Abstract
Abstract We present the largest currently existing subarcsecond 3–5 μm atlas of 119 local (z < 0.3) active galactic nuclei (AGNs). This atlas includes AGNs of five subtypes: 22 are Seyfert 1; five are intermediate Seyferts; 46 are Seyfert 2; 26 are low-ionization nuclear emission regions; and 20 are composites/starbursts. Each active galactic nucleus was observed with the Very Large Telescope Infrared Spectrometer and Array Camera (ISAAC) in the L and/or M bands between 2000 and 2013. We detected at 3σ confidence 92 sources in the L band and 83 sources in the M band. We separated the flux into unresolved nuclear flux and resolved the flux through two-Gaussian fitting. We report the nuclear flux, extended flux, apparent size, and position angle of each source, giving 3σ upper limits for sources that are undetected. Using Wide-field Infrared Survey Explorer (WISE) W1- and W2-band photometry we derived relations predicting the nuclear L and M fluxes for Sy1 and Sy2 AGNs based on their W1–W2 color and WISE fluxes. Lastly, we compare the measured mid-infrared colors to those predicted by dusty torus models SKIRTOR, CLUMPY, CAT3D, and CAT3D-WIND, finding the best agreement with the latter. We find that models including polar winds best reproduce the 3–5 μm colors, indicating that it is an important component of dusty torus models. We found that several AGNs are bluer than models predict. We discuss several explanations for this and find that it is most plausibly stellar light contamination within the ISAAC L-band nuclear fluxes.
Highlights
Understanding the dust in the vicinity of central supermassive black holes is instrumental to understanding how active galactic nuclei (AGN) are fed and powered
Our reported fluxes are the nuclear, unresolved component of our two-Gaussian fit. We present these fluxes separately, because the unresolved flux is most relevant for study of the AGN and interferometric follow-up observations
In the L -band, we find that 15 Seyfert 1 (Sy1), 3 Syi, 32 Seyfert 2 (Sy2), 14 Low-ionization nuclear emission region galaxies (LINERs), and 9 Cps exhibit extended emission
Summary
Observation is blocked by the torus (Type 2). The dust making up the sublimation ring (the dust closest to the AGN) is ∼ 1500K and is best observed in the near-infrared (NIR). Lira et al (2013) emphasize that spectral information at 5μm is necessary to properly constrain their SED fits This midinfrared (MIR) bump is expected to originate from dust radiating at intermediate spatial scales: outside of the accretion disk and the hot dust sublimation zone, but still inside of any extended polar dust emission further out. The examination of L- and M-band fluxes in local AGN in a statistically relevant sample fulfills two goals: (i) direct observational evidence of the fact that LM-flux in excess of the classical hot torus radiation is a typical feature of nearby AGN; and (ii) the presentation of an atlas and systematic characterization of the spatially resolved radiation properties to aide the sample selection for future, detailed interferometric imaging of that excess radiation to further understand its origin. We present the observing dates and conditions of each source in Appendix A, we further explain the flux calibration procedure in Appendix B, and we present cutouts of all 119 sources in Appendix C
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