Star Formation in Nearby Isolated Galaxies

TL;DR

This study analyzes star formation in nearby isolated galaxies using GALEX FUV data, revealing a universal upper limit on specific star formation rates and highlighting the properties of gas-rich, late-type galaxies in low-density regions.

Contribution

It provides the first comprehensive analysis of star formation properties in isolated galaxies within the Local Supercluster using FUV data.

Findings

Most galaxies have SSFR below 0.4 Gyr^{-1}.

A quasi-Eddington limit for star formation exists.

Isolated galaxies are predominantly late-type, gas-rich objects.

Abstract

We use the FUV fluxes measured with the GALEX to study the star formation properties of galaxies collected in the "Local Orphan Galaxies" catalog (LOG). Among 517 LOG galaxies having radial velocities V(LG) < 3500 km/s and Galactic latitudes |b|> 15 degr, 428 objects have been detected in FUV. We briefly discuss some scaling relations between the specific star formation rate (SSFR) and stellar mass, HI-mass, morphology, and surface brightness of galaxies situated in extremely low density regions of the Local Supercluster. Our sample is populated with predominantly late-type, gas-rich objects with the median morphological type of Sdm. Only 5% of LOG galaxies are classified as early types: E, S0, S0/a, however, they systematically differ from normal E and S0 galaxies by lower luminosity and presence of gas and dust. We find that almost all galaxies in our sample have their SSFR below 0.4 [Gyr^{-1}]. This limit is also true even for a sample of 260 active star-burst Markarian galaxies situated in the same volume. The existence of such a quasi-Eddington limit for galaxies seems to be a key factor which characterizes the transformation of gas into stars at the current epoch.