Chandra Observations of Diffuse Gas and Luminous X-ray Sources Around the X-ray Bright Elliptical NGC 1600

Abstract

(Abridged) We observed the X-ray bright E3 galaxy NGC 1600 and nearby group members with the Chandra X-ray Observatory ACIS S3. Unresolved emission dominates the observation; however, we resolved some emission into 71 sources, most of which are low-mass X-ray binaries (LMXBs) associated with NGC 1600. Twenty-one sources have L_X>2E39 ergs/s (0.3-10.0 keV; assuming they are at the distance of NGC 1600) marking them as ultraluminous X-ray point source (ULX) candidates; we expect only 11+/-2 are unrelated sources. 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 AGN cannot be ruled out. There are indications that there are also a large number of unresolved point sources. We propose that these are associated with globular clusters (GCs), and that NGC 1600 has a large GC specific frequency. The unresolved emission appears to have two gas components. We interpret the soft inner component (a<~25", kT~0.85 keV) as the interstellar medium of NGC 1600 and the hotter outer component (a>~25", kT~1.5 keV) as the intragroup medium of the NGC 1600 group. The X-ray image shows several interesting structures, excess emission roughly cospatial with H$α$ and dust filaments, possible holes in the X-ray emission roughly coincident with radio lobes, excess emission to the northeast possibly indicating the center of the group potential, and a tail of X-ray emission from the group galaxy NGC 1603 probably due to ram-pressure stripping