SYMBA: An end-to-end VLBI synthetic data generation pipeline (2004.01161v1)

Abstract: Realistic synthetic observations of theoretical source models are essential for our understanding of real observational data. In using synthetic data, one can verify the extent to which source parameters can be recovered and evaluate how various data corruption effects can be calibrated. These studies are important when proposing observations of new sources, in the characterization of the capabilities of new or upgraded instruments, and when verifying model-based theoretical predictions in a comparison with observational data. We present the SYnthetic Measurement creator for long Baseline Arrays (SYMBA), a novel synthetic data generation pipeline for Very Long Baseline Interferometry (VLBI) observations. SYMBA takes into account several realistic atmospheric, instrumental, and calibration effects. We used SYMBA to create synthetic observations for the Event Horizon Telescope (EHT), a mm VLBI array, which has recently captured the first image of a black hole shadow. After testing SYMBA with simple source and corruption models, we study the importance of including all corruption and calibration effects. Based on two example general relativistic magnetohydrodynamics (GRMHD) model images of M87, we performed case studies to assess the attainable image quality with the current and future EHT array for different weather conditions. The results show that the effects of atmospheric and instrumental corruptions on the measured visibilities are significant. Despite these effects, we demonstrate how the overall structure of the input models can be recovered robustly after performing calibration steps. With the planned addition of new stations to the EHT array, images could be reconstructed with higher angular resolution and dynamic range. In our case study, these improvements allowed for a distinction between a thermal and a non-thermal GRMHD model based on salient features in reconstructed images.

• The paper introduces a comprehensive VLBI synthetic data pipeline that integrates atmospheric, instrumental, and calibration effects beyond traditional thermal noise.
• It applies the pipeline to generate realistic EHT observations of M87, enhancing black hole imaging through precise simulation of varying observational conditions.
• The study demonstrates that realistic synthetic data aids in testing future VLBI array enhancements and validating competing astrophysical models.

SYMBA: An End-to-End VLBI Synthetic Data Generation Pipeline

The paper presents SYMBA, an innovative framework designed to generate realistic synthetic data for Very Long Baseline Interferometry (VLBI) observations. This paper focuses on simulating observations for the Event Horizon Telescope (EHT), particularly aimed at the galaxy M87. SYMBA provides a comprehensive pipeline for synthetic data creation, simulating various observational and instrumental effects that can impact the data from VLBI arrays.

The addition of synthetic data is critical for testing the capabilities of evolving or new instruments, verifying theoretical models through direct observation, and ensuring effective calibration of various data corruption effects. SYMBA broadens conventional synthetic data simulations by incorporating realistic atmospheric influences, instrumental effects, and calibration errors that are often overlooked.

Key Contributions

1. Comprehensive Simulation Pipeline:
   • SYMBA stands out by integrating multiple layers of corruption and calibration into synthetic data, making it more reflective of real-world observations.
   • Atmosphere, instrumental, and calibration errors are simulated, going beyond the traditional inclusion of only thermal noise.
2. Application to Event Horizon Telescope (EHT):
   • The pipeline facilitates the simulation of data as would be captured by the EHT array, particularly the 2017 array's observations of M87. The authors discuss the significance of these simulations in imaging the black hole's shadow in M87, reinforcing the pipeline's practical application.
3. Pipeline for Testing Future EHT Arrays:
   • SYMBA considers observational scenarios with potential expansions to the EHT array, such as the inclusion of new stations.
   • The synthetic data generated under varying weather conditions and differing array configurations enables adaptive testing of strategies that optimize scientific output.
4. Comparative Model Analysis Through Imaging:
   • Using general relativistic magnetohydrodynamics (GRMHD) models for testing, SYMBA allows distinct visualization of model-specific features, such as jet structures, highlighting its utility in distinguishing between competing theoretical models.

Implications and Future Work

The research underscores the importance of including complex corruption and calibration effects to more precisely reconstruct observed source models. The results indicate that with additional stations considered for the EHT array, distinguishing between theoretical models based on observational data could improve significantly. This capability is not only limited to current models but can also crucially inform the design and development of future observational campaigns.

Looking forward, the potential expansion of this pipeline includes applying it to different VLBI arrays across various wavelengths, and incorporating time-variable and polarized source models. The paper also lays groundwork for future computational analysis to fit source models to observed data with higher precision, extending its utility within the astrophysical community.

The insights gained from SYMBA's application are poised to enhance our understanding of black hole physics and the observational paper of extreme environments. The holistic approach to synthetic data generation presented in this paper serves as a robust model for future astrophysical and cosmological investigations.