Angular correlation functions of bright Lyman-break galaxies at 3 ≲ z ≲ 5
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf1651
Abstract:
Evidence for inverse Compton scattering in high-redshift Lyman-break galaxies
Monthly Notices of the Royal Astronomical Society (2025) staf1505
Abstract:
Radio continuum emission provides a unique opportunity to study star-formation unbiased by dust obscuration. However, if radio observations are to be used to accurately trace star-formation to high redshifts, it is crucial that the physical processes which affect the radio emission from star-forming galaxies are well understood. While inverse Compton (IC) losses from the cosmic microwave background (CMB) are negligible in the local universe, the rapid increase in the strength of the CMB energy density with redshift [∼(1 + z)4] means that this effect becomes increasingly important at z ≳ 3. Using a sample of ∼200, 000 high-redshift (3 < z < 5) Lyman-break galaxies selected in the rest-frame ultraviolet (UV), we have stacked radio observations from the MIGHTEE survey to estimate their 1.4-GHz flux densities. We find that for a given rest-frame UV magnitude, the 1.4-GHz flux density and luminosity decrease with redshift. We compare these results to the theoretical predicted effect of energy losses due to inverse Compton scattering off the CMB, and find that the observed decrease is consistent with this explanation. We discuss other possible causes for the observed decrease in radio flux density with redshift at a given UV magnitude, such as a top-heavy initial mass function at high redshift or an evolution of the dust properties, but suggest that inverse Compton scattering is the most compelling explanation.MIGHTEE: A first look at MIGHTEE quasars
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf1187
Abstract:
Abstract In this work we study a robust, Ks-band complete, spectroscopically-confirmed sample of 104 unobscured (Type-1) quasars within the COSMOS and XMM-LSS fields of the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey, at 0.60 < zspec < 3.41. The quasars are selected via gJKs colour-space and, with 1.3-GHz flux-densities reaching rms ≈ 3.0 μ Jy beam−1, we find a radio-loudness fraction of 5percnt. Thanks to the deep, multiwavelength datasets that are available over these fields, the properties of radio-loud and radio-quiet quasars can be studied in a statistically-robust way, with the emphasis of this work being on the active-galactic-nuclei (AGN)-related and star-formation-related contributions to the total radio emission. We employ multiple star-formation-rate estimates for the analysis so that our results can be compared more-easily with others in the literature, and find that the fraction of sources that have their radio emission dominated by the AGN crucially depends on the SFR estimate that is derived from the radio luminosity. When redshift dependence is not taken into account, a larger fraction of sources is classed as having their radio emission dominated by the AGN. When redshift dependence is considered, a larger fraction of our sample is tentatively classed as ‘starbursts’. We also find that the fraction of (possible) starbursts increases with redshift, and provide multiple suggestions for this trend.The ALMA-CRISTAL survey: Gas, dust, and stars in star-forming galaxies when the Universe was ∼1 Gyr old
Astronomy & Astrophysics EDP Sciences 699 (2025) a80
Abstract:
We present the ALMA-CRISTAL survey, an ALMA Cycle 8 Large Program designed to investigate the physical properties of star-forming galaxies at 4 ≲ z ≲ 6 through spatially resolved, multiwavelength observations. This survey targets 19 star-forming main-sequence galaxies selected from the ALPINE survey, using ALMA Band 7 observations to study [C II ] 158 μm line emission and dust continuum, complemented by JWST/NIRCam and HST imaging to map stellar and UV emission. The CRISTAL sample expanded to 39 after including newly detected galaxies in the CRISTAL fields, archival data, and pilot study targets. The resulting dataset provides a detailed view of gas, dust, and stellar structures on kiloparsec scales at the end of the era of reionization. The survey reveals diverse morphologies and kinematics, including rotating disks, merging systems, [C II ] emission tails from potential interactions, and clumpy star formation. Notably, the [C II ] emission in many cases extends beyond the stellar light seen in HST and JWST imaging. Scientific highlights include CRISTAL-10, exhibiting an extreme [C II ] deficit similar to Arp 220, and CRISTAL-13, where feedback from young star-forming clumps likely causes an offset between the stellar clumps and the peaks of [C II ] emission. CRISTAL galaxies exhibit global [C II ]/FIR ratios that decrease with increasing FIR luminosity, similar to trends seen in local galaxies but shifted to higher luminosities, likely due to their higher molecular gas content. CRISTAL galaxies also span a previously unexplored range of global FIR surface brightness at high-redshift, showing that high-redshift galaxies can have elevated [C II ]/FIR ratios. These elevated ratios are likely influenced by factors such as lower-metallicity gas, the presence of significant extraplanar gas, and contributions from shock-excited gas.The ALMA-CRISTAL survey: Extended [CII] emission in an interacting galaxy system at z ∼ 5.5
Astronomy & Astrophysics EDP Sciences 699 (2025) a256