An Enigmatic PeVatron in an Area around H ii Region G35.6−0.5

Issued Date

2025-01-20

Resource Type

Article

ISSN

0004637X

eISSN

15384357

DOI

10.3847/1538-4357/ad991d

Scopus ID

2-s2.0-85216125175

Journal Title

Astrophysical Journal

Volume

979

Issue

1

Rights Holder(s)

SCOPUS

Bibliographic Citation

Astrophysical Journal Vol.979 No.1 (2025)

Suggested Citation

Cao Z., Aharonian F., Axikegu, Bai Y.X., Bao Y.W., Bastieri D., Bi X.J., Bi Y.J., Bian W., Bukevich A.V., Cao Q., Cao W.Y., Cao Z., Chang J., Chang J.F., Chen A.M., Chen B.Q., Chen E.S., Chen H.X., Chen L., Chen L., Chen L., Chen M.J., Chen M.L., Chen Q.H., Chen S., Chen S.H., Chen S.Z., Chen T.L., Chen Y., Cheng N., Cheng Y.D., Chu M.C., Cui M.Y., Cui S.W., Cui X.H., Cui Y.D., Dai B.Z., Dai H.L., Dai Z.G., Danzengluobu, Dong X.Q., Duan K.K., Fan J.H., Fan Y.Z., Fang J., Fang J.H., Fang K., Feng C.F., Feng H., Feng L., Feng S.H., Feng X.T., Feng Y., Feng Y.L., Gabici S., Gao B., Gao C.D., Gao Q., Gao W., Gao W.K., Ge M.M., Ge T.T., Geng L.S., Giacinti G., Gong G.H., Gou Q.B., Gu M.H., Guo F.L., Guo J., Guo X.L., Guo Y.Q., Guo Y.Y., Han Y.A., Hannuksela O.A., Hasan M., He H.H., He H.N., He J.Y., He Y., Hor Y.K., Hou B.W., Hou C., Hou X., Hu H.B., Hu Q., Hu S.C., Huang C., Huang D.H., Huang T.Q., Huang W.J., Huang X.T., Huang X.Y., Huang Y., Huang Y.Y., Ji X.L., Jia H.Y., Jia K., Jiang H.B., Jiang K. An Enigmatic PeVatron in an Area around H ii Region G35.6−0.5. Astrophysical Journal Vol.979 No.1 (2025). doi:10.3847/1538-4357/ad991d Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/103149

Title

An Enigmatic PeVatron in an Area around H ii Region G35.6−0.5

Author(s)

Cao Z.
 Aharonian F.
 Axikegu
 Bai Y.X.
 Bao Y.W.
 Bastieri D.
 Bi X.J.
 Bi Y.J.
 Bian W.
 Bukevich A.V.
 Cao Q.
 Cao W.Y.
 Cao Z.
 Chang J.
 Chang J.F.
 Chen A.M.
 Chen B.Q.
 Chen E.S.
 Chen H.X.
 Chen L.
 Chen L.
 Chen L.
 Chen M.J.
 Chen M.L.
 Chen Q.H.
 Chen S.
 Chen S.H.
 Chen S.Z.
 Chen T.L.
 Chen Y.
 Cheng N.
 Cheng Y.D.
 Chu M.C.
 Cui M.Y.
 Cui S.W.
 Cui X.H.
 Cui Y.D.
 Dai B.Z.
 Dai H.L.
 Dai Z.G.
 Danzengluobu
 Dong X.Q.
 Duan K.K.
 Fan J.H.
 Fan Y.Z.
 Fang J.
 Fang J.H.
 Fang K.
 Feng C.F.
 Feng H.
 Feng L.
 Feng S.H.
 Feng X.T.
 Feng Y.
 Feng Y.L.
 Gabici S.
 Gao B.
 Gao C.D.
 Gao Q.
 Gao W.
 Gao W.K.
 Ge M.M.
 Ge T.T.
 Geng L.S.
 Giacinti G.
 Gong G.H.
 Gou Q.B.
 Gu M.H.
 Guo F.L.
 Guo J.
 Guo X.L.
 Guo Y.Q.
 Guo Y.Y.
 Han Y.A.
 Hannuksela O.A.
 Hasan M.
 He H.H.
 He H.N.
 He J.Y.
 He Y.
 Hor Y.K.
 Hou B.W.
 Hou C.
 Hou X.
 Hu H.B.
 Hu Q.
 Hu S.C.
 Huang C.
 Huang D.H.
 Huang T.Q.
 Huang W.J.
 Huang X.T.
 Huang X.Y.
 Huang Y.
 Huang Y.Y.
 Ji X.L.
 Jia H.Y.
 Jia K.
 Jiang H.B.
 Jiang K.

Author's Affiliation

Zhejiang Lab
 State Key Laboratory of Particle Detection & Electronics
 Université Paris Cité
 Yunnan Observatories
 Nanjing University
 Shanghai Astronomical Observatory Chinese Academy of Sciences
 Institute for Nuclear Research of the Russian Academy of Sciences
 Shandong University
 Yunnan University
 Institute of High Energy Physics, Chinese Academy of Sciences
 University of Chinese Academy of Sciences
 Guangzhou University
 Tsinghua University
 Shanghai Jiao Tong University
 Sun Yat-Sen University
 University of Science and Technology of China
 Zhengzhou University
 Institiúid Ard-Lénn Bhaile Átha Cliath
 National Astronomical Observatories Chinese Academy of Sciences
 Max-Planck-Institut für Kernphysik
 Southwest Jiaotong University
 China Center of Advanced Science and Technology World Laboratory
 Purple Mountain Observatory Chinese Academy of Sciences
 Chinese University of Hong Kong
 Hebei Normal University
 Tibet University
 TIANFU Cosmic Ray Research Center

Corresponding Author(s)

Cao Z.

Other Contributor(s)

Mahidol University

Abstract

Identifying Galactic PeVatrons (PeV particle accelerators) from ultrahigh-energy (UHE, >100 TeV) γ-ray sources plays a crucial role in revealing the origin of Galactic cosmic rays. The UHE source 1LHAASO J1857+0203u is suggested to be associated with HESS J1858+020, which may be attributed to the possible PeVatron candidate supernova remnant (SNR) G35.6−0.4 or H ii region G35.6−0.5. We perform detailed analysis on the very-high-energy and UHE γ-ray emissions toward this region with data from the Large High Altitude Air Shower Observatory (LHAASO). 1LHAASO J1857+0203u is detected with a significance of 11.6σ above 100 TeV, indicating the presence of a PeVatron. It has an extent of ∼0 . ° 18 with a power-law (PL) spectral index of ∼2.5 at 1-25 TeV and pointlike emission with a PL spectral index of ∼3.2 above 25 TeV. Using archival CO and H i data, we identify some molecular and atomic clouds that may be associated with the TeV γ-ray emissions. Our modeling indicates that the TeV γ-ray emissions are unlikely to arise from clouds illuminated by the protons that escaped from SNR G35.6−0.4. In the scenario in which H ii region G35.6−0.5 could accelerate particles to the UHE band, the observed GeV-TeV γ-ray emission could be well explained by a hadronic model with a PL spectral index of ∼2.0 and cutoff energy of ∼450 TeV. However, an origin in an evolved pulsar wind nebula cannot be ruled out.

Keyword(s)

Earth and Planetary Sciences
 Physics and Astronomy

Availability

URI

https://repository.li.mahidol.ac.th/handle/20.500.14594/103149

Collections

Scopus 2025