Hierarchical Progressive Survey (HiPS) format: Moving from visualisation to scientific analysis

¹ Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
² Serco for the European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
³ Centro de Investigación Avanzada en Física Fundamental (CIAFF-UAM), 28049 Madrid, Spain
⁴ International Centre for Radio Astronomy Research, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009, Australia
⁵ Telespazio UK for European Space Agency, ESAC, Camino Bajo del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain
⁶ European Space Astronomy Centre (ESAC) Science Data Centre, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain

^★ Corresponding author: fabriziogiordano77@gmail.com

Received: 20 April 2025
Accepted: 5 September 2025

Abstract

Context. In the current era of multi-wavelength and multi-messenger astronomy, international organisations are actively working on the definition of new standards for the publication of astronomical data, and substantial effort is being devoted to making them available through public archives.

Aims. We present a set of tools that allow user-friendly access and the basic scientific analysis of observations in the Hierarchical Progressive Survey (HiPS) format, and we use them to gauge the quality of representative skymaps at ultraviolet, optical, and infrared wavelengths.

Methods. We apply a fully automatic procedure to derive aperture photometry in ten different bands for the 323 nearby galaxies in the Herschel Reference Sample (HRS), and compare its results with the rigorous analyses involving specialised knowledge and human intervention carried out by the HRS team.

Results. Our experiment shows that nine of the ten skymaps considered preserve the original quality of the data, and the photometric fluxes returned by our pipeline are consistent with the HRS measurements within a few percent. In the case of Herschel PACS maps at 100 μm, we uncovered a systematic error that we ascribe to an inconsistent combination of data products with different spatial resolutions. For the remaining skymaps, the estimated statistical uncertainties provide a realistic indication of the differences with respect to the HRS catalogue.

Conclusions. In principle, the currently available HiPS skymaps in the Flexible Image Transport System (FITS) format allow one to carry out broadband photometric analyses with an accuracy of the order of a few percent, but some level of human intervention is still required. In addition to assessing data quality, we also propose a series of recommendations to realise the full potential of the HiPS format for the scientific analysis of large astronomical datasets.