Star formation rate density as a function of galaxy mass at z < 0.2 with MUSE and GAMA surveys

TL;DR

This study investigates how star formation rate density varies with galaxy mass at low redshifts using data from MUSE and GAMA surveys, revealing a consistent slope down to low masses and potential underdensity in the observed volume.

Contribution

It provides new measurements of SFRD as a function of galaxy mass at z < 0.2 using two different spectroscopic surveys, extending the analysis to very low stellar masses.

Findings

SFRD remains constant at low stellar masses down to 10^5.5 M_sun.

No evidence of a turn-over in the galaxy stellar mass function.

The MUSE WIDE and HUDF sample may be underdense.

Abstract

The star formation rate density (SFRD) is an important tool in galaxy evolution that allows us to identify at which cosmic time galaxies are more efficient at forming stars. For low-mass star-forming galaxies, the SFRD as a function of stellar mass can be straightforwardly related to the galaxy stellar mass function (GSMF). Given the uncertainty of the GSMF at the low-mass end, due to the challenges in observing dwarf galaxies, deriving the SFRD with respect to mass may be crucial to understand galaxy formation. Measurement of SFRD is more complete than number density in a cosmological volume because galaxies with higher SFR are easier to detect and characterize. In this work, the SFRD is derived using two different samples, one using the MUSE WIDE and MUSE Hubble Ultra Deep Field IFU spectroscopic surveys, and another using the GAMA spectroscopic survey. The first sample comprised a total of 27 star-forming galaxies at z $<$ 0.2 (H$\alpha$ selected), whereas the second contained 7579 galaxies at z $<$ 0.06 ($r$-band selected). The star formation rates are derived from measurements of the H$\alpha$ emission line fluxes for the first sample, and using MagPhys SED fitting for the second one. The results show the behaviour of the SFRD to the lowest stellar masses of 10$^{5.5}$ $M_{\odot}$, consistent with a constant slope (in log SFRD versus log stellar mass) and thus no turn-over in the GSMF. The results also suggest that the volume considered for the MUSE WIDE and HUDF sample is underdense.