FredJenningsAstro

Dr. Fred J. Jennings

Hi there! I am a computational astrophysicist from the UK. I hold a Masters’ degree in Astrophysics from the University of Cambridge, and a PhD in Computational Astrophysics from the University of Edinburgh. I currently work at UNIMORE, Italy as a Computational Research Fellow. I am primarily interested in Massively-Parallel Simulations and Numerical Methods applied to Multiphase and Magnetised Flows, Active Galactic Nuclei, Galaxy Groups & Clusters, and Galaxy Formation. I am always interested in applying my expertise to new research areas and collaborating with diverse groups of scientists. You can currently reach me at Fred.Jennings@unimore.it

Publications
CV
Clockwise from left I show the density, entropy, and radial velocity for a large galaxy group of mass 10^13.8 solar masses from the Hyenas suite of simulations. Inset is a mock Chandra ACIS mosaic, roughly 200 kiloparsecs across, showing bipolar cavities similar to those seen in larger halos e.g. RBS 797, MS 0735+7421, and Perseus
In Jennings et. al 2023 we showed how including magnetic fields of different strengths and orientations can affect the evolution of cold clumps in the ICM. In the above plot is a comparison of the magnetic field structure inside such a clump after evolving for the same amount of time within a 1-microGauss field (left) and a 5 microGauss field (right)
Some observed cavities from our Hyenas groups sample, left showing smoothed flux and right showing unsharp-masked maps. These cavities are inflated by AGN jets simulated with the Simba model, and match observed cavities in size, radius from the BCG, and eccentricity.
A short volume-rendered movie over 200 Megayears of the same Hyenas galaxy group shown above, now with yellow, maroon, and blue highlighting hot, warm, and cold gas. The jet is seen to reorient and entrain cold fluid in outflows.
We show for the first time that the feedback model in a cosmological simulation can produce cavities which overheat group-scale halos relative to radiative losses, with an excellent match to observations
Volume renderings of hot (upper left), cold (upper right) gas, and streamlines of the magnetic field (lower left) and gas momentum (lower right) for a simple cluster jet set-up in AthenaPK. I used PyVista to generate this plot.
A sub-sample of the halos for which I produced fully-mocked observations using pyXSIM and SOXS for our Jennings, Dave et. al. 2023 paper.
The cleaning procedure we used in Jennings et. al. 2023 is demonstrated for a single halo. Cosmic X-ray Background sources are removed through this technique leaving just ICM emission.

In Jennings et. al. 2023 we showed how you can fully mock the full procedure for measuring halo masses using hydrostatic equilibrium, and calculated halo mass biases in Simba in this way. In addition to measuring pressure via de-projected X-ray profiles from spectral-fitting, we also tested mass-weighting and two types of emmision-weighting. We find that using fully-mocked X-ray derived radial profiles gives a similar mass bias to the emission-weighted method, but this is around twice the value obtained from mass-weighted profiles, which are typically employed by simulators. This has important consequences for both simulators and observers wishing to derive halo masses in this way, for instance for cosmological surveys.

Research Topics

Broadly, I am interested in the following topics…

Role of Multiphase Gas in Galaxy Evolution

How much gas can condense due to local thermal instabilities in the IGrM/ICM? What can trigger this? What size and volume filling distribution does it have? How does it evolve and impact galaxy and black hole evolution?

AGN Feedback and heating

How do jets from supermassive black holes inflate cavities, drive shocks, and heat the Intra-halo gas?

Mock Observations

How can we make the best possible comparisons between what our simulations and telescopes are telling us?

Satellite Population

How is the satellite population in massive halos influenced by things like the passage of X-ray cavities and turbulence stirred by AGN?

Protoclusters

How do the most massive bound structures in the Universe look and behave during their infancy?

Upcoming X-ray missions

What will the next generation of X-ray observatories like Athena and LEM tell us about hot baryons in the Universe?