Galaxy formation and evolution

Abstract:

Constrained cosmological simulations play an important role in modelling the local Universe, enabling investigation of the dark matter content of local structures and their formation. We introduce an internal method for quantifying the extent to which the variance of individual halo properties is suppressed by the constraints imposed on the initial conditions. We apply it to the Constrained Simulations in BORG (CSiBORG) suite of 101 high-resolution realizations across the posterior probability distribution of initial conditions from the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm. The method is based on the overlap of the initial Lagrangian patch of a halo in one simulation with those in another, measuring the degree to which the haloes' particles are initially coincident. This addresses the extent to which the imposed large-scale structure constraints reduce the variance of individual halo properties. We find consistent reconstructions of M≳1014M⊙h-1 haloes, indicating that the constraints from the BORG algorithm are sufficient to pin down the masses, positions, and peculiar velocities of clusters to high precision, though we do not assess how well they reproduce observations of the local Universe. The effect of the constraints tapers off towards lower mass, and the halo spins and concentrations are largely unconstrained at all masses. We document the advantages of evaluating halo consistency in the initial conditions and describe how the method may be used to quantify our knowledge of the halo field given galaxy survey data analysed through the lens of probabilistic inference machines such as BORG.

Abstract:

We conduct a systematic search for high-redshift galaxy overdensities at 4.9 < z spec < 8.9 in both the Great Observatories Origins Deep Survey (GOODS)-N and GOODS-S fields using James Webb Space Telescope/Near-Infrared Camera (JWST/NIRCam) imaging from the JWST Advanced Deep Extragalactic Survey and JWST Extragalactic Medium-band Survey in addition to JWST/NIRCam wide field slitless spectroscopy from the First Reionization Epoch Spectroscopic Complete Survey. High-redshift galaxy candidates are identified using Hubble Space Telescope + JWST photometry spanning λ = 0.4–5.0 μm. We confirmed the redshifts for roughly a third of these galaxies using JWST spectroscopy over λ = 3.9–5.0 μm through identification of either Hα or OIIIλ5008 around the best-fit photometric redshift. The rest-ultraviolet magnitudes and continuum slopes of these galaxies were inferred from the photometry: the brightest and reddest objects appear in more dense environments and thus are surrounded by more galaxy neighbors than their fainter and bluer counterparts, suggesting accelerated galaxy evolution within overdense environments. We find 17 significant (δ gal ≥ 3.04, N gal ≥ 4) galaxy overdensities across both fields (seven in GOODS-N and 10 in GOODS-S), including the two highest redshift spectroscopically confirmed galaxy overdensities to date at zspec=7.954 and zspec=8.222 (representing densities around ∼6 and ∼12 times that of a random volume). We estimate the total halo mass of these large-scale structures to be 11.5≤log10Mhalo/M⊙≤13.4 using an empirical stellar mass-to-halo mass relation, which are likely underestimates as a result of incompleteness. These protocluster candidates are expected to evolve into massive galaxy clusters with log10Mhalo/M⊙≳14 by z = 0.

Abstract:

One of the more surprising findings after the first year of JWST observations is the large number of spatially extended galaxies (ultrared flattened objects, or UFOs) among the optically faint galaxy (OFG) population otherwise thought to be compact. Leveraging the depth and survey area of the JWST Advanced Deep Extragalactic Survey, we extend observations of the OFG population to an additional 112 objects, 56 of which are well-resolved in F444W with effective sizes, R e > 0.″25, more than tripling previous UFO counts. These galaxies have redshifts around 2 < z < 4, high stellar masses ( log(M*/M⊙)∼10–11 ), and star formation rates around ∼100–1000 M ⊙ yr−1. Surprisingly, UFOs are red across their entire extents, which spatially resolved analysis of their stellar populations shows is due to large values of dust attenuation (typically A V > 2 mag even at large radii). Morphologically, the majority of our UFO sample tends to have low Sérsic indices (n ∼ 1) suggesting that these large, massive, OFGs have little contribution from a bulge in F444W. Further, a majority have axis ratios between 0.2 < q < 0.4, which Bayesian modeling suggests that their intrinsic shapes are consistent with being a mixture of inclined disks and prolate objects with little to no contribution from spheroids. While kinematic constraints will be needed to determine the true intrinsic shapes of UFOs, it is clear that an unexpected population of large, disky or prolate objects contributes significantly to the population of OFGs.