Study of Galaxies in the Lynx-Cancer Void. IV. Photometric Properties

TL;DR

This study analyzes the photometric properties of 85 galaxies in the Lynx-Cancer void using SDSS data, revealing their star formation histories, stellar masses, and gas content, and comparing them with more typical galaxy samples.

Contribution

It provides detailed photometric and evolutionary analysis of galaxies in the Lynx-Cancer void, highlighting their star formation timelines and gas properties, which is novel for this specific void environment.

Findings

Most galaxies have star formation times comparable to the universe's age.

A subset of low-luminosity galaxies are relatively unevolved with younger star formation histories.

Gas-rich galaxies can have gas mass fractions up to 94-99%.

Abstract

We present the results of a photometric study of 85 objects from the updated sample of galaxies residing in the nearby Lynx--Cancer void. We perform our photometry on u, g, r, and i-band images of the Sloan Digital Sky Survey. We determine model-independent galaxy parameters such as the integrated magnitudes and colors, effective radii and the corresponding surface brightness values, optical radii and Holmberg radii. We analyze the radial surface brightness profiles to determine the central brightness values and scale lengths of the model discs. We analyze the colors of the outer parts of the galaxies and compare them with model evolutionary tracks computed using the PEGASE2 software package. This allowed us to estimate the time T_SF elapsed since the onset of star formation, which turned out to be on the order of the cosmological time T_0 for the overwhelming majority of the galaxies studied. However, for 13 galaxies of the sample the time T_SF does not exceed T_0/2 ~ 7 Gyr, and for 7 of them T_SF < 3.5 Gyr. The latter are mostly unevolved objects dominated by low-luminosity galaxies with M_B > -13.2. We use the integrated magnitudes and colors to estimate the stellar masses of the galaxies. We estimate the parameter M(HI)/L_B and the gas mass fractions for void galaxies with known HI-line fluxes. A small subgroup (about 10%) of the gas-richest void galaxies with M(HI)/L_B > 2.5 has gas mass fractions that reach 94-99%. The outer regions of many of these galaxies show atypically blue colors. To test various statistical differences between void galaxies and galaxies from the samples selected using more general criteria, we compare some of the parameters of void galaxies with similar data for the sample of 195 galaxies from the Equatorial Survey (ES) based on a part of the HIPASS blind HI survey. abridged