Linking the brightest stellar streams with the accretion history of Milky Way-like galaxies

TL;DR

This study uses hydrodynamical simulations to analyze the brightest stellar streams in Milky Way-like galaxies, revealing their properties, detectability limits, and relation to galaxy accretion history.

Contribution

It provides new insights into the properties and detectability of stellar streams and their progenitors in galaxy formation models, based on a comprehensive simulation analysis.

Findings

Bright streams are detectable at surface brightness limits of 27-28 mag arcsec$^{-2}$.

Most brightest stream progenitors are accreted over 1.6-10 Gyr ago, with only 25% accreted in the last 5 Gyr.

37% of progenitors survive to present day, with a relation between mass and infall time.

Abstract

According to the current galaxy formation paradigm, mergers and interactions play an important role in shaping present-day galaxies. The remnants of this merger activity can be used to constrain galaxy formation models. In this work we use a sample of thirty hydrodynamical simulations of Milky Way-mass halos, from the AURIGA project, to generate surface brightness maps and search for the brightest stream in each halo as a function of varying limiting magnitude. We find that none of the models shows signatures of stellar streams at $\mu_{r}^{lim} \leq 25$ mag arcsec$^{-2}$. The stream detection increases significantly between 27 and 28 mag arcsec$^{-2}$. Nevertheless, even at 30 mag arcsec$^{-2}$, 13 percent of our models show no detectable streams. We study the properties of the brightest streams progenitors (BSPs). We find that BSPs are accreted within a broad range of infall times, from 1.6 to 10 Gyr ago, with only 25 percent accreted within the last 5 Gyrs; thus most BSPs correspond to relatively early accretion events. We also find that 37 percent of the BSPs survive to the present day. The median infall times for surviving and disrupted BSPs are 5.6 and 6.7 Gyr, respectively. We find a clear relation between infall time and infall mass of the BSPs, such that more massive progenitors tend to be accreted at later times. However, we find that the BSPs are not, in most cases, the dominant contributor to the accreted stellar halo of each galaxy.