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Duties

Instrument Scientist for OMEGACAM at VST.

Instrument Scientist for VIMOS at UT3@VLT.

Prior Instrument Scientist for HAWK-I at UT4@VLT.

Scientific Interests

The stellar initial mass function of the Arches cluster.

After showing that the field of the LMC has an IMF with an upper mass slope consistent with the Salpeter one, we approached the other emblematic cluster for which a deviant value has been claimed. We have shown that the IMF slope in the upper mass range is also consitent with the Salpeter value. The details can be found in Espinoza, Selman and Melnick (2009), soon to appear in A\&A. You can see an ESO press release.

Scale free star cluster mass function and a universal stellar IMF in clusters and the field..

After having determined that the stellar population in the field and in the ionizing cluster of 30 Doradus both have a Salpeter slope IMF we have discussed the implications in the context of Kroupa and Weidner's arguments against the field IMF being the same as that of the IMF of stars in clusters. We presented our arguments in Protostars and Planets VI (Hawaii, 2005). We have refined the study since then, recognizing the significance of the statistics of the maximal star mass-cluster mass presented by Weidner and Kroupa by reproducing their results with our own simulations. The figure shows the contour map of this statistics showing the area permitted by the purely random sampling model but not covered by observations. We are using n-body simulations to determine the gravitational stability of the different parts of this diagram.

Intergalactic light in clusters of galaxies.

With Hernan Quintana from PUC and J. Melnick at ESO I have developed a technique to analyze imaging data in the optical in a manner analogous to that used in the infrared permitting accurate sky subtraction. The technical details are found in Melnick, Selman, and Quintana (1999). We are currently applying this technique to study the distribution of light in two clusters of galaxies. Preliminary results are presented in A&A 463, 833 (2007)

30 Doradus: star formation history and IMF.

With Jorge Melnick we have recently found that between 7 and 40 solar the stellar IMF in the field of the 30 Doradus superassociation has a Salpeter slope. Dor details see this paper.

With Jorge Melnick, Roberto Terlevich and Guillermo Bosch we have written a series of papers on the properties of the ionizing cluster of 30 Doradus. Paper I deals with the data analysis and the distribution of reddening; Paper II, written by Bosch et al. deals with the spectroscopic study of the massive stellar population; Paper III, by Selman et al. deals with the IMF and star formation history; and Paper IV, by Bosch et al. started as an attempt to study the dynamics of the cluster and ended being a study of the binary fraction.

Stellar Formation and Evolution.

In order to study environmental effects on the IMF, and the star-formation history as a function of position I am in the process of extending the work from the ionizing cluster of the Tarantula to the larger super-association area. The data consist on 4 WFI pointings. To compare with the previous work I show how a single WFI pointing looks compared with an NTT SUSI frame used in the previous study. You can look at the data from this frame, together with a few isochrones and the theoretical surface in this 3D color image of the color-color stereogram.

Fractals and self-organized criticality.

J. Melnick and I have published two papers on these issues; The first one deals with the fractal nature of the distribution of super-association sizes in galaxies and the second deals with self-organized criticality and star-formation.