UV slope, dust extinction and corrected star formation rate
density of z~4 Lyman break galaxies 

Study of the dust extinction in high-redshift galaxies is fundamental to obtaining an 
estimate of the corrected star formation rate density (SFRD) and to put constraints on galaxy
 evolution models. To this aim we have defined a new approach to the selection of 
Lyman Break Galaxies and to the characterisation of their UV reddening thanks to deep 
near-IR data from WFC3-HST. I will present the analysis of a sample of z~4 LBGs in the ERS 
and HUDF fields over GOODS-South and the distribution of their UV 
continuum slopes as a function of magnitude, suggesting a very low dust extinction for both 
bright and faint objects. I will present a revised estimate of dust-corrected SFRD at z~4, 
which takes into account the probability distribution of UV extinction values at different 
magnitudes, and discuss how extinction varies as a function of star formation rate. Finally, I will 
present our ongoing efforts to expand this work to other redshift ranges by defining a set of robust optical-IR LBG color 
selection criteria.


Water in proto-stellar outflows with Herschel


Water is a unique and crucial molecule for understanding the physical and
chemical conditions of proto-stellar environments. It is one of the main
coolants of the shocked gas and is very sensitive to local conditions, due to
its large abundance variations. The 'Water In Star-forming regions with
Herschel' (WISH) key program 
has carried out the first systematic study of the
H2O emission from nearby 
star-forming regions. The aim is to study the
physical and chemical 
properties of young stellar objects using water and to
follow the water abundance from collapsing clouds to 
planet-forming disks.
As part of the WISH (Water In Star-forming regions with Herschel) key project,
we observed different shock regions in young proto-stellar systems in a set of
H2O lines, together with several transitions of CO, OH and [OI].
I will present the results of this line survey concerning the water 
excitation and abundance. I will show the complexity of the water line profiles and how
water traces a gas very different from that probed by standard jet tracers
(SiO and low-J CO).