STECKMAP: STEllar Content and Kinematics from high resolution galactic spectra via Maximum A Posteriori

By P. Ocvirk, C. Pichon, Ariane Lançon, E. Strasbourg, I. D. Paris, Observatoire de Lyon. 2005

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We introduce STECKMAP (STEllar Content and Kinematics via Maximum A Posteriori likelihood), a method for recovering the kinematic properties of a galaxy simultaneously with its stellar content from integrated light spectra. It is an extension of STECMAP (presented recently by Ocvirk et al.) to the general case where the velocity distribution of the underlying stars is also unknown. The reconstructions of the stellar age distribution, the age‐metallicity relation and the line-of-sight velocity distribution (LOSVD) are all non-parametric, i.e. no specific shape is assumed. The only a priori conditions that we use are positivity and the requirement that the solution is smooth enough. The smoothness parameter can be set by generalized cross-validation according to the level of noise in the data in order to avoid overinterpretation. We use single stellar populations (SSPs) from P´-HR (R = 10 000, λ = 4 000‐6 800 A, from Le Borgne et al.) to test the method through realistic simulations. Non-Gaussianities in LOSVDs are reliably recovered with signal-to-noise ratio (SNR) as low as 20 per 0.2 A pixel. It turns out that the recovery of the stellar content is not degraded by the simultaneous recovery of the kinematic distribution, so that the resolution in age and error estimates given in Ocvirk et al. remain appropriate when used with STECKMAP. We also explore the case of age-dependent kinematics (i.e. when each stellar component has its own LOSVD). We separate the bulge and disc components of an idealized simplified spiral galaxy in integrated light from high-quality pseudo-data (SNR = 100 per pixel, R = 10 000), and constrain the kinematics (mean projected velocity, projected velocity dispersion) and age of both components. Ke yw ords: methods: data analysis ‐ methods: statistical ‐ techniques: spectroscopic ‐ galaxies: abundances ‐ galaxies: kinematics and dynamics ‐ galaxies: stellar content.

Subfields: Astronomy and Astrophysics, Computer Vision and Pattern Recognition

View Paper: https://www.semanticscholar.org/paper/7a02f428b6ee3be13c1f38007bec1d99ccaefd6f

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Citations in the corpus

Bimodal gas accretion in the Horizon–MareNostrum galaxy formation simulation (2008, methodology): “This observation is further supported by the analysis of spectroscopic data, using star formation history reconstruction methods (Reichardt et al. 2001; Panter et al. 2003; Cid Fernandes et al. 2004; Ocvirk et al. 2006b,a).”
Stellar population gradients in galaxy discs from the CALIFA survey - The influence of bars (2014, methodology): “To derive star formation histories we used the code STECKMAP (STEllar Content and Kinematics via Maximum A Posteriori likelihood, Ocvirk et al. 2006a,b) on the emission linecleaned spectra (see previous section).”
Fitting the integrated spectral energy distributions of galaxies (2010, methodology): “It uses the method described in Ocvirk et al. (2006) to estimate at each step, how many parameters can be recovered for a linear problem perturbed by noise.”
A census of metals and baryons in stars in the local universe (2007, methodology): “…extended to the SDSS DR3 (three times larger sample) by Panter et al. (2007), with improvements both in the data and in the modelling sides (see also Ocvirk et al. 2006; Cid Fernandes et al. 2007; Tojeiro et al. 2007 for similar methods to recover stellar content and SFHs from galaxy spectra).”
Evolutionary stellar population synthesis with MILES – I. The base models and a new line index system (2010, methodology): “In fact, there is a growing body of full spectrum fitting algorithms that are being developed for constraining and recovering in part the Star Formation History (e.g., Panter et al. 2003; Cid Fernandes et al. 2005; Ocvirk et al. 2006ab; Koleva et al. 2008).”
Spectroscopic ages and metallicities of stellar populations : validation of full spectrum fitting (2008, methodology): “The method has been presented in several places (Prugniel et al. 2003; Ocvirk et al. 2006a,b) and its reliability assessed on the basis of various simulations.”