G515, Revisited. I. Stellar Populations and Evidence of Nuclear Activity in A Luminous “E+A” Galaxy

Abstract

We present multiwavelength observations of the very luminous ``E+A'' galaxy known as G515 (J152426.50+080908.0), including deep Ks imaging, spatially resolved Hα spectroscopy, and radio observations. The data, together with detailed spectral synthesis of the galaxy's integrated stellar population, show that G515 is a ~1 Gyr old postmerger, poststarburst galaxy. We detect no Balmer line emission in the galaxy, although there is a small amount of [N II] λλ6548, 6583 Å emission. The galaxy's H I mass has a 2 σ upper limit of 1.0×109 Msolar. IRAS detections in the 60 and 100 μm bands indicate a far-infrared luminosity of ~5.8×1010 Lsolar. A small amount (~3 mJy) of radio continuum flux, which appears to be variable, has been detected. The data suggest that G515 may have once been an ultraluminous infrared galaxy, and may harbor a weak, dust-obscured active nucleus. Based on data collected at The Arecibo Observatory, part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation (NSF); Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the NSF; The MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona; and Steward Observatory, operated by the University of Arizona.