Hunting Faint Dwarf Galaxies in the Field Using Integrated Light Surveys

TL;DR

This paper proposes a method using integrated light surveys to detect faint dwarf galaxies in the Local Volume, demonstrating that such surveys can find galaxies down to stellar masses of about 10^4 solar masses at distances up to 10 Mpc.

Contribution

It introduces a new approach combining surface brightness and spatial resolution parameters to effectively identify faint dwarf galaxies in the field, supplementing traditional star counts.

Findings

Integrated light surveys can detect galaxies with stellar masses as low as 10^4 M_sun.

Detection efficiency depends mainly on surface brightness at distances over 3 Mpc.

Expected galaxy counts range from 0.04 to 0.35 per square degree between 3 and 10 Mpc.

Abstract

We discuss the approach of searching low mass dwarf galaxies, $\lesssim10^6\textrm{ M}_{\odot}$, in the general field, using integrated light surveys. By exploring the limiting surface brightness-spatial resolution ($\mu_{\textrm{eff,lim}}-\theta$) parameter space, we suggest that faint field dwarfs in the Local Volume, between $3$ and $10 \textrm{ Mpc}$, are expected to be detected effectively and in large numbers using integrated light photometric surveys, complementary to the classical star counts method. We use a sample of Local Group dwarf galaxies to construct relations between their photometric and structural parameters, $\textrm{M}_{*}$-$\mu_{\textrm{eff,V}}$ and $\textrm{M}_{*}$-$\textrm{R}_{\textrm{eff}}$. We use these relations, along with assumed functional forms for the halo mass function and the stellar mass-halo mass relation, to calculate the lowest detectable stellar masses in the Local Volume and the expected number of galaxies as a function of the limiting surface brightness and spatial resolution. The number of detected galaxies depends mostly on the limiting surface brightness for distances $>3\textrm{ Mpc}$ while spatial resolution starts to play a role at distances $>8\textrm{ Mpc}$. Surveys with $\mu_{\textrm{eff,lim}}\sim30\textrm{ mag arcsec}^{-2}$ should be able to detect galaxies with stellar masses down to $\sim10^4 \textrm{ M}_{\odot}$ in the Local Volume. Depending on the assumed stellar mass-halo mass relation, the expected number of galaxies between $3$ and $10\textrm{ Mpc}$ is $0.04-0.35\textrm{ deg}^{-2}$, assuming a limiting surface brightness of $\sim29-30\textrm{ mag arcsec}^{-2}$ and a spatial resolution $<4''$. We currently look for field dwarf galaxies by performing a blank wide-field survey with the Dragonfly Telephoto Array, optimized for the detection of ultra-low surface brightness structures.