scholarly journals The age, metallicity and  -element abundance of Galactic globular clusters from single stellar population models

2007 ◽  
Vol 379 (4) ◽  
pp. 1618-1636 ◽  
Author(s):  
J. T. Mendel ◽  
R. N. Proctor ◽  
D. A. Forbes
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Population Models ◽  
Element Abundance ◽  
Galactic Globular Clusters

scholarly journals Near-infrared integrated spectra of Galactic globular clusters: testing simple stellar population models

2010 ◽  
Vol 410 (4) ◽  
pp. 2714-2724 ◽  
Author(s):  
R. Riffel ◽  
D. Ruschel-Dutra ◽  
M. G. Pastoriza ◽  
A. Rodríguez-Ardila ◽  
J. F. C. Santos Jr ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Near Infrared ◽  
Population Models ◽  
Galactic Globular Clusters

scholarly journals The WAGGS project-III. Discrepant mass-to-light ratios of Galactic globular clusters at high metallicity

2020 ◽  
Vol 492 (3) ◽  
pp. 3859-3871 ◽  
Author(s):  
H Dalgleish ◽  
S Kamann ◽  
C Usher ◽  
H Baumgardt ◽  
N Bastian ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Milky Way ◽  
Population Models ◽  
Theoretical Predictions ◽  
Field Unit ◽  
Stellar Masses ◽  
Kinematic Information ◽  
High Metallicity ◽  
Integral Field

ABSTRACT Observed mass-to-light ratios (M/L) of metal-rich globular clusters (GCs) disagree with theoretical predictions. This discrepancy is of fundamental importance since stellar population models provide the stellar masses that underpin most of extragalactic astronomy, near and far. We have derived radial velocities for 1622 stars located in the centres of 59 Milky Way GCs – 12 of which have no previous kinematic information – using integral-field unit data from the WAGGS project. Using N-body models, we determine dynamical masses and M/LV for the studied clusters. Our sample includes NGC 6528 and NGC 6553, which extend the metallicity range of GCs with measured M/L up to [Fe/H] ∼ −0.1 dex. We find that metal-rich clusters have M/LV more than two times lower than what is predicted by simple stellar population models. This confirms that the discrepant M/L–[Fe/H] relation remains a serious concern. We explore how our findings relate to previous observations, and the potential causes for the divergence, which we conclude is most likely due to dynamical effects.

scholarly journals The multipopulation phenomenon in Galactic globular clusters: M4 and M22

2009 ◽  
Vol 5 (S266) ◽  
pp. 326-332
Author(s):  
S. Villanova ◽  
G. Piotto ◽  
A. F. Marino ◽  
A. P. Milone ◽  
A. Bellini ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectroscopic Data ◽  
Globular Clusters ◽  
Stellar Population ◽  
The Other ◽  
Wide Field ◽  
Galactic Globular Clusters ◽  
Red Giant ◽  
Process Elements ◽  
Different Characteristics

AbstractWe present an abundance analysis based on high-resolution spectra of red-giant-branch (RGB) stars in the Galactic globular clusters NGC 6121 (M4) and NGC 6656 (M22). Our aim was to study their stellar population in the context of the multipopulation phenomenon recently discovered to affect some globular clusters. Analysis was performed for the following elements: O, Na, Mg, Al, Ca, Fe, Y, and Ba. Spectroscopic data were completed by high-precision wide-field U BV IC ground-based photometry and HST/ACS observations. For M4, we find a well-defined Na–O anticorrelation composed of two distinct groups of stars with significantly different Na and O content. The two groups of Na-rich and Na-poor stars populate two different regions along the RGB. As regards M22, Na and O follow the well-known anticorrelation found in many other GCs. However, at odds with M4, it appears to be continuous without any hint of clumpiness. On the other hand, we identified two clearly separated groups of stars with significantly different abundances of the s-process elements Y, Zr and Ba. The relative numbers of the members of both groups are very similar to the ratio of the stars in the two subgiant branches of M22 recently found by Piotto (2009). The s-element-rich stars are also richer in iron and have higher Ca abundances. This makes M22 the second cluster after ω Centauri where an intrinsic spread in Fe was found. Both spectroscopic and photometric results imply the presence of two stellar populations in M4 and M22, even if both clusters have completely different characteristics.

scholarly journals Stellar Population Models with Variable Element Abundance Ratios

2005 ◽  
Vol 13 ◽  
pp. 189-190
Author(s):  
Daniel Thomas ◽  
Claudia Maraston ◽  
Ralf Bender
Keyword(s):  
Absorption Line ◽  
Wavelength Range ◽  
Stellar Population ◽  
Population Models ◽  
Element Abundance ◽  
Variable Element ◽  
New Generation ◽  
First Time

AbstractWe present a comprehensive set of new generation stellar population models of Lick absorption line indices, which for the first time include element abundance ratios different from solar. We computed the 21 Lick indices CN1, CN2, Ca4227, G4300, Fe4383, Ca4455, Fe4531, C24668, Hβ, Fe5015, Mg1, Mg2, Mgb, Fe5270, Fe5335, Fe5406, Fe5709, Fe5782, Na D, TiO1, and TiO2, in the wavelength range 4000 ≲ λ ≲ 6500 Å. Models are provided with: [α/Fe] = 0.0, 0.3, 0.5, [α/Ca] = -0.1, 0.0, 0.2, 0.5, and [α/N] = −0.5, 0.0; ages from 1 to 15 Gyr; total metallicities from 1/200 to 3.5 solar (-2.25 ≤ [Z/H] ≤ 0.67).

scholarly journals IntegratedJ- andH-band spectra of globular clusters in the LMC: implications for stellar population models and galaxy age dating

2012 ◽  
Vol 543 ◽  
pp. A75 ◽  
Author(s):  
M. Lyubenova ◽  
H. Kuntschner ◽  
M. Rejkuba ◽  
D. R. Silva ◽  
M. Kissler-Patig ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Population Models ◽  
Age Dating ◽  
Band Spectra

scholarly journals Stellar population models based on the SDSS-IV MaStar library of stellar spectra – I. Intermediate-age/old models

2020 ◽  
Vol 496 (3) ◽  
pp. 2962-2997 ◽  
Author(s):  
C Maraston ◽  
L Hill ◽  
D Thomas ◽  
R Yan ◽  
Y Chen ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Globular Clusters ◽  
Stellar Population ◽  
Population Models ◽  
Full Account ◽  
Stellar Spectra ◽  
Novel Approach ◽  
Calibration Sets ◽  
Low Metallicity ◽  
Cold Metal

ABSTRACT We use the first release of the SDSS/MaStar stellar library comprising ∼9000, high S/N spectra, to calculate integrated spectra of stellar population models. The models extend over the wavelength range 0.36–1.03 µm and share the same spectral resolution ($R\sim 1800$) and flux calibration as the SDSS-IV/MaNGA galaxy data. The parameter space covered by the stellar spectra collected thus far allows the calculation of models with ages and chemical composition in the range $\rm {\mathit{ t}\gt 200 \,Myr, -2 \lt = [Z/H] \lt = + 0.35}$, which will be extended as MaStar proceeds. Notably, the models include spectra for dwarf main-sequence stars close to the core H-burning limit, as well as spectra for cold, metal-rich giants. Both stellar types are crucial for modelling λ > 0.7 µm absorption spectra. Moreover, a better parameter coverage at low metallicity allows the calculation of models as young as 500 Myr and the full account of the blue horizontal branch phase of old populations. We present models adopting two independent sets of stellar parameters (Teff, log g, [Z/H]). In a novel approach, their reliability is tested ‘on the fly’ using the stellar population models themselves. We perform tests with Milky Way and Magellanic Clouds globular clusters, finding that the new models recover their ages and metallicities remarkably well, with systematics as low as a few per cent for homogeneous calibration sets. We also fit a MaNGA galaxy spectrum, finding residuals of the order of a few per cent comparable to the state-of-art models, but now over a wider wavelength range.

scholarly journals Ultra-Compact Dwarf Galaxies – More Massive than Allowed?

2007 ◽  
Vol 3 (S246) ◽  
pp. 427-428 ◽  
Author(s):  
Michael Hilker ◽  
S. Mieske ◽  
H. Baumgardt ◽  
J. Dabringhausen
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Dwarf Galaxies ◽  
Population Models ◽  
High Mass ◽  
Early Type ◽  
Dynamical Mass ◽  
Dispersion Diagram

AbstractDynamical mass estimates of ultra-compact dwarfs galaxies and massive globular clusters in the Fornax and Virgo clusters and around the giant elliptical Cen A have revealed some surprising results: 1) above ~106M⊙ the mass-to-light (M/L) ratio increases with the objects' mass; 2) some UCDs/massive GCs show high M/L values (4 to 6) that are not compatible with standard stellar population models; and 3) in the luminosity-velocity dispersion diagram, UCDs deviate from the well-defined relation of “normal” GCs, being more in line with the Faber-Jackson relation of early-type galaxies. In this contribution, we present the observational evidences for high mass-to-light ratios of UCDs and discuss possible explanations for them.

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