scholarly journals Visual–IR Color Gradients in Elliptical Galaxies

1987 ◽  
Vol 127 ◽  
pp. 443-444
Author(s):  
R. F. Peletier ◽  
E. A. Valentijn ◽  
R. F. Jameson
Keyword(s):  
Population Model ◽  
Stellar Population ◽  
Main Sequence ◽  
Elliptical Galaxies ◽  
Strong Constraint ◽  
Average Temperature ◽  
Simultaneous Measurements ◽  
Continuity Of Solutions ◽  
Different Populations ◽  
Color Gradients

Dissipational formation theories (e.g. Larson 1974) predict a metallicity change with distance from the center in elliptical galaxies. Several authors have reported small color gradients in visual colors like B–V and B–R. The interpretation of these data is not easy, due to uncertainties caused by the short wavelength–baseline, and by the presence of a hot stellar population suggested by IUE–data (e.g. Burstein et al. 1986). Simultaneous measurements of visual and visual-infrared colors provide the means to determine both the average temperature of the giant branch and the turnoff–temperature of the main sequence. This allows to model fractional contributions of different populations, including age– and metallicity–effects. The required continuity of solutions at different radii provides a strong constraint in selecting a more unique overall population model, and relieves the ambiguous interpretation of single measurements.

scholarly journals Near-IR Imaging of Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 443-443 ◽  
Author(s):  
M.A. Pahre ◽  
S. Djorgovski ◽  
K. Matthews ◽  
D. Shupe ◽  
R. De Carvalho ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Stellar Population ◽  
Elliptical Galaxies ◽  
Virgo Cluster ◽  
Fundamental Plane ◽  
Near Ir ◽  
Surface Brightness Fluctuations ◽  
Distance Indicator ◽  
Color Gradients ◽  
Optical Color

We have imaged more than thirty early-type galaxies in the K-band to investigate their stellar populations. Our surface brightness fluctuations (SBF) measurements for the nearest 14 galaxies produce a mean fluctuations magnitude in the K-band of The scatter in the Virgo cluster is small at 0.18 mag, which implies that infrared SBF is potentially a good distance indicator (Pahre & Mould 1994). Inspection of the simple stellar population tracks of Worthey (1994) suggests that a plot of the fluctuation color against broadband color (V – I) might be useful in discriminating between age and metallicity effects in elliptical galaxies. We have measured (r – K) color gradients for the entire sample utilizing three methods, two of them independent of sky-subtraction errors, as found in Sparks & Jørgensen (1993). Our color gradients are consistent with a mean metallicity gradient of 0.14 mag dex−1, which is somewhat smaller than that implied by optical color and line gradients alone, suggesting that age gradients may also be important. Finally, we have constructed an infrared Fundamental Plane (FP) which is consistent with its optical counterpart; continued work will determine if there is a significant change in the tilt of the FP between the optical and infrared.

scholarly journals The Stellar Content of the Nuclei of Spiral Galaxies

1983 ◽  
Vol 6 ◽  
pp. 157-163
Author(s):  
D. Crampton ◽  
R.D. McClure ◽  
A.P. Cowley
Keyword(s):  
Spectral Type ◽  
Stellar Population ◽  
Main Sequence ◽  
Spiral Galaxies ◽  
Elliptical Galaxies ◽  
Solar Neighbourhood ◽  
Stellar Content ◽  
Late Type ◽  
Metal Abundances ◽  
Hydrogen Lines

Numerous studies have been attempted to determine the stellar content of the nuclei of galaxies. In the case of elliptical galaxies observations show that there is a change in spectral type from later to earlier types correlated with a variation from high to low luminosity (e.g. Faber 1977). This has been interpreted for the most part as being due to differences in metal abundances in an old stellar population, although some recent studies suggest a variation in stellar age may be important as well (e.g. O’Connell 1980, Heckman 1980). The nuclear bulges of spiral galaxies also display a change from late to early spectral type along a sequence from high to low luminosity bulges. In this case, however, the assumption has almost universally been made that these differences are due to differences in age of the stellar population. In particular, most stellar models for the nuclear bulges of spiral galaxies have used solar neighbourhood metal- rich stars, and assumed that the strong hydrogen lines and weak metal lines in late-type spiral nuclei are due to the predominance of a very young main-sequence population rather than old metal-poor stars.

scholarly journals Dust VS. Color Gradients in Elliptical Galaxies

1996 ◽  
Vol 171 ◽  
pp. 383-383
Author(s):  
Paul Goudfrooij
Keyword(s):  
Multiple Scattering ◽  
Stellar Population ◽  
Elliptical Galaxies ◽  
Scattering Model ◽  
Poster Paper ◽  
Dust Component ◽  
Color Gradients

Color gradients in elliptical galaxies are commonly interpreted as being due to stellar population gradients (e.g., Davies et al. 1993, MNRAS 262, 650). Here, I show that elliptical galaxies should generally contain a diffusely distributed component of dust, in addition to the “visible” component which is in the form of dust lanes or patches (see Fig. 1a). Employing a multiple scattering model for the dust, the presence of this newly postulated dust component is found to imply significant radial color gradients (see Fig. 1b). This should be taken seriously in the interpretation of color gradients in elliptical galaxies. This poster paper is based upon a (much!) more elaborate article by Goudfrooij & de Jong (1995, A&A 298, 784).

scholarly journals Galaxy properties as revealed by MaNGA – III. Kinematic profiles and stellar population gradients in S0s

2020 ◽  
Vol 495 (3) ◽  
pp. 2894-2908 ◽  
Author(s):  
H Domínguez Sánchez ◽  
M Bernardi ◽  
F Nikakhtar ◽  
B Margalef-Bentabol ◽  
R K Sheth
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Signal To Noise Ratio ◽  
Elliptical Galaxies ◽  
Element Abundance ◽  
High Signal ◽  
Galactocentric Distance ◽  
Massive Galaxies ◽  
Nearby Galaxies ◽  
Mass Functions

ABSTRACT This is the third paper of a series where we study the stellar population gradients (SP; ages, metallicities, α-element abundance ratios, and stellar initial mass functions) of early-type galaxies (ETGs) at $z$ ≤ 0.08 from the Mapping Nearby Galaxies at APO Data Release 15 (MaNGA-DR15) survey. In this work, we focus on the S0 population and quantify how the SP varies across the population as well as with galactocentric distance. We do this by measuring Lick indices and comparing them to SP synthesis models. This requires spectra with high signal-to-noise ratio which we achieve by stacking in bins of luminosity (Lr) and central velocity dispersion (σ0). We find that: (1) there is a bimodality in the S0 population: S0s more massive than $3\times 10^{10}\, \mathrm{M}_\odot$ show stronger velocity dispersion and age gradients (age and σr decrease outwards) but little or no metallicity gradient, while the less massive ones present relatively flat age and velocity dispersion profiles, but a significant metallicity gradient (i.e. [M/H] decreases outwards). Above $2\times 10^{11}\, \mathrm{M}_\odot$, the number of S0s drops sharply. These two mass scales are also where global scaling relations of ETGs change slope. (2) S0s have steeper velocity dispersion profiles than fast-rotating elliptical galaxies (E-FRs) of the same luminosity and velocity dispersion. The kinematic profiles and SP gradients of E-FRs are both more similar to those of slow-rotating ellipticals (E-SRs) than to S0s, suggesting that E-FRs are not simply S0s viewed face-on. (3) At fixed σ0, more luminous S0s and E-FRs are younger, more metal rich and less α-enhanced. Evidently for these galaxies, the usual statement that ‘massive galaxies are older’ is not true if σ0 is held fixed.

scholarly journals AGN feedback in numerical simulations

2009 ◽  
Vol 5 (H15) ◽  
pp. 293-293
Author(s):  
Luca Ciotti
Keyword(s):  
Black Hole ◽  
Numerical Simulations ◽  
Stellar Population ◽  
Cosmic Time ◽  
Elliptical Galaxies ◽  
Stellar Mass ◽  
Feedback Effects ◽  
Supermassive Black Hole ◽  
Physically Based ◽  
Continuous Source

AbstractThe passively evolving stellar population in elliptical galaxies (Es) provides a continuous source of fuel for accretion on the central supermassive black hole (SMBH), which is 1) extended over the entire galaxy life (but declining with cosmic time), 2) linearly proportional to the stellar mass of the host spheroid, 3) summing up to a total gas mass that is > 100 times larger than the currently observed SMBH masses, 4) available independently of merging events. The main results of numerical simulations of Es with central SMBH, in which a physically based implementation of radiative and mechanical feedback effects is considered, are presented.

scholarly journals The X-ray stellar population of the LMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 20-29 ◽  
Author(s):  
Yaël Nazé
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Massive Stars ◽  
High Energy ◽  
Magellanic Clouds ◽  
X Rays ◽  
X Ray ◽  
Energy Domain ◽  
X Ray Binaries

AbstractIn the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC.

Further mid-infrared study of the rho Ophiuchi cloud young stellar population: Luminosities and masses of pre-main-sequence stars

1994 ◽  
Vol 434 ◽  
pp. 614 ◽  
Author(s):  
Thomas P. Greene ◽  
Bruce A. Wilking ◽  
Philippe Andre ◽  
Erick T. Young ◽  
Charles J. Lada
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Infrared Study ◽  
Mid Infrared ◽  
Rho Ophiuchi
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