The High-redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: Investigating the Role of Environment on Bent Radio AGNs Using LOFAR

© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Bent radio active galactic nucleus (AGN) morphology depends on the density of the surrounding gas. However, bent sources are found inside and outside clusters, raising the question of how environment impacts bent AGN morphology. We analyze new LOw-Frequency Array the LOFAR Two-metre Sky Survey (LoTSS) Data Release II observations of 20 bent AGNs in clusters and 15 not in clusters from the high-z Clusters Occupied by Bent Radio AGN (COBRA) survey (0.35 1.2 Mpc) or bent AGNs in weaker groups rather than the field.Peer reviewe

The Mass-Metallicity Relation of Dwarf Galaxies at the Cosmic Noon in the JWST Era

We present the mass-metallicity relation (MZR) at $z=2-3$ in the stellar mass range of $M_\star\approx 10^{6.5}-10^{9.5}M_\odot$ using 55 dwarf galaxies in the Abell 2744 and SMACS J0723-3732 galaxy cluster fields. These dwarf galaxies are identified and confirmed by deep JWST/NIRISS imaging and slitless grism spectroscopic observations. Taking advantage of the gravitational lensing effect, we extend the previous MZR relation at $z=2-3$ to a much lower mass regime by more than 2.5 orders of magnitude compared with previous studies. We find that the MZR has a shallower slope at the low-mass end ($M_\star<10^{9}M_\odot$) compared to that at the high-mass end ($M_\star>10^{9}M_\odot$), with a slope turnover point at around the stellar mass of $10^9 M_\odot$. This implies that dominating feedback processes in dwarf galaxies may be different from that in galaxies with higher mass. From $z=3$ to $z=2$, the metallicity of the dwarf galaxies is enhanced by $\approx0.1$ dex for a given stellar mass, consistent with the mild evolution found in galaxies with higher mass. Further, we confirm the existence of a 3D relation between the gas-phase metallicity, stellar mass, and star formation rate, i.e., fundamental metallicity relation (FMR), in dwarf galaxies at $z=2-3$. Our derived FMR, which has no significant redshift evolution, can be used as a benchmark to understand the origin of the anti-correlation between SFR and metallicity of dwarf galaxies in the high-redshift Universe.Comment: 16 pages, 4 figures, 1 table, submitted to AAS Journal; welcome comment

Searching for C ii Emission from the First Sample of z ∼ 6 O i Absorption-associated Galaxies with the Atacama Large Millimeter/submillimeter Array

We report the first statistical analyses of [C ii ] and dust continuum observations in six strong O i absorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combined with one [C ii ] emitter reported in Wu et al., we detect one O i -associated [C ii ] emitter in six fields. At redshifts of O i absorbers in nondetection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between ±200 km s ^−1 . The averaged [C ii ]-detection upper limit is 50 kpc) and having larger outflow velocities within ±600 km s ^−1 . If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side

Extended Radio AGN at z ∼ 1 in the ORELSE Survey: The Confining Effect of Dense Environments

Recent hydrodynamic simulations and observations of radio jets have shown that the surrounding environment has a large effect on their resulting morphology. To investigate this, we use a sample of 50 Extended Radio Active Galactic Nuclei (ERAGN) detected in the Observations of Redshift Evolution in Large-Scale Environments survey. These sources are all successfully cross-identified to galaxies within a redshift range of 0.55 ≤ z ≤ 1.35, either through spectroscopic redshifts or accurate photometric redshifts. We find that ERAGN are more compact in high-density environments than those in low-density environments at a significance level of 4.5σ. Among a series of internal properties under our scrutiny, only the radio power demonstrates a positive correlation with their spatial extent. After removing the possible radio power effect, the difference of size in low- and high-density environments persists. In the global environment analyses, the majority (86%) of high-density ERAGN reside in the cluster/group environment. In addition, ERAGN in the cluster/group central regions are preferentially compact with a small scatter in size, compared to those in the cluster/group intermediate regions and fields. In conclusion, our data appear to support the interpretation that the dense intracluster gas in the central regions of galaxy clusters plays a major role in confining the spatial extent of radio jets

Identification and Characterization of Six Spectroscopically Confirmed Massive Protostructures at 2.5<z<4.52.5<z<4.5

We present six spectroscopically confirmed massive protostructures, spanning a redshift range of $2.5<z<4.5$ in the Extended Chandra Deep Field South (ECDFS) field discovered as part of the Charting Cluster Construction in VUDS and ORELSE (C3VO) survey. We identify and characterize these remarkable systems by applying an overdensity measurement technique on an extensive data compilation of public and proprietary spectroscopic and photometric observations in this highly studied extragalactic field. Each of these six protostructures, i.e., a large scale overdensity (volume $>9000$\thinspace cMpc$^3$) of more than $2.5\sigma_{\delta}$ above the field density levels at these redshifts, have a total mass $M_{tot}\ge10^{14.8}M_\odot$ and one or more highly overdense (overdensity$\thinspace>5\sigma_{\delta}$) peaks. One of the most complex protostructures discovered is a massive ($M_{tot}=10^{15.1}M_\odot$) system at $z\sim3.47$ that contains six peaks and 55 spectroscopic members. We also discover protostructures at $z\sim3.30$ and $z\sim3.70$ that appear to at least partially overlap on sky with the protostructure at $z\sim3.47$, suggesting a possible connection. We additionally report on the discovery of three massive protostructures at $z=2.67$, 2.80, and 4.14 and discuss their properties. Finally, we discuss the relationship between star formation rate and environment in the richest of these protostructures, finding an enhancement of star formation activity in the densest regions. The diversity of the protostructures reported here provide an opportunity to study the complex effects of dense environments on galaxy evolution over a large redshift range in the early universe.Comment: 10 pages, 4 figures, 1 tabl

The high-redshift clusters occupied by bent radio AGN (COBRA) survey

Galaxy clusters are the largest gravitationally-bound structures in the universe. Since clusters are comprised of hundreds of galaxies, hot X-ray emitting gas, and dark matter, they offer a unique laboratory in which to explore the evolution of large-scale structure and galaxies. To understand how massive, low-redshift galaxy clusters evolve to become what is observed in the modern universe, astronomers need to trace the evolution of progenitor clusters. Though there are thousands of well-studied low-redshift clusters, there are significantly fewer spectroscopically confirmed high-redshift clusters. Because most massive galaxies host supermassive black holes, one cluster tracer at both low and high redshift are active galactic nuclei (AGNs). Specifically, bent, double-lobed radio sources are commonly found in clusters. I find high-redshift clusters hosting bent AGNs and explore their evolution and red sequence galaxies over cosmic time. To characterize cluster evolution, I examine the galaxy populations surrounding each AGN to determine if bent AGNs are commonly found within clusters with evolved red sequence populations. I then identify evolution among the member galaxies in the clusters, I estimate cluster morphology, and I explore the relationship between bent radio source morphology and the surrounding cluster. By measuring the color of each galaxy and the overdensity of galaxies surrounding each AGN, I identify 39 red sequence cluster candidates, 17 of which are at redshifts of z > 1.0. Using my red sequence surface density measurement, I show that each bent AGN is not necessarily centrally located, but is generally within ~ 400 kpc of the cluster center. With this sample, I probe the dynamics of the host galaxies using the radio source morphology and find that most of the radio sources do not follow radial paths relative to the cluster center. By analyzing the morphology of the radio sources in my sample, I find that richer clusters host narrower bent sources. I also see a range of red sequence populations in the clusters, with variations, in particular, among the populations of faint red sequence galaxies. With my surface density measurements, I place preliminary constraints on cluster morphology, finding both relaxed and merging systems