Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN
Artikel i vetenskaplig tidskrift, 2015

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 (nu(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 x 10(13) L-circle dot kpc(-2). These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, nu(2) = 1, lines of HCN are excited by intense 14 mu m 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 (. = 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.

galaxies: evolution

galaxies: nuclei

galaxies: active



Susanne Aalto

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

S. Martin

Institut de RadioAstronomie Millimetrique (IRAM)

Francesco Costagliola

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

E. Gonzalez-Alfonso

Universidad de Alcala

Sebastien Muller

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

K. Sakamoto

Academia Sinica

G. A. Fuller

University of Manchester

S. G. Burillo

Observatorio Astronamico Nacional (OAN-IGN)

P. van der Werf

Universiteit Leiden

R. Neri

Institut de RadioAstronomie Millimetrique (IRAM)

M. Spaans

Rijksuniversiteit Groningen

F. Combes

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

S. Viti

University College London (UCL)

S. Muhle

Argelander-Institut für Astronomie

L. Armus

California Institute of Technology (Caltech)

A. Evans

National Radio Astronomy Observatory

University of Virginia

E. Sturm

Max Planck-institutet

J. Cernicharo

CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)

C. Henkel

King Abdulaziz University

Max Planck-institutet

T. R. Greve

University College London (UCL)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 584 A42

Molekyler som Diagnostiska Redskap för Aktiva och Skymda Galaxer

Vetenskapsrådet (VR), 2012-01-01 -- 2014-12-31.


Astronomi, astrofysik och kosmologi


Onsala rymdobservatorium



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