Visibility of old supernova remnants in H i 21-cm emission line

Koo, Bon‐Chul; Kang, Ji-hyun

doi:10.1111/j.1365-2966.2004.07579.x

Cited by 21 publications

(20 citation statements)

References 53 publications

(102 reference statements)

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“…Finally, the fact that 63 (62%) out of those 101 SNRs have Σ 1 GHz < 10 −20 W m −2 sr −1 Hz −1 can be considered as a proof that the large fraction of SNRs are evolving in the low-density phase of the ISM. The same conclusion about the environments of the galactic SNRs was earlier made by Marsden et al (2001) from the association of AXP and SGR with SNRs and in Koo and Kang (2004) from the considerable deficit of HI-emitting, old SNRs. This result is also in accordance with the theory of McKee and Ostriker (1977), which predicts the widespread existence of hot and low-density gas in the Galaxy.…”

Section: The σ − D Relationshipsupporting

confidence: 73%

Radio emission from shell-type supernova remnants

Asvarov¹

2006

A&A

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The evolution of the radio emission of shell-type Supernova remnants (SNRs) is modeled within the framework of the simple and commonly used assumptions that the mechanism of diffusive shock acceleration (DSA) is responsible for generating radio emitting electrons and that the magnetic field is the typical interstellar field compressed at the shock. It is considered that electrons are injected into the mechanism in test-particle regime directly from the high energy tail of the downstream Maxwellian distribution function. The model can be applied to most of the observed SNRs because the majority of detected SNRs are shell-types and have a more or less spherical shape and are sources of nonthermal radio emission. It is shown that the model successfully explains the many averaged observational properties of evolved shell-type SNRs. In particular, the radio surface brightness (Σ) evolves with diameter as ∼D −(0.3÷0.5) , while the bounding shock is strong (Mach number is M ≥ 10), followed by steep decrease (steeper than ∼D −4.5 ) for M < 10. Such evolution of the surface brightness with diameter and its strong dependence on the environmental parameters strongly reduce the usefulness of Σ − D relations as a tool for determining the distances to SNRs. The model predicts no radio emission from SNRs in the late radiative stage of evolution and the existence of radio-quiet but relatively active SNRs is possible. Our model easily explains very large-diameter radio sources such as the Galactic Loops and the candidates for Hypernova radio remnants. The model predicts that most of the observed SNRs with Σ 1 GHz < ∼ 10 −20 W m −2 sr −1 Hz −1 are located in a tenuous phase of the ISM. The model also predicts the existence of a population of 150−250 pc SNRs with Σ 1 GHz < ∼ 10 −22 W m −2 sr −1 Hz −1 if the kinetic energy of the explosion is ∼10 51 erg. From the comparison of the model results with the statistics of evolved shell-type SNRs, we were able to estimate the fraction of electrons accelerated from the thermal pool in the range (3 ÷ 11) × 10 −4 . If acceleration takes place directly from the high energy tail of the downstream Maxwellian distribution function, then the corresponding injection momentum is estimated as p inj ∼ (2.7−3) · p th .

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Section: The σ − D Relationshipsupporting

confidence: 73%

Radio emission from shell-type supernova remnants

Asvarov¹

2006

A&A

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“…In large-scale ( , v) diagrams of H i 21 cm line emission in the Galactic plane, there are many small, faint, high-velocity (HV) "wing-like" features extending to velocities well beyond the maximum or minimum permitted by Galactic rotation (Koo & Kang 2004). These "Forbidden Velocity Wings (FVWs)" are likely due to energetic phenomena in the Galaxy, as they are confined to small areas ( 2 • ) and project smoothly beyond the general Galactic emission to high velocities.…”

Section: Introductionmentioning

confidence: 99%

“…These "Forbidden Velocity Wings (FVWs)" are likely due to energetic phenomena in the Galaxy, as they are confined to small areas ( 2 • ) and project smoothly beyond the general Galactic emission to high velocities. Koo & Kang (2004) suggested that some of these FVWs may represent the expanding shells of "missing" supernova remnants (SNRs), which are not included in existing SNR catalogs. The basic idea is that old SNRs are faint in the radio continuum, making it difficult to identify them because of both the confusion due to the Galactic background emission and observational limitations (e.g., Brogan et al 2006).…”

Section: Introductionmentioning

confidence: 99%

“…The basic idea is that old SNRs are faint in the radio continuum, making it difficult to identify them because of both the confusion due to the Galactic background emission and observational limitations (e.g., Brogan et al 2006). Koo & Kang (2004) considered the fact that an old SNR should possess a fast-expanding H i shell that will still be present as a coherent entity after the remnant becomes too faint to be visible in the radio continuum. If its expansion velocity is greater than the minimum or maximum velocities permitted by Galactic rotation, then an old SNR shell, or part of it (maybe the caps), could be detected as HV H i gas, e.g., FVWs.…”

Section: Introductionmentioning

confidence: 99%

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An Old Supernova Remnant Within an H Ii Complex at ℓ ≈ 173°: FVW 172.8+1.5

Kang

Koo

Salter

2012

The Astronomical Journal

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We present the results of H i 21 cm line observations to explore the nature of the high-velocity (HV) H i gas at ∼ 173• . In low-resolution H i surveys this HV gas appears as faint, wing-like, H i emission that extends to velocities beyond those allowed by Galactic rotation. We designate this feature as Forbidden Velocity Wing (FVW) 172.8+1.5. Our high-resolution (3. 4) Arecibo H i observations show that FVW 172.8+1.5 is composed of knots, filaments, and ring-like structures distributed over an area of a few degrees in extent. These HV H i emission features are confined within the limits of the H ii complex G173+1.5, which is composed of five Sharpless H ii regions distributed along a radio continuum loop of size 4.• 4 × 3.• 4, or ∼138 pc × 107 pc, at a distance of 1.8 kpc. G173+1.5 is one of the largest star-forming regions in the outer Galaxy. We demonstrate that the HV H i gas is well correlated with the radio continuum loop and that the two seem to trace an expanding shell. The expansion velocity of the shell is large (55 km s −1 ), suggesting that it represents a supernova remnant (SNR). We derive physical parameters for the shell and show these to be consistent with the object being an SNR. We also detect hot X-ray-emitting gas inside the H ii complex by analyzing the ROSAT all-sky X-ray background survey data. This also supports the SNR interpretation. We conclude that the HV H i gas and the X-rays are most likely the products of a supernova explosion(s) within the H ii complex, possibly in a cluster that triggered the formation of these H ii regions.

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“…Dubner et al 1998;Reynoso et al 1999;Giacani et al 2000;Velázquez et al 2002;Koo & Kang 2004;Paron et al 2006;Lee et al 2008;Park et al 2013). An interesting approach using atomic gas studies was recently used in the historic remnant of SN 1006 by Miceli et al (2014), where an important connection between shock-cloud interaction and particle acceleration was demonstrated based on the comparison of X-ray with HI data.…”

Section: Consequences Of the Interactionmentioning

confidence: 99%

Radio Emission from Supernova Remnants

Dubner

2016

Handbook of Supernovae

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The explosion of a supernova releases almost instantaneously about 10 51 ergs of mechanic energy, changing irreversibly the physical and chemical properties of large regions in the galaxies. The stellar ejecta, the nebula resulting from the powerful shock waves, and sometimes a compact stellar remnant, constitute a supernova remnant (SNR). They can radiate their energy across the whole electromagnetic spectrum, but the great majority are radio sources. Almost 70 years after the first detection of radio emission coming from a SNR, great progress has been achieved in the comprehension of their physical characteristics and evolution. We review the present knowledge of different aspects of radio remnants, focusing on sources of the Milky Way and the Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief overview of theoretical background, analyze morphology and polarization properties, and review and critical discuss different methods applied to determine the radio spectrum and distances. The consequences of the interaction between the SNR shocks and the surrounding medium are examined, including the question of whether SNRs can trigger the formation of new stars. Cases of multispectral comparison are presented. A section is devoted to reviewing recent results of radio SNRs in the Magellanic Clouds, with particular emphasis on the radio properties of SN 1987A, an ideal laboratory to investigate dynamical evolution of an SNR in near real time. The review concludes with a summary of issues on radio SNRs that deserve fur-G. Dubner and E. Giacani are members of the "Carrera del Investigador Científico" of CONICET, Argentina

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Visibility of old supernova remnants in H i 21-cm emission line

Cited by 21 publications

References 53 publications

Radio emission from shell-type supernova remnants

Radio emission from shell-type supernova remnants

An Old Supernova Remnant Within an H Ii Complex at ℓ ≈ 173°: FVW 172.8+1.5

Radio Emission from Supernova Remnants

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