Maya Fishbach

Assistant Professor · CITA · University of Toronto

I am an Assistant Professor at the Canadian Institute for Theoretical Astrophysics (CITA), University of Toronto. I am a gravitational-wave astrophysicist and member of the LIGO Scientific Collaboration. Previously, I was a NASA Einstein Postdoctoral Fellow at CIERA, Northwestern University, and before that, I was an NSF Graduate Research Fellow at the University of Chicago, where I completed my PhD under the supervision of Daniel Holz.


How are black holes made?

How are black holes and neutron stars made, and how do they get into binaries?

LIGO and Virgo have revealed a previously-unobserved population of black holes and neutron stars that collide into one another, emitting a burst of energy in the form of gravitational-waves. Meanwhile, the origin of these systems remains an open question. Several formation scenarios have been proposed, from primordial black holes that make up a fraction of the dark matter (“primordial”), to the ends states of binary stellar evolution in the galactic field (”isolated”), to stellar remnants that form binaries through dynamical interactions in dense environments (“dynamical”), with each category consisting of many proposed variations. In my research, I study the population properties of black holes and neutron stars observed in gravitational-waves, in order to learn about the formation history of these systems.

I have pointed out several powerful features in the distribution of spins, masses, mass ratios, and redshifts of LIGO/Virgo's observations. Using LIGO's first four observations, I found evidence for missing big black holes and pointed out the connection to the theoretically proposed pair-instability supernova mass gap for the first time. I also showed that we may have observed a black hole on the far side of the black hole mass gap in LIGO and Virgo's third observing run. I performed the first measurement of the redshift evolution of the merger rate and the mass distribution. I studied the pairing between the two black holes in a binary, analyzing whether black holes are picky about their partners. I performed the first full fit to the gravitational-wave compact binary population, including neutron stars and black holes, quantifying the evidence for a mass gap between neutron stars and black holes. These population properties probe the origin of black holes; for example, whether LIGO's black holes are made from smaller black holes. My research also has implications for the physics of massive stars, binary interactions, and nuclear reaction rates.

As we observe more and more black holes and neutron stars, we can precisely resolve features in the population and push our theoretical understanding. We analyzed the population properties of LIGO/Virgo's first 10 binary black holes in this LIGO/Virgo Collaboration paper. Recently I led the population analysis on the ~50 events in the LIGO/Virgo's second gravitational-wave transient catalog. Check out our detailed results about the Population Properties of Compact Objects from the Second LIGO-Virgo Gravitational-Wave Transient Catalog, or read about the highlights in the introduction I wrote for the Astrophysical Journal Letters' Focus on Gravitational-wave Astrophysics from the Second LIGO-Virgo Transient Catalog.

Where are black holes made?

Where are binary black holes and neutron stars made, and how do these systems co-evolve with their environments?

In order to understand the history of black holes and neutron stars in merging binaries, we must understand where and when they formed. I carried out the first measurement of the evolution of the black hole merger rate as a function of redshift, or cosmic time. By including information from the unresolved stochastic background, we can even constrain the peak merger rate. Contextualizing black holes and neutron stars in cosmic time is a first step towards probing the coevolution of these binaries with the global population of stars, galaxies, and the chemical composition of the universe. For example, studying the evolution of the merger rate reveals the delay times between star formation and black hole merger, which can discriminate between proposed formation channels. Using the second LIGO/Virgo catalog, I measured the binary black hole time delay distribution the first time. We can learn even more about the history of gravitational-wave sources by identifying and characterizing their host galaxies.

How big is the universe?

What can gravitational-wave sources teach us about the size and age of the universe, and the nature of gravity?

The luminosity distance to a compact binary merger is directly encoded in its gravitational-wave signal, earning these systems the name “standard sirens.” This feature makes compact binary mergers extremely powerful probes of the size of the universe and the nature of gravity. I have developed analyses to measure the expansion rate of the universe –the Hubble parameter– by combining gravitational-wave measurements of distance with redshifts supplied either by electromagnetic counterparts, a catalog of galaxies, the redshifted pair-instability feature in the black hole mass spectrum, or prior knowledge of the peak merger redshift (cosmic noon for merging binaries). Standard sirens can also be used to probe the nature of gravity itself; for example, by measuring the number of spacetime dimensions or the running of the Planck mass. For a recent overview of standard siren cosmology, check out the standard sirens chapter I wrote for this Living Review on emerging cosmological probes.

Curriculum Vitae

Download my CV (updated June 2024)


Check out my publications on ADS


My research has been featured on NPR, CNN, the Atlantic, Quanta Magazine, Science Magazine, Nature News, Symmtery Magazine, Astrobites, AAS Nova, APS News, University of Chicago News, the Daily Beast, Science News, and Sky & Telescope, among other media. Check out some links below! You can also hear me talk about my research in interviews by Alan Alda and Bad Astra.

Insights from Misaligned Black Hole Pairs by Kerry Hensley for AAS Nova, October 2022

What Gravitational Waves Have Taught Us About Black Holes by Camille M. Carlisle for Sky & Telescope, June 2022

CIERA High School Researcher is Regeneron National Science Talent Search Grand Prize Winner by Marlena Noeth and Darvell Jones for CIERA, March 2022

When A City-Size Star Becomes A Black Hole's Lunch, The Universe Roils by Nell Greenfieldboyce for NPR, June 2021

Ripples in spacetime reveal black holes slurping up neutron stars by Adrian Cho for Science Magazine, June 2021

Growing Inventory of Black Holes Offers a Radical Probe of the Cosmos by Thomas Lewton for Quanta Magazine, February 2021

Big Black Holes Dominate New Gravitational-Wave Catalog by Camille Carlisle for Sky & Telescope, November 2020

What 50 gravitational-wave events reveal about the Universe by Davide Castelvecchi for, October 2020

The universe teems with weird black holes, gravitational wave hunters find by Adrian Cho for Science Magazine, October 2020

Going Deep into Black Holes by Sophia Chen for APS News, June 2020

Merger Partners? Maybe. by Tarini Konchady for AAS Nova, April 2020

What Next for Gravitational Wave Detection? by Sophia Chen for APS News, June 2019

Gravitational waves could soon provide measure of universe’s expansion by Louise Lerner for UChicago News, October 2018

Gravitational waves provide dose of reality about extra dimensions by Louise Lerner for UChicago News, September 2018

Black Hole Mergers Through Cosmic Time by Kerry Hensley for AAS Nova, September 2018

Are We Closer to Finding a Fifth Dimension? by Matthew R. Francis for The Daily Beast, February 2018

An Answer to LIGO’s Low-Mass Black Hole Woes by Thankful Cromartie for Astrobites, September 2017

Are LIGO’s Black Holes Made From Smaller Black Holes? by Susanna Kohler for AAS Nova, May 2017

Spin may reveal black hole history by Emily Conover for Science News, January 2017


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For more information about LIGO and gravitational-waves, check out:

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