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Home » Stanford astrophysicists discover starkly different magnetic fields in galaxies

Stanford astrophysicists discover starkly different magnetic fields in galaxies

Magnetic fields are abundant throughout the universe, yet they pose significant challenges for researchers to study. Unlike other observable phenomena, magnetic fields do not emit or reflect light directly, making it difficult to gather astrophysical data. To overcome this obstacle, scientists have sought cosmic equivalents of iron filings—materials in galaxies that respond to magnetic fields and emit light indicative of their structure and strength.

In a recent study published in The Astrophysical Journal, a team of astrophysicists from Stanford delved into the analysis of infrared signals from such material—dust grains with magnetic alignment found in the cold, dense clouds of star-forming regions. To compare and understand the measured magnetic fields of galaxies, they looked at the light from cosmic ray electrons marked by magnetic fields in warmer, less dense regions and discovered surprising differences.

Enrique Lopez-Rodriguez, a Stanford astrophysicist affiliated with the Kavli Institute for Particle Acceleration and Cosmology (KIPAC), sheds light on these differences and their potential implications for the growth and of galaxies.

Originally hailing from the Canary Islands, Lopez-Rodriguez pursued his scientific journey in the Bay Area, contributing to the Stratospheric Observatory for Infrared Astronomy (SOFIA) program. SOFIA, a modified Boeing 737 jetliner equipped with instruments, facilitated observations above most atmospheric dust and water vapor that hinder infrared light. Even after the conclusion of the SOFIA program in 2022, Lopez-Rodriguez continued his work at Stanford, where he remains actively involved in analyzing legacy SOFIA data as a principal investigator for SALSA—the Survey of extragalactic Magnetism with SOFIA.

This interview has been condensed and edited for clarity.

Can you describe your findings? What makes them so groundbreaking?

In a groundbreaking study, we undertook the first-ever comparison of magnetic fields in various physical environments within other galaxies. To achieve this, we meticulously examined 15 nearby galaxies, utilizing both radio and far-infrared wavelengths. This remarkable research project was led by two principal investigators: myself, responsible for analyzing the infrared data, and Sui Ann Mao, based at the Max Planck Institute for Radio Astronomy in Germany, who handled the radio data.

The outcomes were truly fascinating. Our respective teams discovered starkly different magnetic fields coexisting within the same galaxies. The radio observations revealed a highly ordered magnetic field in the ionized, warm, and diffuse medium situated at heights of one to two kiloparsecs above the galactic disks we focused on (to put it in perspective, one kiloparsec amounts to about 3,260 light years). In contrast, the far-infrared light emitted by magnetically aligned dust grains within the disks' midplane unveiled a magnetic field that displayed nearly twice as much chaos. Interestingly, regions with more intense star formation exhibited stronger and more turbulent magnetic fields.

This pioneering research opens up new avenues of understanding the intricate interplay between magnetic fields and galactic processes, shedding light on the complexities of magnetic field evolution and its potential impact on the growth and evolution of galaxies.

What do these chaotic magnetic fields tell us?

The magnetic fields within spiral arms of galaxies tend to be intricate and tangled, largely influenced by the vigorous star formation activity and the formation of molecular clouds. This complexity suggests the presence of high turbulence, making these regions potential sites for magnetic field amplification. On the other hand, the regions found between the arms of spiral galaxies and in the surrounding medium—above and below the galactic disk—exhibit well-ordered magnetic fields. This orderly arrangement hints at the influence of rotation in shaping these magnetic fields.

While the exact role of magnetic fields in the evolution of galaxies remains elusive, the far-infrared observations have provided crucial insights. They indicate a profound intrinsic connection between magnetic fields and areas undergoing star formation, a fundamental aspect of . The precise nature of this relationship remains uncertain, but researchers hypothesize the existence of a feedback loop between the two phenomena.

Understanding the interplay between magnetic fields and star-forming processes is a crucial step toward unraveling the complexities of galaxy evolution, offering invaluable knowledge about the mechanisms that shape and drive the formation and development of galaxies across the universe.

What's next? How will you look for the nature of the feedback loop?

This groundbreaking discovery opens up exciting possibilities for further research. Armed with these new insights, we can now embark on three-dimensional studies of magnetic fields in other galaxies, enabling us to delve into their impact on star formation activity and the overall evolution of galaxies.

However, to gain a more comprehensive understanding, we require observations with higher angular resolution, allowing us to closely examine the intricate star-forming regions. Additionally, studying magnetic fields across different cosmic epochs is crucial for a more complete picture of galactic evolution. Fortunately, we are making significant progress in these areas with the help of cutting-edge technology.

ALMA (the Atacama Large Millimeter/submillimeter Array) is already providing us with data featuring superior angular resolution, granting us unprecedented proximity to star-forming regions in distant galaxies. Moreover, the next generation of NASA space missions is set to bring us even more advanced far-infrared polarimetric observations. These enhanced capabilities will enable us to study the magnetic fields in a statistical sample of galaxies with greater accuracy and detail.

With these advanced tools at our disposal, we are on the brink of unraveling the intricate relationship between magnetic fields and galactic phenomena. The forthcoming data promises to shed further light on the cosmic processes that drive star formation and shape the evolution of galaxies throughout the vast expanse of the universe.

Several other Stanford researchers are involved in the study as well. How did you all come together here?

During my time at NASA, I served as an instrument scientist and had the incredible opportunity to fly over 100 missions with SOFIA—an adventure in itself, though it eventually became a bit overwhelming. Most of the observations utilized in this study were personally taken by me, utilizing HAWC+—the High-resolution Airborne Wideband Camera+—a remarkable far-infrared imager and polarimeter. I developed a new observing mode that significantly improved sensitivity and acquisition time by an impressive 300%. Given my specialization in studying magnetic fields in galaxies and my close association with the instrument, data acquisition, and analysis, this project was a perfect fit for me.

Following my time with SOFIA, my desire to dedicate myself to full-time scientific research led me to KIPAC, where I found an excellent opportunity. The presence of Assistant Professor Susan Clark, with her research goals closely aligned with mine, made the decision even more appealing. Furthermore, the team at KIPAC is complemented by the expertise of Mehrnoosh Tahani, who focuses on magnetic fields in the Milky Way using radio observations, Sergio Martin-Alvarez, skilled in magneto-hydro-dynamic simulations, and Alex Alejandro S. Borlaff, a NASA postdoctoral fellow visiting from NASA-Ames.

This diverse and specialized team now boasts a wide range of expertise in magnetism here at Stanford, positioning us perfectly to extract the most valuable scientific insights from the SALSA observations. Together, we are uniquely poised to unravel the mysteries of magnetic fields in galaxies and delve into their crucial role in the fascinating process of galactic evolution.

Source: Stanford University

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