ULySS: a full spectrum fitting package

By M. Koleva, P. Prugniel, A. Bouchard, Yue Wu. 2009

379 citations recorded by the source corpus.

Aims. We provide an easy-to-use full-spectrum fitting package and explore its applications to (i) the determination of the stellar atmospheric parameters and (ii) the study of the history of stellar populations. Methods. We developed ULySS, a package to fit spectroscopic observations against a linear combination of non-linear model components convolved with a parametric line-of-sight velocity distribution. The minimization can be either local or global, and determines all the parameters in a single fit. We use χ 2 maps, convergence maps and Monte-Carlo simulations to study the degeneracies, local minima and to estimate the errors. Results. We show the importance of determining the shape of the continuum simultaneously to the other parameters by including a multiplicative polynomial in the model (without prior pseudo-continuum determination, or rectification of the spectrum). We also stress the usefulness of using an accurate line-spread function, depending on the wavelength, so that the line-shape of the models properly matches the observation. For simple models, i.e., to measure the atmospheric parameters or the age/metallicity of a singleage stellar population, there is often a unique minimum, or when local minima exist they can be recognized unambiguously. For more complex models, Monte-Carlo simulations are required to assess the validity of the solution. Conclusions. The ULySS package is public, simple to use and flexible. The full spectrum fitting makes optimal use of the signal.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/80d1f220ad39cd3322c4cb2bf514c1829cfb7c48

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Citations in the corpus

Evidence of Environmental Dependencies of Type Ia Supernovae from the Nearby Supernova Factory indicated by Local H$\alpha$ (2013, methodology): “The University of Lyon Spectroscopic analysis Software1 (ULySS, Koleva et al. 2008, 2009) is used to disentangle the stellar and gas components.”
The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA-derived Quantities, Data Visualization Tools, and Stellar Library (2018, methodology): “The color-coding are based on our preliminary measurement of metallicity using the ULySS pipeline (Koleva et al. 2009, 2011) with MILES (Sánchez-Blázquez et al. 2006) as the training set.”
The atmospheric parameters and spectral interpolator for the MILES stars (2011, methodology): “We determined it following the precepts of Koleva et al. (2009).”
UV-extended E-MILES stellar population models: young components in massive early-type galaxies (2016, methodology): “28 we show the ULySS fit obtained for M32 in the spectral range covering the Mg features at ∼ 2800Å.”
ACCURATE STELLAR KINEMATICS AT FAINT MAGNITUDES: APPLICATION TO THE BOÖTES I DWARF SPHEROIDAL GALAXY (2011, methodology): “…subtraction from either the object or the template, which is advantageous since that is always a poorly defined task; instead we rely on the continuum shape from the synthetic spectrum, with additional polynomial modifications (cf Koleva et al. (2009) for a discussion of continuum fitting).”
Modeling the Panchromatic Spectral Energy Distributions of Galaxies (2013, methodology): “This is precisely the approach taken by several groups, including MOPED (Heavens, Jimenez & Lahav 2000), STARLIGHT (Cid Fernandes et al. 2005), STECMAP (Ocvirk et al. 2006), VESPA (Tojeiro et al. 2007), ULySS (Koleva et al. 2009), and MacArthur, González & Courteau (2009).”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, methodology): “To model the observed spectra and obtain chemical abundances and radial velocities we use a direct pixel-fitting approach by interpolated spectral templates (see e.g. Koleva et al. 2009; Koposov et al. 2011; Walker, Olszewski & Mateo 2015).”
Modelling and interpreting spectral energy distributions of galaxies with BEAGLE (2016, background): “In practice, most codes designed to fit galaxy spectra (e.g. PPXF, Cappellari & Emsellem 2004; STARLIGHT, Cid Fernandes et al. 2005; STECKMAP, Ocvirk et al. 2006; ULYSS, Koleva et al. 2009) suffer from intrinsic limitations.”
Coudé-feed stellar spectral library – atmospheric parameters (2010, methodology): “To determine the optimal order of the multiplicative polynomial, n, we proceeded as suggested in (Koleva et al. 2009b).”
Four new observational H(z) data from luminous red galaxies in the Sloan Digital Sky Survey data release seven (2012, methodology): “…convolved with a line-of-sight velocity distribution (LOSVD), multiplied by annth order polynomial ofPn(λ) and summed to another polynomial ofQm(λ) (for more details please refer to Koleva et al., 2009b): Fobs(λ) = Pn(λ) × {LOS VD(vsys, σ, h3, h4)⊗ i=k ∑ i=0 WiCMPi(a1, a2, a3, ..., λ)} + Qm(λ).”
Fitting the integrated spectral energy distributions of galaxies (2010, methodology): “More sophisticated schemes proceed in an iterative way, i.e. alternate linear inversion and a nonlinear minimization scheme (Koleva et al. 2009), or use nonlinear minimization schemes for all parameters (Cid Fernandes et al. 2005).”
Stellar Population Inference with Prospector (2020, methodology): “These so-called nonparametric – actually many-parameter – models have become the standard in SFH inference from (semi-) resolved stellar color-magnitude diagrams (e.g., Dolphin 1997; Harris & Zaritsky 2001; Weisz et al. 2011; Cook et al. 2019) and have been used in maximum-likelihood “inversion” cod”
Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models (2015, methodology): “…use these model SEDs with newly developed algorithms that aim at constraining and recovering the SFH by means of full spectrum-fitting approach (e.g. Panter, Heavens & Jimenez 2003; Cid Fernandes et al. 2005; Ocvirk et al. 2006a,b; Chilingarian et al. 2007; Koleva et al. 2009; Tojeiro et al. 2011).”
The first data release (DR1) of the LAMOST regular survey (2015, methodology): “ULySS method:The ULySS (Université de Lyon Spectroscopic analysis Software, Koleva et al. 2009; Wu et al. 2011a, available atht p://ulyss.univ-lyon1.fr/) package is employed by LASP to derive the stellar parameters via minimizing the squareddifference between the observations and the model.”
Automatic determination of stellar atmospheric parameters and construction of stellar spectral templates of the Guoshoujing Telescope (LAMOST) (2011, methodology): “In this work we employed ULySS4 (Universit́e de Lyon Spectroscopic analysis Software, Koleva et al. 2009a) to analyze the selected spectra.”
Age-dating luminous red galaxies observed with the Southern African Large Telescope (2016, methodology): “In this paper, we derive their ages by applying the full spectral fitting method using the ulyss package developed by Koleva et al. (2009a).”
A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA (2013, background): “…been developed to model the underlying stellar population, effectively decoupling it from the emission lines (e.g., Cappellari & Emsellem 2004; Cid Fernandes et al. 2005; Ocvirk et al. 2006; Sarzi et al. 2006; Sánchez et al. 2006; Koleva et al. 2009; MacArthur et al. 2009; Walcher et al. 2011).”