Evidence for the connection between star formation rate and evolutionary phases of quasars

TL;DR

This study uses SDSS data to investigate how quasar outflows influence star formation, revealing a pattern of suppression and rebound linked to quasar evolutionary phases, supporting the idea of negative feedback on galaxy growth.

Contribution

It provides observational evidence connecting quasar outflow phases with changes in star formation rates, highlighting the negative feedback effect during quasar evolution.

Findings

Star formation rate decreases from LoBAL to HiBAL quasars.

Star formation rate increases from HiBAL to non-BAL quasars.

Results support a model of star formation quenching and rebound during quasar evolution.

Abstract

Both theory and observations suggest that outflows driven by an active central supermassive black hole (SMBH) has a feedback effect on shaping the global properties of the host galaxy. However, whether feedback from the outflow is effective, and if so, whether it is positive or negative, has long been controversial. Here, using the latest catalog from the Sloan Digital Sky Survey (SDSS), we use the flux ratio of the [O II] to [Ne V] emission lines as a proxy to compare the star formation rate (SFR) in the hosts of quasars with different types of broad absorption lines (BALs): low-ionization (Lo)BAL, high-ionization (Hi)BAL, and non-BAL. We find that SFR decreases from LoBAL to HiBAL quasars, and then increases from HiBAL to non-BAL quasars. Assuming that the sequence of LoBAL to HiBAL to non-BAL represents evolution, our results are consistent with a quenching and subsequent rebound of star formation in quasar host galaxies. This phenomenon can be explained that the SFR is suppressed by the outflow, which then rebounds once the outflow disappears as the quasars evolve from HiBALs to non-BALs. Our result suggests that the quasar outflow has a negative global feedback on galaxy evolution.