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

Comparison of Hi and optical redshifts of galaxies - The impact of redshift uncertainties on spectral line stacking

Accurate optical redshifts will be critical for spectral co-adding techniques used to extract detections from below the noise level in ongoing and upcoming surveys for Hi, which will extend our current understanding of gas reservoirs in galaxies to lower column densities and higher redshifts. We have used existing, high quality optical and radio data from the SDSS and ALFALFA surveys to investigate the relationship be- tween redshifts derived from optical spectroscopy and neutral hydrogen (Hi) spectral line observations.We find that the two redshift measurements agree well, with a negli- gible systematic offset and a small distribution width. Employing simple simulations, we determine how the width of an ideal stacked Hi profile depends on these redshift offsets, as well as larger redshift errors more appropriate for high redshift galaxy sur- veys. The width of the stacked profile is dominated by the width distribution of the input individual profiles when the redshift errors are less than the median width of the input profiles, and only when the redshift errors become large, 150 kms−1, do they significantly affect the width of the stacked profile. This redshift accuracy can be achieved with moderate resolution optical spectra. We provide guidelines for the number of spectra required for stacking to reach a specified mass sensitivity, given tele- scope and survey parameters, which will be useful for planning optical spectroscopy observing campaigns to supplement the radio data.Web of Scienc

Predoctoral Interns\u27 Nondisclosure in Supervision

In interviews with 14 counseling center predoctoral interns regarding a significant nondisclosure in supervision, eight interns reported good supervisory relationships and six indicated that they experienced problematic supervisory relationships. Nondisclosures for the interns in good supervisory relationships related to personal reactions to clients, whereas nondisclosures for interns in problematic supervisory relationships related to global dissatisfaction with the supervisory relationship. In both groups, interns mentioned concerns about evaluation and negative feelings as typical reasons for nondisclosure. Additional reasons for nondisclosure for interns in problematic supervision were power dynamics, inhibiting demographic or cultural variables, and the supervisor\u27s theoretical orientation. Both groups described negative effects of nondisclosure on themselves and their relationships with clients. Interns in problematic supervision also reported that nondisclosures had negative effects on the supervisory relationship

Variation of galactic cold gas reservoirs with stellar mass

The stellar and neutral hydrogen (HI) mass functions at z~0 are fundamental benchmarks for current models of galaxy evolution. A natural extension of these benchmarks is the two-dimensional distribution of galaxies in the plane spanned by stellar and HI mass, which provides a more stringent test of simulations, as it requires the HI to be located in galaxies of the correct stellar mass. Combining HI data from the ALFALFA survey, with optical data from SDSS, we find a distinct envelope in the HI-to-stellar mass distribution, corresponding to an upper limit in the HI fraction that varies monotonically over five orders of magnitude in stellar mass. This upper envelope in HI fraction does not favour the existence of a significant population of dark galaxies with large amounts of gas but no corresponding stellar population. The envelope shows a break at a stellar mass of ~10^9 Msun, which is not reproduced by modern models of galaxy populations tracing both stellar and gas masses. The discrepancy between observations and models suggests a mass dependence in gas storage and consumption missing in current galaxy evolution prescriptions. The break coincides with the transition from galaxies with predominantly irregular morphology at low masses to regular disks at high masses, as well as the transition from cold to hot accretion of gas in simulations.Comment: 9 pages, 6 figures, accepted for publication in MNRA

The H I mass function of group galaxies in the ALFALFA survey

We estimate the H i mass function (HIMF) of galaxies in groups based on thousands of ALFALFA (Arecibo Legacy Fast ALFA survey) H i detections within the galaxy groups of four widely used SDSS (Sloan Digital Sky Survey) group catalogues. Although differences between the catalogues mean that there is no one definitive group galaxy HIMF, in general we find that the low-mass slope is flat, in agreement with studies based on small samples of individual groups, and that the 'knee' mass is slightly higher than that of the global HIMF of the full ALFALFA sample. We find that the observed fraction of ALFALFA galaxies in groups is approximately 22 per cent. These group galaxies were removed from the full ALFALFA source catalogue to calculate the field HIMF using the remaining galaxies. Comparison between the field and group HIMFs reveals that group galaxies make only a small contribution to the global HIMF as most ALFALFA galaxies are in the field, but beyond the HIMF 'knee' group galaxies dominate. Finally, we attempt to separate the group galaxy HIMF into bins of group halo mass, but find that too few low-mass galaxies are detected in the most massive groups to tightly constrain the slope, owing to the rarity of such groups in the nearby Universe where low-mass galaxies are detectable with existing H i surveys.© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyWe acknowledge the work of the entire ALFALFA team for observing, flagging, and performing signal extraction. We thank the anonymous referee for their suggestions that helped to improve this paper. MGJ is supported by a Juan de la Cierva formacion´ fellowship (FJCI-2016-29685) from the Spanish Ministerio de Ciencia, Innovacion y Universidades (MCIU). MGJ and LVM ´ also acknowledge support from the grants AYA2015-65973-C3-1- R (MINECO/FEDER, UE) and RTI2018-096228-B-C31 (MCIU). The research of KMH is supported by the under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement nr. 291531. EAKA is supported by the WISE research programme, which is financed by the Netherlands Organisation for Scientific Research (NWO). This work has been supported by the State Agency for Research of the Spanish MCIU through the ‘Centro de Excelencia Severo Ochoa’ award to the Instituto de Astrof´ısica de Andaluc´ıa (SEV-2017-0709). This research was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) which is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)Peer reviewe

ALFALFA and WSRT Imaging of Extended H I Features in the Leo Cloud of Galaxies

We present ALFALFA HI observations of a well studied region of the Leo Cloud, which includes the NGC 3227 group and the NGC 3190 group. We detect optically dark HI tails and plumes with extents potentially exceeding 600 kpc, well beyond the field of view of previous observations. These HI features contain approximately 40% of the total HI mass in the NGC~3227 group and 10% in the NGC~3190 group. We also present WSRT maps which show the complex morphology of the extended emission in the NGC~3227 group. We comment on previously proposed models of the interactions in these groups and the implications for the scale of group processing through interactions. Motivated by the extent of the HI plumes, we place the HI observations in the context of the larger loose group, demonstrating the need for future sensitive, wide field HI surveys to understand the role of group processing in galaxy evolution.Comment: 17 pages, 9 figures, accepted for publication in MNRA

H I in group interactions: HCG 44

Extending deep observations of the neutral atomic hydrogen (HI) to the environment around galaxy groups can reveal a complex history of group interactions which is invisible to studies that focus on the stellar component. Hickson Compact Group 44 (HCG 44) is a nearby example and we have combined HI data from the Karoo Array Telescope, Westerbork Synthesis Radio Telescope, and Arecibo Legacy Fast ALFA survey, in order to achieve high column density sensitivity (N_HI < 2x10^18 cm^-2) to the neutral gas over a large field-of-view beyond the compact group itself. We find the giant HI tail north of HCG 44 contains 1.1x10^9 M_Sun of gas and extends 450 kpc from the compact group: twice as much mass and 33% further than previously detected. However, the additional gas is still unable to account for the known HI deficiency of HCG 44. The tail likely formed through a strong tidal interaction and HI clouds in the tail have survived for 1 Gyr or more after being stripped. This has important implications for understanding the survival of neutral clouds in the intragroup and circumgroup medium, and we discuss their survival in the context of simulations of cold gas in hot halos. HCG 44 is one of a growing number of galaxy groups found to have more extended HI in the intragroup and circumgroup medium than previously measured. Our results provide constraints for simulations on the properties of galaxy group halos, and reveal a glimpse of what will be seen by future powerful HI telescopes and surveys.Comment: 12 pages, 6 figures. Accepted for publication in MNRA