Galaxy formation and evolution

Abstract:

The James Webb Space Telescope (JWST) has extended the frontier of galaxy detection to redshifts z > 11, finding a high abundance of UV-bright sources that challenge theoretical models. However, most current results come from just a few fields, introducing uncertainties due to cosmic variance. Here, we constrain z ∼ 7–14 UV luminosity functions (LFs) over ∼400 arcmin2 across 36 independent sight lines from Data Release 2 of BEACON, a JWST pure-parallel NIRCam multiband imaging survey. We identify 164 7 < z < 12 galaxy candidates: 150 F090W, 14 F115W, and no robust F150W dropouts. In the 11 pointings overlapping with public JWST spectroscopy, we find no contaminants, indicating a high purity in our sample. Our z ∼ 7.5 UV LF agrees with previous bright-end measurements but yields lower number densities at −21 ≤ MUV ≤ −19. At z ∼ 10, our measurements are lower than most photometric JWST results but match spectroscopic constraints, consistent with the high purity of our selection. The LFs at z ∼ 7.5 and 10 are consistent with pre-JWST models, while our limits at z > 13 do not rule out a possible excess. We measure significant clustering of bright (MUV < −20.5) galaxies at 7 < z < 10. Fields hosting such sources are approximately 3 times more likely to be overdense relative to the full survey, implying that UV-bright galaxies preferentially reside in the most massive halos at these redshifts. Comparing with seminumerical simulations, we estimate that MUV < −20.5 galaxies inhabit halos ∼0.8 dex less massive at z ∼ 11 than at z ∼ 8, consistent with a shift to higher star formation rates. However, their observed clustering exceeds predictions from pre-JWST luminosity–halo mass relations, suggesting these sources reside in more massive halos than previously modelled and/or multiple halo occupation.

Abstract:

We present the star formation and dust content properties for a sample of 646 galaxies at redshifts 3 < z < 7 as part of the JADES survey. Our analysis is based on measurements of the Hα/Hβ Balmer decrement using medium resolution (R ∼ 1000) spectroscopic observations with the JWST/NIRSpec microshutter assembly. Stellar masses and star formation rates (SFRs) are inferred with Prospector using deep multiband imaging. We utilize the Balmer decrement to measure dust-corrected Hα-based SFRs, taking into account the subsolar metallicities observed in galaxies at high redshift. We confirm, with our large sample size, that the correlation between the Balmer decrement and stellar mass is already established out to z ∼ 7. We find that the relation between the Balmer decrement and stellar mass does not significantly evolve from the local Universe to z ∼ 7. We investigate the UV slope as a function of the Balmer optical depth and find that the best-fit correlation for our high redshift sample is specific SFR (sSFR) dependent and significantly different at high redshift when compared to galaxies at z ≈ 0 and z ≈ 2. For the highest sSFR galaxies in our sample, there is no significant correlation between the UV slope and Balmer optical depth. This is evidence that the UV slope should be used with great caution to correct for dust in high redshift galaxies.

Abstract:

We present a sample of 213 early-type galaxies (ETGs) at redshifts 0.25 < z < 0.75. We combine deep integral-field spectroscopy from the MUSE-DEEP survey with high-resolution Hubble Space Telescope (HST) imaging to study the structure, kinematics, and stellar populations of these galaxies. We measure spatially resolved stellar kinematics and use the specific angular momentum proxy, λR, to classify galaxies into fast and slow rotators. The kinematic and photometric axes of fast rotators are generally well aligned, similar to their local counterparts. We find that global stellar population properties, such as age, metallicity, and mass-to-light ratio (M*/L), correlate strongly with the central velocity dispersion (σe), following trends established for local ETGs. Slow rotators are typically more massive, have higher σe, and are more metal rich than fast rotators. We also find a slow rotator fraction consistent with local Universe samples. Our findings indicate that the fundamental structural, kinematic, and stellar population scaling relations of massive ETGs were already in place by z ∼ 0.75, suggesting their evolutionary pathways have remained stable over the last ∼7 Gyr.

Abstract:

NGC 1399, the bright central galaxy of the Fornax cluster, contains an extensive population of globular clusters (GCs) extending beyond 200 kpc into its outer halo, approximately 6.5 effective radii (Re). We conducted dynamical mass modelling of NGC 1399 out to 5 Re (∼150 kpc) using the most comprehensive radial velocity catalogue of GCs to date, which includes data from the Fornax cluster VLT Spectroscopic Survey (FVSS) and previous velocity measurements from the literature. Applying spherical Jeans equations, we performed dispersion-kurtosis modelling of NGC 1399’s GC kinematics to derive its mass profile and the orbital anisotropy of its GCs. We also investigated the impact of including intra-cluster GCs in the mass modelling, which were selected based on spatial segregation and a velocity σ-clipping method. Our findings indicate that both cusp-like (NFW) and core-like (Burkert) halos can reproduce the observed kinematics of GCs. Including the intra-cluster GCs in the mass modelling yields broadly consistent mass profiles for the two halo types, with the full GC sample giving a virial mass of log Mvir = 13.81 ± 0.09 M⊙ for the NFW halo, slightly higher than the value inferred for the Burkert halo. Regardless of the dark matter halo profile adopted, we observe that the intra-cluster GCs exhibit radial anisotropy in the outskirts, especially the blue, metal-poor GCs. These results suggest that GCs in NGC 1399’s outer halo are influenced by an additional halo component associated with the galaxy cluster potential. The radial anisotropy observed in these outer-halo GCs provides strong dynamical evidence that they were accreted from external sources, which is consistent with prior photometric and spectroscopic studies of GCs. This study highlights the importance of including intra-cluster GCs in dynamical mass modelling to fully account for the contribution of dark matter to the cluster gravitational potential.

Abstract:

Context. Measuring the expansion rate of the Universe is a central challenge in cosmology, particularly due to the persistent statistically significant discrepancy between the measurements of the Hubble constant, H 0 , obtained using early- and late-time probes, commonly known as the Hubble tension. Independent and robust methods are therefore essential to validate existing measurements and assess potential systematic effects. Aims. We employed the cosmic chronometer (CC) approach, which uses the differential age evolution of quiescent galaxies to measure the Hubble parameter H ( z ) without assuming an underlying cosmological model. In contrast to previous CC studies, we restricted our analysis to relics – ultra-compact massive galaxies (UCMGs) hosting the oldest stellar populations – thereby minimising uncertainties related to star formation history and merger history. Methods. We selected a sample of 189 relic galaxies in the redshift range 0.07 ≤ z ≤ 0.22 from the E-INSPIRE UCMG catalogue. Using the D n 4000 spectral index of relic galaxies and its redshift evolution, combined with MILES stellar population synthesis models, we derived the differential age relation required to infer H ( z ). We accounted not only for metallicity effects but also for the impact of α -element enhancement, which has not been explicitly propagated into the systematic uncertainty budget of the D n 4000 CC method. Results. We obtain an independent measurement of H ( z = 0.15) = 85 ± 53 km s −1 Mpc −1 . Although the total uncertainty remains large and dominated by statistical limitations, the systematic component is 13% (8.7% when α enrichment is not propagated), among the tightest estimates in current CC studies. We find that α enrichment plays a major role in the systematic error budget, particularly in the high-metallicity regime, and must be properly accounted for in future analyses. Conclusions. We demonstrate the proof of concept that relic galaxies provide a promising pathway to reduce systematic uncertainties in the CC method. The statistical uncertainties, which dominate the error budget, can be significantly reduced by the increase of data volume expected during the next years with Euclid , the Vera C. Rubin Observatory, DESI, and 4MOST.