FIRST EXTRAGALACTIC DETECTION OF SUBMILLIMETER CH ROTATIONAL LINES FROM THE HERSCHEL SPACE OBSERVATORY

被引：12

作者：

Rangwala, Naseem ^{[1
,2
]}

Maloney, Philip R. ^{[1
]}

Glenn, Jason ^{[1
]}

Wilson, Christine D. ^{[3
]}

Kamenetzky, Julia ^{[1
]}

Schirm, Maximilien R. P. ^{[3
]}

Spinoglio, Luigi ^{[4
]}

Santaella, Miguel Pereira ^{[4
]}

机构：

[1] Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80303 USA

[2] NASA, Ames Res Ctr, Space Sci & Astrobiol Div, Moffett Field, CA 94035 USA

[3] McMaster Univ, Dept Phys & Astron, Hamilton, ON L8S 4M1, Canada

[4] INAF, Ist Fis Spazio Interplanetario, I-00133 Rome, Italy

来源：

ASTROPHYSICAL JOURNAL | 2014年 / 788卷 / 02期

关键词：

galaxies: ISM; galaxies: starburst; ISM: molecules; line: identification; techniques: spectroscopic; DIFFUSE INTERSTELLAR-MEDIUM; STAR-FORMING REGIONS; MOLECULAR GAS; ABSORPTION-LINES; NGC; 1068; CLOUDS; SPIRE; EMISSION; SPECTRUM; ARP-220;

D O I：

10.1088/0004-637X/788/2/147

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We present the first extragalactic detections of several CH rotational transitions in the far-infrared in four nearby galaxies, NGC 1068, Arp 220, M82, and NGC 253, using the Herschel Space Observatory. The CH lines in all four galaxies are a factor of 2-4 brighter than the adjacent HCN and HCO+ J = 6-5 lines (also detected in the same spectra). In the star-formation-dominated galaxies, M82, NGC 253, and Arp 220, the CH/CO abundance ratio is low (similar to 10(-5)), implying that the CH is primarily arising in diffuse and translucent gas where the chemistry is driven by UV radiation as found in the Milky Way interstellar matter. In NGC 1068, which has a luminous active galactic nucleus (AGN), the CH/CO ratio is an order of magnitude higher, suggesting that CH formation is driven by an X-ray-dominated region (XDR). Our XDR models show that both the CH and CO abundances in NGC 1068 can be explained by an XDR-driven chemistry for gas densities and molecular hydrogen column densities that are well constrained by the CO observations. We conclude that the CH/CO ratio may a good indicator of the presence of AGN in galaxies. We also discuss the feasibility of detecting CH in intermediate-to high-z galaxies with ALMA.

引用

页数：9

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