A NICMOS Survey of Early-Type Galaxy Centers: The Relation Between Core Properties, Gas and Dust Content and Environment

Abstract

We present a NICMOS 1.6 micron imaging isophotal study of 27 early-type galaxies. Our selected sample is not as biased against dusty galaxies as the visible WFPC samples observed with HST. Core galaxies have reduced ellipticity and boxiness near and within their core or break radius. This supports a core formation mechanism which mixes or scatters stars such as scattering caused by a binary black hole. We find no correlation between core properties and dust mass or X-ray luminosity, suggesting that processes determining the current gas content (e.g., such as minor mergers and cooling flows) are unrelated to processes occurring during core formation. Core galaxies exist in a variety of environments ranging from poor groups to large clusters. A combined sample suggests that galaxy groups may harbor more luminous power law galaxies than clusters such as Virgo and Fornax.