Astrophys. J., 763, 128 (2013/February-1)
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. and WEISZ D.R.
Abstract (from CDS):
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 ∼6x1035 erg/s 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 and 1036 erg/s, 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) 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.
binaries: general - galaxies: individual: NGC 404 - surveys - X-rays: galaxies
VizieR on-line data:
<Available at CDS (J/ApJ/763/128): table3.dat table4.dat table5.dat table6.dat table10.dat table12.dat table13.dat>
Tables 3-6, 10, 13, Col(ID): CXOLV JHHMMSS.ss+DDMMSS.s N=74 = Tables 3-6, 10, 13, Col(Seq): [BWE2013] NGC 404 NN (Nos 1-74).
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