arXiv subjects

Daudi Mazengo

Publications and source records attributed to Daudi Mazengo.

2 recordsLinked to original sources

arXiv2026

Circumgalactic medium depletion drives satellite quenching in IllustrisTNG

Satellite galaxies dominate the quenched population at low stellar masses ($M_\star \lesssim 10^{10}~\rm M_\odot$), yet identifying which processes shut down their star formation, their relative importance, and on what timescales, remains a central problem in galaxy evolution. We use MaNGA-like mock galaxies from IllustrisTNG to dissect different satellite quenching pathways, paying special attention to the role of the circumgalactic medium (CGM) during quenching phase. We reconstruct the baryonic, dark matter, structural, and chemical histories of $\sim$7 300 galaxies (2 800 satellites), using time since infall as the physical axis along which quenching unfolds. Satellites retain rotation-supported stellar kinematics throughout quenching, with disturbed velocity fields confined to systems with $M_\star \lesssim 10^{10.5}~\rm M_\odot$. For the first time, we present the coupled time evolution of the depletion of both the hot and cool gas reservoirs after infall: satellites lose $\sim$90% of their hot CGM within $\sim$$4.2^{+0.6}_{-0.6}$ Gyr, increasing with residence time and independent of stellar mass. The hot gas mass correlates strongly with SFR, establishing the CGM as the long-term fuel reservoir, unlike quenched centrals, which retain massive hot halos likely maintained by AGN feedback. Present-day quenched satellites were accreted earlier than star-forming ones (6.5$^{+0.3}_{-0.3}$ vs. 4.3$^{+0.3}_{-0.3}$ Gyr ago), forming stars for at least $\sim$3 Gyr after infall before declining sharply, consistent with a delayed-then-rapid quenching scenario. Losing little stellar mass, yet with their gas depleted and their dark matter and metal-poor stellar outskirts tidally stripped, satellites emerge more compact and metal-rich than centrals at fixed mass. Our results suggest the gradual erosion of the hot CGM as the key link connecting infall to the slow shutdown of star formation.

astro-ph.GA↗

arXiv2026

Baryonic assembly bias in X-ray-selected galaxy groups and clusters: insights from the Magneticum simulation

Galaxy groups and clusters trace the large-scale matter distribution, with their clustering usually interpreted mainly as a function of halo mass. Yet, at fixed mass, their baryonic properties retain information about halo growth, gas accretion, and feedback. The intrinsic scatter in X-ray luminosity and gas fraction suggests that X-ray-selected systems may not be a random subset of the halo population. If these observables correlate with halo assembly, they may trace secondary variations in halo bias. We test this using the Magneticum hydrodynamical simulation, measuring the clustering of systems selected by X-ray luminosity and gas fraction at fixed halo mass. We construct mass-matched subsamples by ranking halos in percentiles of X-ray luminosity and derive the linear halo-matter bias from the halo-matter cross-power spectrum. X-ray-bright halos are more strongly clustered than X-ray-faint halos at fixed mass. For the 84th-16th percentile split, we find $\Delta b_{\rm lin}=0.17\pm0.03$, corresponding to a $\sim17\%$ enhancement relative to the X-ray-faint sample. A 67th-33rd split gives a consistent signal, with $\Delta b_{\rm lin}=0.12\pm0.02$ and a $\sim12\%$ enhancement. The effect is strongest at group scales and negligible for cluster-size halos. Gas fraction shows an even stronger clustering dependence, with relative enhancements of $\sim39\%$ and $\sim26\%$ for the two percentile splits. This signal is present from $z\simeq2$, whereas X-ray luminosity becomes significant only at $z\simeq0.3$, once the gas thermodynamic state is more closely coupled to baryon retention. Matching halos by both mass and formation time reduces the large-scale bias difference to below $2\sigma$, indicating that formation time captures much of the signal. These results show that, in Magneticum, X-ray luminosity traces a baryonic manifestation of halo assembly bias beyond mass.

astro-ph.CO↗