A5036367458- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Molecular Spectroscopy and Structure
- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Scientific Research and Discoveries
- Advanced Frequency and Time Standards
- Atmospheric Ozone and Climate
- Ionosphere and magnetosphere dynamics
- Adaptive optics and wavefront sensing
- Mechanics and Biomechanics Studies
- Dark Matter and Cosmic Phenomena
- GNSS positioning and interference
- CCD and CMOS Imaging Sensors
- Advanced Chemical Physics Studies
- Neutrino Physics Research
- Spectroscopy and Laser Applications
National Radio Astronomy Observatory
2014-2024
New Mexico Institute of Mining and Technology
2019
Joint Institute for VLBI ERIC
2001-2002
Swedish Institute of Space Physics
2002
Netherlands Institute for Radio Astronomy
2001
University of Illinois Urbana-Champaign
2001
Leiden University
1998
Leiden Observatory
1996-1998
The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with unique combination of high angular resolution ($\approx$2.5"), sensitivity (a 1$\sigma$ goal 70 $\mu$Jy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2-4 GHz). first observations began September 2017, observing for will finish 2024. VLASS use approximately 5500 hours on Karl G. Jansky (VLA) to cover whole visible VLA (Declination $>-40^{\circ}$), total...
We present the first results of VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey 1127 sources with flat radio spectra. Through automated data reduction imaging routines, we have produced publicly available I, Q, U images detected polarized flux density from 37% sources. also developed an algorithm to use each source's I image automatically classify it as pointlike source, core jet, compact symmetric object (CSO) candidate, or complex source. Using Sloan Digital Sky (SDSS),...
We report on a successful, simultaneous observation and modeling of the sub-millimeter to near-infrared flare emission Sgr A* counterpart associated with super-massive black hole at Galactic center. Our is based observations that have been carried out 03 June, 2008 using NACO adaptive optics (AO) instrument ESO VLT LABOCA bolometer APEX telescope. Inspection light curves show sub-mm follows NIR delay 1.5+/-0.5 hours. explain by an adiabatic expansion source components.
Two independent, largely overlapping 1612 MHz data sets were searched for OH/IR stars in the Galactic center. One set, taken with Very Large Array period 1988 to 1991, consists of 17 epochs monitoring Van Langevelde et al. (1993). The other set was observed 1994, using Australia Telescope Compact Array. This article describes reduction procedures as well a different way searching image cubes narrow line sources, and lists total 155 double peak OH maser detections within 18 or 40 projected...
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....
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...
We examine the radio properties of EGRET-detected blazars observed as part VLBA Imaging and Polarimetry Survey (VIPS). VIPS has a flux limit roughly an order magnitude below MOJAVE survey most other samples that have been used to study EGRET blazars. At lower levels, density does not directly correlate with gamma-ray density. do find tend higher brightness temperatures, greater core fractions, possibly larger than average jet opening angles. A weak correlation is also found length...
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...
We present 86 GHz (v = 1, J 2 -1) SiO maser line observations with the IRAM 30-m telescope of a sample 441 late-type stars in Inner Galaxy (-4 degr < l +30 degr). These were selected on basis their infrared magnitudes and colours from ISOGAL MSX catalogues. emission was detected 271 sources, line-of-sight velocities indicate that are located Galaxy. new detections double number available previous OH area covered by our survey are, together other samples e.g. OH/IR stars, useful for...
We confirm our earlier tentative detection of M31* in X-rays and measure its light-curve spectrum. Observations 2004-2005 find rather quiescent the X-ray radio. However, observations 2006-2007 radio 2002 show to be highly variable at times. A separate source is found near P1, brighter two optical nuclei. The apparent angular Bondi radius largest any black hole, large enough well resolved with Chandra. diffuse emission within this have an temperature ~0.3 keV density 0.1 cm-3,...
The asymptotic giant branch (AGB) stars X Her and TX Psc have been imaged at 70 160 microns with the PACS instrument onboard Herschel satellite, as part of large MESS (Mass loss Evolved StarS) Guaranteed Time Key Program. images reveal an axisymmetric extended structure its axis oriented along space motion stars. This is very likely to be shaped by interaction wind ejected AGB star surrounding interstellar medium (ISM). As predicted numerical simulations, detailed wind-ISM interface depends...
We present Very Large Array (VLA) radio interferometry observations of the 1720 MHz OH masers in Galactic center (GC). Most arise regions where supernova remnant Sgr A East is interacting with interstellar medium. The majority newly found are located to northeast, independently indicating and confirming an area shock interaction +50 km s−1 molecular cloud (M–0.02–0.07) on far side East. previously known bright southeast suggested be result between two remnants, instead surrounding clouds, as...
<i>Context. <i/>We report on a successful, simultaneous observation and modelling of the millimeter (mm) to near-infrared (NIR) flare emission Sgr A* counterpart associated with supermassive (4 × 10<sup>6<sup/> ) black hole at Galactic centre (GC). We present mm/sub-mm light curve one highest quality continuous time coverages.<i>Aims. study model physical processes giving rise variable A*. <i>Methods. <i/>Our non-relativistic is based observations carried out in May 2007 2008, using NACO...
We have performed targeted surveys for 22 GHz H2O and 43 SiO maser emission in Galactic center OH/IR stars using the Very Large Array. Some of detections been used a previous paper to investigate possibility measuring milli-arcsecond accurate positions (to obtain stellar proper motions) center. Here we report on detection at least 25 masers 18 associated with within 2° 15´ Sgr A*, respectively. This survey has more than doubled total number motion candidates about 50 objects. The are best...
We present full polarization Very Long Baseline Array (VLBA) observations at 5 GHz and 15 of 24 compact active galactic nuclei (AGN). These sources were observed as part a pilot project to demonstrate the feasibility conducting large VLBI survey further our understanding physical properties temporal evolution AGN jets. The sample is drawn from Cosmic Lens All-Sky Survey (CLASS) where it overlaps with Sloan Digital Sky declinations north degrees. There are 2100 CLASS brighter than 50 mJy 8.4...
Recent studies of methanol and ground-state OH masers at very high spectral resolution have shed new light on small-scale maser processes. The nearby source W3(OH), which contains numerous bright in several different transitions, provides an excellent laboratory for techniques. We present a model W3(OH) based European VLBI Network (EVN) observations the rotationally excited 6030 6035 MHz taken 0.024 km s-1 resolution. 6.0 GHz are becoming brighter with time show evidence tangential proper...
We present MSX two-color diagrams that can be used to characterize circumstellar environments of sources with good quality colors in terms IRAS color regions for oxygen-rich stars. With these we aim provide a new tool study and improve detection rates targeted surveys maser emission similar the diagram. This is especially useful sky where was confused, particular Galactic plane bulge region. Unfortunately, using alone does not allow distinguish between carbon-rich objects. An application...
ABSTRACT We report on Green Bank Telescope 23.87 GHz NH 3 (3,3) emission observations in five supernova remnants (SNRs) interacting with molecular clouds (G1.4−0.1, IC 443, W44, W51C, and G5.7−0.0). The show a clumpy gas density distribution, most cases the narrow line widths of ∼3–4 km s −1 are suggestive maser emission. Very Large Array reveal 36 and/or 44 CH OH majority (72%) peak positions toward three these SNRs. This good positional correlation is agreement high densities required for...
The collisionally pumped, ground-state 1720 MHz maser line of OH is widely recognized as a tracer for shocked regions and observed in star-forming supernova remnants. Whereas some lines excited states have been detected studied regions, the subject excited-state remnants—where high collision rates are to be expected—is only recently being addressed. Modeling collisional excitation demonstrates that 1720, 4765, 6049 masers can occur under similar conditions gas. In particular, 4765 become...
We present radio continuum light curves of the magnetar SGR J1745$-$2900 and Sgr A* obtained with multi-frequency, multi-epoch Very Large Array observations between 2012 2014. During this period, a powerful X-ray outburst from occurred on 2013-04-24. Enhanced emission is delayed respect to peak by about seven months. In addition, flux density fluctuates factor 2 4 at frequencies 21 41 GHz its spectral index varies erratically. Here we argue that excess fluctuating arises interaction shock...