Ruprecht-Karls-Universität Heidelberg

Patzer Award for Emily Hunt (LSW) and Reza Ayromlou (ITA)

Dr. Emily Hunt (private communication)

Dr. Mohammadreza Ayromlou (private communication)

The Ernst Patzer Foundation is awarding up to three prizes each year for the best refereed publications by doctoral students and young postdocs at MPIA and ZAH. In 2023, Emily Hunt from LSW and Dr. Mohammadreza Ayromlou from ITA are among the awardees.

Dr. Emily Hunt receives this prize for her paper on Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3 (2023, Astronomy & Astrophysics, Volume 673, id.A114, 31 pp).

Together with her supervisor, priv.Doz. Dr. Sabine Reffert, Emily Hunt conducted the largest search for open clusters to date in Gaia DR3 catalogue data, producing a single homogeneous star cluster catalogue. By applying the HDBSCAN algorithm to recover clusters, she recovered 7167 clusters, 2387 of which are candidate new objects and 4782 of which crossmatch to objects in the literature, including 134 globular clusters. A more stringent cut of their catalogue contains 4105 highly reliable clusters, 739 of which are new. The catalogue includes two quality criteria for every cluster: firstly, based on their significance in Gaia astrometric data; and secondly, based on their compatibility with a single population of stars calculated with an approximate Bayesian neural network. The catalogue also includes age and extinction estimates for every cluster, which they show trace the structure of the Milky Way's disk.

Dr. Mohammadreza Ayromlou was honored with the Patzer Prize for his research paper on Feedback reshapes the baryon distribution within haloes, in halo outskirts, and beyond: the closure radius from dwarfs to massive clusters (2023, Monthly Notices of the Royal Astronomical Society, 524, 5391).

Together with Dr. Dylan Nelson (ZAH/ITA) and Dr. Annalisa Pillepich (MPIA) he introduced the closure radius, a novel characteristic distance from the centers of dark matter haloes, within which all baryons associated with dark matter are located. This was the first study to systematically reveal how feedback processes affect baryon distribution from small to large scales across all galaxy-hosting halo masses. Using three major cosmological simulations—IllustrisTNG, EAGLE, and SIMBA—he showed that feedback redistributes gas, reducing baryon fractions within haloes while accumulating it beyond the halo virial radius. He found that heating from the UV background in low-mass haloes, stellar feedback in intermediate-mass haloes, and black hole feedback in galaxy groups are the dominant processes that redistribute the gas. In contrast, galaxy clusters are closed systems least affected by these. He formulated a universal relation for predicting the closure radius, offering a theoretically reliable, empirically testable, solution to the missing baryon problem in LCDM cosmology.

The award winners will be honored during the Patzer Colloquium on November 24th, 2023, at 15:00 in the MPIA Lecture Hall.

The Scientific Ernst Patzer Foundation was established in 2001 by the widow of the Philosopher Ernst Patzer. The goal of the foundation is to support young scientists in the field of astronomy, in particular at the Max Planck Institute for Astronomy in Heidelberg and ZAH. For more information see

Dr. Emily Hunt
Center for Astronomy of Heidelberg University (ZAH)
Landessternwarte Königstuhl (LSW)

Dr. Mohammadreza Ayromlou
Center for Astronomy of Heidelberg University (ZAH)
Institute for Theoretical Astrophysics (ITA)

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