The Distance to the Galaxy Coma P

TL;DR

This study determines the distance to galaxy Coma P as approximately 10.9 Mpc, resolving previous discrepancies and showing its velocity aligns with models of Virgo Cluster infall, with a dominant young stellar population.

Contribution

The paper provides a new distance measurement to Coma P using HST data, clarifying its velocity and position relative to the Virgo Cluster, and characterizes its stellar population.

Findings

Distance to Coma P is about 10.9 Mpc.

Galaxy's velocity is consistent with Virgo Cluster infall.

Dominant stellar population is a few Gyr old.

Abstract

If the extremely low surface brightness galaxy Coma P lies at $5.5\pm0.3$ Mpc as recently proposed then it would have an extraordinarily deviant peculiar velocity of $\sim900$ km $\mathrm{s^{-1}}$ at a location where differential velocities between galaxies are low. We have accessed the images from the HST archives used to derive the literature distance from the magnitude of the tip of the red giant branch. Our analysis gives the distance to be $10.9\pm1.0$ Mpc. At this location the galaxy lies within the infall region of the Virgo Cluster, such that its still considerable peculiar velocity of $\sim500$ km $\mathrm{s^{-1}}$ is consistent with an established model. Coma P has an unusually pronounced asymptotic giant branch relative to its red giant branch. The dominant stellar population is just a few Gyr old.