Event Horizon Telescope observations of the jet launching and collimation in Centaurus A: Calibrated Data
Authors: Janssen et al.
Date: July 19th, 2021
Primary Reference: Janssen et al. 2021, Nat Astron, Volume 5
Data Product Code: 2021-D03-01
Brief Description:
We release a data set to accompany the Event Horizon Telescope observations
of the jet launching and collimation in Centaurus A paper (Janssen et al. 2021).
These data are the calibrated visibilities from the Event Horizon Telescope
observations of Centaurus A from April 10, 2017 (day of year 100) for both
low and high bands, centred around 227.1 GHz and 229.1 GHz, respectively.
Data from the 2017 observations were processed through three independent
reduction pipelines (Blackburn et al. 2019, Janssen et al. 2019,
EHTC et al. 2019). This release includes the fringe fitted, a-priori calibrated,
and network calibrated casa and hops data from the rPICARD and EHT-HOPS
pipelines, respectively. Independent flux calibration is performed based on
estimated station sensitivities 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 EHTC et al. (2019) 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 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 |
| SP | South Pole Telescope | South Pole |
References:
- EHT Collaboration Data Portal Website
- EHTC et al. 2019, ApJL, 875, L3
- Blackburn, L., Chan, C.-k., Crew, G., et al. 2019, ApJ, 882, 23
- Janssen, M., Goddi, C., van Bemmel, I., et al. 2019, A&A, 626, A75
- 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