Miguel Pereira-Santaella, Eduardo González-Alfonso, Ismael García-Bernete, Fergus R. Donnan, Miriam G. Santa-Maria, Javier R. Goicoechea, Isabella Lamperti, Michele Perna, Dimitra Rigopoulou
{"title":"利用 JWST/NIRSpec 对当地 (U)LIRG 中 H3+ 的吸收和发射进行研究:高H2电离率的证据","authors":"Miguel Pereira-Santaella, Eduardo González-Alfonso, Ismael García-Bernete, Fergus R. Donnan, Miriam G. Santa-Maria, Javier R. Goicoechea, Isabella Lamperti, Michele Perna, Dimitra Rigopoulou","doi":"10.1051/0004-6361/202451741","DOIUrl":null,"url":null,"abstract":"We study the 3.4 − 4.4 μm fundamental rovibrational band of H<sub>3<sub/><sup>+<sup/>, a key tracer of the ionization of the molecular interstellar medium (ISM), in a sample of 12 local (<i>d<i/> < 400 Mpc) (ultra)luminous infrared galaxies ((U)LIRGs) observed with JWST/NIRSpec. The <i>P<i/>, <i>Q<i/>, and <i>R<i/> branches of the band are detected in 13 out of 20 analyzed regions within these (U)LIRGs, which increases the number of extragalactic H<sub>3<sub/><sup>+<sup/> detections by a factor of 6. For the first time in the ISM, the H<sub>3<sub/><sup>+<sup/> band is observed in emission; we detect this emission in three regions. In the remaining ten regions, the band is seen in absorption. The absorptions are produced toward the 3.4 − 4.4 μm hot dust continuum rather than toward the stellar continuum, indicating that they likely originate in clouds associated with the dust continuum source. The H<sub>3<sub/><sup>+<sup/> band is undetected in Seyfert-like (U)LIRGs where the mildly obscured X-ray radiation from the active galactic nuclei might limit the abundance of this molecule. For the detections, the H<sub>3<sub/><sup>+<sup/> abundances, <i>N<i/>(H<sub>3<sub/><sup>+<sup/>)/<i>N<i/><sub>H<sub/> = (0.5 − 5.5)×10<sup>−7<sup/>, imply relatively high ionization rates, <i>ζ<i/><sub>H<sub>2<sub/><sub/>, of between 3 × 10<sup>−16<sup/> and > 4 × 10<sup>−15<sup/> s<sup>−1<sup/>, which are likely associated with high-energy cosmic rays. In half of the targets, the absorptions are blueshifted by 50–180 km s<sup>−1<sup/>, which is lower than the molecular outflow velocities measured using other tracers such as OH 119 μm or rotational CO lines. This suggests that H<sub>3<sub/><sup>+<sup/> traces gas close to the outflow-launching sites before it has been fully accelerated. We used nonlocal thermodynamic equilibrium models to investigate the physical conditions of these clouds. In seven out of ten objects, the H<sub>3<sub/><sup>+<sup/> excitation is consistent with inelastic collisions with H<sub>2<sub/> in warm translucent molecular clouds (<i>T<i/><sub>kin<sub/> ∼ 250–500 K and <i>n<i/>(H<sub>2<sub/>) ∼10<sup>2 − 3<sup/> cm<sup>−3<sup/>). In three objects, dominant infrared pumping excitation is required to explain the absorptions from the (3,0) and (2,1) levels of H<sub>3<sub/><sup>+<sup/> detected for the first time in the ISM.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":5.4000,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"H3+ absorption and emission in local (U)LIRGs with JWST/NIRSpec: Evidence for high H2 ionization rates\",\"authors\":\"Miguel Pereira-Santaella, Eduardo González-Alfonso, Ismael García-Bernete, Fergus R. Donnan, Miriam G. Santa-Maria, Javier R. Goicoechea, Isabella Lamperti, Michele Perna, Dimitra Rigopoulou\",\"doi\":\"10.1051/0004-6361/202451741\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We study the 3.4 − 4.4 μm fundamental rovibrational band of H<sub>3<sub/><sup>+<sup/>, a key tracer of the ionization of the molecular interstellar medium (ISM), in a sample of 12 local (<i>d<i/> < 400 Mpc) (ultra)luminous infrared galaxies ((U)LIRGs) observed with JWST/NIRSpec. The <i>P<i/>, <i>Q<i/>, and <i>R<i/> branches of the band are detected in 13 out of 20 analyzed regions within these (U)LIRGs, which increases the number of extragalactic H<sub>3<sub/><sup>+<sup/> detections by a factor of 6. For the first time in the ISM, the H<sub>3<sub/><sup>+<sup/> band is observed in emission; we detect this emission in three regions. In the remaining ten regions, the band is seen in absorption. The absorptions are produced toward the 3.4 − 4.4 μm hot dust continuum rather than toward the stellar continuum, indicating that they likely originate in clouds associated with the dust continuum source. The H<sub>3<sub/><sup>+<sup/> band is undetected in Seyfert-like (U)LIRGs where the mildly obscured X-ray radiation from the active galactic nuclei might limit the abundance of this molecule. For the detections, the H<sub>3<sub/><sup>+<sup/> abundances, <i>N<i/>(H<sub>3<sub/><sup>+<sup/>)/<i>N<i/><sub>H<sub/> = (0.5 − 5.5)×10<sup>−7<sup/>, imply relatively high ionization rates, <i>ζ<i/><sub>H<sub>2<sub/><sub/>, of between 3 × 10<sup>−16<sup/> and > 4 × 10<sup>−15<sup/> s<sup>−1<sup/>, which are likely associated with high-energy cosmic rays. In half of the targets, the absorptions are blueshifted by 50–180 km s<sup>−1<sup/>, which is lower than the molecular outflow velocities measured using other tracers such as OH 119 μm or rotational CO lines. This suggests that H<sub>3<sub/><sup>+<sup/> traces gas close to the outflow-launching sites before it has been fully accelerated. We used nonlocal thermodynamic equilibrium models to investigate the physical conditions of these clouds. In seven out of ten objects, the H<sub>3<sub/><sup>+<sup/> excitation is consistent with inelastic collisions with H<sub>2<sub/> in warm translucent molecular clouds (<i>T<i/><sub>kin<sub/> ∼ 250–500 K and <i>n<i/>(H<sub>2<sub/>) ∼10<sup>2 − 3<sup/> cm<sup>−3<sup/>). In three objects, dominant infrared pumping excitation is required to explain the absorptions from the (3,0) and (2,1) levels of H<sub>3<sub/><sup>+<sup/> detected for the first time in the ISM.\",\"PeriodicalId\":8571,\"journal\":{\"name\":\"Astronomy & Astrophysics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":5.4000,\"publicationDate\":\"2024-09-26\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Astronomy & Astrophysics\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://doi.org/10.1051/0004-6361/202451741\",\"RegionNum\":2,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"ASTRONOMY & ASTROPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Astronomy & Astrophysics","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1051/0004-6361/202451741","RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ASTRONOMY & ASTROPHYSICS","Score":null,"Total":0}
H3+ absorption and emission in local (U)LIRGs with JWST/NIRSpec: Evidence for high H2 ionization rates
We study the 3.4 − 4.4 μm fundamental rovibrational band of H3+, a key tracer of the ionization of the molecular interstellar medium (ISM), in a sample of 12 local (d < 400 Mpc) (ultra)luminous infrared galaxies ((U)LIRGs) observed with JWST/NIRSpec. The P, Q, and R branches of the band are detected in 13 out of 20 analyzed regions within these (U)LIRGs, which increases the number of extragalactic H3+ detections by a factor of 6. For the first time in the ISM, the H3+ band is observed in emission; we detect this emission in three regions. In the remaining ten regions, the band is seen in absorption. The absorptions are produced toward the 3.4 − 4.4 μm hot dust continuum rather than toward the stellar continuum, indicating that they likely originate in clouds associated with the dust continuum source. The H3+ band is undetected in Seyfert-like (U)LIRGs where the mildly obscured X-ray radiation from the active galactic nuclei might limit the abundance of this molecule. For the detections, the H3+ abundances, N(H3+)/NH = (0.5 − 5.5)×10−7, imply relatively high ionization rates, ζH2, of between 3 × 10−16 and > 4 × 10−15 s−1, which are likely associated with high-energy cosmic rays. In half of the targets, the absorptions are blueshifted by 50–180 km s−1, which is lower than the molecular outflow velocities measured using other tracers such as OH 119 μm or rotational CO lines. This suggests that H3+ traces gas close to the outflow-launching sites before it has been fully accelerated. We used nonlocal thermodynamic equilibrium models to investigate the physical conditions of these clouds. In seven out of ten objects, the H3+ excitation is consistent with inelastic collisions with H2 in warm translucent molecular clouds (Tkin ∼ 250–500 K and n(H2) ∼102 − 3 cm−3). In three objects, dominant infrared pumping excitation is required to explain the absorptions from the (3,0) and (2,1) levels of H3+ detected for the first time in the ISM.
期刊介绍:
Astronomy & Astrophysics is an international Journal that publishes papers on all aspects of astronomy and astrophysics (theoretical, observational, and instrumental) independently of the techniques used to obtain the results.