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| DOI | 10.1088/0004-6256/144/1/11 | ||||
| Año | 2012 | ||||
| Tipo | artículo de investigación |
Citas Totales
Autores Afiliación Chile
Instituciones Chile
% Participación
Internacional
Autores
Afiliación Extranjera
Instituciones
Extranjeras
We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs), and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGNs; L-bol less than or similar to 10(42) erg s(-1)). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGNs, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGNs have not yet been well determined. We separate the present LLAGN sample into three categories depending on their Eddington ratio and radio emission, finding different IR characteristics for each class. (1) At the low-luminosity, low-Eddington-ratio (log L-bol/L-Edd < -4.6) end of the sample, we identify "host-dominated" galaxies with strong polycyclic aromatic hydrocarbon bands that may indicate active (circum-)nuclear star formation. (2) Some very radio-loud objects are also present at these low Eddington ratios. The IR emission in these nuclei is dominated by synchrotron radiation, and some are likely to be unobscured type 2 AGNs that genuinely lack a broad-line region. (3) At higher Eddington ratios, strong, compact nuclear sources are visible in the MIR images. The nuclear SEDs of these galaxies are diverse; some resemble typical Seyfert nuclei, while others lack a well-defined MIR "dust bump." Strong silicate emission is present in many of these objects. We speculate that this, together with high ratios of silicate strength to hydrogen column density, could suggest optically thin dust and low dust-to-gas ratios, in accordance with model predictions that LLAGNs do not host a Seyfert-like obscuring torus. We anticipate that detailed modeling of the new data and SEDs in terms of accretion disk, jet, radiatively inefficient accretion flow, and torus components will provide further insights into the nuclear structures and processes of LLAGNs.
| Ord. | Autor | Género | Institución - País |
|---|---|---|---|
| 1 | Mason, R. E. | - |
Observatorio Gemini - Estados Unidos
Gemini Observatory - Estados Unidos |
| 2 | Lopez-Rodriguez, Enrique | Hombre |
UNIV FLORIDA - Estados Unidos
University of Florida - Estados Unidos |
| 3 | Packham, C. | Hombre |
UNIV FLORIDA - Estados Unidos
University of Florida - Estados Unidos |
| 4 | Alonso Herrero, Almudena | Mujer |
CSIC UC - España
CSIC-UC - Instituto de Física de Cantabria (IFCA) - España |
| 5 | Levenson, Nancy A. | Mujer |
AURA Chile - Chile
Gemini ObservatorySouthern Operations Center - Chile |
| 6 | Radomski, James T. | Hombre |
AURA Chile - Chile
Gemini ObservatorySouthern Operations Center - Chile |
| 7 | RamosAlmeida, C. | Mujer |
Inst Astrofis Canarias - España
UNIV LA LAGUNA - España Instituto Astrofisico de Canarias - España Universidad de La Laguna - España |
| 8 | Colina, L. | Hombre |
Inst Nacl Tecn Aeroespacial - España
Instituto Nacional de Tecnica Aeroespacial - España |
| 9 | Elitzur, Moshe | Hombre |
UNIV KENTUCKY - Estados Unidos
University of Kentucky - Estados Unidos |
| 10 | Aretxaga, I. | Mujer |
INAOE - México
Instituto Nacional de Astrofisica Optica y Electronica - México |
| 11 | Roche, P. | Hombre |
UNIV OXFORD - Reino Unido
University of Oxford - Reino Unido |
| 12 | Oi, Nagisa | Mujer |
Grad Univ Adv Studies SOKENDAI - Japón
The Graduate University for Advanced Studies - Japón |
| Fuente |
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| National Science Foundation |
| Spanish Ministry of Science and Innovation (MICINN) |
| STFC |
| Science and Technology Facilities Council |
| Spanish Plan Nacional de Astronomia y Astrofisica |
| Direct For Mathematical & Physical Scien; Division Of Astronomical Sciences |
| Division Of Astronomical Sciences; Direct For Mathematical & Physical Scien |
| Agradecimiento |
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| We are grateful to the anonymous referee for a clear and helpful report, and we also thank J. A. Fernandez-Ontiveros for providing data in advance of publication. R.E.M. appreciates the hospitality of the University of Sheffield during a portion of this work. This paper is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministrio da Cincia e Tecnologia (Brazil), and SECYT (Argentina). A.A.-H. and L.C. acknowledge support from the Spanish Plan Nacional de Astronomia y Astrofisica under grants AYA2009-05705-E and AYA2010-21161-C02-1. C.R.A. acknowledges the Spanish Ministry of Science and Innovation (MICINN) through project Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC (http://www.iac.es/consolider-ingenio-gtc/) and PN AYA2010-21887-C04.04. |