The origin and properties of red spirals: Insights from cosmological simulations

TL;DR

This study uses cosmological simulations to investigate the origins and properties of red spiral galaxies, revealing that most are quenched by AGN feedback and are characterized by low gas content, high metallicity, and larger stellar masses.

Contribution

It provides a detailed analysis of red spiral galaxies' properties and origins using the IllustrisTNG100 simulation, highlighting the dominant role of AGN feedback in quenching.

Findings

Most red spirals are gas-poor with low SFRs and high metallicity.

Approximately 13% of red spirals experienced environmental gas stripping.

AGN feedback is the primary quenching mechanism for the majority of red spirals.

Abstract

A significant fraction of spiral galaxies are red, gas-poor, and have low star formation rates (SFRs). We study these unusual objects using the IllustrisTNG100 simulation. Among 1912 well-resolved disk galaxies selected from the last simulation output, we identify 377 red objects and describe their properties and origins using a few representative examples. The simulated red spirals turn out to be typically very gas-poor, have very low SFRs, are more metal-rich, and have larger stellar masses than the remaining disks. Only about 13% of red spirals suffered strong mass loss and thus could have resulted from environmental quenching by ram pressure and tidal stripping of the gas, or similar processes. The majority of red disks were probably quenched by feedback from the active galactic nucleus (AGN). This conclusion is supported by the higher black hole masses and lower accretion rates of red disks, as well as the larger total AGN feedback energies injected into the surrounding gas in the kinetic feedback mode implemented in the IllustrisTNG simulations. The timescales of the gas loss correlate with the black hole growth for the AGN-quenched galaxies and with the dark-matter loss for the environmentally quenched ones. The red spirals are more likely to possess bars, and their bars are stronger than in the remaining disks, which is probably the effect of gas loss rather than the reason for quenching.