Stellar Population Models and Individual Element Abundances. Ii. Stellar Spectra and Integrated Light Models

Lee, H.-c.; Worthey, Guy; Dotter, Aaron; Chaboyer, Brian; Jevremović, D.; Baron, E.; Briley, Michael M.; Ferguson, Jason W.; Coelho, P.; Trager, S. C.

doi:10.1088/0004-637x/694/2/902

Cited by 70 publications

(85 citation statements)

References 58 publications

(84 reference statements)

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“…Dotter et al 2007Dotter et al , 2008. Most SPS models that consider variable abundance patterns do not include the abundance effects on the isochrones (e.g., D. Thomas et al 2003Graves & Schiavon 2008), with the exception of the models of Coelho et al (2007) and Lee et al (2009). We emphasize that these models are the only ones currently available that follow the effect of individual elemental abundance variation on the full spectrum.…”

Section: Modelmentioning

confidence: 99%

“…We emphasize that these models are the only ones currently available that follow the effect of individual elemental abundance variation on the full spectrum. To our knowledge, all other models that include variation in individual elemental abundances do so only on the effect of spectral indices, principally the Lick index system (e.g., Thomas et al 2003;Schiavon et al 2005;Lee et al 2009). …”

Section: Modelmentioning

confidence: 99%

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The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. Ii. Results

Conroy

Dokkum

2012

ApJ

499

571

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The spectral absorption lines in early-type galaxies contain a wealth of information regarding the detailed abundance pattern, star formation history, and stellar initial mass function (IMF) of the underlying stellar population. Using our new population synthesis model that accounts for the effect of variable abundance ratios of 11 elements, we analyze very high quality absorption line spectra of 38 early-type galaxies and the nuclear bulge of M31. These data extend to 1 μm and they therefore include the IMF-sensitive spectral features Na i, Ca ii, and FeH at 0.82 μm, 0.86 μm, and 0.99 μm, respectively. The models fit the data well, with typical rms residuals 1%. Strong constraints on the IMF and therefore the stellar mass-to-light ratio, (M/L) stars , are derived for individual galaxies. We find that the IMF becomes increasingly bottom-heavy with increasing velocity dispersion and [Mg/Fe]. At the lowest dispersions and [Mg/Fe] values the derived IMF is consistent with the Milky Way (MW) IMF, while at the highest dispersions and [Mg/Fe] values the derived IMF contains more low-mass stars (is more bottom-heavy) than even a Salpeter IMF. Our best-fit (M/L) stars values do not exceed dynamically based M/L values. We also apply our models to stacked spectra of four metal-rich globular clusters in M31 and find an (M/L) stars that implies fewer low-mass stars than a MW IMF, again agreeing with dynamical constraints. We discuss other possible explanations for the observed trends and conclude that variation in the IMF is the simplest and most plausible.

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Section: Modelmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. Ii. Results

Conroy

Dokkum

2012

ApJ

499

571

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“…Brodie & Huchra 1990) to those which perform the simultaneous χ 2 -minimisation of a large number of spectral indices (see, e.g., Proctor et al 2004). Nevertheless, both photometric and spectroscopic methods are dependent on the accurate modelling of simple stellar populations (SSPs, see, Table 4 is available in electronic form at http://www.aanda.org e.g., Bruzual & Charlot 2003;Le Borgne et al 2004;Delgado et al 2005;Maraston 2005;Coelho et al 2007;Percival et al 2009;Lee et al 2009;Conroy & Gunn 2010;Vazdekis et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Full spectral fitting of Milky Way and M 31 globular clusters: ages and metallicities

Cezario

Coelho

Alves-Brito

et al. 2012

A&A

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Context. The formation and evolution of disk galaxies are long standing questions in astronomy. Understanding the properties of globular cluster systems can lead to important insights on the evolution of its host galaxy. Aims. We aim to obtain the stellar population parameters -age and metallicity -of a sample of M 31 and Galactic globular clusters. Studying their globular cluster systems is an important step towards understanding their formation and evolution in a complete way. Methods. Our analysis employs a modern pixel-to-pixel spectral fitting technique to fit observed integrated spectra to updated stellar population models. By comparing observations to models we obtain the ages and metallicities of their stellar populations. We apply this technique to a sample of 38 globular clusters in M 31 and to 41 Galactic globular clusters, used as a control sample. Results. Our sample of M 31 globular clusters spans ages from 150 Myr to the age of the Universe. Metallicities [Fe/H] range from -2.2 dex to the solar value. The age-metallicity relation obtained can be described as having two components: an old population with a flat age-[Fe/H] relation, possibly associated with the halo and/or bulge, and a second one with a roughly linear relation between age and metallicity, higher metallicities corresponding to younger ages, possibly associated with the M 31 disk. While we recover the very well known Galactic GC metallicity bimodality, our own analysis of M 31's metallicity distribution function (MDF) suggests that both GC systems cover basically the same [Fe/H] range yet M 31's MDF is not clearly bimodal. These results suggest that both galaxies experienced different star formation and accretion histories.

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“…More recently, a number of other element abundance sensitive models have been produced increasing the number of chemical elements considered, implementing other stellar libraries, and extending the approach to full spectral response (Annibali et al 2007;Schiavon 2007;Coelho et al 2007;Lee et al 2009;Worthey et al 2011;Conroy et al 2014).…”

Section: Brief History Of Element Ratio Modellingmentioning

confidence: 99%

Element abundance ratios in stellar population modelling

Thomas

2014

Proc. IAU

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Abstract. I review the implementation of the effects from varying chemical element abundance ratios in stellar population modelling, focusing on α-and Fe-peak elements. A brief overview of the development of such models over the past 30 years is provided, starting with early work on the identification of relevant absorption features in the spectra of early-type galaxies in the 1980s leading to the most recent developments of the past years. Recent highlights include the adoption of new flux calibrated libraries, the inclusion of a wide range of chemical elements, the calculation of error estimates on the model, and the consideration of element variation effects on full spectra. The calibration of such models with globular clusters and some key results on the element ratios measured in early-type galaxies are presented.

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Stellar Population Models and Individual Element Abundances. Ii. Stellar Spectra and Integrated Light Models

Cited by 70 publications

References 58 publications

The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. Ii. Results

The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. Ii. Results

Full spectral fitting of Milky Way and M 31 globular clusters: ages and metallicities

Element abundance ratios in stellar population modelling

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