The MASSIVE Survey IX: Photometric Analysis of 35 High Mass Early-Type Galaxies with HST WFC3/IR

TL;DR

This study uses HST WFC3/IR imaging to analyze the surface brightness and isophotal shapes of 35 high-mass early-type galaxies, revealing complex structures and formation histories.

Contribution

First near-infrared high-resolution survey of massive early-type galaxies, providing detailed isophotal analysis and insights into their structural complexity.

Findings

37% of galaxies show significant isophotal PA rotations

Most galaxies are rounder at the center than outer regions

Presence of both disky and boxy isophotes with radius

Abstract

We present near-infrared observations of 35 of the most massive early-type galaxies in the local universe. The observations were made using the infrared channel of the Hubble Space Telescope Wide Field Camera 3 in the F110W (1.1 $\mu$m) filter. We measured surface brightness profiles and elliptical isophotal fit parameters from the nuclear regions out to a radius of ~10 kpc in most cases. We find that 37% (13) of the galaxies in our sample have isophotal position angle rotations greater than 20 degrees over the radial range imaged by WFC3/IR, which is often due to the presence of neighbors or multiple nuclei. Most galaxies in our sample are significantly rounder near the center than in the outer regions. This sample contains six fast rotators and 28 slow rotators. We find that all fast rotators are either disky or show no measurable deviation from purely elliptical isophotes. Among slow rotators, significantly disky and boxy galaxies occur with nearly equal frequency. The galaxies in our sample often exhibit changing isophotal shapes, sometimes showing both significantly disky and boxy isophotes at different radii. The fact that parameters vary widely between galaxies and within individual galaxies is evidence that these massive galaxies have complicated formation histories, and some of them have experienced recent mergers and have not fully relaxed. These data demonstrate the value of high spatial resolution IR imaging of galaxies and provide measurements necessary for determining stellar masses, dynamics, and black hole masses in high mass galaxies.