scholarly journals Stellar content of obscured compact H II regions

2003 ◽  
Vol 212 ◽  
pp. 467-473 ◽  
Author(s):  
Margaret M. Hanson ◽  
Lex Kaper ◽  
Arjan Bik ◽  
Fernando Comerón ◽  
Joachim Puls ◽  
...  
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
Massive Stars ◽  
Model Atmosphere ◽  
Spectroscopic Studies ◽  
H Ii Regions ◽  
Stellar Content ◽  
High Quality ◽  
Physical Conditions

Near-infrared, spectroscopic studies of central ionizing sources of very young H ii regions is presented in conjunction with a recently available, sophisticated atmospheric code to constrain the physical conditions and environment of very massive stars at very early stages of evolution. Combining high quality near-infrared spectroscopy of very young massive stars with model atmosphere calculations should allow for the most accurate quantitative determination of Teff, rotation, L, and log g, and to search for binaries and possible disk or in-fall signatures in forming or recently formed massive stars. These characteristics make up a vital boundary condition constraining theories on massive star formation.

scholarly journals Spectroscopy of the Ionizing Sources of UC HII Regions

2002 ◽  
Vol 12 ◽  
pp. 167-169
Author(s):  
Margaret M. Hanson
Keyword(s):  
Near Infrared ◽  
Massive Stars ◽  
Hii Regions ◽  
Spectroscopic Studies ◽  
Physical Conditions ◽  
Early Stages ◽  
Infrared Spectroscopic

AbstractThe utility of near-infrared, spectroscopic studies of central ionizing sources of UC HII regions is presented, in conjunction with a recently available, sophisticated atmospheric code, to constrain the physical conditions and environment of very massive stars at extremely early stages of evolution.

scholarly journals Spectroscopic Studies of Er3+-Yb3+ Codoped Multicomposition Tellurite Oxide Glass

2014 ◽  
Vol 895 ◽  
pp. 323-333 ◽  
Author(s):  
Sharudin Omar Baki ◽  
L.S. Tan ◽  
C.S. Kan ◽  
Halimah Mohamed Kamari ◽  
A.S.M. Noor ◽  
...  
Keyword(s):  
Room Temperature ◽  
Near Infrared ◽  
Transition Probabilities ◽  
Branching Ratios ◽  
Spectroscopic Studies ◽  
Oxide Glass ◽  
Near Infrared Spectra ◽  
Intensity Parameters ◽  
Measured Absorption

Multicomposition of Er3+-Yb3+codoped tellurite oxide, TeO2-ZnO-PbO-TiO2-Na2O glass has been investigated. Detailed spectroscopic study of the Judd-Ofelt analysis has been performed from the measured absorption spectrum in order to obtain the intensity parameters Ωt(t=2, 4, 6). The calculated Ωtvalues were then utilized in the determination of transition probabilities, radiative lifetimes and branching ratios of the Er3+transitions between theJ(upper)-J(lower) manifolds. Both visible upconversion and near-infrared spectra were characterized under the 980 nm laser diode excitation at room temperature.

The Nature of Boxy/Peanut Spiral Galaxies: Overview and New Results

1997 ◽  
Vol 14 (2) ◽  
pp. 146-158 ◽  
Author(s):  
M. Bureau ◽  
K. C. Freeman
Keyword(s):  
Formation Mechanism ◽  
Vertical Structure ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Spiral Galaxies ◽  
Physical Conditions ◽  
Bar Buckling ◽  
Line Imaging ◽  
Observational Program

AbstractThe formation mechanism of boxy/peanut-shaped bulges in spiral galaxies has been a problem for many years. We briefly review here the possible formation scenarios for boxy/peanut bulges, concentrating on both the bar-buckling and accretion hypotheses, and then describe an observational program aimed at testing those various theories and studying the vertical structure of edge-on bars. Our program includes optical long-slit spectroscopy, Hiline-imaging, near-infrared imaging, and multi-band optical imaging. New spectroscopic results (both optical and Hi) are presented on seven galaxies, including five boxy/peanut-bulge spirals. Based on Kuijken & Merrifield's (1995) idea for detecting edge-on bars, we argue that these observations constitute a strong case in favour of the bar-buckling mechanism for the formation of boxy/peanut-shaped bulges, but they also raise many questions and prompt for more detailed modelling to be made. The implications of the observations concerning the determination of rotation curves and of the physical conditions in bulges are also discussed.

scholarly journals HII regions and star formation in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 139-144 ◽  
Author(s):  
Robert C. Kennicutt
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Massive Star ◽  
Massive Stars ◽  
Hii Regions ◽  
Magellanic Clouds ◽  
H Ii Regions ◽  
Distant Galaxies ◽  
Close Range ◽  
Mass Functions

The H II regions in the Magellanic Clouds provide an opportunity to characterize the global star formation properties of a galaxy at close range. They also provide a unique laboratory for testing empirical tracers of the massive star formation rates and initial mass functions in more distant galaxies, and for studying the dynamical interactions between massive stars and the interstellar medium. This paper discusses several current studies in these areas.

scholarly journals The Massive stellar Population at the Galactic Center

2016 ◽  
Vol 12 (S329) ◽  
pp. 287-291
Author(s):  
Francisco Najarro ◽  
Diego de la Fuente ◽  
Tom R. Geballe ◽  
Don F. Figer ◽  
D. John Hillier
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Milky Way ◽  
Local Group ◽  
Galactic Center ◽  
Spectroscopic Studies ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History

AbstractWe present results from our ongoing infrared spectroscopic studies of the massive stellar content at the Center of the Milky Way. This region hosts a large number of apparently isolated massive stars as well as three of the most massive resolved young clusters in the Local Group. Our survey seeks to infer the presence of a possible top-heavy recent star formation history and to test massive star formation channels: clusters vs isolation.

scholarly journals Searching for emission line and OB stars in Cl 1806-20 using a NIR narrow-band technique

2010 ◽  
Vol 6 (S272) ◽  
pp. 606-607 ◽  
Author(s):  
Michelle L. Edwards ◽  
Reba M. Bandyopadhyay ◽  
Stephen S. Eikenberry ◽  
Valerie J. Mikles ◽  
Dae-Sik Moon
Keyword(s):  
Emission Line ◽  
Massive Star ◽  
Near Infrared ◽  
Narrow Band ◽  
Massive Stars ◽  
Narrow Band Imaging ◽  
Ob Stars ◽  
Luminous Blue Variables ◽  
Upper Limit

AbstractWe survey the environment of Cl 1806-20 using near-infrared narrow-band imaging to search for Brγ features indicative of evolved massive stars. Using this technique, we successfully detect previously identified massive stars in the cluster. We detect no new emission line stars, establishing a firm upper limit on the number of Wolf Rayets and Luminous Blue Variables; however, we do find several candidate OB supergiants, which likely represent the bulk of the heretofore undiscovered massive star population.

scholarly journals Massive Stars in the Galactic Center

2007 ◽  
Vol 3 (S250) ◽  
pp. 257-264
Author(s):  
F. Martins ◽  
D. J. Hillier ◽  
R. Genzel ◽  
F. Eisenhauer ◽  
T. Ott ◽  
...  
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
Galactic Center ◽  
Massive Stars ◽  
Evolutionary Status ◽  
Infrared Spectral Range ◽  
Different Types ◽  
Infrared Spectral ◽  
Observational Techniques ◽  
Massive Clusters

AbstractWe present results of two studies aiming at better understanding the properties of massive stars in the Galactic Center. We focus on the youngest and oldest of the three massive clusters harboring this region, namely the Arches and central cluster. We show that the development of powerful observational techniques in the near infrared spectral range (mainly 3D spectroscopy) allows to uncover the entire massive star population in these clusters. Using CMFGEN models, we derive the classical stellar and wind properties of 46 stars, as well as their surface abundances. The latter allow us to investigate in detail their evolutionary status and to identify evolutionary sequences between different types of stars. We thus constrain stellar evolution in the upper part of the HR diagram.

scholarly journals The VLT-FLAMES Tarantula Survey

2018 ◽  
Vol 618 ◽  
pp. A73 ◽  
Author(s):  
F. R. N. Schneider ◽  
O. H. Ramírez-Agudelo ◽  
F. Tramper ◽  
J. M. Bestenlehner ◽  
N. Castro ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
High Redshift ◽  
Large Magellanic Cloud ◽  
Giant Molecular Clouds ◽  
Stellar Content ◽  
Massive Star Formation ◽  
Hii Region ◽  
Mass Distributions

The 30 Doradus (30 Dor) nebula in the Large Magellanic Cloud (LMC) is the brightest HII region in the Local Group and a prototype starburst similar to those found in high redshift galaxies. It is thus a stepping stone to understand the complex formation processes of stars in starburst regions across the Universe. Here, we have studied the formation history of massive stars in 30 Dor using masses and ages derived for 452 mainly OB stars from the spectroscopic VLT-FLAMES Tarantula Survey (VFTS). We find that stars of all ages and masses are scattered throughout 30 Dor. This is remarkable because it implies that massive stars either moved large distances or formed independently over the whole field of view in relative isolation. We find that both channels contribute to the 30 Dor massive star population. Massive star formation rapidly accelerated about 8 Myr ago, first forming stars in the field before giving birth to the stellar populations in NGC 2060 and NGC 2070. The R136 star cluster in NGC 2070 formed last and, since then, about 1 Myr ago, star formation seems to be diminished with some continuing in the surroundings of R136. Massive stars within a projected distance of 8 pc of R136 are not coeval but show an age range of up to 6 Myr. Our mass distributions are well populated up to 200 M⊙. The inferred IMF is shallower than a Salpeter-like IMF and appears to be the same across 30 Dor. By comparing our sample of stars to stellar models in the Hertzsprung–Russell diagram, we find evidence for missing physics in the models above log L/L⊙ = 6 that is likely connected to enhanced wind mass loss for stars approaching the Eddington limit. Our work highlights the key information about the formation, evolution and final fates of massive stars encapsulated in the stellar content of 30 Dor, and sets a new benchmark for theories of massive star formation in giant molecular clouds.

scholarly journals Massive Star Formation

2004 ◽  
Vol 221 ◽  
pp. 169-180
Author(s):  
Guido Garay
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Massive Star ◽  
Massive Stars ◽  
Critical Role ◽  
Detailed Knowledge ◽  
Theoretical Studies ◽  
Cloud Environment ◽  
Physical Processes ◽  
Physical Conditions

The understanding of the formation process of massive stars requires a detailed knowledge of the physical conditions of the cloud environment which is thought to play a critical role in determining the formation mechanism. In recent years there has been a rapid growth of observational and theoretical studies concerning the formation of massive stars. Here I review observational data gathered during the last few years which are providing key evidence concerning the physical processes that take place during the formation of massive stars.

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