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Special Colloquium |
Dr. Yaherlin Diaz
| SCHEDULED |
Universidad Diego Portales, Chile
We present a study of mid-infrared emission in a sample of 138 local
active galactic nuclei (AGN; ⟨z⟩ = 0.03 - covering the central ~2.16
kpc), using low-resolution Spitzer/IRS observations. We measured the
fluxes of the 6.2, 7.7, 8.6, and 11.3 µm polycyclic aromatic
hydrocarbon (PAH) features to assess their viability as tracers of star
formation in AGN hosts. PAH features were detected in over 68% (106/138)
of the sample, with the more resilient 11.3 µm feature present in 92%
of sources. We find that the PAH-based star formation rate (SFR)
correlates positively with X-ray luminosity, suggesting a potential
connection between the AGN activity and star formation on kiloparsec
scales. However, we find no significant correlation between PAH emission
and AGN properties such as Eddington ratio or black hole mass.
Interestingly, in unobscured or type 1 AGN (column densities log(NH) <
22), the 11.3 µm PAH feature is more correlated with AGN emission,
implying that PAH molecules can be excited by the central engine only
when not shielded by intervening material. Our results highlight the
need for specific corrections when using PAH features as star formation
indicators in AGN environments.