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23 April 2024 |
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Probing highly-obscured galaxy nuclei with vibrationally excited HCN - Extreme luminosity densities inside self-absorbed v=0 HCN and HCO+ | | S. Aalto
; S. Martin F. Costagliola
; E. Gonzalez-Alfonso
; S. Muller
; K. Sakamoto
; G. A. Fuller
; S. Garcia-Burillo
; P. van der Werf
; R. Neri
; M. Spaans
; F. Combes
; S. Viti
; S. Muehle
; L. Armus
; A. Evans
; E. Sturm
; J. Cernicharo
; C. Henkel
; T. R. Greve
; | | Date: |
26 Apr 2015 | | Abstract: | We present high resolution (0."4) IRAM PdBI and ALMA mm and submm
observations of the (Ultra) Luminous Infrared Galaxies ((U)LIRGs)
IRAS17208-0014, Arp220, IC860 and Zw049.057 that reveal intense line emission
from vibrationally excited (v2=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 >5e13 Lsun/kpc2. These nuclei are likely
powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K)
extreme starbursts. Vibrational, v2=1, lines of HCN are excited by intense 14
micron mid-infrared emission and are excellent probes of the dynamics, masses
and physical conditions of (U)LIRG nuclei when H2 column densities exceed 1e24
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,
the ground vibrational state (v=0), J=3-2 and 4-3 rotational lines of HCN and
HCO+ fail to probe the highly enshrouded, compact nuclear regions due 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. | | Source: | arXiv, 1504.6824 | | Services: | Forum | Review | PDF | Favorites | |
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