AXIS ivo://nasa.heasarc/axis NASA/GSFC HEASARC Carrera et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source 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<sup>-14</sup> 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. This table was created by the HEASARC in August 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/469/27">CDS catalog J/A+A/469/27</a> file table23.dat. This is a service provided by NASA HEASARC . 2007A&A...469...27C https://heasarc.gsfc.nasa.gov/W3Browse/all/axis.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=axis& GET text/xml 180 99999 true 0.10222 -25.349192 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=axis GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_axis&Action=More+Options&Action=Parameter+Search&ConeAdd=1 XMM-NEWTON 0.0166666666666667 X-ray public axis AXIS XMM-Newton Source Catalog name Source Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable xid_count_rate Count Rate in 0.5-4.5 keV Band ct/s phot.count;em.X-ray double nullable xid_count_rate_error Uncertainty in that band ct/s stat.error;phot.count;em.X-ray double nullable spect_index Photon Index in 0.5-12 keV spect.index;em.X-ray double nullable spect_index_neg_err Lower 1-Sigma Uncertainty on Photon Index in 0.5-12 keV stat.error;spect.index;em.X-ray double nullable spect_index_pos_err Upper 1-Sigma Uncertainty on Photon Index in 0.5-12 keV stat.error;spect.index;em.X-ray double nullable flux Flux in the 0.5-10 keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable flux_error 1-Sigma Uncertainty on Flux in the 0.5-10 keV Band erg/s/cm^2 stat.error;phot.flux;em.X-ray double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable sb2_detect_likelihood Likelihood of Detection in that Band stat.likelihood;phot.count;em.X-ray.soft double nullable hard_spect_index_pos_err Upper 1-Sigma Uncertainty on Photon Index in 2-12 keV Band stat.error;spect.index;em.X-ray double nullable uhb_flag Flag for the UH Sample meta.code short nullable sb_flux Flux in the 0.5-2 keV Band (Soft) erg/s/cm^2 phot.flux;em.X-ray.soft double nullable hb_flux Flux in the 2-10 keV Band (Hard) erg/s/cm^2 phot.flux;em.X-ray.medium double nullable sb4_count_rate Count Rate in 4.5-7.5 keV Band ct/s phot.count;em.X-ray.medium double nullable lii Galactic Longitude degree pos.galactic.lon double nullable sb4_count_rate_error Uncertainty in that Band ct/s stat.error;phot.count;em.X-ray.medium double nullable soft_spect_index_neg_err Lower 1-Sigma Uncertainty on Photon Index in 0.5-4.5 keV Band stat.error;spect.index;em.X-ray double nullable sb3_count_rate_error Uncertainty in that Band ct/s stat.error;phot.count;em.X-ray.medium double nullable uhb_flux_error 1-Sigma Uncertainty on Flux in the 4.5-7.5 keV Band (UH) erg/s/cm^2 stat.error;phot.flux;em.X-ray.medium double nullable sb3_detect_likelihood Likelihood of Detection in that Band stat.likelihood;phot.count;em.X-ray.medium double nullable sb2_count_rate Count Rate in 0.5-2 keV Band ct/s phot.count;em.X-ray.soft double nullable sb4_detect_likelihood Likelihood of Detection in that Band stat.likelihood;phot.count;em.X-ray.medium double nullable soft_spect_index Photon Index in 0.5-4.5 keV Band spect.index;em.X-ray double nullable hard_spect_index Photon Index in 2-12 keV Band spect.index;em.X-ray double nullable uhb_flux Flux in the 4.5-7.5 keV Band (UH) erg/s/cm^2 phot.flux;em.X-ray.medium double nullable bii Galactic Latitude degree pos.galactic.lat double nullable hb_flux_error 1-Sigma Uncertainty on Flux in the 2-10 keV Band (Hard) erg/s/cm^2 stat.error;phot.flux;em.X-ray.medium double nullable soft_spect_index_pos_err Upper 1-Sigma Uncertainty on Photon Index in 0.5-4.5 keV Band stat.error;spect.index;em.X-ray double nullable xid_flux Flux in the 0.5-4.5 keV Band (XID) erg/s/cm^2 phot.flux;em.X-ray double nullable sb3_count_rate Count Rate in 2-4.5 keV Band ct/s phot.count;em.X-ray.medium double nullable sb_flux_error 1-Sigma Uncertainty on Flux in the 0.5-2 keV Band (Soft) erg/s/cm^2 stat.error;phot.flux;em.X-ray.soft double nullable xid_detect_likelihood Likelihood of Detection in that Band stat.likelihood;phot.count;em.X-ray double nullable sb_flag Flag for the Soft Sample meta.code short nullable sb5_count_rate Count Rate in 7.5-12 keV Band ct/s phot.count;em.X-ray.medium double nullable sb2_count_rate_error Uncertainty in that Band ct/s stat.error;phot.count;em.X-ray.soft double nullable hb_flag Flag for the Hard Sample meta.code short nullable sb5_detect_likelihood Likelihood of Detection in that Band stat.likelihood;phot.count;em.X-ray.medium double nullable error_radius 90% Uncertainty Radius in Position (arcsec) arcsec stat.error;pos double nullable hard_spect_index_neg_err Lower 1-Sigma Uncertainty on Photon Index in 2-12 keV Band stat.error;spect.index;em.X-ray double nullable xid_flux_error 1-Sigma Uncertainty on Flux in the 0.5-4.5 keV Band (XID) erg/s/cm^2 double nullable xid_flag Flag for the XID Sample meta.code short nullable sb5_count_rate_error Uncertainty in that Band ct/s stat.error;phot.count;em.X-ray.medium double nullable