LOTSS DR2 - Where to find the data

User Interfaces

The LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) Data Release 2 (LoTSS DR2) is hosted on the SURF Data Repository, and exposed to the community through the standard Virtual Observatory protocols. This section describes how the LoTSS DR2 data products can be queried and accessed by using different applications.

Introduction

The science-ready data products as described in Available data products are exposed through standard Virtual Observatory (VO) protocols to facilitate their access and exploration. You can find an introduction to the usage of the VO on this page. In the following we will be refering to several VO standards (SIA, DataLink, etc.) which are all discussed in the VO documentation.

The LoTSS DR2 data itself is hosted on the SURF Data Repository (sdr) system. Also the raw observations from which the survey data has been derived are accessible through the Lofar Long-Term Archvie. The main data products (images) are all directly accessible through the VO (either through the Simple Image Access, or via DataLinks to auxiliary data products). The raw data is stored on tape, which means that they need to be put on disk for access. This process is refered to as "staging". The DataLink entries to the files on tape all point to the page of the sdr which lists all the data from a specific pointing. An example of such a page is shown in Fig. 1. This page shows all data that is directly downloadable (with the status "online" or "external), data that is in the process of being staged (with the status "staging") or data that needs to be staged (with the status "offline").

To obtain more information about a file, you can click on the small arrow next to it. This will show a description (the same as is used in the DataLink), a persistent identifier that can be used to cite the data product itself when used in a publication, and a checksum (of the Adler32 format) that one could use to check the integrity of a downloaded product. To stage the data, you can click the "Request" button next to the "offline" status field. After confirming, a request will be made to copy the data from tape to disk where it will remain for a while for users to download it. This workflow is illustrated in Fig. 2.

Data access

The tables of mosaics and sources can be found in the ASTRON Virtual Observatory.
The entry of LoTSS DR2 in the SURF Data Repository.
Also you can see the HiPS  of the high-resolution (primary data products) and low-resolution data.

More information can be found on the LOFAR surveys webpage and in:

Shimwell, T.W., et al. “The LOFAR Two-metre Sky Survey (LoTSS). V. Second data release" accepted for publication in Astronomy & Astrophysics, DOI 10.1051/0004-6361/202142484.

Data usage policy

Papers making use of LOFAR data should follow the LOFAR Data Policy.

This states that papers making use of this data should include the following acknowledgement:

This paper is based (in part) on data obtained with the International LOFAR Telescope (ILT). LOFAR (van Haarlem et al. 2013) is the Low Frequency Array designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris –PSL and Université d'Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland; The Istituto Nazionale di Astrofisica (INAF), Italy.

In addition, they should include the LoTSS DR2 PID: 21.12136/95f9f5a9-406e-4270-ad8b-45e36c809561 and cite the survey paper: Shimwell, T.W., et al. “The LOFAR Two-metre Sky Survey (LoTSS). V. Second data release" accepted for publication in Astronomy & Astrophysics, DOI 10.1051/0004-6361/202142484.