The stellar and neutral hydrogen (H i) 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 H i mass, which provides a more stringent test of simulations, as it requires the H i to be located in galaxies of the correct stellar mass. Combining H i data from the Arecibo Legacy Fast ALFA survey, with optical data from Sloan Digital Sky Survey, we find a distinct envelope in the H i-to-stellar mass distribution, corresponding to an upper limit in the H i fraction that varies monotonically over five orders of magnitude in stellar mass. This upper envelope in H i 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 ∼109 M⊙, 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 discs at high masses, as well as the transition from cold to hot accretion of gas in simulations.
Abstract
New MMT/Hectospec spectroscopy centered on the galaxy cluster A2626 and covering a ∼1.8 deg
2
area out to
z
∼ 0.46 more than doubles the number of galaxy redshifts in this region. The ...spectra confirm four clusters previously identified photometrically. A2625, which was previously thought to be a close neighbor of A2626, is in fact much more distant. The new data show six substructures associated with A2626 and five more associated with A2637. There is also a highly collimated collection of galaxies and galaxy groups between A2626 and A2637 having at least three and probably four substructures. At larger scales, the A2626–A2637 complex is not connected to the Pegasus–Perseus filament.
Compared with STEM fields, foreign language (FL) education and second language acquisition have only slowly embraced open education and the new knowledge ecologies it produces. FL educators may have ...been hesitant to participate in the open education movement due to a lack of research which investigates the benefits and challenges of FL learning and teaching in open environments. This book contextualizes open education in FL learning and teaching via an historical overview of the movement, along with an in-depth exploration of how the open movement affects FL education beyond the classroom context; fills the research void by exploring aspects of open second language learning and teaching across a range of educational contexts; and illustrates new ways of creating, adapting and curating FL materials that are freely shared among FL educators and students. This book is open access under a CC BY ND licence.
Context.
The morphology-density relation manifests the environmental dependence of the formation and evolution of galaxies as they continuously migrate through the cosmic web to ever denser ...environments. As gas-rich galaxies traverse the outskirts and inner regions of galaxy clusters, they experience sudden and radical changes in their gas content and star formation activity.
Aims.
The goal of this work is to gain an H
I
perspective on gas depletion mechanisms acting on galaxies and galaxy groups that are being accreted by a moderately massive galaxy cluster. We aim to study the relative importance and efficiency of processes such as ram-pressure stripping and tidal interactions as well as their dependency on the local and global environment of galaxies in the cluster core and in its surroundings.
Methods.
We have conducted a blind radio continuum and H
I
spectral line imaging survey with the MeerKAT radio telescope of a 2° × 2° area centred on the galaxy cluster Abell 2626. We have used the
CARAcal
pipeline to reduce the data,
SoFiA
to detect sources within the H
I
data cube, and
GIPSY
to construct spatially resolved information on the H
I
morphologies and kinematics of the H
I
detected galaxies.
Results.
We have detected H
I
in 219 galaxies with optical counterparts within the entire surveyed volume. We present the H
I
properties of each of the detected galaxies as a data catalogue and as an atlas page for each galaxy, including H
I
column-density maps, velocity fields, position-velocity diagrams, and global H
I
profiles. These data will also be used for case studies of identified ‘jellyfish’ galaxies and galaxy population studies by means of morphological classification of the direct H
I
detections as well as using the H
I
stacking technique.
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Measuring galaxy asymmetries in 3D Deg, N; Perron-Cormier, M; Spekkens, K ...
Monthly notices of the Royal Astronomical Society,
06/2023, Volume:
523, Issue:
3
Journal Article
Peer reviewed
Open access
ABSTRACT
One of the commonly used non-parametric morphometric statistics for galaxy profiles and images is the asymmetry statistic. With an eye to current and upcoming large neutral hydrogen (H i) ...surveys, we develop a 3D version of the asymmetry statistic that can be applied to datacubes. This statistic is more resilient to variations due to the observed geometry than 1D asymmetry measures, and can be successfully applied to lower spatial resolutions (3 – 4 beams across the galaxy major axis) than the 2D statistic. We have also modified the asymmetry definition from an ‘absolute difference’ version to a ‘squared difference’ version that removes much of the bias due to noise contributions for low signal-to-noise observations. Using a suite of mock asymmetric cubes we show that the background-corrected, squared difference 3D asymmetry statistic can be applied to many marginally resolved galaxies in large wide-area H i surveys such as WALLABY on the Australian SKA Pathfinder (ASKAP).
We present the H
I
emission project within the MIGHTEE survey, currently being carried out with the newly commissioned MeerKAT radio telescope. This is one of the first deep, blind, medium-wide ...interferometric surveys for neutral hydrogen (H
I
) ever undertaken, extending our knowledge of H
I
emission to
z
= 0.6. The science goals of this medium-deep, medium-wide survey are extensive, including the evolution of the neutral gas content of galaxies over the past 5 billion years. Simulations predict nearly 3000 galaxies over 0 <
z
< 0.4 will be detected directly in H
I
, with statistical detections extending to
z
= 0.6. The survey allows us to explore H
I
as a function of galaxy environment, with massive groups and galaxy clusters within the survey volume. Additionally, the area is large enough to contain as many as 50 local galaxies with H
I
mass < 10
8
M
⊙
, which allows us to study the low-mass galaxy population. The 20 deg
2
main survey area is centred on fields with exceptional multi-wavelength ancillary data, with photometry ranging from optical through far-infrared wavelengths, supplemented with multiple spectroscopic campaigns. We describe here the survey design and the key science goals. We also show first results from the Early Science observations, including kinematic modelling of individual sources, along with the redshift, H
I
, and stellar mass ranges of the sample to date.
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A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9 GW(th) reactors were ...detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) and the first direct measurement of the ν¯(e) mass-squared difference |Δm(ee)2|=(2.59(-0.20)(+0.19))×10(-3) eV2 is obtained using the observed ν¯(e) rates and energy spectra in a three-neutrino framework. This value of |Δm(ee)2| is consistent with |Δm(μμ)2| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.
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We report a measurement of electron antineutrino oscillation from the Daya Bay Reactor Neutrino Experiment with nearly 4 million reactor νover ¯_{e} inverse β decay candidates observed over 1958 days ...of data collection. The installation of a flash analog-to-digital converter readout system and a special calibration campaign using different source enclosures reduce uncertainties in the absolute energy calibration to less than 0.5% for visible energies larger than 2 MeV. The uncertainty in the cosmogenic ^{9}Li and ^{8}He background is reduced from 45% to 30% in the near detectors. A detailed investigation of the spent nuclear fuel history improves its uncertainty from 100% to 30%. Analysis of the relative νover ¯_{e} rates and energy spectra among detectors yields sin^{2}2θ_{13}=0.0856±0.0029 and Δm_{32}^{2}=(2.471_{-0.070}^{+0.068})×10^{-3} eV^{2} assuming the normal hierarchy, and Δm_{32}^{2}=-(2.575_{-0.070}^{+0.068})×10^{-3} eV^{2} assuming the inverted hierarchy.
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ABSTRACT
We examine different measures of asymmetry for galaxy H i velocity profiles. We introduce the channel-by-channel asymmetry and the velocity-of-equality statistics to quantify profile ...asymmetries. Using a sample of simulated galaxies, we examine how these and the standard lopsidedness morphometric statistic depend on a variety of observational effects, including the viewing angle and inclination. We find that our newly introduced channel-by-channel asymmetry is less sensitive to the effects of viewing angle and inclination than other morphometrics. Applying our statistics to the WHISP (Westerbork H i survey of Irregular and SPiral galaxies) H i galaxy sample, we also find that the channel-by-channel asymmetry is a better indicator of visually classified asymmetric profiles. In addition, we find that the lopsidedness–velocity of equality space can be used to identify profiles with deep central dips without visual inspection.
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