Institut d'Astrophysique de Paris

Early onset of the hot circumgalactic medium around Milky Way galaxies

Abstract Hot coronae are key regulators in Milky Way (MW)-type galaxy formation and are thought to emerge once a galaxy’s dark matter halo crosses a critical mass threshold, Mvir ~ 1012 M⊙, so that accretion shocks can heat infalling gas to virial temperatures, Tvir. Here we inve...

Novel geometrical test of cosmological expansion from photometric data

In tomographic cosmic-shear observations, the Bernardeau, Nishimichi, Taruya (BNT) transform allows us to build weak lensing transformed maps for which the contribution from low-redshift lenses is nulled. As this transformation depends specifically on the expansion rate of the Un...

The Composite Spectrum of QSO Absorption Line Systems in DESI DR2

Abstract We present details regarding a composite spectrum of quasar (QSO) absorption line systems. In this composite spectrum, we identify more than 70 absorption lines and observe oxygen and hydrogen emission features at a higher signal-to-noise ratio than any previous study. A...

MEGATRON: Reproducing the Diversity of High-Redshift Galaxy Spectra with Cosmological Radiation Hydrodynamics Simulations

We present the MEGATRON suite of cosmological radiation hydrodynamics simulations following the formation of Milky Way-mass galaxies from the earliest cosmic epochs when Population III stars form to Cosmic Noon. The suite represents the first set of cosmological simulations that...

MEGATRON: how the first stars can create an iron metallicity plateau in the smallest dwarf galaxies

We study the stellar mass-iron metallicity relation of dwarf galaxies in the new high-resolution MEGATRON cosmological radiation-hydrodynamics simulations. These simulations model galaxy formation up to z ≈ 8 in a region that will collapse into a Milky-Way-like galaxy at z = 0 ,...

MEGATRON: the impact of non-equilibrium effects and local radiation fields on the circumgalactic medium at cosmic noon

We present three cosmological radiation-hydrodynamic zoom simulations of the progenitor of a Milky Way-mass galaxy from the MEGATRON suite. The simulations combine on-the-fly radiative transfer with a detailed non-equilibrium thermochemical network (81 ions and molecules), resolv...

Extreme Values of Black-hole-to-stellar-mass Ratio for High-redshift Galaxies

Abstract With recent data from the James Webb Space Telescope (JWST), it is possible to calculate the mass of the supermassive black holes at the center of galaxies and the stellar mass of the host galaxies at redshift z ≳ 5. In this work, we apply extreme-value statistics to cal...

TESS Observations of Stochastic Low-frequency Variability in Extreme Helium Stars

Abstract Extreme helium stars (EHes) are low-mass hydrogen-deficient stars thought to be the products of double white dwarf mergers. Despite prolonged ground-based observations, there is no consensus on the properties of their photometric variability. In this article, we present...

Episodic super-Eddington accretion as a clue to Overmassive Black Holes in the early Universe

Abstract Early JWST observations are providing growing evidence for a ubiquitous population of accreting supermassive black holes (BHs) at high redshift, many of which appear overmassive compared to the empirically-derived local scaling relation between black hole mass and host g...

ODIN: Confirmation and 3D Reconstruction of Six Massive Protoclusters at Cosmic Noon

Abstract Protoclusters represent sites of accelerated galaxy formation and extreme astrophysical activity characteristic of dense environments. Identifying massive protoclusters and mapping their spatial structures are therefore crucial for understanding how large-scale environme...

Zippers and Twisters: Planes of Satellite Galaxies Emerge from Whirling and Shocking Gas Streams in the Cosmic Web

Abstract We investigate dwarf satellite systems around massive centrals analogs (Milky Way to Centaurus A) in the NewHorizon simulation. Using simple estimators limiting overdetection, we identify planes of satellites comparable to observations in 30%–70% of cases. The full sampl...