 'RX J1756.2+7042', have no identified optical counterpart near their X-ray locations, and have been given null values for their optical positions in the present table: these can thus not be found by positional searches, but can be found by, for example, name or other parameter searches.

Dec
The Declination of the optical object associated with the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 1 arcsecond in the original table. Notice that two objects in this catalog, 'RX J1719.8+6457' and 'RX J1756.2+7042', have no identified optical counterpart near their X-ray locations, and have been given null values for their optical positions in the present table: these can thus not be found by positional searches, but can be found by, for example, name or other parameter searches.

LII
The Galactic Longitude of the optical object associated with the X-ray source.

BII
The Galactic Latitude of the optical object associated with the X-ray source.

SNR
The Signal-to-Noise Ratio (SNR) for the detected (X-ray) source count rate, determined as the net source count rate divided by the 1-sigma uncertainty in the count rate.

Flux
The detect unabsorbed flux in the 0.5 - 2 keV energy range, in erg/s/cm^2. The detect flux is measured in the photometry circular aperture (5' radius). To determine the fluxes for the different classes of astronomical objects, the authors converted from count rate to unabsorbed flux using conversion factors based on three different types of source spectra (see Section 2 of the published paper).

Flux_Corr
The total unabsorbed flux in the 0.5 - 2 keV energy range, in erg/s/cm^2. The total flux accounts for the flux outside the photometry aperture and reflects the size correction applied to the detect flux. For point sources, this flux correction factor is constant and equal to 1.0369 (see Section 2 of the published paper), while it varies for extended sources, such as clusters or groups of galaxies. The flux correction factor used for extended sources is given in the comments parameter field.

Log_Lx
The logarithm of the rest-frame, K-Corrected 0.5 - 2 keV luminosity, in erg/s, given for extragalactic objects, with uncertainties based on the fractional errors in the source count rates. The K-correction factors for clusters of galaxies, assuming a Raymond-Smith plasma spectrum with a metallicity 0.3 solar, are 0.76, 0.95 and 1.01, minimum, median and maximum values respectively. For AGN, the assumed power law spectrum with an energy index = -1 gives a formal K-correction factor of 1.

Redshift
The spectroscopically measured redshift, given for extragalactic sources. The typical uncertainty is <=0.001.

Source_Type
The optical identification of the X-Ray source based on the following classification scheme:

      AGN = active galactic nucleus, either type 1 (AGN1) or type 2 (AGN2)
            (see Section 4 of the paper);
     STAR = star plus spectral type if known;
       CL = group or cluster of galaxies;
       BL = BL Lacertae object;
      GAL = normal galaxy;
       PN = Planetary Nebula.
  

Notes_Flag
This parameter is a flag which is set to 'N' to indicate that there is a note about the object in Section 6 of the published paper and available online at ftp://cdsarc.u-strasbg.fr/pub/cats/J/ApJS/149/29/notes.dat

Comments
This parameter lists some additional comments regarding the source, such as the size correction factor, sc, used for galaxy clusters.

Class
The HEASARC Browse object classification, based on the value of the source_type parameter.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 31-Aug-2005