Star Formation Properties of Sloan Digital Sky Survey BOSS Void Galaxies in the Hyper Suprime-Cam Survey

TL;DR

This study uses the Hyper Suprime-Cam Survey to analyze the properties of void galaxies from BOSS, finding they are underdense, mostly star-forming, and evolve similarly to control galaxies, supporting galaxy assembly bias.

Contribution

It provides the first detailed characterization of faint void galaxies up to z~0.7 using deep imaging, revealing their similar evolution to control galaxies and supporting assembly bias.

Findings

Void galaxies are underdense compared to the mean density.

Void galaxies have a slightly higher fraction of star-forming galaxies.

Star formation rates of void and control galaxies are similar.

Abstract

We utilize the Hyper Suprime-Cam (HSC) Wide Survey to explore the properties of galaxies located in the voids identified from the Baryon Oscillation Spectroscopic Survey (BOSS) up to z~0.7. The HSC reaches i~25, allowing us to characterize the void galaxies down to 10$^{9.2}$ solar mass. We find that the revised void galaxy densities, when including faint galaxies in voids defined by bright galaxies, are still underdense compared to the mean density from the entire field. In addition, we classify galaxies into star-forming, quiescent, and green valley populations, and find that void galaxies tend to have slightly higher fractions of star-forming galaxies under the mass and redshift control, although the significance of this result is only moderate (2$\sigma$). However, when we focus on the star-forming population, the distribution of the specific star formation rate (sSFR) of void galaxies shows little difference from that of the control galaxies. Similarly, the median sSFR of star-forming void galaxies is also in good agreement with that of the star-forming control galaxies. Moreover, the effective green valley fraction of void galaxies, defined as the number of green valley galaxies over the number of nonquiescent galaxies, is comparable to that of the control ones, supporting the suggestion that void and control galaxies evolve under similar physical processes and quenching frequencies. Our results thus favor a scenario of the galaxy assembly bias.