Multiobjective optimization for scattering mitigation and scattering screen reconstruction in very long baseline interferometry observations of the Galactic Center

¹ Dipartimento di Fisica, Università degli Studi di Cagliari, SP Monserrato-Sestu km 0.7, 09042 Monserrato, Italy
² INAF-Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
³ SCOPIA Research Group, University of the Balearic Islands, Dpt. of Mathematics and Computer Science, Crta. Valldemossa, Km 7.5, Palma 07122, Spain
⁴ Health Research Institute of the Balearic Islands (IdISBa), Palma 07122, Spain
⁵ Artificial Intelligence Research Institute of the Balearic Islands (IAIB), Palma 07122, Spain
⁶ Instituto de Astrofísica de Andalucía CSIC, Apartado 3004, 18080 Granada, Spain
⁷ Jansky Fellow of National Radio Astronomy Observatory, 1011 Lopezville Rd, Socorro, NM 87801, USA
⁸ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn (Endenich), Germany
⁹ Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090, Brazil

^★ Corresponding author: alejandro.musmejias@unica.it

Received: 17 November 2024
Accepted: 22 April 2025

Abstract

Context. Imaging reconstruction of interferometric data is a hard and ill-posed inverse problem. Its difficulty is increased for observations of the Galactic Center, which is obscured by a scattering screen. This is because the scattering breaks the one-to-one correspondence between images and visibilities.

Aims. Solving the scattering problem is one of the greatest challenges in radio imaging of the Galactic Center. We present a novel strategy for mitigating its effect and for constraining the screen itself using multiobjective optimization.

Methods. We exploited the potential of evolutionary algorithms to describe the optimization landscape with the aim to recover the intrinsic source structure and the scattering screen that affects the data.

Results. We successfully recovered the screen and the source in a wide range of simulated cases, including the speed of a moving screen at 230 GHz. Particularly, we recovered a ring structure in scattered data at 86 GHz.

Conclusions. Our analysis demonstrates the huge potential that recent advancements in imaging and optimization algorithms offer in recovering image structures, even in weakly constrained, degenerated, and possibly multimodal settings. The successful reconstruction of the scattering screen opens the window to event-horizon scale works on the Galactic Center at 86 GHz up to 116 GHz and to the study of the scattering screen itself.