Supernova Remnant OH Masers: Signposts of Cosmic Collision

Wardle, Mark; Yusef‐Zadeh, F.

doi:10.1126/science.1068168

Cited by 86 publications

(85 citation statements)

References 56 publications

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“…Fig. 1), underpinned by a theoretical production mechanism hinging on molecular shock waves, provides a firm basis for assuming that the presence of these masers signals the existence of a shock wave driven by a supernova remnant into an adjacent cloud (Wardle & Yusef-Zadeh 2002). This has been confirmed by follow-up studies of individual remnants.…”

Section: Introductionsupporting

confidence: 52%

OH Masers and Supernova Remnants

Wardle

McDonnell

2012

Proc. IAU

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Abstract. OH(1720 MHz) masers are created by the interaction of supernova remnants with molecular clouds. These masers are pumped by collisions in warm, shocked molecular gas with OH column densities in the range 10 16 -10 17 cm −2 . Excitation calculations suggest that inversion of the 6049 MHz OH line may occur at the higher column densities that have been inferred from main-line absorption studies of supernova remnants with the Green Bank Telescope. OH(6049 MHz) masers have therefore been proposed as a complementary indicator of remnantcloud interaction.This motivated searches for 6049 MHz maser emission from supernova remnants using the Parkes 63 m and Effelsberg 100 m telescopes, and the Australia Telescope Compact Array. A total of forty-one remnants have been examined by one or more of these surveys, but without success. To check the accuracy of the OH column densities inferred from the single-dish observations we modelled OH absorption at 1667 MHz observed with the Very Large Array towards three supernova remnants, IC 443, W44 and 3C 391. The results are mixed -the OH column is revised upwards in IC443, downwards in 3C391, and is somewhat reduced in W44. We conclude that OH columns exceeding 10 17 cm −2 are indeed present in some supernova remnants and so the lack of any detections is not explained by low OH column density. We discuss the possibility that non-local line overlap is responsible for suppressing the inversion of the 6049 MHz line.

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Section: Introductionsupporting

confidence: 52%

OH Masers and Supernova Remnants

Wardle

McDonnell

2012

Proc. IAU

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“…Paradoxically, non-dissociative shocks can produce hotter molecular material than faster dissociative shocks, where molecules are quickly destroyed behind the shock front and are reformed only after the gas has cooled to ∼ 500 K. In some maser sources, gas temperatures of at least ∼ 900 K are implied by the observed water maser line ratios, indicating the presence of non-dissociative shocks (Melnick et al 1993). Where supernova-driven shock waves encounter molecular clouds, widespread 1720 MHz OH maser emission is observed; here, the enhanced column densities of OH needed to explain the observed maser emission are believed to result from the effects of X-rays and/or cosmic rays in dissociating H 2 O to form OH (Wardle & Yusef-Zadeh 2002). …”

Section: Figurementioning

confidence: 95%

Interstellar Hydrides

Gérin

Neufeld

Goicoechea

2016

Annu. Rev. Astron. Astrophys.

128

171

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Interstellar hydrides -that is, molecules containing a single heavy element atom with one or more hydrogen atoms -were among the first molecules detected outside the solar system. They lie at the root of interstellar chemistry, being among the first species to form in initially-atomic gas, along with molecular hydrogen and its associated ions. Because the chemical pathways leading to the formation of interstellar hydrides are relatively simple, the analysis of the observed abundances is relatively straightforward and provides key information about the environments where hydrides are found. Recent years have seen rapid progress in our understanding of interstellar hydrides, thanks largely to far-IR and submillimeter observations performed with the Herschel Space Observatory. In this review, we will discuss observations of interstellar hydrides, along with the advanced modeling approaches that have been used to interpret them, and the unique information that has thereby been obtained.

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“…In radio continuum emission, the western area is faint and has no distinct shell-like feature in visible region, whereas a bright semi-circular shell is evident in the east. In CGPS 1420 MHz radio emission, there was no polarized emission (Willis 1973;Landecker et al 1985;Kothes et al 2006). An HI observation suggested that a HI stellar wind bubble at 4.5 kpc is surrounding the remnant and that the progenitor could be an O4 Fig.…”

Section: G769+10mentioning

confidence: 98%

SRAO CO observation of 11 supernova remnants in l=70∘ to 190∘

Jeong

Byun

Koo

et al. 2012

Astrophys Space Sci

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We present the results of 12 CO J = 1−0 line observations of eleven Galactic supernova remnants (SNRs) obtained using the Seoul Radio Astronomy Observatory (SRAO) 6-m radio telescope. The observation was made as a part of the SRAO CO survey of SNRs between l = 70 • and 190 • , which is intended to identify SNRs interacting with molecular clouds. The mapping areas for the individual SNRs are determined to cover their full extent in the radio continuum. We used halfbeam grid spacing (60 ′′ ) for 9 SNRs and full-beam grid spacing (120 ′′ ) for the rest. We detected CO emission towards most of the remnants. In six SNRs, molecular clouds showed a good spatial relation with their radio morphology, although no direct evidence for the interaction was detected. Two SNRs are particularly interesting: G85.4+0.7, where there is a filamentary molecular cloud along the radio shell, and 3C434.1, where a large molecular cloud appears to block the western half of the remnant. We briefly summarize the results obtained for individual SNRs.

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Supernova Remnant OH Masers: Signposts of Cosmic Collision

Cited by 86 publications

References 56 publications

OH Masers and Supernova Remnants

OH Masers and Supernova Remnants

Interstellar Hydrides

SRAO CO observation of 11 supernova remnants in l=70∘ to 190∘

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