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I Heywood - One of the best experts on this subject based on the ideXlab platform.
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the stripe 82 1 2 ghz Very Large Array snapshot survey host galaxy properties and accretion rates of radio galaxies
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: I H Whittam, I Heywood, M Prescott, M Jarvis, K McalpineAbstract:A sample of 1161 radio galaxies with 0.01
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the stripe 82 1 2 ghz Very Large Array snapshot survey multiwavelength counterparts
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: M Prescott, I Heywood, I H Whittam, M Jarvis, K Mcalpine, L L Richter, S Fine, T Mauch, M VaccariAbstract:Published by Oxford University Press on behalf of the Royal Astronomical Society. We have combined spectroscopic and photometric data from the Sloan Digital Sky Survey with 1.4 GHz radio observations, conducted as part of the Stripe 82 1-2 GHz Snapshot Survey using the Karl G. Jansky Very Large Array, which covers ~100 sq deg, to a flux limit of 88 μJy rms. Cross-matching the 11 768 radio source components with optical data via visual inspection results in a final sample of 4794 cross-matched objects, of which 1996 have spectroscopic redshifts and 2798 objects have photometric redshifts. Three previously undiscovered giant radio galaxies were found during the cross-matching process, which would have been missed using automated techniques. For the objects with spectroscopy, we separate radio-loud active galactic nuclei (AGN) and star-forming galaxies (SFGs) using three diagnostics and then further divide our radio-loud AGN into the high and low excitation radio galaxy (HERG and LERG) populations. A control-matched sample of HERGs and LERGs, matched on stellar mass, redshift, and radio luminosity, reveals that the host galaxies of LERGs are redder and more concentrated than HERGs. By combining with near-infrared data, we demonstrate that LERGs also follow a tight K - z relationship. These results imply the LERG populations are hosted by population ofmassive, passively evolving early-type galaxies. We go on to show that HERGs, LERGs, quasars, and SFGs in our sample all reside in different regions of aWide-field Infrared Survey Explorer colour-colour diagram. This cross-matched sample bridges the gap between previous 'wide but shallow' and 'deep but narrow' samples and will be useful for a number of future investigations.
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a deep wide 1 2 ghz snapshot survey of sdss stripe 82 using the karl g jansky Very Large Array in a compact hybrid configuration
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: I Heywood, M J Jarvis, Andrew J Baker, K W Bannister, C S Carvalho, M J Hardcastle, Matt Hilton, Kavilan MoodleyAbstract:We have used the Karl G. Jansky Very Large Array to image ~100 sq. deg. of SDSS Stripe 82 at 1-2 GHz. The survey consists of 1,026 snapshot observations of 2.5 minutes duration, using the hybrid CnB configuration. The survey has good sensitivity to diffuse, low surface brightness structures and extended radio emission, making it highly synergistic with existing 1.4 GHz radio observations of the region. The principal data products are continuum images, with 16 x 10 arcsecond resolution, and a catalogue containing 11,782 point and Gaussian components resulting from fits to the thresholded Stokes-I brightness distribution, forming approximately 8,948 unique radio sources. The typical effective 1{\sigma} noise level is 88 {\mu}Jy / beam. Spectral index estimates are included, as derived from the 1 GHz of instantaneous bandwidth. Astrometric and photometric accuracy are in excellent agreement with existing narrowband observations. A Large-scale simulation is used to investigate clean bias, which we extend into the spectral domain. Clean bias remains an issue for snapshot surveys with the VLA, affecting our total intensity measurements at the ~1{\sigma} level. Statistical spectral index measurements are in good agreement with existing measurements derived from matching separate surveys at two frequencies. At flux densities below ~35{\sigma} the median in-band spectral index measurements begin to exhibit a bias towards flatness that is dependent on both flux density and the intrinsic spectral index. In-band spectral curvature measurements are likely to be unreliable for all but the Very brightest components. Image products and catalogues are publicly available via an FTP server.
Remy Indebetouw - One of the best experts on this subject based on the ideXlab platform.
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Very Large Array ammonia observations of the hh 111 hh 121 protostellar system a detection of a new source with a peculiar chemistry
The Astrophysical Journal, 2017Co-Authors: Marta Sewilo, Jaime E Pineda, Remy Indebetouw, Jennifer Wiseman, S B Charnley, Johan E Lindberg, Shengli QinAbstract:We present the results of Very Large Array NH3 (J, K) = (1, 1) and (2, 2) observations of the HH 111/HH 121 protostellar system. HH 111, with a spectacular collimated optical jet, is one of the most well-known Herbig-Haro objects. We report the detection of a new source, NH3-S, in the vicinity of HH 111/HH 121 (approximately 0.03 parsecs from the HH 111 jet source) in two epochs of the ammonia observations. This constitutes the first detection of this source, in a region that has been thoroughly covered previously by both continuum and spectral line interferometric observations. We study the kinematic and physical properties of HH 111 and the newly discovered NH3-S. We also use HCO plus and HCN (J=4-3) data obtained with the James Clerk Maxwell Telescope and archival Atacama Large Millimeter/submillimeter Array (sup 13) CO, (sup 12) CO, and C (sup 18) O (J=2-1), N2D plus (J=3-2), and (sup 13) CS (J=5-4) data to gain insight into the nature of NH3-S. The chemical structure of NH3-S shows evidence for "selective freeze-out," an inherent characteristic of dense cold cores. The inner part of NH3-S shows subsonic nonthermal velocity dispersions indicating a "coherent core," while they increase in the direction of the jets. Archival near- to far-infrared data show no indication of any embedded source in NH3-S. The properties of NH3-S and its location in the infrared dark cloud suggest that it is a starless core located in a turbulent medium, with the turbulence induced by Herbig-Haro jets and associated outflows. More data are needed to fully understand the physical and chemical properties of NH3-S and if/how its evolution is affected by nearby jets.
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Very Large Array ammonia observations of the hh 111 hh 121 protostellar system a detection of a new source with a peculiar chemistry
arXiv: Astrophysics of Galaxies, 2017Co-Authors: Marta Sewilo, Jaime E Pineda, Remy Indebetouw, Jennifer Wiseman, S B Charnley, Johan E Lindberg, Shengli QinAbstract:We present the results of Very Large Array NH$_{3}$ $(J,K)=(1,1)$ and $(2,2)$ observations of the HH 111/HH 121 protostellar system. HH 111, with a spectacular collimated optical jet, is one of the most well-known Herbig-Haro objects. We report the detection of a new source (NH$_{3}-$S) in the vicinity of HH 111/HH 121 ($\sim$0.03 pc from the HH 111 jet source) in two epochs of the ammonia observations. This constitutes the first detection of this source, in a region which has been thoroughly covered previously by both continuum and spectral line interferometric observations. We study the kinematic and physical properties of HH 111 and the newly discovered NH$_{3}-$S. We also use HCO$^{+}$ and HCN $(J=4-3)$ data obtained with the James Clerk Maxwell Telescope and archival Atacama Large Millimeter/submillimeter Array $^{13}$CO, $^{12}$CO, and C$^{18}$O $(J=2-1)$, N$_2$D$^{+}$ $(J=3-2)$, and $^{13}$CS $(J=5-4)$ data to gain insight into the nature of NH$_{3}-$S. The chemical structure of NH$_3-$S shows evidence for "selective freeze-out", an inherent characteristic of dense cold cores. The inner part of NH$_3-$S shows subsonic non-thermal velocity dispersions indicating a "coherent core", while they increase in the direction of the jets. Archival near- to far-infrared data show no indication of any embedded source in NH$_3-$S. The properties of NH$_3-$S and its location in the infrared dark cloud suggest that it is a starless core located in a turbulent medium with turbulence induced by Herbig-Haro jets and associated outflows. More data is needed to fully understand the physical and chemical properties of NH$_3-$S and if/how its evolution is affected by nearby jets.
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first results from a 1 3 cm expanded Very Large Array survey of massive protostellar objects g35 03 0 35
The Astrophysical Journal, 2011Co-Authors: C L Brogan, C J Chandler, C J Cyganowski, T R Hunter, R Friesen, Remy IndebetouwAbstract:We have performed a 1.3 cm survey of 24 massive young stellar objects (MYSOs) using the Expanded Very Large Array. The sources in the sample exhibit a broad range of massive star formation signposts including infrared dark clouds (IRDCs), ultra-compact H II (UC H II) regions, and extended 4.5 μm emission in the form of extended green objects (EGOs). In this work, we present results for G35.03+0.35 which exhibits all of these phenomena. We simultaneously image the 1.3 cm NH3 (1,1) through (6,6) inversion lines, four CH3OH transitions, two H recombination lines, plus continuum at 0.05 pc resolution. We find three areas of thermal NH3 emission, two within the EGO (designated as the NE and SW cores) and one toward an adjacent IRDC. The NE core contains a UC H II region (CM1) and a candidate hyper-compact H II region (CM2). A region of non-thermal, likely masing NH3 (3,3) and (6,6) emission is coincident with an arc of 44 GHz CH3OH masers. We also detect two new 25 GHz Class-I CH3OH masers. A complementary Submillimeter Array 1.3 mm continuum image shows that the distribution of dust emission is similar to the lower-lying NH3 lines, all peaking to the NW of CM2, indicating the likely presence of an additional MYSO in this protocluster. By modeling the NH3 and 1.3 mm continuum data, we obtain gas temperatures of 20-220 K and masses of 20-130 M ☉. The diversity of continuum emission properties and gas temperatures suggests that objects in a range of evolutionary states exist concurrently in this protocluster.
C J Law - One of the best experts on this subject based on the ideXlab platform.
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a distant fast radio burst associated with its host galaxy by the Very Large Array
The Astrophysical Journal, 2020Co-Authors: C J Law, B J Butler, Sarah Burkespolaor, Barak Zackay, A Mannings, Nicolas Tejos, A Josephy, B C Andersen, Xavier J Prochaska, P ChawlaAbstract:We present the discoVery and subarcsecond localization of a new fast radio burst (FRB) by the Karl G. Jansky Very Large Array (VLA) and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc cm⁻³. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hr of VLA observing and 153 hr of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB with a pair of galaxies with r ∼ 23 mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly 3×10⁻⁴ hr⁻¹. The two putative host galaxies have similar photometric redshifts of z_(phot) ∼ 0.6, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm⁻³) electron column density associated with the FRB environment or host galaxy/galaxies.
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a distant fast radio burst associated to its host galaxy with the Very Large Array
arXiv: High Energy Astrophysical Phenomena, 2020Co-Authors: C J Law, B J Butler, Sarah Burkespolaor, J X Prochaska, Barak Zackay, A Mannings, Nicolas Tejos, A Josephy, B C Andersen, P ChawlaAbstract:We present the discoVery and subarcsecond localization of a new Fast Radio Burst with the Karl G. Jansky Very Large Array and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc/cm3. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hours of VLA observing and 153 hours of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB to a pair of galaxies with $\rm{r}\sim23$ mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly $3\times10^{-4}\ \rm{hr}^{-1}$. The two putative host galaxies have similar photometric redshifts of $z_{\rm{phot}}\sim0.6$, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm3) electron column density associated with the FRB environment or host galaxy/galaxies.
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commensal multi user observations with an ethernet based jansky Very Large Array
arXiv: Instrumentation and Methods for Astrophysics, 2019Co-Authors: Jack Hickish, Sarah Burkespolaor, Paul Demorest, Steve Croft, Tony Beasley, Geoff Bower, Dave Deboer, Bill Diamond, Vishal Gajjar, C J LawAbstract:Over the last decade, the continuing decline in the cost of digital computing technology has brought about a dramatic transformation in how digital instrumentation for radio astronomy is developed and operated. In most cases, it is now possible to interface consumer computing hardware, e.g. inexpensive graphics processing units and storage devices, directly to the raw data streams produced by radio telescopes. Such systems bring with them myriad benefits: straightforward upgrade paths, cost savings through leveraging an economy of scale, and a lowered barrier to entry for scientists and engineers seeking to add new instrument capabilities. Additionally, the typical data-interconnect technology used with general-purpose computing hardware -- Ethernet -- naturally permits multiple subscribers to a single raw data stream. This allows multiple science programs to be conducted in parallel. When combined with broad bandwidths and wide primary fields of view, radio telescopes become capable of achieving many science goals simultaneously. Moreover, because many science programs are not strongly dependent on observing cadence and direction (e.g. searches for extraterrestrial intelligence and radio transient surveys), these so-called "commensal" observing programs can dramatically increase the scientific productivity and discoVery potential of an observatory. In this whitepaper, we detail a project to add an Ethernet-based commensal observing mode to the Jansky Very Large Array (VLA), and discuss how this mode could be leveraged to conduct a powerful program to constrain the distribution of advanced life in the universe through a search for radio emission indicative of technology. We also discuss other potential science use-cases for the system, and how the system could be used for technology development towards next-generation processing systems for the Next Generation VLA.
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vys a protocol for commensal fast transient searches and data processing at the Very Large Array
Journal of Astronomical Instrumentation, 2018Co-Authors: Martin Pokorny, B J Butler, C J Law, Geoffrey C Bower, Sarah Burkespolaor, Paul Demorest, Shakeh Khudikyan, Joseph T W Lazio, James Robnett, Michael P RupenAbstract:We describe a new protocol deployed at the National Radio Astronomy Observatory’s Karl G. Jansky Very Large Array (VLA) to support the distribution of data in support of commensal data analysis. Th...
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realfast real time commensal fast transient surveys with the Very Large Array
Astrophysical Journal Supplement Series, 2018Co-Authors: C J Law, B J Butler, Martin Pokorny, Geoffrey C Bower, Sarah Burkespolaor, Paul Demorest, Shakeh Khudikyan, T J W Lazio, A Halle, James RobnettAbstract:Radio interferometers have the ability to precisely localize and better characterize the properties of sources. This ability is having a powerful impact on the study of fast radio transients, where a few milliseconds of data is enough to pinpoint a source at cosmological distances. However, recording interferometric data at millisecond cadence produces a terabyte-per-hour data stream that strains networks, computing systems, and archives. This challenge mirrors that of other domains of science, where the science scope is limited by the computational architecture as much as the physical processes at play. Here, we present a solution to this problem in the context of radio transients: realfast, a commensal, fast transient search system at the Jansky Very Large Array. Realfast uses a novel architecture to distribute fast-sampled interferometric data to a 32-node, 64-GPU cluster for real-time imaging and transient detection. By detecting transients in situ, we can trigger the recording of data for those rare, brief instants when the event occurs and reduce the recorded data volume by a factor of 1000. This makes it possible to commensally search a data stream that would otherwise be impossible to record. This system will search for millisecond transients in more than 1000 hours of data per year, potentially localizing several Fast Radio Bursts, pulsars, and other sources of impulsive radio emission. We describe the science scope for realfast, the system design, expected outcomes, and ways real-time analysis can help in other fields of astrophysics.
B J Butler - One of the best experts on this subject based on the ideXlab platform.
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a distant fast radio burst associated with its host galaxy by the Very Large Array
The Astrophysical Journal, 2020Co-Authors: C J Law, B J Butler, Sarah Burkespolaor, Barak Zackay, A Mannings, Nicolas Tejos, A Josephy, B C Andersen, Xavier J Prochaska, P ChawlaAbstract:We present the discoVery and subarcsecond localization of a new fast radio burst (FRB) by the Karl G. Jansky Very Large Array (VLA) and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc cm⁻³. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hr of VLA observing and 153 hr of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB with a pair of galaxies with r ∼ 23 mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly 3×10⁻⁴ hr⁻¹. The two putative host galaxies have similar photometric redshifts of z_(phot) ∼ 0.6, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm⁻³) electron column density associated with the FRB environment or host galaxy/galaxies.
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a distant fast radio burst associated to its host galaxy with the Very Large Array
arXiv: High Energy Astrophysical Phenomena, 2020Co-Authors: C J Law, B J Butler, Sarah Burkespolaor, J X Prochaska, Barak Zackay, A Mannings, Nicolas Tejos, A Josephy, B C Andersen, P ChawlaAbstract:We present the discoVery and subarcsecond localization of a new Fast Radio Burst with the Karl G. Jansky Very Large Array and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc/cm3. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hours of VLA observing and 153 hours of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB to a pair of galaxies with $\rm{r}\sim23$ mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly $3\times10^{-4}\ \rm{hr}^{-1}$. The two putative host galaxies have similar photometric redshifts of $z_{\rm{phot}}\sim0.6$, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm3) electron column density associated with the FRB environment or host galaxy/galaxies.
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vys a protocol for commensal fast transient searches and data processing at the Very Large Array
Journal of Astronomical Instrumentation, 2018Co-Authors: Martin Pokorny, B J Butler, C J Law, Geoffrey C Bower, Sarah Burkespolaor, Paul Demorest, Shakeh Khudikyan, Joseph T W Lazio, James Robnett, Michael P RupenAbstract:We describe a new protocol deployed at the National Radio Astronomy Observatory’s Karl G. Jansky Very Large Array (VLA) to support the distribution of data in support of commensal data analysis. Th...
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the next generation Very Large Array a technical overview
arXiv: Instrumentation and Methods for Astrophysics, 2018Co-Authors: R Selina, B J Butler, Barry Clark, E J Murphy, Mark M Mckinnon, A J Beasley, C L Carilli, Alan Erickson, Wes Grammer, J M JacksonAbstract:The next-generation Very Large Array (ngVLA) is an astronomical observatory planned to operate at centimeter wavelengths (25 to 0.26 centimeters, corresponding to a frequency range extending from 1.2 GHz to 116 GHz). The observatory will be a synthesis radio telescope constituted of approximately 214 reflector antennas each of 18 meters diameter, operating in a phased or interferometric mode. We provide an overview of the current system design of the ngVLA. The concepts for major system elements such as the antenna, receiving electronics, and central signal processing are presented. We also describe the major development activities that are presently underway to advance the design.
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realfast real time commensal fast transient surveys with the Very Large Array
Astrophysical Journal Supplement Series, 2018Co-Authors: C J Law, B J Butler, Martin Pokorny, Geoffrey C Bower, Sarah Burkespolaor, Paul Demorest, Shakeh Khudikyan, T J W Lazio, A Halle, James RobnettAbstract:Radio interferometers have the ability to precisely localize and better characterize the properties of sources. This ability is having a powerful impact on the study of fast radio transients, where a few milliseconds of data is enough to pinpoint a source at cosmological distances. However, recording interferometric data at millisecond cadence produces a terabyte-per-hour data stream that strains networks, computing systems, and archives. This challenge mirrors that of other domains of science, where the science scope is limited by the computational architecture as much as the physical processes at play. Here, we present a solution to this problem in the context of radio transients: realfast, a commensal, fast transient search system at the Jansky Very Large Array. Realfast uses a novel architecture to distribute fast-sampled interferometric data to a 32-node, 64-GPU cluster for real-time imaging and transient detection. By detecting transients in situ, we can trigger the recording of data for those rare, brief instants when the event occurs and reduce the recorded data volume by a factor of 1000. This makes it possible to commensally search a data stream that would otherwise be impossible to record. This system will search for millisecond transients in more than 1000 hours of data per year, potentially localizing several Fast Radio Bursts, pulsars, and other sources of impulsive radio emission. We describe the science scope for realfast, the system design, expected outcomes, and ways real-time analysis can help in other fields of astrophysics.
R A Perley - One of the best experts on this subject based on the ideXlab platform.
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deep 3 ghz observations of the lockman hole north with the Very Large Array ii catalogue and μjy source properties
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: T Vernstrom, W D Cotton, K I Kellermann, D Scott, J V Wall, J J Condon, R A PerleyAbstract:This is the second of two papers describing the observations and source catalogues derived from sensitive 3-GHz images of the Lockman Hole North using the Karl G. Jansky Very Large Array. We describe the reduction and cataloguing process, which yielded an image with 8 arcsec resolution and instrumental noise of \sigma$_{\rm n}$=1.0 \mu Jy beam$^{-1}$ rms (before primary beam corrections) and a catalogue of 558 sources detected above 5\sigma$_{\rm n}$. We include details of how we estimate source spectral indices across the 2-GHz VLA bandwidth, finding a median index of -0.76$\pm$0.04. Stacking of source spectra reveals a flattening of spectral index with decreasing flux density. We present a source count derived from the catalogue. We show a traditional count estimate compared with a completely independent estimate made via a P(D) confusion analysis, and find Very good agreement. Cross-matches of the catalogue with X-ray, optical, infrared, radio, and redshift catalogues are also presented. The X-ray, optical and infrared data, as well as AGN selection criteria allow us to classify 10 per cent as radio-loud AGN, 28 percent as radio-quiet AGN, and 58 per cent as star-forming galaxies, with only 4 per cent unclassified.
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deep 3 ghz observations of the lockman hole north with the Very Large Array i source extraction and uncertainty analysis
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: T Vernstrom, W D Cotton, D Scott, J V Wall, J J Condon, R A PerleyAbstract:This is the first of two papers describing the observations and cataloguing of deep 3-GHz observations of the Lockman Hole North using the Karl G. Jansky Very Large Array. The aim of this paper is to investigate, through the use of simulated images, the uncertainties and accuracy of source-finding routines, as well as to quantify systematic effects due to resolution, such as source confusion and source size. While these effects are not new, this work is intended as a particular case study that can be scaled and translated to other surveys. We use the simulations to derive uncertainties in the fitted parameters, as well as bias corrections for the actual catalogue (presented in Paper 2). We compare two different source-finding routines, OBIT and AEGEAN, and two different effective resolutions, 8 and 2.75 arcsec. We find that the two routines perform comparably well, with OBIT being slightly better at de-blending sources, but slightly worse at fitting resolved sources. We show that 30 to 70 per cent of sources are missed or fit inaccurately once the source size becomes Larger than the beam, possibly explaining source count errors in high-resolution surveys. We also investigate the effect of blending, finding that any sources with separations smaller than the beam size are fit as single sources. We show that the use of machine-learning techniques can correctly identify blended sources up to 90 per cent of the time, and prior-driven fitting can lead to a 70 per cent improvement in the number of de-blended sources.
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the expanded Very Large Array a new telescope for new science
The Astrophysical Journal, 2011Co-Authors: R A Perley, B J Butler, C J Chandler, J M WrobelAbstract:Since its commissioning in 1980, the Very Large Array (VLA) has consistently demonstrated its scientific productivity. However, its fundamental capabilities have changed little since 1980, particularly in the key areas of sensitivity, frequency coverage, and velocity resolution. These limitations have been addressed by a major upgrade of the Array, which began in 2001 and will be completed at the end of 2012. When completed, the Expanded VLA?the EVLA?will provide complete frequency coverage from 1 to 50?GHz, a continuum sensitivity of typically 1 ?Jy beam?1 (in 9 hr with full bandwidth), and a modern correlator with vastly greater capabilities and flexibility than the VLA's. In this Letter, we describe the goals of the EVLA project, its current status, and the anticipated expansion of capabilities over the next few years. User access to the Array through the Open Shared Risk Observing and Resident Shared Risk Observing programs is described. The following papers in this special issue, derived from observations in its early science period, demonstrate the astonishing breadth of this most flexible and powerful general-purpose telescope.
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the expanded Very Large Array a new telescope for new science
arXiv: Instrumentation and Methods for Astrophysics, 2011Co-Authors: R A Perley, B J Butler, C J Chandler, J M WrobelAbstract:Since its commissioning in 1980, the Very Large Array (VLA) has consistently demonstrated its scientific productivity. However, its fundamental capabilities have changed little since 1980, particularly in the key areas of sensitivity, frequency coverage, and velocity resolution. These limitations have been addressed by a major upgrade of the Array, which began in 2001 and will be completed at the end of 2012. When completed, the Expanded VLA -- the EVLA -- will provide complete frequency coverage from 1 to 50 GHz, a continuum sensitivity of typically 1 microJy/beam (in 9 hours with full bandwidth), and a modern correlator with vastly greater capabilities and flexibility than the VLA's. In this paper we describe the goals of the EVLA project, its current status, and the anticipated expansion of capabilities over the next few years. User access to the Array through the OSRO and RSRO programs is described. The following papers in this special issue, derived from observations in its early science period, demonstrate the astonishing breadth of this most flexible and powerful general-purpose telescope.
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the expanded Very Large Array
arXiv: Instrumentation and Methods for Astrophysics, 2009Co-Authors: R A Perley, P Napier, J M Jackson, B J Butler, B Carlson, D Fort, P E Dewdney, Barry Clark, R Hayward, S DurandAbstract:In almost 30 years of operation, the Very Large Array (VLA) has proved to be a remarkably flexible and productive radio telescope. However, the basic capabilities of the VLA have changed little since it was designed. A major expansion utilizing modern technology is currently underway to improve the capabilities of the VLA by at least an order of magnitude in both sensitivity and in frequency coverage. The primary elements of the Expanded Very Large Array (EVLA) project include new or upgraded receivers for continuous frequency coverage from 1 to 50 GHz, new local oscillator, intermediate frequency, and wide bandwidth data transmission systems to carry signals with 16 GHz total bandwidth from each antenna, and a new digital correlator with the capability to process this bandwidth with an unprecedented number of frequency channels for an imaging Array. Also included are a new monitor and control system and new software that will provide telescope ease of use. Scheduled for completion in 2012, the EVLA will provide the world research community with a flexible, powerful, general-purpose telescope to address current and future astronomical issues.