Measurement of Very-High-Energy Diffuse Gamma-Ray Emissions from the Galactic Plane with LHAASO-WCDA

Issued Date

2025-02-28

Resource Type

Article

ISSN

00319007

eISSN

10797114

DOI

10.1103/PhysRevLett.134.081002

Scopus ID

2-s2.0-85219749003

Journal Title

Physical Review Letters

Volume

134

Issue

8

Rights Holder(s)

SCOPUS

Bibliographic Citation

Physical Review Letters Vol.134 No.8 (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 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., Jiang X.W. Measurement of Very-High-Energy Diffuse Gamma-Ray Emissions from the Galactic Plane with LHAASO-WCDA. Physical Review Letters Vol.134 No.8 (2025). doi:10.1103/PhysRevLett.134.081002 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/106673

Title

Measurement of Very-High-Energy Diffuse Gamma-Ray Emissions from the Galactic Plane with LHAASO-WCDA

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 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.
 Jiang X.W.

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

The diffuse Galactic gamma-ray emission is a very important tool used to study the propagation and interaction of cosmic rays in the Milky Way. In this Letter, we report the measurements of the diffuse emission from the Galactic plane - covering Galactic longitudes from 15° to 235° and latitudes from -5° to +5°, in an energy range of 1 to 25 TeV - made with the Water Cherenkov Detector Array (WCDA) of the Large High Altitude Air Shower Observatory. After the sky regions of known sources are masked, the diffuse emission is detected with 24.6σ and 9.1σ significance in the inner Galactic plane (15°<l<125°, |b|<5°) and outer Galactic plane (125°<l<235°, |b|<5°), respectively. The WCDA spectra in both regions can be well described by a power-law function, with spectral indices of -2.67±0.05stat in the inner region and -2.83±0.19stat in the outer region, respectively. Combined with the Square Kilometer Array (KM2A) measurements at higher energies, a clear softening of the spectrum is found in the inner region, with change of spectral indices by ∼0.5 at a break energy around 30 TeV. The fluxes of the diffuse emission are higher by a factor of 1.5-2.7 than the model prediction assuming local cosmic ray spectra and the gas column density, which are consistent with those measured by the KM2A. Along the Galactic longitude, the spatial distribution of the diffuse emission shows deviation from that of the gas column density. The spectral shape of the diffuse emission may vary in different longitude regions. The WCDA measurements bridge the gap between the low-energy measurements by space detectors and the ultra-high-energy observations by KM2A and other experiments. These results suggest that improved modeling of the wideband diffuse emission is required.

Keyword(s)

Physics and Astronomy

Availability

URI

https://repository.li.mahidol.ac.th/handle/123456789/106673

Collections

Scopus 2025