A5048726244- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Molecular Spectroscopy and Structure
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Spectroscopy and Laser Applications
- Geophysics and Gravity Measurements
- Superconducting and THz Device Technology
- Solar and Space Plasma Dynamics
- Scientific Research and Discoveries
- Particle Accelerators and Free-Electron Lasers
- History and Developments in Astronomy
- Ionosphere and magnetosphere dynamics
- Atomic and Subatomic Physics Research
- Adaptive optics and wavefront sensing
- Particle Detector Development and Performance
- Phase Equilibria and Thermodynamics
National Radio Astronomy Observatory
2015-2024
University of Virginia
2009-2023
South African Radio Astronomy Observatory
2019
North-West University
2019
University of Nigeria
2019
National Astronomical Observatory of Japan
2019
Hartebeesthoek Radio Astronomy Observatory
2019
University of Hawaii System
2006
Institute of Astronomy
2006
University of Hawaii at Hilo
2004-2005
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission HL Tau region. The images at wavelengths of 2.9, 1.3, 0.87 mm have unprecedented angular resolutions 0 075 (10 AU) to 025 (3.5 AU), revealing an astonishing level detail circumstellar disk surrounding young solar analog Tau, with a pattern bright dark rings observed all wavelengths. By fitting ellipses most distinct rings, we measure...
ABSTRACT Using images from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE), we have identified more than 300 extended 4.5 μm sources (Extended Green Objects (EGOs), for common coding of [4.5] band as green in three-color composite InfraRed Array Camera images). We present a catalog these EGOs, including integrated flux density measurements at 3.6, 4.5, 5.8, 8.0, and 24 GLIMPSE Multiband Imaging Photometer Plane Survey. The average angular separation between...
Using Infrared Array Camera (IRAC) images at 3.6, 4.5, 5.8, and 8 μm from the GLIMPSE Legacy science program on Spitzer Space Telescope, we searched for infrared counterparts to 95 known supernova remnants that are located within Galactic longitudes 65° > |l| 10° latitudes |b| < 1°. Eighteen were detected. Many other could have significant emission but in portions of Milky Way too confused allow separation bright H II regions pervasive mid-infrared atomic molecular clouds along line sight....
We present the results of a high angular resolution Very Large Array (VLA) Class I 44 GHz and II 6.7 CH3OH maser survey sample ∼20 massive young stellar object (MYSO) outflow candidates selected on basis extended 4.5 μm emission in Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire images. These are referred to as green objects (EGOs), for common coding this band three-color Camera The detection rate masers, which associated exclusively with YSOs, toward EGOs is ≳64%—nearly...
We report the discovery of up to 35 new supernova remnants (SNRs) from a 42 arcsec resolution 90cm multi-configuration Very Large Array survey Galactic plane covering 4.5 deg< l <22.0 deg and |b| < 1.25 deg. Archival 20cm, 11cm, 8 micron data have also been used identify SNRs constrain their properties. The image is sensitive with diameters 2.5 arcmin 50 down surface brightness limit about 10^{-21} W m^{-2} Hz^{-1} sr^{-1}. This has nearly tripled number known in this part Galaxy,...
Abstract Based on sub-arcsecond Atacama Large Millimeter/submillimeter Array (ALMA) and Submillimeter (SMA) 1.3 mm continuum images of the massive protocluster NGC 6334I obtained in 2015 2008, we find that dust emission from MM1 has increased by a factor 4.0 ± 0.3 during intervening years, undergone significant change morphology. The other cluster members (MM2, MM4, UCH ii region MM3 = 6334F) remained constant. Long-term single-dish maser monitoring at HartRAO finds multiple species toward...
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions tens milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up ~15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from September late November 2014, culminating in end-to-end observations, calibrations, imaging selected Science Verification (SV) targets. This paper presents an overview campaign its main results,...
We present initial results of very high resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations the z = 3.042 gravitationally lensed submillimeter galaxy HATLAS J090311.6+003906 (SDP.81). These were carried out using a extended configuration as part Science Verification for 2014 ALMA Long Baseline Campaign, with baselines up to ∼15 km. continuum imaging at 151, 236, and 290 GHz unprecedented angular resolutions fine 23 mas, corresponding an unmagnified spatial scale ∼180...
The formation process of massive stars is not well understood, and advancement in our understanding benefits from high resolution observations modelling the gas dust surrounding individual high-mass (proto)stars. Here we report sub-arcsecond (<1550 au) young star G11.92-0.61 MM1 with SMA VLA. Our 1.3 mm reveal consistent velocity gradients compact molecular line emission species such as CH$_3$CN, CH$_3$OH, OCS, HNCO, H$_2$CO, DCN CH$_3$CH$_2$CN, oriented perpendicular to previously reported...
Abstract We report ALMA observations with resolution ≈0.″5 at 3 mm of the extended Sgr B2 cloud in Central Molecular Zone (CMZ). detect 271 compact sources, most which are smaller than 5000 au. By ruling out alternative possibilities, we conclude that these sources consist a mix hypercompact H ii regions and young stellar objects (YSOs). Most newly detected YSOs gas envelopes that, based on their luminosities, must contain masses <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Abstract We describe the calibration and imaging heuristics developed deployed in Atacama Large Millimeter/submillimeter Array (ALMA) interferometric data processing pipeline, as of ALMA Cycle 9 operations. The pipeline software framework is written Python, with each reduction stage layered on top tasks toolkit functions provided by Common Astronomy Software Applications package. This supports a variety for observatory operations, including science quality assurance, observing mode...
We present observations of IRAS 16293-2422 using the Submillimeter Array (SMA) at 300 GHz, and Very Large (VLA) frequencies from 1.5 to 43 GHz. This source was already known be a binary system with components A B separated by ~5". The new SMA data now separate into two submm continuum components, denoted Aa Ab. strongest these, Aa, peaks between cm radio sources A1 A2. Archival VLA show proper motion 17 mas/yr, associated rho Ophiuchi cloud. also find relative A2 which excludes possibility...
M17 is one of the youngest and most massive nearby star-formation regions in Galaxy. It features a bright H II region erupting as blister from side giant molecular cloud (GMC). Combining photometry Spitzer GLIMPSE survey with complementary infrared (IR) surveys, we identify candidate young stellar objects (YSOs) throughout 1.5 deg x 1 field that includes complex. The long sightline through Galaxy behind creates significant contamination our YSO sample unassociated sources similar IR colors....
The southwestern (SW) part of the Galactic H II region M17 contains an obscured ionization front that is most easily seen at infrared and radio wavelengths. It nearly edge-on, thus offering excellent opportunity to study way in which gas changes from fully ionized molecular as radiation ionizing stars penetrates into gas. also one very few regions for magnetic field strength can be measured photodissociation ( PDR) forms interface between Here we model observed line sight through cloud,...
Abstract We report the detection of interstellar methoxymethanol (CH 3 OCH 2 OH) in Atacama Large Millimeter/submillimeter Array (ALMA) Bands 6 and 7 toward MM1 core high-mass star-forming region NGC 6334I at ∼0.″1–1″ spatial resolution. A column density 4(2) × 10 18 cm −2 T ex = 200 K is derived MM1, ∼34 times less abundant than methanol OH), significantly higher predicted by astrochemical models. Probable formation destruction pathways are discussed, primarily through reaction CH OH...
We present an analysis of the physical conditions in extreme molecular cloud Antennae merging galaxies. This has properties consistant with those required to form a globular cluster. have obtained ALMA CO and 870 μm observations galaxy system ∼05 resolution. stands out data radius ≲24 pc mass >5 × 106 M⊙. The appears capable forming cluster, but lack associated thermal radio emission indicates that star formation not yet altered environment. places early stage evolution, which we expect be...
We report the first sub-arcsecond VLA imaging of 6 GHz continuum, methanol maser, and excited-state hydroxyl maser emission toward massive protostellar cluster NGC6334I following recent 2015 outburst in (sub)millimeter continuum MM1, strongest source protocluster. In addition to detections previously known 6.7 Class II sites hot core MM2 UCHII region MM3 (NGC6334F), we find new features several components along with weaker $\sim1''$ north, west, southwest non-thermal radio CM2. None these...
Producing images from interferometer data requires accurate modeling of the sources in field view, which is typically done using CLEAN algorithm. Given large number degrees freedom interferometeric images, one constrains possible model solutions for by masking regions that contain emission. Traditionally this process has largely been hand. This approach not with today's volumes require automated imaging pipelines. paper describes an algorithm operates within called AUTO-MULTITHRESH. was...
Class II methanol masers are signs of massive young stellar objects (MYSOs). Recent findings show that MYSO accretion bursts cause flares these masers. Thus, maser monitoring can be used to identify such bursts. Burst-induced SED changes provide valuable information on a very intense phase high-mass star formation. In mid-January 2019, flare the G358.93-0.03 was reported. ALMA and SMA imaging resolved core forming region proved association with brightest continuum source MM1. However, no...
New low-frequency 74 and 330 MHz observations of the Galactic center (GC) region reveal presence a large-scale ($6\arcdeg\times 2\arcdeg$) diffuse source nonthermal synchrotron emission. A minimum energy analysis this emission yields total $\sim (\phi^{4/7}f^{3/7})\times 10^{52}$ ergs magnetic field strength 6(\phi/f)^{2/7}$ \muG (where $\phi$ is proton to electron ratio $f$ filling factor emitting gas). The equipartition particle density $1.2(\phi/f)^{2/7}$ \evcm, value consistent with...
Using the Submillimeter Array (SMA), we have imaged 1.3 mm continuum emission at centers of massive star-forming regions NGC 6334 I and I(N). In both regions, SMA observations resolve into multiple millimeter sources, with most sources clustered areas only 10,000 AU in diameter. Toward I, find four compact sources: two brightest (I-SMA1 I-SMA2) are associated previously known ammonia cores; I-SMA3 coincides peak H II region (NGC F), I-SMA4 is a newly discovered object. While exhibits mixture...
We aim at deriving the molecular abundances and temperatures of hot cores in high-mass star-forming region NGC 6334I consequently their physical astrochemical conditions. In framework Herschel guaranteed time key program CHESS, is investigated by using HIFI aboard Space Observatory. A spectral line survey carried out frequency range 480-1907 GHz, auxiliary interferometric data from SMA 230 GHz band provide spatial information for disentangling different components contributing to spectrum....