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Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN

Aalto, S. and Martín, S. and Costagliola, F. and González-Alfonso, E. and Muller, S. and Sakamoto, K. and Fuller, G. A. and García-Burillo, S. and van der Werf, P. and Neri, R. and Spaans, M. and Combes, F. and Viti, S. and Mühle, S. and Armus, L. and Evans, A. and Sturm, E. and Cernicharo, J. and Henkel, C. and Greve, T. R. (2015) Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN. Astronomy and Astrophysics, 584 . Art. No. A42. ISSN 0004-6361. https://resolver.caltech.edu/CaltechAUTHORS:20160115-163113572

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Abstract

We present high resolution (0.̋4) IRAM PdBI and ALMA mm and submm observations of the (ultra) luminous infrared galaxies ((U)LIRGs) IRAS 17208-0014, Arp220, IC 860 and Zw049.057 that reveal intense line emission from vibrationally excited (ν_2 = 1) J = 3–2 and 4–3 HCN. The emission is emerging from buried, compact (r < 17–70 pc) nuclei that have very high implied mid-infrared surface brightness > 5 × 10^(13) L_⊙ kpc^(-2). These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, ν_2 = 1, lines of HCN are excited by intense 14 μm mid-infrared emission and are excellent probes of the dynamics, masses, and physical conditions of (U)LIRG nuclei when H_2 column densities exceed 10^(24) cm^(-2). It is clear that these lines open up a new interesting avenue to gain access to the most obscured AGNs and starbursts. Vibrationally excited HCN acts as a proxy for the absorbed mid-infrared emission from the embedded nuclei, which allows for reconstruction of the intrinsic, hotter dust SED. In contrast, we show strong evidence that the ground vibrational state (ν = 0), J = 3–2 and 4–3 rotational lines of HCN and HCO^+ fail to probe the highly enshrouded, compact nuclear regions owing to strong self- and continuum absorption. The HCN and HCO^+ line profiles are double-peaked because of the absorption and show evidence of non-circular motions – possibly in the form of in- or outflows. Detections of vibrationally excited HCN in external galaxies are so far limited to ULIRGs and early-type spiral LIRGs, and we discuss possible causes for this. We tentatively suggest that the peak of vibrationally excited HCN emission is connected to a rapid stage of nuclear growth, before the phase of strong feedback.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1051/0004-6361/201526410DOIArticle
http://www.aanda.org/articles/aa/abs/2015/12/aa26410-15/aa26410-15.htmlPublisherArticle
ORCID:
AuthorORCID
Sakamoto, K.0000-0003-0494-8838
van der Werf, P.0000-0001-5434-5942
Neri, R.0000-0002-7176-4046
Armus, L.0000-0003-3498-2973
Additional Information:© ESO, 2015. Received 25 April 2015 / Accepted 27 July 2015. We thank the IRAM PdBI staff and the Nordic ALMA ARC node for excellent support. S.A. acknowledges partial support from the Swedish National Science Council grant 621-2011-4143. K.S. was supported by the MOST grant 102- 2119-M-001-011-MY3. This paper makes use of the following ALMA data: ADS/JAO.ALMA2012.1.00453.S and 2012.1.00817.S. Based on observations carried out with the IRAM Plateau de Bure and ALMA Interferometers. IRAM is supported by INSU/CNRS (France),MPG (Germany), and IGN (Spain). ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
Swedish National Science Council (NFR)621-2011-4143
Ministry of Science and Technology (Taipei)102- 2119-M-001-011-MY3
Subject Keywords:galaxies: evolution – galaxies: active – galaxies: nuclei – galaxies: ISM – ISM: molecules
Record Number:CaltechAUTHORS:20160115-163113572
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160115-163113572
Official Citation:Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN S. Aalto, S. Martín, F. Costagliola, E. González-Alfonso, S. Muller, K. Sakamoto, G. A. Fuller, S. García-Burillo, P. van der Werf, R. Neri, M. Spaans, F. Combes, S. Viti, S. Mühle, L. Armus, A. Evans, E. Sturm, J. Cernicharo, C. HenkelS. Aalto, S. Martín, F. Costagliola, E. González-Alfonso, S. Muller, K. Sakamoto, G. A. Fuller, S. García-Burillo, P. van der Werf, R. Neri, M. Spaans, F. Combes, S. Viti, S. Mühle, L. Armus, A. Evans, E. Sturm, J. Cernicharo, C. Henkel and T. R. Greve A&A, 584 (2015) A42 DOI: http://dx.doi.org/10.1051/0004-6361/201526410
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63730
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:19 Jan 2016 17:09
Last Modified:03 Oct 2019 09:31

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