scholarly journals Atlas of Main-line OH Masers in the Galactic Longitude Range 3° to 60°

1983 ◽  
Vol 36 (3) ◽  
pp. 417 ◽  
Author(s):  
JL Caswell ◽  
RF Haynes
Keyword(s):  
Star Formation ◽  
Circular Polarization ◽  
Galactic Plane ◽  
Hii Regions ◽  
Main Line ◽  
Late Type ◽  
Circumstellar Shells ◽  
Many Sources ◽  
First Time ◽  
Galactic Longitude

We tabulate all 55 OH main-line masers discovered to date in the galactic plane between longitude 3� and 60�. For most of these we show current spectra, which have been taken with the Parkes 64 m radio telescope, in both senses of circular polarization on the 1665 MHz and/or 1667 MHz transitions; for some sources we give new position estimates, and several sources are reported for the first time. We discuss many sources individually and note that while most of the main-line OH masers probably pinpoint compact HII regions and sites of current star formation, a few appear to be unusual varieties occurring in circumstellar shells, possibly associated with late-type stars.

scholarly journals Building up mass in the centers of late type galaxies

2007 ◽  
Vol 3 (S245) ◽  
pp. 169-172
Author(s):  
E. Schinnerer ◽  
T. Böker ◽  
E. Emsellem ◽  
U. Lisenfeld ◽  
D. Downes
Keyword(s):  
Star Formation ◽  
Gas Flow ◽  
Line Emission ◽  
Hii Regions ◽  
Small Scale ◽  
Molecular Gas ◽  
Late Type ◽  
Central Mass ◽  
Ngc 6946 ◽  
First Time

AbstractWe present highest angular resolution (~ 1″ and 0.35″) mm-interferometric observations of the HCN(1-0), 12CO(1-0) and 12CO(2-1) line emission in the central 300 pc of the late-type spiral galaxy NGC 6946. The data, obtained with the IRAM Plateau de Bure Interferometer (PdBI) shows for the first time a molecular gas spiral in the inner ~ 10″ (270 pc) with a large concentration of molecular gas ($M_{H_2} \sim\,1.6\times10^7\,M_{\odot}$) within the inner 60 pc, The gas distribution in the central 50 pc has been resolved and is consistent with a gas ring or spiral driven by a bar. Both the distribution of the molecular gas as well as its kinematics can be well explained by the influence of an inner stellar bar of about 400 pc length as tested via a qualitative model for the gas flow. NGC 6946 is a prime example of molecular gas kinematics being driven by a small-scale, secondary stellar bar.For the first time, it is possible to directly compare the location of (dense) giant molecular clouds with that of (optically) visible HII regions in space-based images. We use the 3 mm continuum and the HCN emission to estimate in the central 50 pc the star formation rates in young clusters that are still embedded in their parent clouds and hence are missed in optical and near-IR surveys of star formation. The amount of embedded star formation is about 1.6 times as high as that measured from HII regions alone, and appears roughly evenly split between ongoing dust-obscured star formation and very young giant molecular cloud cores that are just beginning to form stars. The build-up of central mass seems to have continued over the past ≥ 10 Myrs, to have occurred in an extended (albeit small) volume around the nucleus, and to be closely related to the presence of an inner bar.

scholarly journals Luminosity function, star density, and star formation efficiency in regions of star formation - near infrared observations -

1991 ◽  
Vol 147 ◽  
pp. 289-292
Author(s):  
Klaus-Werner Hodapp ◽  
John Rayner ◽  
Hua Chen
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Near Infrared ◽  
Hii Regions ◽  
Young Stars ◽  
Young Age ◽  
Infrared Observations ◽  
Star Density ◽  
Many Sources ◽  
Formation Efficiency

Clusters of young stars have been found near a number of compact HII regions. These clusters do not show a turnover in the K-band luminosity and are probably several million years old. In L 1641 only moderate clustering tendency has been observed and many sources show signs of extremely young age.

scholarly journals THE SINO-GERMAN λ6 CM POLARIZATION SURVEY OF THE GALACTIC PLANE: A SUMMARY

2013 ◽  
Vol 23 ◽  
pp. 82-91 ◽  
Author(s):  
J. L. HAN ◽  
W. REICH ◽  
X. H. SUN ◽  
X. Y. GAO ◽  
L. XIAO ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Interstellar Medium ◽  
Radio Telescope ◽  
Supernova Remnants ◽  
Galactic Plane ◽  
High Sensitivity ◽  
Hii Regions ◽  
Galactic Latitude ◽  
Galactic Longitude ◽  
Individual Objects

We have finished the λ6 cm polarization survey of the Galactic plane using the Urumqi 25 m radio telescope. It covers 10° ≤ l ≤ 230° in Galactic longitude and |b| ≤ 5° in Galactic latitude. The new polarization maps not only reveal new properties of the diffuse magnetized interstellar medium, but also are very useful for studying individual objects such as HII regions, which may act as Faraday screens with strong regular magnetic fields inside, and supernova remnants for their polarization properties and spectra. The high sensitivity of the survey enables us to discover two new SNRs G178.2–4.2 and G25.3–2.1 and a number of HII regions.

scholarly journals The First EUV Survey: White Dwarfs and Cool Stars

1992 ◽  
Vol 9 ◽  
pp. 241-245
Author(s):  
C. Jordan ◽  
K.A. Pounds
Keyword(s):  
White Dwarfs ◽  
Galactic Plane ◽  
Cataclysmic Variables ◽  
Wide Field ◽  
Late Type ◽  
Systematic Analysis ◽  
Cool Stars ◽  
To Come ◽  
Galactic Longitude

AbstractPreliminary results from the survey carried out with the Wide Field Camera (WFC) on ROS AT are presented. 732 sources were detected, of which 230 were observable in both the S1 and S2 filters. The distribution of sources with galactic longitude, near the galactic plane, shows the greatest number in the quadrant where H I absorption is least. The identifiable sources include a high proportion of hot white dwarfs and ‘normal’ late-type stars. The optical follow-up programme has identified over 40 new white dwarfs and over 60 late-type stars including RS CVn systems and cataclysmic variables. Emission from some A stars detected appears to come from white dwarf companions. Individual sources of particular interest are discussed. The systematic analysis of a sample of late-type stars has begun.

scholarly journals The Arecibo Methanol Maser Galactic Plane Survey

2007 ◽  
Vol 3 (S242) ◽  
pp. 208-212
Author(s):  
Jagadheep D. Pandian ◽  
Paul. F. Goldsmith ◽  
Avinash A. Deshpande
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Galactic Plane ◽  
Density Level ◽  
Massive Star Formation ◽  
Methanol Maser ◽  
Methanol Masers ◽  
Galactic Longitude ◽  
Early Phases ◽  
Spiral Arm

AbstractThe Arecibo Methanol Maser Galactic Plane Survey (AMGPS) is a blind survey for 6.7 GHz methanol masers in a section of the Galactic plane visible from the Arecibo radio telescope. The survey for these signposts of massive star formation is complete at a flux density level of 0.27 Jy making it the most sensitive blind survey for methanol masers carried out to date, and resulted in the detection of 86 methanol masers, 48 of which are new discoveries. The properties of methanol masers discovered in the survey are consistent with their being associated with early phases of massive star formation. The data also show the tangent point of the Carina-Sagittarius spiral arm to be around a Galactic longitude of 49.6°.

scholarly journals Luminosity function, star density, and star formation efficiency in regions of star formation - near infrared observations -

1991 ◽  
Vol 147 ◽  
pp. 289-292
Author(s):  
Klaus-Werner Hodapp ◽  
John Rayner ◽  
Hua Chen
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Near Infrared ◽  
Hii Regions ◽  
Young Stars ◽  
Young Age ◽  
Infrared Observations ◽  
Star Density ◽  
Many Sources ◽  
Formation Efficiency

Clusters of young stars have been found near a number of compact HII regions. These clusters do not show a turnover in the K-band luminosity and are probably several million years old. In L 1641 only moderate clustering tendency has been observed and many sources show signs of extremely young age.

scholarly journals A Search For “Young Galaxies”

1984 ◽  
Vol 78 ◽  
pp. 395-396
Author(s):  
R. McMahon ◽  
R. Terlevich ◽  
C. Hazard ◽  
M. Irwin ◽  
J. Melnick
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Hii Regions ◽  
High Rate ◽  
Irregular Galaxies ◽  
Objective Prism ◽  
Absolute Magnitudes ◽  
The Uk ◽  
First Time ◽  
Low Dispersion

Among the most interesting objects found on low dispersion IllaJ objective prism plates taken with the UK Schmidt telescope are a large number of compact and intrinsically very bright ‘extragalactic HII regions’. Spectroscopically they are indistinguishable from the giant HII regions found in spiral and irregular galaxies except that they are much more luminous with absolute magnitudes in the range My -14 to -23. The stellar continuum is extremely blue indicating a predominantly young stellar population. The Hf3 luminosities, 1038 to 1042 ergs/sec indicate that they must contain 105 - 107 OB stars with a total mass in stars of 106 - 109 Mʘ. The associated high rate of star formation cannot have continued for more than 107 years, which implies that these systems are either undergoing star formation for the first time, or that they undergo intermittent bursts of star formation. The chemical composition of these systems is also remarkable in that the oxygen abundance is invariably less than solar.

scholarly journals H2O Masers in the Galactic Plane. I. Longitude 340º to the Galactic Centre

1983 ◽  
Vol 36 (3) ◽  
pp. 401 ◽  
Author(s):  
JL Caswell ◽  
RA Batchelor ◽  
JR Forster ◽  
KJ Wellington
Keyword(s):  
Galactic Plane ◽  
Main Line ◽  
Galactic Centre ◽  
Type I ◽  
Late Type

Twenty-five new H20 masers in the southern galactic plane have been discovered using a 22 GHz maser receiver on the Parkes telescope. The search was conducted at the locations of all the known 1665 MHz OH masers in the longitude range 340� through the galactic centre to 2�; of the 46 type I OH masers 38 are now found to have an H20 maser nearby; three other main-line OH emitters, possibly unusual late-type stars, also show H20 emission. We give an up-to-date tabulation of all 46 currently known H20 masers in the region which includes for completeness several H20 masers with no readily detectable associated type I OH emission.

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