The universe can no longer hide behind the zone of avoidance

The central region of the Milky Way, also known as the Avoidance Zone. Credit: ESO/S. Brunier

Our view of the cosmos is still limited by the fact that we are located in a galaxy filled with interstellar gas and dust. This is particularly visible in the central region of the Milky Way, which is filled with so much dust that it is sometimes called the Avoidance Zone. Within this zone, our observations of extragalactic objects are limited, but this is starting to change.

Although dust in the avoidance zone prevents visible light from passing through it, infrared and radio light can penetrate the region. We have long used radio and infrared observations to study the center of our galaxy, for example to observe the stars that orbit our supermassive black hole. Now, a new study published on the arXiv The preprint server used public sky surveys to search for galaxies in the area.

The work focuses on data from the VISTA Variables in Vía Láctea (VVV) near-infrared public survey, collected by the VISTA telescope in Paranal, Chile. Although the survey focused on studying globular clusters and open clusters, it also captured data on galaxies in the region. To distinguish galaxies from other objects, the team began by selecting extended objects within the data. They then filtered their objects looking for those with a typical galactic spectrum. This meant they would miss many galaxies, but their goal was to find some, not all.

The universe can no longer hide behind the zone of avoidance

A galaxy seen by 2MASS compared to VVV. Credit: Duplancic, et al.

They then compared their candidates with data from the 2MASS extended source catalog. Although 2MASS contains 1.5 million objects, only 271 of them are in the VVV study region, and the team found that only 182 of them are galaxies. It’s a small number, but the results are impressive. Images of galaxies captured by the VVV survey show significantly greater detail than the 2MASS survey, and this work was able to confirm 75% of the 2MASS galaxies in the region.

This is only a first step in the study of galaxies hidden by the avoidance zone. The team plans to continue this work and bring in data from the VVV eXtended Survey, which should allow it to study thousands of galaxies. As this study shows, the center of our galaxy is no longer a region to avoid. This poses significant challenges, but the reward will be the understanding of a long-hidden part of the universe.

More information:
Fernanda Duplancic et al, Illuminating the universe behind the Milky Way bulge, arXiv (2023). DOI: 10.48550/arxiv.2310.13156

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