Credit: NASA, ESA, CSA, S. Lilly (ETH Zurich), D. Kashino (Nagoya University), J. Matthee (ETH Zurich), C. Eilers (MIT), R. Simcoe (MIT), R. Bordoloi (MIT), R. Mackenzie (ETH Zurich), A. Pagan (STScI)
Julien Wolf portrait

Julien Wolf

Observational Astronomer · Quasar Hunter · Early-Universe Enthusiast

Welcome to my website. I am a postdoctoral researcher at the European Southern Observatory (ESO) in Garching, Germany.

My Research

focuses on understanding how the first supermassive black holes formed, grew, and influenced their environments during the first billion years of cosmic history. I approach this problem by searching for and characterizing their most extreme incarnation: distant luminous quasars and their host galaxies.

Integral-Field Spectroscopy of High-Redshift Quasars

Using JWST/NIRSpec IFU data, I study the gas, kinematics, and feedback processes surrounding quasars at cosmic dawn. My work includes the development of custom JWST reduction pipelines and PSF subtraction tools, enabling discoveries such as the first extremely metal-poor Balmer shell around the most distant known quasar and the first spectroscopic evidence of jet-induced star formation at z ∼ 6 (Wolf et al. 2025 submitted, Wolf et al. in prep.).

High-Redshift Quasar Discovery

Using deep-learning and more traditional photometric methods, I search for extremely rare quasars in large survey datasets including Euclid and eROSITA. This work has led to the discovery of some of the most luminous and unusual high-redshift AGN known, including a distant blazar and a radio-loud BAL quasar (Wolf et al. 2024). I am part of Euclid's core z > 7 discovery team and PI of a large HST programme (SNAP, 125 orbits) dedicated to confirming faint Euclid quasar candidates beyond the current redshift frontier.

X-ray Studies of AGN and Population Evolution

My PhD research used the eROSITA all-sky survey to study the X-ray properties of the earliest quasars, providing the first constraints on the X-ray luminosity function and black-hole accretion-rate density at z ∼ 6 (Wolf et al. 2021, 2023).

About me

I am an observational astrophysicist studying supermassive black holes in the early universe. After my Bachelor's and Master's studies in physics and astrophysics at the Ludwig-Maximilians-Universität München (DE), I joined the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching (DE) as a PhD student in 2019. Under the supervision of Dr. Mara Salvato and Prof. Kirpal Nandra, I worked on the discovery and characterization of high-redshift quasars using the soft X-ray telescope eROSITA. My doctoral thesis, Tracing the Evolution of Supermassive Black Holes through Cosmic Time with Luminous AGN (graded 0.88, Magna Cum Laude, 2023), is available here.

In Spring 2023, I moved to the Max Planck Institute for Astronomy (MPIA) in Heidelberg (DE) for my first postdoctoral appointment in Dr. Eduardo Bañados' group. Since July 2026, I have been a postdoctoral researcher at the European Southern Observatory (ESO) in Garching (DE), working with Dr. Vincenzo Mainieri on AGN feedback and the interaction between supermassive black holes and their host galaxies. My research spans the discovery of very distant quasars with Euclid, their multi-wavelength characterization, and the spatially resolved study of their environments using JWST/NIRSpec integral-field spectroscopy.

My scientific work sits at the intersection of multi-wavelength survey catalog exploration, state-of-the-art spectroscopic and imaging techniques, and advanced data analysis. I have broad expertise ranging from JWST IFU data reduction and PSF modeling to X-ray spectral analysis and deep-learning-based rare-object discovery. My guiding principle: use every waveband and method available to push the observational frontiers of the early universe. I am an active member of several international collaborations, including the Euclid Consortium (Primeval Universe SWG), EREBUS, AETHER, eROSITA (AGN working group), NewAthena, and SDSS-V.

When I'm not working with telescopes, I enjoy cooking (in pursuit of the perfect shoyu ramen), enduro mountainbiking, writing loud music, collecting vinyl records, and most of all spending time with my family and my dog.

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CV and publication record

You can find my up-to-date CV here.

ADS record of all contributions

ORCID iD 0000-0003-0643-7935

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Contact.

You can contact me at julien.wolf (at) eso.org.