Australian Journal of Physics Astrophysical Supplement

Clark, DH; Caswell, J. L.; Green, Anne

doi:10.1071/ph750651

Cited by 53 publications

(74 citation statements)

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“…The Ñux densities have been measured over a wide range of radio frequencies (e.g., by Kundu & Velusamy 1972 ;Dickel & DeNoyer 1975 ;Clark & Caswell 1976 ;Clark, Green, & Caswell 1975 ;Kassim 1992). The spectral index is about [0.33 (Kovalenko, PinzarÏ, & UdalÏtsov1994) to [0.4 (Giacani et al 1997, the latter reported with a Ñux density of about 400 Jy at 330 MHz.…”

Section: Distance Determinationmentioning

confidence: 99%

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

Cox

Shelton

Maciejewski

et al. 1999

ApJ

165

222

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We show that many observations of W44, a supernova remnant in the Galactic plane at a distance of about 2500 pc, are remarkably consistent with the simplest realistic model. The model remnant is evolving in a smooth ambient medium of fairly high density, about 6 cm~3 on average, with a substantial density gradient. At the observed time it has an age of about 20,000 yr, consistent with the age of the associated pulsar, and a radius of 11È13 pc. Over most of the outer surface, radiative cooling has become important in the postshock gas ; on the denser end there has been sufficient compression of the cooled gas to develop a very thin dense half-shell of about 450 supported against further compression by M _ , nonthermal pressure. The half-shell has an expansion velocity of about 150 km s~1 and is bounded on the outer surface by a radiative shock with that speed. The deep interior of the remnant has a substantial and fairly uniform pressure, as expected from even highly idealized adiabatic models ; our model, however, is never adiabatic. Thermal conduction, while the remnant is young and hot, reduces the need for expansion cooling and prevents formation of the intensely vacuous cavity characteristic of adiabatic evolution. It radically alters the interior structure from what one might expect from familiarity with the Sedov solution. At the time of observation, the temperature in the center is about 6 ] 106 K, the density about 1 cm~3. The temperature decreases gradually away from the center, while the density rises. Farther out, where cooling is becoming important, the pressure drops precipitously, and the temperature in the denser gas there is quite low. We provide several analytic tools for the assembly of models of this type. We review the early evolution and shell formation analyses and their generalizations to evolution in a density gradient. We also calculate the density and temperature that should be present in the hot interior of a remnant with thermal conduction. We supply the van der Laan mechanism in a particularly useful form for the calculation of radio continuum from radiative remnants. Finally, we estimate the optical emission that should be present from Ñuorescence of UV light, emitted by the forming shell and the radiative shock and absorbed in the cold shell and the ambient medium, and the associated 63 km [O I] emission. Both are in agreement with the intensity and spatial structures found in recent observations. Neither requires interaction with a dense molecular cloud for its generation. We calculate the gamma rays that should be emitted by cosmic-ray electrons and ions in the shell, interacting with the cold material, and Ðnd each capable of generating about 25% of the Ñux reported by EGRET for the vicinity.

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Section: Distance Determinationmentioning

confidence: 99%

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

Cox

Shelton

Maciejewski

et al. 1999

ApJ

165

222

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“…Below 11 GHz, the spectral index obtained by Morsi & Reich (1987a) is α = −0.26, which is consistent with our result. Adding new flux densities at 28, 40, 42, 44, 49, 61, 62, 64, 78, 95, 103, 105, 108, 111, 137, 139- Becker & Kundu (1975), (7) Dulk & Slee (1975), (8) Green (1974), (9) , (10) Kassim (1992), (11) Kothes & Reich (2001), (12) Morsi & Reich (1987b), (13) Milne et al (1969), (14) Reich et al (1984a), (15) Reifenstein et al (1970), (16) Slee (1977), (17) , (18) Shaver & Weiler (1976), (19) Tam et al (2002), (20) Angerhofer et al (1977), (21) Clark et al (1975a), (22) Dubner et al (1996), (23) Trushkin (1999), (24) Helfand et al (1989), (25) Reich et al (1986), (26) Clark et al (1975b), (27) Kesteven (1968), (28) Langston et al (2000), (29) Milne et al (1989), (30) Milne & Dickel (1975), …”

Section: Snr Spectramentioning

confidence: 99%

A Sino-Germanλ6 cm polarization survey of the Galactic plane

Sun

Reich

et al. 2011

A&A

119

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Aims. We study the spectral and polarization properties of supernova remnants (SNRs) using our λ6 cm survey data. Methods. We analyse data from observations taken as part of the Sino-German λ6 cm polarization survey of the Galactic plane. By using the integrated flux densities at λ6 cm together with measurements at other wavelengths from the literature, we derive the global spectra of 50 SNRs. In addition, from the observations at λ6 cm we obtain the polarization images of 24 SNRs. Results. We derive integrated flux densities at λ6 cm for 51 small SNRs with angular sizes smaller than 1 • . We are able to derive global radio spectral indices in all the cases except for Cas A. For the SNRs G15.1−1.6, G16.2−2.7, G16.4−0.5, G17.4−2.3, G17.8−2.6, G20.4+0.1, G36.6+2.6, G43.9+1.6, G53.6−2.2, G55.7+3.4, G59.8+1.2, G68.6−1.2, and G113.0+0.2, the spectra have been significantly improved. From our analysis, we argue that the object G16.8−1.1 is probably an H ii region instead of a SNR. Cas A shows a secular decrease in total intensity, and we measure a flux density of 688 ± 35 Jy at λ6 cm between 2004 and 2008. We detect polarized emission from 25 SNRs. For G16.2−2.7, G69.7+1.0, G84.2−0.8, and G85.9−0.6, the polarized emission is detected for the first time confirming that they are SNRs. Conclusions. High-frequency observations of SNRs are difficult but essential to determine their spectra and measure their polarization in particular towards the inner Galaxy, where Faraday effects are important.

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“…Previously, the big steps in the discovery of the Galactic SNRs relied on the radio surveys carried out by powerful telescopes, e.g., Shaver & Goss (1970) and Clark et al (1975) on the 408 MHz and 5 GHz surveys by the Parkes and Molonglo telescopes. Reich et al (1988) found many SNRs using the λ21 cm and λ11 cm surveys made by the Effelsberg 100-m telescope.…”

Section: Introductionmentioning

confidence: 99%

Discovery of a new supernova remnant G150.3+4.5

Gao

Han

2014

A&A

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Context. Large-scale radio continuum surveys have good potential for discovering new Galactic supernova remnants (SNRs). Surveys of the Galactic plane are often limited in the Galactic latitude of |b| ∼ 5 • . SNRs at high latitudes, such as the Cygnus Loop or CTA 1, cannot be detected by surveys in such limited latitudes. Aims. Using the available Urumqi λ6 cm Galactic plane survey data, together with the maps from the extended ongoing λ6 cm medium latitude survey, we wish to discover new SNRs in a large sky area. Methods. We searched for shell-like structures and calculated radio spectra using the Urumqi λ6 cm, Effelsberg λ11 cm, and λ21 cm survey data. Radio polarized emission and evidence in other wavelengths are examined for the characteristics of SNRs. Results. We discover an enclosed oval-shaped object G150.3+4.5 in the λ6 cm survey map. It is about 2.• 5 wide and 3 • high. Parts of the shell structures can be identified well in the λ11 cm, λ21 cm, and λ73.5 cm observations. The Effelsberg λ21 cm total intensity image resembles most of the structures of G150.3+4.5 seen at λ6 cm, but the loop is not closed in the northwest. High resolution images at λ21 cm and λ73.5 cm from the Canadian Galactic Plane Survey confirm the extended emission from the eastern and western shells of G150.3+4.5. We calculated the radio continuum spectral indices of the eastern and western shells, which are β ∼ −2.4 and β ∼ −2.7 between λ6 cm and λ21 cm, respectively. The shell-like structures and their non-thermal nature strongly suggest that G150.3+4.5 is a shell-type SNR. For other objects in the field of view, G151.4+3.0 and G151.2+2.6, we confirm that the shell-like structure G151.4+3.0 very likely has a SNR origin, while the circular-shaped G151.2+2.6 is an H ii region with a flat radio spectrum associated with optical filamentary structure, Hα, and infrared emission.

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Australian Journal of Physics Astrophysical Supplement

Cited by 53 publications

References 0 publications

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

A Sino-Germanλ6 cm polarization survey of the Galactic plane

Discovery of a new supernova remnant G150.3+4.5

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