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NormaArmRegionChandraSurveyPoint&ExtendedSourceCatalog

Metadata Updated: September 19, 2025

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 .

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Dates

Metadata Created Date April 11, 2025
Metadata Updated Date September 19, 2025

Metadata Source

Harvested from NASA Data.json

Additional Metadata

Resource Type Dataset
Metadata Created Date April 11, 2025
Metadata Updated Date September 19, 2025
Publisher High Energy Astrophysics Science Archive Research Center
Maintainer
Identifier ivo://nasa.heasarc/narcscat
Data Last Modified 2025-09-10
Category Astrophysics
Public Access Level public
Bureau Code 026:00
Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
Schema Version https://project-open-data.cio.gov/v1.1/schema
Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
Harvest Object Id 6205ead6-bda4-4bd4-8f19-7c399caba4b8
Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
Harvest Source Title NASA Data.json
Homepage URL https://heasarc.gsfc.nasa.gov/W3Browse/all/narcscat.html
Program Code 026:000
Source Datajson Identifier True
Source Hash 8c32485be77dacf25dbfbc8efb24da60d04bc2a8ff3c82c263e7bb3e30173dc0
Source Schema Version 1.1

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