STELLAR POPULATIONS IN ELLIPTICAL GALAXIES

2011 ◽  
Vol 20 (10) ◽  
pp. 1901-1906
Author(s):  
LUCIO ANGELETTI ◽  
PIETRO GIANNONE
Keyword(s):  
Spectral Index ◽  
Surface Brightness ◽  
Elliptical Galaxies ◽  
Dynamical Structure ◽  
Spatial Distributions ◽  
Population Synthesis ◽  
Full Sample ◽  
Radial Profiles ◽  
Accretion Model ◽  
Metal Abundances

The R1/n law for the radial surface brightness of elliptical galaxies and the "Best Accretion Model" together with the "Concentration Model" have been combined in order to determine the mass and dynamical structure of largely-populated star systems. Families of models depending on four parameters have been used to fit the observed surface radial profiles of some spectro-photometric indices of a sample of eleven galaxies. We present the best agreements of the spectral index Mg2 with observations for three selected galaxies representative of the full sample. For them we have also computed the spatial distributions of the metal abundances, which are essential to achieve a population synthesis.

scholarly journals Diffuse LINER-type emission from extended disc regions of barred galaxies

2020 ◽  
Vol 496 (1) ◽  
pp. 36-48 ◽  
Author(s):  
S M Percival ◽  
P A James
Keyword(s):  
Line Emission ◽  
Elliptical Galaxies ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Population Synthesis ◽  
Full Sample ◽  
Barred Galaxies ◽  
Horizontal Branch Stars ◽  
Ambient Gas ◽  
Barred Spiral Galaxies

ABSTRACT We present a spectroscopic analysis of the central disc regions of barred spiral galaxies, concentrating on the region that is swept by the bar but not including the bar itself (the ‘star formation desert’ or SFD region). New spectroscopy is presented for 34 galaxies, and the full sample analysed comprises 48 SBa–SBcd galaxies. These data confirm the full suppression of SF within the SFD regions of all but the latest type (SBcd) galaxies. However, diffuse [N ii] and H α line emission is detected in all galaxies. The ubiquity and homogeneous properties of this emission from SBa to SBc galaxies favour post-asymptotic giant branch (p-AGB) stars as the source of this line excitation, rather than extreme blue horizontal branch stars. The emission-line ratios strongly exclude any contribution from recent SF, but are fully consistent with recent population synthesis modelling of p-AGB emission by other authors, and favour excitation dominated by ambient gas of approximately solar abundance, rather than ejecta from the AGB stars themselves. The line equivalent widths are also larger than those observed in many fully passive (e.g. elliptical) galaxies, which may also be a consequence of a greater ambient gas density in the SFD regions.

scholarly journals Surface brightness fluctuation distances for nearby dwarf elliptical galaxies

2001 ◽  
Vol 380 (1) ◽  
pp. 90-101 ◽  
Author(s):  
H. Jerjen ◽  
R. Rekola ◽  
L. Takalo ◽  
M. Coleman ◽  
M. Valtonen
Keyword(s):  
Surface Brightness ◽  
Elliptical Galaxies ◽  
Brightness Fluctuation ◽  
Dwarf Elliptical Galaxies

scholarly journals Kinematic Modelling of NGC 3379

1983 ◽  
Vol 100 ◽  
pp. 295-296
Author(s):  
Gary A. Mamon
Keyword(s):  
Surface Brightness ◽  
Elliptical Galaxies ◽  
Anisotropic Pressure ◽  
Velocity Anisotropy ◽  
Kinematic Modelling

Giant elliptical galaxies are now known to be supported by anisotropic pressure rather than by rotation (cf. Binney, 1981). This anisotropy can be derived from observable quantities for spherical systems as was shown by Binney and Mamon (1982) in their study of M87. We investigate here the velocity anisotropy of the El galaxy NGC 3379, a giant elliptical whose surface brightness constitutes an excellent illustration of the r1/4 law.

scholarly journals The Shapes and Ages of Elliptical Galaxies

1996 ◽  
Vol 171 ◽  
pp. 359-359
Author(s):  
Roelof S. de Jong ◽  
Roger L. Davies
Keyword(s):  
Elliptical Galaxies ◽  
Population Synthesis ◽  
Range Of Values ◽  
Normal Perception

Normally elliptical galaxies are thought to be old, evolved systems, but recently a controversy has arisen over the age of ellipticals. Measurements by Gonzáles (1993, Ph.D. thesis, UCSC) show that the Hβ absorption indices of ellipticals span a range of values. Population synthesis models indicate that the Hβ index is a good age indicator and hence, contrary to normal perception, the ages of ellipticals seem to span a range of values.

scholarly journals The Age Spread Among Galaxies and the Origin of the UV Radiation from Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 448-449
Author(s):  
Young-Wook Lee ◽  
Jang-Hyun Park
Keyword(s):  
Uv Radiation ◽  
Spectral Energy Distribution ◽  
Type Systems ◽  
Elliptical Galaxies ◽  
Spectral Energy ◽  
Population Synthesis ◽  
Massive Galaxies ◽  
Metal Abundance ◽  
Inside Out ◽  
Uv Upturn

Recent UV observations of elliptical galaxies are interpreted as evidence for the global second parameter phenomenon of horizontal-branch (HB) morphology within, as well as between, these galaxies. In this picture, the origin of the UV radiation is mostly due to hot HB stars and their post-HB progeny produced by the metal-poor tail of the wide metallicity distribution expected to be present in these systems. The attractive feature of this model is that the bimodal temperature distributions of HB stars (and their progeny), required to generate the 2000 Å dip of the spectral energy distribution (SED), can naturally be reproduced from the standard HB population models with large range of metal abundance (see Lee 1994, ApJ, 430, L113). Detailed population synthesis models are presented, which reproduce the systematic variation of UV upturn among elliptical galaxies (Fig 1). If age is the major second parameter, as suggested by the fossil record in our Galaxy, the observed UV color gradient and the UV upturn-total mass (mean metallicity) correlation, within and between the early-type systems, would imply, respectively, (1) that most galaxies formed from the inside out, and (2) that there is age spread among galaxies, in the sense that more massive galaxies are older (and more metal-rich in the mean) than less massive galaxies as a result of more efficient star formation (and metal enrichment) in denser environments.

scholarly journals Dark Matter Dogma: A Study of 214 Galaxies

Galaxies ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 36 ◽  
Author(s):  
Alan Sipols ◽  
Alex Pavlovich
Keyword(s):  
Dark Matter ◽  
Surface Brightness ◽  
Parametric Models ◽  
Galactic Rotation ◽  
Total Density ◽  
Apparent Difference ◽  
Rotation Curves ◽  
Disk Model ◽  
Radial Profiles ◽  
Baryonic Dark Matter

The aim of this paper is to test the need for non-baryonic dark matter in the context of galactic rotation and the apparent difference between distributions of galactic mass and luminosity. We present a set of rotation curves and 3.6 μm surface brightness profiles for a diverse sample of 214 galaxies. Using rotation curves as the sole input into our Newtonian disk model, we compute non-parametric radial profiles of surface mass density. All profiles exhibit lower density than parametric models with dark halos and provide a superior fit with observed rotation curves. Assuming all dynamical mass is in main-sequence stars, we estimate radial distributions of characteristic star mass implied by the corresponding pairs of density and brightness profiles. We find that for 132 galaxies or 62% of the sample, the relation between density and brightness can be fully explained by a radially declining stellar mass gradient. Such idealized stellar population fitting can also largely address density and brightness distributions of the remaining 82 galaxies, but their periphery shows, on average, 14 M⊙/pc2 difference between total density and light-constrained stellar density. We discuss how this density gap can be interpreted, by considering a low-luminosity baryonic matter, observational uncertainties, and visibility cutoffs for red dwarf populations. Lastly, we report tight correlation between radial density and brightness trends, and the discovered flattening of surface brightness profiles—both being evidence against dark matter. Our findings make non-baryonic dark matter unnecessary in the context of galactic rotation.

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