scholarly journals Assessing the Stellar Population and the Environment of an H ii Region on the Far Side of the Galaxy*

2021 ◽  
Vol 911 (2) ◽  
pp. 91
Author(s):  
André-Nicolas Chené ◽  
Robert A. Benjamin ◽  
Sebastian Ramírez-Alegría ◽  
Jura Borissova ◽  
Radostin Kurtev ◽  
...  
Keyword(s):  
Stellar Population ◽  
The Galaxy ◽  
H Ii Region

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

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 LINER-like emission in red galaxies: evolutionary phase or recurring phenomenon?

2007 ◽  
Vol 3 (S245) ◽  
pp. 181-184
Author(s):  
Genevieve J. Graves
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Large Fraction ◽  
Optical Emission ◽  
Ionized Gas ◽  
Satellite Galaxy ◽  
The Galaxy ◽  
Evolutionary Phase ◽  
Interstellar Material ◽  
Red Galaxies

AbstractWe present recent results showing that a large fraction of red sequence galaxies contain ionized gas with LINER-like optical emission line ratios. This emission is more frequently found in galaxies with lower central velocity dispersion (σ) and these galaxies typically have younger mean ages than galaxies at the same σ which do not host emission. We suggest that the presence of LINER-like emission may be determined by the quantity of interstellar material in these galaxies and may be associated with the recent accretion of a gas-rich satellite galaxy or alternatively with stellar mass loss that declines as the galaxy stellar population ages.

scholarly journals Galactic starburst NGC 3603 from X-rays to radio

2003 ◽  
Vol 212 ◽  
pp. 515-522
Author(s):  
Anthony F.J. Moffat ◽  
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
X Rays ◽  
Stellar Content ◽  
Near Ir ◽  
The Galaxy ◽  
The Status ◽  
H Ii Region ◽  
Mass Segregation ◽  
Colliding Winds

While NGC 3603 is often quoted as the most massive visible Giant H ii Region in the Galaxy, there are other similar and even more massive regions now being found towards the inner Galaxy in the near-IR. Nevertheless, NGC 3603 still retains the status of clone to the dense core-object in 30 Dor, R 136 — but 7x closer and 49x less crowded! This paper summarizes the most recent findings concerning NGC 3603's color-magnitude diagram (CMD), initial mass function (IMF), mass segregation and stellar content — including its unusually luminous H-rich WNL members — down to its pre-main-sequence stars near the H-burning limit. Of special relevance are new high-resolution X-ray and radio images as related to merging/colliding winds and three massive proplyd-like objects. NGC 3603 is a somewhat younger, hotter, scaled-down version of typical starbursts found in other galaxies.

scholarly journals How to Model the Chemical Evolution of Galaxies

1993 ◽  
Vol 155 ◽  
pp. 557-566
Author(s):  
Joachim Köppen
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Time Scale ◽  
Life Time ◽  
Magellanic Clouds ◽  
Formation Time ◽  
List Type ◽  
The Galaxy ◽  
H Ii Region ◽  
Magellanic Stream

For a first interpretation of the comparison of observational data, the crude “Simple Model” of chemical evolution is quite useful. Since it has well been described in the literature (e.g. Pagel and Patchett 1975, Tinsley 1980), let us here just review the assumptions and whether they are satisfied: 1.The galaxy is a closed system, with no exchange of matter with its surroundings: For the solar neighbourhood this probably is not true (the infamous Gdwarf-“problem”, Pagel 1989b). For the Magellanic Clouds this is most certainly wrong, because of the presence of the Inter-Cloud Region and the Magellanic Stream, and evidence for interaction with each other and the Galaxy as well (cf. e.g. Westerlund 1990).2.It initially consists entirely of gas (without loss of generality of primordial composition): This is good approximation also for models with gas infall, as long as the infall occurs with a time scale shorter than the star formation time scale.3.The metal production of the average stellar generation (the yield y) is constant with time: Initially, it is reasonable to make this assumption. For tables of the oxygen yield see Koppen and Arimoto (1991).4.The metal rich gas ejected by the stars is completely mixed with the ambient gas. To neglect the finite stellar life times (“instantaneous recycling approximation”) is appropriate for elements synthesized in stars whose life time is much shorter than the star formation time scale, such as oxygen, neon, sulphur, and argon.5.The gas is well mixed at all times: We don't know. The dispersion of H II region abundances may give an indication. In the Magellanic Clouds Dufour (1984) finds quite a low value (±0.08 dex for oyxgen).

scholarly journals A New Sample of Thick Disk and Halo Stars

1995 ◽  
Vol 164 ◽  
pp. 386-386
Author(s):  
C. Soubiran ◽  
M.N. Perrin ◽  
R. Cayrel ◽  
E. Chereul
Keyword(s):  
Stellar Population ◽  
Thin Disk ◽  
Thick Disk ◽  
The Other ◽  
Chemical Characteristics ◽  
Fundamental Parameters ◽  
Halo Stars ◽  
Synthetic Spectra ◽  
The Galaxy ◽  
Comparison Stars

The aim of our stellar population study is to investigate the kinematical and chemical characteristics of the thin disk, thick disk and halo of the Galaxy. We have selected 51 stars in 2 astrometric and photometric surveys at l = 42°, b = +79° (Soubiran 1992) and l = 167°, b = +47° (Ojha et al. 1994), on the basis of the Reduced Proper Motion Diagram. They were observed with the 193cm telescope at Observatoire de Haute-Provence, with the CARELEC spectrograph (dispersion of 66Å/mm, FWHM of 3.0Å, range λλ4600 – 5500Å), together with 43 comparison stars with known fundamental parameters. The derivation of Teff, logg and [Fe/H] was done differentially using a grid of synthetic spectra and the comparison stars, as described in Cayrel et al. (1991). Twenty of the target stars were found to be more deficient than −0.5. In the (V, [Fe/H]) distribution, the halo stars are clearly separated from the other stars with a mean of (V, [Fe/H]) ≃ (−210km/s, – 1.4dex). Because of the small size of the sample, it was not possible to discriminate the thick disk from the thin disk. We have taken 200 more spectra, and with these new observations, we hope to be able to deconvolve the 3 populations in the (U, V, W, [Fe/H]) space as we did previously with the (U, V) velocity (Soubiran 1993).

scholarly journals The Bulge-disc connection in the Milky Way

2008 ◽  
Vol 4 (S254) ◽  
pp. 145-152
Author(s):  
James Binney
Keyword(s):  
Angular Momentum ◽  
Stellar Population ◽  
Milky Way ◽  
Dark Halo ◽  
Principal Characteristics ◽  
Corotation Radius ◽  
The Galaxy

AbstractBulges come in two flavours – classical and pseudo. The principal characteristics of each flavour are summarised and their impact on discs is considered. Classical bulges probably inhibit the formation of stellar discs. Pseudobulges exchange angular momentum with stars and gas in their companion discs, and also with its embedding dark halo. Since the structure of a pseudobulge depends critically on its angular momentum, these exchanges are expected to modify the bulge. The consequences of this modification are not yet satisfactorily understood. The Galaxy has a pseudobulge. I review the manifestations of its interaction with the disc. More work is needed on the dynamics of gas near the bulge's corotation radius, and on tracing the stellar population in the inner few hundred parsecs of the Galaxy.

The Dark Energy Survey: perspectives for resolved stellar population studies

2009 ◽  
Vol 5 (S262) ◽  
pp. 265-269
Author(s):  
Basílio Santiago ◽  
Brian Yanny
Keyword(s):  
Dark Energy ◽  
Stellar Population ◽  
Galactic Halo ◽  
Population Studies ◽  
Large Magellanic Cloud ◽  
Dark Energy Survey ◽  
The Galaxy ◽  
Photometric Measurements ◽  
Tidal Tails ◽  
Energy Survey

AbstractThe Dark Energy Survey (DES) will cover 5000 sq. deg. in grizY filters. Although its main goals are related to cosmology, it will yield photometric measurements of over 108 stars, most of them belonging to the Galaxy. DES will increase the sampling depth of very low-luminosity stellar and sub-stellar species, such as white, red, and brown dwarfs, by a factor of several as compared to SDSS. The structure of the Galactic halo, including its complex sub-structures caused by accretion remnants and globular cluster tidal tails, will also be probed and analyzed. DES will also allow comparison of star counts between Northern and Southern Galactic hemispheres to unprecedented detail. Finally, a significant sample of stars in the outskirts of the Large Magellanic Cloud (LMC) will be studied, providing new light into the debate about the existence of an LMC spheroidal component. These, among other important research goals attainable with the DES stellar data, are discussed in this contribution.

An H II region beyond the optical disk of the galaxy

1993 ◽  
Vol 413 ◽  
pp. L97 ◽  
Author(s):  
E. J. de Geus ◽  
S. N. Vogel ◽  
S. W. Digel ◽  
R. A. Gruendl
Keyword(s):  
Optical Disk ◽  
The Galaxy ◽  
H Ii Region

Stellar Population Models of Distant Radio Galaxies

1996 ◽  
Vol 175 ◽  
pp. 588-590
Author(s):  
D. Villani ◽  
S. Di Serego Alighieri
Keyword(s):  
Energy Distribution ◽  
Galaxy Formation ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Stellar Populations ◽  
Radio Galaxies ◽  
Initial Mass Function ◽  
Spectral Energy ◽  
The Galaxy

Stellar populations of high redshift radio galaxies (HzRG) (z up to 4.2) are the oldest stellar systems known, that is the ones formed at the earliest cosmological epochs. Therefore they are the best objects for providing us with information about the epoch of galaxy formation. The information on the stellar populations in HzRG are obtained from the study of their Integrated Spectral Energy Distribution (ISED) which are gathered both from spectra and integrated magnitudes. The most common approach for the interpretation of colors and spectral features of the energy distribution of galaxies is the Evolutionary Population Synthesis (EPS), which has been introduced for the first time by Tinsley in 1972. EPS models have often been used in the past to interpret the ISED of HzRG (Chambers & Charlot 1990; Lilly & Longair 1984; di Serego Alighieri et al. 1994) in order to draw conclusions on the age of the stellar populations and therefore on the epoch of galaxy formation. The results are sometimes conflicting and a number of very recent EPS models have become available (Bressan et al. 1995; Bruzual & Charlot 1993; Buzzoni 1989; Guiderdoni & Rocca-Volmerange 1987): we are therefore analysing the differences between the various EPS models with the aim of assessing their suitability to study the stellar population at early epochs. The EPS models assume for stars a given Initial Mass Function(IMF) as well as a Star Formation Rate (SFR). Then one can compute the number of stars with given mass present in the galaxy as a function of time. The position of each star in the HR diagram is determined by means of the isochrones, which are calculated from stellar evolutionary models. The ISED of a galaxy is obtained from the superposition of the spectra of single stars obtained from a stellar spectral library. Thus these models describe the galaxy ISED as a function of the time, giving a complete evolutionary picture.

Sign in / Sign up

Export Citation Format

Share Document