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HELP: The Herschel Extragalactic Legacy Project

Shirley, R., Duncan, K., Camops Varillas, M. C., Hurley, P. D., Małek, K., Roehlly, Y., Smith, M. W. L. ORCID:, Aussel, H., Bakx, T., Buat, V., Burgarella, D., Christopher, N., Duivenvoorden, S., Eales, S. ORCID:, Efstathiou, A., Gonźalez Solares, E. A., Griffin, M. ORCID:, Jarvis, M., Lo Faro, B., Marchetti, L., McCheyne, I., Papadopoulos, A., Penner, K., Pons, E., Prescott, M., Rigby, E., Rottgering, H., Saxena, A., Scudder, J., Vaccari, M., Wang, L. and Oliver, S. J. 2021. HELP: The Herschel Extragalactic Legacy Project. Monthly Notices of the Royal Astronomical Society 507 (1) , pp. 129-155.

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We present the Herschel Extragalactic Legacy Project (HELP). This project collates, curates, homogenises, and creates derived data products for most of the premium multi-wavelength extragalactic data sets. The sky boundaries for the first data release cover 1270 deg2 defined by the Herschel SPIRE extragalactic survey fields; notably the Herschel Multi-tiered Extragalactic Survey (HerMES) and the Herschel Atlas survey (H-ATLAS). Here, we describe the motivation and principal elements in the design of the project. Guiding principles are transparent or “open” methodologies with care for reproducibility and identification of provenance. A key element of the design focuses around the homogenisation of calibration, meta data and the provision of information required to define the selection of the data for statistical analysis. We apply probabilistic methods that extract information directly from the images at long wavelengths, exploiting the prior information available at shorter wavelengths and providing full posterior distributions rather than maximum likelihood estimates and associated uncertainties as in traditional catalogues. With this project definition paper we provide full access to the first data release of HELP; Data Release 1 (DR1), including a monolithic map of the largest SPIRE extragalactic field at 385 deg2 and 18 million measurements of PACS and SPIRE fluxes. We also provide tools to access and analyse the full HELP database. This new data set includes far-infrared photometry, photometric redshifts, and derived physical properties estimated from modelling the spectral energy distributions over the full HELP sky. All the software and data presented is publicly available.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Additional Information: This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
Publisher: Royal Astronomical Society
ISSN: 1365-2966
Date of First Compliant Deposit: 2 July 2021
Date of Acceptance: 20 May 2021
Last Modified: 04 May 2023 02:10

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