ABSTRACT
We present early science results from the First Large Absorption Survey in H i (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen (H i) gas at cosmological ...distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for H i absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between z = 0.34 and 0.79 over a sky area of approximately 50 deg2. In a purely blind search, we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the H i spin temperature of Tspin = 100 K and source covering fraction cf = 1, the total comoving absorption path-length sensitive to all Damped Lyman α Absorbers (DLAs; NH i ≥ 2 × 1020 cm−2) is ΔX = 6.6 ± 0.3 (Δz = 3.7 ± 0.2) and super-DLAs (NH i ≥ 2 × 1021 cm−2) is ΔX = 111 ± 6 (Δz= 63 ± 3). We estimate upper limits on the H i column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross-matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at z = 0.3562 towards NVSS J224500−343030, with a column density of $N_{\rm H\,\small{I}} = (1.2 \pm 0.1) \times 10^{20}\, (T_{\rm spin}/100\, \mathrm{K})$ cm−2. The absorber is associated with GAMA J22450.05−343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive (MH i ≳ 3 × 109 M⊙) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.
Cross‐boundary fluxes of organisms and matter, termed “subsidies,” are now recognized to be reciprocal and of roughly equal importance for both aquatic and terrestrial systems, even if terrestrial ...input to aquatic ecosystems has received most attention. The magnitude of aquatic‐to‐terrestrial subsidies is well documented, but the drivers behind these subsidies and their utilization by terrestrial consumers are characteristically local‐scale studies, limiting the inferences that can be drawn for broader geographic scales. We therefore built and analyzed a database of stable isotope data extracted from 21 studies worldwide, to identify both landscape‐scale (catchment) and local‐scale (100‐m riparian zone) variables that may affect the diet of terrestrial predators in riparian ecosystems. Our meta‐analysis revealed a greater magnitude of aquatic‐to‐terrestrial subsidies (>50%) than previously reported, albeit with large geographic and inter‐annual variations. Moreover, we demonstrated a large effect of landscape‐scale factors on aquatic‐to‐terrestrial subsidies, particularly anthropogenic land use and tree cover. Local human population was the only relevant factor at the local scale. We also found that studies on landscape‐scale and anthropogenic land use effects on aquatic‐to‐terrestrial subsidies are strongly under‐represented in the ecological literature, which limits the general inferences that can currently be drawn about landscape effects. We suggest that landscape‐scale studies could improve our understanding of how land use and environmental change might influence future patterns of biodiversity and ecosystem function.
von Willebrand disease (VWD) is a commonly encountered inherited bleeding disorder affecting both males and females, causing mucous membrane and skin bleeding symptoms, and bleeding with surgical or ...other haemostatic challenges. VWD may be disproportionately symptomatic in women of child-bearing age. It may also occur less frequently as an acquired disorder (acquired von Willebrand syndrome). VWD is caused by deficiency or dysfunction of von Willebrand factor (VWF), a plasma protein that mediates platelet haemostatic function and stabilizes blood coagulation factor VIII. The pathophysiology, classification, diagnosis and management of VWD are relatively complex, but understanding them is important for proper diagnosis and management of patients with VWD. These evidence-based guidelines for diagnosis and management of VWD from the National Heart, Lung, and Blood Institute (NHLBI) Expert Panel (USA) review relevant publications, summarize current understanding of VWD pathophysiology and classification, and present consensus diagnostic and management recommendations based on analysis of the literature and expert opinion. They also suggest an approach for clinical and laboratory evaluation of individuals with bleeding symptoms, history of bleeding or conditions associated with increased bleeding risk. This document summarizes needs for further research in VWF, VWD and bleeding disorders, including clinical research to obtain more objective information about bleeding symptoms, advancements in diagnostic and therapeutic tools, and enhancement in the education and training of clinicians and scientists in bleeding and thrombotic disorders. The NHLBI Web site (http://www.nhlbi.nih.gov/guidelines/vwd) has a more detailed document, a synopsis of these recommendations, and patient education information.
Unlike at lower redshift, where there is a 40 per cent detection rate, surveys for 21-cm absorption arising within the hosts of z 1 radio galaxies and quasars have been remarkably unsuccessful. ...Curran et al. (2008) suggest that this is due to the high-redshift selection biasing towards the most optically bright objects those most luminous in the ultraviolet (UV) in the rest-frame, where the gas is ionized by the active galactic nucleus. They therefore argue that there must be a population of fainter objects in which the hydrogen is not ionized and which exhibit a similar detection rate as at lower redshifts. In order to find this 'missing' gas at high redshift, we have therefore undertaken a survey of z 2 radio sources, selected by optical faintness. Despite having optical magnitudes which indicate that the targets have UV luminosities below the threshold where all of the gas is ionized, there were no detections in any of the eight sources for which useable data were obtained. Upon an analysis of the spectral energy distributions, ionizing photon rates can only be determined for three of these, all of which suggest that the objects are above the highest luminosity of a current 21-cm detection. The possibility that the other five could be located at lower photon rates cannot be ruled out, although zero detections out of five are not statistically significant. Another possible cause of the non-detections is that our selection biases the sample towards sources which are very steep in the radio band, with a mean spectral index of 〈α〉 = −1.0, cf. −0.3 for both the 21-cm detections and UV luminous non-detections. This adds the further possibility that the sources have very extended emission, which would have the effect of reducing the coverage by the putative absorbing gas, thus decreasing the sensitivity of the observation.
ABSTRACT
Obscuration of quasars by accreted gas and dust, or dusty intervening galaxies, can cause active galactic nuclei (AGN) to be missed in optically selected surveys. Radio observations can ...overcome this dust bias. In particular, radio surveys searching for H i absorption inform us on how the AGN can impact on the cold neutral gas medium within the host galaxy, or the population of intervening galaxies through the observed line of sight gas kinematics. We present the results of an H i absorption line survey at 0.4 < z < 1 towards 34 obscured quasars with the Australian SKA Pathfinder (ASKAP) commissioning array. We detect three H i absorption lines, with one of these systems previously unknown. Through optical follow-up for two sources, we find that in all detections the H i gas is associated with the AGN, and hence that these AGN are obscured by material within their host galaxies. Most of our sample are compact, and in addition, are either gigahertz peaked spectrum (GPS), or steep spectrum (CSS) sources, both thought to represent young or recently re-triggered radio AGN. The radio spectral energy distribution classifications for our sample agree with galaxy evolution models in which the obscured AGN has only recently become active. Our associated H i detection rate for GPS and compact SS sources matches those of other surveys towards such sources. We also find shallow and asymmetric H i absorption features, which agrees with previous findings that the cold neutral medium in compact radio galaxies is typically kinematically disturbed by the AGN.
This paper is the second in a series describing the Sydney University Molonglo Sky Survey (SUMSS) being carried out at 843 MHz with the Molonglo Observatory Synthesis Telescope (MOST). The survey ...will consist of ∼590 4.3°× 4.3° mosaic images with 45 × 45 cosec|δ| arcsec2 resolution, and a source catalogue. In this paper we describe the initial release (version 1.0) of the source catalogue consisting of 107 765 radio sources made by fitting elliptical Gaussians in 271 SUMSS 4.3°× 4.3° mosaics to a limiting peak brightness of 6 mJy beam−1 at δ≤−50° and 10 mJy beam−1 at δ > −50°. The catalogue covers approximately 3500 deg2 of the southern sky with δ≤−30°, about 43 per cent of the total survey area. Positions in the catalogue are accurate to within 1–2 arcsec for sources with peak brightness A843≥ 20 mJy beam−1 and are always better than 10 arcsec. The internal flux density scale is accurate to within 3 per cent. Image artefacts have been classified using a decision tree, which correctly identifies and rejects spurious sources in over 96 per cent of cases. Analysis of the catalogue shows that it is highly uniform and is complete to 8 mJy at δ≤−50° and 18 mJy at δ > −50°. In this release of the catalogue about 7000 sources are found in the overlap region with the National Radio Astronomy Observatories Very Large Array Sky Survey at 1.4 GHz. We calculate a median spectral index of α=−0.83 between 1.4 GHz and 843 MHz. This version of the catalogue will be released via the World Wide Web with future updates as new mosaics are released.
The Galaxy And Mass Assembly (GAMA) survey is a multiwavelength photometric and spectroscopic survey, using the AAOmega spectrograph on the Anglo-Australian Telescope to obtain spectra for up to ∼300 ...000 galaxies over 280 deg2, to a limiting magnitude of r
pet < 19.8 mag. The target galaxies are distributed over 0 < z 0.5 with a median redshift of z 0.2, although the redshift distribution includes a small number of systems, primarily quasars, at higher redshifts, up to and beyond z = 1. The redshift accuracy ranges from σ
v
50 km s−1 to σ
v
100 km s−1 depending on the signal-to-noise ratio of the spectrum. Here we describe the GAMA spectroscopic reduction and analysis pipeline. We present the steps involved in taking the raw two-dimensional spectroscopic images through to flux-calibrated one-dimensional spectra. The resulting GAMA spectra cover an observed wavelength range of 3750 λ 8850 Å at a resolution of R 1300. The final flux calibration is typically accurate to 10-20 per cent, although the reliability is worse at the extreme wavelength ends, and poorer in the blue than the red. We present details of the measurement of emission and absorption features in the GAMA spectra. These measurements are characterized through a variety of quality control analyses detailing the robustness and reliability of the measurements. We illustrate the quality of the measurements with a brief exploration of elementary emission line properties of the galaxies in the GAMA sample. We demonstrate the luminosity dependence of the Balmer decrement, consistent with previously published results, and explore further how Balmer decrement varies with galaxy mass and redshift. We also investigate the mass and redshift dependencies of the N ii/Hα versus O iii/Hβ spectral diagnostic diagram, commonly used to discriminate between star forming and nuclear activity in galaxies.
Fast radio bursts (FRBs) are millisecond-duration pulses of radio emission originating from extragalactic distances. Radio dispersion is imparted on each burst by intervening plasma, mostly located ...in the intergalactic medium. In this work, we observe the burst FRB 20220610A and localize it to a morphologically complex host galaxy system at redshift 1.016 ± 0.002. The burst redshift and dispersion measure are consistent with passage through a substantial column of plasma in the intergalactic medium and extend the relationship between those quantities measured at lower redshift. The burst shows evidence for passage through additional turbulent magnetized plasma, potentially associated with the host galaxy. We use the burst energy of 2 × 10
42
erg to revise the empirical maximum energy of an FRB.
Editor’s summary
Fast radio bursts (FRBs) are brief flashes of radio emission from extragalactic sources. Ryder
et al
. detected a FRB and localized its source to a galaxy at a redshift of about 1, more than halfway back to the Big Bang. The burst is unusually bright, challenging models of the FRB emission mechanism. The authors also investigated how the intergalactic medium causes dispersion of the radio waves, finding more dispersion than expected from a correlation measured at lower redshift. They inferred the presence of magnetized plasma within the host galaxy, which has a complex morphology. —Keith T. Smith
A fast radio burst is localized to a distant galaxy, indicating that its intrinsic brightness is unusually high.
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