Galaxy formation and evolution

Abstract:

We report the detection of a previously unknown object with a single emission line within the Hubble Ultra Deep Field, using a new JWST NIRSpec technique called Multiobject Coronagraphy for Slitless Spectroscopy (MOCSS) with the G140M/F100LP observing mode. The MOCSS technique involves opening almost all the shutters on the NIRSpec microshutter array, while simultaneously closing the shutters that lie on top of known low-redshift objects, facilitating a wide-field slitless spectroscopic search without contamination from bright objects. This observational technique has enabled the detection of a strong emission line in four different dither positions and in two position angles, and thus cannot be artificial. This line is detected at 1.60 μm with a line flux of [2.5 ± 0.3] × 10−18 erg s−1cm−2 and an FWHM of 13.2 ± 2.0 Å, and does not correspond to any known source with some of the deepest Hubble Space Telescope and JWST imaging in existence. Based upon the absence of imaging detection, we place a lower limit on the observed frame equivalent width (EW) of 7620 Å on this object, which strongly limits the number of possible lines that this line can be. Given the wavelength, an EW limit that is near the ceiling of expectation, and the lack of other lines in the bandpass, this line cannot be easily explained by [O ii] at z = 3.29, [O iii] at z = 2.20, Hα at z = 1.44, and Lyα at z = 12.16. We discuss possible active galactic nucleus and transient phenomena that could explain the finding.

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:

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, λ R , 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 ( σ e ), following trends established for local ETGs. Slow rotators are typically more massive, have higher σ e , 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:

Abstract The physics governing the morphology of radio-loud AGN jets is not fully understood. We investigate how magnetization, flickering jet power and their interplay affects the morphology of radio galaxies. We present a grid of relativistic magnetohydrodynamic simulations using the PLUTO code covering constant and variable jets with two levels of magnetisation. We find that the constant high magnetisation jets can lead to highly asymmetrical cocoon morphologies, whilst the variable high magnetisation jet can exhibit a broken morphology, caused by a discontinuous jet beam. Our work highlights the importance of magnetisation and variability on the stability and resulting morphology of radio-loud AGN jets, suggesting both are significant factors in addition to jet power or environment. Furthermore, we show that the interaction between magnetisation and variability can lead to the development of localised kink instabilities along the jet beam. Finally, we discuss the effects of hydrodynamic mixing in low magnetisation jets and the role of viewing angle dependence in comparisons between our simulations and observed sources. To facilitate this comparison we present a library of simulated radio images at different times in the simulations and from various viewing angles, which highlight a diverse set of complex morphologies.

Abstract:

Abstract We analyse black hole scaling relations for disk-dominated galaxies, and present evidence for secularly driven galaxy-black hole co-evolution. We do this observationally by looking at “bulgeless” galaxies, where the lack of a stellar bulge suggests a quiet merger history. We first compose a sample of 2,435 disk-dominated galaxies hosting optical broad line active galactic nuclei (AGN) from DESI data, and find a $M_{\mathrm{BH}^{}}$–$M_{*}^{}$ scaling relation of log (MBH) $= - 3.7^{+0.3}_{-0.3} + 1.00^{+0.03}_{-0.03} \log (M_*)$. From these, we identify 546 bulgeless galaxies hosting AGN, a factor of ≳ 5 larger than pre-existing samples, and find they follow the same $M_{\mathrm{BH}^{}}$-$M_{*}^{}$ relation as the general disk galaxy sample. Comparing the bulgeless galaxies to those with some bulge component, we find good agreement in the $M_{\mathrm{BH}^{}}$–$M_{*}^{}$ relation (within 3σ), but disagreement in the $M_{\mathrm{BH}^{}}$–$M_{\mathrm{*,bulge}}^{}$ relation (at &gt;7σ). This is the opposite of what is expected from merger-driven co-evolution, suggesting secular growth is significant in establishing observed $M_{\mathrm{BH}^{}}$–$M_{*}^{}$ scaling relations. Furthermore, in a control sample of early-type galaxies we find tentative evidence of increased AGN luminosity compared to the bulgeless sample, but no statistical difference in black hole mass. This suggests the assumed merger-dominated evolutionary history of early-type galaxies does not lead to significantly increased long-term BH growth. These results support numerous recent observational and theoretical studies which suggest secular processes fuel significant supermassive black hole growth and galaxy-black hole co-evolution.