The chandra local volume survey: The X-ray point-source population of NGC 404

B. Binder, B. F. Williams, M. Eracleous, T. J. Gaetz, A. K H Kong, E. D. Skillman, D. R. Weisz

Research output: Contribution to journalArticle

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Abstract

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 ∼123 ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ∼6 × 1035 erg s-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 1035 erg s-1 and 1036 erg s-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 (>1037 erg s-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 ∼0.5 Gyr ago.

Original languageEnglish (US)
Article number128
JournalAstrophysical Journal
Volume763
Issue number2
DOIs
StatePublished - Feb 1 2013

Fingerprint

point sources
point source
x rays
erg
luminosity
completeness
stellar mass
Hubble Space Telescope
active galactic nuclei
cross correlation
catalogs
energy bands
star formation
time measurement

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Binder, B., Williams, B. F., Eracleous, M., Gaetz, T. J., Kong, A. K. H., Skillman, E. D., & Weisz, D. R. (2013). The chandra local volume survey: The X-ray point-source population of NGC 404. Astrophysical Journal, 763(2), [128]. https://doi.org/10.1088/0004-637X/763/2/128
Binder, B. ; Williams, B. F. ; Eracleous, M. ; Gaetz, T. J. ; Kong, A. K H ; Skillman, E. D. ; Weisz, D. R. / The chandra local volume survey : The X-ray point-source population of NGC 404. In: Astrophysical Journal. 2013 ; Vol. 763, No. 2.
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Binder, B, Williams, BF, Eracleous, M, Gaetz, TJ, Kong, AKH, Skillman, ED & Weisz, DR 2013, 'The chandra local volume survey: The X-ray point-source population of NGC 404', Astrophysical Journal, vol. 763, no. 2, 128. https://doi.org/10.1088/0004-637X/763/2/128

The chandra local volume survey : The X-ray point-source population of NGC 404. / Binder, B.; Williams, B. F.; Eracleous, M.; Gaetz, T. J.; Kong, A. K H; Skillman, E. D.; Weisz, D. R.

In: Astrophysical Journal, Vol. 763, No. 2, 128, 01.02.2013.

Research output: Contribution to journalArticle

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AB - 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 ∼123 ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ∼6 × 1035 erg s-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 1035 erg s-1 and 1036 erg s-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 (>1037 erg s-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 ∼0.5 Gyr ago.

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