Stellar populations and their kinematics from high and medium resolution spectra: mixed inversions
P. Ocvirk $^{1}$
A. Lancon $^{1}$
C. Pichon
We present inversion techniques aiming at recovering the stellar content (age, metallicity, extinction) and kinematics of a stellar population from its absorption line spectrum. These techniques use new synthetic high resolution spectra produced by PEGASE\_HR and minimization algorithms. Application to SDSS data and to a simulated disc-bulge system are shown.
ocvirk.tex
%%%%%%%%%%%%%%%%%%%%%%% file template_SF2A.tex %%%%%%%%%%%%%%%%%%%%%%%%%
% This is a template file for SF2A-2003 proceedings
%==========================================
%Les Comptes-Rendus 2003, seront publi�s
%par EDP-Sciences, en anglais.

%La deadline est   le 1er Octobre 2003.

%Le nombre limite (tr�s stricte!) de pages est:
%*    Revues et Contributions orales - 4 pages
%*    Posters - 2 pages
%Les macros de style edp-conf.cls  sont sur le site web
%Veuillez les respecter strictement (pas de bibtex par exemple, etc..).
%Les fichiers .tex et .ps (nomenclature: nom.tex, nom_fig1.ps, nom_fig2a.ps,
%nom_fig2b.ps) seront envoy�s par ftp anonyme:

%ftp aramis.obspm.fr
%login anonymous
%cd incoming/sf2a
%mkdir author1
%cd author1
%ascii
%hash (to print `#' for each buffer transferred)
%put author1.tex
%put author1_fig1.ps
%etc..
%bye
%Puis alerter les �diteurs de votre envoi, par mail � sf2a@cesr.fr. Merci!
%%%%%%%%%%%%%%%%%%%%%%%%   EDP Sciences  %%%%%%%%%%%%%%%%%%%%%%%%%%
%
\documentclass{edp-conf}
\usepackage{graphicx}
%\usepackage[]{inputenc,amssymb,enumerate,color}
%
%%%%%%%%%%%%%--PREAMBLE--%%%%%%%%%%%%%%%%%%
%%-----------------------------
%         your macros
%%-------------------------%%----
%%%%%%%%%%%%%%%--BODY--%%%%%%%%%%%%%%%%%%
%
\begin{document}

\TitreGlobal{SF2A 2003}

%%-----------------------------
%%      the top matter
%%-----------------------------
\title{Stellar populations and their kinematics from high and medium
resolution spectra: mixed inversions}
%
\author{P. Ocvirk $^{1}$, A. Lancon $^{1}$, C. Pichon}\address{Observatoire de Strasbourg,
$^{2}$ CRAL, $^{3}$ Institut d'Astrophysique de Paris, $^{4}$  Observatoire de Bordeaux}
\author{P. Prugniel $^{2}$, E. Thiebaut $^{2}$}
\author{D. Le Borgne $^{3}$, B. Rocca-Volmerange $^{3}$, M. Fioc $^{3}$}
\author{C. Soubiran $^{4}$}
\runningtitle{Inversions of galaxy spectra}
%
\setcounter{page}{237}
% Keep this line, even if the page will be settled afterwards..
\index{Ocvirk, P.}
\index{Lancon, A.}
\index{Lancon, A.}
\index{Pichon, C.}
\index{Prugniel, P.}
\index{Thi\'{e}baut, E.}
\index{Thiebaut, E.}
\index{Le Borgne, D.}
\index{Rocca-Volmerange B.}
\index{Fioc, M.}
\index{Soubiran, E.}
% Repeat the authors here, this will help to make the final index

\maketitle
%
\begin{abstract} 
We present inversion techniques aiming at recovering the stellar content
(age, metallicity, extinction) and kinematics of a stellar population from its
absorption line spectrum. These techniques use new synthetic high
resolution spectra produced by PEGASE\_HR 
and minimization algorithms. Application to SDSS data and to a simulated disc-bulge system are shown.
\end{abstract}
%Such
%automated techniques have become mandatory for the analysis of large
%datasets.
%
%%-----------------------------
%%      your text
%%-----------------------------
\section{Introduction}
The high resolution spectrographs now installed on 10m-class telescopes open new perspectives in the exploration of the formation of galaxies. This poster presents the first attempt to fit simultaneously the local line-of-sight velocity distribution (LOSVD) and the nature of the stellar population. It is based on efficient non-parametric inversion procedures.
\section{Models of galaxy spectra}
PEGASE\_HR (Fioc \& Rocca-Volmerange 1997; Le
Borgne et al., 2002) produces high resolution synthetic spectra of evolved Single Stellar
Populations (SSPs) assuming a given IMF and stellar evolution tracks. We build
a basis of such spectra by computing SSPs for a set of ages and metallicities. A model galaxy spectrum is a linear combination of the components of
this basis obscured by a dust extinction model and convolved by a
velocity distribution. The model galaxy spectrum thus depends on the following
4 sets of
unknowns: the weight of each component, the metallicity of each component,
the color excess seen by the component and finally the global LOSVD of the
whole population.
\section{Inversion of galaxy spectra}
Inverting an observed spectrum involves recovering the 4 sets of
unknowns. We follow a maximum a posteriori likelihood formulation, assuming
gaussian errors. This inversion problem thus turns into minimizing a
chi-square with a quadratic penalization. Simulations have been performed to investigate the behaviour of the method for several
pseudo-observational contexts.
\section{Application to SDSS data}
As an example, the stellar
content, reddening and kinematic information have been reconstructed for the galaxy
SDSS-51630-0266-001 and shown in figure \ref{f:sdss}. Application to a larger
systematic subset of SDSS data is on course.
%Having estimated the level of significance of the recon
\section{Application to disc-bulge separation}
We have studied the feasibility of separating the disc light from the bulge
light in an idealized case where the disc and bulge stellar populations are
different in SFH and kinematics, mono-metallic and seen without
extinction (figure \ref{f:cki}).

%\begin{figure}[h]
%   \centering
%  If you have a figure, remove the comments % before...
%   \includegraphics[width=9cm]{author1_fig1.ps}
%      \caption{ My caption here..}
%       \label{figure_mafig}
%   \end{figure}

\begin{figure}[h]  
\centerline{
\resizebox{2.5cm}{2.5cm}{{\includegraphics{ocvirk_fig1.ps}}}
\resizebox{2.5cm}{2.5cm}{{\includegraphics{ocvirk_fig2.ps}}}
\resizebox{2.5cm}{2.5cm}{{\includegraphics{ocvirk_fig3.ps}}}
\resizebox{2.5cm}{2.5cm}{{\includegraphics{ocvirk_fig4.ps}}}
\resizebox{2.5cm}{2.5cm}{{\includegraphics{ocvirk_fig5.ps}}}}
\caption{ Results of the inversion of the spectrum of the galaxy
SDSS-51630-0266-001. }  
\label{f:sdss}
\end{figure}

\begin{figure}[h]  
\centerline{
\resizebox{3.3cm}{3.3cm}{{\includegraphics{ocvirk_fig7.ps}}}
\resizebox{3.3cm}{3.3cm}{{\includegraphics{ocvirk_fig6.ps}}}}
\caption{ Model and reconstruction of a simulated disc-bulge system. }  
\label{f:cki}
\end{figure}



%%-----------------------------
%%      your bibliography
%%-----------------------------
\begin{thebibliography}{}
%\bibitem{}Einstein, A., 1926, ApJ, 63, 196
\bibitem{}Fioc, M., Rocca-Volmerange, B., A\&A, 326, 950
%\bibitem{spectral synthesis with PEGASE-HR}Le Borgne, D., Fioc, M., Lancon,
%A., Prugniel P., Rocca-Volmerange, B., Soubiran, C.,  2002, in prep. 
\bibitem{spectral synthesis with PEGASE-HR}Le Borgne, D. et al., SF2A-2002
conference series proceedings, p.347
%\bibitem{} Le Borgne, D. et al, SF2A-2002: Semaine de l'Astrophysique
%Francaise, meeting held in Paris, France, June 24-29, 2002, Eds.: F. Combes
%and D. Barret, EdP-Sciences (Editions de Physique), Conference Series, p. 347

\end{thebibliography}
\end{document}
%%%%%%%%%% fin de file template %%%%%%%%%%%%%%%%%%%%%%%%%%%%%

astro-ph0310543.extracted_bib
\begin{thebibliography}{}
%\bibitem{}Einstein, A., 1926, ApJ, 63, 196
\bibitem{}Fioc, M., Rocca-Volmerange, B., A\&A, 326, 950
%\bibitem{spectral synthesis with PEGASE-HR}Le Borgne, D., Fioc, M., Lancon,
%A., Prugniel P., Rocca-Volmerange, B., Soubiran, C.,  2002, in prep. 
\bibitem{spectral synthesis with PEGASE-HR}Le Borgne, D. et al., SF2A-2002
conference series proceedings, p.347
%\bibitem{} Le Borgne, D. et al, SF2A-2002: Semaine de l'Astrophysique
%Francaise, meeting held in Paris, France, June 24-29, 2002, Eds.: F. Combes
%and D. Barret, EdP-Sciences (Editions de Physique), Conference Series, p. 347

\end{thebibliography}