A5091404609- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Additive Manufacturing and 3D Printing Technologies
- High Entropy Alloys Studies
- Additive Manufacturing Materials and Processes
- Particle physics theoretical and experimental studies
- High-pressure geophysics and materials
- Sensor Technology and Measurement Systems
- Radiation Therapy and Dosimetry
- Superconducting and THz Device Technology
- Solar and Space Plasma Dynamics
- Neutrino Physics Research
- Adaptive optics and wavefront sensing
- Soil Moisture and Remote Sensing
- Radio Wave Propagation Studies
- Telecommunications and Broadcasting Technologies
University of Cambridge
2019-2024
University College London
2011-2021
Cavendish Hospital
2019
University of Manchester
2005-2016
UCL Australia
2008-2016
Netherlands Institute for Radio Astronomy
2012-2016
Max Planck Society
2015
Max Planck Institute for Radio Astronomy
2015
University College Lahore
2014
SKA Observatory
2006-2012
We present the first data release of high-resolution ($\leq0.2$ arcsec) 1.5-GHz radio images 103 nearby galaxies from Palomar sample, observed with eMERLIN array, as part LeMMINGs survey. This sample includes which are active (LINER and Seyfert) quiescent (HII Absorption line galaxies, ALG), reclassified based upon revised emission-line diagrams. detect emission $\gtrsim$ 0.2 mJy for 47/103 (22/34 LINERS, 4/4 Seyferts, 16/51 HII 5/14 ALGs) sizes typically $\lesssim$100 pc. identify core...
The results of an extremely deep, 8-day long observation the central kpc nearby starburst galaxy M82 using MERLIN (Multi-Element Radio Linked Interferometer Network) at 5 GHz are presented. 17E-06 Jy/beam, rms noise level in naturally weighted image make it most sensitive high resolution radio made to date. Over 50 discrete sources detected, majority which supernova remnants, but with 13 identified as HII regions. Sizes, flux densities and brightnesses given for all detected sources, well...
We present high-sensitivity eMERLIN radio images of the Seyfert galaxy NGC 4151 at 1.5 GHz. compare new to those from archival MERLIN observations in 1993 determine change jet morphology 22 years between observations. report an increase by almost a factor 2 peak flux density central core component, C4, thought host black hole, but probable decrease some other components, possibly due adiabatic expansion. The indicates AGN which is currently active and feeding jet. detect no significant...
We present the second data release of high-resolution ($\leq0.2$ arcsec) 1.5-GHz radio images 177 nearby galaxies from Palomar sample, observed with e-MERLIN array, as part LeMMINGs (Legacy Multi-band Imaging Nearby Galaxy Sample) survey. Together 103 targets first release, this represents a complete sample 280 local active (LINER and Seyfert) inactive HII Absorption Line Galaxies, ALG). This large program is deepest survey Universe, $\gtrsim$10$^{17.6}$ W Hz$^{-1}$, regardless host nuclear...
From a combination of Multi-Element Radio-Linked Interferometer Network (MERLIN) and global Very Long Baseline Interferometry (VLBI) observations the starburst galaxy M82, images 36 discrete sources at resolutions ranging from ∼3 to ∼80 mas 1.7 GHz are presented. Of these sources, 32 identified as supernova remnants, two H ii regions three remain unclassified. Sizes, flux densities radio brightnesses given for all detected sources. Additionally, VLBI only data this project used image four...
A faint new radio source has been detected in the nuclear region of starburst galaxy M82 using MERLIN observations designed to monitor flux density evolution recent bright supernova SN2008iz. This was initially identified made between 1-5th May 2009 but had not present one week earlier, or any previous M82. In this paper we report discovery and monitoring its over first 9 months existence. The true nature remains unclear, discuss whether may be an unusual supernova, a supermassive blackhole...
Massive stars play an important role in both cluster and galactic evolution the rate at which they lose mass is a key driver of their own interaction with environment up to including SNe explosions. Young massive clusters provide ideal opportunity study co-eval population stars. We performed 3mm continuum observations Atacama Large Millimetre/submillimetre Array Galactic Westerlund 1, constituent determine mass-loss rates for diverse post-main sequence population. detected emission from 50...
What determines the nuclear radio emission in local galaxies? We combine optical [O III] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from LeMMINGs survey, of a statistically-complete sample 280 nearby, optically active (LINER Seyfert) inactive HII Absorption galaxies [ALG]) galaxies. Using luminosity ($L_{\rm [O~III]}$) as proxy for accretion power, follow distinct sequences optical-radio planes BH activity, which suggest different origins...
We present the results of a second epoch 18-cm global very long baseline interferometry (VLBI) observations, taken on 2001 February 23, central kiloparsec nearby starburst galaxy Messier 82. These observations further investigate structural and flux evolution most compact radio sources in region M82. The two objects M82 have been investigated (41.95+575 43.31+592). Using this recent data comparison with our previous VLBI earlier epochs European network we measure expansion velocities range...
The Scripted E-merlin Rfi-mitigation PipelinE for iNTerferometry (SERPent) is an automated reduction and RFI-mitigation procedure utilising the SumThreshold methodology (Offringa et al. 2010b), originally developed LOFAR pipeline. SERPent written in Parseltongue language enabling interaction with Astronomical Image Processing Software (AIPS) program. Moreover, a simple "out of box" Python script, which easy to set up free compilers. In addition flagging RFI affected visibilities, script also...
All 280 of the statistically-complete Palomar sample nearby (<120 Mpc) galaxies dec > 20 degrees have been observed at 1.5 GHz as part LeMMINGs e-MERLIN legacy survey. Here, we present Chandra X-ray observations nuclei 213 these galaxies, including a sub-set 113 in declination range 40 to 65 degrees. We all optical spectral types, 'active' (e.g., LINERs and Seyferts) 'inactive' like HII absorption line (ALG). The flux limit our survey is 1.65$\times$10$^{-14}$~erg s$^{-1}$ cm$^{-2}$...
This paper presents the results of 2009–2010 monitoring sessions starburst galaxy M82, obtained with Multi-Element Radio-Linked Interferometer Network (MERLIN) at 5 GHz and e-MERLIN 6 GHz. Combining several MERLIN epochs to form a map 33.0 μJy bm−1 noise level, 52 discrete sources, mostly supernova remnants H ii regions, are identified. These include three objects which were not detected in 2002 session: SN2008iz, transient source 43.78+59.3, new remnant shell. Flux density variations, long...
We present e-MERLIN 21 cm (L-band) observations of single luminous OB stars in the Cygnus OB2 association, from COBRaS Legacy programme. The radio potentially offer most straightforward, least model-dependent, determinations mass-loss rates, and can be used to help resolve current discrepancies rates via clumped structured hot star winds. report here that flux densities O3 O6 supergiant giant are less than ~ 70 microJy. These fluxes may translated `smooth' wind upper limits 4.4 - 4.8 x...
Abstract Mass-loss in massive stars plays a critical role their evolution, although the precise mechanism(s) responsible – radiatively driven winds, impulsive ejection and/or binary interaction remain uncertain. In this Letter, we present Atacama Large Millimetre/Submillimeter Array line and continuum observations of supergiant B[e] star Wd1-9, post-main-sequence object located within starburst cluster Westerlund 1 (Wd1). We find it to be one brightest stellar point sources sky at millimetre...
Abstract We present a large-scale study of diffuse X-ray emission in the nearby massive stellar association Cygnus OB2 as part Chandra Legacy Program. used 40 ACIS-I observations covering ∼1.0 deg 2 . After removing 7924 point sources detected our survey and applying adaptive smoothing to background-corrected emission, reveals emission. Diffuse was subbands soft (0.5−1.2 keV) medium (1.2−2.5 marginally hard (2.5−7.0 band. From spectral analysis stacked spectra we compute total (0.5–7.0...
The CLEAN algorithm, widely used in radio interferometry for the deconvolution of images, performs well only if raw image (dirty image) is, to good approximation, a simple convolution between instrumental point-spread function beam) and true distribution emission across sky. An important case which this approximation breaks down is during frequency synthesis observing bandwidth wide enough variations spectrum sky become significant. assumption also down, any situation but snapshot...
The SKA will be a transformational instrument in the study of our local Universe.In particular, by virtue its high sensitivity (both to point sources and diffuse low surface brightness emission), angular resolution frequency ranges covered, undertake very wide range astrophysical research field nearby galaxies.By surveying vast numbers galaxies all types with µJy sub-arcsecond resolutions at radio wavelengths, provide cornerstone understanding star-formation accretion activity this chapter...
We present high-resolution e-Multi-Element Radio Linked Interferometer Network radio continuum maps of the dwarf irregular galaxy IC 10 at 1.5 and 5 GHz. detect 11 compact sources GHz, five which have complementary detections classify three extended as H ii regions within 10, contaminating background galaxies identify that require additional observations to classify. do not expect any these are supernova remnants they will likely be resolved out assumed distance (0.7 Mpc). correct integrated...
ABSTRACT A key characteristic of many active galactic nuclei (AGNs) is their variability, but its origin poorly understood, especially in the radio domain. Williams et al. (2017) reported a ∼50 per cent increase peak flux density AGN Seyfert galaxy NGC 4151 at 1.5 GHz with e-MERLIN array. We present new high-resolution observations 5 and compare these to archival MERLIN investigate variability. Our allow us probe nuclear region factor three times higher resolution than previous study....
This white paper describes the science case for Very Long Baseline Interferometry (VLBI) and provides suggestions towards upgrade paths European VLBI Network (EVN). The EVN is a distributed long-baseline radio interferometric array, that operates at very forefront of astronomical research. Recent results, together with new possibilities outlined in this vision document, demonstrate EVN's potential to generate exciting results will transform our view cosmos. Together e-MERLIN, range baseline...
Using the Very Large Array, a series of high-velocity-resolution observations have been made M82 starburst at 1.6 GHz. These follow up on previous studies main line OH maser emission in central kiloparsec this region, but with far greater velocity resolution, showing significant structure some spots for first time. A total 13 masers were detected, including all one previously known sources. While these are still unresolved velocity, new results clearly show spectra from several regions....
We report new 5.5 GHz radio observations of the massive star cluster Westerlund 1, taken by Australia Telescope Compact Array, detecting nine ten yellow hypergiants (YHGs) and red supergiants (RSGs) within cluster. Eight sources are spatially resolved. The nebulae associated with YHGs Wd1-4a, -12a -265 demonstrate a cometary morphology - first time this phenomenon has been observed for such stars. This structure is also echoed in ejecta RSGs Wd1-20 -26; each case tails directed away from...
We present high-sensitivity 1.51 GHz e-MERLIN radio images of the nearby galaxy NGC 6217. resolve compact source at centre 6217 for first time, finding a twin-lobed structure with total linear size ~4 arcsec (~400pc). The does not have central core but there is an unresolved hot spot near outer edge southern lobe. Combining our data new VLA A-Array and archival multi-wavelength data, we explore possible scenarios which might explain this complex morphology. conclude that most likely powered...
Massive stars and their stellar winds are important for a number of feedback processes. The mass lost in the wind can help determine end-point star as NS or BH. However, impact mass-loss on post-Main Sequence evolutionary stage massive is not well understood. Westerlund 1 an ideal astrophysical laboratory which to study great detail over large range different phases. Aims: We aim radio emission from 1, order measure fluxes population stars, rates spectral indices where possible. Methods:...