The 1.28 GHz MeerKAT Galactic Center Mosaic

Abstract: The inner $\sim$200 pc region of the Galaxy contains a 4 million M$_{\odot}$ supermassive black hole (SMBH), significant quantities of molecular gas, and star formation and cosmic ray energy densities that are roughly two orders of magnitude higher than the corresponding levels in the Galactic disk. At a distance of only 8.2 kpc, the region presents astronomers with a unique opportunity to study a diverse range of energetic astrophysical phenomena, from stellar objects in extreme environments, to the SMBH and star-formation driven feedback processes that are known to influence the evolution of galaxies as a whole. We present a new survey of the Galactic center conducted with the South African MeerKAT radio telescope. Radio imaging offers a view that is unaffected by the large quantities of dust that obscure the region at other wavelengths, and a scene of striking complexity is revealed. We produce total intensity and spectral index mosaics of the region from 20 pointings (144 hours on-target in total), covering 6.5 square degrees with an angular resolution of 4$"$,at a central frequency of 1.28 GHz. Many new features are revealed for the first time due to a combination of MeerKAT's high sensitivity, exceptional $u,v$-plane coverage, and geographical vantage point. We highlight some initial survey results, including new supernova remnant candidates, many new non-thermal filament complexes, and enhanced views of the Radio Arc Bubble, Sgr A and Sgr B regions. This project is a SARAO public legacy survey, and the image products are made available with this article.

• The paper presents a 6.5 sq. deg. mosaic using 144 hours of MeerKAT observations at 1.28 GHz, revealing unprecedented details of the Galactic center.
• It employs high-resolution imaging to identify new supernova remnants and diverse non-thermal filaments, enhancing our understanding of cosmic structures.
• The study refines spectral index analyses to differentiate thermal and non-thermal processes, setting a framework for future multi-wavelength research.

The 1.28 GHz MeerKAT Galactic Center Mosaic

The paper "The 1.28 GHz MeerKAT Galactic Center Mosaic" presents a comprehensive survey of the Milky Way's Galactic center conducted with the MeerKAT radio telescope. The study focuses on a 6.5 square degree area around the Galactic center, imaged at a central frequency of 1.28 GHz and an angular resolution of 4 inches. It covers a broad array of phenomena including supermassive black holes, supernova remnants, non-thermal filament complexes, and the intricacies of star formation within this energetic region. This document not only unlocks previously obscured details due to dust but introduces novel features owing to MeerKAT’s high sensitivity and cover.

Summary of Observations and Analysis

The survey was conducted using 20 pointings with a total of 144 hours on-target time. MeerKAT’s capabilities have allowed for an unprecedented level of detail, unveiling new supernova remnant candidates, enhancing views of known regions like Sgr A and Sgr B, and revealing myriad new structures such as the non-thermal filaments. Complementary Very Large Array (VLA) data was used to ensure the precision of the astrometry, resulting in a reliable positional framework for the observed phenomena.

Key Findings and Results

1. Supernova Remnants and Radio Structures: The high-resolution imaging illuminates potential new supernova remnants and provides enhanced detail on known remnants. Features such as SNR G0.9+0.1 reveal interactions between pulsar wind nebulae and surrounding supernova shells, potentially indicative of energetic polar outflows.
2. Radio Filaments: The discovery of numerous non-thermal filaments underscores the complexity and dynamism of the Galactic center. These structures, notably the spiral and elongated forms, display varying spectral indices, suggesting differing interactions and origins, possibly in relation to cosmic-ray driven processes.
3. Spectral Index Analysis: Detailed spectral index mosaics were created, pointing to varied emission origins, differentiating between thermal and non-thermal processes in the region. This is crucial for distinguishing astrophysical processes at work, particularly in star-forming regions like Sgr B2.
4. Interactions with Galactic Center Bubbles: The survey elaborates on the association between the filamentary structures and the broader 430 pc bipolar radio bubbles, providing insights into how starburst or black hole feedback processes might drive galactic evolution.

Implications

The implications of this survey are extensive, offering a refined toolset for studying the Galactic center. The ability to differentiate emission processes aids in constructing a discipline-wide framework for understanding galactic phenomena on a macro scale. Furthermore, the data challenge existing models of Galactic center dynamics, calling for deeper exploration into feedback processes and cosmic-ray interactions.

Future Prospects

Future efforts can expand on this groundwork by integrating findings with observations across other wavelengths, leveraging technologies like polarization imaging to better understand magnetic fields and further study cosmic-ray propagation. Additionally, potential follow-up observations with upcoming facilities can refine our understanding of detected phenomena, such as the nature of the radio supernova remnants and the filamentary structures.

In conclusion, the MeerKAT survey has significantly contributed to our understanding of the Galactic center, allowing further exploration into the energetic processes that define this chaotic region. This work sets a new precedent for sensitivity and resolution in radio astronomy, opening pathways for future astrophysical inquiry and enhanced multi-modal research.