3 results
Search Results
Now showing 1 - 3 of 3
- ItemA Multiwavelength Dynamical State Analysis of ACT-CL J0019.6+0336(Basel : MDPI, 2021) Pillay, Denisha S.; Turner, David J.; Hilton, Matt; Knowles, Kenda; Kesebonye, Kabelo C.; Moodley, Kavilan; Mroczkowski, Tony; Oozeer, Nadeem; Pfrommer, Christoph; Sikhosana, Sinenhlanhla P.; Wollack, Edward J.In our study, we show a multiwavelength view of ACT-CL J0019.6+0336 (which hosts a radio halo), to investigate the cluster dynamics, morphology, and ICM. We use a combination of XMM-Newton images, Dark Energy Survey (DES) imaging and photometry, SDSS spectroscopic information, and 1.16 GHz MeerKAT data to study the cluster properties. Various X-ray and optical morphology parameters are calculated to investigate the level of disturbance. We find disturbances in two X-ray parameters and the optical density map shows elongated and axisymmetric structures with the main cluster component southeast of the cluster centre and another component northwest of the cluster centre. We also find a BCG offset of ~950 km/s from the mean velocity of the cluster, and a discrepancy between the SZ mass, X-ray mass, and dynamical mass (MX,500 and MSZ,500 lies > 3σ away from Mdyn,500), showing that J0019 is a merging cluster and probably in a post-merging phase.
- ItemTurning AGN Bubbles into Radio Relics with Sloshing: Modeling CR Transport with Realistic Physics(Basel : MDPI, 2021) ZuHone, John; Ehlert, Kristian; Weinberger, Rainer; Pfrommer, ChristophRadio relics are arc-like synchrotron sources at the periphery of galaxy clusters, produced by cosmic-ray electrons in a µG magnetic field, which are believed to have been (re-)accelerated by merger shock fronts. However, not all relics appear at the same location as shocks as seen in the X-ray. In a previous work, we suggested that the shape of some relics may result from the pre-existing spatial distribution of cosmic-ray electrons, and tested this hypothesis using simulations by launching AGN jets into a cluster atmosphere with sloshing gas motions generated by a previous merger event. We showed that these motions could transport the cosmic ray-enriched material of the AGN bubbles to large radii and stretch it in a tangential direction, producing a filamentary shape resembling a radio relic. In this work, we improve our physical description for the cosmic rays by modeling them as a separate fluid which undergoes diffusion and Alfvén losses. We find that, including this additional cosmic ray physics significantly diminishes the appearance of these filamentary features, showing that our original hypothesis is sensitive to the modeling of cosmic ray physics in the intracluster medium.
- ItemLYRA. III. The Smallest Reionization Survivors(London : Institute of Physics Publ., 2022) Gutcke, Thales A.; Pfrommer, Christoph; Bryan, Greg L.; Pakmor, Rüdiger; Springel, Volker; Naab, ThorstenThe dividing line between galaxies that are quenched by reionization ("relics") and galaxies that survive reionization (i.e., continue forming stars) is commonly discussed in terms of a halo mass threshold. We probe this threshold in a physically more complete and accurate way than has been possible to date, using five extremely high resolution (Mtarget = 4 M⊙) cosmological zoom-in simulations of dwarf galaxies within the halo mass range (1–4) × 109 M⊙. The employed LYRA simulation model features resolved interstellar medium physics and individual, resolved supernova explosions. Interestingly, two out of five of the simulated dwarf galaxies lie close to the threshold mass but are neither full reionization relics nor full reionization survivors. These galaxies initially quench at the time of reionization but merely remain quiescent for ∼500 Myr. At z ∼ 5 they recommence star formation in a synchronous way and remain star-forming until the present day. The parallel timing indicates consistent sound-crossing and cooling times between the halos. While the star formation histories we find are diverse, we show that they are directly related to the ability of a given halo to retain and cool gas. Whereas the latter is most strongly dependent on the mass (or virial temperature) of the host halo at the time of reionization, it also depends on its growth history, the UV background (and its decrease at late times), and the amount of metals retained within the halo.