A Cosmic Census of the Galaxies in the Distant Universe

Description and aim

Understanding the evolution of galaxies across cosmic time is one of the great challenges of astrophysics. Current observations and theories have significant uncertainties in e.g. the feedback processes that influence star formation and the way in which the demographics of galaxy populations and their evolution depend on their environments. To make progress, we need to map well-defined samples of galaxies in statistically representative range of environments using telescopes that probe different physical processes. These observations provide statistical constraints on models of galaxy formation in which the star-formation, stellar mass and accretion activity in galaxies of galaxies are tied to the history of the dark matter halos in which they reside.  Rare populations of galaxies also provide sensitive tests of the extremes of such models.

To address these topics many ambitious survey programs (covering a few, tens, hundreds or thousands plus square degrees) have recently been carried out, or are currently underway, at the major astronomical observatories, e.g. VISTA, LOFAR, Herschel etc. The Herschel Extragalactic Legacy Project (HELP), funded by the European Commission Research Executive Agency, aims to “help" by bringing together these various projects. 

The foundation of HELP is 1300 deg2 of data from the European Space Agency's (ESA) Herschel space mission. Exploration of the star formation history of the universe, using extragalactic surveys, was a major goal of the Herschel mission.  By combining the data from many observatories, utilizing advanced statistical techniques and developing new tools HELP intends to overcome the limits of Herschel resolution and enable astronomers in Europe to realize Herschel’s full potential.  

HELP will create a multi-wavelength, homogenous, photometric resource covering ~1300 deg2, with added-value in the form of photometric redshifts and physical modeling of e.g. stellar mass, dust masses and star-formation rates.

Our workshop is timed for the midpoint of the HELP project. It will bring together for the first time the European scientists who are expected to be key beneficiaries of HELP, with members of the international multi-wavelength survey teams (including LOFAR) and the core HELP team.  Through direct interaction between the HELP team and the users, the science exploitation can begin in earnest and HELP can get feedback and make adjustments to future direction of project so that final data products and tools have the greatest legacy value possible and thus provide the key tools and data products to enable European astronomers to understand the growth of galaxies across the history of the Universe.

The key objectives are to:

·         Explore the scientific questions that these multi-wavelength datasets seek to address;

·         Review the available, ongoing and planned datasets and assess the needs for new observations;

·         Assess the progress on the technical challenges e.g. in photometric redshifts, dealing with selection functions and resolving the Herschel confusion challenge ;

·         Compare and asses the methods for modelling the intrinsic physical properties of galaxies from their observed photometric properties.

·         Critically assess the tools and delivery of data to best meet the needs of the community in addressing the scientific questions.