How do galaxies evolve? Perhaps a college student provided the missing link

Image Credit: NASA, ESA, The Hubble Heritage Collaboration, Evans

A University of Massachusetts Amherst undergraduate student has contributed important work regarding the growth of stars and black holes, providing key insight into how they are related. This new information will allow the James Webb Space Telescope (JWST) to untangle how galaxies work more efficiently.

Astronomers know that the evolution of galaxies is powered by two processes: the growth of supermassive black holes at the center of each galaxy and the formation of new stars. How these processes relate has remained a mystery and is one of the questions that the recently launched James Webb Space Telescope (JWST) will explore. Work by Meredith Stone, who graduated from the UMass Amherst astronomy program in May 2022, will help scientists better understand how they are related.

Stone, who completed this research under the supervision of Alexandra Pope, professor of astronomy at the University of Massachusetts Amherst and senior author of a new paper recently published in Astrophysical Journal. “And we know that black hole growth and star formation play critical roles. We think the two are related and that they regulate each other, but until now, it’s been very difficult to know exactly how.”

Part of the reason why it’s so difficult to study the interaction between black holes and stars is that we can’t really see these interactions because they happen behind massive clouds of galactic dust. “For galaxies that are actively forming stars, dust can absorb more than 90% of visible light, and that dust absorbs visible light,” says Pope.

However, there is an alternative solution: when dust absorbs visible light, it heats up, and although the naked eye can’t see heat, infrared telescopes can. “We used the Spitzer Space Telescope,” which was collected during the Great Observations All-sky LIRG Survey (GOALS), says Stone, who will begin her graduate studies in astronomy at the University of Arizona this fall, to look at the mid-wavelength infrared range. for some of the brightest galaxies relatively close to Earth.” In particular, Stone and her co-authors have been searching for tell-tale tools that represent the imprints of black holes and stars in the midst of formation.

The difficulty is that these fingerprints are very faint and almost impossible to distinguish from the general noise of the infrared spectrum. “What Meredith has done is calibrate the measurements of these detectors so that they are more distinct,” says Pope.

Once the team had these most remarkable observations in hand, they were able to see that in fact, black hole growth and star formation occur simultaneously in the same galaxies and seem to influence each other. Stone was able to calculate a ratio that describes how the two phenomena are related.

Not only is this an exciting scientific achievement in itself, but the JWST could also take up Stone’s work, with his unprecedented access to light in the mid-infrared spectrum, and use it to focus more on the remaining questions. Although Stone and her co-authors, including UMass Amherst graduate student Jed McKinney, have determined how black holes and stars in the same galaxy are related, why they are related remains a mystery.

Supermassive black holes discovered inside dying galaxies in the early universe

more information:
Meredith Stone et al., Measurement of star formation and black hole accretion rates in tandem using mid-infrared spectra of illuminated local infrared galaxies, Astrophysical Journal (2022). DOI: 10.3847 / 1538-4357 / ac778b

Submitted by University of Massachusetts Amherst

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