Vibrationally excited HCN in the luminous infrared galaxy NGC 4418
Artikel i vetenskaplig tidskrift, 2010

Infrared pumping and its effect on the excitation of HCN molecules can be important when using rotational lines of HCN to probe dense molecular gas in galaxy nuclei. We report the first extragalactic detection of (sub)millimeter rotational lines of vibrationally excited HCN, in the dust-enshrouded nucleus of the luminous infrared galaxy NGC 4418. We estimate the excitation temperature of T-vib approximate to 230 K between the vibrational ground and excited (v(2) = 1) states. This excitation is most likely due to infrared radiation. At this high vibrational temperature the path through the v(2) = 1 state must have a strong impact on the rotational excitation in the vibrational ground level, although it may not be dominant for all rotational levels. Our observations also revealed nearly confusion-limited lines of CO, HCN, HCO+, (HCN)-C-13, (HCN)-N-15, CS, N2H+, and HC3N at lambda similar to 1 mm. Their relative intensities may also be affected by the infrared pumping.

galaxies: ISM

co

temperature-dependence

galaxies: individual (NGC 4418)

dust

hco+

ngc-4418

excitation

vib-rotational transitions

star-formation

galaxies: active

molecular gas

einstein a-coefficients

Författare

K. Sakamoto

Institute of Astrophysics and Astronomy, Academia Sinica Taiwan

Susanne Aalto

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

A. S. Evans

University of Virginia

National Radio Astronomy Observatory

M. C. Wiedner

L'Observatoire de Paris

D. J. Wilner

Harvard-Smithsonian Center for Astrophysics

Astrophysical Journal Letters

2041-8205 (ISSN) 2041-8213 (eISSN)

Vol. 725 L228-L233

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1088/2041-8205/725/2/L228