Inspired by dramatic discoveries from the Jansky VLA and ALMA, the astronomy community has initiated discussion of a future large area radio array optimized for imaging of thermal emission to milli-arcsecond (mas) scales that will open new discovery space from proto-planetary disks to distant galaxies.
This Next Generation Very Large Array (ngVLA) is currently envisioned to include:
- 10x the collecting area of the Jansky VLA & ALMA
- science operations from 1.2 – 116 GHz
- 10x longer baselines (300 km) that yield mas-resolution, and
- a dense antenna core on km-scales for low surface brightness imaging.
There has been rapid progress in the ngVLA science case and technical requirements over the past two years though a number of NRAO-sponsored community workshops.
As we continue to build towards a final vision for the ngVLA, we invite the entire astronomical community to become involved by signing up for the ngVLA mailing list, participation in upcoming conferences and workshops, as a member of the Science and/or Technical Advisory Council, as well as through our community-driven design studies program.
An ngVLA will have broad impact on many of the high priority goals of modern astronomy and astrophysics, including the science priorities described in the New Worlds, New Horizons Astro2010 Decadal Survey. The ngVLA Science Working Groups are identifying a number of key science programs that push the requirements of the telescope. If you are interested in joining one of the Science Working Groups, please contact Chris Carilli or Eric Murphy. An initial set of science goals suggested by the four Science Working Groups are described in white papers published in the ngVLA memo series.
As examples, three compelling science goals that require an ngVLA are briefly described below. The Science Working Groups are continuing to expand their science programs through realistic simulations, and a corresponding science workshop highlighting their findings will be held in 2017.
The inner regions of protoplanetary disks are optically thick at shorter wavelengths. The ngVLA will image gap-structures indicating planet formation on solar system scales, determine the growth of grains, and image accretion onto porto-planets themselves. Probing dust gaps on 1 AU scales in the nearest major star-forming regions requires baselines 10x the Jansky VLA baselines, with a sensitivity adequate to achieve a few K brightness at 1 cm wavelength and 9 mas resolution.
The ngVLA covers the spectral range richest in the ground state transitions of the most important molecules in astrochemistry and astrobiology, as well as key thermal and non-thermal continuum emission processes related to star formation. The ngVLA will perform wide field imaging of line and continuum emission on scales from GMCs (100 pc) down to cores (few pc) in galaxies out to the Virgo Cluster, with an order of magnitude faster mapping speed than ALMA. A centrally condensed antenna distribution on scales of a few to 10 km is required for wide-field, high surface brightness sensitivity.
Octave bandwidth is required for large cosmic volume surveys of low order CO emission (the fundamental tracer of total gas mass) from distant galaxies, as well as for dense gas tracers such as HCN and HCO+. The spatial resolution and sensitivity will also be adequate to image the gas on sub-kph scales and detect molecular gas masses down to dwarf galaxies.
Community Studies Program
As part of the process of building towards a final concept for the ngVLA, NRAO has launched the ngVLA Community Studies program, allowing members of the scientific and engineering communities to become major contributors to this effort. With the help of the astronomical community over the past two years, NRAO has already taken a preliminary look at a number of scientific objectives and technical challenges that play major roles driving the telescope deign, yielding a range of suggested topics where community input is expected to be most constructive.
A list of the 25 approved scientific and technical studies are provided below, and will be carried out over the next year to help construct a final design concept to be brought to Astro2020. Information the proposal selection process can be found in the call for proposals. Supporting materials for the ngVLA Community Studies, such as notional receiver and array configuration files, can be found on the scientific and technical documents page.
ngVLA Community Studies are expected to:
- Demonstrate the major scientific/technical advancement being advocated and put it in context for the broader astronomical community.
- State clearly the impact on design choices.
- Ultimately produce a publication in a peer-refereed journal, or at minimum in the ngVLA memo series.
All accepted Community Studies efforts are expected to write up their findings as part of a peer-refereed journal article or ngVLA memo, and present their progress/final results at the ngVLA science meeting to be held in June 2017. Consequently, NRAO will financially support each study at modest level to offset travel expenses to present results at the mid-2017 ngVLA Science Conference, as well as for page charges from publications expected to result from the study. For 10 of the accepted proposals, NRAO is able to provide funding at a more significant level.
Approved Science Studies
|PI (Affiliation)||Proposal Title|
|Geoffrey Bower (ASIAA)||Galactic Center Pulsars with the ngVLA|
|Caitlin Casey (University of Texas at Austin)*||Cold Gas in the Early Universe|
|Shami Chatterjee (Cornell University)*||A NANOGrav Study of Gravitational Wave Astronomy with the ngVLA|
|Alessandra Corsi (Texas Tech University)*||Cosmic Explosions and Collisions in the ngVLA Era|
|Andrea Isella (Rice University)*||Imaging Planet Formation with the ngVLA|
|Garrett Keating (SAO)||Exploring the Cosmic History of Molecular Gas with Intensity Mapping|
|Adam Leroy (Ohio State University)||Assessing the Suitability of Proposed ngVLA Designs for Surface Brightness Science|
|Brett McGuire (NRAO)||The Detectability of Interstellar Molecules with the ngVLA|
|Kristina Nyland (NRAO)||Revolutionizing Radio AGN Science with the ngVLA|
|Rachel Osten (STScI & JHU)*||Quantifying the ngVLA's Contribution to Exo-Space Weather|
|Jorge Pineda (JPL)||Composition of the Interstellar Medium|
|Vikram Ravi (Caltech)*||Centimeter-Wavelength Observations of Compact-Object Cataclysms|
|Karen Willacy (JPL)||Protoplanetary Disk Chemistry as a Probe of Planet Formation|
Approved Technical Studies
|PI (Affiliation)||Proposal Title|
|Roger Angel (University of Arizona; REhnu, Inc.)||A New Approach to Inexpensive Radio Dishes|
|Joe Campbell (UVa)*||High-Power, High-Speed Photodiodes|
|Larry D'Addario (Caltech/JPL)||Advanced Cryocooling Technologies|
|Matt Fleming (Minex Engineering Corp.)*||Proposal for Antenna Mount Study|
|David Frayer (GBO)||Short Spacing Requirements for the ngVLA|
|Brian Jeffs (BYU)*||Advanced Spatial Filtering Methods for RFI Mitigation at the ngVLA|
|Jeroen Koelemeij (LaserLaB and VU Amsterdam)||Sub-Nanosecond Time Accuracy and Frequency Distribution through White Rabbit Ethernet|
|Dean Chalmers (NRC Herzberg)||Offset Gregorian Antenna|
|Lewis Knee (NRC Herzberg)||ngVLA Receivers|
|Michael Rupen (NRC Herzberg)||The Scientific Drivers and Technical Requirements for the ngVLA Correlator|
|Stefano Spagna (Quantum Design Inc.)*||Smart Energy Cryocooler Technology for the ngVLA|
|Greg Taylor (UNM)||Exploring Low Frequency Options for the ngVLA: Providing a Path to a Next Generation LOw Band Observatory (ngLOBO)|
|David Woody (Caltech/Owens Valley Radio Observatory)||Impact of Fast Switching on Telescope Design|
Science Working Groups
The high resolution and sensitivity of the ngVLA in the 1-100 GHz frequency regime would pave the way for revolutionary new science in the fields of star and planet formation. Major science drivers include: (1) low-mass, embedded objects, where the longer wavelengths will allow us both to probe disk properties extremely close to the parent protostar and to reveal binaries and multiplicity out to much larger distances in our galaxy; (2) high-mass star formation, where the high sensitivity will allow us to resolve the density structure and dynamics of the youngest HII regions and high-mass protostellar jets; (3) protoplanetary disks, where the longer wavelengths and the unprecedented angular resolution will allow us to map planet forming regions around young stars and investigate the evolution of dust grains; (4) planetary science, where the unprecedented sensitivity will allow deep mapping of planetary atmosphere on very short time scales; and (5) SETI (Search for Extraterrestrial Intelligence), where the vast frequency and sky coverage of the ngVLA, coupled with improved targeting information from space missions such as GAIA and TESS, would bring the search for life outside of our own solar system into a new era.
The ngVLA would be a powerful tool to study the detailed astrophysics of star formation both within the Milky Way and nearby galaxies. With an unprecedented combination of high angular resolution and both line and continuum sensitivity, this revolutionary facility would: (1) provide new insight on the fundamental physics behind radio emission; (2) allow detailed spectroscopic characterization of the interstellar medium in all sorts of astronomical systems; (3) directly measure the ionizing photon rate of newly formed massive stars with the ability to penetrate through high columns of dust for extremely compact, embedded systems; (4) study dust physics by accessing the cold/massive dust component that powers the Raleigh-Jeans tail of dust spectral energy distributions; and (5) directly study the role of magnetic fields on the star formation process by increasingly pushing into the Faraday-thin regime where polarization observations should begin to probe deep into star forming regions. The combination of sensitivity and astrometric accuracy promised by the ngVLA would further allow studies of the motions around black holes and at the base of jets, measurements of proper motions in Local Group galaxies, and refinements to our knowledge of Galactic structure.
The combination of unique capabilities offered by a Next Generation VLA would enable great advances in studies of galaxy assemble over cosmic time. The sensitivity and frequency coverage would allow the detection of cool gas and dust in relatively 'normal' distant galaxies, including molecular gas tracers such as low-J CO, H20, HCN, and HCO+; synchrotron and free-free continuum emission; and even the exciting possibility of thermal emission at the highest (z ~ 7) redshifts. The ultra-wide bandwidths would allow a complete sampling of radio/submillimeter SEDs, as well as the simultaneous detection of multiple emission lines. Finally, the superb angular resolution would move us beyond detection experiments and allow detailed studies of the morphology and dynamics of these systems, such as dynamical modeling of disks/mergers, determining the properties of outflows, measuring black hole masses from gas disks, and resolving multiple AGN nuclei. Our working group will explore the contribution of a ngVLA to these areas and more, as well as synergies with current and upcoming facilities including ALMA, SKA, TMT/ELT, and JWST.
The ngVLA will provide powerful probes of the transient and high energy universe, revealing new physics. Millisecond pulsars orbiting Sgr A* have the potential to measure black hole mass and spin to unprecedented accuracy, as well as probe the fundamentals of general relativity. Electromagnetic counterparts to gravitational wave events provide a window into extreme physics of neutron star mergers. Tidal disruption of stars around massive black holes provides a unique laboratory for accretion-jet physics and explores the growth of black holes in galactic centers. The physics of plasmas, from the Sun to galaxy clusters, are also uniquely probed by this instrument.