Gas accretion from minor mergers in local spiral galaxies

TL;DR

This study quantifies gas accretion from minor mergers in local spiral galaxies, finding it to be insufficient to sustain star formation, thus implying other mechanisms are responsible for gas supply.

Contribution

It introduces a new method to estimate gas accretion rates from minor mergers using HI data and provides the first upper limit estimates for local galaxies.

Findings

Maximum gas accretion rate estimated at 0.28 solar masses per year.

Only 22% of galaxies have detected dwarf companions.

Minor mergers contribute minimally to the total gas budget.

Abstract

In this paper we quantify the gas accretion rate from minor mergers onto star-forming galaxies in the Local Universe using HI observations of 148 nearby spiral galaxies (WHISP sample). We developed a dedicated code that iteratively analyses HI data-cubes, finds dwarf gas-rich satellites around larger galaxies and estimates an upper limit to the gas accretion rate. We found that 22% of the galaxies have at least one detected dwarf companion. We made the very stringent assumption that all satellites are going to merge in the shortest possible time transferring all their gas to the main galaxies. This leads to an estimate of the maximum gas accretion rate of 0.28 solar masses per year, about five times lower than the average SFR of the sample. Given the assumptions, our accretion rate is clearly an overestimate. Our result strongly suggests that minor mergers do not play a significant role in the total gas accretion budget in local galaxies.