The discovery of seven extremely low surface brightness galaxies in the field of the nearby spiral galaxy M101

TL;DR

This study used a specialized telescope to discover seven ultra-diffuse, low surface brightness dwarf galaxy candidates near M101, revealing a population that standard surveys might miss, with properties similar to Local Group dwarfs.

Contribution

The paper reports the discovery of seven new low surface brightness dwarf galaxy candidates around M101 using the Dragonfly Telephoto Array, highlighting a potentially significant population missed by traditional surveys.

Findings

Seven low surface brightness galaxy candidates identified near M101.

Galaxies have effective radii of 350 pc to 1.3 kpc and very low Sersic indices.

Properties are similar to Local Group dwarf galaxies like Sextans I.

Abstract

Dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, which makes it difficult to identify and study them outside of the Local Group. We used a low surface brightness-optimized telescope, the Dragonfly Telephoto Array, to search for dwarf galaxies in the field of the massive spiral galaxy M101. We identify seven large, low surface brightness objects in this field, with effective radii of \(10 - 30\) arcseconds and central surface brightnesses of \(\mu_{g} \sim 25.5 - 27.5\) mag arcsec\(^{-2}\). Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Assuming the galaxies are dwarf satellites of M101, their absolute magnitudes are in the range \(-11.6 \lesssim M_{V} \lesssim -9.3\) and their effective radii are \(350\) pc \(-\) \(1.3\) kpc. Their radial surface brightness profiles are well fit by Sersic profiles with a very low Sersic index (\(n \sim 0.3 - 0.7\)). The properties of the sample are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix. Distance measurements are required to determine whether these galaxies are in fact associated with M101 or are in its foreground or background.