arXiv subjects

Ralf M. Konietzka

Publications and source records attributed to Ralf M. Konietzka.

5 recordsLinked to original sources

arXiv2026

The CGM with local universe FRBs: evidence of strong AGN feedback in a massive elliptical galaxy

Modern cosmology and galaxy formation rely on an understanding of how cosmic baryons are distributed, a significant portion of which exist in the diffuse gas confined to halos. Fast Radio Bursts (FRBs) are a promising probe of the Universe's ionized gas. At low redshift, the contribution to the dispersion measure (DM) from the intergalactic medium (IGM) and intervening halos is subdominant, allowing us to study the circumgalactic media (CGM) of the host galaxies, if the host interstellar medium (ISM) can be sufficiently suppressed. We select a sample of five local universe FRBs with host halos spanning a wide range in mass ($\sim10^{11-13}\,M_\odot$), and with indicators that host ISM DM is negligible. We use these FRBs to constrain the CGM in each halo by comparing to simulations and measuring the CGM mass assuming a range of spherical gas profiles. We find one of our sources, the only massive elliptical host galaxy, strongly disfavors low feedback scenarios in simulations, and has been evacuated of its baryons ($\sim\,10\%$ of the cosmological average $\frac{Ω_b}{Ω_m}$ within $R_\mathrm{vir}$). This galaxy shows evidence of a past episode of AGN activity, consistent with the picture of strong AGN feedback in galaxy group-scale halos. The gas mass measurements for the other sources tentatively support more baryon retention in $L_*$ galaxies compared to group-scale halos. Finally, we demonstrate that a large sample of local universe FRBs will enable precision measurements of halo gas.

astro-ph.GA↗

arXiv2026

A New Model for the Milky Way Halo Dispersion Measure with the ENGAWA Simulations: Low DMs and Large Anisotropy

Fast radio burst (FRB) dispersion measures (DMs) are powerful tracers of the low density universe, but interpretation is made difficult by the integrated nature of DM. In this paper, we analyze the new ENGAWA cosmological zoom-in simulation suite to constrain the DM contribution from the Milky Way (MW) halo. The ENGAWA simulations consist of four Milky Way-like galaxies with enhanced resolution in the circumgalactic medium, making them an excellent tool to probe the properties of the gaseous halo. The median all-sky DM from the galactic halos in ENGAWA span 19-39 pc cm$^{-3}$, varying even at fixed feedback strength, halo mass, and $f_\mathrm{CGM}$. These simulations show that, with enhanced circumgalactic resolution, the mean halo DM values are in general lower with more anisotropy across the sky than previous models, reaching < 10 pc cm$^{-3}$ towards the poles. Furthermore, by varying the solar position within the simulated galaxies, we have obtained an estimate of the uncertainty in DM given our location in the MW. We provide a Python package with MW halo DM values from the simulation accessible via API functions of Galactic longitude and latitude. These new, simulation-based MW halo DM estimates will provide a critical baseline for interpretations of future FRB observations and our understanding of the global gas distribution in the Universe.

astro-ph.GA↗

arXiv2025

Ray-tracing Fast Radio Bursts Through IllustrisTNG: Cosmological Dispersion Measures from Redshift 0 to 5.5

The dispersion measures (DMs) of Fast Radio Bursts (FRBs) arise predominantly from free electrons in the large-scale structure of the Universe. The increasing number of FRB observations have started to empirically constrain the distribution of cosmic baryons, making it crucial to accurately forward model their propagation within cosmological simulations. In this work, we present a method for measuring FRB DMs in IllustrisTNG that continuously traces rays through the simulation while reconstructing all traversed line segments within the underlying Voronoi mesh. Leveraging this technique, we create over $20$ publicly available DM catalogs, including a full-sky DM map observed from a Milky Way-like environment. Our method addresses a problem in previous TNG-based studies, in which a sparse snapshot sampling in the path integral leads to a misestimation of the standard deviation and higher moments of the DM distribution $p(\rm{DM}|z)$ by over $50\%$. We show that our results are consistent with the most recent observational data from the DSA-110, ASKAP, and CHIME. We offer a functional form for $p(\rm{DM}| z)$ that provides very good fits across all redshifts from $0$ to $5.5$, showing that the previously proposed log-normal distribution is not well matched to the data. We find that using simulation box sizes smaller than $35\,h^{-1}\,$Mpc or resolutions with baryonic masses of less than $5\times10^{8}\,h^{-1}\,M_{\odot}$ can distort the derived DM signal by more than $8\%$. Our findings provide new insights into how the cosmic web shapes FRB signals, and highlight the importance of accurate methodology when comparing cosmological simulations against observations.

astro-ph.CO↗

arXiv2025

A gas-rich cosmic web revealed by the partitioning of the missing baryons

Approximately half of the Universe's dark matter resides in collapsed halos; significantly less than half of the baryonic matter (protons and neutrons) remains confined to halos. A small fraction of baryons are in stars and the interstellar medium within galaxies. The lion's share are diffuse ($<$10$^{-3}$ cm$^{-3}$) and ionized (neutral fraction $<$10$^{-4}$), located in the intergalactic medium (IGM) and in the halos of galaxy clusters, groups, and galaxies. This diffuse ionized gas is notoriously difficult to measure, but has wide implications for galaxy formation, astrophysical feedback, and precision cosmology. Recently, the dispersion of extragalactic Fast Radio Bursts (FRBs) has been used to measure the total content of cosmic baryons. Here, we present a large cosmological sample of FRB sources localized to their host galaxies. We have robustly partitioned the missing baryons into the IGM, galaxy clusters, and galaxies, providing a late-Universe measurement of the total baryon density of $Ω_b\,h_{70} = 0.051_{-0.006}^{+0.006}$. Our results indicate efficient feedback processes that can deplete galaxy halos and enrich the IGM ($f_{\rm IGM}=0.76_{-0.11}^{+0.10}$), agreeing with the baryon-rich cosmic web scenario seen in cosmological simulations. Our results may reduce the ``$S_8$ tension'' in cosmology, as strong feedback leads to suppression of the matter power spectrum.

astro-ph.CO↗

arXiv2025

A Correlation Between FRB Dispersion Measure and Foreground Large-Scale Structure

The distribution of baryons in the Universe remains a fundamental open question in astronomy, and the dispersion measure (DM) of Fast Radio Bursts (FRBs) serves as a valuable tool for probing this cosmic gas. We investigate the impact of the foreground cosmic web on FRB DMs using 61 localized FRBs and public galaxy catalogs. We test for the large-scale structure's impact on cosmological DM using two methods. First, we searched for a correlation between galaxy number density along the line of sight and extragalactic DM, and found a statistically significant positive correlation ($p$ = $1.76 \times 10^{-5}$). The shape of this correlation contains information about the cosmic baryon distribution, and can also be used to better constrain host galaxy DM by providing an estimate of the cosmic contribution on a per-source basis. We observe similar correlations in a mock FRB survey based on the IllustrisTNG cosmological simulation, where the DM is dominated by filaments in the IGM and not by halos. Next, we performed a stacking analysis that measures the average excess DM as a function of impact parameter of foreground galaxies to obtain spatial information about how ionized gas is distributed around galaxy halos. We report excess DM in the stacked signal for impact parameters up to Mpc scales ($\sim$3$σ$). Finally, we identified FRBs that do not appear to intersect intervening halos within $r_{vir}$, allowing us to estimate the fraction of baryons that reside in the IGM. We find $f_{\mathrm{IGM}} \geq 0.69$ at 95$\%$ confidence, indicating significant astrophysical feedback.

astro-ph.CO↗