Project Overview Eric Murphy, ngVLA Project Scientist

The Jansky Very Large Array 1972 – Approved by Congress 1975 – First Antenna in place 1980 – Full science operations 2001 – Complete electronics upgrade approved by NSF 2011 – Jansky VLA full science ops ~12,000 refereed papers with ~500,000 citations ~500 PhD theses The VLA has been among the most productive telescopes ever! Major recent science: FRB localization of completely unknown phenomena distance record for atomic H in emission Investigations of solar weather.

A next generation VLA Scientific Frontier: Thermal imaging at milli-arcsecond scale resolution Design Goals 10x effective collecting area of JVLA and ALMA 10x resolution of JVLA and ALMA Frequency range: 1.2 –116 GHz Located in Southwest U.S. (NM+TX+?) & Mexico, building from JVLA site Baseline design under development Low technical risk (reasonable step beyond current state of the art) https://science.nrao.edu/futures/ngvla Where we started… goals for the array. Really started previous DS (2010) with NAA

Radio Facilities in the 2030’s Complementary suite from cm to submm, appropriate for the mid-21st century < 0.3cm: ALMA 2030 superb for chemistry, dust, fine structure lines 0.3 to 3cm: ngVLA superb for terrestrial planet formation, dense gas history, baryon cycling > 3cm: SKA superb for pulsars, reionization, HI + continuum surveys

Radio Facilities in the 2030’s Complementary suite from cm to submm, appropriate for the mid-21st century < 0.3cm: ALMA 2030 superb for chemistry, dust, fine structure lines 0.3 to 3cm: ngVLA superb for terrestrial planet formation, dense gas history, baryon cycling > 3cm: SKA superb for pulsars, reionization, HI + continuum surveys

Radio Facilities in the 2030’s ngVLA Key Science Cases Complementary suite from cm to submm, appropriate for the mid-21st century < 0.3cm: ALMA 2030 superb for chemistry, dust, fine structure lines 0.3 to 3cm: ngVLA superb for terrestrial planet formation, dense gas history, baryon cycling > 3cm: SKA superb for pulsars, reionization, HI + continuum surveys Stars or key science drivers

Bridging SKA & ALMA Scientifically Thermal Imaging on mas Scales at λ ~ 0.3cm to 3cm 1AU @ 140pc Terrestrial zone planet formation Resolution ~ 10mas @ 1cm (300km) Synergy w. ALMA submm, future ELTs Complement to SKA low frequency capabilities Synergies with (ALMA) sub-mm, and (ELT’s) optical/NIR high-resolution science.

Highly Synergistic with Other Facilities on Similar Timescales SKA Atomic/non-thermal Molecular/thermal ALMA Warm/star-forming Cold/dense fuel for SF LUVOIR/HabEx Image earth-like planets Image terrestrial-zone planets forming OST (FIR surveyor) C/WNM & WIM Cold Molecular Medium TMT/GMT Stellar Mass and Unobscured SF Dense Gas and Obscured SF JWST Continuing its legacy in many areas of astrophysics All science Highly synergistic with next-generation ground-based OIR and NASA missions.

Developing the ngVLA Science Case Community-Driven, Growing, and Evolving Numerous Science and Technical meetings, starting from Jan 2015 AAS Initial Science Working Group reports covering 4 broad areas, Nov .2015 (http://library.nrao.edu/ngvla.shtml) Cradle of Life: CoL (Isella et al): Terrestrial-zone planet formation, Massive Stars, etc. Galaxy Ecosystems: GEco (Leroy et al): wide field, high resolution/sensitive imaging Galaxy Formation: GFor (Casey et al): Dense gas history of the Universe Time domain, Cosmology, and Physics: TdCP (Bower et al): Plasma physics, Exo-space weather, Strong Lensing 26 Community Design Studies in progress, partially funded by NRAO (https://science.nrao.edu/futures/ngvla/ngvla-community-studies-approved-programs) 75 Community-Led Science Use Cases Submitted for ‘Reqs to Specs’ process All gathered to report out and build toward a consensus vision last week of June in Socorro A community-driven ngVLA Science Case has been being built over past 2.5 years and includes: Really builds on NAA, which was submitted at previous DS2010 A number of science and technology workshops were held Initial set of science WPs covering 4 broad areas A (funded) community study program Science use-case capture (led by SAC) All gathered in Socorro in June to report out and discuss findings of science use case capture. Andrea will report on the resulting key science mission.

Community-Led Advisory Councils ngVLA Science Advisory Council ngVLA Technical Advisory Council Interface between the science community & NRAO Recent/Current Activities: Science working groups: science use cases  telescope requirements SOC for science meeting in June Lead Science case development  ‘science book’ & DS2020 White Papers Interface between the engineering & computing community and NRAO Membership covers a broad range of expertise in relevant technical areas including: Antennas, low-noise receiver systems, cryogenics, data transmission, correlators, and data processing Alberto Bolatto    (University of Maryland: co-Chair) Andrea Isella    (Rice University : co-Chair) Brenda Matthews    (NRC-Victoria: SWG1 Chair) Cornelia Lang    (University of Iowa: SWG2 Chair) Dominik Riechers (Cornell: SWG3 Chair) Joseph Lazio    (JPL: SWG4 Chair) James Lamb (Caltech : co-Chair) Melissa Soriano (JPL : co-Chair) ngVLA Project Office has been relying on input gathered by our two advisory councils. Will hear form both SAC and TAC co-charis later.

ngVLA Key Science Mission (ngVLA memo #19) Unveiling the Formation of Solar System Analogues Probing the Initial Conditions for Planetary Systems and Life with Astrochemistry Charting the Assembly, Structure, and Evolution of Galaxies Over Cosmic Time Using Pulsars in the Galactic Center as Fundamental Tests of Gravity Understanding the Formation and Evolution of Stellar and Supermassive BH’s Uncovering the Violent Sky in the Era of Multi-Messenger Astronomy Highly synergistic with next-generation ground-based OIR and NASA missions. ngVLA 100hr 25GHz 10mas rms = 90nJy/bm = 1K Jupiter @13AU Saturn @6AU Isella Dust Model 0.1” = 13AU Gas ALMA NGVLA Decarli+2016 HI + CO(1-0) CO(2-1)

Science Use Case Parameterization (ngVLA memo #18) 75 Science Use Cases developed into 180 discrete observations. Derived a number of parameters from each observation to determine what the community needs from this array. Andrea’s Talk will summarize the process/findings. All feedback was distilled and uniformly parametrized into a spreadsheet Large number of slices in paramter space (resolution, frequency, sensitivity, etc.) was looed at see talk posted online form meeting and ngVLA memo 18.

Significant Requirements & Take-Aways ngVLA 100hr 25GHz 10mas rms = 90nJy/bm = 1K Jupiter @13AU Saturn @6AU Isella Dust Model 0.1” = 13AU Significant Requirements & Take-Aways PI driven / pointed operations model. Need full 1.2 – 116 GHz Frequency coverage across the full array. Most science achievable with ~300 – 1000 km scale array, with a long tail extending out to VLBI scales. Gas ALMA NGVLA HI + CO(1-0) CO(2-1) Decarli+2016 Most importantly, we can’t predict how the intellectual curiosity of the community will drive this array, likely leading to a lot of exciting science that has not yet been captured.

Operating Modes / Functional Capabilities Spectral Line & Continuum Modes Time Domain Capabilities VLBI Capabilities Phased Array Capability Total Power Measurements Sub-Array Capabilities Solar Observation Capabilities Goal to maximize flexibility of both modes. Both equally represented. Time domain search capabilities on msec scales. Combine with other antennas out to continental scale baselines. Operate as both an interferometer and phased array. Need a solution to recover total flux. Flexible sub-array capability. Analog dynamic range for bright sources.

Requested Key Technical Parameters Frequency Range – 1.2 – 116GHz Requested Sensitivities @ 30 GHz Continuum Imaging Sensitivity – 0.08 uJy/bm Line Imaging Sensitivity – 10 uJy/bm/km/s Surface Brightness Sensitivity – 1 mK @ 1 arcsec Angular Resolution – < 10mas @ 30GHz Dynamic Range – <~105 Polarization – 0.1% Purity, 1-degree An artist’s rendering of the ngVLA core, centered on the current JVLA site, which may include ~85 of the ~214 18m diameter dishes that comprise the array. Dynamic range: 90% cases require DR < 40 dB 0.2 uJy/bm in 10hr => 100% of all driving science cases and ~80% of all science cases submitted.

Current Reference Design Specifications (ngVLA Memo #17) 214 18m offset Gregorian (feed-low) Antennas Supported by internal costing exercise Fixed antenna locations across NM, TX, MX ~1000 km baselines being explored 1.2 – 50.5 GHz; 70 – 116 GHz Single-pixel feeds 6 feeds / 2 dewar package Short-spacing/total power array under consideration Receiver Configuration Band # Dewar fL GHz fM GHz fH GHz fH: fL BW GHz 1 A 1.2 2.55 3.9 3.25 2.7 2 8.25 12.6 3.23 8.7 3 B 16.8 21.0 1.67 8.4 4 28.0 35.0 14.0 5 30.5 40.5 50.5 1.66 20.0 6 70.0 93.0 116 46.0 Continuum Sensitivity: ~0.1uJy/bm @ 1cm, 10mas, 10hr => TB ~ 1K Line sensitivity: ~20uJy @ 1cm/bm, 10 km/s, 1” => TB ~ 25mK - Where we ended up based on a very successful meeting in June in Socorro. - Registration was a oversubscribed. - Included breakout sessions of SWGs. - Settled on a reference design to focus on for DS2020.

Estimated Price Tag (Internal Preliminary Costing Exercise) Target construction baseline budget ~ (2016) $1.5B Target operations budget of < (2016) $75M (< 3x current VLA) Operations, maintenance, computing, archiving, etc.: optimize as part of design Partnerships Possible U.S. Multiagency Interest [including VLBI option] ICRF – DOD/Navy, Air Force Spacecraft tracking/imaging, `burst-telemetry’ (mission-critical events) – NASA, DOD Space situational awareness – DOD Strong International Partnership critical for success: Current International Involvement in SAC/TAC/Community Studies: Canada, Mexico, Japan, Germany, Netherlands, Taiwan Current Industrial Involvement through Community Studies: REhnu Inc., Minex Engineering Corp, LaserLaB, Quantum Design Anticipating “Open Skies” policy Is this SKA-High? Scientifically, the same direction.

Key Open Questions – Specification Decisions Recovering Large Scale Structure Is a 30m minimum spacing good enough? Large single dish w/ FPA (e.g., 45m x 20 beams – D. Frayer, ngVLA memo 14)? Short-spacing array of small dishes + TP mode (e.g., 6m – Murphy/Condon+, Sci. Case NGA-3)? Distribution of collecting area – sensitivity over a range of angular scales needed. Maximum baseline in the reference design. 300 – 500 km. Up to 1000 km? How far should we go with connected elements?

Science Options Commensal Low Frequency Science (Taylor & Kassim) Leverage ngVLA infrastructure (land/fiber/power) for commensal LF capabilities (ngLOBO) 5 – 150 MHz: multi-beam dipole arrays alongside ngVLA long-baseline stations (e.g., LWA style). 150 – 800 MHz commensal prime focus feeds on ngVLA antennas (e.g., VLITE style) U.S. VLBI Expansion of Capabilities (Brisken) Replace existing VLBI antennas/infrastructure with ngVLA technology Introduce new ~1000 km baseline stations to bridge gap between ngVLA & existing VLBA baselines Cross correlate VLBI antennas with phased ngVLA LWA: all sky w/ multiple beams

www.nrao.edu science.nrao.edu public.nrao.edu The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Band 6 Band 5 Band 4 Band 3 Band 2 Band 1 Band definitions purely illustrative at this point, not final. Definition of Color Coding: * Red: Drivers are key science cases currently identified by SAC as essential * Green: Science Cases that strongly support the key science drivers * Blue: The remaining science cases received Main takeaway – key science needs 1.2 - 116

Band 6 Band 5 Band 4 Band 3 Band 2 Band 1 30 km 300 km How does frequency request look as a function of requested resolution (max baseline) Conclusion – need both low and high frequency bands across the full angular scales supported by the array. * Implies outfitting all antennas with full suite of receivers.

80 nJy/bm Conclusion: sensitivity is a driving requirement! All Driving Science achieved with ~0.08 uJy/bm and 80% of all cases. ~100hr integration with current incarnation, pessimistically assuming factor of x2 above NA sensitivity => 25 hr with Natural Weighting. Stresses importance of imaging performance studies to improve weighting factors.

10 uJy/bm/km/s Conclusion: Cases are split roughly 52% continuum and 48% spectral line. Need demanding sensitivity for spectral line work too! Cannot sacrifice sensitivity at narrow bandwidths. Achieve 90% of science drivers w/ ~10 uJy/bm/km/s ~720hr integration with current incarnation, pessimistically assuming factor of x2 above NA sensitivity => 180hr with Natural Weighting. ~ Upside, other half of driving requirements needs ~80uJy/bm/km/s, so ~10hr integration

300 km 30 km 1" 1" 300 km 30 km Continuum and spectral line cases separated. Conclusion – need to get to ~ mK surface brightness sensitivity in the compact core of the array. (Can achieve 90% of all line and continuum science cases) Conclusion – need to get to ~ mK surface brightness sensitivity on ~1” angular scales in the compact core of the array. (Can achieve 80% of all science cases) -- one outlier is large scale HI emission.

30 km 300 km 100% of all major science drivers achieved with ~300 km baselines 80% of all science cases achieved within ~300 km baselines ~60% of all science drivers achieved within existing VLA footprint. Plot has structure – emphasis on 1-2km scale and 20-80 km scale. Noise or signal? Something to ponder in configuration design….