A deep Chandra catalog of x-ray point sources toward the galactic center

M. P. Muno, F. K. Baganoff, M. W. Bautz, W. N. Brandt, P. S. Broos, E. D. Feigelson, G. P. Garmire, M. R. Morris, G. R. Ricker, L. K. Townsley

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186 Scopus citations


We present a catalog of 2357 point sources detected during 590 ks of Chandra observations of the 17′ × 17′ field around Sgr A*. This field encompasses a physical area of 40 × 40 pc at a distance of 8 kpc. The completeness limit of the sample at the Galactic center is 1031 ergs s-1 (2.0-8.0 keV), while the detection limit is an order of magnitude lower. The 281 sources detected below 1.5 keV are mainly in the foreground of the Galactic center, while comparisons to the Chandra deep fields at high Galactic latitudes suggest that only about 100 of the observed sources are background AGNs. The surface density of absorbed sources (not detected below 1.5 keV) falls off as 1/θ away from Sgr A*, in agreement with the distribution of stars in infrared surveys. This demonstrates the X-ray sources trace the general stellar population at the Galactic center. Point sources brighter than our completeness limit produce 10% of the flux previously attributed to diffuse emission. The log N-log S distribution of the Galactic center sources is extremely steep (power-law slope α = 1.7). If this distribution extends down to a flux of 10-17 ergs cm-2 s-1 (1029 ergs s-1 at 8 kpc, 2.0-8.0 keV) with the same slope, then point sources would account for all of the, previously reported diffuse emission. However, there are numerous diffuse, filamentary structures in the field that also contribute to the total flux, so the 2.0-8.0 keV luminosity distribution must flatten between 10 29 and 1031 ergs s-1. Many types of stellar systems should be present in the field at the luminosities to which we are sensitive. However, the spectra of more than half of the Galactic center sources are very hard and can be described by a power law (E ) with photon index Γ < 1. Such hard spectra have been seen previously only from magnetically accreting white dwarfs (polars and intermediate polars) and wind-accreting neutron stars (pulsars), suggesting that there are large numbers of these systems in our field.

Original languageEnglish (US)
Pages (from-to)225-241
Number of pages17
JournalAstrophysical Journal
Issue number1 I
StatePublished - May 20 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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