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UniMass - Janine Pforr

Stellar Population Properties of Galaxies across the Cosmic Time
My research within the UNIMASS Excellence Grant team project focusses on the derivation of physical properties, such as stellar masses, ages and star formation rates, of large samples of galaxies over a wide range of redshifts to constrain galaxy formation and evolution.
A common tool to derive these properties is the fitting of modelled spectra to observed broad band spectral energy distributions.
For this, spectral templates covering a wide range of parameters, e.g. metallicity, star formation mode, age, and a large amount of photometric data are required.
The majority of galaxy properties reported in the literature and used for galaxy evolution studies is based on stellar population models lacking a complete treatment of the Thermally-Pulsing Asymptotic Giant Branch (TP-AGB) phase of stellar evolution. In the models by Maraston (2005) this phase has been included. In these models intermediate-age stellar populations (~0.2 - 2 Gyr) stars in this evolutionary phase make up roughly 40% of the bolometric and up to 80% of the light emission in the near-IR. It has been shown (Maraston et al. 2006 and several subsequent works) that the physical properties of galaxies depend on the stellar population models that is used to derive them, and on the treatment of the TP-AGB in particular.
Within the UniMass project I analyse galaxy data, e.g. from the GOODS and COSMOS surveys, using the up-to-date stellar population models of Maraston (2005) and the newest calculated within the Unimass project (Maraston Stromback et al. 2009 ) and obtain the physcal properties of galaxies for various surveys at at various redshifts.
The fitting is carried out using the publicly available code HyperZ (Bolzonella et al. 2000) and other codes that have been used for the Maraston et al. 2006 work on passive galaxies, including a macro written by Emanuele Daddi.
In addition, we fully explore and test the efficiency of spectral energy distribution fitting in recovering the true physical properties of galaxies, by using simulated galaxies given by semi-analytic galaxy formation models developed within the UniMass project (Tonini et al. 2009; 2010, see Chiara's web page).
This enable us not only to put constraints on galaxy formation and evolution and existing galaxy formation models, but also to help planning and exploit galaxy surveys. In particular, I am involved in the BOSS, WISE and SERVS surveys.