STEMAGE · Towards an unbiased view of the role of stellar mass in galaxy evolution

Towards an unbiased view of the role of stellar mass in galaxy evolution

During the four years funded by the CIG, the Fellow has developed a complex set of tools to “digest” datasets of integral field spectroscopy (IFS, specifically CALIFA) and imaging photometry (specifically SDSS) to derive spatially resolved maps of stellar population properties and stellar mass in particular (plus complementary information on the ISM and kinematics). A substantial part of the activity has been devoted to the quality assessment and statistical characterization of the sample dataset. The Fellow was head of the Quality Control in the CALIFA collaboration since 2013 until the final data release of 667 galaxies in April 2016. In parallel, a lot of work has been conducted to develop and test the methods and the actual reference models to derive stellar population parameters from the observed data. The new models take advantage of the latest stellar spectral libraries and implement more realistic types of star-formation and chemical-enrichment histories. Systematic effects and biases in parameter recovery have been tested and minimized by means of extensive simulations. The first set of direct science results has been published in the paper by Zibetti et al. (2017, MNRAS), in which the bimodality in the distribution of stellar ages on sub-galactic scales is analyzed as a function of stellar-mass surface density. The paper also presents the method and its novelties. The core paper of the project, presenting the calibration of 1- and 2-colour relations with the stellar mass-to-light ratio, is in preparation: the dataset and all physical parameters are now frozen, and the plan is to submit the paper by the end of June 2017. A third paper on resolution effects, based on the same frozen dataset and analysis, is also in preparation, all the procedures being already in place and tested, with preliminary results already presented in conferences/workshops in the past years. The unpublished/partial results of this work have been employed in collaboration papers, including one on Nature (Toft et al., 2017, Nature, accepted) about the stellar population properties and the kinematics of a high-redshift lensed galaxy. The Fellow has given substantial contributions to a number of papers of the CALIFA collaboration about stellar populations and the link of different properties (to stellar-mass surface density. Moreover, the technical and scientific expertise gained in these years have been used in collaboration projects based on IFS and deep spectroscopy of distant galaxies, including two proposals for James Webb Space Telescope and the upcoming WEAVE-StePS survey. The Fellow is contributing to the definition of the science goals of new instruments (MOS/MOSAIC@E-ELT, SHARKS@LBT, MAORY/MICADO@E-ELT). The CIG has allowed the Fellow to consolidate the research on galaxy stellar populations as staff member at the host institution (also through the postdoctoral support to a researcher, now staff member) and to develop spin-off international collaborations. Dissemination has been done through 9 international and 2 national conferences, 7 international collaboration meetings, 2 invited colloquia, teaching to PhD students and guided visits to schools at the Observatory.

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