The VVV-SkZ pipeline: an automatic PSF-fitting photometric pipeline for the VVV survey

We present the VVV-SkZ_pipeline, a DAOPHOT-based photometric pipeline, created to perform PSF-fitting photometry of "VISTA Variables in the Vía Láctea" (VVV) ESO Public Survey data. The pipeline replaces the user avoiding repetitive interaction in all the operations, retaining all of the benefits of the power and accuracy of the DAOPHOT suite. The pipeline provides an astrometrized photometric catalog reliable up to more than 2 magnitudes brighter than the saturation limit, where other techniques fail. It also produces deeper and more accurate photometry. These achievements allow the VVV-SkZ_pipeline to produce data well anchored to the selected standard photometric system and analyze important phenomena (i.e. TRGB, RGB slope, HB morphology, RR Lyrae), that other methods are not able to manage.