A5079112859- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Antenna Design and Optimization
- Molecular Spectroscopy and Structure
- Solar and Space Plasma Dynamics
- Pulsars and Gravitational Waves Research
- Superconducting and THz Device Technology
- Spectroscopy and Laser Applications
- Antenna Design and Analysis
- Scientific Research and Discoveries
- Geophysics and Gravity Measurements
- GNSS positioning and interference
- History and Developments in Astronomy
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Advanced MIMO Systems Optimization
- Radio Wave Propagation Studies
University of New Mexico
2014-2024
National Radio Astronomy Observatory
2004-2018
Leiden Observatory
2011
Nicolaus Copernicus University
2011
Joint Institute for VLBI ERIC
2011
Science and Technology Facilities Council
2011
U.S. National Science Foundation
2011
National Research Council Canada
2011
United States Naval Research Laboratory
2010
United States Navy
2010
The Long Wavelength Array (LWA) will be a new multipurpose radio telescope operating in the frequency range 10-88 MHz. Upon completion, LWA consist of 53 phased array ldquostationsrdquo distributed over region about 400 km diameter state New Mexico. Each station 256 pairs dipole-type antennas whose signals are formed into beams, with outputs transported to central location for high-resolution aperture synthesis imaging. resulting image sensitivity is estimated few millijanskys (5 sigma, 8...
The first station of the Long Wavelength Array (LWA1) was completed in April 2011 and is currently performing observations resulting from its call for proposals addition to a continuing program commissioning characterization observations. instrument consists 258 dual-polarization dipoles, which are digitized combined into beams. Four independently-steerable beams available, each with two tunings 16 MHz bandwidth that can be independently tuned any frequency between 10 88 MHz. system...
We present new data obtained with the Submillimeter Array for a sample of fourteen nearby luminous and ultraluminous infrared galaxies.The galaxies were selected to have distances D L < 200 Mpc far-infrared luminosities log FIR > 11.4.The observed spatial resolutions order
Aims. To study at multiple frequencies the radio emission arising from massive galaxy cluster MACS J0717.5+3745 (z=0.55). Known to be an extremely complex merger, system is uniquely suited for investigation of phenomena work in intra-cluster medium (ICM) during collisions. Methods. We use multi-frequency and multi-resolution data obtained with Very Large Array telescope, X-ray features revealed by Chandra, probe non-thermal thermal components ICM, their relations interactions. Results. The...
We present a detailed comparison of the CO(3-2) emitting molecular gas between local sample luminous infrared galaxies (U/LIRGs) and high redshift that comprises submm selected (SMGs), quasars, Lyman Break Galaxies (LBGs). The U/LIRG consists our recent survey using Submillimeter Array while data for population are obtained from literature. find L(CO(3-2)) L(FIR) relation is correlated over five orders magnitude, which suggests traced in emission robust tracer dusty star formation activity....
We present an overview of the occurrence and properties atomic gas associated with compact radio sources at redshifts up to . Searches for H i 21 cm absorption were made Westerbork Synthesis Radio Telescope UHF-high frequencies (725–1200 MHz). Detections obtained 19 57 usable spectra (33%). have found a large range in line depths, from There is substantial variety profiles, including Gaussians less than 10 km s-1, more typically 150 as well irregular multi-peaked sometimes spanning several...
<i>Context. <i/>The 6.7 GHz methanol maser marks an early stage of high-mass star formation, but the origin this is currently a matter debate. In particular it unclear whether emission arises in discs, outflows or behind shocks running into rotating molecular clouds.<i>Aims. <i/>We investigated which structures masers trace environment protostar candidates by observing homogenous sample selected from Torun surveys. We also probed their origins looking for associated H II regions and IR...
We consider the incidence of Hiabsorption in intrinsically small sub-galactic sized extragalactic sources selected from classified as Gigahertz Peaked Spectrum (GPS) and Compact Steep (CSS) sources. find that smaller (<0.5 kpc) have larger Hicolumn densities than (>0.5 kpc). Both a spherical an axi-symmetric gas distribution, with radial power law density profile, can be used to explain this anti-correlation between projected linear size Hi column density. Since most detections occur objects...
We present ~2'' resolution CO(3-2), HCO+(4-3) and 880micron continuum images of the luminous infrared galaxy NGC6240 obtained at Submillimeter Array. find that spatially resolved emission peaks between two nuclear components are both known to harbor AGNs. Our Large Velocity Gradient (LVG) analysis performed on each velocity channel suggests peak molecular gas traced in our observations is warm (T = 20 - 100K), dense (nH2 10^(5.0 5.4) cm^-3) moderately optically thin (tau 0.2 2) central 1...
We have recently discovered a supermassive binary black hole system with projected separation between the two holes of 7.3 parsecs in radio galaxy 0402+379. This is most compact pair yet imaged by more than orders magnitude. present Global VLBI observations at 1.3464 GHz this galaxy, taken to improve quality HI data. Two absorption lines are found toward southern jet source, one redshifted 370 +/- 10 km/s and other blueshifted 700 respect systemic velocity which, along results obtained for...
We are currently undertaking a large survey for redshifted atomic and molecular absorption lines at radio frequencies. In this paper, we present the results from first phase of survey: search H i 21-cm OH 18-cm in hosts reddened quasars galaxies. Although observed each source up to several hours with two world's most sensitive telescopes, Giant Metrewave Radio Telescope (GMRT) Westerbork Synthesis (WSRT), only one clear tentative detection were obtained: z= 0.097 PKS 1555−140 0.126 2300−189,...
In radio interferometry, information about a small region of the sky is obtained in form samples Fourier transform domain desired image. Since this sampling usually incomplete, missing has to be reconstructed using additional assumptions The emerging field compressed sensing provides promising new approach type problem that based on supposed sparsity natural images some domain. We present versatile CS-based image reconstruction framework called SparseRI, an interesting alternative CLEAN...
We have used the Karl G. Jansky Very Large Array to search for 36 GHz and 44 methanol (CH3OH) lines in a sample of 21 Galactic supernova remnants (SNRs). Mainly regions SNRs with 1720 MHz OH masers were observed. Despite limited spatial extent covered our search, detected both G1.4−0.1 W28. Additional found Sgr A East. More than 40 G1.4−0.1, which we deduce are due interactions between SNR at least two separate molecular clouds. The six W28 associated cloud that is also maser excitation....
Gamma-ray bursts (GRBs) are the ultimate cosmic lighthouses, capable of illuminating universe at its earliest epochs. Could such events probe properties first stars z $\sim$ 20, end Dark Ages? Previous studies Population III GRBs only considered explosions in diffuse relic H II regions their progenitors, or that far more energetic than those observed to date. But processes produce highest redshifts likely reset local environments, creating much complicated structures which relativistic jets...
EVN and MERLIN observations of the 18 cm continuum OH maser emission in luminous infrared galaxy III Zw 35 are presented. The consists two components. first component is made up a number compact sources, resembling types objects observed Arp 220 Mrk 273. In origin these components unclear, we discuss possibility they individual young radio supernovae. Alternatively could be clusters or clumps supernova remnants. second diffuse has an angular size ~ (230 pc) . We argue that this also powered...
We present Very Long Baseline Interferometry (VLBI) observations 217 days after the gamma-ray burst of 2003 March 29. These provide further measurements size and position GRB 030329 that are used to constrain expansion rate proper motion this nearby GRB. The appears be slowing down with time, favoring into a constant density interstellar medium, rather than circumstellar wind an r^-2 profile. also late time Arecibo redshifted HI OH absorption spectra towards 030329. No (or emission) is seen...
We investigate the practice of assigning high spin temperatures to damped Lyman-alpha absorption systems (DLAs) not detected in HI 21-cm absorption. In particular, Kanekar & Chengaulr (2003) have attributed mix detections and non-detections low redshift (z<2.04) DLAs a temperatures, while at were temperatures. Below z=0.9, where some DLA host galaxy morphologies are known, we find that is normally towards large radio sources when absorber known be associated with intermediate (spiral)...
We present high-sensitivity Very Long Baseline Interferometry (VLBI) observations 806 days after the γ-ray burst of 2003 March 29 (GRB 030329). The angular diameter radio afterglow is measured to be 0.347 ± 0.09 mas, corresponding 0.99 0.26 pc at redshift GRB 030329 (z = 0.1685). evolution image size favors a uniform external density over an R-2 windlike profile (at distances R ≳ 1018 cm from source), although latter cannot ruled out yet. current apparent expansion velocity only mildly...
Class I methanol masers are believed to be produced in the shock-excited environment around star-forming regions.Many authors have argued that appearance of various subsets class may indicative specific evolutionary stages star formation or excitation conditions.Until recently, however, no major interferometer was capable imaging important 36 GHz transition.We report on Expanded Very Large Array observations and Submillimeter 229 DR21(OH), DR21N, DR21W.The distribution outflow DR21(OH) is...
We report on the interferometric detection of 36.2 GHz Class I methanol emission with new 27–40 Ka-band receivers available Expanded Very Large Array (EVLA). The brightness temperatures 36 detections unambiguously indicate for first time that is maser emission. masers are not co-spatial 1720 MHz OH masers, indicating two species trace different shocks. and 44 which collisionally pumped, do necessarily co-exist may gas. seem correlated NH3(3,3) density peaks. favor an explanation in outline...
We present the first detection of a 6.7 GHz Class II methanol (CH3OH) maser in Andromeda galaxy (M31). The CH3OH was found VLA survey during fall 2009. have confirmed with new EVLA, operation since 2010 March, but were unsuccessful detecting water at this location. A direct application for is determination proper motion M31, such as previously obtained masers M33 and IC10. Unraveling three-dimensional velocity M31 would solve biggest unknown modeling dynamics evolution Local Group galaxies.
We report on the detection of 44 GHz Class I methanol (CH3OH) maser emission in SgrA complex with Expanded Very Large Array (EVLA). These EVLA observations show that harbors at least four different tracers shocked regions radio regime. The masers correlate positions and velocities previously detected 36 CH3OH masers, but less 1720 MHz OH masers. Our detections agree theoretical predictions densities temperatures conducive for may also produce emission. However, many do not overlap suggesting...
The radio source 4C12.50 has often been suggested to be a prime candidate for the link between ultraluminous infrared galaxies and young galaxies. A VLBI study of neutral hydrogen in nuclear regions this object shows that most gas detected close systemic velocity is associated with an off-nuclear cloud (~50 100 pc from core) column density ~10^22 T_spin/100 K) cm^(-2) HI mass few times 10^5 10^6 M_sun. We consider number possibilities explain results. In particular, we discus possibility...
We present high resolution images of the 12CO(2-1) emission in central 1' (1 kpc) NGC 5128 (Centaurus A), observed using SMA. elucidate for first time distribution and kinematics molecular gas this region with a 6'.0 x 2'.4 (100 pc 40 pc). spatially resolve circumnuclear inner 24'' 12'' (400 200 pc), which is elongated along position angle P.A. = 155 deg perpendicular to radio/X-ray jet. The SE NW components are connected found at larger radii. This appears as two parallel filaments 120 deg,...
We present results from calculations of the physical conditions necessary for occurrence 36.169 ($4_{-1}-3_{0}\, E$), 44.070 ($7_{0}-6_{1}\,A^+$), 84.521 ($5_{-1}-4_{0}\,E$), and 95.169 ($8_{0}-7_{1}\,A^+$) GHz methanol (CH$_3$OH) maser emission lines near supernova remnants (SNRs), using MOLPOP-CEP program. The show that given a sufficient abundance, arises over wide range densities temperatures, with optimal at $n\sim 10^4-10^6$ cm$^{-3}$ $T>60$ K. 36~GHz 44~GHz transitions display more...