THE CHANDRA LOCAL VOLUME SURVEY: THE X-RAY POINT-SOURCE POPULATION OF NGC 404

Journal Article · Fri Feb 15 04:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/763/2/128· OSTI ID:22167126

Binder, B.; Williams, B. F.; Weisz, D. R. ^[1]; Eracleous, M. ^[2]; Gaetz, T. J. ^[3]; Kong, A. K. H. ^[4]; Skillman, E. D. ^[5]

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1. University of Washington, Department of Astronomy, Box 351580, Seattle, WA 98195 (United States)
2. Department of Astronomy and Astrophysics and Center for Gravitational Wave Physics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street Cambridge, MA 02138 (United States)
4. Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
5. University of Minnesota, Astronomy Department, 116 Church St. SE, Minneapolis, MN 55455 (United States)

We present a comprehensive X-ray point-source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new 97 ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of {approx}123 ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of {approx}6 Multiplication-Sign 10{sup 35} erg s{sup -1} in the 0.35-8 keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2 keV) and the hard band (2-8 keV) have a limiting luminosity at the 90% completeness limit of 10{sup 35} erg s{sup -1} and 10{sup 36} erg s{sup -1}, respectively, significantly lower than previous X-ray studies of NGC 404. We find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10{sup 37} erg s{sup -1}) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation {approx}0.5 Gyr ago.

• OSTI ID: 22167126
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 763; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
GALAXY NUCLEI
KEV RANGE
LUMINOSITY
MASS
POINT SOURCES
STARS
TELESCOPES
X RADIATION
X-RAY DETECTION
X-RAY GALAXIES
X-RAY SOURCES