7 research outputs found
The HiZELS/UKIRT large area survey for bright Lyman-alpha emitters at z~9
We present the largest area survey to date (1.4 deg2) for Lyman-alpha
emitters (LAEs) at z~9, as part of the Hi-z Emission Line Survey (HiZELS). The
survey, which primarily targets H-alpha emitters at z < 3, uses the Wide Field
CAMera on the United Kingdom Infrared Telescope and a custom narrow-band filter
in the J band to reach a Lyman-alpha luminosity limit of ~10^43.8 erg/s over a
co-moving volume of 1.12x10^6 Mpc^3 at z = 8.96+-0.06. Two candidates were
found out of 1517 line emitters, but those were rejected as LAEs after
follow-up observations. This improves the limit on the space density of bright
Lyman-alpha emitters by 3 orders of magnitude and is consistent with
suppression of the bright end of the Lyman-alpha luminosity function beyond
z~6. Combined with upper limits from smaller but deeper surveys, this rules out
some of the most extreme models for high-redshift Lyman-alpha emitters. The
potential contamination of narrow-band Lyman-alpha surveys at z>7 by Galactic
brown dwarf stars is also examined, leading to the conclusion that such
contamination may well be significant for searches at 7.7 < z < 8.0, 9.1 < z <
9.5 and 11.7 < z < 12.2.Comment: To appear in proceedings of "UKIRT at 30: A British Success Story
HiZELS: the High Redshift Emission Line Survey with UKIRT
In these proceedings we report on HiZELS, the High-z Emission Line Survey,
our successful panoramic narrow-band Campaign Survey using WFCAM on UKIRT to
detect and study emission line galaxies at z~1-9. HiZELS employs the H2(S1)
narrow-band filter together with custom-made narrow-band filters in the J and
H-bands, with the primary aim of delivering large, identically-selected samples
of H-alpha emitting galaxies at redshifts of 0.84, 1.47 and 2.23. Comparisons
between the luminosity function, the host galaxy properties, the clustering,
and the variation with environment of these H-alpha-selected samples are
yielding unique constraints on the nature and evolution of star-forming
galaxies, across the peak epoch of star-formation activity in the Universe. We
provide a summary of the project status, and detail the main scientific results
obtained so far: the measurement of the evolution of the cosmic star-formation
rate density out to z > 2 using a single star-formation indicator,
determination of the morphologies, environments and dust-content of the
star-forming galaxies, and a detailed investigation of the evolution of their
clustering properties. We also summarise the on-going work and future goals of
the project.Comment: To appear in proceedings of "UKIRT at 30: A British Success Story"
Radio imaging of the Subaru/XMM-Newton Deep Field - III. Evolution of the radio luminosity function beyond z=1
We present spectroscopic and eleven-band photometric redshifts for galaxies
in the 100-uJy Subaru/XMM-Newton Deep Field radio source sample. We find good
agreement between our redshift distribution and that predicted by the SKA
Simulated Skies project. We find no correlation between K-band magnitude and
radio flux, but show that sources with 1.4-GHz flux densities below ~1mJy are
fainter in the near-infrared than brighter radio sources at the same redshift,
and we discuss the implications of this result for spectroscopically-incomplete
samples where the K-z relation has been used to estimate redshifts. We use the
infrared--radio correlation to separate our sample into radio-loud and
radio-quiet objects and show that only radio-loud hosts have spectral energy
distributions consistent with predominantly old stellar populations, although
the fraction of objects displaying such properties is a decreasing function of
radio luminosity. We calculate the 1.4-GHz radio luminosity function (RLF) in
redshift bins to z=4 and find that the space density of radio sources increases
with lookback time to z~2, with a more rapid increase for more powerful
sources. We demonstrate that radio-loud and radio-quiet sources of the same
radio luminosity evolve very differently. Radio-quiet sources display strong
evolution to z~2 while radio-loud AGNs below the break in the radio luminosity
function evolve more modestly and show hints of a decline in their space
density at z>1, with this decline occurring later for lower-luminosity objects.
If the radio luminosities of these sources are a function of their black hole
spins then slowly-rotating black holes must have a plentiful fuel supply for
longer, perhaps because they have yet to encounter the major merger that will
spin them up and use the remaining gas in a major burst of star formation.Comment: Accepted for publication in MNRAS: 36 pages, including 13 pages of
figures to appear online only. In memory of Stev
Proceedings of Abstracts, School of Physics, Engineering and Computer Science Research Conference 2022
© 2022 The Author(s). This is an open-access work distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. For further details please see https://creativecommons.org/licenses/by/4.0/. Plenary by Prof. Timothy Foat, ‘Indoor dispersion at Dstl and its recent application to COVID-19 transmission’ is © Crown copyright (2022), Dstl. This material is licensed under the terms of the Open Government Licence except where otherwise stated. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: [email protected] present proceedings record the abstracts submitted and accepted for presentation at SPECS 2022, the second edition of the School of Physics, Engineering and Computer Science Research Conference that took place online, the 12th April 2022
Galactic Science Case for AtLAST
We will present a report from the Science Working Group breakaway sessions
The nature and evolution of H alpha emitters at high-z with HiZELS
The High-z Emission Line Survey (HiZELS) is targeting H alpha emitters at z similar to 0.8 - 2.2, and, by probing large volumes down to faint fluxes with WFCAM on UKIRT, is resulting in the largest samples of high-z H alpha selected star-forming galaxies. With HiZELS, we have accurately measured the evolution of the H alpha luminosity function up to z > 2 in a fully consistent way and determined the H alpha-based star formation history of the Universe since z similar to 2.2 for the first time. We have found important morphology-H alpha relations and have been able to show that it is the evolution of disk galaxies from z similar to 1 to z similar to 0 that is responsible for the decline in the cosmic star formation activity not the decline in merger activity. Furthermore, we have conducted the first detailed clustering analysis of H alpha emitters at z similar to 1 and their evolution up to z > 2, not only finding strong relations with H alpha luminosity and infra-red luminosity, but also suggesting a single, fundamental relation valid over the last 10 Gyrs, relating the dark-matter halo mass and quenching of star-formation across cosmic time. HiZELS is probing a large variety of environments, enabling us to detail the dependence of star formation activity on environment and stellar mass, reconciling previous contradictory results in the literature and providing a much sharper view of our understanding at z similar to 1
Evaluating the effectiveness of abbreviated breast MRI (abMRI) interpretation training for mammogram readers : a multi-centre study assessing diagnostic performance, using an enriched dataset
Background
Abbreviated breast MRI (abMRI) is being introduced in breast screening trials and clinical practice, particularly for women with dense breasts. Upscaling abMRI provision requires the workforce of mammogram readers to learn to effectively interpret abMRI.
The purpose of this study was to examine the diagnostic accuracy of mammogram readers to interpret abMRI after a single day of standardised small-group training and to compare diagnostic performance of mammogram readers experienced in full-protocol breast MRI (fpMRI) interpretation (Group 1) with that of those without fpMRI interpretation experience (Group 2).
Methods
Mammogram readers were recruited from six NHS Breast Screening Programme sites. Small-group hands-on workstation training was provided, with subsequent prospective, independent, blinded interpretation of an enriched dataset with known outcome. A simplified form of abMRI (first post-contrast subtracted images (FAST MRI), displayed as maximum-intensity projection (MIP) and subtracted slice stack) was used. Per-breast and per-lesion diagnostic accuracy analysis was undertaken, with comparison across groups, and double-reading simulation of a consecutive screening subset.
Results
37 readers (Group 1: 17, Group 2: 20) completed the reading task of 125 scans (250 breasts) (total = 9250 reads). Overall sensitivity was 86% (95% confidence interval (CI) 84–87%; 1776/2072) and specificity 86% (95%CI 85–86%; 6140/7178). Group 1 showed significantly higher sensitivity (843/952; 89%; 95%CI 86–91%) and higher specificity (2957/3298; 90%; 95%CI 89–91%) than Group 2 (sensitivity = 83%; 95%CI 81–85% (933/1120) p < 0.0001; specificity = 82%; 95%CI 81–83% (3183/3880) p < 0.0001). Inter-reader agreement was higher for Group 1 (kappa = 0.73; 95%CI 0.68–0.79) than for Group 2 (kappa = 0.51; 95%CI 0.45–0.56). Specificity improved for Group 2, from the first 55 cases (81%) to the remaining 70 (83%) (p = 0.02) but not for Group 1 (90–89% p = 0.44), whereas sensitivity remained consistent for both Group 1 (88–89%) and Group 2 (83–84%).
Conclusions
Single-day abMRI interpretation training for mammogram readers achieved an overall diagnostic performance within benchmarks published for fpMRI but was insufficient for diagnostic accuracy of mammogram readers new to breast MRI to match that of experienced fpMRI readers. Novice MRI reader performance improved during the reading task, suggesting that additional training could further narrow this performance gap