Evolution of submillimeter galaxies across cosmic-web environments

Abstract

Submillimeter galaxies (SMGs) provide valuable insights into galaxy formation and evolution and are likely influenced by their cosmic environment. However, their rarity makes environmental trends difficult to establish. We use the FLAMINGO simulation, which simultaneously reproduces the redshift distribution and number counts of SMGs. We use the DisPerSE to identify filamentary structures at $z=4$, 3, 2, 1.5, and 1. We define inner cluster-halo, outer cluster-halo, inner filament, outer filament, and void/wall environments at each redshift considering mass evolution of cluster-halos and density evolution of filaments. For a fixed stellar-mass cut of $M_* \geq 10^{9}$ M$_{\odot}$, the fraction of SMGs in the inner cluster-halo environment declines from $\sim30\%$ at $z=4$ to $\sim3\%$ by $z=1$, and similar trends are observed in other environments. The abundance of SMGs within a cluster-halo increases with halo mass, mirroring the increase in the total galaxy population. Consequently, the ratio of SMG halo occupation to that of all galaxies is largely insensitive to halo mass, but varies with redshift. In contrast, the ratio of the halo occupation of non-SMGs to that of all galaxies declines with halo mass and shows little redshift evolution. We show that the central and satellite SMGs form two distinct populations in inner cluster-halos. SMGs occupy the metal-rich side of the metallicity distribution, but rarely attain the highest metallicities because ongoing enrichment is limited by gas depletion. The brightest SMGs (S$_{850} > 10$ mJy) are found exclusively in inner cluster-halos, highlighting a strong connection between SMG luminosity and environmental density. Our results show that SMGs dominate star formation in dense environments, contributing up to $80\%$ of the SFR in inner cluster-halos at $z=4$, but less than $50\%$ in low-density regions.

Figures (6)

• Figure 1: Left: panel shows the cumulative halo mass functions at redshifts $z=4$, 3, 2, 1.5, 1, and 0, respectively, with the blue, orange, green, red, purple, and brown color curves. The vertical gray color dotted line indicates the minimum halo mass at $z=0$ used to define cluster-halo, whereas horizontal line indicate corresponding halo number density at $z=0$. The intersections of horizontal gray color line with cumulative halo mass functions indicate the lower mass limit of halo ($\rm M_{Thresh} (z)$) used to define cluster-halo at corresponding redshift. Right: panel shows the stacked radial galaxy number density for the filaments collapsed along their spines. The vertical dashed and dotted gray color lines indicate the radii used to define the extent of inner ($R = 1$ pMpc) and outer ($R = 2$ pMpc) filament regions, respectively.
• Figure 2: Top: The percentage of SMGs (non-SMGs) in different environments using hatched (unhatched) bars. Redshifts $z=4$, 3, 2, 1.5, and 1 are represented by the blue, orange, green, red, and purple colors, respectively. Middle: Redshift evolution of the SMG and non-SMG fractions across cosmic environments, normalized by the total galaxy population in each environment. Bottom: Redshift evolution of the SMG-to-non-SMG ratio in different cosmic environments. In all three panels, SMGs and non-SMGs are modeled for galaxies with $\rm M_{*} \ge 10^{9}~\rm M_{\odot}$.
• Figure 3: Panel (a): The median halo occupation of galaxies within the inner cluster-halo environment at redshifts $z=4$ (blue circles), 3 (orange triangles), 2 (green boxes), 1.5 (red diamonds), and 1 (purple crosses). Panel (b): The median halo occupation of SMGs. Panel (c): The median halo occupation of non-SMGs. Panel (d): The ratio of the halo occupation of SMGs to that of all galaxies. Panel (e): The ratio of the halo occupation of non-SMGs to that of all galaxies. We note that SMGs and non-SMGs are modeled for galaxies with $\rm M_{*} \ge 10^{9}~M_\odot$. In all panels, the shaded regions indicate the 16th to 84th percentile range.
• Figure 4: Evolution of the stellar mass function (left panels), star-forming gas mass function (middle panels), and star formation rate function (right panels) in different cosmic environments as indicated on the right-most panel of each row (from top to bottom: inner cluster-halo, outer cluster-halo, inner filament, outer filament, and void/wall). The solid blue, orange, green, red, and purple color curves of each panel represents SMGs in a specific cosmic environment at redshift $z=4$, 3, 2, 1.5, and 1, respectively, whereas the dotted curves of corresponding colors show all galaxies in the same cosmic environment. The vertical marks at the bottom of each panel indicate the mean values of SMGs. The thin panels at the bottom of each main panel shows the relative contribution of SMGs as the ratio of SMGs to total galaxies with $\rm M_{*} \ge 10^{9}~M_\odot$.
• Figure 5: Evolution of the star-forming gas metallicity function (left panels), disk-to-total mass ratio function (middle panels), and submillimeter flux density function (right panels) in different cosmic environments as indicated on the right-most panel of each row. The solid blue, orange, green, red, and purple color curves of each panel represents SMGs in a specific cosmic environment at redshift $z=4$, 3, 2, 1.5, and 1, respectively, whereas the dotted curves of corresponding colors show all galaxies in the same cosmic environment. The vertical marks at the bottom of each panel indicate the mean values of SMGs.