The thick disk in the galaxy NGC 4244 from S4G imaging

TL;DR

This study uses S4G imaging data to identify signs of a thick disk in NGC 4244, challenging previous reports of its absence and suggesting implications for galaxy evolution processes.

Contribution

It provides the first evidence of a thick disk in NGC 4244 using infrared imaging, highlighting the subtlety of thick disks in late-type galaxies.

Findings

Detected signs of two disk components in NGC 4244.

Asymmetries explained by galaxy inclination and opacity.

Thick disk subtlety linked to galaxy evolution factors.

Abstract

If thick disks are ubiquitous and a natural product of disk galaxy formation and/or evolution processes, all undisturbed galaxies which have evolved during a significant fraction of a Hubble time should have a thick disk. The late-type spiral galaxy NGC 4244 has been reported as the only nearby edge-on galaxy without a confirmed thick disk. Using data from the Spitzer Survey of Stellar Structure in Galaxies (S4G) we have identified signs of two disk components in this galaxy. The asymmetries between the light profiles on both sides of the mid-plane of NGC 4244 can be explained by a combination of the galaxy not being perfectly edge-on and a certain degree of opacity of the thin disk. We argue that the subtlety of the thick disk is a consequence of either a limited secular evolution in NGC 4244, a small fraction of stellar material in the fragments which built the galaxy, or a high amount of gaseous accretion after the formation of the galaxy.