Research Highlights

Jun 16, 2022 | Exploring the Cosmos while Preserving Spaceship Earth

Extracting information from the data gathered by large cosmological surveys requires sophisticated theory modeling that combines physical models of our Universe, astrophysical models of galaxies, and telescope and survey-specific models of measurement uncertainties. The theory models involved are now quite sophisticated and typically have thirty to fifty parameters, making it hard to find plausible sets of parameters that describe the observational data. Therefore, even with the most advanced algorithms and software, analyses of modern cosmological datasets are costly, not only in the time required for computers to finish an analysis, but in energy needed to run the computers.

May 31, 2022 | "Studying the physics of astrophysics": Steve Kahn looks back at the founding of KIPAC

Celebrated physicist and Rubin Observatory project scientist Steve Kahn has crisscrossed the country multiple times during his academic career—from a PhD at University of California Berkeley to Columbia University and back west to Stanford—but his biggest leap was shifting from a decades-long career in X-ray astronomy to building the world’s largest digital camera for the Legacy Survey of Space and Time (LSST). Now he's making another big leap to Dean of the Division of Mathematical and Physical Sciences at the University of California, Berkeley.

May 2, 2022 | The telescope at the edge of the solar system

New research led by KIPAC PhD student Alex Madurowicz, published in the Astrophysical Journal, describes a novel technique to image Earth-like exoplanets in detail by using the Sun as a telescope. The gravity of the Sun lenses and magnifies light from a distant planet, but also distorts the image into what is now known as an Einstein ring. By tracing the path of light as it bends around the Sun, the Einstein ring can be deconstructed to recover an image of a distant planet. This concept would allow for observations in far greater detail than an ordinary telescope could ever possibly achieve, such as movies of the detailed surfaces of exoplanets.

Mar 30, 2022 | #PandemicGoals: Building a record-breaking observatory while locked down in Chile

Sometime this fall, the Legacy Survey of Space and Time (LSST) camera will be delivered to Santiago on a 747 jumbo jet and trucked to the Rubin Observatory Summit Facility. Located nearly nine thousand feet above sea level in the Andean foothills—about two hours from Chile’s second-oldest city, La Serena—the observatory will house an 8.4 meter (almost 28 feet!) telescope containing the largest digital camera ever built. Each night, the SUV-sized camera will collect thousands of wide-field images of the southern sky, looking further back into the history of the universe with each exposure. Commissioning engineers and scientists from the SLAC National Accelerator Laboratory (SLAC) have been developing novel ways to handle the many technical challenges that come with building a Guinness World Record breaking observatory.

Mar 25, 2022 | Confronting models with DES Year 3 data, or: How did we get here, and what’s next?

In DES cosmology analyses we ultimately learn about physics by comparing the predictions of a model to measurements. Even with our most sophisticated models of the Universe, we can’t predict exactly where a given galaxy or clump of matter that is causing gravitational lensing will appear. However, we don’t need to do that to learn about physics! We just need to focus on something we can predict: the statistical properties of how we expect galaxy positions and the shear signal of weak gravitational lensing to be distributed relative to one another. This means that when we compare our model to measurements, we’re not comparing models and measurements at the level of the full map of the positions and shapes of all the galaxies measured by DES. Instead we summarize information in those maps using statistical measurements.

Feb 3, 2022 | Objects In Mirror Are Bluer Than They Appear: What a Galaxy's Color Says About Its Distance

Understanding how the Universe evolved from a dense ball of superheated plasma to the vast canvas of stars and galaxies it is today—and what it will become next—remains a fundamental question asked throughout history. Today, we can begin to answer this question by making more precise measurements of objects in space, from our nearest neighbors to the deepest recesses of the visible Universe, than we've ever been able to before. The resulting maps help us frame the question of how the Universe unfolds by measuring how cosmic structure—the web of galaxies that make up the Universe—grows over time, according to the rules of physics. A key part of measuring this cosmic structure is to determine the distances to the many galaxies we observe with our telescopes.

Jan 5, 2022 | How to tease out the tiniest distortions of galaxy shapes to probe the secrets of the Universe

One of the key measurements of a galaxy’s shape is its ellipticity, which, for those who remember their geometry, is zero for a perfect circle and approaches one for something flat like a pancake. In the case of a galaxy, its ellipticity is a measure of how round it appears to us as we view it through a telescope. One might guess that, for an array of galaxies, the average of all galaxies’ ellipticities would be zero over a large volume, because galaxies are seemingly randomly oriented. That is, it would look as if a galaxy is just as likely to be slanted in one direction as any other. To the naked eye, this generally seems to be true. However, this is not quite the case!

Sep 26, 2021 | Between the worlds of the visible and invisible lies: Dark Matter

Two powerful probes of dark matter on small scales—strong gravitational lensing and ultra-faint dwarf galaxies—join together to set world-leading constraints on the nature of the dark matter particle in a recent study led by KIPAC researchers, including the authors. In the process, we have shown that combining these probes provides a framework to detect “dark halos,” clumps of dark matter that have no associated visible light, using the vast amounts of deeper data promised by upcoming surveys. 

Aug 1, 2021 | Cosmos in a Box: Supercomputer simulations of pencil-and-paper universes

Cosmology in the 2020s is in a particularly privileged position as far as scientific fields go. Soon several experiments will come online that will give us a tremendous amount of information about the so-called "dark" components of the Universe: dark matter and dark energy. But if we’re not careful, we run the risk of drawing inadequate conclusions from these rich datasets. Not because our data aren’t adequate—they’re amazing—but because our models aren’t good enough. That’s why much current work is focused on creating better predictions of the signals these experiments are designed to measure.

Apr 22, 2021 | What the nose shows: Black Widow systems and the fundamental nature of nuclear matter

Neutron stars are made of highly compressed material called degenerate matter, which is so dense it must be described using the laws of quantum mechanics. As a result, NSs should have a unique relationship between mass and radius, determined by an “equation of state” (EoS). An EoS is a thermodynamic description of the entwined properties of, for example, temperature, pressure, and volume. The steam in a pressure cooker can be described by an EoS; so can the interior of a star. For neutron star-like conditions only density matters, which results in a density-dependent EoS, P(rho). But because their material is in an exotic state not found anywhere on Earth, the EoS for neutron stars remains unknown.

Mar 22, 2021 | Optical joins X-Ray: Optical Luminosity-Time correlations for more than 100 GRBs

A new correlation has been discovered in optical observations of gamma ray bursts (GRBs) that may be the key to using GRBs as cosmological distance indicators, adding another rung to the so-called "distance ladder" that helps astronomers determine the size of the observable Universe.

Feb 19, 2021 | What happens to the supermassive black holes at the hearts of merging galaxy trios?

While there have been extensive previous studies of mergers between two galaxies, a recent study that helps reveal what happens when three galaxies merge is one of the first to systematically look at the consequences for the supermassive black holes at their hearts when a trio of galaxies comes together.