Galaxy And Mass Assembly (GAMA): Deconstructing the galaxy stellar mass function by star formation and environment

Abstract

Using the equatorial Galaxy and Mass Assembly (GAMA) dataset, we investigate how the low-redshift galaxy stellar mass function (GSMF) varies across different galaxy populations and as a function of halo mass. We find that: (i) The GSMF of passive and star-forming galaxies are well described by a double and a single Schechter function, respectively, although the inclusion of a second component for the star-forming population yields a more accurate description. Furthermore, star-forming galaxies dominate the low-mass end of the total GSMF, whereas passive galaxies mainly shape the intermediate-to-high-mass regime. (ii) The GSMF of central galaxies dominates the high-mass end, whereas satellites and ungrouped galaxies shape the intermediate-to-low-mass regime. Additionally, we find a relative increase in the abundance of low-mass galaxies moving from dense group environments to isolated systems. (iii) More massive halos host more massive galaxies, have a higher fraction of passive systems, and show a steeper decline in the number of intermediate-mass galaxies. Finally, our results reveal larger differences between passive and star-forming GSMFs than predicted by a phenomenological quenching model, but generally confirm the environmental quenching trends for centrals and satellites reported in other works.

Figures (19)

• Figure 1: Distribution of the LP parameter. The dashed red line marks our lower limit (LP $= -50$) that has been applied to exclude galaxies with poor SED fits, caused by unreliable photometric data.
• Figure 2: Selection of star-forming and passive galaxies using the $\log M-\log$ SFR plane. The dashed blue and red lines display the star-forming and passive population fits, respectively, whereas the solid green line displays our final dividing line. Star-forming galaxies are shown in cyan and passive galaxies in pink. Black dots refer to the $242$ sources with LP $<-50$ (Sect. \ref{['3.1.1']}).
• Figure 3: GSMFs for our total, star-forming and passive galaxy populations, as indicated in the legend. Panel (a) shows the full sample, whereas panels (b) and (c) show grouped and ungrouped galaxies, respectively. In each sub-figure, the lower panel shows the GSMFs, and the upper panel displays the raw number of galaxies as a function of stellar mass in each sample, as indicated. Dashed lines in panel (a) show the two individual Schechter components of each GSMF.
• Figure 4: Best-fit double Schechter function parameters of the GSMFs shown in Fig. \ref{['fig:6.1']}, using the same colour-coding. The $x$-axes distinguish between all, grouped, and ungrouped galaxies; within each sample, the three ticks correspond to the total (T), star-forming (SF), and passive (P) subsamples. The corresponding corner plots illustrating the correlations among the fitted parameters are provided in Figs. \ref{['fig:appendix1']}--\ref{['fig:appendix3']}.
• Figure 5: GSMFs for our total, central, satellite, and ungrouped galaxy populations, as indicated in the legend. The left-hand panel shows the GSMFs for each entire population, while the right-hand panel shows their subdivision into star-forming and passive galaxies. In each sub-figure, the lower panel shows the GSMFs, and the upper panel displays the raw number of galaxies as a function of stellar mass in each sample, as indicated.