Star Formation Rates in [Ne V] 3426 \r{A} Selected Active Galactic Nuclei: Evidence for a Decrease along the Main Sequence?

TL;DR

This study investigates the relationship between AGN activity and star formation along the galaxy main sequence using [Ne V] selected AGN, finding a decrease in specific star formation rates that suggests lower gas fractions in host galaxies, but no direct suppression evidence.

Contribution

It introduces a new analysis of [Ne V] selected AGN to examine star formation trends, highlighting the unreliability of emission-line-based sSFRs and emphasizing SED-based measurements.

Findings

sSFR decreases along the main sequence in [Ne V] AGN

Emission-line-based sSFRs are unreliable due to AGN contamination

Lower gas fractions in AGN host galaxies compared to star-forming galaxies

Abstract

Studying the behavior along the galaxy main sequence is key in furthering our understanding of the possible connection between AGN activity and star formation. We select a sample of 1215 AGN from the catalog of SDSS galaxy properties from the Portsmouth group by detection of the high-ionization [Ne V] 3426 \r{A} emission line. Our sample extends from 10$^{40}$ to 10$^{42.5}$ erg/s in [Ne V] luminosity in a redshift range z = 0.17 to 0.57. We compare the specific star formation rates (sSFRs, SFR scaled by galaxy mass) obtained from the corrected [O II] and H{\alpha} luminosities, and the SED-determined values from Portsmouth. We find that the emission-line-based sSFR values are unreliable for the [Ne V] sample due to the AGN contribution, and proceed with the SED sSFRs for our study of the main sequence. We find evidence for a decrease in sSFR along the main sequence in the [Ne V] sample which is consistent with results from the hard X-ray BAT AGN sample, which extends to lower redshifts than our [Ne V] sample. Although we do not find evidence that the concurrent AGN activity is suppressing star formation, our results are consistent with a lower gas fraction in the host galaxies of the AGN as compared to that of the star forming galaxies. If the evacuation of gas, and therefore suppression of star formation is due to AGN activity, it must have occurred in a previous epoch.