Galaxy pairs in cosmic voids

Abstract

We present a statistical analysis of different astrophysical properties of a sample of galaxy pairs in cosmic voids. The sample consists of 72 galaxy pairs with projected separations and relative radial velocities rp < 100 h−1 kpc, ∆V < 500 km s−1 in the redshift range z < 0.1. We compared the different results for this pair sample to those derived for matched samples configured in absolute magnitude, stellar mass, and concentration residing in void, wall, and global averaged environments. We find that the pair galaxies in voids tend to have bluer optical colors than the corresponding galaxies in the wall and field environments, regardless of their stellar mass and concentration, which indicates a more recent formation of the bulk of stars. We also obtained larger mid-IR color indices for the void paired galaxies with respect to the corresponding matched samples in the wall and field environments. However, we found significantly larger differences for galaxies with a high mass and concentration. We also note that a mid-IR color-color diagram of the results showed void pair members consistent with the locus of star forming galaxies, in contrast to the other environments that exhibit a bimodal behavior comprising both passive and star forming objects. The Dn(4000) parameter also shows a significant younger stellar population in paired galaxies in voids. This is also reflected in the higher star formation rate values, which show a greater efficiency for void paired galaxies. We note that the star formation efficiency is greater for void paired galaxies with a high stellar mass and concentration. We also find that the efficiency of star formation associated with galaxy interactions is significantly greater in pairs residing in cosmic voids. This increased star formation activity could be associated with the expected richer gas environment and a gentler dynamical behavior as compared to the more eccentric orbits and stronger interactions and mergers more likely to occur in the wall and field environments.