Scalable cm-Wavelength Aperture Arrays Steve Ellingson, Virginia Tech Dunc Lorimer, West Virginia Univ. U.S. Radio/Millimeter/Submillimeter Science Futures II Baltimore MD Aug 4, 2016

Instrument & Science Fast radio bursts (FRBs) Pulsars Localization & survey Monitor for repeating FRBs Learn how to exploit FRBs as probes of the IGM Pulsars Spin-down monitoring Giant pulses Other science in which time on sky is more useful than sensitivity Small L-band aperture arrays (“tiles”) Lots of wide beams Long baselines  Localization Initially small collecting area, but scalable U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

Fast Radio Bursts (FRBs) – 1-Slide Primer Brief (~ms), dispersed (probably extragalactic), bright (~Jy) in L-band 17+ detected by 3+ instruments ~4400/sky/day Could be: Compact object mergers, anomalous NS behaviors, Cosmic strings, … But one (so far) repeats U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

Fast Radio Bursts (FRBs) – Science & Requirements Localization Need < 2’’ for confidence in an association at z=1 Need more (1000s) Understand the population(s) Find the anomalous cases Find repeating FRBs Need multiwavelength detections Co-observe with instruments in other wavebands To-Do List Interferometry 20 km @ 1.4 GHz Instrument Requirements The Science What are they? Guaranteed to be interesting Applications: Probe the IGM Baryon consensus Cosmic magnetism Photon mass constraints Very high duty cycle (time on sky) Need to steer (purely commensal mode not OK) Then maximize sensitivity U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

Taking Stock of Existing Instruments Suggests: O(10 m) apertures Lots of beams Spread out over 10s of km for localization Incoherently combined to maintain FOV Then lots of them, for sensitivity Given plausible Tsys & BW specs, productive searching is possible with just a few such apertures  scalability 4' 7 beams 7º 1 beam 14' 13 beams ~2-50'' ~0.5-16' LAS Productive Searching Typical FRB flux, Typical Tsys & BW, Increasing dish size U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

Large Array of Small Arrays (LASA) – “Tile” Conservative Specs: 1200-1700 MHz tuning range Ae ~ 3 m2 TR ~ 70 K (Tsys < 100 K) 16 dual-pol beams (8, 32) FWHM 6.3° (1.45 GHz, zenith) Z < 30° (> 30° with degradation) 100 MHz BW (50, 200 MHz) US$50K 1700 W U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

LASA – System Equiv. dish: 3-m 9-m 34-m x 16 (eap=0.5, Tsys=30 K) # tiles 3 32 512 Ae/Tsys [m2/K] 0.09 0.96 15.36 POP Cost [USD] 200K 2M 30M Long Baselines Equiv. dish: 3-m 9-m 34-m x 16 (eap=0.5, Tsys=30 K) U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

Performance of Relative Performance for FRB Survey CHIME: UTMOST: LASA-512, 32 beams beams CHIME: 400-800 MHz 14’ (no loco.) UTMOST: 843 MHz 20’’ (coarse loco.) VLA (Realfast) L-Band < 2” in A config Low availability Low time resolution (5 ms) AO, GBT, Parkes All: Respect! LASA-512, 8 beams LASA-32, 32 beams LASA-32, 8 beams LASA-3, 32 beams Parkes (100% duty cycle) LASA-3, 8 beams VLA (Realfast) (100% duty cycle) (@ actual duty cycle) U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

16 Beams that Don’t Have to be Pointed in any Particular Direction … What Else Can Be Done? Transient science that can’t be done by any other instrument Monitor coordinates of all known FRBs to check for repeaters Follow instruments in same and other bands … co-detections Triggering by other instruments – phased arrays can be repointed quickly Generally: Projects in which time on sky is more useful than maximizing sensitivity Giant pulse surveys – productive even with LASA-3 Monitor spin-down of normal bright pulsars: Better understanding of timing noise processes – productive even with LASA-3 SETI Your project here? U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016

Concluding Remarks LASA-3, 16 beams, ~US$1M yields a productive FRB instrument + other interesting science LASA-32, 16 beams, ~US$3M yields a front-line FRB instrument + other interesting science No “technology development” (only “design”) required - not even the antenna array (tile) Wait a minute… isn’t this SKA2 AA-MID? NO. Very modest requirements  Much smaller, simpler instrument BUT: Definitely potential two-way synergy that would be useful to pursue Effort underway to get this started; inquiries & collaborators welcome! U.S. Radio/Millimeter/Submillimeter Science Futures II, Baltimore, MD, Aug 4, 2016