A mid-infrared spectroscopic atlas of local active galactic nuclei on sub-arcsecond resolution using GTC/CanariCam

• Published in: Monthly notices of the Royal Astronomical Society Vol. 455; no. 1; pp. 563 - 583
• Main Authors: Alonso-Herrero, A., Esquej, P., Roche, P. F., Ramos Almeida, C., González-Martín, O., Packham, C., Levenson, N. A., Mason, R. E., Hernán-Caballero, A., Pereira-Santaella, M., Alvarez, C., Aretxaga, I., López-Rodríguez, E., Colina, L., Díaz-Santos, T., Imanishi, M., Rodríguez Espinosa, J. M., Perlman, E.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01-01-2016
• Subjects: Active galactic nuclei; Luminosity; Mathematical models; Nuclei; Polyallylamine hydrochloride; Polycyclic aromatic hydrocarbons; Quasars; Seyfert galaxies; Silica; Space telescopes; Spectra; Spectroscopy; Star & galaxy formation; quasars: general; galaxies: Seyfert; infrared: galaxies; galaxies: active
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv2342

We present an atlas of mid-infrared (mid-IR) ∼ 7.5-13 μm spectra of 45 local active galactic nuclei (AGN) obtained with CanariCam on the 10.4 m Gran Telescopio CANARIAS (GTC) as part of an ESO/GTC large programme. The sample includes Seyferts and other low-luminosity AGN (LLAGN) at a median distance of 35 Mpc and luminous AGN, namely PG quasars, (U)LIRGs, and radio galaxies (RG) at a median distance of 254 Mpc. To date, this is the largest mid-IR spectroscopic catalogue of local AGN at sub-arcsecond resolution (median 0.3 arcsec). The goal of this work is to give an overview of the spectroscopic properties of the sample. The nuclear 12 μm luminosities of the AGN span more than four orders of magnitude, νL
12 μm ∼ 3 × 1041–1046 erg s−1. In a simple mid-IR spectral index versus strength of the 9.7 μm silicate feature diagram most LLAGN, Seyfert nuclei, PG quasars, and RGs lie in the region occupied by clumpy torus model tracks. However, the mid-IR spectra of some might include contributions from other mechanisms. Most (U)LIRG nuclei in our sample have deeper silicate features and flatter spectral indices than predicted by these models suggesting deeply embedded dust heating sources and/or contribution from star formation. The 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature is clearly detected in approximately half of the Seyfert nuclei, LLAGN, and (U)LIRGs. While the RG, PG quasars, and (U)LIRGs in our sample have similar nuclear νL
12 μm, we do not detect nuclear PAH emission in the RGs and PG quasars.