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AXIS - AXIS XMM-Newton Source Catalog

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Overview

Recent results have revised upwards the total X-ray background (XRB) intensity below ~10 keV, therefore an accurate determination of the source counts is needed. There are also contradictory results on the clustering of X-ray selected sources. The authors have studied the X-ray source counts in four energy bands: soft (0.5 - 2 keV), hard (2 - 10 keV), XID (0.5 - 4.5 keV) and ultra-hard (4.5 - 7.5 keV) in order to evaluate the contribution of sources at different fluxes to the X-ray background. They have also studied the angular clustering of X-ray sources in those bands. AXIS (An XMM International Survey) is a survey of 36 high Galactic latitude XMM observations covering 4.8 square degrees in the Northern sky and containing 1433 serendipitous X-ray sources detected with 5-sigma significance. This survey has similar depth to the XMM catalogs and therefore serves as a pathfinder to explore their possibilities. The authors in their paper combined this survey with shallower and deeper surveys, and fitted the source counts with a Maximum Likelihood technique. Using only AXIS sources they studied the angular correlation using a novel robust technique.

The AXIS source counts results are compatible with most previous samples in the soft, XID, ultra-hard and hard bands. This study has improved on previous results in the hard band. The fractions of the XRB resolved in the surveys used in this work are 87%, 85%, 60% and 25% in the soft, hard, XID and ultra-hard bands, respectively. Extrapolation of the source counts to zero flux is not sufficient to saturate the XRB intensity. Only galaxies and/or absorbed AGN could contribute the remaining unresolved XRB intensity. These results are compatible, within the errors, with recent revisions of the XRB intensity in the soft and hard bands. The maximum fractional contribution to the XRB comes from fluxes within about a decade of the break in the source counts (~10^-14 cgs), reaching ~50% of the total in the soft and hard bands. Angular clustering (widely distributed over the sky and not confined to a few deep fields) is detected at 99-99.9% significance in the soft and XID bands, with no detection in the hard and ultra-hard band (probably due to the smaller number of sources). The authors cannot confirm the detection of significantly stronger clustering in the hard-spectrum hard sources. Medium-depth surveys such as AXIS are essential to determine the evolution of the X-ray emission in the Universe below 10 keV.

Included here are the basic data for the 2560 X-ray sources in the reference paper which satified the selection criteria of having an emldetect detection likelihood >= 10 (the default value) in at least one band, namely:

(i) XMM-Newton pn count-rates in four XMM-Newton Science Analysis System (SAS) bands (band 2: 0.5 - 2 keV, band 3: 2 - 4.5 keV, band 4: 4.5 - 7.5 keV, band 5: 7.5 - 12 keV); (ii) spectral photon indices in the 0.5 - 4.5 keV band, the 2 - 10 keV band and the 0.5 - 10 keV band; (iii) fluxes in the soft (0.5 - 2 keV), hard (2 - 10 keV), XID (0.5 - 4.5 keV), ultra-hard (4.5 - 7.5 keV) and "total" (0.5 - 10 keV) bands; and (iv) flags describing to which of the samples discussed in the paper (soft, hard, XID or ultra-hard) each source belongs.

There is no spectral or flux information given for the sources not belonging to any of the samples, but the count-rates of such sources are given for completeness.


Catalog Bibcode

2007A&A...469...27C

References

The XMM-Newton serendipitous survey.
III. The AXIS X-ray source counts and angular clustering.
    Carrera F.J., Ebrer J., Mateos S., Ceballos M.T., Corral A., Barcons X.,
    Page M.J., Rosen S.R., Watson M.G., Tedds J.A., Della Ceca R.,
    Maccacaro T., Brunner H., Freyberg M., Lamer G., Bauer F.E., Ueda Y.
    <Astron. Astrophys. 469, 27 (2007)>
    =2007A&A...469...27C        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in August 2007 based on CDS catalog J/A+A/469/27 file table23.dat.

Parameters

Name
The name for the X-ray source using the 'XMMU' prefix for an XMM-Newton X-ray source, and the truncated J2000.0 coordinates (JHHMMSS.s+DDMMSS), as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the X-ray source in the selected equinox. The RA was given in J2000.0 coordinates in degrees to a precision of 10^-6 degrees (= 0.0036 arcseconds) in the original table. The authors registered the X-ray source positions to the USNO-A2 reference frame field by field, using the SAS task eposcorr. This task shifts the X-ray reference frame to minimise the differences between the X-ray source positions and the positions of their optical counterparts in a given reference astrometric catalog (USNO-A2 in this case). The corrected positions are given in this table. The average shift in absolute value in RA (Dec) was 1.3 (0.9) arcsec, and in all cases the shifts were under 3 arcsec.

Dec
The Declination of the X-ray source in the selected equinox. The Declination was given in J2000.0 coordinates in degrees to a precision of 10^-6 degrees (= 0.0036 arcseconds) in the original table. The authors registered the X-ray source positions to the USNO-A2 reference frame field by field, using the SAS task eposcorr. This task shifts the X-ray reference frame to minimise the differences between the X-ray source positions and the positions of their optical counterparts in a given reference astrometric catalog (USNO-A2 in this case). The corrected positions are given in this table. The average shift in absolute value in RA (Dec) was 1.3 (0.9) arcsec, and in all cases the shifts were under 3 arcsec.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The 90% uncertainty radius in the X-ray position, in arcseconds.

SB2_Count_Rate
The count rate of the X-ray source in the 0.5 - 2 keV band (SAS band 2), in counts per second.

SB2_Count_Rate_Error
The uncertainty in the X-ray source count rate in the 0.5 - 2 keV band (SAS band 2), in counts per second.

SB2_Detect_Likelihood
The X-ray source likelihood of detection in the specified band.

SB3_Count_Rate
The count rate of the X-ray source in the 2 - 4.5 keV band (SAS band 3), in counts per second.

SB3_Count_Rate_Error
The uncertainty in the X-ray source count rate in the 2 - 4.5 keV band (SAS band 3), in counts per second.

SB3_Detect_Likelihood
The X-ray source likelihood of detection in the specified band.

SB4_Count_Rate
The count rate of the X-ray source in the 4.5 - 7.5 keV band (SAS band 4), in counts per second.

SB4_Count_Rate_Error
The uncertainty in the X-ray source count rate in the 4.5 - 7.5 keV band (SAS band 4), in counts per second.

SB4_Detect_Likelihood
The X-ray source likelihood of detection in the specified band.

SB5_Count_Rate
The count rate of the X-ray source in the 7.5 - 12 keV band (SAS band 5), in counts per second.

SB5_Count_Rate_Error
The uncertainty in the X-ray source count rate in the 7.5 - 12 keV band (SAS band 5), in counts per second.

SB5_Detect_Likelihood
The X-ray source likelihood of detection in the specified band.

Xid_Count_Rate
The count rate of the X-ray source in the 0.5 - 4.5 keV band (XID band), in counts per second.

Xid_Count_Rate_Error
The uncertainty in the X-ray source count rate in the 0.5 - 4.5 keV band (XID band), in counts per second

Xid_Detect_Likelihood
The X-ray source likelihood of detection in the specified band.

Soft_Spect_Index
The X-ray spectral photon index Gamma_s of the X-ray source over the 0.5 - 4.5 keV energy range.

Soft_Spect_Index_Pos_Err
The positive 1-sigma uncertainty in Gamma_s.

Soft_Spect_Index_Neg_Err
The negative 1-sigma uncertainty in Gamma_s.

SB_Flux
The flux of the X-ray source in the 0.5 - 2 keV (soft) band, in cgs units of erg/s/cm^2.

SB_Flux_Error
The 1-sigma uncertainty in the flux of the X-ray source in the 0.5 - 2 keV (soft) band, in cgs units of erg/s/cm^2.

Hard_Spect_Index
The X-ray spectral photon index Gamma_h over either the 2 - 10 or 2 - 12 keV energy range (the CDS documentation is ambiguous about the upper energy limit).

Hard_Spect_Index_Pos_Err
The positive 1-sigma uncertainty in Gamma_h.

Hard_Spect_Index_Neg_Err
The negative 1-sigma uncertainty in Gamma_h.

HB_Flux
The flux of the X-ray source in the 2 - 10 keV (hard) band, in cgs units of erg/s/cm^2.

HB_Flux_Error
The 1-sigma uncertainty in the flux of the X-ray source in the 2 - 10 keV (hard) band, in cgs units of erg/s/cm^2.

Xid_Flux
The flux of the X-ray source in the 0.5 - 4.5 keV (XID) band, in cgs units of erg/s/cm^2.

Xid_Flux_Error
The 1-sigma uncertainty in the flux of the X-ray source in the 0.5 - 4.5 keV (XID) band, in cgs units of erg/s/cm^2.

UHB_Flux
The flux of the X-ray source in the 4.5 - 7.5 keV (ultrahard) band, in cgs units of erg/s/cm^2.

UHB_Flux_Error
The 1-sigma uncertainty in the flux of the X-ray source in the 4.5 - 7.5 keV (ultrahard) band, in cgs units of erg/s/cm^2.

Spect_Index
The X-ray spectral photon index Gamma of the X-ray source over either the 0.5 - 10 or 0.5 - 12 keV energy range (the CDS documentation is ambiguous about the upper energy limit).

Spect_Index_Pos_Err
The positive 1-sigma uncertainty in Gamma.

Spect_Index_Neg_Err
The negative 1-sigma uncertainty in Gamma.

Flux
The flux of the X-ray source in the 0.5 - 10 keV (total) band, in cgs units of erg/s/cm^2.

Flux_Error
The 1-sigma uncertainty in the flux of the X-ray source in the 0.5 - 10.0 keV (total) band, in cgs units of erg/s/cm^2.

SB_Flag
This parameter is a flag which indicates whether (1) or not (0) the X-ray source belongs to the soft sample.

HB_Flag
This parameter is a flag which indicates whether (1) or not (0) the X-ray source belongs to the hard sample.

Xid_Flag
This parameter is a flag which indicates whether (1) or not (0) the X-ray source belongs to the XID sample.

UHB_Flag
This parameter is a flag which indicates whether (1) or not (0) the X-ray source belongs to the ultrahard sample.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 14-Aug-2007