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 μm imaging isophotal study of 27 early-type galaxies. Core galaxies have reduced ellipticity and boxiness near and within their core or break radius. This supports a core formation mechanism that mixes or scatters stars such as scattering caused by a binary black hole. We find the same trends between central surface brightness and luminosities as the WPFC studies. 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.

Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of University for Research in Astronomy, Inc. (AURA), under NASA contract NAS5-26555.