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Title: Extended gamma-ray emission from the G25.0+0.0 region: A star-forming region powered by the newly found OB association?

Abstract

We report a study of extended γ-ray emission with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, which is likely to be the second case of a γ-ray detection from a star-forming region (SFR) in our Galaxy. The LAT source is located in the G25 region, 1°7 × 2°1 around (l, b) = (25°0, 0°0). The γ-ray emission is found to be composed of two extended sources and one pointlike source. The extended sources have similar sizes of about 1°4 × 0fdg6. An ~0°4 diameter subregion of one has a photon index of Γ = 1.53 ± 0.15, and is spatially coincident with HESS J1837–069, likely a pulsar wind nebula. The other parts of the extended sources have a photon index of Γ = 2.1 ± 0.2 without significant spectral curvature. Given their spatial and spectral properties, they have no clear associations with sources at other wavelengths. Their γ-ray properties are similar to those of the Cygnus cocoon SFR, the only firmly established γ-ray detection of an SFR in the Galaxy. Indeed, we find bubble-like structures of atomic and molecular gas in G25, which may be created by a putative OB association/cluster. The γ-ray emitting regionsmore » appear confined in the bubble-like structure; similar properties are also found in the Cygnus cocoon. In addition, using observations with the XMM-Newton, we find a candidate young massive OB association/cluster G25.18+0.26 in the G25 region. Here, we propose that the extended γ-ray emission in G25 is associated with an SFR driven by G25.18+0.26. Based on this scenario, we discuss possible acceleration processes in the SFR and compare them with the Cygnus cocoon.« less

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3]
  1. Hiroshima Univ., Hiroshima (Japan)
  2. Rikkyo Univ., Tokyo (Japan)
  3. Erlangen Centre for Astroparticle Physics, Erlangen (Germany)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1355728
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 839; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; acceleration of particles; cosmic rays; gamma rays: ISM; ISM: bubbles; open clusters and associations: general; X-rays: stars

Citation Formats

Katsuta, J., Uchiyama, Y., and Funk, S.. Extended gamma-ray emission from the G25.0+0.0 region: A star-forming region powered by the newly found OB association?. United States: N. p., 2017. Web. doi:10.3847/1538-4357/aa6aa3.
Katsuta, J., Uchiyama, Y., & Funk, S.. Extended gamma-ray emission from the G25.0+0.0 region: A star-forming region powered by the newly found OB association?. United States. doi:10.3847/1538-4357/aa6aa3.
Katsuta, J., Uchiyama, Y., and Funk, S.. Thu . "Extended gamma-ray emission from the G25.0+0.0 region: A star-forming region powered by the newly found OB association?". United States. doi:10.3847/1538-4357/aa6aa3. https://www.osti.gov/servlets/purl/1355728.
@article{osti_1355728,
title = {Extended gamma-ray emission from the G25.0+0.0 region: A star-forming region powered by the newly found OB association?},
author = {Katsuta, J. and Uchiyama, Y. and Funk, S.},
abstractNote = {We report a study of extended γ-ray emission with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, which is likely to be the second case of a γ-ray detection from a star-forming region (SFR) in our Galaxy. The LAT source is located in the G25 region, 1°7 × 2°1 around (l, b) = (25°0, 0°0). The γ-ray emission is found to be composed of two extended sources and one pointlike source. The extended sources have similar sizes of about 1°4 × 0fdg6. An ~0°4 diameter subregion of one has a photon index of Γ = 1.53 ± 0.15, and is spatially coincident with HESS J1837–069, likely a pulsar wind nebula. The other parts of the extended sources have a photon index of Γ = 2.1 ± 0.2 without significant spectral curvature. Given their spatial and spectral properties, they have no clear associations with sources at other wavelengths. Their γ-ray properties are similar to those of the Cygnus cocoon SFR, the only firmly established γ-ray detection of an SFR in the Galaxy. Indeed, we find bubble-like structures of atomic and molecular gas in G25, which may be created by a putative OB association/cluster. The γ-ray emitting regions appear confined in the bubble-like structure; similar properties are also found in the Cygnus cocoon. In addition, using observations with the XMM-Newton, we find a candidate young massive OB association/cluster G25.18+0.26 in the G25 region. Here, we propose that the extended γ-ray emission in G25 is associated with an SFR driven by G25.18+0.26. Based on this scenario, we discuss possible acceleration processes in the SFR and compare them with the Cygnus cocoon.},
doi = {10.3847/1538-4357/aa6aa3},
journal = {The Astrophysical Journal (Online)},
number = 2,
volume = 839,
place = {United States},
year = {Thu Apr 20 00:00:00 EDT 2017},
month = {Thu Apr 20 00:00:00 EDT 2017}
}

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