Relevant bibliographies by topics / HII regions;supernova remnants;radio lines

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Academic literature on the topic 'HII regions;supernova remnants;radio lines'

Author: Grafiati
Published: 4 June 2021
Last updated: 20 February 2023

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Journal articles on the topic "HII regions;supernova remnants;radio lines"

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Argo, M. K., A. Pedlar, T. W. B. Muxlow, and R. J. Beswick. "OH main line masers in the M 82 starburst." Proceedings of the International Astronomical Union 3, S242 (March 2007): 427–31. http://dx.doi.org/10.1017/s1743921307013543.

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AbstractA study of the distribution of OH gas in the central region of the nearby active starburst galaxy M82 has confirmed two previously known bright masers and revealed several new main line masers. Three of these are seen only at 1665 MHz, one is detected only at 1667 MHz, while the rest are detected in both lines. Observations covering both the 1665 and 1667 MHz lines, conducted with both the Very Large Array (VLA) and the Multi-Element Radio Linked Interferometer Network (MERLIN), have been used to accurately measure the positions and velocities of these features. This has allowed a comparison with catalogued continuum features in the starburst such as HII regions and supernova remnants, as well as known water and satellite line OH masers. Most of the main line masers appear to be associated with known HII regions although the two detected only at 1665 MHz are seen along the same line of sight as known supernova remnants.
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Supan, L., G. Castelletti, W. M. Peters, and N. E. Kassim. "G51.04+0.07 and its environment: Identification of a new Galactic supernova remnant at low radio frequencies." Astronomy & Astrophysics 616 (August 2018): A98. http://dx.doi.org/10.1051/0004-6361/201832995.

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We have identified a new supernova remnant (SNR), G51.04+0.07, using observations at 74 MHz from the Very Large Array Low-Frequency Sky Survey Redux (VLSSr). Earlier, higher frequency radio continuum, recombination line, and infrared data had correctly inferred the presence of nonthermal radio emission within a larger, complex environment including ionised nebulae and active star formation. However, our observations have allowed us to redefine at least one SNR as a relatively small source (7.′5 × 3′in size) located at the southern periphery of the originally defined SNR candidate G51.21+0.11. The integrated flux density of G51.04+0.07 at 74 MHz is 6.1 ± 0.8 Jy, while its radio continuum spectrum has a slope α = −0.52 ± 0.05 (S v ∝ vα), typical of a shell-type remnant. We also measured spatial variations in the spectral index between 74 and 1400 MHz across the source, ranging from a steeper spectrum (α = −0.50 ± 0.04) coincident with the brightest emission to a flatter component (α = −0.30 ± 0.07) in the surrounding fainter region. To probe the interstellar medium into which the redefined SNR is likely evolving, we have analysed the surrounding atomic and molecular gas using the 21 cm neutral hydrogen (HI) and 13CO(J = 1 − 0) emissions. We found that G51.04+0.07 is confined within an elongated HI cavity and that its radio emission is consistent with the remains of a stellar explosion that occurred ~6300 yr ago at a distance of 7.7 ± 2.3 kpc. Kinematic data suggest that the newly discovered SNR lies in front of HII regions in the complex, consistent with the lack of a turnover in the low frequency continuum spectrum. The CO observations revealed molecular material that traces the central and northern parts of G51.04+0.07. The interaction between the cloud and the radio source is not conclusive and motivates further study. The relatively low flux density (~1.5 Jy at 1400 MHz) of G51.04+0.07 is consistent with this and many similar SNRs lying hidden along complex lines of sight towards inner Galactic emission complexes. It would also not be surprising if the larger complex studied here hosted additional SNRs.
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Chu, You-Hua, and Robert C. Kennicutt. "Supernova Remnants in Giant HII Regions." International Astronomical Union Colloquium 101 (1988): 201–4. http://dx.doi.org/10.1017/s0252921100102374.

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Giant HII regions contain large numbers of massive stars, and hence are expected to contain large numbers of SNRs. Until recently, however, only a few SNRs have been identified in extragalactic giant HII regions. Moreover, most of these SNRs are located at the outskirts of HII regions, instead of the core where most of the stars are located. The low detection rate and the outlying locations of the SNRs may be due to: 1) observational difficulties - the background HII regions are much more luminous than the SNRs in both optical line emission and radio continuum; 2) intrinsic invisibility of SNRs - stellar wind and SNRs may have created a supershell (Mac Low and McCray 1987), and the core of a giant HII region is filled with hot tenuous coronal gas; or 3) a genuine deficiency of supernovae and SNRs in the HII regions (Sramek and Weedman 1986).
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Filipović, M. D., L. Staveley-Smith, W. Reid, and P. A. Jones. "Supernova Remnants in the Magellanic Clouds." Symposium - International Astronomical Union 218 (2004): 87–88. http://dx.doi.org/10.1017/s0074180900180672.

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A study of the nature and the spatial distribution of over 250 discrete radio sources (HII regions and SNRs) in the Magellanic Clouds (MCs) is underway. A multi-frequency comparison of these sources involves the latest radio, IR, optical and X-ray surveys with angular resolution of <1′. Special emphasis is given to the MC SNRs. Their morphology, birth rate and overall properties are investigated and compared with Galactic SNRs and SNRs from other nearby galaxies. Also, we are investigating the radio source distribution throughout both MCs.
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Filipovic, M. D., P. A. Jones, and G. L. Vhite. "The relation between radio flux density and ionizing ultra-violet flux for HII regions and supernova remnants in the Large Magellanic cloud." Serbian Astronomical Journal, no. 166 (2003): 31–37. http://dx.doi.org/10.2298/saj0366031f.

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We present a comparison between the Parkes radio surveys (Filipovic et al 1995) and Vacuum Ultra-Violet (VUV) surveys (Smith et al. 1987) of the Large Magellanic Clouds (LMC). We have found 72 sources in common in the LMC which are known HII regions (52) and supernova remnants (SNRs) (19). Some of these radio sources are associated with two or more UV stellar associations. A comparison of the radio flux densities and ionizing UV flux for HII regions shows a very good correlation, as expected from theory. Many of the Magellanic Clouds (MCs) SNRs are embedded in HII regions, so there is also a relation between radio and UV which we attribute to the surrounding HII regions.
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Odenwald, Sten F. "VLA Observations of Far-IR Sources Toward the Galactic Center." Symposium - International Astronomical Union 136 (1989): 205–11. http://dx.doi.org/10.1017/s0074180900186553.

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Preliminary results are presented from a 4.8-GHz VLA study of 5 far-IR sources within 1° of the Galactic center. Sgr-D and FIR-27 appear to be nearly featureless radio sources similar to young blister type HII regions, and FIR-21 has a filamentary structure similar to bright rimmed HII regions or Crab-like supernova remnants. Also presented are additional observations of Sgr-C.
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Filipović, Miroslav D., Paul A. Jones, Graeme L. White, and Raymond F. Haynes. "Comparison of Discrete Sources in Radio and Hα Surveys of the Magellanic Clouds and the Potential for the New Hα Survey." Publications of the Astronomical Society of Australia 15, no. 1 (1998): 128–31. http://dx.doi.org/10.1071/as98128.

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AbstractWe present a comparison between the latest Parkes radio surveys (Filipović et al. 1995, 1996, 1997) and Hα surveys of the Magellanic Clouds (Kennicutt & Hodge 1986). We have found 180 discrete sources in common for the Large Magellanic Cloud (LMC) and 40 in the field of the Small Magellanic Cloud (SMC). Most of these sources (95%) are HII regions and supernova remnants (SNRs). A comparison of the radio and Hα flux densities shows a very good correlation and we note that many of the Magellanic Clouds SNRs are embedded in HII regions.
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Turtle, A. J. "Supernova Remnants in the Magellanic Clouds Observed at the Molonglo Observatory." Symposium - International Astronomical Union 125 (1987): 130. http://dx.doi.org/10.1017/s0074180900160656.

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Radio surveys of the Magellanic Clouds at 843 MHz have been made with the Molonglo Observatory Synthesis Telescope. An initial catalogue (Mills et al. 1984) presented details of 38 supernova remnants detected by a combination of X-ray, optical and radio observations. The subsequent completion of the radio survey has revealed at least a further 17 remnants, mainly of large diameter and undetected by the Einstein X-ray Observatory. Though a few remnants have their radio emission concentrated towards their centre there is no evidence in the Magellanic Clouds for a Crab-like plerion (without an associated shell). The two well-established plerions 0540-693 (with optical and X-ray pulsar) and 0538-691 (N157B) appear to be connected with partial shells of strong radio emission which are relatively weak in optical emission lines (0538-691 is superposed on an HII region). Four sources which have a central concentration show larger optical and X-ray shells. The optical spectra of three of these (0505-679, 0509-675 and 0519-690) are dominated by the emission lines of hydrogen and Tuohy et al. (1982) argue that they are remnants of Type I supernovae. The fourth source (0453-685) which has detectable [OIII] emission may be an older but similar type of remnant. A further remnant 0509-687 (N103B) is compact but its radio diameter of 6 pc agrees with the published X-ray result.
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Duncan, A. R., and R. F. Haynes. "Bright Prospects: Comparing the Hα Survey with Large-scale Radio Continuum Emission." Publications of the Astronomical Society of Australia 15, no. 1 (1998): 50–55. http://dx.doi.org/10.1071/as98050.

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AbstractProspects for comparisons between the AAO/UKST Hα survey and large-scale radio continuum emission are considered, with particular reference to the recently completed Parkes 2·4 GHz survey of the southern Galactic Plane. Both these surveys have a high sensitivity to thermal emission, and comparisons between the Parkes work and previous Hα surveys show many objects in common. Possibilities for new detections include: a number of new supernova remnants; the faint extensions and envelopes surrounding ‘classical’ HII complexes, and other faint regions of thermal emission; several active HII complexes, including an outflow of ionised gas from IC 4628 and a number of bi-polar ‘plumes’ of low-density, thermal material apparently associated with HII complexes on the Carina spiral arm.
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Pedlar, Alan, Tom Muxlow, and Jon Riley. "Radio Observations of Supernova Remnants in the M82 Starburst." International Astronomical Union Colloquium 192 (2005): 219–25. http://dx.doi.org/10.1017/s0252921100009222.

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SummaryWe report on recent MERLIN, VLA and VLBI observations of the compact radio sources in the nearby starburst M82, with angular resolutions ranging from arcseconds to milliarcseconds. The spectral properties of the compact sources have been investigated by 15 GHz VLA-Pie Town observations which show that 16 of the less luminous compact sources are, in fact, HII regions. However the steep non-thermal spectrum, parsec size and small variability of the remaining sources is consistent with their being supernova remnants. Several show clear shell structures at MERLIN resolution (~50 mas) and 5 have been resolved further using VLBI. Measurements of the most compact source (41.95+575) shows an expansion velocity of ~ 2000 km s-1, and one of the best defined SNR shells (43.31+592) shows an expansion velocity of ~ 104 km s-1. Recent VLBI and MERLIN measurements confirm this expansion velocity and show little evidence for deceleration. We comment on the discrepancy between this measured expansion velocity and the low expansion velocities predicted theoretically for remnants in M82.
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Dissertations / Theses on the topic "HII regions;supernova remnants;radio lines"

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Misanovic, Zdenka. "A search for young galactic supernova remnants." University of Sydney. Physics, 2001. http://hdl.handle.net/2123/795.

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A sample of 9 small-diameter radio sources has been selected from the Molonglo Galactic Plane Survey (MGPS) and observed with the Australia Telescope Compact Array (ATCA) in the radio recombination line (RRL) at 5 GHz, in a search for young Galactic SNRs. Since the RRL emission is an unambiguous indicator of a thermal source, this method has been used to eliminate HII regions from the selected sample. In addition, the IRAS and MSX infrared data and spectral index measurements have been combined with the RRL studies to distinguish thermal and non-thermal sources in the selected sample. One source (G282.8-1.2) is identified here as a possible new young Galactic supernova remnant, based on its relatively weak infrared emission, steep radio spectrum and possible x-ray emission. However, the ATCA data are inconclusive and further studies are needed to confirm this result. Radio recombination line emission (H107 alpha) has been detected in 3 of the selected sources, eliminating them from the sample of SNR candidates. In addition, the parameters of the RRL emission from the identified HII regions have been used to estimate their properties. The RRL data are inconclusive for the remaining low brightness, extended sources in the sample. However, some of these sources are likely to be thermal HII regions according to the infrared and spectral index data. The selected method for distinguishing thermal and non-thermal Galactic radio sources seems promising. The selected ATCA configuration was appropriate for imaging relatively bright, compact sources, but a slightly modified observing technique is needed to successfully image low surface brightness, extended sources.
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Book chapters on the topic "HII regions;supernova remnants;radio lines"

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Pannuti, Thomas G. "Galactic Radio Astronomy: Galactic Structure, HII Regions, Supernova Remnants, Neutron Stars and Pulsars." In Undergraduate Lecture Notes in Physics, 191–268. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-16982-8_6.

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