Authors: The Event Horizon Telescope Collaboration et al.
Date: April 10, 2019
Primary Reference: The Event Horizon Telescope Collaboration, et al. 2019c, ApJL, 875, L3 (M87 Paper III)
Data Product Code: 2019-D01-01
Brief Description:
We release a data set to accompany the First M87 Event Horizon Telescope Results paper series (EHT Collaboration et al. 2019a,b,c,d,e,f). The data set is derived from the Science Release 1 (SR1) of the Event Horizon Telescope (EHT)'s April 2017 observation campaign (EHT Collaboration et al. 2019c). It is made public simultaneously with three imaging pipelines.
This data set contains M87 data for both low and high bands for all observed days (April 5th, 6th, 10th, 11th, 2017). Data from the 2017 observations were processed through three independent reduction pipelines (Blackburn et al. 2019, Janssen et al. 2019, Paper III). This release includes the fringe fitted, a-priori calibrated, and network calibrated data from the EHT-HOPS pipeline, which is the primary data set for the First M87 EHT results. Independent flux calibration is performed based on estimated station sensitvities during the campaign (Issaoun et al. 2017, Janssen et al. 2019). A description of the data properties, their validation, and estimated systematic errors is given in Paper III with additional details in Wielgus et al. (2019).
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.
All uvfits files are located in the "uvfits/" subdirectory. Easy-to-read
csv and txt files are derived from the uvfits files and provided in
"csv/" and "txt/", respectively. Scripts that generate these files from the
original SR1 data are also included. Finally, the run.sh script in the top
directory will convert uvfits files into csv and txt files.
The three tgz files are gzipped tarballs that contains uvfits, txt, and
csv files, respectively. They are included in this repository for convenience.
File Name Convention:
The data files are named in the following convention:
[Data-Release-Tag]_[Source]_[year]_[day-of-year]_[band]_[pipeline]_[stage]_StokesI.[format]
Station Code Table:
| UVFITS Code | Station Name | Location |
|---|---|---|
| AA | ALMA | Chile |
| AP | APEX | Chile |
| AZ | Submillimeter Telescope | Arizona |
| JC | James Clerk Maxwell Telescope | Hawai'i |
| LM | Large Millimeter Telescope | Mexico |
| PV | IRAM | Spain |
| SM | Submillimeter Array | Hawai'i |
References:
- EHT Collaboration Data Portal Website
- The Event Horizon Telescope Collaboration, et al. 2019a, ApJL, 875, L1 (M87 Paper I)
- The Event Horizon Telescope Collaboration, et al. 2019b, ApJL, 875, L2 (M87 Paper II)
- The Event Horizon Telescope Collaboration, et al. 2019c, ApJL, 875, L3 (M87 Paper III)
- The Event Horizon Telescope Collaboration, et al. 2019d, ApJL, 875, L4 (M87 Paper IV)
- The Event Horizon Telescope Collaboration, et al. 2019e, ApJL, 875, L5 (M87 Paper V)
- The Event Horizon Telescope Collaboration, et al. 2019f, ApJL, 875, L6 (M87 Paper VI)
- Blackburn, L., Chan, C.-k., Crew, G., et al. 2019, arXiv:1903.08832
- Janssen, M., Goddi, C., van Bemmel, I., et al. 2019, arXiv:1902.01749
- Issaoun, S., Folkers, T., Blackburn, L., et al. 2017, EHT Memo 2017-CE-02
- Janssen, M., Blackburn, L., Issaoun, S., et al. 2019, EHT Memo 2019-CE-01
- Wielgus, M., Blackburn, L., Issaoun, S., et al. 2019, EHT Memo 2019-CE-02