Environmental dependence of galaxy properties in the southern GAMA regions

TL;DR

This work quantifies how galaxy properties depend on local environment in the southern GAMA regions G02 and G23 using the two-point and marked correlation functions. It robustly measures color, near-infrared luminosity, stellar mass, and star-formation indicators across scales up to $7\ h^{-1}\mathrm{Mpc}$, and examines the impact of redshift incompleteness and cosmic variance. The analysis finds that $u-r$ and $g-r$ colors are the strongest environment tracers, stellar mass and near-IR luminosities correlate with overdensity, while SFR and sSFR anti-correlate with density; red/near-IR bands provide useful proxies for stellar mass growth and quenching. Its results serve as key constraints for models of galaxy assembly in different environments and offer practical guidance for interpreting future near-IR surveys and high-redshift studies.

Abstract

Using data from the Galaxy and Mass Assembly (GAMA) survey, we investigate how galaxy properties correlate with the local environment, focusing on the two southern regions of the survey (G02 and G23) that have not previously been examined in this context. We employ two-point and marked correlation functions to quantify the environmental dependence of galaxy color, stellar mass, luminosity across the $u$, $g$, $r$, $J$, and $K$ bands, as well as star formation rate (SFR) and specific star formation rate (sSFR). We also assess the impact of redshift incompleteness and cosmic variance on these clustering measurements. Our results show that $u-r$ and $g-r$ colors are most strongly correlated with local overdensity, followed by stellar mass. The sSFR exhibits a clear inverse relationship with density of the environment, consistent with the trend observed for $u$-band luminosity, which traces young stellar populations. In contrast, galaxies brighter in the $g$, $J$, and $K$ bands preferentially inhabit denser regions. By comparing our measurements from the southern regions with those from the equatorial regions of GAMA, we find that cosmic variance does not significantly influence our conclusions. However, redshift incompleteness affects the clustering measurements, as revealed through comparisons of subsets within the G02 region. The measured correlations provide key constraints for models of galaxy assembly across mass and environment, while the environmental trends in color and near-infrared luminosity offer a means to trace stellar mass growth and quenching with redshift.

Figures (8)

• Figure 1: Left panel: Selection of samples from the G02 region. The red lines indicate a redshift limit from 0.1 to 0.2 and a stellar mass cut of $\log_{10}\left(M_{\star}/\mathrm{M}_{\sun}\right) > 9.5$. Galaxies within the red lines form the samples $G02LC$ (blue dots) and $G02HC$ (orange dots). Right panel: RA-DEC distribution of galaxies in the selected samples $G02LC$ and $G02HC$.
• Figure 2: Left panel: Selection of galaxy sample from the G23 region. The red lines indicate a redshift limit from 0.1 to 0.2 and a stellar mass cut of $\log_{10}\left(M_{\star}/\mathrm{M}_{\sun}\right) > 9.7$. Galaxies within the red lines form the sample $G23$. Right panel: RA-DEC distribution of galaxies in sample $G23$.
• Figure 3: Rank-ordered projected MCFs for the low-completeness sample $G02LC$ (left panel) and the high-completeness sample $G02HC$ (right panel) within the G02 region of the GAMA survey. Different markers denote the different galaxy properties used in the MCF calculation, as indicated in the legend. The horizontal dashed line represents $M_\mathrm{p}(r_\mathrm{p})=1$. The MCF error bars shown are the jackknife and shuffling errors added in quadrature.
• Figure 4: Left panel: Projected 2pCFs for the $G02LC$ and $G02HC$ samples. The inset plot shows the best-fit power-law parameters (filled stars) along with their $1\sigma$, $2\sigma$, and $3\sigma$ (solid, dashed, and dotted) uncertainty contours. Right panel: Ratio of MCFs of the high-completeness sample to that of the low-completeness sample, $M_{G02HC}/M_{G02LC}$. Different colored lines represent the MCF ratios for different galaxy properties. Error bars of $\omega_\mathrm{p}(r_\mathrm{p})$ are estimated via jackknife resampling. While the errors in MCF ratios, calculated in quadrature, are represented by their corresponding color shaded region.
• Figure 5: Left panel: Projected 2pCF for the $G23$ sample, with a power-law fit. The inset shows the best-fit power-law parameters (filled star) and their corresponding $1\sigma$, $2\sigma$, and $3\sigma$ (solid, dashed, and dotted) uncertainty contours. Error bars of 2pCF are from the diagonal elements of the covariance matrix obtained through jackknife resampling. Right panel: Rank-ordered projected MCFs with different markers indicating the different galaxy properties used as marks. The MCF error bars shown are the jackknife and shuffling errors added in quadrature. The horizontal dashed line represents $M_\mathrm{p}(r_\mathrm{p})=1$.