Deep Radio Observations and the Role of the Cosmic Web in Galaxy Evolution

A current open question in the evolution of galaxies, is what are the physical mechanisms that cut off galaxies from their primordial gas reservoirs, resulting in the end of their star-formation capabilities? Recent observational programs have shown that the properties of galaxies show dependencies on their placement within the large-scale structure (LSS) of the universe. These observations have motivated recent developments in theoretical work that have shown how a galaxy\u27s interaction with the LSS may impact its connection to primordial gas supply, and ability to continue to accrete gas, the fundamental ingredient in star-formation. In order to investigate the role of LSS in galaxy evolution, we use data from the COSMOS HI Large Extragalactic Survey (CHILES), a single pointing of the Very Large Array in the COSMOS field with the ability to detect HI in galaxies out to a redshift 0.45. We introduce a fast imaging pipeline that is able to produce science-ready image cubes of the CHILES data in a reasonable turnover time. This pipeline is applied to the full CHILES database and produces data of excellent sensitivity with minimal imaging artefacts. Additionally, we introduce the CHILES Continuum Polarization Survey (CHILES Con Pol), which is the most sensitive 1.4 GHz radio continuum survey, to date, at 4.5 resolution. We discuss the survey design, data processing, and comparison to other surveys taken in the COSMOS field and discuss their complementary aspects. Using these high quality sensitive radio data, and ancillary data from the COSMOS survey, we investigate neutral hydrogen content and relative star-formation rate for blue, lower mass spiral galaxies as a function of their placement in their LSS, for two redshift bins. We find that the neutral hydrogen content for galaxies not near the spine of filaments, more than 2 Mpc away, is lower in our low-z bin. We place this result in the context of recent theoretical work and speculate that we are observing recent cosmic web detachment events for galaxies of these types, that result in the cutting-off of galaxies from their primordial gas supply

Large Scale Structure in CHILES

We demonstrate that the Discrete Persistent Source Extractor (DisPerSE) can be used with spectroscopic redshifts to define the cosmic web and its distance to galaxies in small area deepfields. Here we analyze the use of DisPerSE to identify structure in observational data. We apply DisPerSE to the distribution of galaxies in the COSMOS field and find the best parameters to identify filaments. We compile a catalog of 11500 spectroscopic redshifts from the Galaxy and Mass Assembly (GAMA) G10 data release. We analyze two-dimensional slices, extract filaments and calculate the distance for each galaxy to its nearest filament. We find that redder and more massive galaxies are closer to filaments. To study the growth of galaxies across cosmic time, and environment, we are carrying out an HI survey covering redshifts z = 0 - 0.45, the COSMOS HI Large Extragalactic Survey (CHILES). In addition we present the predicted HI mass fraction as a function of distance to filaments for the spectroscopically known galaxies in CHILES. Lastly, we discuss the cold gas morphology of a few individual galaxies and their positions with respect to the cosmic web. The identification of the cosmic web, and the ability of CHILES to study the resolved neutral hydrogen morphologies and kinematics of galaxies, will allow future studies of the properties of neutral hydrogen in different cosmic web environments across the redshift range z = 0.1 - 0.45.Comment: Accepted for publication in the Astronomical Journal; 11 pages ; 8 figure

CHILES: HI morphology and galaxy environment at z=0.12 and z=0.17

We present a study of 16 HI-detected galaxies found in 178 hours of observations from Epoch 1 of the COSMOS HI Large Extragalactic Survey (CHILES). We focus on two redshift ranges between 0.108 <= z <= 0.127 and 0.162 <= z <= 0.183 which are among the worst affected by radio frequency interference (RFI). While this represents only 10% of the total frequency coverage and 18% of the total expected time on source compared to what will be the full CHILES survey, we demonstrate that our data reduction pipeline recovers high quality data even in regions severely impacted by RFI. We report on our in-depth testing of an automated spectral line source finder to produce HI total intensity maps which we present side-by-side with significance maps to evaluate the reliability of the morphology recovered by the source finder. We recommend that this become a common place manner of presenting data from upcoming HI surveys of resolved objects. We use the COSMOS 20k group catalogue, and we extract filamentary structure using the topological DisPerSE algorithm to evaluate the \hi\ morphology in the context of both local and large-scale environments and we discuss the shortcomings of both methods. Many of the detections show disturbed HI morphologies suggesting they have undergone a recent interaction which is not evident from deep optical imaging alone. Overall, the sample showcases the broad range of ways in which galaxies interact with their environment. This is a first look at the population of galaxies and their local and large-scale environments observed in HI by CHILES at redshifts beyond the z=0.1 Universe.Comment: 23 pages, 12 figures, 1 interactive 3D figure, accepted to MNRA

GASP XXXIX: MeerKAT hunts Jellyfish in A2626

We present MeerKAT H I observations of six jellyfish candidate galaxies (JFCGs) in the galaxy cluster, A2626. Two of the six galaxies JW100 and JW103, which were identified as JFCGs from B-band images, are confirmed as jellyfish galaxies (JFGs). Both of the JFGs have low H I content, reside in the cluster core, and move at very high velocities (~ 3σcl). The other JFCGs, identified as non-jellyfish galaxies, are H I rich, with H I morphologies revealing warps, asymmetries, and possible tidal interactions. Both the A2626 JFGs and three other confirmed JFGs from the GASP sample show that these galaxies are H I stripped but not yet quenched. We detect H I, H α, and CO(2-1) tails of similar extent (~50 kpc) in JW100. Comparing the multiphase velocity channels, we do not detect any H I or CO(2-1) emission in the northern section of the tail where H α emission is present, possibly due to prolonged interaction between the stripped gas and the intracluster medium. We also observe an anticorrelation between H I and CO(2-1), which hints at an efficient conversion of H I to H2 in the southern part of the tail. We find that both ram-pressure stripping and H I-to-H2 conversion are significant depletion channels for atomic gas. H I-to-H2 conversion is more efficient in the disc than in the tail