The optical vs. mid-infrared spectral properties of 82 Type 1 AGNs: coevolution of AGN and starburst

TL;DR

This study explores the relationship between optical and mid-infrared spectral features in 82 Type 1 AGNs, revealing correlations that shed light on the coevolution of AGN activity and starburst phenomena.

Contribution

It provides a comparative analysis of optical and MIR diagnostics for starburst activity in AGNs, highlighting their differences and correlations.

Findings

Increased MIR starburst indicators correlate with higher optical line EWs.

MIR spectral index increase correlates with decreased EW([OIII]).

Weak relation between [OIII]/Hβ ratio and PAH contribution.

Abstract

We investigated the connection between the mid-infrared (MIR) and optical spectral characteristics in a sample of 82 Type 1 active galactic nuclei (AGNs), observed with Infrared Spectrometer on Spitzer (IRS) and Sloan Digital Sky Survey (SDSS, DR12). We found several interesting correlations between optical and MIR spectral properties: i) as starburst significators in MIR increase, the EWs of optical lines H$\beta$NLR and FeII, increase as well; ii) as MIR spectral index increases, EW([OIII]) decreases, while fractional contribution of AGN (RAGN) is not connected with EW([OIII]); iii) The log([OIII]5007/$\rm H\beta$NLR) ratio is weakly related to the fractional contribution of polycyclic aromatic hydrocarbons (RPAHs). We compare the two different MIR and optical diagnostics for starburst contribution to the overall radiation (RPAH and BPT diagram, respectively). The significant differences between optical and MIR starburst diagnostics were found. The starburst influence to observed correlations between optical and MIR parameters is discussed.