scholarly journals The relation between radio flux density and ionizing ultra-violet flux for HII regions and supernova remnants in the Large Magellanic cloud

2003 ◽  
pp. 31-37 ◽  
Author(s):  
M.D. Filipovic ◽  
P.A. Jones ◽  
G.L. Vhite
Keyword(s):  
Flux Density ◽  
Supernova Remnants ◽  
Ultra Violet ◽  
Hii Regions ◽  
Large Magellanic Cloud ◽  
Magellanic Clouds ◽  
Radio Sources ◽  
Radio Flux ◽  
Stellar Associations ◽  
Vacuum Ultra Violet

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.

scholarly journals Comparison of Discrete Sources in Radio and Hα Surveys of the Magellanic Clouds and the Potential for the New Hα Survey

1998 ◽  
Vol 15 (1) ◽  
pp. 128-131 ◽  
Author(s):  
Miroslav D. Filipović ◽  
Paul A. Jones ◽  
Graeme L. White ◽  
Raymond F. Haynes
Keyword(s):  
Supernova Remnants ◽  
Hii Regions ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Small Magellanic Cloud

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.

scholarly journals A Radio Continuum Survey of the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 283-291 ◽  
Author(s):  
B. Y. Mills ◽  
A. J. Turtle
Keyword(s):  
Supernova Remnants ◽  
Large Magellanic Cloud ◽  
Magellanic Clouds ◽  
Radio Continuum ◽  
Radio Sources ◽  
Synchrotron Emission ◽  
Low Frequencies ◽  
External Galaxies ◽  
Continuum Radio ◽  
The Individual

Continuum radio emission from the Large Magellanic Cloud was first detected just 30 years ago (Mills & Little, 1953). Subsequently, surveys of the Clouds were made after each new advance in southern hemisphere instrumentation and the principal surveys are listed and briefly described in Table I. They cover a range of frequencies from 19.7 MHz to 8.4 GHz. The early surveys at low frequencies were chiefly concerned with the overall synchrotron emission from the Clouds but, as resolution improved, emphasis has shifted to the individual sources, both emission nebulae and supernova remnants, which can be recognized as Cloud members. Of recent years the unique position of the Clouds for studying radio sources in external galaxies has been undermined by the development of powerful synthesis telescopes in the northern hemisphere; these have provided equivalent sensitivity and better spatial resolution on M31, and several other northern galaxies can also be studied effectively. However, with the commissioning of the Molonglo Observatory Synthesis Telescope (MOST) in 1981 the Clouds have been restored to their rightful place befitting the closest galaxies.

scholarly journals ISO Observations of Compact HII Regions in the Large Magellanic Cloud

1999 ◽  
Vol 190 ◽  
pp. 377-378
Author(s):  
A. Moneti ◽  
R. J. Laureijs ◽  
J.M. van der Hulst ◽  
F. Israel ◽  
P.P. van der Werf
Keyword(s):  
Star Formation ◽  
Hii Regions ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
First Results ◽  
Reflection Nebulae ◽  
Compact Hii Regions

With the detection of strong PAH features and H2 emission in selected knots of the N159, N11A, and 30 Dor regions in the LMC, we present the first results of a study that is part of a coordinated Guaranteed Time ISO programme to investigate star formation in the Magellanic Clouds. The PAH features have different ratios than the ones in Galactic reflection nebulae.

scholarly journals The Radio Properties of SNRs in the Magellanic Clouds

1983 ◽  
Vol 101 ◽  
pp. 551-558 ◽  
Author(s):  
B. Y. Mills
Keyword(s):  
Supernova Remnants ◽  
Average Distance ◽  
Hii Regions ◽  
Magellanic Clouds ◽  
Selection Effects ◽  
Absolute Distance ◽  
Major Difficulty ◽  
Order Of Magnitude ◽  
Thermal Sources ◽  
Better Than

An understanding of the radio properties and evolution of Galactic supernova remnants has always been hampered by the difficulty of measuring distances. A conventional wisdom has developed around a set of ‘good’ calibrators but most workers involved have drawn attention to the uncertainties and the possibility of selection effects distorting results. This major difficulty is completely overcome by studying SNRs in the Magellanic Clouds. Although there is uncertainty in the absolute distance scale, relative distances can be determined to better than 10% and differences of this magnitude are not significant when intercomparing SNRs. There is, however, another set of problems associated with sensitivity and resolution. The Clouds are an order of magnitude more distant than the average distance of Galactic SNRs, thus many of the SNRs are close to or below the sensitivity limits of most of the southern radiotelescopes and, until recently, the resolution available has often been inadequate to separate non-thermal sources from thermal HII regions, so that both flux densities and spectra have been subject to error. Also there are ∼ 1000 extragalactic background sources which can mimic the flux density and spectra of SNRs in the Clouds, particularly when close to or behind HII regions; as a result numerous incorrect or doubtful SNR identifications have been suggested.

scholarly journals Classification of Supernova Remnants and HII Regions from their Recombination Line Emission

1972 ◽  
Vol 25 (5) ◽  
pp. 539 ◽  
Author(s):  
JR Dickel ◽  
DK Milne
Keyword(s):  
Electron Temperature ◽  
Supernova Remnants ◽  
Line Emission ◽  
Hii Regions ◽  
Radio Sources ◽  
Recombination Line ◽  
Line Frequency ◽  
Upper Limits ◽  
Galactic Radio

H109a, recombination line observations are used in an attempt to classify 46 galactic radio sources as either supernova remnants or HII regions. Long integrations at the H109a line frequency on two well-known supernova remnants (IC 443 and 3C 391) provide improved upper limits on the line emission from these objects. From these results the electron temperature in IC 443 is estimated to be in excess of 1�6 � 104 K.

scholarly journals Australian Journal of Physics Astrophysical Supplement

1976 ◽  
Vol 29 (5) ◽  
pp. 471
Author(s):  
JN Clarke ◽  
AG Little ◽  
BY Mills
Keyword(s):  
Flux Density ◽  
High Frequency ◽  
Magellanic Clouds ◽  
Australian Journal ◽  
The Other ◽  
Optical Data ◽  
Radio Sources ◽  
Angular Extent

The fourth catalogue of radio sources observed at 408 MHz with the Molonglo radiotelescope is presented. A total of 1349 sources is listed to a limiting flux density of 0�2 Jy, the catalogue being largely complete above 0� 25 Jy. The area of sky surveyed includes the Magellanic Clouds as well as a comparison region of similar angular extent. Detailed notes are provided on some of the Cloud sources, and maps are given for complex sources in the region of the Clouds. Those sources for which high-frequency or optical data are available are classified into two lists, one of Cloud members and the other of 'unidentified nonthermal sources', presumably not Cloud members.

scholarly journals 8·8 GHz Radio Observations of 12 Suggested Supernova Remnants

1973 ◽  
Vol 26 (3) ◽  
pp. 379 ◽  
Author(s):  
JR Dickel ◽  
DK Milne ◽  
AR Kerr ◽  
JG Ables
Keyword(s):  
Flux Density ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Galactic Plane ◽  
Small Diameter ◽  
Radio Sources ◽  
Radio Observations ◽  
Frequency Measurements ◽  
Thermal Spectrum

Brightness distributions and flux densities at 8�8 GHz are presented for 12 small-diameter radio sources near the galactic plane. Each of these sources has been classified at one time or another as a supernova remnant. For one source, G295� 2 - 0�6, the flux density at 8�8 GHz confirms the thermal spectrum suggested by lower frequency measurements and indicates that it is not a supernova remnant. Another source, G309� 6+ 1�7, is thought to be extragalactic.

scholarly journals The X-Ray Emission of a Clumpy Irregular Galaxy from Thousands of Supernova Remnants?

1983 ◽  
Vol 101 ◽  
pp. 591-595
Author(s):  
D. S. Heeschen ◽  
J. Heidmann
Keyword(s):  
Flux Density ◽  
Power Law ◽  
Supernova Remnants ◽  
Hii Regions ◽  
Spectral Information ◽  
Irregular Galaxy ◽  
X Ray ◽  
Optical Position ◽  
Irregular Galaxies ◽  
30 Doradus

Clumpy irregular galaxies contain 5–10 “clumps” which are hyperactive HII complexes each equivalent to 100 giant HII regions of the 30 Doradus type (Heidmann 1982). We observed one of them, Mkn 325 (= NGC 7673), with the Einstein IPC in Dec. 1980 (seq.no 10201) for 3,200 s. The reduction was made kindly by D.E. Harris. The source was localized at 23h 25m 12.2s, + 23° 18′ 25″ (1950) in agreement with the optical position, at a quite weak level (14 counts in the 1.4–2.9 kev range). Thus we could not get valuable spectral information, only that the spectrum is rather not soft. Correction for galactic absorption NH = 5 ×1020 at.cm−2 (Heyles 1975) is applied. Fits of power law spectra happen to all go through the point with flux density 4.5 ×10−5 mJy at 3.0 ×1017 Hz (1.24 kev) and they yield a flux (1.1 ± 0.3) x10−13 erg cm−2 s−1 inside 1–3 kev and an X-luminosity (2.2 ± 0.3)×1041 erg s−1 inside 0.5–4.5 kev, for a distance 49 Mpc.

scholarly journals A search for candidate radio supernova remnants in the nearby irregular starburst galaxies NGC 4214 and NGC 4395

2005 ◽  
pp. 101-110 ◽  
Author(s):  
B. Vukotic ◽  
I. Bojicic ◽  
T.G. Pannuti ◽  
Dejan Urosevic
Keyword(s):  
Supernova Remnants ◽  
Hii Regions ◽  
Mean Value ◽  
Starburst Galaxies ◽  
Starburst Galaxy ◽  
Radio Sources ◽  
Mean Values ◽  
The Mean ◽  
Ngc 4395 ◽  
Discrete Radio Sources

We present the results of a search for new candidate radio su?pernova remnants (SNRs) in the nearby starburst irregular galaxies NGC 4214 and NGC 4395 using archived radio observations made with the Very Large Array (VLA) at the wavelengths of 3.5 cm, 6 cm and 20 cm for NGC 4214 and 6 cm and 20 cm for NGC 4395. These observations were analyzed as part of our ongoing search for candidate radio SNRs in nearby galaxies: the goal of this search is to prepare a large sample of candidate radio SNRs for the purpose of a robust statistical study of the properties of these sources. Based on our analysis, we have confirmed the nonthermal nature of the discrete radio sources ? and ? in NGC 4214 and classify these sources as candidate radio SNRs based on their positional coincidences with HII regions in that galaxy. We have measured the flux densities of the two candidate radio SNRs at each wavelength and calculated corresponding spectral indices: we have also measured flux densities of two other discrete radio sources in these galaxies - ? in NGC 4214 and #3 in NGC 4395 which we suspect to be additional candidate radio SNRs based on their positional coincidences with other HII regions in these galaxies. However, the radio data presently available for these sources can?not confirm such a classification and additional observations are needed. We have also calculated the radio luminosities Lradio at the wavelength of 20 cm for these two candidate radio SNRs as well as the corresponding values for the minimum total energy Emin required to power these radio sources via synchrotron emission and the corresponding magnetic field strength Bmin. We have compared our mean calculated values for these properties with the mean values for populations of candidate radio SNRs in other starburst galaxies: while the values for Lradio and Bmin are roughly comparable to the values seen in other starburst galaxies, the mean value for Emin is higher than the mean value of any other starburst galaxy. Finally, we include these two candidate radio SNRs in a discussion of the ? ? D relation for extragalactic candidate radio SNRs and find that these sources are located on the shallower end of the master ? ? D relation for all extragalactic SNRs as derived by Urosevic et al.(2005). .

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