First M87 EHT Results: Imaging Pipelines

Authors: The Event Horizon Telescope Collaboration et al.

Date: April 10, 2019

Primary Reference: The Event Horizon Telescope Collaboration, et al. 2019d, ApJL, 875, L4 (M87 Paper IV)

Data Product Code: 2019-D01-02

Brief Description:

We release three imaging pipelines (DIFMAP, eht-imaging and SMILI) used in the parameter survey of M87 Paper IV Section 6 and later. All imaging pipelines create images from calibrated uvfits files (see M87 Paper III) simultaneously released (data product code: 2019-D01-01). For more detailed instructions, please see the README file in the sub-directory for each pipeline.

We note that, as described in 2019-D01-01, released visibility data sets have only Stokes I, which are slightly different from data sets used in Paper IV that have dual polarization at Stokes RR and LL. This slight difference in released data sets will provide no net changes in DIFMAP and eht-imaging pipelines, while it will change self-calibration procedures slightly for SMILI calibrating R and L gains separately for the latter dual polarization data sets. We confirm that reconstructed images are consistent with images presented in Paper IV on fiducial parameters (see Paper IV Section 6) for all three pipelines, and will not affect our conclusions in the M87 publications (Paper I, II, III, IV, V and VI).

Notes:

These data files only include Stokes I visibilities, while the published results used data files from the full SR1 release which include Stokes RR and LL. The slight difference in the underlying data from the conversion to Stokes I in the single-precision *.uvfits files, as well as differences in the python dependencies used by eht-imaging and SMILI (e.g. numpy, astropy, scipy), may slightly affect the final image.

References:

mgjeon/2019-D01-02

First M87 EHT Results: Imaging Pipelines