New simulation shows how galaxies feed their supermassive black holes
First model to show how gas flows across universe into a supermassive
black hole's center

Date:
August 17, 2021
Source:
Northwestern University
Summary:
While other simulations have modeled black hole growth, new
model is the first single computer simulation powerful enough to
comprehensively account for the numerous forces and factors that
play into the evolution of supermassive black holes. Simulation
shows that galaxies' spiral arms 'put the brakes on gas,' enabling
it to fall into the black hole and as gas heats up while falling
into a black hole, it turns into a bright quasar.



FULL STORY ========================================================================== Galaxies' spiral arms are responsible for scooping up gas to feed to
their central supermassive black holes, according to a new high-powered simulation.


========================================================================== Started at Northwestern University, the simulation is the first to show,
in great detail, how gas flows across the universe all the way down to
the center of a supermassive black hole. While other simulations have
modeled black hole growth, this is the first single computer simulation powerful enough to comprehensively account for the numerous forces and
factors that play into the evolution of supermassive black holes.

The simulation also gives rare insight into the mysterious nature of
quasars, which are incredibly luminous, fast-growing black holes. Some
of the brightest objects in the universe, quasars often even outshine
entire galaxies.

"The light we observe from distant quasars is powered as gas falls
into supermassive black holes and gets heated up in the process," said Northwestern's Claude-Andre' Faucher-Gigue`re, one of the study's senior authors. "Our simulations show that galaxy structures, such as spiral
arms, use gravitational forces to 'put the brakes on' gas that would
otherwise orbit galaxy centers forever. This breaking mechanism enables
the gas to instead fall into black holes and the gravitational brakes,
or torques, are strong enough to explain the quasars that we observe."
The research was published today(Aug. 17) in the Astrophysical Journal.

Faucher-Gigue`reis an associate professor of physics and astronomy
at Northwestern's Weinberg College of Arts and Sciencesand a member
of the Center for Interdisciplinary Exploration and Research in Astrophysics(CIERA). Daniel Angle's-Alca'zar, an assistant professor at
the University of Connecticut and former CIERA fellow inFaucher-Gigue`re's group, is the paper's first author.



========================================================================== Equivalent to the mass of millions or even billions of suns, supermassive
black holes can swallow 10 times the mass of a sun in just one year. But
while some supermassive black holes enjoy a continuous supply of food,
others go dormant for millions of years, only to reawaken abruptly
with a serendipitous influx of gas. The details about how gas flows
across the universe to feed supermassive black holes have remained a long-standing question.

To address this mystery, the research team developed the new simulation,
which incorporates many of the key physical processes -- including
the expansion of the universe and the galactic environment on large
scales, gravity gas hydrodynamics and feedback from massive stars --
into one model.

"Powerful events such as supernovae inject a lot of energy into
the surrounding medium, and this influences how the galaxy evolves," Angle's-Alca'zar said. "So we need to incorporate all of these details
and physical processes to capture an accurate picture." Building on
previous work from the FIRE ("Feedback In Realistic Environments")
project, the new technology greatly increases model resolution and allows
for following the gas as it flows across the galaxy with more than 1,000
times better resolution than previously possible.

"Other models can tell you a lot of details about what's happening very
close to the black hole, but they don't contain information about what
the rest of the galaxy is doing or even less about what the environment
around the galaxy is doing," Angle's-Alca'zar said. "It turns out,
it is very important to connect all these processes at the same time."
"The very existence of supermassive black holes is quite amazing, yet
there is no consensus on how they formed," Faucher-Gigue`re said. "The
reason supermassive black holes are so difficult to explain is that
forming them requires cramming a huge amount of matter into a tiny
space. How does the universe manage to do that? Until now, theorists
developed explanations relying on patching together different ideas for
how matter in galaxies gets crammed into the innermost one millionth of a galaxy's size." With the new simulations, researchers can finally model
how this happens. For example, the new simulation will help researchers understand the origin of the supermassive black hole at the center of our
own Milky Way galaxy as well as the supermassive black hole at the center
of the Messier 87 galaxy, which was famously captured by the Event Horizon Telescopein 2019. Next, the researchers aim to study large statistical populations of galaxies and their central black holes to better understand
how black holes can form and grow under various conditions.

========================================================================== Story Source: Materials provided by Northwestern_University. Original
written by Amanda Morris. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Daniel Angle's-Alca'zar, Eliot Quataert, Philip F. Hopkins,
Rachel S.

Somerville, Christopher C. Hayward, Claude-Andre'
Faucher-Gigue`re, Greg L. Bryan, Dusan Keres, Lars Hernquist, James
M. Stone. Cosmological Simulations of Quasar Fueling to Subparsec
Scales Using Lagrangian Hyper- refinement. The Astrophysical
Journal, 2021; 917 (2): 53 DOI: 10.3847/ 1538-4357/ac09e8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210817131435.htm

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