Very Thin Disc Galaxies in The SDSS Catalog of Edge-on Galaxies

TL;DR

This study investigates very thin disc galaxies in the SDSS catalog, revealing their similarities to low surface brightness galaxies, their low dust content, and a threshold surface density related to their thin, rotationally supported structure.

Contribution

The paper introduces a detailed analysis of very thin disc galaxies, highlighting their properties, spectral characteristics, and environmental preferences, and proposes a threshold surface density for their formation.

Findings

VTD galaxies are mostly bulgeless and have low dust content.

They share properties with low surface brightness galaxies.

A threshold central surface density of about 88 Mo/pc² is identified.

Abstract

We study the properties of galaxies with very thin discs using a sample of 85 objects whose stellar disc radial-to-vertical scale ratio determined from photometric decomposition, exceeds nine. We present evidences of similarities between the very thin disc galaxies (VTD galaxies) and low surface brightness (LSB) disc galaxies, and conclude that both small and giant LSB galaxies may reveal themselves as VTD, edge-on galaxies. Our VTD galaxies are mostly bulgeless, and those with large radial scale length tend to have redder colors. We performed spectral observations of 22 VTD galaxies with the Dual Imaging Spectrograph on the 3.5m telescope at the Apache Point Observatory. The spectra with good resolution (R ~ 5000) allow us to determine the distance and the ionized gas rotation curve maximum for the galaxies. Our VTD galaxies have low dust content, in contrast to regular disc galaxies. Apparently, VTD galaxies reside in specific cosmological low-density environments and tend to have less connection with filaments. Comparing a toy model that assumes marginally low star formation in galactic discs with obtained gas kinematics data, we conclude that there is a threshold central surface density of about 88 Mo/pc**2, which we observe in the case of very thin, rotationally supported galactic discs.