SUBMILLIMETER-HCN DIAGRAM FOR ENERGY DIAGNOSTICS IN THE CENTERS OF GALAXIES

被引：60

作者：

Izumi, Takuma ^{[1
]}

Kohno, Kotaro ^{[1
,2
]}

Aalto, Susanne ^{[3
]}

Espada, Daniel ^{[4
,5
,6
]}

Fathi, Kambiz ^{[7
]}

Harada, Nanase ^{[8
]}

Hatsukade, Bunyo ^{[5
]}

Hsieh, Pei-Ying ^{[8
,9
]}

Imanishi, Masatoshi ^{[5
,6
,10
]}

Krips, Melanie ^{[11
]}

Martin, Sergio ^{[4
,11
,12
]}

Matsushita, Satoki ^{[8
]}

Meier, David S. ^{[13
]}

Nakai, Naomasa ^{[14
]}

Nakanishi, Kouichiro ^{[4
,5
,6
]}

Schinnerer, Eva ^{[15
]}

Sheth, Kartik ^{[16
]}

Terashima, Yuichi ^{[17
]}

Turner, Jean L. ^{[18
]}

机构：

[1] Univ Tokyo, Inst Astron, Sch Sci, 2-21-1 Osawa, Tokyo 1810015, Japan

[2] Univ Tokyo, Res Ctr Early Universe, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1130033, Japan

[3] Chalmers Univ Technol, Dept Earth & Space Sci, Onsala Observ, SE-43994 Onsala, Sweden

[4] Joint ALMA Observ, Alonso de Cordova 3107, Santiago 7630355, Chile

[5] Natl Astron Observ Japan, 2-21-1 Osawa, Mitaka, Tokyo 1818588, Japan

[6] SOKENDAI Grad Univ Adv Studies, 2-21-1 Osawa, Mitaka, Tokyo 1818588, Japan

[7] Stockholm Univ, Dept Astron, AlbaNova Ctr, Stockholm Observ, SE-10691 Stockholm, Sweden

[8] Acad Sinica, Inst Astron & Astrophys, POB 23-141, Taipei 10617, Taiwan

[9] Natl Cent Univ, Inst Astron, 300 Jhongda Rd, Jhongli 32001, Taoyuan County, Taiwan

[10] NAOJ, Subaru Telescope, 650 N Aohoku Pl, Hilo, HI 96720 USA

[11] Inst Radio Astron Millimetr, 300 Rue Piscine, F-38406 St Martin Dheres, France

[12] European So Observ, Alonso de Cordova 3107, Santiago, Chile

[13] New Mexico Inst Min & Technol, Dept Phys, 801 Leroy Pl, Soccoro, NM 87801 USA

[14] Univ Tsukuba, Fac Pure & Appl Sci, Dept Phys, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 3058571, Japan

[15] Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany

[16] NASA, 300 E St SW, Washington, DC 20546 USA

[17] Ehime Univ, Dept Phys, 2-5 Bunkyo Cho, Matsuyama, Ehime 7908577, Japan

[18] UCLA, Dept Phys & Astron, 430 Portola Plaza, Los Angeles, CA 90095 USA

来源：

ASTROPHYSICAL JOURNAL | 2016年 / 818卷 / 01期

基金：

日本学术振兴会;

关键词：

galaxies: active; galaxies: ISM; ISM: molecules; DENSE MOLECULAR GAS; LARGE-MAGELLANIC-CLOUD; LUMINOUS INFRARED GALAXIES; ACTIVE GALACTIC NUCLEI; VIBRATIONALLY EXCITED HCN; YOUNG STELLAR OBJECTS; H II REGIONS; PHOTON-DOMINATED REGIONS; XMM-NEWTON OBSERVATIONS; MASSIVE STAR-FORMATION;

D O I：

10.3847/0004-637X/818/1/42

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Compiling data from literature and the Atacama Large Millimeter/submillimeter Array archive, we show enhanced HCN(4-3)/HCO+(4-3) and/or HCN(4-3)/CS(7-6) integrated intensity ratios in circumnuclear molecular gas around active galactic nuclei (AGNs) compared to those in starburst (SB) galaxies (submillimeter HCN. enhancement). The number of sample galaxies is significantly increased from our previous work. We expect that this feature could potentially be an extinction-free energy diagnostic tool of nuclear regions of galaxies. Non-LTE radiative transfer modelings of the above molecular emission lines involving both collisional and radiative excitation, as well as a photon trapping effect, were conducted to investigate the cause of the high line ratios in AGNs. As a result, we found that enhanced abundance ratios of HCN to HCO+ and HCN to CS in AGNs as compared to SB galaxies by a factor of a few to even greater than or similar to 10 are a plausible explanation for the submillimeter HCN. enhancement. However, a counterargument of a systematically higher gas density in AGNs than in SB galaxies can also be a plausible scenario. Although we cannot fully distinguish. these two scenarios at this moment owing to an insufficient amount of multi-transition, multi-species data, the former scenario is indicative of abnormal chemical composition in AGNs. Regarding the actual mechanism to realize the composition, we suggest that it is difficult with conventional gas-phase X-ray-dominated region ionization models to reproduce the observed high line ratios. We might have to take into account other mechanisms such as neutral-neutral reactions that are efficiently activated in high-temperature environments and/or mechanically heated regions to further understand the high line ratios in AGNs.

引用

页数：23

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