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Title: The Norma arm region Chandra survey catalog: X-ray populations in the spiral arms

We present a catalog of 1415 X-ray sources identified in the Norma Arm Region Chandra Survey (NARCS), which covers a 2° × 0.°8 region in the direction of the Norma spiral arm to a depth of ≈20 ks. Of these sources, 1130 are point-like sources detected with ≥3σ 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. We 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 our survey. We find that ∼50% of our 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. We argue that a mixture of magnetic and nonmagnetic cataclysmic variables dominates the Scutum-Crux and near Norma arms, while intermediate polars andmore » high-mass stars (isolated or in binaries) dominate the far Norma arm. We also present the cumulative number count distribution for sources in our 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} ≈ 10{sup –14} erg cm{sup –2} s{sup –1}, but the distribution curve flattens at fainter fluxes. We find good agreement between the observed distribution and predictions based on other surveys.« less
Authors:
 [1] ; ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720 (United States)
  2. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 (United States)
  3. Department of Physics, McGill University, Rutherford Physics Building, 3600 University Street, Montreal, QC H3A 2T8 (Canada)
  4. European Southern Observatory, Karl Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany)
  5. Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)
  6. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22 (Chile)
  7. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 169-506, Pasadena, CA 91109 (United States)
Publication Date:
OSTI Identifier:
22370148
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 796; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; CATALOGS; CLASSIFICATION; COSMIC X-RAY SOURCES; DISTRIBUTION; EMISSION; GALAXIES; GALAXY NUCLEI; HARD X RADIATION; KEV RANGE; MASS; MIXTURES; NOVAE; SPECTRA; X-RAY SOURCES