As a part of the UCM Star Formation Group (SFG), my research activity is focused on the detailed study of the formation and evolution of galaxies along the lifetime of the Universe.

In my PhD thesis, presented in June 2003, I compiled broad- and narrow-band optical and near-infrared data for the 191 galaxies in the UCM Survey. The UCM Survey selected by their Hα emission a representative sample of star-forming galaxies in the local Universe. This sample has been used extensively as a the local benchmark for studies of galaxies at intermediate and high redshift (see, e.g., Gallego et al. 1995).

With the complete dataset for the UCM galaxies, I studied the main properties of the stellar populations in the local star-forming galaxies and the global properties of the star formation in the local Universe. For that purpose, we developed a code for stellar population synthesis studies. This code combines the emission from stars (with the possibility of including different populations with different properties) and gas and compares the models with the observed data using a Bayesian technique that provides the most probable values of properties such as the age of the stellar population, the metallicity, or the stellar mass.

Some of the main results in my thesis are shown in the figure below. The star formation in the local Universe is concentrated in galaxies with a typical stellar mass of 1010 ℳ⊙ and a specific SFR of 100-1000 yr-1. There are 2 main categories among the local star-forming galaxies: 1) some massive galaxies with enhanced star formation in their disks (probably linked to interactions with other galaxies), which typically harbor star formation bursts with high metallicities and low ionizations (filled black symbols in the figure); and 2) less massive galaxies with more intense bursts which typically present low metallicities and high ionization estates (open black symbols in the figure). The former type, known as disk-like star-forming galaxies, are closer to normal quiescent spiral galaxies (for example, the ones in Kennicutt 1983 sample, shown as green triangles). The other type of local star-forming galaxies are known as HII-like objects, and they are closer to some of the objects in the Universe with the most violent star formation, such as HII galaxies (Telles 1995; cyan crosses) or UV-bright starbursts (Calzetti 1997; blue rectangles).

This is another figure from my thesis, which shows Hα images of 4 UCM Survey galaxies. In Jesús Gallego's thesis (1995), long-slit spectra were obtained for all the UCM sample (see also Gallego et al. 1996). For my thesis, we obtained narrow-band Hα images for a representative subsample of UCM galaxies to measure how much star formation for each galaxy was not detected by the long slits. In the figure below, we show the positions of the lon-slits used by Gallego et al. 1996. Our results indicate that typically 50% to 70% of the total Hα flux of a UCM galaxy is extended, so it falls out of a long-slit. Using this correction, we re-estimated the cosmic SFR density at z=0 (Pérez-González et al. 2003), obtaining a value of 0.029+0.008-0.005 ℳ⊙ yr-1Mpc-3 for a cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and Λ = 0.7 (for comparison, Gallego et al. 1995 obtained a value of 0.021 ℳ⊙ yr-1Mpc-3 for the same cosmology).

You can find more information about my thesis work and the UCM Survey in my publications from 1999 to 2003, and all the publications of the UCM Star Formation Group (SFG)