Spatially Resolved Properties of the GW170817 Host Galaxy

Abstract

Abstract GW170817 is the unique gravitational-wave (GW) event associated with the electromagnetic (EM) counterpart GRB 170 817A. NGC 4993 is identified as the host galaxy of GW170817/GRB 170 817A. In this paper, we focus on the spatially resolved properties of NGC 4993. We present the photometric results from the comprehensive data analysis of the high spatial-resolution images in the different optical bands. The morphological analysis reveals that NGC 4993 is a typical early-type galaxy without significant remnants of a major galaxy merger. The spatially resolved stellar population properties of NGC 4993 suggest that the galaxy center has passive evolution with the outskirt formed by gas accretion. We derive the merging rate of the compact object per galaxy by a co-evolution scenario of a supermassive black hole and its host galaxy. If the galaxy formation is at redshift 1.0, the merging rate per galaxy is from 3.2 × 10−4 to 7.7 × 10−5 within the merging decay time from 1.0 to 5.0 Gyr. The results provide vital information for ongoing GW EM counterpart detections. The Hubble space telescope data analysis presented in this paper can be also applied to Chinese Space Station Telescope research in the future.