The Pierre Auger Observatory publishes 10% of the data recorded using the world's largest cosmic ray detector. This data is made public for use by a broad and diverse community, including professional and amateur researchers, for research, education and outreach initiatives.
The Pierre Auger Collaboration has been making data collected in a similar manner available to the general public for more than a decade, but the current way of publishing is much more efficient in terms of the quality and type of data, making it usable for both educational purposes and scientific research. The data can be accessed at: www.auger.org/opendata [1]
The operation of the Pierre Auger Observatory by a collaboration of about 400 scientists from over 90 institutions in 18 countries around the world has led to the determination of the properties of cosmic rays at the highest energies and with unprecedented precision. These cosmic particles are predominantly nuclei of ordinary elements that reach Earth from astrophysical sources. Data from the Observatory have been used to demonstrate that the highest energy particles are of extragalactic origin. The energy spectrum of the measured cosmic rays exceeds 1020 eV which corresponds to a macroscopic value of about 16 Joules for a single particle. It has been shown that there is a sharp decrease in the particle flux at high energies and there is preliminary evidence of emission from specific nearby sources. Data analyses have allowed the characterization of the type of particles with such remarkable energies, which include elements from hydrogen to silicon. The data can also be used to test particle physics at energies above those obtained at the LHC.
At the Pierre Auger Hybrid Observatory [2], located in Argentina, cosmic radiation is observed indirectly, through the beams of secondary particles produced by the interaction of the incident primary particle with the atmosphere. Detectorul de Suprafață a Observatorului acoperă o arie de 3000 km2 and is made up of a network of individual particle detectors placed at a distance of 1500 m from each other. The entire Observatory is framed by the telescopes that make up Detectorul de Fluorescență, sensitive to the fluorescent light, similar to auroras, emitted as atmospheric jets develop. Detectorul de Suprafață is sensitive to muons, electrons, and photons reaching the ground level. Data from the Observatory include raw data (obtained directly from these instruments), reconstructed data sets generated by detailed analyses, and data presented in scientific publications. Some data are routinely shared with other observatories to allow analyses using multiple experiments that thus cover the entire sky and to facilitate multi-messenger studies.
As collaboration spokesperson Ralph Engel emphasized, “the data from the Pierre Auger Observatory, which was established more than 20 years ago, are the result of a large and long-term scientific, human and financial investment by a very large international collaboration” and are of remarkable value to the scientific community worldwide. By publishing the data and analysis programs, the Auger Collaboration embraces the principle that open access to the data will allow, in the long term, the maximum exploitation of their scientific potential.
The Auger Collaboration adopted a 4-level classification of data complexity, relative to those used in high-energy physics, and adapted it to its open public access policy.
(Level 1) Open access publications with additional numerical data provided to facilitate their re-use [3];
(Level 2) Periodic publication of data in a simplified format for education and outreach. This began in 2007 when 1% of the data was published, a percentage that increased to 10% in 2019 [4];
(Level 3) Publication of data reconstructing cosmic ray events, obtained with the best available knowledge of detector performance and conditions at the time of data recording. Examples of codes derived from those used by the Collaboration for publishing analyses are also provided [5];
(Level 4) Publishing of raw data associated with recorded events. An event display browser and data reading codes are also available [6].
The latest layers of information added now [1] include data from two major instruments of the Observatory: the Surface Detector located at 1500 m2 and the Fluorescence Detector. The dataset consists of 10% of all events recorded at the Observatory, subjected to the same selection and reconstruction procedures used by the Collaboration in recent publications. The data recording periods are the same as those used to obtain the scientific results presented at the International Cosmic Radiation Conference held in 2019. The example analyses use updated versions of Auger datasets, which differ slightly from those used for publications due to subsequent improvements in reconstruction and calibration. On the other hand, as the percentage of data currently publicly available is 10% of the Auger database, the statistical significance of the measured quantities is reduced, relative to what can be obtained with a complete database, but the number of events is comparable to that used in some of the first scientific publications of the Pierre Auger Collaboration.
The Pierre Auger collaboration wishes to continue its policy of making experimental data public for the purpose of access to a wide and diverse public, to increase the common scientific potential in the future.