scholarly journals Supernova Remnants in Giant HII Regions

1988 ◽  
Vol 101 ◽  
pp. 201-204
Author(s):  
You-Hua Chu ◽  
Robert C. Kennicutt
Keyword(s):  
Supernova Remnants ◽  
Detection Rate ◽  
Massive Stars ◽  
Line Emission ◽  
Hii Regions ◽  
Radio Continuum ◽  
Hii Region ◽  
The Core ◽  
Large Numbers ◽  
Optical Line

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).

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

1973 ◽  
Vol 26 (2) ◽  
pp. 267 ◽  
Author(s):  
JR Dickel ◽  
DK Milne
Keyword(s):  
Supernova Remnants ◽  
Supernova Remnant ◽  
Line Emission ◽  
Hii Regions ◽  
Recombination Line ◽  
Hii Region ◽  
Galactic Source ◽  
Source Number

The galactic source number designations G35'6-0'4 and G35�5-0�0 in Table 1 should be interchanged. Thus G35'6-0'4 is the supernova remnant and G35�5 -0�0 appears to be an HII region. The authors thank Dr. T Velusamy for calling this error to their attention.

scholarly journals How to form a 200 M⊙ star

1986 ◽  
Vol 116 ◽  
pp. 271-273 ◽  
Author(s):  
Hans Zinnecker
Keyword(s):  
Massive Stars ◽  
Hii Regions ◽  
Stellar Mass ◽  
Mass Limit ◽  
The Core ◽  
Dense Cluster

Stellar coalescence is suggested as a possible mechanism for doubling the upper stellar mass limit from ∼100M⊙ to ∼200M⊙ in a moderately dense cluster of a few hundred young massive stars (∼105 M⊙ pc−3). The merger will be between the two components of the dominant central tight binary formed in the core of the cluster by the N-body evolution. This process may occur in some giant extragalactic HII regions.

Observations of the 1→0 Transition of CO Towards Southern HII Regions

1982 ◽  
Vol 4 (4) ◽  
pp. 434-440 ◽  
Author(s):  
J. B. Whiteoak ◽  
Robina E. Otrupcek ◽  
C. J. Rennie
Keyword(s):  
Radio Telescope ◽  
Molecular Cloud ◽  
Milky Way ◽  
Line Emission ◽  
Hii Regions ◽  
Hii Region ◽  
Giant Molecular Cloud ◽  
Molecular Lines ◽  
Csiro Division

The 4-m radio telescope of the CSIRO Division of Radiophysics at Epping is being used to survey the line emission associated with the 1→0 transition of CO (rest frequency 115.271 GHz) in the southern Milky Way. The programme includes mapping the CO distribution across giant molecular-cloud/HII-region complexes. As a first stage the emission has been observed towards bright southern HII regions. These results will not only serve as a basis for future extensive mapping but will also provide data which is directly comparable with observations of other molecular lines that have been made towards the HII regions.

scholarly journals The Kinematics of Pulsars

1987 ◽  
Vol 125 ◽  
pp. 23-33
Author(s):  
A.G. Lyne
Keyword(s):  
Binary System ◽  
Supernova Remnants ◽  
Massive Stars ◽  
Normal Population ◽  
Hii Regions ◽  
Close Binary System ◽  
Close Binary ◽  
The Galaxy ◽  
Motion Measurements ◽  
Halo Population

Pulsars have a galactic radial distribution similar to that of many galactic populations such as HII regions, massive stars and supernova remnants. However they are generally much further from the plane of the Galaxy than these objects. Proper motion measurements sho that this is because they are typically moving with high velocities. The measurements also indicate that most pulsars were formed a few million years ago close to the plane, within the normal Population I regions. Some pulsars will escape from the Galaxy, although the majority will end up in a halo population. The origin of the high velocities is not clear at present but may be due either to some asymme try in the formation event or to the disruption of a close binary system.

scholarly journals Giant H II Regions in M81

1986 ◽  
Vol 116 ◽  
pp. 503-504 ◽  
Author(s):  
Michele Kaufman ◽  
R. C. Kennicutt ◽  
F. N. Bash
Keyword(s):  
Star Formation ◽  
Hii Regions ◽  
Radio Continuum ◽  
H Ii Regions ◽  
Hii Region ◽  
Distant Galaxies ◽  
Flux Measurements ◽  
Selection Of

Giant HII regions are important tracers of recent star formation in distant galaxies. For a selection of HII regions in our galaxy where the exciting stars can be identified, Rumstay (1985) finds that the measured Hα and radio continuum luminosities of an HII region correlate with the stellar ionizing flux derived from model atmospheres and the known exciting stars. Therefore, we use flux measurements of giant HII regions as an index of the distribution of O stars in M81.

scholarly journals Radio emission during the formation of stellar clusters in M 33

2020 ◽  
Vol 639 ◽  
pp. A27
Author(s):  
Edvige Corbelli ◽  
Jonathan Braine ◽  
Fatemeh S. Tabatabaei
Keyword(s):  
Radio Emission ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Line Emission ◽  
Radio Continuum ◽  
Stellar Clusters ◽  
Nonthermal Radio ◽  
Early Formation ◽  
5 Ghz

Aims. We investigate thermal and nonthermal radio emission associated with the early formation and evolution phases of young stellar clusters (YSCs) selected by their mid-infrared (MIR) emission at 24 μm in M 33. We consider regions in their early formation period, which are compact and totally embedded in the molecular cloud, and in the more evolved and exposed phase. Methods. Thanks to recent radio continuum surveys between 1.4 and 6.3 GHz we are able to find radio source counterparts to more than 300 star forming regions of M 33. We identify the thermal free–free component for YSCs and their associated molecular complexes using the Hα line emission. Results. A cross-correlation of MIR and radio continuum is established from bright to very faint sources, with the MIR-to-radio emission ratio that shows a slow radial decline throughout the M 33 disk. We confirm the nature of candidate embedded sources by recovering the associated faint radio continuum luminosities. By selecting exposed YSCs with reliable Hα flux, we establish and discuss the tight relation between Hα and the total radio continuum at 5 GHz over four orders of magnitude. This holds for individual YSCs as well as for the giant molecular clouds hosting them, and allows us to calibrate the radio continuum–star formation rate relation at small scales. On average, about half of the radio emission at 5 GHz in YSCs is nonthermal with large scatter. For exposed but compact YSCs and their molecular clouds, the nonthermal radio continuum fraction increases with source brightness, while for large HII regions the nonthermal fraction is lower and shows no clear trend. This has been found for YSCs with and without identified supernova remnants and underlines the possible role of massive stars in triggering particle acceleration through winds and shocks: these particles diffuse throughout the native molecular cloud prior to cloud dispersal.

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 Massive Stars and Giant HII Regions: The High-Energy Picture

1991 ◽  
Vol 143 ◽  
pp. 397-408
Author(s):  
Thierry Montmerle
Keyword(s):  
Supernova Remnants ◽  
Massive Stars ◽  
Hii Regions ◽  
High Energy ◽  
X Rays ◽  
High Energy Radiation ◽  
Low Mass ◽  
Γ Rays ◽  
Pms Stars

Giant HII regions contain highly energetic objects: luminous, massive stars (including Wolf-Rayet stars) generating powerful winds, as well as, often, supernova remnants. These objects interact with the surrounding gas by creating shock waves. Part of the energy input is radiated away in the form of X-rays; also, protons and electrons may be accelerated in situ and generate γ-rays by collisions with the ionized gas. In addition, the stars themselves (including the accompanying low-mass PMS stars) are sources of X-rays, and W-R stars may emit continuum y-rays and are associated with nuclear γ-ray lines seen in the interstellar medium. Therefore, both through the stars they contain and through interactions within the gas, giant HII regions are, in addition to their more traditional properties and over nearly 7 decades in energy, important sources of high-energy radiation.

scholarly journals High-Redshift Radio Galaxies

1995 ◽  
Vol 10 ◽  
pp. 543-546
Author(s):  
George Miley
Keyword(s):  
Galaxy Formation ◽  
High Redshift ◽  
Line Emission ◽  
Optical Emission ◽  
Delta Function ◽  
Radio Galaxies ◽  
Radio Continuum ◽  
Spatially Resolved ◽  
A Value ◽  
Optical Line

Radio galaxies are unique cosmological probes. As with radio-loud quasars, the presence of luminous radio continuum and optical line emission enable radio galaxies to be observed and recognized at large distances, up to z = 4.2. However, unlike the situation for most quasars, their optical emission can be spatially resolved from the ground and studied in detail.Progress in detecting distant radio galaxies has been rapid in recent years due to the use of CCDs and the exploitation of new selection criteria. Now, more than 60 radio galaxies are known with z > 2. More than half of these have been found by our group by concentrating on radio sources with the steepest spectra, most of these in a “Key Programme” of the European Southern Observatory. Although several people contributed to this Key Programme, most of the work was done by Huub Röttgering, who presented his Ph.D thesis in January and Rob van Ojik, who succeededhim. Redshifts of 1.5 to 4 correspond to a time when the Universe was 10% -20% of its present age. This was a crucial period in history when galaxy formation must have been rampant. It corresponds to the AGN era, a two-billion year “delta function” in the population evolution of luminous quasars and radio galaxies, when their space-density rose to a value several hundred times larger than the present density before the species mysteriously and suddenly became almost extinct.

Sign in / Sign up

Export Citation Format

Share Document