Stellar halos from The Dragonfly Edge-on Galaxies Survey

TL;DR

This study investigates the stellar halos of twelve nearby edge-on galaxies using the Dragonfly Telephoto Array, revealing correlations with galaxy mass and comparing observations with cosmological simulations.

Contribution

It provides new observational data on stellar halo fractions across a range of galaxy masses and compares these with theoretical predictions.

Findings

Stellar halo fractions vary widely among galaxies.

A positive correlation exists between halo fraction and galaxy mass.

Observed halo fractions are slightly lower than simulation predictions.

Abstract

We present the primary results from the Dragonfly Edge-on Galaxies Survey (DEGS), an exploration of the stellar halos of twelve nearby ($d < 25$ Mpc) edge-on disc galaxies with the Dragonfly Telephoto Array. The edge-on orientation of these galaxies allows their stellar halos to be explored with minimal obscuration by or confusion with the much brighter disc light. Galaxies in the sample span a range of stellar masses from $10^{9.68} - 10^{10.88} M_\odot$. We confirm that the wide range of stellar halo mass fractions previously seen for Milky Way-mass galaxies is also found among less massive spiral galaxies. The scatter in stellar halo mass fraction is large but we do find a significant positive correlation between stellar halo mass fraction and total stellar mass when the former is measured beyond five half-mass radii. Reasonably good agreement is found with predictions from cosmological hydrodynamical simulations, although observed stellar halo fractions appear to be somewhat lower than expected from these simulations.