Dwarf galaxies in the Perseus Cluster: further evidence for a disc origin for dwarf ellipticals

TL;DR

This study uses spectroscopy to analyze dwarf elliptical galaxies in the Perseus Cluster, providing evidence that some dEs originate from disc galaxies transformed by tidal interactions, challenging the idea they are all primordial cluster members.

Contribution

It presents new spectroscopic data confirming cluster membership and proposes a disc origin for some dwarf ellipticals based on morphological and kinematic evidence.

Findings

Two new dwarf ellipticals confirmed as cluster members.

SA 0426-002 shows features indicative of a disc origin.

Evidence supports tidal harassment as a transformation mechanism.

Abstract

We present the results of a Keck-ESI spectroscopic study of six dwarf elliptical (dE) galaxies in the Perseus Cluster core, and confirm two dwarfs as cluster members for the first time. All six dEs follow the size-magnitude relation for dE/dSph galaxies. Central velocity dispersions are measured for three Perseus dwarfs in our sample, and all lie on the $\sigma$-luminosity relation for early-type, pressure supported systems. We furthermore examine SA 0426-002, a unique dE in our sample with a bar-like morphology surrounded by low-surface brightness wings/lobes ($\mu_{B} = 27$ mag arcsec$^{-2}$). Given its morphology, velocity dispersion ($\sigma_{0} = 33.9 \pm 6.1 $ km s$^{-1}$), velocity relative to the brightest cluster galaxy NGC 1275 (2711 km s$^{-1}$), size ($R_{e} =2.1 \pm 0.10$ kpc), and Sersic index ($n= 1.2 \pm 0.02$), we hypothesise the dwarf has morphologically transformed from a low mass disc to dE via harassment. The low-surface brightness lobes can be explained as a ring feature, with the bar formation triggered by tidal interactions via speed encounters with Perseus Cluster members. Alongside spiral structure found in dEs in Fornax and Virgo, SA 0426-002 provides crucial evidence that a fraction of bright dEs have a disc infall origin, and are not part of the primordial cluster population.