Convection and turbulence in stellar atmospheres have a significant effect on the emergent flux from late-type stars. The theoretical advancements in convection modelling over recent years have proved challenging for the observers to obtain measurements with sufficient precision and accuracy to allow discrimination between the various predictions. An overview of the current observational techni...

We describe TRILEGAL, a new populations synthesis code for simulating the stellar photometry of any Galaxy field. The code attempts to improve upon several technical aspects of star count models, by: dealing with very complete input libraries of evolutionary tracks; using a stellar spectral library to simulate the photometry in virtually any broad-band system; being very versatile allowing easy...

Context. The stellar populations in the outer Galactic disk are nowadays a subject of wide interest. To contribute to a better picture of this part of the Galaxy, we have studied the nature of five marginally investigated star clusters (Collinder 74, Berkeley 27, Haffner 8, NGC 2509, and VdB-Hagen4) by means of accurate CCD photometry in the V and I pass-bands. These clusters are in fact locate...

We present new BVI ground-based photometry and VI space-based photometry for the globular cluster M92 (NGC 6341) and examine luminosity functions in B, V, and I containing over 50,000 stars ranging from the tip of the red giant branch to several magnitudes below the main sequence turn off. Once corrected for completeness, the observed luminosity functions agree very well with theoretical models...

We have used a large sample of low-inclination spiral galaxies with radially-resolved optical and near-infrared photometry to investigate trends in star formation history with radius as a function of galaxy structural parameters. A maximum likelihood method was used to match all the available photometry of our sample to the colours predicted by stellar population synthesis models. The use of si...

We report the discovery of a new ultra-faint globular cluster in the constellation of Ursa Minor, based on stellar photometry from the MegaCam imager at the Canada-France-Hawaii Telescope (CFHT). We find that this cluster, Muñoz 1, is located at a distance of 45± 5 kpc and at a projected distance of only 45 from the center of the Ursa Minor dSph galaxy. Using a Maximum Likelihood technique we m...

The key features of the MATPHOT algorithm for precise and accurate stellar photometry and astrometry using discrete Point Spread Functions are described. A discrete Point Spread Function (PSF) is a sampled version of a continuous PSF which describes the two-dimensional probability distribution of photons from a point source (star) just above the detector. The shape information about the photon ...

We use a robust sample of 11 z ∼ 7 galaxies (z850-dropouts) to estimate the stellar mass density of the universe when it was only ∼750 Myr old. We combine the very deep optical to near-Infrared photometry from the HST ACS and NICMOS cameras with mid-Infrared Spitzer IRAC imaging available through the GOODS program. After carefully removing the flux from contaminating foreground sources we have ...