First Sagittarius A* EHT Results: Calibrated Data

We release a data set to accompany the First Sagittarius A* Event Horizon Telescope Results paper series (EHT Collaboration et al. 2022a,b,c,d,e,f). The data set is derived from the Rev7 Correlation of the Event Horizon Telescope (EHT)'s April 2017 observation campaign (EHT Collaboration et al. 2019c), with further processing and science validation as described in EHT Collaboration et al. 2022b. It is made public simultaneously with four imaging pipelines (2022-D02-02, EHT Collaboration et al. 2022c). This data set contains Sagittarius A* (Sgr A*) data for both low and high bands for two observed days (April 6th and 7th, 2017). Data from the 2017 observations were processed through three independent reduction pipelines (Blackburn et al. 2019, Janssen et al. 2019, M87 Paper III, and Sgr A* Paper II, Paper III). This release includes the fringe fitted, a-priori calibrated, and network calibrated data from both the EHT-HOPS and rPICARD (CASA) pipelines, which are used in the First Sgr A* EHT results. Independent flux calibration is performed based on estimated station sensitvities during the campaign (Issaoun et al. 2017, Janssen et al. 2019, Wielgus et al. 2022). A description of the data properties, their validation, and estimated systematic errors is given in M87 Paper III and Sgr A* Paper II and Paper III with additional details in Wielgus et al. (2019) and Wielgus et al. (2022). The data are time averaged to 10 seconds and frequency averaged over all 32 intermediate frequencies (IFs). All polarization information is explicitly removed. To make the resulting uvfits files compatible with popular very-long-baseline interferometry (VLBI) software packages, the circularly polarized cross-hand visibilities RL and LR are set to zero along with their errors, while parallel-hands RR and LL are both set to an estimated Stokes I value. Measurement errors for RR and LL are each set to sqrt(2) times the statistical errors for Stokes I.