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  • richardmitnick 2:30 pm on June 9, 2016 Permalink | Reply
    Tags: , , NRAO VLA, , VLASS begins   

    From NRAO: “The VLA Sky Survey Pilot Begins” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    6.9.16

    1
    Claire Chandler, VLASS Project Director

    1

    The Very Large Array Sky Survey (VLASS) will be a three-epoch (32-month cadence), all-sky, S-band (2-4 GHz) continuum polarimetry survey with 2.5-arcsecond spatial resolution. The survey will span seven years and six VLA configuration cycles, and will begin in 2017, pending successful achievement of the design phase milestones. The total VLA telescope time required for the survey is ~5400 hours, or ~900 hours per configuration cycle.

    With the decision to proceed with the VLASS (see 17 Dec 2015 e-News), a 200-hr pilot in the recently commenced VLA B-configuration of semester 2016A has been approved, with the first observations starting June 2016. This pilot survey will inform VLASS implementation and operational issues associated with the full survey as input to design reviews, while at the same time providing the community with early VLASS-type data products. The pilot will be observed in as similar a mode to the full VLASS as possible, including:

    S-band (2-4 GHz), 1024 x 2 MHz channels
    VLA B-configuration, 2.5-arcsec resolution
    On-The-Fly (OTF) mosaics scanning at 3.31 arcmin/sec in right ascension, at constant declination
    Net mapping speed ~20 deg2/hr, 4-hr scheduling blocks covering 80 deg2 (10o x 8o tiles)

    Some areas will be covered with three passes to provide a similar sensitivity as that expected from three epochs of the full VLASS (70 microJy/beam), while others will be observed with a single pass (120 microJy/beam) to maximize sky coverage. The pilot will cover key galactic and extragalactic fields that have good multi-wavelength ancillary data, as well as covering areas of sky with good prior radio observations for technical validation of the OTF mosaicking observing mode. The total area to be covered will be ~2500 deg2, and will include:

    VLASS Pilot Fields, 3 passes (70 microJy/beam):

    Galactic Plane fields: Galactic Center, Cygnus, Cepheus
    Extragalactic fields: Cosmological Evolution Survey, Sloane Digital Sky Survey (SDSS) Stripe 82, Chandra Deep Field South

    VLASS Pilot Fields, 1 pass (120 microJy/beam):

    SDSS South Galactic Cap / FIRST southern sky for declination > 0 deg
    SDSS North Galactic Cap fields: Great Observatories Origins Deep Survey – North, Elais-N1, Lockman Hole, H-ATLAS North, Bootes

    Raw visibility data will be immediately available through the NRAO archive under project code TVPILOT. Data products (calibrated visibility data, images) will be made available after undergoing quality assurance.

    At this time, we encourage community participation in various Science Working Groups as we define and refine the operational aspects of the pilot survey:

    Extragalactic Working Group
    Galactic Working Group
    Transients Working Group
    Polarization Working Group
    EPO Working Group
    Survey Implementation Working Group
    NRAO Data Products, Archiving and Enhanced Data Products Working Group

    A Google Group has been set up to facilitate discussion and communication within the working groups, please visit to sign up.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO/GBT radio telescope
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 11:49 am on March 14, 2016 Permalink | Reply
    Tags: , , NRAO VLA, Our Galactic Center   

    From AAS NOVA: “Imaging the Heart of Our Galaxy” 

    AASNOVA

    Amercan Astronomical Society

    14 March 2016
    Susanna Kohler

    Galactic Center NRAO VLA
    Galactic Center. NRAO/VLA

    New radio images of the center of the Milky Way are providing an unprecedented view of the structure and processes occurring in the Galactic center.

    Improved Radio View

    A recent study led by Jun-Hui Zhao (Harvard-Smithsonian Center for Astrophysics) presents new images of the Galactic center using the Jansky Very Large Array (JVLA) at 5.5 GHz.

    NRAO VLA
    NRAO/VLA

    The images center on the radio-bright zone at the core of our galaxy, with the field of view covering the central 13’ of the Milky Way — equivalent to a physical size of ~100 light-years.

    Due to recent hardware and software improvements in the VLA, these images are much deeper than any previously obtained of the Galactic center, reaching an unprecedented 100,000:1 dynamic range. Not only do these observations provide a detailed view of previously known structures within the Sagittarius A radio complex in the Milky Way’s heart, but they also reveal new features that can help us understand the processes that formed this bright complex.

    Features in Sagittarius A

    Sgr A consists of three main components nested within each other: the supernova remnant Sgr A East, the mini-spiral structure Sgr A West (located off-center within the Sgr A East structure), and the compact radio source Sgr A* (located near the center of the mini-spiral). Sgr A* is the supermassive black hole that resides at the very center of the Milky Way.

    SGR A
    SGR A*

    The newest JVLA images reveal numerous filamentary sources that trace out two radio lobes, oriented nearly perpendicular to the Galactic plane and ~50 light-years in size. These are smaller radio counterparts to the enormous (on the scale of 30,000 light-years!) gamma-ray Fermi bubbles that have been observed to extend from the Galactic center. The bipolar radio structures appear to be due to winds emanating from Sgr A* itself, from a central cluster of massive stars, or from a combination of the two.

    Supernova Structures

    The outermost shape of Sgr A East — which looks like an elliptical ring — is thought to be an expanding spherical shell from a past supernova explosion, appearing as an ellipse because of our angle of view. In the newest JVLA images, Zhao and collaborators identify a new structure inside of the ring that they term the “Sigma Front”.

    The authors argue that this emission front — which is shaped like the capital Greek letter sigma — may be the reflection of the supernova blast wave bouncing off of the dense, clumpy circumnuclear molecular disk around Sgr A* (which encircles the mini-spiral, but isn’t visible in radio wavelengths). Under this assumption, they use the Sigma Front to constrain the geometry of the supernova explosion.

    These new JVLA images contain a wealth of information in their detail, and analysis is only just beginning. Further examination of these images will continue to help us learn about the activity at the heart of our galaxy.
    Citation

    Jun-Hui Zhao et al 2016 ApJ 817 171. doi:10.3847/0004-637X/817/2/171

    See the full article here .

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  • richardmitnick 8:31 am on December 29, 2015 Permalink | Reply
    Tags: , , Magnetic Fields and Star Formation, NRAO VLA,   

    From NRAO: “Twisted Magnetic Fields Give New Insights on Star Formation” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    1
    Magnetic field lines (purple) are twisted as they are dragged inward toward a swirling, dusty disk surrounding a young star in this artist’s conception. CREDIT: Bill Saxton, NRAO/AUI/NSF.

    21 December 2015
    Media Contact:
    Dave Finley, Public Information Officer
    (575) 835-7302
    dfinley@nrao.edu

    Using new images that show unprecedented detail, scientists have found that material rotating around a very young protostar probably has dragged in and twisted magnetic fields from the larger area surrounding the star. The discovery, made with the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) radio telescope, has important implications for how dusty disks — the raw material for planet formation — grow around young stars.

    NRAO VLA
    VLA

    The scientists studied a young protostar about 750 light-years from Earth in the constellation Perseus. Their observations, made in 2013 and 2014, measured the alignment, or polarization, of radio waves emitted by material, mostly dust, falling into a burgeoning disk orbiting the young star. The polarization information revealed the configuration of magnetic fields in this region near the star.

    “The alignment of magnetic fields in this region near young stars is very important to the development of the disks that orbit them. Depending on its alignment, the magnetic field can either hinder the growth of the disk or help funnel material onto the disk, allowing it to grow,” said Leslie Looney, of the University of Illinois at Urbana-Champaign.

    As material from the envelope of dust and gas surrounding the young star falls inward toward the rotating disk, it is likely to drag magnetic field lines with it. Because of this, the structure of the magnetic field near the star will become different from the field’s structure farther away.

    “Our VLA observations are showing us this region, where the change in shape of the magnetic field is taking place,” said Erin Cox, also of the University of Illinois Urbana-Champaign. The observations, she added, produced the first images at wavelengths of 8 and 10 millimeters to show the polarization near a protostar.

    The observations also indicated that millimeter- to centimeter-sized particles are numerous in the disk surrounding the young star. Since the protostar is only about 10,000 years old — very short in astronomical timescales — this may mean that such grains form and grow quickly in the environment of a still-forming star.

    The star, dubbed NGC1333 IRAS 4A, is one of two young stars forming within a common envelope of dust and gas. The disk around it contains material with a total mass more than twice that of our Sun.

    Cox and Looney are part of an international team of astronomers studying the protostar. The scientists are reporting their results in the Astrophysical Journal Letters.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 10:41 am on November 18, 2015 Permalink | Reply
    Tags: , , , NRAO VLA   

    From Hubble: “A Multi-Wavelength View of Radio Galaxy Hercules A” 

    NASA Hubble Telescope

    Hubble

    November 29, 2012
    Reposted by ESA 16/11/2015

    Ray Villard
    Space Telescope Science Institute, Baltimore, Md.
    410-338-4514
    villard@stsci.edu

    John Stoke
    National Radio Astronomy Observatory, Charlottesville, Va.
    434-244-6896
    jstoke@nrao.edu

    Dave Finley
    National Radio Astronomy Observatory, Socorro, N.M.
    575-835-7302
    dfinley@nrao.edu

    1
    NASA, ESA, S. Baum, C. O’Dea (RIT), R. Perley, W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

    [ESA] Scientists often use the combined power of multiple telescopes to reveal the secrets of the Universe – and this image is a prime example of when this technique is strikingly effective.

    [HubbleSite]Spectacular jets powered by the gravitational energy of a supermassive black hole in the core of the elliptical galaxy Hercules A illustrate the combined imaging power of two of astronomy’s cutting-edge tools, the Hubble Space Telescope’s Wide Field Camera 3 [WFC3], and the recently upgraded Karl G. Jansky Very Large Array (VLA) radio telescope in New Mexico.

    NASA Hubble WFC3
    WFC3

    NRAO VLA
    VLA

    Some two billion light-years away, the yellowish elliptical galaxy in the center of the image appears quite ordinary as seen by Hubble in visible wavelengths of light. The elliptical galaxy is roughly 1,000 times more massive than the bulge of our Milky Way and harbors a 2.5-billion-solar-mass central black hole that is 1,000 times more massive than the black hole in the Milky Way. But the innocuous-looking galaxy, also known as 3C 348, has long been known as the brightest radio-emitting object in the constellation Hercules. Emitting nearly a billion times more power in radio wavelengths than our Sun, the galaxy is one of the brightest extragalactic radio sources in the entire sky.

    The VLA radio data reveal enormous, optically invisible jets that, at one-and-a-half million light-years wide, dwarf the visible galaxy from which they emerge. The jets are very-high-energy plasma beams, subatomic particles and magnetic fields shot at nearly the speed of light from the vicinity of the black hole. The outer portions of both jets show unusual ring-like structures suggesting a history of multiple outbursts from the supermassive black hole at the center of the galaxy.

    The innermost parts of the jets are not visible because of the extreme velocity of the material; relativistic effects confine all of the light to a narrow cone aligned with the jets, and so that light is not seen by us. Far from the galaxy, the jets become unstable and break up into the rings and wisps.

    The entire radio source is surrounded by a very hot, X-ray-emitting cloud of gas, not seen in this optical-radio composite.

    Hubble’s view of the field also shows a companion elliptical galaxy very close to the center of the optical-radio source, which may be merging with the central galaxy. Several other elliptical and spiral galaxies that are visible in the Hubble data may be members of a cluster of galaxies. Hercules A is by far the brightest and most massive galaxy in the cluster.

    See the full article here .

    Please help promote STEM in your local schools.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 12:16 pm on November 16, 2015 Permalink | Reply
    Tags: , , NRAO VLA,   

    From NRAO: “35 Years of Constraints on Thermonuclear Supernova Progenitors with the VLA” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    11.16.2015
    Laura Chomiuk, Alicia M. Soderberg, Roger A. Chevalier, Seth Bruzewski, Ryan J. Foley, Jerod Parrent, Jay Strader, Carles Badenes, Claes Fransson, Atish Kamble, Raffaella Margutti, Michael P. Rupen, & Joshua D. Simon

    Today, the progenitors of Type Ia Supernovae (SNe) and their lower-luminosity thermonuclear cousins remain shrouded in mystery. While researchers agree that these SNe mark the explosions of white dwarf stars, it is unclear what destabilizes the white dwarf: merger with another white dwarf, accretion from a H-rich main sequence or giant star, or perhaps interaction with a helium star? Deep radio observations with the VLA can tackle this puzzle by searching for material in the environments of SNe, left over from the process of mass transfer onto the white dwarf.

    1

    When a SN shock interacts with surrounding material, relativistic electrons are accelerated and magnetic fields are amplified, yielding synchrotron emission. Therefore, radio observations of SNe provide insight into pre-SN mass loss and SN progenitors. In a paper recently submitted to Astrophysical Journal, our team combined archival radio observations from 30 years of legacy VLA operations with new observations from the Karl G. Jansky VLA. This yields a sample of 85 thermonuclear SNe observed by the VLA in the first year following explosion. None are detected. These radio limits imply that Type Ia supernovae explode in low-density environments.

    We use our limits on the density of material surrounding these SNe to constrain the fraction of thermonuclear SNe that might have red giant companions. We make use of legacy VLA observations of Galactic symbiotic binaries carried out by E. Seaquist and collaborators to characterize the density of material around white dwarfs with red giant companions, and find that, for many SNe, we can rule out such symbiotic progenitors. We conclude that ≲10% of thermonuclear SNe have red giant companions.

    Future work with the VLA can improve upon these results via: (a) further observations of Galactic symbiotic binaries that more completely pin down their wind properties; (b) additional observations of a large number of Type Ia SNe, providing even stronger constraints on the fraction with red giant companion; and (c) analysis of radio observations at longer times after explosion (1-100 years, as the SN transitions to a SN remnant) to probe the SN environment at larger radii.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 2:05 pm on November 6, 2015 Permalink | Reply
    Tags: , , , NRAO VLA, ,   

    From AAS NOVA: “Masquerading as a Merger” 

    AASNOVA

    Amercan Astronomical Society

    6 November 2015
    Susanna Kohler

    1
    Mrk 739, seen here, is an example of a galaxy merger where the two nuclei at the center of the newly-formed galaxy can easily be identified as being separate. For trickier cases, astronomers often identify dual AGN by signatures in their spectra. [SDSS]

    Dual active galactic nuclei (AGN), an intermediary product of galaxy mergers, can give us a better understanding of what happens when two galaxies collide. But because the angular separation of the two galactic nuclei is so small at this stage, identifying these systems is very difficult. In a recent study, a team of authors proposes a new technique for confirming dual AGN candidates.

    2
    Total-intensity VLA image for J1023+3243. This system is confirmed as a dual AGN; the two compact radio cores are separately identifiable here. [Müller-Sánchez et al. 2015]

    Signatures in Spectra

    One approach commonly used to identify dual AGN candidates is to look for signatures in the spectra of these galaxies. Light is emitted by ionized gas in the narrow-line region (NLR), the region that extends from a few hundreds of parsecs to ~30kpc from the nuclei. The spatially-averaged spectrum of this region for dual AGN, however, appears double-peaked due to the motion of the two nuclei rotating around each other.

    But there’s a problem with using this technique to identify dual AGN: other processes also produce double-peaked narrow-line emission, mimicking the behavior of dual AGN. These processes include the rotation of ionized gas in the galactic disk, and the motion of radio jets emitted from the AGN.

    A team of scientists led by Francisco Müller-Sánchez (University of Colorado Boulder) have proposed that the use of a combination of high-resolution radio observations and spatially-resolved spectroscopy could be used to discern between these possible cases.

    Dual AGN or Moving Gas?

    To test this method, the group examined a sample of 18 active galactic nuclei from the Sloan Digital Sky Survey [SDSS].

    SDSS Telescope
    SDSS telescope, Apache Point, NM, USA

    These AGN had previously been identified as candidate dual AGN with double-peaked narrow emission lines. The team obtained both optical long-slit spectroscopy and high-resolution Very Large Array observations of these AGN.

    NRAO VLA
    NRAO/VLA

    They then combined this information to identify the cause of the double-peaked lines in each case.

    3
    Total-intensity VLA image for J0009–0036. This system contains a two-sided radio jet, causing the extended radio emission seen here. [Müller-Sánchez et al. 2015]

    Müller-Sánchez and collaborators found the following:

    Roughly 15% are confirmed to be dual AGN. In these cases, distinctly separated radio cores are visible in the Very Large Array data, but their spectra are similar to those of single AGN.

    Roughly 75% have double-peaked lines due to gas kinematics, instead. These kinematics include jets, rotating NLR regions, and wind-driven outflows. The jets are identifiable by their extended radio emission and steeper spectra, whereas the rotating NLR regions and wind-driven outflows are identifiable by their lack of additional radio cores or extended emission, and the morphology of their spectra.

    Only two cases of the 18 were ambiguous and couldn’t be identified. The authors conclude that their method of confirming dual AGN is therefore a powerful means of identifying dual AGN that have very small angular separations.
    Citation

    F. Müller-Sánchez et al 2015 ApJ 813 103. doi:10.1088/0004-637X/813/2/103

    See the full article here .

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  • richardmitnick 6:10 am on October 15, 2015 Permalink | Reply
    Tags: , , NRAO VLA   

    From NRAO: “VLA Reveals Spectacular “Halos” of Spiral Galaxies” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    13 October 2015
    Dave Finley, National Radio Astronomy Observatory
    (575) 835-7302
    dfinley@nrao.edu

    Carlos J. Vargas, New Mexico State University
    (575)646-3409
    cjvargas@nmsu.edu

    1
    Composite image of an edge-on spiral galaxy with a radio halo produced by fast-moving particles in the galaxy’s magnetic field. In this image, the large, grey-blue area is a single image formed by combining the radio halos of 30 different galaxies, as seen with the Very Large Array. At the center is a visible-light image of one of the galaxies, NGC 5775, made using the Hubble Space Telescope. This visible-light image shows only the inner part of the galaxy’s star-forming region, outer portions of which extend horizontally into the area of the radio halo.
    IMAGE CREDIT: Jayanne English (U. Manitoba), with support from Judith Irwin and Theresa Wiegert (Queen’s U.) for the CHANG-ES consortium; NRAO/AUI/NSF; NASA/STScI
    SCIENCE CREDIT: Theresa Wiegert, Judith Irwin and the CHANG-ES consortium.

    NASA Hubble Telescope
    NASA/ESA Hubble

    A study of spiral galaxies seen edge-on has revealed that “halos” of cosmic rays and magnetic fields above and below the galaxies’ disks are much more common than previously thought.

    An international team of astronomers used the Karl G. Jansky Very Large Array (VLA) [image and link below] to study 35 edge-on spiral galaxies at distances from 11 million to 137 million light-years from Earth. The study took advantage of the ability of the VLA, following completion of a decade-long upgrade project, to detect radio emission much fainter than previously possible.

    “We knew before that some halos existed, but, using the full power of the upgraded VLA and the full power of some advanced image-processing techniques, we found that these halos are much more common among spiral galaxies than we had realized,” said Judith Irwin, of Queen’s University in Canada, leader of the project.

    Spiral galaxies, like our own Milky Way, have the vast majority of their stars, gas, and dust in a flat, rotating disk with spiral arms. Most of the light and radio waves seen with telescopes come from objects in that disk. Learning about the environment above and below such disks has been difficult.

    “Studying these halos with radio telescopes can give us valuable information about a wide range of phenomena, including the rate of star formation within the disk, the winds from exploding stars, and the nature and origin of the galaxies’ magnetic fields,” said Theresa Wiegert, also of Queen’s University, lead author of a paper in the Astronomical Journal reporting the team’s findings. The paper provides the first analysis of data from all 35 galaxies in the study.

    To see how extensive a “typical” halo is, the astronomers scaled their images of 30 of the galaxies to the same diameter, then another of the authors, Jayanne English, of the University of Manitoba in Canada, combined them into a single image. The result, said Irwin, is “a spectacular image showing that cosmic rays and magnetic fields not only permeate the galaxy disk itself, but extend far above and below the disk.”

    The combined image, the scientists said, confirms a prediction of such halos made in 1961.

    Along with the report on their findings, the astronomers also are making their first batch of specialized VLA images available to other researchers. In previous publications, the team described the details of their project and its goals. The team has completed a series of VLA observations and their latest paper is based on analysis of their first set of images. They now are analyzing additional datasets, and also will make those additional images available to other scientists when they publish the results of the later analyses.

    “The results from this survey will help answer many unsolved questions in galactic evolution and star formation,” said Marita Krause of the Max-Planck Institute for Radioastronomy in Bonn, Germany.

    The data are available at: http://queensu.ca/changes

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 8:21 pm on July 27, 2015 Permalink | Reply
    Tags: , , NRAO VLA,   

    From NRAO: “Brown Dwarfs, Stars Share Formation Process, New Study Indicates” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    23 July 2015
    Dave Finley, Public Information Officer
    (575) 835-7302
    dfinley@nrao.edu

    1
    Artist’s conception of a very young, still-forming brown dwarf, with a disk of material orbiting it, and jets of material ejected outward from the poles of the disk. CREDIT: Bill Saxton, NRAO/AUI/NSF

    Astronomers using the Karl G. Jansky Very Large Array (VLA) have discovered jets of material ejected by still-forming young brown dwarfs.

    NRAO VLA
    NRAO/VLA

    The discovery is the first direct evidence that brown dwarfs, intermediate in mass between stars and planets, are produced by a scaled-down version of the same process that produces stars.

    The astronomers studied a sample of still-forming brown dwarfs in a star-forming region some 450 light-years from Earth in the constellation Taurus, and found that four of them have the type of jets emitted by more-massive stars during their formation. The jets were detected by radio observations with the VLA. The scientists also observed the brown dwarfs with the Spitzer and Herschel space telescopes to confirm their status as very young objects.

    NASA Spitzer Telescope
    NASA/Spitzer

    ESA Herschel
    ESA/Herschel

    “This is the first time that such jets have been found coming from brown dwarfs at such an early stage of their formation, and shows that they form in a way similar to that of stars,” said Oscar Morata, of the Institute of Astronomy and Astrophysics of the Academia Sinica in Taiwan. “These are the lowest-mass objects that seem to form the same way as stars,” he added.

    Brown dwarfs are less massive than stars, but more massive than giant planets such as Jupiter. They have insufficient mass to produce the temperatures and pressures at their cores necessary to trigger the thermonuclear reactions that power “normal” stars. Theorists suggested in the 1960s that such objects should exist, but the first unambiguous discovery of one did not come until 1994.

    A key question has been whether brown dwarfs form like stars or like planets. Stars form when a giant cloud of gas and dust in interstellar space collapses gravitationally, accumulating mass. A disk of orbiting material forms around the young star, and eventually planets form from the material in that disk. In the early stages of star formation, jets of material are propelled outward from the poles of the disk. No such jets mark planet formation, however.

    Previous evidence strongly suggested that brown dwarfs shared the same formation mechanism as their larger siblings, but detecting the telltale jets is an important confirmation. Based on this discovery, “We conclude that the formation of brown dwarfs is a scaled-down version of the process that forms larger stars,” Morata said.

    Morata led an international team of astronomers with members from Asia, Europe, and Latin America. They reported their findings in the Astrophysical Journal.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 3:02 pm on May 7, 2015 Permalink | Reply
    Tags: , , , , NRAO VLA   

    From ALMA: “ALMA Discovers Proto Super Star Cluster — a Cosmic ‘Dinosaur Egg’ About to Hatch” 

    ESO ALMA Array
    ALMA

    07 May 2015
    Valeria Foncea
    Education and Public Outreach Officer
    Joint ALMA Observatory
    Santiago, Chile
    Tel: +56 2 467 6258
    Cell: +56 9 75871963
    Email: vfoncea@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 434.242.9559
    E-mail: cblue@nrao.edu

    Richard Hook
    Public Information Officer, ESO
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory Tokyo, Japan
    Tel: +81 422 34 3630
    E-mail: hiramatsu.masaaki@nao.ac.jp

    1
    The Antennae galaxies, shown in visible light in a Hubble image (upper image), were studied with ALMA, revealing extensive clouds of molecular gas (center right image). One cloud (bottom image) is incredibly dense and massive, yet apparently star free, suggesting it is the first example of a prenatal globular cluster ever identified. Credit: NASA/ESA Hubble, B. Whitmore (STScI); K. Johnson, U.Va.; ALMA (NRAO/ESO/NAOJ); B. Saxton (NRAO/AUI/NSF).

    NASA Hubble Telescope
    NASA/ESA Hubble

    NRAO VLA
    NRAO/VLA

    Globular clusters – dazzling agglomerations of up to a million ancient stars – are among the oldest objects in the universe. Though plentiful in and around many galaxies, newborn examples are vanishingly rare and the conditions necessary to create new ones have never been detected, until now.

    Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered what may be the first known example of a globular cluster about to be born: an incredibly massive, extremely dense, yet star-free cloud of molecular gas.

    “We may be witnessing one of the most ancient and extreme modes of star formation in the universe,” said Kelsey Johnson, an astronomer at the University of Virginia in Charlottesville and lead author on a paper accepted for publication in the Astrophysical Journal. “This remarkable object looks like it was plucked straight out of the very early universe. To discover something that has all the characteristics of a globular cluster, yet has not begun making stars, is like finding a dinosaur egg that’s about to hatch.”

    This object, which the astronomers playfully refer to as the “Firecracker,” is located approximately 50 million light-years away from Earth nestled inside a famous pair of interacting galaxies (NGC 4038 and NGC 4039), which are collectively known as the Antennae galaxies. The tidal forces generated by their ongoing merger are triggering star formation on a colossal scale, much of it occurring inside dense clusters.

    2
    NGC 4038 (left) and NGC 4039 (right)

    What makes the Firecracker unique, however, is its extraordinary mass, comparatively small size, and apparent lack of stars.

    All other globular cluster analogues astronomers have observed to date are already brimming with stars. The heat and radiation from these stars have therefore altered the surrounding environment considerably, erasing any evidence of its colder, quieter beginnings.

    2
    ALMA image of dense cores of molecular gas in the Antennae galaxies. The round yellow object near the center may be the first prenatal example of a globular cluster ever identified. It is surrounded by a giant molecular cloud. Credit: K. Johnson, U.Va.; ALMA (NRAO/ESO/NAOJ).

    With ALMA, the astronomers were able to find and study in detail a pristine example of such an object before stars forever change its unique characteristics. This afforded astronomers a first-ever glimpse of the conditions that may have led to the formation of many, if not all globular clusters.

    “Until now, clouds with this potential have only been seen as teenagers, after star formation had begun,” said Johnson. “That meant that the nursery had already been disturbed. To understand how a globular cluster forms, you need to see its true beginnings.”

    Most globular clusters formed during a veritable “baby boom” around 12 billion years ago, at a time when galaxies first assembled. Each contains as many as a million densely packed “second generation” stars — stars with conspicuously low concentrations of heavy metals, indicating they formed very early in the history of the universe. Our own Milky Way is known to have at least 150 such clusters, though it may have many more.

    Throughout the universe, star clusters of various sizes are still forming to this day. It’s possible, though increasingly rare, that the largest and densest of these will go on to become globular clusters.

    “The survival rate for a massive young star cluster to remain intact is very low – around one percent,” said Johnson. “Various external and internal forces pull these objects apart, either forming open clusters like the Pleiades or completely disintegrating to become part of a galaxy’s halo.”

    The astronomers believe, however, that the object they observed with ALMA, which contains 50 million times the mass of the Sun in molecular gas, is sufficiently dense that it has a good chance of being one of the lucky ones.


    Animation of ALMA data depicting dense cores of molecular gas in the Antennae galaxies. The yellow object at the center may be the first prenatal example of a globular cluster ever identified. Credit: K. Johnson, U.Va.; ALMA (NRAO/ESO/NAOJ)

    Globular clusters evolve out of their embryonic, star-free stage very rapidly — in as little as one million years. This means the object discovered by ALMA is undergoing a very special phase of its life, offering astronomers a unique opportunity to study a major component of the early universe.

    The ALMA data also indicate that the Firecracker cloud is under extreme pressure – approximately 10,000 times greater than typical interstellar pressures. This supports previous theories that high pressures are required to form globular clusters.

    In exploring the Antennae, Johnson and her colleagues observed the faint emission from carbon monoxide molecules, which allowed them to image and characterize individual clouds of dust and gas. The lack of any appreciable thermal emission – the telltale signal given off by gas heated by nearby stars – confirms that this newly discovered object is still in its pristine, unaltered state.

    Further studies with ALMA may reveal additional examples of proto super star clusters in the Antennae galaxies and other interacting galaxies, shedding light on the origins of these ancient objects and the role they play in galactic evolution.

    More Information

    The paper The Physical Conditions in a Pre Super Star Cluster Molecular Cloud in the Antennae Galaxies by K.E. Johnson et.al it can be found here.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small

    ESO 50

    NAOJ

     
  • richardmitnick 2:24 pm on April 27, 2015 Permalink | Reply
    Tags: , , NRAO VLA   

    From NRAO: “Strange Supernova is “Missing Link” in Gamma-Ray Burst Connection” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    27 April 2015
    Dave Finley, Public Information Officer
    (575) 835-7302
    dfinley@nrao.edu

    1
    In an ordinary core-collapse supernova with no “central engine,” ejected material expands outward nearly spherically, left. At right, a strong central engine propels jets of material at nearly the speed of light and generates a gamma-ray burst (GRB). The center panel shows an intermediate supernova like SN 2012ap, with a weak central engine, weak jets, and no GRB.
    CREDIT: Bill Saxton, NRAO/AUI/NSF

    Astronomers using the National Science Foundation’s Very Large Array (VLA) have found a long-sought “missing link” between supernova explosions that generate gamma-ray bursts (GRBs) and those that don’t.

    NRAO VLA
    NRAO VLA

    The scientists found that a stellar explosion seen in 2012 has many characteristics expected of one that generates a powerful burst of gamma rays, yet no such burst occurred.

    “This is a striking result that provides a key insight about the mechanism underlying these explosions,” said Sayan Chakraborti, of the Harvard-Smithsonian Center for Astrophysics (CfA). “This object fills in a gap between GRBs and other supernovae of this type, showing us that a wide range of activity is possible in such blasts,” he added.

    The object, called Supernova 2012ap (SN 2012ap) is what astronomers term a core-collapse supernova [Type II]. This type of blast occurs when the nuclear fusion reactions at the core of a very massive star no longer can provide the energy needed to hold up the core against the weight of the outer parts of the star. The core then collapses catastrophically into a superdense neutron star or a black hole. The rest of the star’s material is blasted into space in a supernova explosion.

    The most common type of such a supernova blasts the star’s material outward in a nearly-spherical bubble that expands rapidly, but at speeds far less than that of light. These explosions produce no burst of gamma rays.

    In a small percentage of cases, the infalling material is drawn into a short-lived swirling disk surrounding the new neutron star or black hole. This accretion disk generates jets of material that move outward from the disk’s poles at speeds approaching that of light. This combination of a swirling disk and its jets is called an “engine,” and this type of explosion produces gamma-ray bursts.

    The new research shows, however, that not all “engine-driven” supernova explosions produce gamma-ray bursts.

    “This supernova had jets moving at nearly the speed of light, and those jets were quickly slowed down, just like the jets we see in gamma-ray bursts,” said Alicia Soderberg, also of CfA.

    An earlier supernova seen in 2009 also had fast jets, but its jets expanded freely, without experiencing the slowdown characteristic of those that generate gamma-ray bursts. The free expansion of the 2009 object, the scientists said, is more like what is seen in supernova explosions with no engine, and probably indicates that its jet contained a large percentage of heavy particles, as opposed to the lighter particles in gamma-ray-burst jets. The heavy particles more easily make their way through the material surrounding the star.

    “What we see is that there is a wide diversity in the engines in this type of supernova explosion,” Chakraborti said. “Those with strong engines and lighter particles produce gamma-ray bursts, and those with weaker engines and heavier particles don’t,” he added.

    “This object shows that the nature of the engine plays a central role in determining the characteristics of this type of supernova explosion,” Soderberg said.

    Chakraborti and Soderberg worked with an international team of scientists from five continents. In addition to the VLA, they also used data from the Giant Meterwave Radio Telescope (GMRT) in India and the InterPlanetary Network (IPN) of spacecraft equipped with GRB detectors. The team, led by Chakraborti, is reporting their work in a paper accepted to the Astrophysical Journal. Other articles, led by co-authors Raffaella Margutti and Dan Milisavljevic, also report on the X-ray and optical follow-up on SN 2012ap using a suite of space and ground-based facilities.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
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