2004ApJ...601..798C

We have detected an X-ray absorption feature against the core of the galaxy cluster A2029 (z=0.0767) that we identify with the foreground galaxy UZC J151054.6+054313 (z=0.0221). Optical observations (B, V, R, and I) indicate that it is an Scd galaxy seen nearly edge-on at an inclination of 87°±3°. H I observations give a rotation velocity of 108 km/s and an atomic hydrogen mass of M_HI_=3.1x109^d2^₉₀ M_☉, where d₉₀is the distance to the galaxy in units of 90 Mpc. X-ray spectral fits to the Chandra absorption feature yield a hydrogen column density of (2.0±0.4)x10²¹/cm2, assuming solar abundances. If the absorber is uniformly distributed over the disk of the galaxy, the implied hydrogen mass is M_H=(6.2±1.2)x10⁸d²₉₀M_☉. Since the absorbing gas in the galaxy is probably concentrated toward the center of the galaxy and the middle of the disk, this is a lower limit to the total hydrogen mass. On the other hand, the absorption measurements imply that the dark matter in UZC J151054.6+054313 is not distributed in a relatively uniform diffuse gas.