| Canonical Name: | HESS J1858+020 |
| TeVCat Name: | TeV J1858+020 |
| Other Names: | 1HWC J1857+023 |
| Source Type: | UNID |
| R.A.: | 18 58 20 (hh mm ss) |
| Dec.: | +02 05 24 (dd mm ss) |
| Gal Long: | 35.58 (deg) |
| Gal Lat: | -0.58 (deg) |
| Distance: | |
| Flux: | (Crab Units) |
| Energy Threshold: | GeV |
| Spectral Index: | 2.17 |
| Extended: | Yes |
| Size (X): | 0.08 (deg) |
| Size (Y): | 0.02 (deg) |
| Discovery Date: | 2007-07 |
| Discovered By: | H.E.S.S. |
| TeVCat SubCat: | Default Catalog |
Source Notes:
| H.E.S.S. Galactic Plane Survey (HGPS, 2018): |
| A selection of information for each of the 78 sources in the HGPS is provided in TeVCat. For full details, visit the HGPS website. |
| Name: | HESS J1858+020 |
| Source Class: | Unid |
| Identified Object: | None |
| R.A. (J2000): | 284.57 deg (18 58 16) |
| Dec. (J2000): | 2.06 deg (02 03 35) |
| Positional uncertainty: | 0.042 deg |
| Spatial Model: | Gaussian |
| Size: | 0.079 +/- 0.016 deg |
| Spectral Model: | power law |
| Integral Flux > 1 TeV: | 4.68e-13 +/- 6.43e-14 cm-2 s-1 |
| Pivot Energy, E0: | 1.27 TeV |
| Diff. Flux at E0: | 3.65e-13 +/- 4.54e-14 cm-2 s-1 TeV-1 |
| Spectral Index: | 2.39 +/- 0.12 |
| HGPS Source Notes: | |
| | |
This is one of eleven HGPS sources that "do not have any associations with known physical objects, although some are associated
with HE gamma-ray sources."
One possible association is listed in Table A.9. "This is a list of astronomical objects, extracted from catalogs of plausible counterparts, which are are found to be spatially coincident with the HGPS source":
- 3FGL J1857.9+0210 (3FGL)
Source position and its uncertainty:
From
Aharonian et al. (2008):
- R.A. (J2000): 18 58 20
- Dec. (J2000): 02 05 24
- The fit position has a statistical error of 0.05 deg
Source Association:
From
Cui et al. (2021):
- "The supernova remnant (SNR) G35.6-0.4 shows a non-thermal radio
shell, however, no gamma-ray or X-ray counterparts have been found for
it thus far. One TeV source, HESS J1858+020, was found near the SNR
and this source is spatially associated with some clouds at 3.6 kpc."
- "To attain a better understanding of the origin of HESS J1858+020,
we further investigate the association between SNR cosmic rays (CRs)
and the clouds through the Fermi-LAT analysis and hadronic modeling."
- "We found a hard GeV source (SrcX2) that is spatially coincident
with both HESS J1858+020 and a molecular cloud complex at 3.6 kpc. In
addition, a soft GeV source (SrcX1) was found at the northern edge of
the SNR. The GeV spectrum of SrcX2 connects well with the TeV spectrum
of HESS J1858+020."
- "The entire gamma-ray spectrum ranges from several GeV up to tens of
TeV and it follows a power-law with an index of ~2.15. We discuss
several pieces of observational evidence to support the middle-aged
SNR argument. Using runaway CRs from the SNR, our hadronic model
explains the GeV-TeV emission at HESS J1858+020, with a diffusion
coefficient that is much lower than the Galactic value."
From
Abeysekara et al. (2015):
- "The source 1HWC J1857+023* is detected at 6.2sigma post trials and
is approx. 0.4deg away from both
HESS J1857+026 and HESS
J1858+020. ... The flux of
HESS J1857+026 is approximately an order of
magnitude higher than HESS J1858+020, and the differential flux
normalization from 1HWC J1857+023 is compatible with the combined flux
of
HESS J1857+026 and HESS J1858+020"
*1HWC J1857+023 is not listed under a separate entry in TeVCat. It is
listed as an associated source for
HESS J1857+026, HESS J1858+020
MAGIC J1857.2+0263 and
MAGIC J1857.6+0297.
From
Parades et al. (2013):
- "This work carries out a thorough multi-wavelength study of the
unidentified, very high energy source HESS J1858+020 and its
environs. ... The region surrounding HESS J1858+020 is rich in
molecular structures and non-thermal objects that may potentially be
linked to this unidentified very high energy source. In particular, a
supernova remnant interacting with nearby molecular clouds may be a
good candidate, but a star forming region, or a non-thermal radio
source of yet unclear nature, may also be behind the gamma-ray
source. Further observational studies are needed."
From
Paron et al. (2011):
- "We conclude that the most probable origin for the TeV gamma-ray emission
are the hadronic interactions between the molecular gas and the cosmic
rays accelerated by the shock front of the SNR G35.6-0.4"
From
Torres et al. (2011):
- "Here, we analyse more than 2 years of data obtained with the
Fermi-LAT for the region of interest, and consider whether it is
indeed possible that the closest LAT source, 1FGL J1857.1+0212c, is
related to HESS J1858+020. We conclude it is not, and we impose upper
limits on the GeV emission originating from HESS J1858+020."
Source Extent:
From
Aharonian et al. (2008):
- semi-major axis: 0.08 +/- 0.02 deg
- semi-minor axis: 0.02 +/- 0.04 deg
- angle: -4 +/- 17 deg
...measured counter-clk relative to RA axis
Seen by: H.E.S.S., HAWC
-
GeV Gamma-ray Emission and Molecular Clouds towards Supernova Remnant G35.6-0.4 and the TeV Source HESS J1858+020
Zhang, Xiao et al., arXiv e-prints parXiv:2204.12053 (2022) [LINK]
-
HESS J1858+020: A GeV-TeV source possibly powered by CRs from SNR G35.6-0.4
Cui, Y. et al., arXiv e-prints parXiv:2101.04851 (2021) [LINK]
-
The H.E.S.S. Galactic plane survey
H.E.S.S. Collaboration et al., A&A 612 pA1 (2018) [LINK]
-
Dense molecular gas at 12 mm towards Galactic TeV gamma-ray sources
de Wilt, P. et al., MNRAS 468 p2093-2113 (2017) [LINK]
-
Search for TeV Gamma-Ray Emission from Point-like Sources in the Inner Galactic Plane with a Partial Configuration of the HAWC Observatory
Abeysekara, A.U. et al., ArXiv e-prints p (2015) [LINK]
-
Deep GMRT radio observations and a multi-wavelength study of the region around HESS J1858+020
Paredes, J.M. et al., ArXiv e-prints p (2013) [LINK]
-
Study of the molecular clump associated with the high-energy source HESS J1858+020
Paron, S. et al., ArXiv e-prints p (2011) [LINK]
-
Cosmic rays in the surroundings of SNR G35.6-0.4
Torres, D.F. et al., MNRAS 417 p3072-3079 (2011) [LINK]
-
Identifying the counterpart of HESS J1858+020
Paron, S. and Giacani, E., A&A 509 pL4+ (2010) [LINK]
-
HESS very-high-energy gamma-ray sources without identified counterparts
Aharonian, F. et al., A&A 477 p353-363 (2008) [LINK]
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