Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
| Autor: | de la Fuente, Eduardo, Toledano-Juárez, Iván, Kawata, Kazumasa, Trinidad, Miguel A., Tafoya, Daniel, Sano, Hidetoshi, Tokuda, Kazuki, Nishimura, Atsushi, Onishi, Toshikazu, Sako, Takashi, Hona, Binita, Ohnishi, Munehiro, Takita, Masato |
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| Rok vydání: | 2023 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/pasj/psad018 |
| Popis: | PeVatrons are the most powerful naturally occurring particle accelerators in the Universe. The identification of counterparts associated to astrophysical objects such as dying massive stars, molecular gas, star-forming regions, and star clusters is essential to clarify the underlying nature of the PeV emission, i.e., hadronic or leptonic. We present $^{12,13}$CO(J=2$\rightarrow$1) observations made with the 1.85~m radio-telescope of the Osaka Prefecture University toward the Cygnus OB7 molecular cloud, which contains the PeVatron candidate LHAASO J2108+5157. We investigate the nature of the sub-PeV (gamma-ray) emission by studying the nucleon density determined from the content of HI and H$_2$, derived from the CO observations. In addition to MML[2017]4607, detected via the observations of the optically thick $^{12}$CO(J=1$\rightarrow$0) emission, we infer the presence of an optically thin molecular cloud, named [FKT-MC]2022, whose angular size is 1.1$\pm$0.2$^{\circ}$. We propose this cloud as a new candidate to produce the sub-PeV emission observed in LHAASO J2108+5157. Considering a distance of 1.7 kpc, we estimate a nucleon (HI+H$_2$) density of 37$\pm$14 cm$^{-3}$, and a total nucleon mass(HI+H$_2$) of 1.5$\pm$0.6$\times$10$^4$ M$_{\odot}$. On the other hand, we confirm that Kronberger 82 is a molecular clump with an angular size of 0.1$^{\circ}$, a nucleon density $\sim$ 10$^3$ cm$^{-3}$, and a mass $\sim$ 10$^3$ M$_{\odot}$. Although Kronberger 82 hosts the physical conditions to produce the observed emission of LHAASO J2108+5157, [FKT-MC]2022 is located closer to it, suggesting that the latter could be the one associated to the sub-PeV emission. Under this scenario, our results favour a hadronic origin for the emission. Comment: Accepted for publication in Publications of the Astronomical Society of Japan (PASJ). Accepted on 06-Mar-2023. DOI: https://doi.org/10.1093/pasj/psad018 20 pages, 12 figures, 12 tables |
| Databáze: | arXiv |
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