On the Distance and Molecular Environment of Westerlund 2 and HESS J1023-575

Dame, T. M.

doi:10.1086/521363

Cited by 40 publications

(71 citation statements)

References 26 publications

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“…The studies of the molecular hydrogen by Dame (2007), Furukawa et al (2009) and Ohama et al (2010) show a complex environment around Westerlund 2. Two molecular clouds in the velocity ranges of [-11 : 9] km/s and [11: 21] km/s physically coincide with Westerlund 2 and and the large H ii region RCW 49.…”

Section: Gas Around Westerlundmentioning

confidence: 99%

Diffuse γ-ray emission in the vicinity of young star cluster Westerlund 2

Yang

Wilhelmi

Aharonian

2018

A&A

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We report the results of our analysis of the publicly available data obtained by the Large Area Telescope (LAT) on board of the Fermi satellite towards the direction of the young massive star cluster Westerlund 2. We found significant extended γ-ray emission in the vicinity of Westerlund 2 with a hard power-law energy spectrum extending from 1 GeV to 250 GeV with a photon index of 2.0 ± 0.1. We argue that amongst several alternatives, the luminous stars in Westerlund 2 are likely sites of acceleration of particles responsible for the diffuse γ-ray emission of the surrounding interstellar medium. In particular, the young star cluster Westerlund 2 can provide sufficient non-thermal energy to account for the gamma-ray emission. In this scenario, since the γ-ray production region is significantly larger than the area occupied by the star cluster, we conclude that the γ-ray production is caused by hadronic interactions of the accelerated protons and nuclei with the ambient gas. In that case, the total energy budget in relativistic particles is estimated of the order of 10 50 erg.

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Section: Gas Around Westerlundmentioning

confidence: 99%

Diffuse γ-ray emission in the vicinity of young star cluster Westerlund 2

Yang

Wilhelmi

Aharonian

2018

A&A

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“…The total mechanical luminosity (W total ) available from stellar winds in Westerlund 2 is estimated to be 3.6 × 10 51 erg (Rauw et al 2007). Observations of the molecular cloud content in the region by Dame (2007) shows a complex and rich environment and triggered high resolution (1.5 ) observations with the Nanten 2 4-m sub-mm telescope. The latter observations resolved massive molecular clouds at ∼16 km s −1 and ∼4 km s −1 (6.5 and 5.2 kpc), that were previously reported by Dame (2007), as well as a second component at ∼-4 km s −1 which appears to be coincident with a region of ongoing star formation.…”

Section: Emission Scenarios Related To Massive Stars and Their Windsmentioning

confidence: 99%

“…Observations of the molecular cloud content in the region by Dame (2007) shows a complex and rich environment and triggered high resolution (1.5 ) observations with the Nanten 2 4-m sub-mm telescope. The latter observations resolved massive molecular clouds at ∼16 km s −1 and ∼4 km s −1 (6.5 and 5.2 kpc), that were previously reported by Dame (2007), as well as a second component at ∼-4 km s −1 which appears to be coincident with a region of ongoing star formation. To illustrate the extent of the star formation region, a three-color Spitzer/IRAC GLIMPSE image is shown in Fig.…”

Section: Emission Scenarios Related To Massive Stars and Their Windsmentioning

confidence: 99%

“…The molecular cloud content in this region observed by the CfA 1.2 m Millimeter-Wave Telescope and the 4-m Nanten 2 sub-mm telescope shows a complex and rich environment. Dame (2007) observed Westerlund 2 with the CfA 1.2 m telescope using 12 CO(J = 1-0) survey data and found a possible association with a giant molecular cloud (GMC) on the far side of the Carina spiral arm, at a distance of 5.0 kpc. Observations at a higher resolution (90 ) on the J = 2-1 transition of 12 CO performed by the Nanten 2 4-m sub-millimeter telescope Ohama et al 2010) confirm the Dame (2007) results but also suggest another possible association.…”

Section: Introductionmentioning

confidence: 99%

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Revisiting the Westerlund 2 field with the HESS telescope array

Abramowski¹,

Acero²,

Aharonian³

et al. 2010

A&A

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Aims. Previous observations with the HESS telescope array revealed the existence of extended very-high-energy (VHE; E > 100 GeV) γ-ray emission, HESS J1023-575, coincident with the young stellar cluster Westerlund 2. At the time of discovery, the origin of the observed emission was not unambiguously identified, and follow-up observations have been performed to further investigate the nature of this γ-ray source. Methods. The Carina region towards the open cluster Westerlund 2 has been re-observed, increasing the total exposure to 45.9 h. The combined dataset includes 33 h of new data and now permits a search for energy-dependent morphology and detailed spectroscopy. Results. A new, hard spectrum VHE γ-ray source, HESS J1026-582, was discovered with a statistical significance of 7σ. It is positionally coincident with the Fermi LAT pulsar PSR J1028-5819. The positional coincidence and radio/γ-ray characteristics of the LAT pulsar favors a scenario where the TeV emission originates from a pulsar wind nebula. The nature of HESS J1023-575 is discussed in light of the deep HESS observations and recent multi-wavelength discoveries, including the Fermi LAT pulsar PSR J1022-5746 and giant molecular clouds in the region. Despite the improved VHE dataset, a clear identification of the object responsible for the VHE emission from HESS J1023-575 is not yet possible, and contribution from the nearby high-energy pulsar and/or the open cluster remains a possibility.

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“…Investigating the possible relationship between molecular gas and high-energy emission can be quite fruitful, as a recent study of the Westerlund 2 TeV source illustrates (Dame 2007). The situation for the Cygnus source is much more complicated owing to a great deal of confusion along this line of sight (see, e.g., Fig.…”

Section: Introductionmentioning

confidence: 99%

The Molecular Environment of the Gamma-Ray Source TeV J2032+4130

Butt¹,

Schneider²,

Dame³

et al. 2008

ApJ

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The mysterious very high energy gamma-ray source, TeV J2032ϩ4130, is coincident with the powerful Cygnus OB2 stellar association, although a physical association between the two remains uncertain. It is possible that the detected very high energy photons are produced via an overdensity of locally accelerated cosmic rays impinging on molecular clouds in the source region. In order to test this hypothesis, we used the Kitt Peak 12 m, the Heinrich Hertz Submillimeter Telescope (HH-SMT), and the Five College Radio Astronomy Observatory (FCRAO) to obtain observations in the and lines of both 12 CO and 13 CO. We report here J p 1 r 0 J p 2 r 1 on the detection of significant molecular material toward the TeV source region which could be acting as the target of locally accelerated CRs. We also find evidence of compact molecular clumps, showing large line widths in the CO spectra, possibly indicative of energetic processes in this region of Cygnus OB2.

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On the Distance and Molecular Environment of Westerlund 2 and HESS J1023-575

Cited by 40 publications

References 26 publications

Diffuse γ-ray emission in the vicinity of young star cluster Westerlund 2

Diffuse γ-ray emission in the vicinity of young star cluster Westerlund 2

Revisiting the Westerlund 2 field with the HESS telescope array

The Molecular Environment of the Gamma-Ray Source TeV J2032+4130

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