Patrones de edad en una muestra de galaxias espirales

The Halpha-toFUV flux ratio in a young star forming regions is an age sensitive quantify. If this quantify is measured for each pixel in an image of a face-on galaxy, it is possible to map the ages of star forming regions across the disk. To do this we compare the new release GALEX FUV images and extremely narrowband TTF Halpha images of a sample of nearby face-on spirals galaxies, using a pixel-to- pixel comparison method.

The evolutionary synthesis model Starburst99 (Leitherer et al. 1999), SB99, describes the predicted decline of Halpha-to-FUV flux ratio with the age of a star forming region. The evolution of the flux ratio is modelled with the Salpeter IMF, 6% escape fraction and solar metallicity. The flux ratio found from the images is scaled to the SB99 model assuming an approximately zero age for the youngest regions. In this way, an age is assigned to each pixel, binned into either 0-4 Myrs, 4-6 Myrs, 6-9 Myrs and >9 Myrs. The resulting age maps show the newest star forming regions tracing the spiral arms in the galaxies of our sample.