A5002721197- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Molecular Spectroscopy and Structure
- Solar and Space Plasma Dynamics
- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Atmospheric Ozone and Climate
- Cosmology and Gravitation Theories
- Spectroscopy and Laser Applications
- Ionosphere and magnetosphere dynamics
- Radio Astronomy Observations and Technology
- Scientific Research and Discoveries
- Phase Equilibria and Thermodynamics
- Geophysics and Gravity Measurements
- Space Exploration and Technology
- CCD and CMOS Imaging Sensors
- History and Developments in Astronomy
- Solar Radiation and Photovoltaics
University of Hong Kong
2015-2024
The University of Sydney
2024
Chinese University of Hong Kong
2023
National University Health System
2022-2023
National University of Singapore
2022-2023
Hong Kong University of Science and Technology
2021
Queen Mary Hospital
2015-2017
Institute of Astronomy and Astrophysics, Academia Sinica
2005-2016
Asia University
2008-2016
Leiden University
2016
We give an overview and describe the rationale, methods, first results from NIRCam images of JWST "Prime Extragalactic Areas for Reionization Lensing Science" ("PEARLS") project. PEARLS uses up to eight filters survey several prime extragalactic areas: two fields at North Ecliptic Pole (NEP); seven gravitationally lensing clusters; high redshift proto-clusters; iconic backlit VV 191 galaxy system map its dust attenuation. also includes NIRISS spectra one NEP NIRSpec high-redshift quasars....
The deflection angles of lensed sources increase with their distance behind a given lens. We utilize this geometric effect to corroborate the $z_{phot}\simeq9.8$ photometric redshift estimate faint near-IR dropout, triply-imaged by massive galaxy cluster Abell 2744 in deep Hubble Frontier Fields images. multiple images source follow same symmetry as other nearby sets which bracket critical curves and have well defined redshifts (up $z_{spec}\simeq3.6$), but larger angles, indicating that...
Abstract The first deep field images from the James Webb Space Telescope (JWST) of galaxy cluster SMACS J0723.3-7327 reveal a wealth new lensed at uncharted infrared wavelengths, with unprecedented depth and resolution. Here we securely identify 14 sets multiply imaged galaxies totaling 42 images, adding to five bright already known Hubble data. We find examples arcs crossing critical curves, allowing detailed community follow-up, such as JWST spectroscopy for precise redshift...
We present ultra-deep J and Ks imaging observations covering a 30' * area of the Extended Chandra Deep Field-South (ECDFS) carried out by our Taiwan ECDFS Near-Infrared Survey (TENIS). The median 5-sigma limiting magnitudes for all detected objects in reach 24.5 23.9 mag (AB) Ks, respectively. In inner 400 arcmin^2 region where sensitivity is more uniform, as faint 25.6 25.0 are at 5-sigma. So this far deepest datasets available ECDFS. To combine TENIS with Spitzer IRAC data obtaining better...
A short 30 minute ALMA observation of the early-type galaxy NGC 5044, which resides at center an X-ray bright group with a moderate cooling flow, has detected 24 molecular structures within central 2.5 kpc. The masses vary from 3e5 to 1e7 Mo3 and CO(2-1) linewidths 15 65 km/s. Given large linewidths, observed are likely giant associations (GMAs) not individual clouds (GMCs). Only few GMAs spatially resolved cycle 0 beam average density these yields GMC volume filling factor about 15%....
We present SubMillimeter-Array observations of a Keplerian disk around the Class I protobinary system L1551 NE in 335 GHz continuum emission and submillimeter line 13CO (J=3-2) C18O at resolution ~120 x 80 AU. The 335-GHz dust-continuum image shows strong central peak closely coincident with binary protostars likely corresponding to circumstellar disks, surrounded by ~600 300 AU feature elongated approximately perpendicular [Fe II] jet from southern protostellar component suggestive...
We present ALMA Band 6 observations of the CO(2-1), HCN(3-2), and HCO$^{+}$(3-2) lines in nearby radio galaxy / brightest cluster (BCG) NGC 1275 with spatial resolution $\sim20$ pc. In previous observations, CO(2-1) emission was detected as radial filaments lying east-west direction. resolved inner filament found that cannot be represented by a simple infalling stream both morphologically kinematically. The observed complex nature resembles cold gas structure predicted recent numerical...
We have constructed a detailed mean density and temperature model for the extended outer atmosphere of O-rich supergiant Betelgeuse (α Ori [M2 Iab]), which extends from 1.0 to 10.0 stellar radii. A one-dimensional is based on fitting NRAO VLA centimeter visibility data, two-dimensional models are using intensity contours 0.7 cm observations Lim et al. As one moves in toward star about 10 R* electron increases value ≃3800 K, then declines down below Teff, rises photospheric values. The peak...
We have imaged in CO(2-1) the molecular gas NGC 1275 (Perseus A), cD galaxy at center of Perseus Cluster, a spatial resolution ~1 kpc over central region radius ~10 kpc. Per A is known to contain ~1.3 × 1010 M☉ gas, which has been proposed be captured from mergers with or ram pressure stripping gas-rich galaxies, accreted X-ray cooling flow. The detected our image total mass ~4 109 M☉, and for first time can seen concentrated three radial filaments lengths ranging least 1.1 2.4 kpc, all...
Powerful radio-AGN are hosted by massive elliptical galaxies which usually very poor in molecular gas. Nevertheless gas is needed the center to feed nuclear activity. We aim study properties (mass, kinematics, distribution, origin) such objects, and compare them with results of other known samples. have performed at IRAM-30m telescope a survey CO(1-0) CO(2-1) emission most powerful radio Local Universe, selected only on basis their continuum fluxes. The main result our low content compared...
The massive cluster MACSJ1149.5+2223(z = 0.544) displays five very large lensed images of a well-resolved spiral galaxy at zspect 1.491. It is within one these that the first example multiply supernova (SN) has been detected recently as part Grism Lens-Amplified Survey from Space. depth this data also reveals many H ii regions which we identify between counter-images. Here, expand capability our free-form method to incorporate locally, with other reliable galaxies added for global solution....
The axes of solar active regions are inclined relative to the east--west direction, with tilt angle tending increase latitude ("Joy's law"). Observational determinations Joy's law have been based either on white-light images sunspot groups or magnetograms, where latter advantage measuring directly physically relevant quantity (the photospheric field), but disadvantage having recorded routinely only since mid-1960s. White-light studies employing historical Mount Wilson (MW) database yielded...
We present a free form mass reconstruction of the massive lensing cluster MACSJ0416.1-2403 using latest Hubble Frontier Fields data. Our model independent method finds that extended pattern is generated by two elongated, closely projected clusters similar mass. lens identifies new lensed images with which we improve accuracy dark matter distribution. find bimodal distribution nearly coincident X-ray emission, but peaks lying closer together than centroids emisison. show this can be achieved...
ABSTRACT We present the first JWST observations of z = 4.11 luminous radio galaxy TN J1338–1942, obtained as part ‘Prime Extragalactic Areas for Reionization and Lensing Science’ (‘PEARLS’) project. Our NIRCam observations, designed to probe key rest-frame optical continuum emission line features at this redshift, enable resolved spectral energy distribution modelling that incorporates both a range stellar population assumptions radiative shock models. With an estimated mass log10(M/M⊙) ∼...
Abstract We present new high-spectral-resolution observations ( R = λ /Δ 7000) of the filamentary nebula surrounding NGC 1275, central galaxy Perseus cluster. These have been obtained with SITELLE, an imaging Fourier transform spectrometer installed on Canada–France–Hawai Telescope a field view <?CDATA $11^{\prime} \times 11^{\prime} $?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>11</mml:mn> <mml:mo accent="false">′</mml:mo> <mml:mo>×</mml:mo>...
Recent observations of caustic-crossing galaxies at redshift 0.7 ≲ z 1 show a wealth transient events. Most them are believed to be microlensing events highly magnified stars. Earlier work predicts such should common near the critical curves (CCs) galaxy clusters (“near region”), but some found relatively far away from these CCs (“far region”). We consider possibility that substructure on milliarcsecond scales (few parsecs in lens plane) is boosting signal region. study combined...
view Abstract Citations (75) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Millimeter, Microwave, Hard X-Ray, and Soft X-Ray Observations of Energetic Electron Populations in Solar Flares Kundu, M. R. ; White, S. Gopalswamy, N. Lim, J. We present comparisons multiwavelength data for a number solar flares observed during the major campaign 1991 June. The different wavelengths are diagnostics energetic electrons energy ranges: soft X-rays...
Studying the earliest stages in birth of stars is crucial for understanding how they form. Brown dwarfs with masses between that and planets are not massive enough to maintain stable hydrogen-burning fusion reactions during most their lifetime. Their origins subject much debate recent literature because far below typical mass where core collapse expected occur. We present first confirmed evidence brown undergo a phase molecular outflow young stars. Using Submillimeter Array, we have obtained...
Hubble Frontier Fields (HFF) imaging of the most powerful lensing clusters provides access to magnified distant galaxies. The challenge is construct lens models capable describing these complex massive, merging so that individual lensed systems can be reliably identified and their intrinsic properties accurately derived. We apply free-form method (WSLAP+) A2744, providing a model independent map cluster mass, magnification, geometric distance estimates multiply-lensed sources. solve...
We derive a free-form mass distribution for the massive cluster AS1063 (z=0.348) using completed optical imaging from Hubble Frontier Fields programme. Based on subset of 11 multiply lensed systems with spectroscopic redshift we produce lens model that is accurate enough to unveil new systems, totalling over 100 arclets, and estimate their redshifts geometrically. Consistency found between this precise obtained only sources spectroscopically measured redshifts. Although relatively large...
We show that the mass-loss rates of active late-type dwarf stars must be significantly lower than recent estimates up to ~5 × 10-10 M☉ yr-1, 4 orders magnitude higher Sun. First, we present aperture-synthesis observations at 3.5 mm dMe flare YZ CMi and AD Leo, during which neither star was detected an upper limit 10 mJy. Although compatible with tentative detection 1.1 reported by Mullan coworkers if millimeter emission originates from a ~104 K, 300 km s-1 wind ≈ 5 such would completely...
We report narrowband imaging of the 1–0 S(1) ro-vibrational transition molecular hydrogen (H2) from NGC 1275, central cD galaxy Perseus Cluster. find that H2 gas has a spatial morphology identical to optical emission-line nebula associated with this galaxy, total luminosity in only an order magnitude less than Hα, and if line-emitting is thermalized mass (at ∼2000 K) over two orders smaller ∼10,000 K). The ratio Hα+[N ii] line intensities spans characteristic range ∼0.02–0.08 throughout...