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This paper describes a new determination of the primordial helium abundance (YP), based on the abundance analysis of five metal-poor extragalactic H II regions. For three regions of the sample (SBS 0335-052, I Zw 18, and H29) we present tailored photoionization models based on improved calculations with respect to previous models. In particular, we

We use deep 70, 100 and 160 μm observations taken with PACS, the Photodetector Array Camera and Spectrometer on board of Herschel, as part of the PACS Evolutionary Probe (PEP) guaranteed time, to study the relation between star formation rate and environment at redshift ~ 1 in the GOODS-S and GOODS-N fields. We use the SDSS spectroscopic catalog to

We have explored the effect of transition timescales in planetary nebulae (PNe) formation. We have performed hydrodynamical simulations of the evolution of the stellar winds predicted by theoretical stellar evolutionary models adopting two choices for the evolution during the transition time. The evolution of the star from the AGB to the PN stage

Upcoming weak lensing surveys, such as LSST, EUCLID and WFIRST, aim to measure the matter power spectrum with unprecedented accuracy. In order to fully exploit these observations, models are needed that, given a set of cosmological parameters, can predict the non-linear matter power spectrum at the level of 1 per cent or better for scales

The ancient Egyptians had just one calendar in operation, the civil one, during most of their history and before the overwhelming influence of Hellenic culture. This calendar may have been invented for a specific purpose in the first half of the third millennium B.C., when the previous local Nile-based lunar calendars were rendered useless, as the