Properties of isolated galaxies in the Digital Survey Isolated Galaxies (DSIG) catalogue within a redshift range (0.005 < z < 0.080)

Abstract

ABSTRACT Evolution of galaxies is known to be influenced by a number of factors such as the environment that hosts the galaxy as well as the galaxies intrinsic properties. The environmental effects on galaxy properties have not been fully quantified. In our study, we analysed a sample of isolated galaxies within 0.005 < z < 0.080 from Sloan Digital Sky Survey data release 16, as part of a Digital Survey Isolated Galaxies catalogue. The aim was to investigate intrinsic physical properties of singly isolated galaxies in low-density environment. We investigated the galaxies morphology, colour, luminosity, stellar masses, and star formation rates (SFRs). A concentration index, Cr, of 2.65 separates our isolated sample into early and late types, with the late-types (spiral galaxies) dominating the isolated sample at 68 per cent as confirmed from the visually classified sample obtained from Galaxy Zoo. Our isolated ellipticals are redder, massive, and more luminous, while the isolated spirals are blue, less massive, and less luminous. Both the isolated spirals and ellipticals have steeper colour relations indicating a fast transition to the red sequence. In the colour–colour analysis, most ellipticals were quiescent with the majority of spirals being star forming. 5 per cent of the isolated ellipticals have recently quenched their star formation and are transiting to the red sequence. The isolated spirals experiences higher star-forming activities, with a small fraction of passively evolving high-mass isolated spirals. Similarly, isolated ellipticals exhibit low SFRs indicating passive evolution, with a fraction being actively star forming.