NGC 1600 Chandra X-Ray Discrete Source Catalog

NGC 1600 Chandra X-Ray Discrete Source Catalog NGC1600CXO ivo://nasa.heasarc/ngc1600cxo NASA/GSFC HEASARC Sivakoff et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The authors observed the X-ray-bright E3 galaxy NGC 1600 and nearby members of the NGC 1600 group with the Chandra X-Ray Observatory ACIS-S3 to study their X-ray properties. NGC 1600 is the brightest member of the NGC 1600 group; NGC 1601 (1.6 arcminutes away) and NGC 1603 (2.5 arcminutes away) are the two nearest galaxies, both of which are non-interacting members. The authors adopted the 2MASS Point Source Catalog position of J2000.0 RA = 04h 31m 39.87s, Dec = -05o 05' 10.5" as the location of the center of the NGC 1600 galaxy. Unresolved emission dominates the Chandra observation; however, some of the emission is resolved into 71 sources, most of which are low-mass X-ray binaries associated with NGC 1600. Twenty-one of the sources have LX > 2 x 1039 ergs/s (0.3-10.0 keV; assuming they are at the distance of NGC 1600 of 59.98 Mpc), marking them as ultraluminous X-ray point source (ULX) candidates. NGC 1600 may have the largest number of ULX candidates in an early-type galaxy to date; however, cosmic variance in the number of background active galactic nuclei cannot be ruled out. The spectrum and luminosity function (LF) of the resolved sources are more consistent with sources found in other early-type galaxies than with sources found in star-forming regions of galaxies. The source LF and the spectrum of the unresolved emission both indicate that there are a large number of unresolved point sources. The authors propose that these sources are associated with globular clusters (GCs) and that NGC 1600 has a large GC specific frequency. Observations of the GC population in NGC 1600 would be very useful for testing this prediction. NGC 1600 was observed in two intervals on 2002 September 18-19 (ObsID 4283) and 2002 September 20 (ObsID 4371) with live exposures of 26,783 and 26,752 s, respectively. The first observation showed clear evidence of a major background "flare" in the first 20% of the observation. The second observation had some small fluctuations greater than 20% from the mean rate. After these were filtered, observations 4283 and 4371 had flare-free exposure times of 21,562 and 23,616 s, respectively. This table lists all 71 discrete sources detected by wavdetect over the 0.3-6 keV energy range in the combination of the two observations. The first 3 sources (source numbers 1, 2 and 3) are clearly extended according to the authors. The authors expect 11 +/- 2 foreground/background sources to be present based on the source counts in Brandt et al. (2000, AJ, 119, 2349) and Mushotzky et al. (2000, Nature, 404, 459). The authors determined the observed X-ray hardness ratios for the sources, using the same techniques that they have used previously. They define three hardness ratios as H21 = (M-S)/(M+S), H31 = (H-S)/(H+S), and H32 = (H-M)/(H+M), where S,M, and H are the total counts in the soft (0.3-1 keV), medium (1-2 keV) and hard (2-6 keV) respectively. From their previous definitions, they have reduced the hard band from 2-10 to 2-6 keV: since the 6-10 keV range is dominated by background photons for most sources, this should increase the S/N of the hardness ratio techniques. The hardness ratios measure observed counts, which are affected by Galactic absorption and quantum efficiency (QE) degradation in the Chandra ACIS detectors. In order to compare with other galaxies, it is useful to correct the hardness ratios for these two soft X-ray absorption effects. Therefore, the authors have calculated the intrinsic hardness ratios, denoted by a superscript 0, using a correction factor in each band appropriate to the best-fit spectrum of the resolved sources, and these are what are quoted in this table. This table was created by the HEASARC in May 2018 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/617/262/">CDS Catalog J/ApJ/617/262/</a> file table1.dat, the list of detected discrete X-ray sources in the Chandra observation of the NGC 1600 group. This is a service provided by NASA HEASARC . 2004ApJ...617..262S https://heasarc.gsfc.nasa.gov/W3Browse/all/ngc1600cxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=ngc1600cxo& GET text/xml 180 99999 true 67.865625 -5.1725 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=ngc1600cxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_ngc1600cxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public ngc1600cxo NGC 1600 Chandra X-Ray Discrete Source Catalog source_number Sequential Identification Number for Each Source in the Catalog meta.id;src short nullable name Source Designation (CXOU JHHMMSS.S+DDMMSS) meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable count_rate Wavdetect Count Rate ct/s phot.count;em.X-ray double nullable count_rate_error Error in Count Rate ct/s stat.error;phot.count;em.X-ray double nullable lx X-Ray Luminosity erg/s phys.luminosity;em.X-ray double nullable radial_distance Projected Radial Distance from the Center of NGC 1600 arcmin pos.angDistance double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable hardness_ratio21_pos_err Upper Error Limit on HR210 stat.error;phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio31 Intrinsic Hardness Ratio HR31 phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio21 Intrinsic Hardness Ratio HR21 phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio31_pos_err Upper Error Limit on HR310 stat.error;phot.flux;arith.ratio;em.X-ray double nullable lii Galactic Longitude degree pos.galactic.lon double nullable hardness_ratio31_neg_err Lower Error Limit on HR310 stat.error;phot.flux;arith.ratio;em.X-ray double nullable semi_major_distance Semi-Major Distance from the Center of NGC 1600 arcmin pos.angDistance double nullable hardness_ratio32 Intrinsic Hardness Ratio HR32 phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio21_neg_err Lower Error Limit on HR210 stat.error;phot.flux;arith.ratio;em.X-ray double nullable bii Galactic Latitude degree pos.galactic.lat double nullable hardness_ratio32_pos_err Upper Limit Error on HR320 stat.error;phot.flux;arith.ratio;em.X-ray double nullable snr Signal-to-Noise Ratio for the Count Rate stat.snr double nullable hardness_ratio32_neg_err Lower Limit Error on HR320 stat.error;phot.flux;arith.ratio;em.X-ray double nullable source_flags Flag(s) Indicate Comment(s) Concerning Source meta.code;src char nullable