A5007075614- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Planetary Science and Exploration
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Space Exploration and Technology
- Solar and Space Plasma Dynamics
- Astrophysics and Cosmic Phenomena
- Isotope Analysis in Ecology
- High-pressure geophysics and materials
- Space Science and Extraterrestrial Life
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Adaptive optics and wavefront sensing
- Atomic and Molecular Physics
- Tribology and Lubrication Engineering
- Calibration and Measurement Techniques
- Geological and Geochemical Analysis
- Gamma-ray bursts and supernovae
- Photosynthetic Processes and Mechanisms
Cardiff University
2016-2025
UK Astronomy Technology Centre
2002-2024
University of St Andrews
2010-2022
University of Cambridge
2017-2020
St. Andrews University
2004-2013
Andrews University
2004-2010
Scottish Universities Physics Alliance
2007-2009
University of Manchester
2008
Alliance University
2008
Royal Observatory
2002-2006
In this paper a simple model for the steady state evolution of debris disks due to collisions is developed and confronted with properties emerging population seven Sun-like stars that have hot dust at <10 AU. The shows there maximum possible disk mass given age, since more massive primordial process their faster. corresponding luminosity fmax = 0.16 × 10-3r7/3t, where r radius in AU tage system age Myr. majority (4/7) exceed limit by ≫1000 so cannot be products asteroid belts; rather,...
Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed structure were not able probe disk midplanes, where most the mass is concentrated planet formation takes place. Using Atacama Large Millimeter/submillimeter Array we detected a pair trailing symmetric arms surrounding star Elias 2-27. The extend outer regions can be traced down midplane. These millimeter-wave also...
One-Sided Story from Disk In young analogs of the solar system, ongoing erosion comets and nascent planets produces dusty debris that is eventually expelled by host star. Gas should also be released in this process when volatile ices sublimate, but it detected less often. Using Atacama Large Millimeter/Submillimeter Array, Dent et al. (p. 1490 , published online 6 March; see Perspective Brandeker ) mapped a highly asymmetric disk dust carbon monoxide orbiting planet-hosting star, β Pictoris....
Dust emission around the nearby star Eridani has been imaged using a new submillimeter camera (the Submillimetre Common-User Bolometer Array at James Clerk Maxwell Telescope). At an 850 μm wavelength, ring of dust is seen peaking 60 AU from and with much lower inside 30 AU. The mass least ~0.01 M⊕ in dust, while upper limit 0.4 molecular gas imposed by CO observations. total comparable to estimated amount material, 0.04-0.3 M⊕, comets orbiting solar system. most probable origin structure...
In this paper a simple analytical model for the steady-state evolution of debris disks due to collisions is confronted with Spitzer observations main sequence A stars. All stars are assumed have planetesimal belts distribution initial masses and radii. disk mass constant until largest planetesimals reach collisional equilibrium whereupon falls off oc 1/t. We find that detection statistics trends seen at both 24 70um can be fitted well by model. While there no need invoke stochastic or...
Using the MIPS instrument on Spitzer, we have searched for infrared excesses around a sample of 82 stars, mostly F, G, and K main-sequence field along with small number nearby M stars. These stars were selected their suitability future observations by variety planet-finding techniques. provide information asteroidal cometary material orbiting these data that can be correlated any planets may eventually found. We found significant excess 70 μm emission toward 12 Combined an earlier study,...
We present dust continuum observations of the protoplanetary disk surrounding pre-main-sequence star AS 209, spanning more than an order magnitude in wavelength from 0.88 to 9.8 mm. The was observed with subarcsecond angular resolution (02–05) investigate radial variations its properties. At longer wavelengths, emission structure is notably compact, providing model-independent evidence for changes grain properties across disk. find that physical models which reproduce require a dependence...
We report on multifrequency linear polarization monitoring of 15 active galactic nuclei containing highly relativistic jets with apparent speeds from ∼4c to >40c. The measurements were obtained at optical, 1 mm, and 3 mm wavelengths, 7 the Very Long Baseline Array. data show a wide range in degree among sources, <1% >30%, interday variability individual sources. properties suggest separation sample into three groups low, intermediate, high core (LVP, IVP, HVP, respectively). are partially...
Debris discs are evidence of the ongoing destructive collisions between planetesimals, and their presence around stars also suggests that planets exist in these systems. In this paper, we present submillimetre images thermal emission from debris formed SCUBA-2 Observations Nearby Stars (SONS) survey, one seven legacy surveys undertaken on James Clerk Maxwell Telescope 2012 2015. The overall results survey presented form 850 μm (and 450 μm, where possible) fluxes for observed fields. Excess...
We present new results from the Disks@EVLA program for two young stars: CY Tau and DoAr 25. trace continuum emission arising their circusmtellar disks spatially resolved observations, down to tens of AU scales, at {\lambda} = 0.9, 2.8, 8.0, 9.8 mm DoAr25 1.3, 7.1 Tau. Additionally, we constrain amount whose origin is different thermal dust 5 cm observations. Directly interferometric data, find that observations 7 1 a compact disk while millimeter-wave an extended structure. From physical...
We present resolved Herschel images of a circumbinary debris disc in the 99 Herculis system. The primary is late F-type star. binary orbit well characterized and we conclude that misaligned with plane. Two different models can explain observed structure. first model ring polar orbits move plane perpendicular to pericentre direction. favour this interpretation because it includes effect secular perturbations survive for Gyr time-scales. second ring. Because there an ambiguity orientation...
The Herschel DEBRIS (Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre) survey brings us unique perspective on study of debris discs around main-sequence A-type stars. by design, offers remarkable data set with which to investigate cold disc properties. statistical analysis 100 and 160 μm for 86 A stars yields lower than previously found rate. Considering better 3σ excess sources, we find detection rate ≥24 ± 5 per cent at is similar F/G/K-spectral type While...
We present the first results from B-fields In STar-forming Region Observations (BISTRO) survey, using Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) camera, with its associated polarimeter (POL-2), on James Clerk Maxwell Telescope (JCMT) in Hawaii. discuss survey's aims and objectives. describe rationale behind questions which survey will aim to answer. The most important of these is role magnetic fields star formation process scale individual filaments cores dense regions. data...
For over a decade, the structure of inner cavity in transition disk TW Hydrae has been subject debate. Modeling with data obtained at different wavelengths led to variety proposed structures. Rather than being inconsistent, individual models might point faces physical processes going on disks, such as dust growth and planet formation. Our aim is investigate again find what extent we can reconcile apparent model differences. A large set high-angular-resolution was collected from near-infrared...
The recent candidate detection of ~1 ppb phosphine in the middle atmosphere Venus is so unexpected that it requires an exhaustive search for explanations its origin. Phosphorus-containing species have not been modelled Venus' before and our work represents first attempt to model phosphorus Venusian atmosphere. We thoroughly explore potential pathways formation a environment, including planet's atmosphere, cloud haze layers, surface, subsurface. investigate gas reactions, geochemical...
We present first results from a submillimeter continuum survey of the Galactic center "central molecular zone" (CMZ), made with Submillimeter Common-User Bolometer Array (SCUBA) on James Clerk Maxwell Telescope. SCUBA's scan-map mode has allowed us to make extremely wide field maps thermal dust emission unprecedented speed and sensitivity. also discuss some issues related elimination artifacts in data. Our simultaneous 850/450 μm have total size approximately 28 × 05 (400 75 pc) elongated...
We describe results from a survey for J = 3–2 12CO emission visible stars classified as having an infrared excess. The line is clearly detected in 21 objects, and significant molecular gas (⩾10−3 Jupiter masses) found to be common targets with excesses ⩾0.01 (⩾56 per cent of objects), but rare those smaller (∼10 objects).
We report the detection of linear polarization from Sgr A* at 750, 850, 1350, and 2000 µm which confirms contribution synchrotron radiation. From lack longer wavelengths, it appears to arise in millimeter/submillimeter excess. There are large position angle changes between millimeter submillimeter results, these discussed terms a polarized dust various models. In model that best explains data, radiation excess is self-absorbed region becomes optically thin submillimeter. This implies arises...
New submillimeter images have been obtained of the dust disk around nearby K2 V star Eridani, with total data set now spanning 5 yr. These show distribution dusty debris generated by comet collisions, reflecting clearing and perturbations planets, may give insights to early conditions in solar system. The structure seen Eri at 850 μm published 1998 is confirmed new observations, same also an image for first time 450 μm. inclined ≈25° sky plane, emission peaking 65 AU, a 105 AU radius outer...
We present the first published maps of magnetic fields in prestellar cores to test theoretical ideas about way which field geometry affects star formation process. The observations are JCMT-SCUBA λ850 μm thermal emission from dust. Linear polarizations at typically 10 or more independent positions each three objects, L1544, L183, and L43, were measured, geometries plane sky mapped polarization directions. observed all objects appear smooth fairly uniform. In L1544 L183 mean an angle ~30°...
An excess of far-infrared emission is seen towards the nearby G8 V star τ Ceti, and this has been attributed to orbiting dust particles generated in planetesimal collisions. A new 850-µm image shows that there indeed such a debris disc, extending out ≈55 au (15 arcsec) radius. This first disc around Sun-like late main-sequence age be confirmed by imaging. The mass at least an order magnitude greater than Kuiper Belt, although dimensions systems are very similar Ceti exceeds Sun. Modelling...
New submillimeter images of the cold dust emission around nearby main-sequence star Fomalhaut are presented. Observations at a wavelength 450 ?m, where telescope beam size is equivalent to resolution 50 AU, reveal that encircled by significantly nonaxisymmetric inclined ring. Smooth axisymmetric models ring suggest existence least one clump with an estimated flux about 5% total from disk, thus implying mass 0.075 lunar masses. At data, this could instead be arc. The most plausible...