VIBRATIONALLY EXCITED HCN IN THE LUMINOUS INFRARED GALAXY NGC 4418

Journal Article · Mon Dec 20 04:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/725/2/L228· OSTI ID:21454875

Sakamoto, Kazushi ^[1]; Aalto, Susanne ^[2]; Evans, Aaron S ^[3]; Wiedner, Martina C ^[4]

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1. Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan (China)
2. Onsala Space Observatory, Onsala (Sweden)
3. Department of Astronomy, University of Virginia, Charlottesville, VA (United States)
4. Observatoire de Paris, Paris (France)

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{sub vib} {approx} 230 K between the vibrational ground and excited (v{sub 2} = 1) states. This excitation is most likely due to infrared radiation. At this high vibrational temperature the path through the v{sub 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{sup +}, H{sup 13}CN, HC{sup 15}N, CS, N{sub 2}H{sup +}, and HC{sub 3}N at {lambda} {approx} 1 mm. Their relative intensities may also be affected by the infrared pumping.

• OSTI ID: 21454875
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 725; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
ELECTROMAGNETIC RADIATION
ENERGY-LEVEL TRANSITIONS
EXCITATION
GALAXIES
GALAXY NUCLEI
HYDROCYANIC ACID
HYDROGEN COMPOUNDS
INFRARED RADIATION
INORGANIC ACIDS
INORGANIC COMPOUNDS
NITRILES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS