scholarly journals Optical and Ultraviolet Spectral Morphology of Luminous OB Stars in the Galaxy and the Magellanic Clouds

1986 ◽  
Vol 116 ◽  
pp. 185-198 ◽  
Author(s):  
Nolan R. Walborn
Keyword(s):  
High Resolution ◽  
Hubble Space Telescope ◽  
Optical Data ◽  
High Resolution Data ◽  
Ob Stars ◽  
Central Cluster ◽  
Distant Galaxies ◽  
The Galaxy ◽  
H Ii Region ◽  
30 Doradus

Three areas of current progress relevant to the theme of this Symposium will be discussed. (1) New spectroscopic observations of the 30 Doradus central cluster, obtained independently by the author and by J. Melnick, confirm the presence of numerous very early O-type members, including several of type O3. In combination with sophisticated new direct imagery of the luminous central object R136 by A. Walker and by G. Weigelt, these results have evident implications for understanding the ionization of the supergiant H II region, as well as for the interpretation of R136 itself and of the apparently similar regions seen in more distant galaxies. In particular, no evidence remains for a supermassive object in 30 Doradus, but its central cluster is revealed as a spectacular grouping of very massive hot stars. (2) A further member of the Ofpe/WN9 category in the LMC has been identified, bringing their number to seven, with no exact spectroscopic counterparts yet known in the Galaxy. One of these objects is currently in a state of outburst and has been interpreted by O. Stahl et al. as the hottest known Hubble-Sandage variable. (3) An extensive survey of IUE high-resolution data has revealed a strong correlation between the ultraviolet stellar wind features and the optical spectral classifications for the majority of normal O stars. These results are relevant to future studies with the High Resolution Spectrograph on the Hubble Space Telescope, which may observe restricted UV wavelength ranges in faint extragalactic OB stars lacking optical data of comparable quality.

scholarly journals The Stellar Content of 30 Doradus

1984 ◽  
Vol 108 ◽  
pp. 243-253
Author(s):  
Nolan R. Walborn
Keyword(s):  
Large Magellanic Cloud ◽  
Stellar Content ◽  
Multiple Systems ◽  
Central Cluster ◽  
Distant Galaxies ◽  
Good Accord ◽  
The Galaxy ◽  
Spectroscopic Information ◽  
H Ii Region ◽  
30 Doradus

The supergiant H II region 30 Doradus is placed in context as the optically most spectacular component in a much larger region of recent and current star formation in the Large Magellanic Cloud, as shown by deep Hα photographs and the new IRAS results. The current state of knowledge concerning the concentrated central cluster in 30 Dor is summarized. Spectroscopic information exists for only 24 of the brightest members, most of which are WR stars; however, photometry shows over 100 probable members earlier than BO. The spectral classification of these stars is a difficult observational problem currently being addressed; in the meantime their hypothetical ionizing luminosity is calculated from the photometry and compared with that suggested for the superluminous central object R136a alone, and with the H II region luminosity. With reference to related regions in the Galaxy, the likelihood that many of the brightest objects in 30 Dor are multiple systems is emphasized. An interpretation of R136a as a system containing a few very massive stars (as opposed to a single supermassive object) is in good accord with the observations, including the visual micrometer results. The study of 30 Dor and its central cluster is vital for an understanding of the numerous apparently similar regions now being discovered in more distant galaxies.

scholarly journals High-Resolution B-Photometry of the Milky Way and Results on Galactic Structure

1990 ◽  
Vol 139 ◽  
pp. 205-206
Author(s):  
S. Kimeswenger ◽  
W. Schlosser ◽  
K. J. Seidensticker ◽  
B. Hoffmann ◽  
Th. Schmidt-Kaler
Keyword(s):  
High Resolution ◽  
Milky Way ◽  
Galactic Structure ◽  
Surface Photometry ◽  
High Resolution Data ◽  
V Band ◽  
The Galaxy ◽  
Global Parameters ◽  
Pioneer 10 ◽  
Resolution Data

During the last two decades, many attempts were made to determine the global parameters of the Galaxy and to compare the Galaxy to other galaxies (Schmidt-Kaler and Schlosser 1973; de Vaucouleurs and Pence 1978; Gilmore 1984; van der Kruit 1986). While most of these investigations are based on star counts, a detailed overall study by surface photometry, because of the lack of homogeneous high-resolution data, is rare. The last attempt by van der Kruit (1986), based on Pioneer 10 data, suffered from low resolution. The great number of individual structures at low and even intermediate latitudes could not be recognized. Our work (B-band, Hoffmann et al. 1989, this volume; V-band, Schlosser, Schmidt-Kaler, and Schneider 1989; U-Band and R-band photometry, in preparation) provides this homogeneous high-resolution data.

scholarly journals Massive Star Formation in W49

1987 ◽  
Vol 115 ◽  
pp. 143-145
Author(s):  
J. Dreher ◽  
S. Vogel ◽  
S. Terebey ◽  
W. J. Welch
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Massive Star ◽  
Hii Regions ◽  
Molecular Line ◽  
The Galaxy ◽  
Molecular Lines ◽  
H Ii Region ◽  
Scale Structures ◽  
The Continuum

W49 is the most luminous H II region complex in the galaxy. VLA maps in the continuum reveal a complex of more than two dozen compact HII regions, including a ring-like distribution of a dozen such regions within a volume of 1 pc. In addition to the VLA maps, we have obtained high resolution maps in this field with the Hat Creek Millimeter Interferometer in the following molecular lines: HCO+(1-0), H13CO+(1-0), SiO(v = 0, J = 2-1), SiO(v = 1, J = 2-1), H13CN(1-0), HC15N(1-0), SO2 [8(3,5)-9(2,8)], SO2[8(1,7)-8(0,8)], SO[2(2)-1(1)], and CH3CH2CN[10(1,10)-9(1,9)], all near 3 mm wavelengh. These maps will be discussed. The HCO+distribution corresponds to the larger scale structures observed in the continuum maps. In contrast the SO and SiO sources are quite compact. Using the detailed molecular line results obtained in the ORION/KL region as a guide, we are able to identify these latter sources as regions in which the star formation is at an earlier stage, regions where there are outflows.

scholarly journals The Luminous Stellar Content of 30 Doradus and NGC 3603 - The Nearest Visible Giant HII Regions

1986 ◽  
Vol 116 ◽  
pp. 233-234
Author(s):  
A.F.J. Moffat ◽  
M.M. Shara ◽  
W. Seggewiss
Keyword(s):  
Spatial Resolution ◽  
Hii Regions ◽  
Stellar Content ◽  
Distant Galaxies ◽  
The Galaxy ◽  
30 Doradus

30 Dor in the LMC and NGC 3603 in the Galaxy are the nearest visible examples of similar giant (or even more massive supergiant) HII regions being studied in other more distant galaxies, where spatial resolution is a much more serious problem. Hence, understanding 30 Dor and NGC 3603 may provide important clues to understanding extragalactic giant HII regions in general.

scholarly journals A High Resolution Optical Summary of the Structure and Dynamics of 30 Doradus

1999 ◽  
Vol 190 ◽  
pp. 249-250
Author(s):  
P. Scowen ◽  
Y.-H. Chu ◽  
R. Gruendl
Keyword(s):  
High Resolution ◽  
Hubble Space Telescope ◽  
Velocity Fields ◽  
Space Telescope ◽  
Structure And Dynamics ◽  
30 Doradus

We present the first comparison between high resolution echelle velocity fields and a mosaic of all Hubble Space Telescope narrowband observations of 30 Doradus.

scholarly journals A New Age and Distance for I Zw 18, the Most Metal-Poor Galaxy in the Nearby Universe

2008 ◽  
Vol 4 (S255) ◽  
pp. 387-391
Author(s):  
A. Aloisi ◽  
G. Clementini ◽  
M. Tosi ◽  
F. Annibali ◽  
R. Contreras ◽  
...  
Keyword(s):  
High Resolution ◽  
Early Universe ◽  
Dwarf Galaxy ◽  
Hubble Space Telescope ◽  
Local Universe ◽  
Photometric Observations ◽  
The Galaxy ◽  
Cepheid Variables ◽  
History Of ◽  
Blue Compact Dwarf Galaxy

AbstractThe blue compact dwarf galaxy I Zw 18 holds the record of the lowest metallicity ever observed in the local universe. As such, it represents the closest analog to primordial galaxies in the early universe. More interestingly, it has recurrently been regarded as a genuinely young galaxy caught in the process of forming in the nearby universe. However, stars of increasingly older ages are found within I Zw 18 every time deeper high-resolution photometric observations are performed with the Hubble Space Telescope (HST): from the original few tens of Myrs to, possibly, several Gyrs. Here we summarize the history of I Zw 18 age and present an ongoing HST/ACS project which allowed us to precisely derive the galaxy distance by studying its Cepheid variables, and to firmly establish the age of its faintest resolved populations.

scholarly journals Star formation in NGC 3603

1999 ◽  
Vol 193 ◽  
pp. 499-500
Author(s):  
Mauricio Tapia ◽  
Brenda Pérez
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Lower Mass ◽  
The Core ◽  
Near Ir ◽  
H Ii Region ◽  
Very High ◽  
30 Doradus

NGC 3603 is the most massive optically visible H II region in our Galaxy and is considered to be the Galactic analogue to 30 Doradus and, thus, a prototype of the starburst phenomenon. Its core, known as WR 43 (HD 97950), contains several dozens of O-B0 stars within 35″. These have been studied with very high resolution in the optical and near-IR. Melnick, Tapia & Terlevich (1989) concluded that the starburst cluster has an age spread of 1 to 2 Myr and that its boundaries extend to ∼60″, while Eisenhauer et al. (1998) determined that the lower mass stars in the core are younger than 1 Myr.

scholarly journals Spectra of the Wolf-Rayet Stars in 30 Doradus

1982 ◽  
Vol 99 ◽  
pp. 551-554
Author(s):  
Peter S. Conti
Keyword(s):  
High Resolution ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Central Cluster ◽  
30 Doradus

The central cluster of the 30 Doradus complex in the Large Magellanic Cloud (LMC) contains at least a dozen Wolf-Rayet (W-R) stars of the nitrogen sequence according to Melnick (1978). In addition to the six stars previously identified by Feast, Thackeray and Wesselinck (1960), Melnick identified an additional six using an Echele spectrograph on the 1.52 m telescope at La Silla. I have obtained high resolution spectra of ten of these stars and would like to discuss the spectral types.

scholarly journals Cobalt and copper abundances in 56 Galactic bulge red giants

2020 ◽  
Vol 640 ◽  
pp. A89
Author(s):  
H. Ernandes ◽  
B. Barbuy ◽  
A. C. S. Friaça ◽  
V. Hill ◽  
M. Zoccali ◽  
...  
Keyword(s):  
High Resolution ◽  
Red Giants ◽  
High Resolution Data ◽  
Mean Values ◽  
Chemical Enrichment ◽  
Very Large Telescope ◽  
The Galaxy ◽  
Observed Behaviour ◽  
Red Clump ◽  
Secondary Element

Context. The Milky Way bulge is an important tracer of the early formation and chemical enrichment of the Galaxy. The abundances of different iron-peak elements in field bulge stars can give information on the nucleosynthesis processes that took place in the earliest supernovae. Cobalt (Z = 27) and copper (Z = 29) are particularly interesting. Aims. We aim to identify the nucleosynthesis processes responsible for the formation of the iron-peak elements Co and Cu. Methods. We derived abundances of the iron-peak elements cobalt and copper in 56 bulge giants, 13 of which were red clump stars. High-resolution spectra were obtained using FLAMES-UVES at the ESO Very Large Telescope by our group in 2000–2002, which appears to be the highest quality sample of optical high-resolution data on bulge red giants obtained in the literature to date. Over the years we have derived the abundances of C, N, O, Na, Al, Mg; the iron-group elements Mn and Zn; and neutron-capture elements. In the present work we derive abundances of the iron-peak elements cobalt and copper. We also compute chemodynamical evolution models to interpret the observed behaviour of these elements as a function of iron. Results. The sample stars show mean values of [Co/Fe] ~ 0.0 at all metallicities, and [Cu/Fe] ~ 0.0 for [Fe/H] ≥−0.8 and decreasing towards lower metallicities with a behaviour of a secondary element. Conclusions. We conclude that [Co/Fe] varies in lockstep with [Fe/H], which indicates that it should be produced in the alpha-rich freezeout mechanism in massive stars. Instead [Cu/Fe] follows the behaviour of a secondary element towards lower metallicities, indicating its production in the weak s-process nucleosynthesis in He-burning and later stages. The chemodynamical models presented here confirm the behaviour of these two elements (i.e. [Co/Fe] vs. [Fe/H] ~constant and [Cu/Fe] decreasing with decreasing metallicities).

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