Implications of the correlation between bulge-to-total baryonic mass ratio and the number of satellites for SAGA galaxies

TL;DR

This study investigates the relationship between the number of satellite galaxies and fundamental properties of Milky Way-like galaxies, revealing correlations with bulge mass and angular momentum that suggest new insights into satellite formation.

Contribution

It uncovers novel correlations between satellite count and galactic properties like bulge mass and angular momentum, based on the SAGA survey data.

Findings

Positive correlation between bulge mass and satellite number

Negative correlation between angular momentum and satellite number

Deeper observations needed to confirm these correlations

Abstract

We searched for correlations between the number of satellites and fundamental galactic properties for the Milky Way-like host galaxies in order to better understand their diverse satellite populations. We specifically aim to understand why galaxies that are very similar in stellar mass content, star formation rate, and local environment have very different numbers of satellites. Satellites of Galactic Analogs (SAGA) spectroscopic survey has completed spectroscopic observations of 36 Milky Way-like galaxies within their virial radii down to the luminosity of Leo I dwarf galaxy. All the available galactic properties of SAGA galaxies from the literature along with measured stellar masses were correlated with the number of satellites and no significant correlation was found. However, when we considered the "expected" number of satellites based on the correlation between the baryonic bulge-to-total ratio and the number of satellites confirmed for several nearby galaxies then strong correlations emerge between this number and (1) the mass of the bulge, and (2) the total specific angular momentum. The first correlation is positive, implying that galaxies with more massive bulges have more satellites, as already confirmed. The second correlation with the angular momentum is negative, meaning that, the smaller the angular momentum, the greater the number of expected satellites. This would imply that either satellites cannot form if galaxy angular momentum is too high, or that satellites form inside-out, so that angular momentum is being transferred to the outer parts of the galaxies. However, deeper spectroscopic observations are needed to confirm these findings, because they rely on the expected rather than detected number of satellites. There was a luminosity limit to the SAGA survey equivalent to the luminosity of Leo I dwarf satellite of the Milky Way galaxy.