TY - JOUR AU - Aalto, S. AU - Martin, S. AU - Costagliola, F. AU - Gonzalez-Alfonso, E. AU - Muller, S. AU - Sakamoto, K. AU - Fuller, G.A. AU - Garcia-Burillo, S. AU - Van Der Werf, P. AU - Neri, R. AU - Spaans, M. AU - Combes, F. AU - Viti, S. AU - Muhle, S. AU - Armus, L. AU - Evans, A. AU - Sturm, E. AU - Cernicharo, J. AU - Henkel, C. AU - Greve, T.R. T1 - Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN LA - eng PY - 2015/12/01/ T2 - Astronomy and Astrophysics SN - 1432-0746 VL - 584 PB - EDP Sciences AB - 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 (ν2 = 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 × 1013 L? kpc-2. These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, ν2 = 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 H2 column densities exceed 1024 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 = 3-2and 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. DO - 10.1051/0004-6361/201526410 UR - https://portalcientifico.uah.es/documentos/61578fe0d3e35f5001a23c4f DP - Dialnet - Portal de la Investigación ER -