Galaxy And Mass Assembly (GAMA) : the galaxy stellar mass function to z=0.1 from the r-band selected equatorial regions

Abstract

We derive the low-redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial Galaxy And Mass Assembly (GAMA) data set covering 180 deg2. We construct the mass function using a density-corrected maximum volume method, using masses corrected for the impact of optically thick and thin dust. We explore the galactic bivariate brightness plane (M⋆–μ), demonstrating that surface brightness effects do not systematically bias our mass function measurement above 107.5 M⊙. The galaxy distribution in the M–μ plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is fitted with a double Schechter function, with M⋆=1010.78±0.01±0.20 M⊙,ϕ^⋆_1=(2.93±0.40)×10−3h^3_70 Mpc−3, α1 = −0.62 ± 0.03 ± 0.15,ϕ^⋆_2=(0.63±0.10)×10−3h^3_70 Mpc−3 and α2 = −1.50 ± 0.01 ± 0.15. We find the equivalent faint end slope as previously estimated using the GAMA-I sample, although we find a higher value ofM⋆. Using the full GAMA-II sample, we are able to fit the mass function to masses as low as 107.5 M⊙, and assess limits to 106.5 M⊙. Combining GAMA-II with data from G10-COSMOS, we are able to comment qualitatively on the shape of the GSMF down to masses as low as 106 M⊙. Beyond the well-known upturn seen in the GSMF at 109.5, the distribution appears to maintain a single power-law slope from 109 to 106.5. We calculate the stellar mass density parameter given our best-estimate GSMF, findingΩ⋆=1.66^+0.24_−0.23±0.97 h^−1_70×10−3, inclusive of random and systematic uncertainties.