Hubble Space Telescope survey of the Perseus Cluster - I: The structure and dark matter content of cluster dwarf spheroidals

TL;DR

This study uses Hubble Space Telescope data to analyze dwarf galaxies in the Perseus Cluster, revealing their structure, dark matter content, and proposing a new method to estimate dark matter without kinematic data.

Contribution

Introduces a novel, kinematics-independent method to measure dark matter in dwarf ellipticals based on their size, position, and cluster mass.

Findings

Dwarfs are smooth and lack internal features.

Dark matter content is significant, with mass-to-light ratios up to 120.

Dwarfs' dark matter ratios are similar to Local Group dSphs.

Abstract

We present the results of a Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) study of dwarf galaxies in the core of the rich nearby Perseus Cluster, down to M_V=-12. We identify 29 dwarfs as cluster members, 17 of which are previously unstudied. All the dwarfs we examine are remarkably smooth in appearance, and lack internal features. Based on these observations, and the sizes of these dwarfs, we argue that some of the dwarfs in our sample must have a large dark matter content to prevent disruption by the cluster potential. We derive a new method, independent of kinematics, for measuring the dark matter content of dEs, based on the radius of the dwarf, the projected distance of the dwarf from the cluster centre, and the total mass of the cluster interior to it. We find that the mass-to-light ratios of these dwarfs are comparable to those of the Local Group dSphs, ranging between 1 and 120.