Dark influences III. Structural characterization of minor mergers of dwarf galaxies with dark satellites

TL;DR

This paper uses hydrodynamical simulations to identify structural, morphological, and kinematic signatures of minor mergers between dwarf galaxies and dark satellites, aiding their observational detection.

Contribution

It introduces new indicators such as asymmetries and starburst locations to identify dark satellite mergers in dwarf galaxies.

Findings

Large asymmetries in gas and stars indicate mergers.

Off-centered starbursts can locate dark satellites.

Merging systems show diverse indicator values.

Abstract

In the current concordance cosmology small halos are expected to be completely dark and can significantly perturb low-mass galaxies during minor merger interactions. These interactions may well contribute to the diversity of the dwarf galaxy population. Dwarf galaxies in the field are often observed to have peculiarities in their structure, morphology, and kinematics, as well as strong bursts of star formation without apparent cause. We aim to characterize the signatures of minor mergers of dwarf galaxies with dark satellites to aid their observational identification. We explore and quantify a variety of structural, morphological, and kinematic indicators of merging dwarf galaxies and their remnants using a suite of hydrodynamical simulations. The most sensitive indicators of mergers with dark satellites are large asymmetries in the gaseous and stellar distributions, enhanced central surface brightness and starbursts, and velocity offsets and misalignments between the cold gas and stellar components. In general, merging systems span a wide range of values of the most commonly used indicators, while isolated objects tend to have more confined values. Interestingly, we find in our simulations that a significantly off-centered burst of star formation can pinpoint the location of the dark satellite. Observational systems with such characteristics are perhaps the most promising for unveiling the presence of the hitherto, missing satellites.