A Survey of Hydroxyl toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission

Hewitt, John W.; Yusef‐Zadeh, F.; Wardle, Mark

doi:10.1086/588652

Cited by 65 publications

(77 citation statements)

References 65 publications

(142 reference statements)

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“…Usually such features indicate that a dense external cloud is disturbing an otherwise spherically symmetric shock expansion. These initial signatures need to be confirmed with more convincing, though more rare, features like broadenings, wings, or asymmetries in the the molecular line spectra (Frail and Mitchell 1998), high ratios between lines of different excitation state (Seta et al 1998), detection of near infrared H 2 or [Fe II] lines (e.g., Reach et al 2005), peculiar infrared colors (Reach et al 2006;Castelletti et al 2011), or the presence of OH (1720) MHz masers (e.g., Frail et al 1996;Green et al 1997;Claussen et al 1997;Hewitt et al 2008), the most powerful tool to diagnose SNR/MC interactions. The fulfillment of one or more of these different criteria can be used to propose the existence of "definitive", "probable" or "possible" physical interactions between an SNR and a neighboring cloud.…”

Section: Observational Signatures Of Snr/mc Interactionsmentioning

confidence: 99%

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

et al. 2014

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The giant molecular clouds (MCs) found in the Milky Way and similar galaxies play a crucial role in the evolution of these systems. The supernova explosions that mark the death of massive stars in these regions often lead to interactions between the supernova remnants (SNRs) and the clouds. These interactions have a profound effect on our understanding of SNRs. Shocks in SNRs should be capable of accelerating particles to cosmic ray (CR) energies with efficiencies high enough to power Galactic CRs. X-ray and γ-ray studies have established the presence of relativistic electrons and protons in some SNRs and provided strong evidence for diffusive shock acceleration as the primary acceleration mechanism, including strongly amplified magnetic fields, temperature and ionization effects on the shock-heated plasmas, and modifications to the dynamical evolution of some systems. Because protons dominate the overall energetics of the CRs, it is crucial to understand this hadronic component even though electrons are much more efficient radiators and it can be difficult to identify the hadronic component. However, near MCs the densities are sufficiently high to allow the γ-ray emission to be dominated by protons. Thus, these interaction sites provide some of our best opportunities to constrain the overall energetics of these particle accelerators. Here we summarize some key properties of interactions between SNRs and MCs, with an emphasis on recent X-ray and γ-ray studies that are providing important constraints on our understanding of cosmic rays in our Galaxy.

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Section: Observational Signatures Of Snr/mc Interactionsmentioning

confidence: 99%

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

et al. 2014

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“…In turn, an upper limit on the maser optical depth can be translated to an upper limit on OH column density through the OH excitation calculations. It turns out that the relatively poor sensitivity of the Parkes observations does not place strong constraints on the OH column; by contrast, the derived limits on OH column density implied by the lack of detected 6049 MHz masers in the Effelsberg and ATCA searches 444 M (Hewitt et al 2006;Hewitt, Yusef-Zadeh & Wardle 2008). These nine remnants are listed in Table 2 -all but G349.7+0.2 were searched for 6049 MHz emission with Effelsberg and/or ATCA, and so one might have expected several detections.…”

Section: Searches For 6049 Mhz Masersmentioning

confidence: 96%

“…While a beam filling factor was included in the modelling by Hewitt et al (2008) this does not account for different sub-structure in the background continuum and overlying OH absorption within the beam, and given that the inferred beam filling factors are typically 10 −2 this omission may be significant. To check whether the inferred OH columns are systematically overestimated we conducted 1667 MHz OH absorption observations of 3 remnants (3C 391, W44, and IC 443) using the VLA in D array, yielding a beam size of ∼ 55 ×90 .…”

Section: Searches For 6049 Mhz Masersmentioning

confidence: 99%

“…To check whether the inferred OH columns are systematically overestimated we conducted 1667 MHz OH absorption observations of 3 remnants (3C 391, W44, and IC 443) using the VLA in D array, yielding a beam size of ∼ 55 ×90 . We followed the approach of Hewitt et al (2008) in modelling the absorption at 1667 MHz in conjunction with 1720 MHz VLA data (the latter kindly provided by Jack Hewitt).…”

Section: Searches For 6049 Mhz Masersmentioning

confidence: 99%

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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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“…However, it is still not clear if the interaction with clouds is a unique mechanism to produce Mixed-morphology SNRs. A better indicator of supernova remnants and molecular clouds (SNR-MC) interactions is the presence of 1720 MHz OH masers, which are detected from ∼20 SNRs (Frail et al 1996;Yusef-Zadeh et al 1999;Hewitt et al 2008). These masers are thought to be collisionally excited and they suggest SNR-MC interactions, but maser emission is not well understood (Yusef-Zadeh et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Discovery of Broad Molecular Lines and of Shocked Molecular Hydrogen From the Supernova Remnant G357.7+0.3: Hhsmt, Apex, Spitzer, and Sofia Observations

Rho

Hewitt

Bieging

et al. 2016

ApJ

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We report a discovery of shocked gas from the supernova remnant (SNR) G357.7+0.3. Our millimeter and submillimeter observations reveal broad molecular lines of CO(2-1), CO(3-2), CO(4-3), 13 CO (2-1), and 13 CO (3-2), HCO + , and HCN using the Heinrich Hertz Submillimeter Telescope, the Arizona 12 m Telescope, APEX, and the MOPRA Telescope. The widths of the broad lines are 15-30 km s −1 , and the detection of such broad lines is unambiguous, dynamic evidence showing that the SNR G357.7+0.3 is interacting with molecular clouds. The broad lines appear in extended regions (>4 5 × 5′). We also present the detection of shocked H 2 emission in the mid-infrared but lacking ionic lines using Spitzer/IRS observations to map a few-arcminute area.The H 2 excitation diagram shows a best fit with a two-temperature local thermal equilibrium model with the temperatures of ∼200 and 660 K. We observed [C II] at 158 μm and high-J CO(11-10) with the German Receiver for Astronomy at Terahertz Frequencies (GREAT) on the Stratospheric Observatory for Infrared Astronomy. The GREAT spectrum of [C II], a 3σ detection, shows a broad line profile with a width of 15.7 km −1 that is similar to those of broad CO molecular lines. The line width of [C II] implies that ionic lines can come from a low-velocity C-shock. Comparison of H 2 emission with shock models shows that a combination of two C-shock models is favored over a combination of C-and J-shocks or a single shock. We estimate the CO density, column density, and temperature using a RADEX model. The best-fit model with n(H 2 )=1.7×10 4 cm −3 , N(CO)=5.6×10 16 cm −2 , and T=75 K can reproduce the observed millimeter CO brightnesses.

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A Survey of Hydroxyl toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission

Cited by 65 publications

References 65 publications

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

Supernova Remnants Interacting with Molecular Clouds: X-Ray and Gamma-Ray Signatures

OH Masers and Supernova Remnants

Discovery of Broad Molecular Lines and of Shocked Molecular Hydrogen From the Supernova Remnant G357.7+0.3: Hhsmt, Apex, Spitzer, and Sofia Observations

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