Nuclear and Star Formation Activities in Nearby Galaxies: Roles of Gas Supply and AGN Feedback

TL;DR

This study examines how gas supply and AGN feedback influence star formation and nuclear activity in nearby galaxies, revealing evolutionary links and the roles of different galaxy types in these processes.

Contribution

It provides a comprehensive analysis of a large galaxy sample, highlighting the relationship between star formation, AGN activity, and galaxy evolution, with new insights into the roles of gas supply and feedback mechanisms.

Findings

Seyfert galaxies have the highest Eddington ratios and bluer colors.

Galaxies likely evolve from blue star-forming to red LINERs through intermediate phases.

Radio luminosity correlates with stellar mass but not directly with Eddington ratios.

Abstract

We analyzed a sample of $\sim$113,000 galaxies ($\rm z < 0.3$) from the Sloan Digital Sky Survey, divided into star-forming, composite, Seyfert, and LINER types, to explore the relationships between UV-to-optical colors ($\rm u-r$), star formation rates (SFRs), specific star formation rates (sSFRs), stellar velocity dispersions ($\rm \sigma_{*}$), mass accretion rates onto the black hole ($\rm L_{[OIII]}/\sigma_{*}^{4}$), and Eddington ratios. Star-forming galaxies predominantly feature young, blue stars along the main-sequence (MS) line, while composite, Seyfert, and LINER galaxies deviate from this line, displaying progressively older stellar populations and lower SFRs. $\rm L_{[OIII]}/\sigma_{*}^{4}$ and Eddington ratios are highest in Seyfert galaxies, moderate in composite galaxies, and lowest in LINERs, with higher ratios associated with bluer colors, indicating a younger stellar population and stronger active galactic nucleus (AGN) activity. These trends suggest a strong correlation between sSFRs and Eddington ratios, highlighting a close connection between AGN and star formation activities. These results may imply an evolutionary sequence where galaxies transition from blue star-forming galaxies to red LINERs, passing through composite and Seyfert phases, driven primarily by gas supply, with AGN feedback playing a secondary role. While both radio luminosities ($\rm L_{1.4GHz}$) and Eddington ratios correlate with SFRs, their trends differ on the SFR$-$stellar mass ($\rm M_{*}$) plane, with radio luminosities increasing with stellar mass along the MS line, and no direct connection between radio luminosities and Eddington ratios. These findings may provide new insights into the interplay between star formation, AGN activity, and radio emission in galaxies, shedding light on their evolutionary pathways.