New Map Reveals Complicated Magnetics Of Milky Way’s Inner Core

Oct 30, 2024

Three-color background image also uses data from European Space Agency (ESA) Herschel Space ... [+] Observatory and the South African Radio Astronomy Observatory (SARAO) MeerKAT Radio Telescope.

Galactic scale magnetism has long been poorly understood. But a new map of our Milky Way's innermost core —- not too far from Sag A*, the supermassive black hole at our galactic center —- is giving astronomers a better understanding of the role that magnetism plays in regulating tar both structure and star formation within our own galaxy.

In fact, galactic magnetism may stymie star formation in ways that have heretofore been unappreciated.

An international Villanova University-led team, funded in part by NASA, used the far infrared telescope aboard NASA and the German Aerospace Center’s now decommissioned SOFIA airborne observatory on nine flights in 2020 and 2021. From there, the team took far infrared observations of the galaxy’s dusty inner regions.

The galactic center is a unique part of our galaxy, the densities are higher, the velocities are faster, and the magnetic fields there are doing things that we don't see in other regions, Team leader David Chuss, chairman of Villanova University’s physics dept. in Pennsylvania.

This is a brand-new look at the magnetic fields in the dust phase of the of the of the galactic center that shows a complicated, intricate interplay between the dynamics and the magnetic fields, says Chuss. This paves the way for a new understanding of how magnetic fields affect the dynamics of centers of galaxies, he says.

Inside the central molecular zone, there’s also a lot of molecular species, because it's cool enough that molecules can form, says Chuss.

As for how the survey was done?

The team primarily used the Stratospheric Observatory for Infrared Astronomy —- a telescope housed in a 747 and flown at 45,000 feet —- to map the magnetic fields in the center of the Milky Way, notes Villanova University.

The project, dubbed “FIREPLACE,” (Far-InfraREd Polarimetric Large Area CMZ Exploration), has produced the largest map ever obtained with SOFIA.

Coupled with multispectral archival data from South Africa’s MeerKAT low frequency radio array and the European Space Agency's Herschel space observatory, the team has put together the most detailed map ever made of the Milky Way’s innermost magnetic fields.

The survey was initially proposed to address the question of how magnetic fields at infrared wavelengths vary throughout the CMZ, note the authors of a paper just submitted to The Astrophysical Journal.

FIREPLACE is a survey of the far-infrared emission from cool dust grains within the central 500 light years of our galaxy, which via magnetism have aligned themselves with the region’s magnetic fields.

The survey has yielded some 65,000 magnetic field pseudovectors, Dylan Pare, a postdoctoral researcher in astrophysics at Villanova University and lead author of the APJ paper, told me via email.

Pseudovectors refer to the fact that when we measure polarization —- the direction in which the light is oscillating, we get a direction and magnitude, says Chuss. But we don’t have a “head” and “tail” (we don’t know which direction is “forward”), he explains.

As to how these fields are aligned?

The magnetic fields are preferentially aligned in two directions: parallel to the galactic plane and perpendicular to the galactic plane, says Pare. These two directions connect to different structures in the galactic center, he says.

The parallel direction is aligned with the distribution of molecular clouds in the region; conversely, the perpendicular direction is aligned with a population of unique thread-like structures that are seen throughout the galactic center, says Pare. These results give us much improved insight into how the magnetic field is ordered in the region, he says.

Magnetic fields are important for star formation, but star formation is very inefficient, says Chuss.

Stars collapse out of dust clouds in the Milky Way, but that process should happen a lot faster than we observe, he says. Magnetic fields are one of the suspects as to why star formation is as inefficient as it is, says Chuss. Because if you squeeze magnetic fields, they push back and they could provide support against the collapse of clouds that form stars, he says.

What’s next?

Questions remain on the underlying physics of the magnetic field distribution in our FIREPLACE observations, says Pare. He says he’ll perform further analysis of how the magnetic field connects to the different structures in the region, which will deepen our understanding of how the magnetic field has shaped and impacted the central region of the Milky Way.

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