Quenching in the Right Place at the Right Time: Tracing the Shared History of Starbursts, AGNs, and Post-starburst Galaxies Using Their Structures and Multiscale Environments

Abstract

This work uses multiscale environments and structures of galaxies in the Sloan Digital Sky Survey as consistency checks of the evolution from starburst to quiescence at redshift $z < 0.2$. The environmental indicators include fixed aperture mass overdensities ($\delta_{x\mathrm{Mpc}}$, $x \in \{0.5, 1, 2, 4, 8\}\,h^{-1}$Mpc), $k$-nearest neighbor distances, the tidal parameter, halo mass ($M_h$), and satellite/central classification. The residuals of specific star formation rates ($\Delta\,\mathrm{SSFR}$) is used to select starbursts ($\Delta\,\mathrm{SSFR} > 0.6\,$dex, $N \approx 8,\,600$). Quenched post-starbursts (QPSBs) are selected using H$\alpha < 3\,$angstrom in emission and H$\delta_A > 4\,$ angstrom in absorption ($N \approx 750$). The environments of starbursts and QPSBs are compared with those of active galactic nuclei (AGNs) and inactive galaxies of varying $\Delta\,\mathrm{SSFR}$. The environments of starbursts, AGNs, and QPSBs are unlike the environments of most quiescent galaxies (QGs). About $70\%-90\%$ of starbursts, AGNs with H$\delta_A > 4$, and QPSBs are centrals, $\sim 80\%-90\%$ have $M_h < 10^{13}\,M_\odot$, and only $\sim 2\%-4\%$ have $M_h > 10^{14}\,M_\odot$ or live in clusters. Their $M_h$ and satellite fractions are also different from those of QGs. All QPSBs are matched to some SFGs, starbursts, AGNs, and QGs of similar $M_\star$, environments, concentration indices, and velocity dispersions. A significant fraction ($\sim 20\%-30\%$) of starbursts cannot be matched to QPSBs or QGs. The implications are: (1) some starbursts do not quench rapidly. (2) Satellite-quenching mechanisms operating in high density environments cannot account for most QPSBs. (3) The evolution from starbursts to QPSBs to QGs is not the dominant path at $z < 0.2$. (4) Starbursts are not mainly triggered by tidal interactions.