PROBING CIRCUMNUCLEAR ENVIRONMENTS WITH THE HCN(J = 3-2) AND HCO{sup +}(J = 3-2) LINES: CASE OF NGC 1097

Journal Article · Sat Mar 10 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/747/2/90· OSTI ID:22016267

Hsieh, Pei-Ying; Ho, Paul T. P.; Matsushita, Satoki ^[1]; Kohno, Kotaro ^[2]; Hwang, Chorng-Yuan ^[3]

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1. Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)
2. Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka-shi, Tokyo 181-0015 (Japan)
3. Institute of Astronomy, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan (China)

We present the first interferometric HCN(J = 3-2) and HCO{sup +}(J = 3-2) maps in the circumnuclear region of NGC 1097, obtained with the Submillimeter Array. The goal is to study the characteristics of the dense gas associated with the starburst ring/Seyfert nucleus. With these transitions, we suppress the diffuse low density emission in the nuclear region. We detect and resolve the individual compact giant molecular cloud associations (GMAs) in the 1.4 kpc circumnuclear starburst ring and within the 350 pc nuclear region. The nucleus is brighter than the ring in both lines, and contributes {approx}20% and {approx}30% to the total detected HCO{sup +}(J = 3-2) and HCN(J = 3-2) flux, within the central 1.4 kpc. The intensity ratios of HCN(J = 3-2)/HCO{sup +}(J = 3-2) are roughly unity in the GMAs of the starburst ring. However, this ratio is up to {approx}2 in the nuclear region. From the HCN(J = 3-2)/HCN(J = 1-0) ratio of {<=}0.2 in the nucleus, we infer that the nuclear HCN(J = 3-2) emission might be optically thin. The HCO{sup +}(J = 3-2) and HCN(J = 3-2) show correlations with {sup 12}CO(J = 3-2) and the 24 {mu}m emission. The tight correlations of HCN(J = 3-2), HCO{sup +}(J = 3-2), and 24 {mu}m emission in the starburst ring suggest that the dense molecular gas and the dust are from the same origins of star-forming regions. On the other hand, the HCN(J = 3-2) emission of the nucleus is significantly enhanced, indicating mechanisms other than star formation, such as active galactic nucleus activities. A self-consistent check of the fractional abundance enhanced by X-ray ionization chemistry of the nucleus is possible with our observations.

• OSTI ID: 22016267
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 747; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
DUSTS
GALAXIES
IONIZATION
MAPS
STARS