Transcript Beyond the Frontiers: The Road From Arecibo to (RSST)

Beyond the Frontiers:
The Road From Arecibo to
The Radio Synoptic Survey Telescope
(RSST)
Steven T. Myers
National Radio Astronomy Observatory
Socorro, NM
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What is the RSST?
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The Radio Synoptic Survey Telescope
• The RSST concept is for a “SKA-mid” facility
– see “Chicago 3” meeting later this week
• Primary Science Goals
– Cosmological HI Large Deep Survey (CHILDS)
• billion galaxies to z~1.5 (and beyond)
• redshift survey
• galaxy evolution
– Deep Continuum Survey (DeCoS)
• radio photometric and polarimetric survey
– Transient Monitoring Survey (TraMS)
• commensal with other RSST surveys
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What is the RSST?
• Radio?
– core frequency range 0.4-1.4 GHz (z<2.5)
• A Square Kilometer Array
– square kilometer of something (effective area?)
– high gain/low noise A/Tsys ≈ 2×104 m2 K-1
• don’t throw away all that collecting area!
– wide field-of-view, target 1 square degree
– “Areal Product” AW ≈ 106 m2 deg2 (at 1.4 GHz)
• A Survey Telescope
– cover large areas of sky 104 deg2 = ¼ sky
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The Synoptic Part
• Revisit the sky regularly
– if you want to cover 104 deg2 with 1deg2 FOV
– can do so in 1 day with 2-8s per point
– different parts of survey can have different
depths (and thus cadences)
• What cadence? Depends on the science
– many short visits or fewer longer ones?
– looking for individual “bursts” or “pulses”?
– looking for groups or trains of pulses?
– classical variability curves (e.g. microlensing)?
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Arecibo as
a RSST Precursor
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Numerology
• What about that AW thing?
– Arecibo 90 m2 deg2 (single beam at 1.4 GHz)
– vs. EVLA 2300 m2 deg2 (25x better but *)
• But, if A~naD2 and W~nb(l/D)2
– AW ~ nanb
– all single dishes the same for single feed
– AO single beam 27x worse than EVLA
• Arecibo must multibeam, the more the better
– bigger array (LNSD) or camera (Megapix) wins!
– SKA ~ 104 beams × elements = 10 Megapix
* EVLA has limited frequency coverage below 1GHz, and “starts” in 2010
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Perspective: Figures of Merit at 1.4GHz
• Areal Product
– SKA: AW ≈ 106 m2 deg2
• Area/Tsys
– SKA: A/Tsys ≈ 2×104 m2 K-1
• Survey Speed
– SKA: W(A/Tsys)2Dn ≈ 3×1017 deg2 m4 K-2 Hz-1
– product of AW and A/T and Dn/T
• Upshot for surveys:
– AO and EVLA equivalent for 7 beams (ALFA)
• 0.002% of SKA
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Focus for Arecibo? My take …
• Must have large multibeam “camera”
– ALFA 7x, ALFA++ 40, can we get 100?
• Should focus on interesting targets
– make every beam count!
– smaller surveys, like Virgo or galactic regions
– hit targets matched to camera footprint
– can be commensal with other observations
• Sensitivity = Thresholding
– Arecibo has 0.03 square km eff. area (11 K/Jy)
– can go deeply if interesting stuff in beam
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What Arecibo Provides
• Highest Instantaneous Sensitivity per beam
– allows detection of faint phenomena
– sets threshold for transient detections
– sets depth of “survey” in pointing: d ~ A½
• Arecibo depth 17% of SKA! Not too shabby!
• Some key thresholds
– see Cordes et al. SKA ScienceBook paper
• mostly continuum phenomena (possibly dispersed)
• 10mJy-1Jy (ALFA 3Jy SEFD ~ 0.17 mJy in 1s)
• e.g. Crab giant pulses d ~ 1.6Mpc (A/AAO)½
– also HI threshold (see this afternoon session)
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Summary: Arecibo as a Precursor
• Arecibo can be profitably used to pioneer
SKA science
– but need to target key projects and objects
• Science it would be good to know…
– giant pulsar pulses in nearby galaxies
– radio bursts from extrasolar planets
– HI galaxy mass function and bias
– add to list from other talks at this meeting!
• These provide critical informed input to
design of next generation projects
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RSST Roadmap
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What really needs to happen
• Need to write a White Paper for DR
– assemble small “blue team” to write the case
– need punchy science case
– remaining technical development?
– need “Phase A” level costing
– put in front of “red team” next year
– present to Decadal Review
• How does AO fit into the next decade?
– Arecibo “White Paper” for DR?
– need science output throughout decade
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For more information…
• RSST White Paper (draft)
– on this conference website:
http://www.naic.edu/~astro/frontiers/RSST-Whitepaper-20070910.txt
• SKA Info
– http://www.skatelescope.org
– particularly see the “Science Book”
• “The Dynamic Radio Sky” by Cordes, Lazio &
McLaughlin
• “Galaxy Evolution, Cosmology, and Dark Energy with
the SKA” by Rawlings et al.
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