How galaxies and supermassive black holes grow together

(ORDO NEWS) — Over the past two decades, astronomers have come to the conclusion that most, if not all, galaxies have massive black holes at their centers, and the masses of the black hole and its galaxy are interconnected. But how are these two objects related? A student at the University of Hawaii at the Manoa Institute of Astronomy (IfA) participating in the National Science Foundation (NSF) Student Experience Program (REU) may have uncovered part of the answer to this question.

Rebecca Minsley participated in the 2019 REU IfA program and worked for 10 weeks with her mentor, deputy researcher at the Mauna Kea Telescope (MSE) project, Andrei Petrik. Thoroughly scanning hundreds of galaxy images, Minsley began to define a clearer picture of the evolution of the galaxy. “The growth of a galaxy may be due to interactions with other galaxies that contribute to the appearance of supermassive black holes (MSCHs) that grow in the center of the galaxy,” Minsley explained.

Gas and dust between stars, called the interstellar medium, is the fuel for both the growth of the NMSF and the formation of new stars. But recent work shows that the interstellar medium can have different properties – it is warmer in galaxies in which there is a growing supermassive black hole in the nuclei, compared with those galaxies that do not. A warmer gas is less likely to collapse into new stars, so this discovery may indicate that a growing central MESF decreases the ability of the galaxy to create new stars.

What could be responsible for heating the interstellar medium? Starlight, especially from hot stars, can do this. But interactions between galaxies – when they collide or even just pass close to each other – can cause large-scale shock waves that compress a less dense gas, increasing the likelihood of star formation.

Minsley studied the shapes of 630 galaxies using images made by the Pan-STARRS telescope. She classified galaxies into mergers, early mergers and non-mergers, and then compared these forms with the light emission of the same galaxies at longer medium infrared wavelengths, where she could study the properties of the interstellar medium.

“When the galaxies come close enough to each other, they portray a kind of galactic dance, until they ultimately come together in a single whole. These interactions have well-documented features that allowed me to classify our set of galaxies, ”Minsley said. “This project showed me the complexity and complexity of all the processes taking place inside the galaxies.”

Minsley and her colleagues found that in galaxies with active black holes, the interstellar medium is warmer, the ratios of warm molecular gas to other coolants are higher, and other characteristics of dust particles have a wider range of values ​​than in galaxies where black holes are at rest.

“In the neighboring universe, we find that the warm interstellar medium of galaxies in which the NMS in their centers grow is different from those that don’t,” Petrik explains. “We assume that the very same processes that direct fuel to the MNFB also transfer energy back to the interstellar medium of the galaxy.” Petrik adds that future, more detailed observations will allow researchers to confirm these energy transfer processes.

This work was published in the May 10 issue of the Astrophysical Journal and is available as a preprint on ArXiv.

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