Research Articles (Physics)

Permanent URI for this collection

https://hdl.handle.net/10566/726

Browse

Now showing 1 - 20 of 515

The discovery of a z = 0.7092 oh megamaser with the mightee survey
(Oxford University Press, 2024) Jarvis, Matthew; Baker, Andrew; Heywood, Ian
We present the discovery of the most distant OH megamaser (OHM) to be observed in the main lines, using data from the MeerKAT International Giga-Hertz Tiered Extragalactic Exploration (MIGHTEE) survey. At a newly measured redshift of z = 0.7092, the system has strong emission in both the 1665 MHz (L ≈ 2500 L-) and 1667 MHz (L ≈ 4.5 × 104 L-) transitions, with both narrow and broad components. We interpret the broad line as a high-velocity-dispersion component of the 1667 MHz transition, with velocity v ∼330 km s-1 with respect to the systemic velocity. The host galaxy has a stellar mass of M = 2.95 × 1010 M- and a star formation rate of SFR = 371 M- yr-1, placing it ∼1.5 dex above the main sequence for star-forming galaxies at this redshift, and can be classified as an ultraluminous infrared galaxy. Alongside the optical imaging data, which exhibit evidence for a tidal tail, this suggests that the OHM arises from a system that is currently undergoing a merger, which is stimulating star formation and providing the necessary conditions for pumping the OH molecule to saturation
Concerto at apex on-sky performance in continuum
(EDP Sciences, 2024) Hu, Wenkai; Beelen, Alexandre; Lagache, Guilaine
CarbON CII line in post-rEionisation and ReionisaTiOn epoch (CONCERTO) instrument is a low-resolution mapping spectrometer based on lumped element kinetic inductance detector (LEKIDs) technology, operating at 130-310 GHz. It was installed on the 12-metre APEX telescope in Chile in April 2021 and was in operation until May 2023. CONCERTO’s main goals were the observation of [CII]-emission line fluctuations at high redshift and of the Sunyaev–Zel’dovich (SZ) signal from galaxy clusters. Aims. We present the data processing algorithms and the performance of CONCERTO in continuum by analysing the data from the commissioning and scientific observations.Methods. We developed a standard data processing pipeline to proceed from the raw data to continuum maps. Using a large dataset of calibrators (Uranus, Mars, and quasars) acquired in 2021 and 2022 at the APEX telescope across a wide range of atmospheric conditions, we measured the CONCERTO continuum performance and tested its stability against observing conditions. Further, using observations on the COSMOS field and observations targeting a distant sub-millimetre galaxy in the UDS field, we assessed the robustness of the CONCERTO performance on faint sources and compared our measurements with expectations.
Comparisons between resolved star formation rate and gas tracers in the strongly lensed galaxy sdss j0901+1814 at cosmic noon
(American Astronomical Society, 2024) Chen, Qingxiang; Baker, Andrew J; Sharon, Chelsea E
We report new radio observations of SDSSJ090122.37+181432.3, a strongly lensed star-forming galaxy at z =2.26. We image 1.4GHz (L-band) and 3GHz (S-band) continuum using the Very Large Array (VLA) and 1.2 mm (band 6) continuum with Atacama Large Millimeter/submillimeter Array, in addition to the CO(7–6) and CI(3P2→3P1) lines, all at 1 TIR 2.65 0.24 7resolution. Based on the VLA integrated flux densities, we decompose the radio spectrum into its free–free (FF) and nonthermal components. The infrared–radio correlation parameter q 0.31 =+ is consistent with expectations for star-forming galaxies. We obtain radio continuum-derived star formation rates (SFRs) that are free of dust extinction, finding 620+ 280 220 280+ 460 120 M  yr 1 M  yr 1- , 230+ 570 160 M  yr 1- , and- from the FF emission, nonthermal emission, and when accounting for both emission processes, respectively, in agreement with previous results. We estimate the gas mass from the CI(3P2→3P1) line as Mgas = (1.2±0.2)×1011M☉, which is consistent with prior CO(1–0)-derived gas masses. Using our new IR and radio continuum data to map the SFR, we assess the dependence of the Schmidt–Kennicutt relation on choices of SFR and gas tracer for ∼kpc scales. The different SFR tracers yield different slopes, with the IR being the steepest, potentially due to highly obscured star formation in J0901. The radio continuum maps have the lowest slopes and overall fidelity for mapping the SFR, despite producing consistent total SFRs. We also find that the Schmidt-Kennicutt relation slope is flattest when using CO(7–6) or C I(3P2→3P1) to trace gas mass, suggesting that those transitions are not suitable for tracing the bulk molecular gas in galaxies like J0901.
Charge radii of thallium isotopes near the n = 126 shell closure
(American Physical Society, 2024) Yue, Z.; Orce, José Nicolás; Barzakh, A. E.
The changes in the mean-squared charge radius of 209Tlg (N = 128) and 207Tlm (N = 126) relative to 205Tl have been measured for the first time using the in-source laser resonance-ionization spectroscopy technique with the Laser Ion Source and Trap (LIST) at ISOLDE (CERN). The application of the LIST suppresses the dominant background from isobaric francium isotopes and allows access to thallium nuclides with A 207. The characteristic kink in the charge radii at the N = 126 neutron shell closure, as well as the odd-even effect similar to that in the adjacent bismuth, lead, and mercury isotopic chains, have been observed. The self-consistent theory of finite Fermi systems based on the energy density functional by Fayans et al. reproduces the behavior of charge radii in these isotopic chains near N = 126. The comparison with calculations in the framework of the relativistic mean field (RMF) approach is also presented. In the case of the Fayans functional it is a specific form of pairing interaction with the dependence on the density gradient that is essential to provide agreement with the experimental charge radii. In particular, the kink is reproduced without the inversion of g9/2 and i11/2 neutron single-particle states, which is a prerequisite to correctly describe the kink in the RMF models.
Proton-unbound states in AI 24 relevant for the mg 23 (p,γ) reaction in novae
(American Physical Society, 2024) Vyfers, E. C; Pesudo, V; Triambak, S
Background: The nucleosynthesis of several proton-rich nuclei is determined by radiative proton-capture reactions on unstable nuclei in nova explosions. One such reaction is 23Mg(p, γ ) 24Al, which links the NeNa and MgAl cycles in oxygen-neon novae. Purpose: The purpose of our study is to extract 23Mg(p, γ ) resonance strengths from proton-unbound states in 24Al, produced via the 24Mg(3 He,t) reaction. Methods: A beam of 3 He2+ ions at 50.7 MeV is used to produce the states of interest in 24Al. Proton-triton angular correlations are measured with a K = 600 QDD magnetic spectrometer and a silicon detector array, located at iThemba LABS, South Africa. Results: We measure the excitation energies of the four lowest proton-unbound states in 24Al and place lower limits on p/ values for these four states. Together with shell-model calculations of partial γ widths, the experimental data are also used to determine resonance strengths for the four lowest 23Mg(p, γ ) 24Al resonances. Conclusions: The energy of the dominant first 23Mg(p, γ ) resonance is determined to be Er = 478 ± 4 keV, with a resonance strength of ωγ = 19 ± 9 meV.
Cosmology from LOFAR two-metre sky survey data release 2: cross-correlation with the cosmic microwave background
(EDP Sciences, 2024) Szymon Nakoneczny; Jarvis M.J.
Aims. We combined the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) second data release (DR2) catalogue with gravitational lensing maps from the cosmic microwave background (CMB) to place constraints on the bias evolution of LoTSS-detected radio galaxies, and on the amplitude of matter perturbations. Methods. We constructed a flux-limited catalogue from LoTSS DR2, and analysed its harmonic-space cross-correlation with CMB lensing maps from Planck, Cℓgκ, as well as its auto-correlation, Cℓgg. We explored the models describing the redshift evolution of the large-scale radio galaxy bias, discriminating between them through the combination of both Cℓgκ and Cℓgg. Fixing the bias evolution, we then used these data to place constraints on the amplitude of large-scale density fluctuations, parametrised by σ8. Results. We report the significance of the Cℓgκ signal at a level of 26.6σ. We determined that a linear bias evolution of the form bg(z) = bg,D/D(z), where D(z) is the growth rate, is able to provide a good description of the data, and we measured bg,D = 1.41 ± 0.06 for a sample that is flux limited at 1.5 mJy, for scales ℓ < 250 for Cℓgg, and ℓ < 500 for Cℓgκ. At the sample’s median redshift, we obtained b(z = 0.82) = 2.34 ± 0.10. Using σ8 as a free parameter, while keeping other cosmological parameters fixed to the Planck values, we found fluctuations of σ8 = 0.75+0.05-0.04. The result is in agreement with weak lensing surveys, and at 1σ difference with Planck CMB constraints. We also attempted to detect the late-time-integrated Sachs-Wolfe effect with LOFAR data; however, with the current sky coverage, the cross-correlation with CMB temperature maps is consistent with zero. Our results are an important step towards constraining cosmology with radio continuum surveys from LOFAR and other future large radio surveys.
DEVILS/MIGHTEE/GAMA/DINGO: the impact of SFR time-scales on the SFR-radio luminosity correlation
(Oxford, 2024) Cook, Robin H. W.; Davies, Luke J. M; Knowles, Kenda
The tight relationship between infrared luminosity ( L TIR ) and 1.4 GHz radio continuum luminosity ( L 1 . 4 GHz ) has proven useful for understanding star formation free from dust obscuration. Infrared emission in star-forming galaxies typically arises from recently formed, dust-enshrouded stars, whereas radio synchrotron emission is expected from subsequent supernovae. By leveraging the wealth of ancillary far -ultra violet –far-infrared photometry from the Deep Extragalactic VIsible Legacy Survey and Galaxy and Mass Assembly surveys, combined with 1.4 GHz observations from the Meer Karoo Array Telescope International GHz Tiered Extragalactic Exploration survey and Deep Investigation of Neutral Gas Origin projects, we investigate the impact of time-scale differences between far -ultraviolet –far-infrared and radio-derived star formation rate (SFR) tracers. We examine how the spectral energy distribution (SED)-derived star formation histories (SFHs) of galaxies can be used to explain discrepancies in these SFR tracers, which are sensitive to different time scales. Galaxies exhibiting an increasing SFH have systematically higher L TIR and SED-derived SFRs than predicted from their 1.4 GHz radio luminosity. This indicates that insufficient time has passed for subsequent supernovae-driven radio emissions to accumulate. We show that backtracking the SFR(t) of galaxies along their SED-derived SFHs to a time several hundred mega years prior to their observed epoch will both linearize the SFR–L 1 . 4 GHz relation and reduce the overall scatter. The minimum scatter in the SFR(t)–L 1 . 4 GHz is reached at 200 –300 Myrprior, consistent with theoretical predictions for the time-scales required to disperse the cosmic ray electrons responsible for the synchrotron emission.
Constraining the growth rate on linear scales by combining SKAO and DESI surveys
(Springer, 2024) Simthembile Dlamini; Sheean Jolicoeur; Roy Maartens
In the pursuit of understanding the large-scale structure of the Universe, the synergy between complementary cosmological surveys has proven to be a powerful tool. Using multiple tracers of the large-scale structure can significantly improve the constraints on cosmological parameters. We explore the potential of combining the Square Kilometre Array Observatory (SKAO) and the Dark Energy Spectroscopic Instrument (DESI) spectroscopic surveys to enhance precision on the growth rate of cosmic structures.We employ a multi-tracer Fisher analysis to estimate precision on the growth rate when using pairs of mock surveys that are based on SKAO and DESI specifications. The pairs are at both low and high redshifts. For SKA-MID, we use the HI galaxy and the HI intensity mapping samples. In order to avoid the complexities and uncertainties at small scales, we confine the analysis to scales where linear perturbations are reliable. The consequent loss of signal in each individual survey is mitigated by the gains from the multi-tracer. After marginalising over cosmological and nuisance parameters, we find a significant improvement in the precision on the growth rate.
The SARAO MeerKAT 1.3 GHz galactic plane Survey
(Oxford, 2024) Woudt, P. A.; Goedhart, S; Cotton, W.D
We present the SARAO MeerKAT Galactic Plane Surv e y (SMGPS), a 1.3 GHz continuum surv e y of almost half of the Galactic Plane (251 ◦≤l ≤358 ◦and 2 ◦≤l ≤61 ◦at | b | ≤1 . ◦5). SMGPS is the largest, most sensitive, and highest angular resolution 1 GHz surv e y of the plane yet carried out, with an angular resolution of 8 arcsec and a broad-band root-mean-square sensitivity of ∼10–20 μJy beam −1 . Here, we describe the first publicly available data release from SMGPS which comprises data cubes of frequenc y-resolv ed images o v er 908–1656 MHz, power-la w fits to the images, and broad-band zeroth moment inte grated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the disco v ery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; impro v ed radio/mid-infrared classification of rare luminous blue variables and disco v ery of associated extended radio nebulae; new radio stars identified by Bayesian cross- matching techniques; the realization that many of the largest radio-quiet Wide-field Infrared Survey Explorer (WISE) H II region candidates are not true H II regions; and a large sample of previously undisco v ered background H I galaxies in the Zone of Avoidance.
Deep Learning Voigt Profiles. I. Single-Cloud Doublets
(2024) Stemock, Bryson; Hassan, Sultan; Churchill, Christopher W
Voigt profile (VP) decomposition of quasar absorption lines is key to studying intergalactic gas and the baryon cycle governing the formation and evolution of galaxies. The VP velocities, column densities, and Doppler b parameters inform us of the kinematic, chemical, and ionization conditions of these astrophysical environments. A drawback of traditional VP fitting is that it can be human-time intensive. With the coming next generation of large all-sky survey telescopes with multi object high-resolution spectrographs, the time demands will significantly outstrip our resources. Deep learning pipelines hold the promise to keep pace and deliver science-digestible data products. We explore the application of deep learning convolutional neural networks (CNNs) for predicting VP-fitted parameters directly from the normalized pixel flux values in quasar absorption line profiles. A CNN was applied to 56 single-component Mg II λλ2796, 2803 doublet absorption line systems observed with HIRES and UVES (R = 45,000). The CNN predictions were statistically indistinct from those of a traditional VP fitter. The advantage is that, once trained, the CNN processes systems ∼105 times faster than a human expert fitting VP profiles by hand. Our pilot study shows that CNNs hold promise to perform bulk analysis of quasar absorption line systems in the future.
The MeerKAT 1.3 GHz survey of the small magellanic cloud
(Oxford academy, 2024) Serylak Meciej; Cotton W.D; Filipovic M.D
Magellanic Cloud. The observations, at a central frequency of 1.3 GHz across a bandwidth of 0.8 GHz, encompass a field of view ∼7 ◦×7 ◦and result in images with resolution of 8 arcsec. The median broad-band Stokes I image Root Mean Squared noise value is ∼11 μJy beam −1 . The catalogue produced from these images contains 108 330 point sources and 517 compact extended sources. We also describe a UHF (544–1088 MHz) single pointing observation. We report the detection of a new confirmed Supernova Remnant (SNR; MCSNR J0100–7211) with an X-ray magnetar at its centre and 10 new SNR candidates. This is in addition to the detection of 21 previously confirmed SNRs and two previously noted SNR candidates. Our new SNR candidates have typical surface brightness an order of magnitude below those previously known, and on the whole they are larger. The high sensitivity of the MeerKAT surv e y also enabled us to detect the bright end of the SMC Planetary Nebulae (PNe) sample –point-like radio emission is associated with 38 of 102 optically known PNe, of which 19 are new detections. Lastly, we present the detection of three foreground radio stars amidst 11 circularly polarized sources, and a few examples of morphologically interesting background radio galaxies from which the radio ring galaxy ESO 029–G034 may represent a new type of radio object.
Infuence of Synthesis Method on Structural, Morphological, Magnetic, and Antimicrobial Properties of Fe‑Ag Nanoparticles
(Springer, 2023) Noukelag, Sandrine Kamdoum; Ngqoloda, Siphelo; Mewa‑Ngongang, Maxwell; Kotsedi, Lebogang; Razanamahandry, Lovasoa Christine; Ntwamp, Seteno; Arendse, Christopher; Maaza, Malik
This contribution reports on the development of two versatile and efcient methods, namely the green and gamma radiolysis for Fe-Ag nanoparticles (NPs) synthesis, characterization, and further their growth inhibition potential on some spoilage microorganisms. Green Ag/Fe2O3 NPs were obtained at Fe-Ag [3:1], annealing temperature of 800 °C for 2 h, and gamma irradiated Ag/Fe3O4 NPs were obtained at Fe-Ag [7:1], a 50 kGy dose. The characterization techniques were performed with these two samples whereby the sizes from crystallographic and microscopic analyses were 39.59 and 20.00 nm for Ag/Fe2O3 NPs, 28.57 and 15.37 nm for Ag/Fe3O4 NPs, respectively. The polycrystallinity nature observed from X-ray diffraction was in accordance with the selected area electron difraction. The vibrational properties confrmed the presence of bimetallic Fe-Ag NPs with the depiction of chemical bonds, Fe–O and Ag–O from attenuated total refection-Fourier transform infrared spectroscopy and elements Ag, Fe, O from energy-dispersive X-ray spectroscopy analyses. The magnetic properties carried out using a vibrating sample magnetometer suggested a superparamagnetic behavior for the Ag/Fe2O3 NPs and a ferromagnetic behavior for the Ag/Fe3O4 NPs. Overall, the green Ag/Fe2O3 NPs successfully inhibited the growth of spoilage yeasts Candida guilliermondii, Zygosaccharomyces fermentati, Zygosaccharomyces forentinus, and spoilage molds Botrytis cinerea, Penicillium expansum, Alternaria alstroemeriae.
Characterizing line-of-sight variability of polarized dust emission with future cmb experiments
(Oxford University Press, 2023) Bull, Philip; McBride, Lisa; Hensley, Brandon S
While Galactic dust emission is often accounted for in cosmic microwave background (CMB) analyses by fitting a two-parameter modified blackbody (MBB) model in each pixel, typically a number of such clouds are found along each line of sight and within each angular pixel, resulting in a superposition of their spectra. We study the effects of this superposition on pixel-based foreground fitting strategies by modeling the spectral energy distribution (SED) in each pixel as the integral of individual MBB spectra over various physically motivated statistical distributions of dust cloud properties. We show that fitting these SEDs with the two-parameter MBB model generally results in unbiased estimates of the CMB Stokes Q and U amplitudes per pixel, unless there are significant changes in both the dust SED and polarization angle along the line of sight, in which case significant (>10σ) biases are observed in an illustrative model.
Cosmic sands: the origin of dusty, star-forming galaxies in the epoch of reionization
(The astrophysical journal, 2023) Davé, Romeel; Lower, Sidney; Narayanan, Desika
We present the Cosmic Sands suite of cosmological zoom-in simulations based on the simba galaxy formation model in order to study the buildup of the first massive and dusty galaxies in the early universe. Residing in the most massive halos, we find that the compact proto-massive galaxies undergo nearly continuous mergers with smaller subhalos, boosting star formation rates (SFRs) and the buildup of stellar mass. The galaxies are already appreciably chemically evolved by z = 7, with modeled dust masses comparable to those inferred from observations in the same epoch, except for the most extreme systems. We track gas accretion onto the galaxies to understand how extreme SFRs can be sustained by these early systems. We find that smooth gas accretion can maintain SFRs above 250 M · yr-1, but to achieve SFRs that boost galaxies well above the main sequence, a larger perturbation like a gas-rich major merger is necessary to trigger a starburst episode. Post-processing the Cosmic Sands simulations with dust RT, we find that, while the infrared luminosities of the most-dust-rich galaxies are comparable to local ULIRGs, they are substantially dimmer than classical z = 2 submillimeter galaxies. We end with a discussion on the possible reasons for this discrepancy at the highest masses and the future work we intend to carry out to study the chemical enrichment of the earliest dusty galaxies.
Boundless baryons: how diffuse gas contributes to anisotropic tSZ signal around simulated three hundred clusters
(Oxford University Press, 2023) Davé, Romeel; Lokken, Martine; Cui, Weiguang
Upcoming advances in galaxy surveys and cosmic microwave background data will enable measurements of the anisotropic distribution of diffuse gas in filaments and superclusters at redshift z = 1 and beyond, observed through the thermal Sunyaev–Zel’dovich (tSZ) effect. These measurements will help distinguish between different astrophysical feedback models, account for baryons that appear to be ‘missing’ from the cosmic census, and present opportunities for using locally anisotropic tSZ statistics as cosmological probes. This study seeks to guide such future measurements by analysing whether diffuse intergalactic gas is a major contributor to anisotropic tSZ signal in THE THREE HUNDRED GIZMO-SIMBA hydrodynamic simulations. We apply multiple different halo boundary and temperature criteria to divide concentrated from diffuse gas at z = 1, then create mock Compton- y maps for the separated components. The maps from 98 simulation snapshots are centred on massive galaxy clusters, oriented by the most prominent filament axis in the galaxy distribution, and stacked. Results vary significantly depending on the definition used for diffuse gas, indicating that assumptions should be clearly defined when claiming observations of the warm-hot intergalactic medium. In all cases, the diffuse gas is important, contributing 25–60 per cent of the tSZ signal in the far field (>4 h−1 comoving Mpc) from the stacked clusters. The gas 1–2 virial radii from halo centres is especially key. Oriented stacking and environmental selections help to amplify the signal from the warm-hot intergalactic medium, which is aligned but less concentrated along the filament axis than the hot halo gas.
A unique, ring-like radio source with quadrilateral structure detected with machine learning
(Oxford University Press, 2023) Lochner, Michelle; Rudnick, Lawrence; Heywood, Ian
We report the discovery of a unique object in the MeerKAT Galaxy Cluster Le gacy Survey (MGCLS) using the machine learning anomaly detection framework ASTRONOMALY. This strange, ring-like source is 30 from the MGCLS field centred on Abell 209, and is not readily explained by simple physical models. With an assumed host galaxy at redshift 0.55, the luminosity (10 25 W Hz −1) is comparable to powerful radio galaxies. The source consists of a ring of emission 175 kpc across, quadrilateral enhanced brightness regions bearing resemblance to radio jets, two ‘ears’ separated by 368 kpc, and a diffuse envelope. All of the structures appear spectrally steep, ranging from −1.0 to −1.5. The ring has high polarization (25 per cent) except on the bright patches (< 10 per cent). We compare this source to the Odd Radio Circles recently discovered in ASKAP data and discuss several possible physical models, including a termination shock from starburst activity, an end-on radio galaxy, and a supermassive black hole merger event. No simple model can easily explain the observed structure of the source. This work, as well as other recent discoveries, demonstrates the power of unsupervised machine learning in mining large data sets for scientifically interesting sources.
An ∼600 pc view of the strongly lensed, massive main-sequence galaxy J0901: a baryon-dominated, thick turbulent rotating disk with a clumpy cold gas ring at z = 2.259
(The astrophysical journal, 2023) Baker, Andrew J.; Liu, Daizhong; Schreiber, N. M. Förster
We present a high-resolution kinematic study of the massive main-sequence star-forming galaxy (SFG) SDSS J090122.37+181432.3 (J0901) at z = 2.259, using ∼0.″36 Atacama Large Millimeter/submillimeter Array CO(3-2) and ∼0.″1-0.″5 SINFONI/VLT Hα observations. J0901 is a rare, strongly lensed but otherwise normal massive ( log ( M ⋆ / M ⊙ ) ∼ 11 ) main-sequence SFG, offering a unique opportunity to study a typical massive SFG under the microscope of lensing. Through forward dynamical modeling incorporating lensing deflection, we fit the CO and Hα kinematics in the image plane out to about one disk effective radius (R e ∼ 4 kpc) at an ∼600 pc delensed physical resolution along the kinematic major axis. Our results show high intrinsic dispersions of the cold molecular and warm ionized gas (σ 0,mol. ∼ 40 km s−1 and σ 0,ion. ∼ 66 km s−1) that remain constant out to R e; a moderately low dark matter fraction (f DM ∼ 0.3-0.4) within R e; and a centrally peaked Toomre Q parameter—agreeing well with the previously established σ 0 versus z, f DM versus Σbaryon, and Q's radial trends using large-sample non-lensed main-sequence SFGs. Our data further reveal a high stellar mass concentration within ∼1-2 kpc with little molecular gas, and a clumpy molecular gas ring-like structure at R ∼ 2-4 kpc, in line with the inside-out quenching scenario. Our further analysis indicates that J0901 had assembled half of its stellar mass only ∼400 Myr before its observed cosmic time, and the cold gas ring and dense central stellar component are consistent with signposts of a recent wet compaction event of a highly turbulent disk found in recent simulations. © 2023. The Author(s). Published by the American Astronomical Society.
Low-operational temperature for selective detection of xylene gas using a p-n CuO-ZnO heterostructure-based sensor
(Elsevier Ltd, 2023) Cummings, Franscious R; Maebana, Lekgolo M; Rapelang G., Motsoeneng; Zamaswazi P, Tshabalala
Xylene is not just considered detrimental to the environment but also hazardous to humans. Herein we report on xylene vapour detection using CuO-ZnO heterostructures containing various concentrations (0.1–2.0 wt%) of Zn, prepared via hydrothermal synthesis. X-ray diffraction, scanning, and transmission electron microscopy, as well as x-ray photoelectron spectroscopy, validated the formation of the CuO-ZnO heterostructure. Gas detection, sensitivity, selectivity, and stability tests of nine different gases, namely benzene, toluene, ethylbenzene, xylene, ethanol, methane, SO2, NO2, and CO2 at various operational temperatures were subsequently investigated. It was found that a CuO-ZnO heterostructure with 1.0 wt% Zn showed excellent selectivity towards 100 ppm of xylene at 100 °C.
Werner Eissner (1930–2022): a pioneer in computational atomic physics
(Atoms, 2023) Lynas-Gray, Anthony E.; Bhatia, Anand K.; Mendoza, Claudio; Nahar, Sultana
Werner Eissner (Figure 1), a pioneer in computational atomic physics, was born on 16 October 1930 in the city of Görlitz, Germany, to Bernhard and Frieda (née Eckert) Eissner. He lost both parents early in life, his father in the War and later his mother at the age of 15. He attended elementary school in his hometown (1937–1941) and high school in both Görlitz (1941–1945) and Lüdenscheid (1946–1951). His higher education was at Göttingen University (Preliminary Diploma in physics, 1954) and Tübingen University (Diploma under Professor Dr. Hubert Krüger, 1959, and doctorate degree under Professor Dr. Gerhard Elwert, 1967). His doctoral thesis dissertation was entitled “Rechnungen zur Elektronenstoßanregung der M-Schale von Wasserstoff und zur Polarisation des Stoßleuchtens der H𝛼 -Linie” (Calculations for the electron collision excitation of the M-shell of hydrogen and for the polarization of the collisionally excited H𝛼 line), which he presented in preliminary form at the Third International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC, 22–26 July 1963) held at University College London (UCL) [1]. For most of Werner’s career, he was a member of two major research groups in atomic physics led by Professor Michael J. Seaton FRS at UCL and by Professor Philip G. Burke FRS at Queen’s University Belfast (QUB) and Daresbury Laboratory (DL).
The bright extragalactic ALMA redshift survey (BEARS) – II. Millimetre photometry of gravitational lens candidates
(Oxford University Press, 2023) Bendo, George; Urquhart, S. A.; Baker, Andrew J.
We present 101- and 151-GHz ALMA continuum images for 85 fields selected from Herschel observations that have 500-μm flux densities >80 mJy and 250–500-μm colours consistent with z > 2, most of which are expected to be gravitationally lensed or hyperluminous infrared galaxies. Approximately half of the Herschel 500-μm sources were resolved into multiple ALMA sources, but 11 of the 15 brightest 500-μm Herschel sources correspond to individual ALMA sources. For the 37 fields containing either a single source with a spectroscopic redshift or two sources with the same spectroscopic redshift, we examined the colour temperatures and dust emissivity indices.

Browse

collection.page.browse.recent.head