# Quantifying star formation activity in the inner 1kpc of local MIR bright QSOs

## TL;DR

This study measures star formation rates in the inner regions of local MIR-bright quasars using high-resolution MIR spectroscopy, revealing centrally concentrated star formation consistent with merger simulation predictions.

## Contribution

It provides the first detailed high-resolution MIR spectral analysis of star formation activity within 1 kpc of local MIR-bright QSOs, highlighting the central concentration of star formation.

## Key findings

- Star formation rates are around 0.2 to 1.6 M_sun/yr in the inner regions.
- Star formation activity is more centrally concentrated than in larger scales.
- Results align with merger simulations predicting centrally peaked star formation.

## Abstract

We examine star formation activity in a distance- (z<0.1) and flux-limited sample of quasars (QSOs). Mid-infrared (MIR) spectral diagnostics at high spatial resolution (~0.4 arcsec) yield star formation rates (SFRs) in the inner regions (~300 pc to 1 kpc) for 13 of 20 of the sample members. We group these objects according to the size probed by the high angular resolution spectroscopy, with characteristic scales of <0.7 and ~0.7-1 kpc. Using the polycyclic aromatic hydrocarbon (PAH) feature at 11.3 um, we measure SFRs around 0.2 and 1.6 M_{\odot}yr^{-1}. We also measure the larger aperture PAH-derived SFRs in the individual IRS/Spitzer spectra of the sample and obtain a clear detection in ~58 percent of them. We compare smaller and larger aperture measurements and find that they are similar, suggesting that star formation activity in these QSOs is more centrally concentrated, with the inner region (>~1 kpc) accounting for the majority of star formation measured on these scales, and that PAH molecules can be present in most local MIR-bright QSOs within a few hundred pc from the central engine. By comparison with merger simulations, we find that our estimation of the SFR and black hole (BH) accretion rates are consistent with a scenario in which the star formation activity is centrally peaked as predicted by simulations.