The new map, dubbed Quaia, includes around 1,295,502 quasars from across the visible Universe and could help astronomers better understand the properties of dark matter.
Storey-Fisher et al. present the all-sky quasar catalog Quaia, that samples the largest comoving volume of any existing spectroscopic quasar sample. Image credit: Storey-Fisher et al., doi: 10.3847/1538-4357/ad1328.
Quasars are powered by supermassive black holes at the center of galaxies and can be hundreds of times as bright as an entire galaxy.
As the black hole’s gravitational pull spins up nearby gas, the process generates an extremely bright disk, and sometimes jets of light, that telescopes can observe.
The galaxies that quasars live in sit inside massive clouds of invisible dark matter.
The distribution of dark matter gives insight into how much dark matter there is in the Universe, and how strong it clusters
Astronomers compare these measurements across cosmic time to test our current model of the Universe’s composition and evolution.
Because quasars are so bright, astronomers use them to map out the dark matter in the very distant Universe, and fill in the timeline of how the cosmos evolved.
For example, scientists have already compared the new quasar map with the cosmic microwave background, a snapshot of the oldest light in our cosmos.
As this light travels to us, it is bent by the intervening web of dark matter — the same web mapped out by the quasars — and by comparing the two, scientists can measure how strongly matter clumps together through time.
“The new quasar catalog is different from all previous catalogs in that it gives us a three-dimensional map of the largest-ever volume of the Universe,” said Professor David Hogg, an astronomer at the Flatiron Institute’s Center for Computational Astrophysics and New York University.
“It isn’t the catalog with the most quasars, and it isn’t the catalog with the best-quality measurements of quasars, but it is the catalog with the largest total volume of the Universe mapped.”
Professor Hogg and his colleagues built the Quaia map using data from the third data release of ESA’s Gaia mission, which contained 6.6 million quasar candidates, and data from NASA’s Wide-Field Infrared Survey Explorer and the Sloan Digital Sky Survey.
By combining the datasets, they removed contaminants such as stars and galaxies from Gaia’s original dataset and more precisely pinpointed the distances to the quasars.
“We were able to make measurements of how matter clusters together in the early Universe that are as precise as some of those from major international survey projects — which is quite remarkable given that we got our data as a ‘bonus’ from the Milky Way-focused Gaia project,” said Dr. Kate Storey-Fisher, a postdoctoral researcher at the Donostia International Physics Center.
“It has been very exciting to see this catalog spurring so much new science.”
“Researchers around the world are using the quasar map to measure everything from the initial density fluctuations that seeded the cosmic web to the distribution of cosmic voids to the motion of our Solar System through the Universe.”
The astronomers created a map showing where dust, stars and other nuisances are expected to block our view of certain quasars, which is critical for interpreting the quasar map.
“This quasar catalog is a great example of how productive astronomical projects are,” Professor Hogg said.
“Gaia was designed to measure stars in our own Galaxy, but it also found millions of quasars at the same time, which give us a map of the entire Universe.”
The results appear in the Astrophysical Journal.
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Kate Storey-Fisher et al. 2024. Quaia, the Gaia-unWISE Quasar Catalog: An All-sky Spectroscopic Quasar Sample. ApJ 964, 69; doi: 10.3847/1538-4357/ad1328
