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

Abstract

We introduce STECKMAP (STEllar Content and Kinematics via Maximum A\nPosteriori), a method to recover the kinematical properties of a galaxy\nsimultaneously with its stellar content from integrated light spectra. It is an\nextension of STECMAP (astro-ph/0505209) to the general case where the velocity\ndistribution of the underlying stars is also unknown.\n %and can be used as is for the analysis of large sets of data. The\nreconstructions of the stellar age distribution, the age-metallicity relation,\nand the Line-Of-Sight Velocity Distribution (LOSVD) are all non-parametric,\ni.e. no specific shape is assumed. The only a propri we use are positivity and\nthe requirement that the solution is smooth enough. The smoothness parameter\ncan be set by GCV according to the level of noise in the data in order to avoid\noverinterpretation. We use single stellar populations (SSP) from PEGASE-HR\n(R=10000, lambda lambda = 4000-6800 Angstrom, Le Borgne et al. 2004) to test\nthe method through realistic simulations. Non-Gaussianities in LOSVDs are\nreliably recovered with SNR as low as 20 per 0.2 Angstrom pixel. It turns out\nthat the recovery of the stellar content is not degraded by the simultaneous\nrecovery of the kinematic distribution, so that the resolution in age and error\nestimates given in Ocvirk et al. 2005 remain appropriate when used with\nSTECKMAP. We also explore the case of age-dependent kinematics (i.e. when each\nstellar component has its own LOSVD). We separate the bulge and disk components\nof an idealized simplified spiral galaxy in integrated light from high quality\npseudo data (SNR=100 per pixel, R=10000), and constrain the kinematics (mean\nprojected velocity, projected velocity dispersion) and age of both components.\n