My Research

Broadly, I am interested in the processes by which large-scale structures form and evolve along the cosmic timeline. In particular, I use major infrared-through-radio facilities to trace galactic features (e.g., cold molecular and atomic gas, dust emission, and starlight) in the hopes of studying the physics behind the most highly star-forming galaxies in the Universe and how they are shaped by their environments. I care a lot about the evolution of galaxy protoclusters from the epoch of reionization down to cosmic noon, particularly those that are anchored by massive systems --- radio galaxies, active galactic nuclei (AGN) and/or highly luminous quasars.

COSMOS-3D

COSMOS-3D is a JWST Cycle 3 Large Program covering 0.33 square degrees with NIRCam/WFSS in F444W. This is complemented by imaging in F115W, F200W, and F356W, adding to COSMOS-Web (F115W, F150W, F277W, F444W). Finally, we acquire 484 square arcmin of parallel MIRI F1000W/F2100W imaging, overlapping with COSMOS-Web's F770W. I am leading the creation of photometry and photometric redshift catalogs for thousands of sources, with a focus on detecting [OIII] emitters at z>7. This will enable science like galaxy-galaxy clustering, the discovery of protoclusters, constraints on the interstellar and stellar properties of EoR galaxies, and mapping of the IGM. Stay tuned!

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An infrared spectroscopic view of quasar environments

I am a member of the ASPIRE team (A SPectroscopic Survey of biased halos In the Reionization Era), which targets 25 z>6.5 quasars with JWST/NIRCam broadband imaging and WFSS, ALMA Band 6 imaging and spectroscopy, and a host of other instruments spanning X-ray to radio wavelengths. I am most interested in characterizing overdense environments of these luminous quasars to find evidence of star-forming protoclusters, as traced by [OIII] and [CII]. In Champagne et al. (2025ab), we discovered a protocluster around a z=6.6 quasar extending beyond 10 Mpc! The structure shows evidence of spatial variations in star-forming properties which we take as evidence for inside-out growth and increased star formation/AGN fuel from cosmic gas inflows.

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Searching for companions around z>6 quasars

My master's project built on my work with Dr. Fabian Walter at MPIA, in which we used ALMA Band 6 observations of z=6 quasars to search for dust continuum overdensities. Such an overdensity would suggest evidence for early clustering around massive quasars, and these have been found with other tracers such as [CII] and Lyman-alpha. Interestingly, we did not find a statistical overdensity in continuum dust emission, but it's important to keep in mind that a continuum search probes Gpc scales: a true overdensity may exist but its signal could be washed out.

Indeed, in a followup paper we tried a complementary technique using HST to look for Lyman break-selected galaxies -- i.e., the less extreme star-forming galaxies than those traced by ALMA. In a subsample of three quasars, we found an extreme overdensity around one z=6.6 quasar, a moderate overdensity very close to a z=6 quasar whose overdensity profile is in line with those predicted for protocluster cores, and no overdensity around a z=6.9 quasar. These works highlight the genuine diversity of environments around quasars as well as the limitations of photometric selections to constrain the presence of galaxy overdensities. Learn more

Galaxy protoclusters near coalescence at z~2.5

Are DSFGs ubiquitous in protoclusters? Do all protoclusters go through starburst periods? Can the molecular gas trigger simultaneous starburst events in structures several comoving Mpc across? Working with a famous knot of the COSMOS Hyperion protocluster at z=2.5, we performed a full census of the molecular gas, dust, and stellar content, and have drawn exciting conclusions about the assembly of protoclusters across cosmic time. Most notably, protoclusters at z~2.5 mark an important transitional phase just before virialization, where extremely gas- and dust-rich galaxies begin to fall towards the dense central core, just before we see the smoking gun X-ray signature of the intracluster medium. Learn more

Bibliography

You can find a full CV here or take a look at my ADS record.

"No Evidence for Millimeter Continuum Source Overdensities in the Environments of z=6 Quasars," Champagne et al., 2018, ApJ, 867, 153

"Comprehensive Gas Characterization of a z=2.5 Protocluster: A Cluster Core Caught in the Beginning of Virialization?" Champagne et al., 2021, ApJ, 913, 110

"A Mixture of LBG Overdensities in the Fields of Three z=6-7 Quasars: Implications for the Robustness of Photometric Selection," Champagne et al. 2023, ApJ, 952, 99

"A Quasar-Anchored Protocluster at z=6.6 in the ASPIRE Survey: I. Properties of [OIII] Emitters in a 10 Mpc Overdensity Structure," Champagne et al. 2025a, ApJ, 981, 113C

"A Quasar-Anchored Protocluster at z=6.6 in the ASPIRE Survey: II. An Environmental Analysis of Galaxy Properties in an Overdense Structure," Champagne et al., 2025b, ApJ, 981, 114C

Girl with the ALMA Tattoo

I grew up in Jackson, New Jersey. I love bagels, pizza, and the Jersey Shore, and I hate making left turns. I love getting tattoos, traveling the world, and crocheting.

I earned my B.S. in physics and astrophysics in 2016 from Rutgers University, where I completed a bachelor's thesis under the advice of Prof. Chuck Keeton. As an undergraduate, I was an NSF-REU student at Cornell University working on gravitationally lensed submillimeter galaxies, which was my first introduction to submillimeter observations with the SMA! I was also a research intern under Dr. Fabian Walter at MPIA using ALMA data to search for dust continuum overdensities around z>6 quasars. A budding interest in submillimeter observations and dusty galaxies led me to Prof. Caitlin Casey, who eventually supervised my doctoral thesis.

As I was learning about astronomy as a career option, what fascinated me most was radio interferometry and how it has revolutionized what we know about the long-wavelength Universe. To celebrate that passion, I tattooed a dish on my arm, so feel free to call me by my self-given nickname, Girl with the ALMA Tattoo. I'm also a walking interferometer, because I recently got a JWST tat too!

I publish under Jaclyn B. Champagne, but if you knew me prior to 2016, you may remember me with my maiden name, Bradli. Bradli is my dad's surname, and it's pronounced like the Anglo-Saxon "Bradley." But due to the Anglicization of what was an originally an Italian name, most people can't spell it. And how will you ever find me on arxiv if you can't spell Bradli? So in 2017 I legally changed my name to my mom's surname, Champagne, to celebrate my Cajun heritage and acquire an easier to spell name. :)

Professional Activities

I'm interested in lots of professional activities besides research! I'm particularly passionate about making astronomy research more accessible for undergraduates through teaching and mentoring.

Python for beginners

Developed for the aforementioned TAURUS program, I have designed a series of Jupyter notebooks containing step-by-step tutorials for Python beginners. The beginning tutorials are aimed toward the first-time undergraduate unfamiliar with basic command-line work, but it is easy to jump ahead if you are simply looking for some Python basics. It contains instructions for the fundamental things like syntax, array manipulation, plotting, plus astropy demonstrations geared specifically for astronomers. We have newly added some more advanced demos for photometry, spectroscopy, and plotting tricks. This is all available for public use on github.

Teaching

In 2019 I was a team member for the UC Santa Cruz ISEE Professional Development Program, for which we developed an undergraduate inquiry activity about galaxy spectra. I returned in 2024 to deliver an optics activity to the Akamai Workforce Initiative interns in Hilo, HI. In 2022 I joined the Computational Research Access NEtwork (CRANE) team, an NSF-supported and early career researcher-led mentorship and teaching program focused on bringing Python fundamentals to physics and astronomy majors, particularly students of color. As a graduate student I TAed for introductory astronomy courses as well as an observational techniques class in conjunction with McDonald Observatory, which was a lot of fun!

Astronomy on Tap

Astronomy on Tap is an international organization hosting astronomy-themed talks at local venues geared toward the public. Austin once boasted the most widely-attended chapter, where I co-hosted the monthly Astronomy in the News segment. I have given a couple talks on the magic of interferometry, available here. I have reclaimed my title as News Anchor at Tucson Space Drafts as well, so catch me every third Tuesday of the month!

Equity & Inclusion in Astronomy

As a woman in STEM and a global citizen in general, I am passionate about tackling institutional biases and unfair treatment in academia. As part of the ISEE PDP, I worked closely with UH Hilo and the Akamai Workforce Initiative to foster STEM inclusivity amonst Hawai'ian undergraduates. I hope to continue fostering community with the astronomers and citizens of Hawai'i, an important and sacred place which has given us invaluable astronomical insight but also calls upon us with kuleana (responsibility) to respect and learn about native culture and history in Hawai'i. Lastly, I was heavily involved in developing seminars for TAURUS, a former nine-week summer research program designed for URM undergraduates.