Evolutionary stellar population synthesis with MILES – I. The base models and a new line index system

By A. Vazdekis, P. Sánchez-Blázquez, J. Falc'on-Barroso, A. Cenarro, M. Beasley, N. Cardiel, J. Gorgas, Reynier Peletier. 2010

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We present synthetic spectral energy distributions (SEDs) for single-age, single-metallicity stellar populations (SSPs) covering the full optical spectral range at moderately high resolution [full width at half-maximum (FWHM) = 2.3A]. These SEDs constitute our base models, as they combine scaled-solar isochrones with an empirical stellar spectral library [Medium resolution INT Library of Empirical Spectra (MILES)], which follows the chemical evolution pattern of the solar neighbourhood. The models rely as much as possible on empirical ingredients, not just on the stellar spectra, but also on extensive photometric libraries, which are used to determine the transformations from the theoretical parameters of the isochrones to observational quantities. The unprecedented stellar parameter coverage of the MILES stellar library allowed us to safely extend our optical SSP SED predictions from intermediate- to very-old-age regimes and the metallicity coverage of the SSPs from super-solar to [M/H] = -2.3. SSPs with such low metallicities are particularly useful for globular cluster studies. We have computed SSP SEDs for a suite of initial mass function shapes and slopes. We provide a quantitative analysis of the dependence of the synthesized SSP SEDs on the (in)complete coverage of the stellar parameter space in the input library that not only shows that our models are of higher quality than those of other works, but also in which range of SSP parameters our models are reliable. The SSP SEDs are a useful tool to perform the analysis of stellar populations in a very flexible manner. Observed spectra can be studied by means of full spectrum fitting or by using line indices. For the latter, we propose a new line index system to avoid the intrinsic uncertainties associated with the popular Lick/IDS system and provide more appropriate, uniform, spectral resolution. Apart from constant resolution as a function of wavelength, the system is also based on flux-calibrated spectra. Data can be analysed at three different resolutions: 5, 8.4 and 14A (FWHM), which are appropriate for studying globular cluster, low- and intermediate-mass galaxies, and massive galaxies, respectively. Furthermore, we provide polynomials to transform current Lick/IDS line index measurements to the new system. We provide line index tables in the new system for various popular samples of Galactic globular clusters and galaxies. We apply the models to various stellar clusters and galaxies with high-quality spectra, for which independent studies are available, obtaining excellent results. Finally, we designed a web page from which not only these models and stellar libraries can be downloaded but which also provides a suite of on-line tools to facilitate the handling and transformation of the spectra.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/bb6a500cf257a4dd80fe61c9f7ea91a46c120a4a

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Citations in the corpus

The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA-derived Quantities, Data Visualization Tools, and Stellar Library (2018, methodology): “…continuum to isolate emission lines, and calculating stellar population models (e.g. Leitherer et al. 1999; Bruzual & Charlot 2003; Maraston 2005; Vazdekis et al. 2010; Conroy & Gunn 2010; Conroy 2013) for deriving age, metallicity, and stellar mass of the stellar populations from integrated…”
MIUSCAT: extended MILES spectral coverage – I. Stellar population synthesis models (2012, methodology): “To estimate the reliability of the newly computed SEDs and the SSP parameter regions where these models can be considered safe, we use the normalized quality parameter Qn defined in Vazdekis et al. (2010).”
GASP. I. Gas Stripping Phenomena in Galaxies with MUSE (2017, methodology): “To extract the stellar kinematics from the spectrum, we use the Penalized Pixel-Fitting (pPXF) code (Cappellari & Emsellem 2004), fitting the observed spectra with the stellar population templates by Vazdekis et al. (2010).”
Age-dating luminous red galaxies observed with the Southern African Large Telescope (2016, methodology): “…(ii) techniques that fit features in the spectra such as Lick– index fitting (e.g. Worthey & Ottaviani 1997; Bruzual & Charlot 2003; Thomas, Maraston, & Bender 2003; Lee & Worthey 2005; Annibali et al. 2007; Schiavon 2007; Lee et al. 2009; Vazdekis et al. 2010; Thomas, Maraston, & Johansson 2011).”
Re-evaluating old stellar populations (2018, methodology): “We also show the linear relation derived by Usher et al. (2012), based on the models of Vazdekis et al. (2010).”
New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies (2016, methodology): “(0000) CAT library of spectral templates (Vazdekis et al. 2012; Ricciardelli et al. 2012), an extension of the previous MILES library (Falcón-Barroso et al. 2011; Cenarro et al. 2001; Vazdekis et al. 2010; Sánchez-Blázquez et al. 2006) in which both Indo-U.”
UV-extended E-MILES stellar population models: young components in massive early-type galaxies (2016, methodology): “To estimate the quality of the SSP spectra in the UV range we follow the quantitative approach introduced in Vazdekis et al. (2010), which makes use of the interpolation algorithm described in Section 2.”
CALIFA, the Calar Alto Legacy Integral Field Area survey - III. Second public data release (2012, methodology): “The CALIFA spectra are decomposed in terms of combinations of SSP spectra from González Delgado et al. (2005) and Vazdekis et al. (2010) including a dust extinction term following the Cardelli et al. (1989) law.”
Metallicity gradients in local field star-forming galaxies: insights on inflows, outflows, and the coevolution of gas, stars and metals (2015, methodology): “To model the stellar continuum, we adopt the penalised pixelfitting routine (PPXF; Cappellari & Emsellem 2004) and employ the empirical MIUSCAT4 SSP models of 13 ages5 and 4 metallicities6 (Vazdekis et al. 2010) while assuming a Salpeter initial mass function (IMF; Salpeter 1955).”
The CALIFA survey across the Hubble sequence: Spatially resolved stellar population properties in galaxies (2015, methodology): “Base GMe is a combination of the SSP spectra provided by Vazdekis et al. (2010) for populations older than t = 63 Myr and the González Delgado et al. (2005) models for younger ages.”
Modeling the Panchromatic Spectral Energy Distributions of Galaxies (2013, methodology): “Nearly all SPS models provide SSPs as a ‘black-box’ (e.g., Leitherer et al. 1999, Bruzual & Charlot 2003, Maraston 2005, Vazdekis et al. 2010).”
SPIDER VIII - constraints on the stellar initial mass function of early-type galaxies from a variety of spectral features (2013, methodology): “…width changes by less than 0.01 Å in all bins). c© 2013 RAS, MNRAS 000, 1–34 7350 Å, with three different sets of simple stellar population (SSP) models, namely, Bruzual & Charlot (2003, BC03), updated Charlot & Bruzual (often refereed to as CB07), and MILES models (Vazdekis et al. 2010, MI10).”
Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models (2015, methodology): “Models that employ such libraries are, e.g. Vazdekis (1999), Schiavon et al. (2002), Bruzual & Charlot (2003), Le Borgne et al. (2004), Vazdekis et al. (2010), Maraston & Strömbäck (2011), Conroy & MNRAS 449, 1177–1214 (2015) D ow nloaded from https://academ ic.oup.com /m…”
A CONTINUUM OF H- TO He-RICH TIDAL DISRUPTION CANDIDATES WITH A PREFERENCE FOR E+A GALAXIES (2014, methodology): “We fit the host spectra to stellar templates provided by the miles empirical stellar library (Sánchez-Blázquez et al. 2006; Vazdekis et al. 2010), using ppxf (Cappellari & Emsellem 2004) and gandalf (Sarzi et al. 2006).”
The star formation history of CALIFA galaxies: Radial structures (2013, methodology): “…put them all together), and for this reason we have performed spectral fits using three different sets of SSPs: (a) The GM base is a combination of the SSP spectra provided by Vazdekis et al. (2010) for populations older than 63 Myr and the González Delgado et al. (2005) models for younger ages.”
Stellar population models at high spectral resolution (2011, methodology): “Vazdekis et al. (2010) provide their models based on the MILES library.”
Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions (2016, methodology): “…et al. 2005; Munari et al. 2005; Gustafsson et al. 2008), and stellar population models based on these libraries (e.g. Bruzual & Charlot 2003; Vazdekis et al. 2010; Maraston & Strömbäck 2011; Conroy & van Dokkum 2012), it has become common practice to extract the stellar kinematics by…”