Spectral models for solar-scaled and α-enhanced stellar populations

By Paula Coelho, G. Bruzual, S. Charlot, A. Weiss, B. Barbuy, J. Ferguson. Monthly notices of the Royal Astronomical Society, 2007

136 citations recorded by the source corpus.

We present the first models allowing one to explore in a consistent way the influence of changes in the α-element-to-iron abundance ratio on the high-resolution spectral properties of evolving stellar populations. The models cover the wavelength range from 3000 Å to 1.34 μm at a constant resolution of full width at half-maximum (FWHM) = 1 Å and a sampling of 0.2 Å, for overall metallicities in the range 0.005 ≤Z≤ 0.048 and for stellar population ages between 3 and 14 Gyr. These models are based on a recent library of synthetic stellar spectra and a new library of stellar evolutionary tracks, both computed for three different iron abundances ([Fe/H]=−0.5, 0.0 and 0.2) and two different α-element-to-iron abundance ratios ([α/Fe]= 0.0 and 0.4). We expect our fully synthetic models to be primarily useful for evaluating the differential effect of changes in the α/Fe ratio on spectral properties such as broad-band colours and narrow spectral features. In addition, we assess the accuracy of absolute model predictions in two ways: first, by comparing the predictions of models for scaled-solar metal abundances ([α/Fe]= 0.0) to those of existing models based on libraries of observed stellar spectra; and secondly, by comparing the predictions of models for α-enhanced metal abundances ([α/Fe]= 0.4) to observed spectra of massive early-type galaxies in the Sloan Digital Sky Survey Data Release 4. We find that our models predict accurate strengths for those spectral indices that are strongly sensitive to the abundances of Fe and α elements. The predictions are less reliable for the strengths of other spectral features, such as those dominated by the abundances of C and N, as expected from the fact that the models do not yet allow one to explore the influence of these elements in an independent way. We conclude that our models are a powerful tool for extracting new information about the chemical properties of galaxies for which high-quality spectra have been gathered by modern surveys.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/1083e7d8d503e29c9ead0fc7b10b9ee08c5a604c

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In Astronomy and Astrophysics

1. C. Conroy
2. P. V. van Dokkum
3. M. Cappellari
4. P. Hopkins
5. J. Dunlop
6. A. Renzini
7. L. Hernquist
8. A. Koekemoer

In Instrumentation

1. C. Conroy
2. P. V. van Dokkum
3. J. Dunlop
4. M. Cappellari
5. A. Renzini
6. M. Franx
7. A. Koekemoer
8. R. McLure

Citations in the corpus

• THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES FROM ABSORPTION LINE SPECTROSCOPY. II. RESULTS (2012, background): “Most SPS models that consider variable abundance patterns do not include the abundance effects on the isochrones (e.g., Thomas et al. 2003; Graves & Schiavon 2008; Thomas et al. 2011a), with the exception of the models of Coelho et al. (2007) and Lee et al. (2009).”
• Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models (2015, methodology): “It has been shown that by using α-enhanced stellar evolution models (e.g. Salaris, Groenewegen & Weiss 2000) and the stellar theoretical spectra (e.g. Tripicco & Bell 1995; Korn et al. 2005; Coelho et al. 2007), line indices such as Mgb and 〈Fe〉 are affected.”
• Fitting the integrated spectral energy distributions of galaxies (2010, background): “However recently this also has been changing, with stellar libraries exploring abundance changes such as α-enhancement as well (e.g. Coelho et al. 2007).”
• COUNTING LOW-MASS STARS IN INTEGRATED LIGHT (2011, background): “Second, although changes in metallicity induce changes in the temperatures of stars, this effect is dwarfedby the much larger change in the spectra of stars at fixed temperature when metallicity varies, especially for old ages (>5 Gyr; see Coelho et al. 2007; Schiavon 2007; Lee et al. 2009).”
• Flux-calibrated stellar population models of Lick absorption-line indices with variable element abundance ratios (2010, methodology): “The latter are known to suffer from incomplete line lists and continuum uncertainties, however (Korn et al. 2005; Rodrı́guez-Merino et al. 2005; Coelho et al. 2007; Lee et al. 2009; Walcher et al. 2009).”
• Evolutionary stellar population synthesis with MILES – I. The base models and a new line index system (2010, unknown): “Models that use such libraries are, e.g., Schiavon et al. (2000), González-Delgado et al. (2005), Coelho et al. (2007).”
• Modeling the Panchromatic Spectral Energy Distributions of Galaxies (2013, methodology): “Such models have existed for the Lick indices since the late 1990s while models for the full optical-NIR spectrum have only recently become available (Coelho et al. 2007, Walcher et al. 2009, Conroy & van Dokkum 2012a).”
• MIUSCAT: extended MILES spectral coverage – I. Stellar population synthesis models (2012, background): “There are models that are fed with theoretical stellar atmospheres (e.g., Schiavon et al. 2000; González-Delgado et al. 2005; Coelho et al. 2007), whereas other models employ empirical libraries, mostly in the visible (e.g., Vazdekis 1999; Bruzual & Charlot 2003; Le Borgne et al. 2004; Conroy &…”
• An updated MILES stellar library and stellar population models (2011, methodology): “Spectra were retrieved from http://www.cruzeirodosul.edu. br/nat/modelos.html, and are described in Coelho et al. (2005) and Coelho et al. (2007).”
• Stellar population models at high spectral resolution (2011, background): “…gravity, metallicity) and in the wavelength extension, known problems exist in the modelling of specific lines (e.g. the Hβ line at ∼ 4861 Å, Coelho et al. 2007; Walcher et al. 2009) as well as continuum regions due to line blanketing (around the V band, Worthey 1994) and around the g,…”
• Bimodal gas accretion in the Horizon–MareNostrum galaxy formation simulation (2008, methodology): “…of galaxies (rather than dark matter haloes), computing their luminosities and colours according to the age and metallicity distributions of their stars using stellar population models such as Bruzual & Charlot (2003); Fioc & Rocca-Volmerange (1997); Le Borgne et al. (2004); Coelho et al. (2007).”
• Age-dating luminous red galaxies observed with the Southern African Large Telescope (2016, background): “…et al. 1999; Bruzual & Charlot 2003; Le Borgne et al. 2004; Jimenez et al. 2004; González Delgado et al. 2005; Maraston 2005; Tantalo 2005; Coelho et al. 2007; Schiavon 2007; Conroy, Gunn, & White 2009; Eldridge & Stanway 2009; Kotulla et al. 2009; Mollá, García-Vargas, & Bressan 2009;…”
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies (2016, methodology): “The latter has been employed for computing spectra of singleage, single-metallicity stellar populations (SSPs) with varying abundance ratios, either fully theoretical (e.g. Coelho et al. 2007) or combined with empirical libraries (e.g. Walcher et al. 2009; Vazdekis et al. 2015).”
• Cosmic chronometers: constraining the equation of state of dark energy. I: H(z) measurements (2009, unknown): “Further, there has been significant advancement in the last few years in modeling stellar populations of LRG galaxies [38, 55, 56] and the differential technique has been”
• MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA) (2010, methodology): “…2000; Dotter et al. 2010), the integrated light of distant galaxies and star clusters via population synthesis techniques (e.g., Worthey 1994; Coelho et al. 2007), stellar yields and galactic chemical evolution (e.g., Timmes et al. 1995), physics of the first stars (Fujimoto et al. 2000),…”
• Improved constraints on the expansion rate of the Universe up to z ∼ 1.1 from the spectroscopic evolution of cosmic chronometers (2012, background): “[97] are available(7) for 6 chemical mixtures, at 3 fixed values of [Fe/H] one model solar scaled and one α-enhanced for which the abundances of all classical α elements are increased by 0.”