NARCSCAT ivo://nasa.heasarc/narcscat NASA/GSFC HEASARC Fornasini et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source This table contains the catalog of 1,415 X-ray sources identified in the Norma Arm Region Chandra Survey (NARCS), which covers a 2 degree x 0.8 degree region in the direction of the Norma spiral arm to a depth of ~ 20 ks. Of these sources, 1,130 are point-like sources detected with >= 3-sigma confidence in at least one of three energy bands (0.5 - 10, 0.5 - 2, and 2 - 10 keV), five have extended emission, and the remainder are detected at low significance. Since most sources have too few counts to permit individual classification, they are divided into five spectral groups defined by their quantile properties. The authors analyze stacked spectra of X-ray sources within each group, in conjunction with their fluxes, variability, and infrared counterparts, to identify the dominant populations in this survey. They find that ~ 50% of their sources are foreground sources located within 1 - 2 kpc, which is consistent with expectations from previous surveys. Approximately 20% of sources are likely located in the proximity of the Scutum-Crux and near Norma arm, while 30% are more distant, in the proximity of the far Norma arm or beyond. The authors argue that a mixture of magnetic and non-magnetic cataclysmic variables dominates the Scutum-Crux and near Norma arms, while intermediate polars and high-mass stars (isolated or in binaries) dominate the far Norma arm. In the paper, they also present the cumulative number count distribution for sources in this survey that are detected in the hard energy band. A population of very hard sources in the vicinity of the far Norma arm and active galactic nuclei dominate the hard X-ray emission down to f<sub>X</sub> ~ 10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup>, but the distribution curve flattens at fainter fluxes. The authors find good agreement between the observed distribution and predictions based on other surveys. Chandra ACIS-I observations were performed in faint mode of a 2 degree by 0.8 degree region of the Norma spiral arm in 2011 June. This field was subdivided into 27 pointings; Table 1 in the reference paper reports their coordinates and exposure times and Figure 1 (op. cit.) is a mosaic image of the survey. The observing strategy was to cover a wide area with relatively uniform flux sensitivity and good spatial resolution; therefore, the authors chose field centers spaced by 12 arcminutes, which provided roughly 70 arcminute<sup>2</sup> of overlap on the outskirts of adjacent observations such that the additional exposure time in these overlapping regions partly made up for the worsening point-spread function (PSF) at large off-axis angles. This table was created by the HEASARC in March 2015 based on electronic versions of Tables 3, 4 and 5 from the reference paper which were obtained from the ApJ web site. This is a service provided by NASA HEASARC . 2014ApJ...796..105F https://heasarc.gsfc.nasa.gov/W3Browse/all/narcscat.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=narcscat& GET text/xml 180 99999 true 248.853694 -48.041948 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=narcscat GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_narcscat&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 Infrared X-ray public narcscat Norma Arm Region Chandra Survey Point & Extended Source Catalog source_number Sequential Identification Number for Each Source in Catalog meta.id;src short nullable name Chandra 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 error_radius Positional Uncertainty arcsec stat.error;pos double nullable fb_counts_limit Limit Flag for Net Full 0.5-10 keV Band Source Counts meta.code;phot;em.X-ray char nullable fb_counts Net Full 0.5-10 keV Band Source Counts ct phot;em.X-ray int nullable fb_counts_neg_err Lower 1-Sigma Error for Net Full 0.5-10 keV Band Source Counts ct stat.error;phot;em.X-ray short nullable fb_counts_pos_err Upper 1-Sigma Error for Net Full 0.5-10 keV Band Source Counts ct stat.error;phot;em.X-ray short nullable fb_flux_limit Limit Flag for Full 0.5-10 keV Band Flux meta.code;phot.flux;em.X-ray char nullable fb_flux Full 0.5-10 keV Band Flux erg/s/cm^2 phot.flux;em.X-ray double nullable xray_ir_offset Angular Separation Between Chandra and VVV Source arcsec pos.angDistance;em.X-ray;em.IR 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 lii Galactic Longitude degree pos.galactic.lon double nullable obsid_1 Chandra Observation Identifier 1 meta.id;obs int nullable psf_radius_1 Point Spread Function for ObsID 1 arcsec instr.det.psf double nullable obsid_2 Chandra Observation Identifier 2 meta.id;obs int nullable source_flags_3 Source Flags for ObsID 3 meta.code;src char nullable psf_radius_3 Point Spread Function for ObsID 3 arcsec instr.det.psf double nullable sb_photon_flux Soft 0.5-2 keV Band Photon Flux photon/cm^2/s phot.flux;em.X-ray.soft double nullable off_axis_3 Offset Angular Separation of Source and Aim Point of ObsID 3 arcmin instr.offset double nullable fb_photon_flux Full 0.5-10 keV Band Photon Flux photon/cm^2/s phot.flux;em.X-ray double nullable hb_significance Hard 2-10 keV Band Significance stat.likelihood;em.X-ray.medium double nullable obsid_3 Chandra Observation Identifier 3 meta.id;obs int nullable q75_energy_error The 1-Sigma Error for Energy Below Which 75% of Total Source Counts Reside keV stat.error;phys.energy double nullable photometric_flags Photometric Flags [FSH] char nullable sb_photon_flux_neg_err Lower 1-Sigma Error for Soft 0.5-2 keV Band Photon Flux photon/cm^2/s stat.error;phot.flux;em.X-ray.soft double nullable bii Galactic Latitude degree pos.galactic.lat double nullable q25_energy Energy Below Which 25% of Total Source Counts Reside keV phys.energy double nullable hb_photon_flux_pos_err Upper 1-Sigma Error for Hard 2-10 keV Band Photon Flux photon/cm^2/s stat.error;phot.flux;em.X-ray.medium double nullable hb_counts_limit Limit Flag for Net Hard 2-10 keV Band Source Counts meta.code;phot;em.X-ray.medium char nullable sb_significance Soft 0.5-2 keV Band Significance stat.likelihood;em.X-ray.soft double nullable sb_counts_limit Limit Flag for Net Soft 0.5-2 keV Band Source Counts meta.code;phot;em.X-ray.soft char nullable hb_photon_flux Hard 2-10 keV Band Photon Flux photon/cm^2/s phot.flux;em.X-ray.medium double nullable hb_counts Net Hard 2-10 keV Band Source Counts ct phot;em.X-ray.medium int nullable fb_photon_flux_neg_err Lower 1-Sigma Error for Full 0.5-10 keV Band Photon Flux photon/cm^2/s stat.error;phot.flux;em.X-ray double nullable fb_photon_flux_pos_err Upper 1-Sigma Error for Full 0.5-10 keV Band Photon Flux photon/cm^2/s stat.error;phot.flux;em.X-ray double nullable off_axis_1 Offset Angular Separation of Source and Aim Point of ObsID 1 arcmin instr.offset double nullable source_flags_2 Source Flags for ObsID 2 meta.code;src char nullable median_energy Median Source Energy keV phys.energy double nullable fb_flux_neg_err Lower 1-Sigma Error for Full 0.5-10 keV Band Flux erg/s/cm^2 stat.error;phot.flux;em.X-ray double nullable ir_ra Right Ascension of Infrared Source degree pos.eq.ra;em.IR double nullable extraction_radius_2 Radius of Aperture Source Region of ObsID 2 arcsec phys.angSize;instr.det double nullable q75_energy Energy Below Which 75% of Total Source Counts Reside keV phys.energy double nullable hb_photon_flux_neg_err Lower 1-Sigma Error for Hard 2-10 keV Band Photon Flux photon/cm^2/s stat.error;phot.flux;em.X-ray.medium double nullable sb_photon_flux_pos_err Upper 1-Sigma Error for Soft 0.5-2 keV Band Photon Flux photon/cm^2/s stat.error;phot.flux;em.X-ray.soft double nullable ir_match_reliability Reliability That VVV Source Matches Chandra Source stat.probability;src;em.IR double nullable median_energy_error The 1-Sigma Error for Median Source Energy keV stat.error;phys.energy double nullable extraction_radius_3 Radius of Aperture Source Region of ObsID 3 arcsec phys.angSize;instr.det double nullable fb_flux_pos_err Upper 1-Sigma Error for Full 0.5-10 keV Band Flux erg/s/cm^2 stat.error;phot.flux;em.X-ray double nullable source_flags_1 Source Flags for ObsID 1 meta.code;src char nullable sb_counts_pos_err Upper 1-Sigma Error for Net Soft 0.5-2 keV Band Source Counts ct stat.error;phot;em.X-ray.soft short nullable psf_radius_2 Point Spread Function for ObsID 2 arcsec instr.det.psf double nullable sb_counts Net Soft 0.5-2 keV Band Source Counts ct phot;em.X-ray.soft short nullable q25_energy_error The 1-Sigma Error for Energy Below Which 25% of Total Source Counts Reside keV stat.error;phys.energy double nullable off_axis_2 Offset Angular Separation of Source and Aim Point of ObsID 2 arcmin instr.offset double nullable fb_significance Full 0.5-10 keV Band Significance stat.likelihood;em.X-ray double nullable sb_photon_flux_limit Limit Flag for Soft 0.5-2 keV Band Photon Flux meta.code;phot.flux;em.X-ray.soft char nullable ir_noise_probability Probability That VVV Source Is a Noise Fluctuation stat.probability;em.IR double nullable quantile_group Quantile Group [ABCDE] meta.code;stat.param char nullable fb_photon_flux_limit Limit Flag for Full 0.5-10 keV Band Photon Flux meta.code;phot.flux;em.X-ray char nullable sb_counts_neg_err Lower 1-Sigma Error for Net Soft 0.5-2 keV Band Source Counts ct stat.error;phot;em.X-ray.soft short nullable hb_counts_pos_err Upper 1-Sigma Error for Net Hard 2-10 keV Band Source Counts ct stat.error;phot;em.X-ray.medium short nullable ir_dec Declination of Infrared Source degree pos.eq.dec;em.IR double nullable extraction_radius_1 Radius of Aperture Source Region of ObsID 1 arcsec phys.angSize;instr.det double nullable hb_counts_neg_err Lower 1-Sigma Error for Net Hard 2-10 keV Band Source Counts ct stat.error;phot;em.X-ray.medium short nullable hb_photon_flux_limit Limit Flag for Hard 2-10 keV Band Photon Flux meta.code;phot.flux;em.X-ray.medium char nullable vvv_source VVV Source Identifier, If Available meta.id.cross char nullable