Hi-GAL: the Herschel infrared Galactic Plane Survey
  Hi-GAL, the Herschel infrared Galactic Plane Survey, is an Open Time Key
Project of the Herschel Space Observatory. It will make an unbiased photometric
survey of the inner Galactic Plane by mapping a two-degree wide strip in the
longitude range |l|<60 degrees in five wavebands between 70um and 500um. The
aim of Hi-GAL is to detect the earliest phases of the formation of molecular
clouds and high-mass stars and to use the optimum combination of Herschel
wavelength coverage, sensitivity, mapping strategy and speed to deliver a
homogeneous census of star-forming regions and cold structures in the
interstellar medium. The resulting representative samples will yield the
variation of source temperature, luminosity, mass and age in a wide range of
Galactic environments at all scales from massive YSOs in protoclusters to
entire spiral arms, providing an evolutionary sequence for the formation of
intermediate and high-mass stars. This information is essential to the
formulation of a predictive global model of the role of environment and
feedback in regulating the star-formation process. Such a model is vital to
understanding star formation on galactic scales and in the early Universe.
Hi-GAL will also provide a science legacy for decades to come with incalculable
potential for systematic and serendipitous science in a wide range of
astronomical fields, enabling the optimum use of future major facilities such
as JWST and ALMA.
