Revealing the invisible: Detecting variations in extragalactic magnetic fields

Magnetic fields are frequent all through the universe however extremely difficult to check. They do not instantly emit or replicate mild, and light-weight from all alongside the electromagnetic spectrum stays the first purveyor of astrophysical knowledge. As an alternative, researchers have needed to discover the equal of cosmic iron filings—matter in galaxies that’s delicate to magnetic fields and in addition emits mild marked by the fields’ construction and depth.

In a brand new research revealed in The Astrophysical Journal, a number of Stanford astrophysicists have studied infrared indicators from simply such a fabric—magnetically aligned dust grains embedded within the chilly, dense clouds of star-forming areas. A comparability to mild from cosmic ray electrons that has been marked by magnetic fields in hotter, extra diffuse materials confirmed stunning variations within the measured magnetic fields of galaxies.

Stanford astrophysicist and member of the Kavli Institute for Particle Acceleration and Cosmology (KIPAC) Enrique Lopez-Rodriguez explains the variations and what they might imply for galactic progress and evolution.

Initially from the Canary Islands, Lopez-Rodriguez got here to the Bay Space as a scientist with the Stratospheric Observatory for Infrared Astronomy (SOFIA), the Boeing 737 jetliner modified to hold devices above a lot of the atmospheric dust and water vapor that blocks infrared mild. Earlier than the SOFIA program resulted in 2022, Lopez-Rodriguez joined Stanford, the place he continues to investigate legacy SOFIA knowledge as one of many principal investigators of SALSA, the Survey of extragALactic MagnetiSm with SOFIA.

This interview has been edited for readability and brevity.

Are you able to describe your findings? What makes them so groundbreaking?

That is the primary research evaluating magnetic fields in numerous bodily environments of different galaxies. To do this we checked out 15 totally different close by galaxies in each radio and far-infrared wavelengths. We have now two totally different principal investigators for this research: myself for the infrared knowledge and Sui Ann Mao on the Max Planck Institute for Radio Astronomy in Germany for the radio knowledge.

Our teams discovered two very totally different magnetic fields in the identical galaxies. Radio observations hint a really ordered magnetic subject within the ionized, heat, and diffuse medium one to 2 kiloparsecs above the galactic disks we studied [one kiloparsec is 3,260 light years], whereas far infrared light emitted by magnetically aligned dust grains within the midplane of the disks exhibits a magnetic field that’s nearly twice as chaotic. In abstract, areas with larger star formation had stronger and extra chaotic magnetic fields.

What do these chaotic magnetic fields inform us?

Spiral arms have tangled magnetic fields as a consequence of star formation exercise and the formation of molecular clouds, which signifies excessive ranges of turbulence and probably a spot the place magnetic fields could also be amplified. In distinction, the areas between the arms of spiral galaxies and within the medium above and under the disk have well-ordered magnetic fields, which signifies that galaxy rotation could also be taking part in a task within the ordering of those magnetic fields.

Generally, we do not know the position of magnetic fields in galaxy evolution, however these far-infrared observations inform us that magnetic fields are intrinsically associated to star-forming areas, which is vital to galaxy formation. We do not know precisely how they’re associated however we expect there could be some type of suggestions loop between the 2.

What’s subsequent? How will you search for the character of the suggestions loop?

With this consequence, we are able to now produce three-dimensional research of the magnetic fields in different galaxies that may assist us research their results on star formation exercise and galaxy evolution.

However we additionally want observations with greater angular decision so we are able to get a more in-depth have a look at the star-forming areas, and we additionally want to check the magnetic fields throughout cosmic time. The excellent news is that we’re already getting that form of knowledge with ALMA (the Atacama Massive Millimeter/submillimeter Array). As well as, the subsequent era of NASA space missions additionally embody the identical sorts of far-infrared polarimetric observations we used, solely higher, to check the magnetic fields in a statistical pattern of galaxies.

A number of different Stanford researchers are concerned within the research as nicely. How did you all come collectively right here?

For myself, at NASA I used to be an instrument scientist and flew greater than 100 instances with SOFIA—though every flight was an journey, it was too many instances for me, actually. Many of the observations we used on this research I took myself with HAWC+ [the High-resolution Airborne Wideband Camera+, a far-infrared imager and polarimeter]. I knew the instrument and easy methods to work with the info, and created a brand new observing mode that improved the sensitivity and observing acquisition time by 300%. My analysis focuses on the research of magnetic fields in galaxies, and since I used to be already working carefully with the instrument, knowledge acquisition, and evaluation, this undertaking was an ideal match.

After SOFIA I wished to do full-time science and KIPAC opened the door very properly for me. Particularly once I discovered [Assistant Professor] Susan Clark was coming right here too and realized her analysis objectives matched very nicely with mine. We even have Mehrnoosh [Tahani], who research the magnetic fields within the Milky Way in radio, Sergio [Martin-Alvarez], who does magneto-hydro-dynamic simulations, and Alex [Alejandro S. Borlaff], who’s visiting from NASA-Ames as a NASA postdoctoral fellow.

Now we’ve got a variety of experience in magnetism right here at Stanford, which makes us a novel workforce completely located to extract probably the most science out of those SALSA observations.