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Topic: Stellar population

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	Stellar - Wikipedia, the free encyclopedia
		Stellar aberration is an astronomical phenomenon defined as an apparent motion of the heavenly bodies due to a combination of the motion of the Earth and the finite velocity of light.
		Stellar astronomy is the study of stars and the phenomena exhibited by the various forms/developmental stages of stars.
		Stellar evolution is the sequence of changes that a star undergoes during its lifetime, the millions or billions of years during which it emits light and heat.
	en.wikipedia.org /wiki/Stellar (537 words)

	Stellar population - Wikipedia, the free encyclopedia
		Population II stars are the first long-lived stars to have formed after the Big Bang, and therefore have low metal abundance.
		Population II stars are found in globular clusters and in the Galactic Halo of the Milky Way (as CS22892-052, CS31082-001, HE0107-5240, HE1327-2326).
		Population II stars are much older than Population I stars, contrary to what one might expect from the numbers assigned to them.
	en.wikipedia.org /wiki/Stellar_population (383 words)

	stellar populations - HighBeam Encyclopedia (Site not responding. Last check: 2007-10-02)
		Population II stars are formed early in the history of the galaxy from pure hydrogen with an admixture of primordial helium.
		Population I stars, of which the sun is typical, are young stars that still lie mostly on the main sequence of the Hertzsprung-Russell diagram.
		Population II stars are found both in the spiral arms and in the gas-free and dust-free regions of the spiral galaxies, i.e., the nucleus and the halo of high-velocity stars and globular clusters that surround the disk of the galaxy.
	www.encyclopedia.com /html/s1/stellarp.asp (473 words)

	The Role Of Stellar Population Types In The Discussion Of Stellar Evolution
		This suggests that the sun is a population I star, and that population I stars orbit the galactic center in roughly circular orbits confined to the galactic plane.
		Population I stars have an H-R diagram similar to those for open star clusters, while the H-R diagram of population II stars resembles that of globular clusters.
		Open star clusters have high metal abundances and are found near the galactic plane, and so are recognized as population I. Population I stars generally have clouds of dust and gas around and near them, while population II stars generally are found in dust free and gas free environments.
	www.creationresearch.org /crsq/articles/30/30_1/StellarPop.html (3401 words)

	MPE : OPINAS
		The alternative approach is the detailed investigation of the stellar populations in local galaxies, which has been pioneered by analyzing slopes and scatter of color-magnitude and scaling relations of early-type galaxies, followed by a number of detailed studies of absorption line indices.
		The main challenge in the archaeology of stellar population is the disentanglement of age and metallicity effects.
		The principal aim is to constrain the formation epochs of the stellar populations in early-type galaxies as a function of their type (elliptical and lenticular), mass and environmental density.
	www.mpe.mpg.de /opinas/research/5.3_elliptical_galaxies (518 words)

	Introduction
		Stellar population synthesis aims at discerning the stellar mix in galaxies from their integrated spectral energy distributions.
		This is the fourth paper of a series dedicated to the study of stellar populations in the optical, with emphasis in the blue spectral region.
		One of the chief applications of stellar population synthesis is the estimate of mean elemental abundances of stars in remote systems from the absorption line indices in their integrated spectra.
	www.astro.virginia.edu /~rps7v/Models/ms/node1.html (1901 words)

	A Brief Stellar History (Site not responding. Last check: 2007-10-02)
		This is a concordant result for the age of both the main stellar Populations on the Vc model.
		As may be inferred from the foregoing discussion, the Vc model accepts the usual mechanism for the ageing of the stars, and the consequent appearance of the various stars is explicable in terms of known processes.
		They reveal that stellar characteristics can generally be accounted for, including the vast, cool, extended atmospheres of the red giant stars, or the more compact internal structure of stars like our sun.
	www.setterfield.org /stellarhist.html (11360 words)

	Stellar Populations
		Stellar populations are not discrete in their properties, but rather have a continuum of characteristics that reflect the changes in star formation with time.
		There are basically three stellar populations in our Galaxy, corresponding to the three distinct dynamical components to the Galaxy; the disk population, the bulge population and the halo population.
		The bulge population is restricted to the rounded, central region of the Galaxy, also rotating.
	zebu.uoregon.edu /~js/ast122/lectures/lec26.html (1192 words)

	Unit 6
		Describe stellar populations in the Milky Way Galaxy, and the properties of population I and population II stars, including their chemical composition.
		Stellar diameters can be determined using interferometry, a technique which measures incoming radiation from two locations and then combines the two signals.
		Stellar diameters can be determined using speckle interferometry, a technique which uses high speed imaging to overcome the blurring effect of the earth's atmosphere.
	www.phyast.pitt.edu /~hamilton/astro89/unit06.htm (1678 words)

	Stellar Populations issues (Site not responding. Last check: 2007-10-02)
		The difficulty of using SBF as stellar population tracers, is the need of an independent estimation of the galaxy distance, if multi-band SBF measurements (that is SBF colours) are not available.
		According to this view, and considering the predictions that the monolithic era of galaxies should be marked by the presence steeper gradients for higher mass galaxies, it seems that SBF gradients have memory of such original state of the galaxy, which could not be detected in the ordinary colour gradients.
		In particular, the location of NGC1407 is consistent with an old stellar population of nearly constant age (t ≈ 15 Gyr), but with a significant increase of metal content in the innermost regions.
	www.te.astro.it /osservatorio/personale/cantiello/Tesi/Chap4/Tables/stellarpop.htm (2785 words)

	Planet Quest: SIM Technical Area
		A complete census of the stellar population of the Galaxy will be made by SIM including both ordinary stars and "dark" stars.
		Ordinary stars, burning their nuclear fuel and shining, can perhaps best be studied with traditional astronomical techniques, but dark stars, by which we include old brown dwarfs, fl holes, old white dwarfs, neutron stars, and perhaps exotic objects such as mirror matter stars or primordial fl holes, can only be studied by their gravitational effects.
		The only way to examine the field population of these dark stars is through microlensing, the deflection of light from a visible star in the background by an object (dark or not) in the foreground.
	planetquest.jpl.nasa.gov /SIM/sim_stellar_astro.cfm (1034 words)

	A Comprehensive Library of Near-Infrared Stellar Spectra (Site not responding. Last check: 2007-10-02)
		Knowledge of the stellar population provides insight into the last epoch of major star formation in the galaxy, giving the age of the dominant stellar population that is present.
		Using a linear optimization technique, these template stellar spectra can then be used to synthesize a galaxy spectrum, giving the combination of stellar types which provide a best-fit to the integrated light from the galaxy.
		This process is known as stellar population synthesis, and provides information regarding the most probable stellar population present in the galaxy.
	www.tsgc.utexas.edu /meetings/2002_spr/jackie_dunn.html (262 words)

	2 Stellar mass-loss and long-term galactic evolution
		2.2 Cumulative mass-loss of a coeval stellar population
		Necessary ingredients to construct an approximate mass-loss curve of a CSP thus reduce to the knowledge of IMF, stellar initial-final mass relation and stellar lifetime-mass relation (in the case of LMS, two lifetimes are necessary, for the ends of the RGB and AGB phases).
		The stellar metallicity does not change the mass-loss of the whole CSP too much despite the fact that individual stars have their lifetimes and final masses influenced by Z quite noticeably (see Figs.
	aanda.u-strasbg.fr:2002 /papers/aa/full/2001/34/aa1504/node2.html (1076 words)

	Digital Demo Room - Stellar Structure and Evolution Tutorial
		The number of higher mass stars in a given stellar population allowed by this IMF is much smaller than number of lower mass stars.
		The result is that for star clusters and stellar populations which this IMF models, there should be many more low mass stars than high mass stars, and such is the case observationally.
		Essentially, what we did was to generate a random mass, check its probability of existing in a stellar population with the normalized IMF, and then either reject it or keep it depending on this probability.
	rainman.astro.uiuc.edu /ddr/stellar/code.html (1785 words)

	3 Stellar population
		In order to study the stellar population content of nuclear regions of galaxies, we applied the stellar population analysis by B88, which is based on spectral group templates built from star clusters of different ages and metallicities, and nuclear galaxy spectral templates.
		For galaxies with spectra in two different slits, we quoted in Table 3 the average values of the equivalent widths in both slits along with the standard deviation of the average.
		Figure 3 shows the synthesized population for the galaxies NGC5757 and NGC6851, that have the bluest and reddest stellar populations respectively.
	aanda.u-strasbg.fr:2002 /papers/aa/full/2001/34/aa1190/node3.html (1265 words)

	On the Stellar Population and Star-Forming History of the Orion Nebula Cluster (Site not responding. Last check: 2007-10-02)
		We report on the first phase of a study of the stellar population comprising the Orion Nebula Cluster (ONC).
		Comparison of the derived HR diagram with traditional pre-main sequence evolutionary calculations shows a trend of increasing stellar age with increasing stellar mass.
		In particular, although there are structural differences between the detailed ONC mass spectrum and various models constructed from solar neighborhood data, the observed mass spectrum appears to a peak at ~0.2 M_sun and to fall off rapidly towards lower masses; several substellar objects are present.
	www.astro.caltech.edu /~lah/papers/orion.abstract.html (407 words)

	Origins: Library: Story of the Universe
		The bulge population of M31 is usually considered to be an "old" population, with an age of 10-15 billion years.
		One key method in estimating the age of the population is to measure the luminosity of its brightest stars.
		The stellar density is so high in these cores that, even when observed with HST, what appears to be a single bright star is in fact the superposition of many fainter ones.
	origins.jpl.nasa.gov /library/story/011200-b_old.html (851 words)

	Laboratoire Astrophysique de Toulouse - Tarbes (UMR5572) - STELIB : a library of stellar spectra for population ...
		The objective of our Stellar Library is to build an homogeneous library of stellar spectra in the visible range (3200 to 9500A), including stars of all spectral types, luminosity classes and metallicity that can be observed from the ground with the current instrumentation.
		One of the weakest points in using theoretical model atmospheres is the fact that the spectra for the coolest stars in some of the most relevant regions in the HR diagram (giants) are not contained in Kurucz atlas.
		The main objective of our Stellar Library is to build a homogeneous library of stellar spectra in the visible range (3200 to 9500A), including stars of all spectral types and luminosity classes that can be observed from the ground with the current instrumentation.
	www.ast.obs-mip.fr /article181.html (477 words)

	Populations & Components of the Milky Way
		The idea of stellar populations, each characterized by a distinct spatial distribution, kinematics, and metal content, proved to be a key concept in interpreting observations of our own galaxy.
		The existence of an intermediate population was explicitly recognized at the Vatican Symposium.
		The true nature of this stellar population is not completely clear; although it was originally classified as Pop.
	www.ifa.hawaii.edu /~barnes/ast626_95/pcmw.html (1111 words)

	Rosa M. Gonzalez Delgado: Research.
		For intermediate and old stellar populations, our results, once degraded to a lower resolution, are similar to the ones obtained by other groups apart from limitations imposed by the stellar evolutionary physics.
		Stellar libraries are one of the basic ingredients of evolutionary population synthesis models.
		It predicts the synthetic spectrum of a stellar population as a function of age, SFR, and IMF.
	www.iaa.es /~rosa/research.html (1309 words)

	Stellar Structure & Evolution
		This is a project to reduce numerical and technical uncertainties in stellar models, and to ensure that model differences are due to variations in the physics employed to calculate them.
		At the Leiden Lorentz Center meeting "Fine-tuning Stellar Population Models" (June 2006) a challenge for the stellar model community was defined with the same intention.
		Results are to be presented at IAU symposium 241 "Stellar Populations as Building Blocks of Galaxies" in December 2006.
	www.mpa-garching.mpg.de /stars/index.shtml (542 words)

	Stellar Population content in the Local Group Galaxies and beyond
		It is worth noting that even though some investigations have been recently devoted to the Color-Magnitude diagram of stellar systems in the quoted clusters, up to now we lack a detailed analysis of the evolutionary properties (age, chemical composition, spatial distribution) of field stars in the halo and/or in the bulge of these galaxies.
		A detailed map of all the stellar populations in nearby galaxies is of great importance for the population synthesis analysis, etc.
		The C-M diagram of large extragalactic stellar fields together with the kinematic properties can cast new light on several astrophysical problems concerning the chemical evolution, the star formation and the metallicity gradients in galaxies which experienced a different dynamical evolutions and environment effects when compared to our Galaxy.
	www.mporzio.astro.it /WFI-LBT/biocamlbt/node54.html (425 words)

	Stellar population and kinematic properties of ULIRGs and Seyfert galaxies
		Stellar population and kinematic properties of ULIRGs and Seyfert galaxies
		The correlations between the kinematic properties and the stellar populations will be explored.
		The new data are well-suited to constrain the stellar population in the circumnuclear region, because the AO will minimize the contribution of the nuclear point-source.
	www.eso.org /science/vltsv/sinfonisv/agnulirg.html (651 words)

	Astrophysics Research Institute - Liverpool John Moores University (Site not responding. Last check: 2007-10-02)
		This is interpreted as evidence for an intermediate age stellar population in the field galaxies, indicative of a more extended or recent epoch of star formation.
		A study of the former enabled the strongest limits to date to be put on possible stellar candidates for the halo dark matter in disk galaxies, and for the first time conclusively ruled out low-mass main-sequence stars as the sole constituent of massive haloes.
		In a minor merger a pre-existing elliptical galaxy accretes a much smaller galaxy, either a low-mass spiral or a dwarf elliptical, and the shells are formed from the stars of the accreted galaxy.
	www.astro.livjm.ac.uk /research/galaxies.shtml (1198 words)

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