arXiv subjects

Henrik W. Edler

Publications and source records attributed to Henrik W. Edler.

3 recordsLinked to original sources

arXiv2026

Exploring the physics of ram pressure stripping with radio continuum observations in the SKA era

Satellite galaxies in clusters are significantly more likely to be red and passive than similar mass galaxies in the field. This fact is known as the environmental quenching of galaxy star formation, which is believed to be driven by ram pressure stripping (RPS). The large velocity differences between the infalling galaxies and the intracluster medium (ICM) result in a strong ram pressure on their interstellar medium (ISM), which can strip it from the stellar disk. The stripped ISM can be studied at various wavelengths, including the radio band, thanks to the synchrotron emission produced by the magnetic fields and relativistic electrons embedded in them. This emission is typically steep-spectrum and thus best observed at low frequencies. Thus, continuum studies of the RPS effect are currently mostly carried out with LOFAR, limiting them to the northern hemisphere. SKA-Low will permit us to extend them to the southern sky, where they will synergize with the southern observatories and the upcoming ELT. Lastly, the sub-arcsecond resolution provided by SKA-Mid will facilitate the exploration of the polarization and filamentary structure of RPS radio tails and allow us to detect them up to $z\simeq0.5$, advancing our understanding of the impact of RPS on satellite galaxies in clusters and groups.

astro-ph.GA↗

arXiv2025

Simulating realistic radio continuum survey maps with diffusion models

The next generation of radio surveys is going to be transformative for cosmology and other aspects of our understanding of astrophysics. Realistic simulations of radio observations are essential for the design and planning of radio surveys. They are employed in the development of methods for tasks, such as data calibration and reduction, automated analysis and statistical studies in cosmology. We implemented a software for machine learning-assisted simulations of realistic surveys with the LOFAR telescope, resulting in a synthetic radio sky model and a corresponding artificial telescope observation. We employed a diffusion model trained on LoTSS observations to generate individual radio galaxy images with control over the angular size. Single sources are assembled into a radio sky model, using an input catalog from cosmological simulations. We then transformed this sky model into visibilities corresponding to a typical LoTSS pointing. We added realistic noise to this synthetic measurement and obtained our final simulated sky maps through deconvolution. We explored different ways to evaluate our resulting sky model. We were able to simulate realistic LOFAR observations, covering a sky patch of 5x5 degrees at an effective resolution of 8.5 arcseconds. The simulated sources have flux and size distributions that match real observations, and the resulting maps have sensitivities compatible with LoTSS observations. Our diffusion model is able to synthesize high-quality realistic radio galaxy images with precise control over the source sizes. This software can readily be applied to other instruments.

astro-ph.IM↗

arXiv2024

The SRG/eROSITA All-Sky Survey: View of the Virgo Cluster

As the closest galaxy cluster, the Virgo Cluster is an exemplary environment for the study of the large-scale filamentary structure and physical effects that are present in cluster outskirts but absent from the more easily studied inner regions. Here, we present an analysis of the SRG/eROSITA data from five all-sky surveys. eROSITA allows us to resolve the entire Virgo cluster and its outskirts on scales between 1 kpc and 3 Mpc, covering a total area on the sky of about 25$^\circ$ by 25$^\circ$. We utilized image manipulation techniques and surface brightness profiles to search for extended emission, surface brightness edges, and features in the outskirts. We employed a method of comparing mean and median profiles to measure gas clumping out to and beyond the virial radius. Surface brightness analysis of the cluster and individual sectors of the cluster reveal the full extent of previously identified cold fronts to the north and south. The emissivity bias due to gas clumping, which we quantify over three orders of magnitude in the radial range, is found to be mild, consistent with previous findings. We find uniform clumping measurements in all directions, with no enhancements along candidate filaments. We find an estimated virial gas mass of $M_{\mathrm{gas},r<r_{200}} = (1.98 \pm 0.70) \times 10^{13}$ M$_\odot$. Through imaging analysis we detect the presence of extended emission spanning 320\,kpc to the southwest of M49. The extension has a significance of 3.15$σ$ and is coincident with radio emission detected with LOFAR, which could be evidence of an accretion shock or turbulent reacceleration as the M49 group or background W' cloud falls into the cluster and interacts with the intracluster medium.

astro-ph.CO↗