Galaxy formation and evolution

Abstract:

The frequency of compact object interactions in AGN discs is naturally tied to the number of objects embedded within it. We investigate the evolution of black holes in the nuclear stellar cluster on inclined orbits to the AGN disc by performing adiabatic hydrodynamical simulations of isolated black hole disc crossings over a range of disc densities and inclinations . We find radiation dominates the pressure in the wake that forms around the BH across the full inclination and disc density range. We identify no well defined steady state wake morphology due to the thin geometry of the disc and the vertical exponential density drop off, where the wake morphology depends on the vertical depth of the transit within the disc. The inclination damping relative the pre-transit inclination behaves as a power law in and the ambient Hill mass as . The drag on the BH is dominated by the gravity of the wake for the majority of our inclination range until accretion effects become comparable at , where is the disc aspect ratio. At low inclinations () the wake morphology becomes more spherical, leading to a regime change in the inclination damping behaviour. Our results suggest that the inclination damping time-scale is shorter than expected from only episodic Bondi–Hoyle–Lyttelton accretion events during each transit, implying inclined objects may be captured by the AGN disc earlier in its lifetime than previously thought.

Abstract:

We present a detailed kinematic study of a sample of 32 massive (9.5 ⩽ log(M */M⊙) ⩽ 10.9) main sequence star-forming galaxies (MS SFGs) at 4 < z < 6 from the ALMA-CRISTAL programme. The data consist of deep (up to 15 hr observing time per target), high-resolution (∼1 kpc) ALMA observations of [C II]158 μm line emission. This dataset allowed us to carry out the first systematic, kiloparsec-scale (kpc-scale) characterisation of the kinematics nature of typical massive SFGs at these epochs. We find that ∼50% of the sample are disk-like, with a number of galaxies located in systems of multiple components. Kinematic modelling reveals these main sequence disks exhibit high-velocity dispersions (σ 0), with a median disk velocity dispersion of ∼70 km s⁻¹ and V rot/σ 0 ∼ 2, which is consistent with dominant gravity driving. The elevated disk dispersions are in line with the predicted evolution based on Toomre theory and the extrapolated trends from z ∼ 0–2.5 MS star-forming disks. The inferred dark matter (DM) mass fraction within the effective radius f DM(< R e) for the disk systems decreases with the central baryonic mass surface density. This is consistent with the trend reported by kinematic studies at z ≲ 3; roughly half the disks display f DM(< R e)≲ 30%. The CRISTAL sample of massive MS SFGs provides a reference of the kinematics of a representative population and extends the view onto typical galaxies beyond previous kpc-scale studies at z ≲ 3.

Abstract:

Time-delay distance measurements from strongly lensed quasars provide a robust and independent method for determining the Hubble constant (H0). This approach offers a crucial cross-check against H0 measurements obtained from the standard distance ladder in the late Universe and the cosmic microwave background in the early Universe. The mass-sheet degeneracy in strong-lensing models may introduce a significant systematic uncertainty, however, that limits the precision of H0 estimates. Dynamical modeling complements strong lensing very well to break the mass-sheet degeneracy because both methods model the mass distribution of galaxies, but rely on different sets of observational constraints. We developed a method and software framework for an efficient joint modeling of stellar kinematic and lensing data. Using simulated lensing and kinematic data of the lensed quasar system RXJ1131−1131 as a test case, we demonstrate that a precision of approximately 4% on H0 can be achieved with high-quality data that have a high signal-to-noise ratio. Through extensive modeling, we examined the impact of a supermassive black hole in the lens galaxy and potential systematic biases in kinematic data on the H0 measurements. Our results demonstrate that either using a prior range for the black hole mass and orbital anisotropy, as motivated by studies of nearby galaxies, or excluding the central bins in the kinematic data can effectively mitigate potential biases on H0 induced by the black hole. By testing the model on mock kinematic data with values that were systematically biased, we emphasize that it is important to use kinematic data with systematic errors below the subpercent level, which can currently be achieved. Additionally, we leveraged GPU parallelization to accelerate the Bayesian inference. This reduced a previously month-long process by an order of magnitude. This pipeline offers significant potential for advancing cosmological and galaxy evolution studies with large datasets.

Abstract:

Context. Baryonic physics has a considerable impact on the distribution of matter in our Universe on scales probed by current and future cosmological surveys, acting as a key systematic in such analyses. Aims. We seek simple symbolic parametrisations for the impact of baryonic physics on the matter power spectrum for a range of physically motivated models, as a function of wavenumber, redshift, cosmology, and parameters controlling the baryonic feedback. Methods. We used symbolic regression to construct analytic approximations for the ratio of the matter power spectrum in the presence of baryons to that without such effects. We obtained separate functions of each of four distinct sub-grid prescriptions of baryonic physics from the CAMELS suite of hydrodynamical simulations (Astrid, IllustrisTNG, SIMBA, and Swift-EAGLE) as well as for a baryonification algorithm. We also provide functions that describe the uncertainty on these predictions, due to both the stochastic nature of baryonic physics and the errors on our fits. Results. The error on our approximations to the hydrodynamical simulations is comparable to the sample variance estimated through varying initial conditions, and our baryonification expression has a root mean squared error of better than one percent, although this increases on small scales. These errors are comparable to those of previous numerical emulators for these models. Our expressions are enforced to have the physically correct behaviour on large scales and at high redshift. Due to their analytic form, we are able to directly interpret the impact of varying cosmology and feedback parameters, and we can identify parameters that have little to no effect. Conlcusions. Each function is based on a different implementation of baryonic physics, and can therefore be used to discriminate between these models when applied to real data. We provide a publicly available code for all symbolic approximations found.