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Astrometric Surveys in the
Next Decade
Dave Monet
U.S. Naval Observatory Flagstaff Station
June 15, 2011
Presumptions
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Currently operational:
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Will happen:
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Pan-STARRS – 100,000 exposures taken so far.
SkyMapper – operational after fix of telescope shake issues.
Kepler – Q8 on ground.
UKIDSS, etc.
Gaia – Current launch date is May 2013 – see poster.
J-MAPS – Current launch date is July 2014.
LSST – PDR in Aug 2011, inclusion in FY14 Federal budget?
No change in resource limitations (NSF, NASA, etc).
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No more Congressional earmarks.
Relevant Equations
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Accuracy = FWHM / SNR
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Velocity = 5 × motion × distance
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Limited by seeing on the ground – F(exposure time, site, etc.).
Limited by ? in space – TBD from Gaia, Kepler, etc.
km/sec, arcsec/year, parsec.
km/sec, mas/year, kpc.
Parallax = 1 / distance
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arcsec, parsec.
mas, kpc.
Quick Summary of Gaia
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Gaia will work as advertised:
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http://www.star.le.ac.uk/great_workshop/talks/Jordan_talk.pdf
1e9 stars with amazingly good astrometry + photometry.
Gaia catalog will be the 600-lb gorilla in the room:
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Guess: G2020 will replace J2000.
Guess: gu, gg, gr, gi, gz bands will replace SDSS as reference.
Guess: Intermediate catalog (mas; 2015?) changes everything.
• Will put USNO astrometry+catalogs out of business.
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For those of us who are not part of Gaia:
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Guess: Final catalog will be last astrometry catalog for decades.
How do we Gaia-proof our products?
How do we Gaia-proof our careers?
Resistance (to Gaia) is futile!
Quick Summary of LSST
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LSST astrometry is almost Gaia-proof:
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Cross-over magnitude where LSST becomes more accurate.
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Cross-over crowding:
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Gaia runs out of photons and bandwidth.
Guess: about 19th depending on CR damage to Gaia CCDs.
Bright stars will give rigid tie between LSST and Gaia.
Faint stars (down to 26th and beyond) will deliver the new science.
Gaia has 2 fields of regard in same focal plane.
At some star density, confusion will degrade accuracy.
LSST has bigger images but a single field of regard.
LSST can do difference imaging and analysis.
LSST is not all-sky.
• Did somebody mention “resources”?
• Can we learn “enough” from PS?
Impact - 1
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Pan-STARRS PS1 and SkyMapper need to hurry!
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Huge amount of astrometry to be done:
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My poster child is finding star that killed dinosaurs.
Parallax of every star in sky.
Survey of proper motions from large to small.
Learn large database astrometry by doing it.
Learn how to do crowded field astrometry.
Amazing opportunities in -30≤δ≤0 overlap zone.
Huge impact on most other astronomical disciplines.
But – Game Over! when Gaia publishes Intermediate catalog.
• Anticipate mas astrometry, mmag photometry over all sky.
• Guess: Release is politically and scientifically important.
• Guess: As early as is reasonable – 2015 or 2016.
Impact - 2
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No need for all-sky (RA,Dec) block adjustment solution.
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What is science driver between now and first Gaia release?
• Only one I know is solar system orbits – fixed USNO-B seems OK.
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Gaia Intermediate catalog will blow all of this away.
Concentrate on really cool new results:
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We don’t need μas astrometry for stars within 100pc.
• Parallax solutions possible after first year of survey.
• PS1 is ready to rock ‘n roll! SkyMapper is almost ready to go!
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Is there a population of fast/red/faint stars that Luyten missed?
• 50 mas/year should be like shooting fish in a barrel.
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Galactic plane is pretty much unsurveyed – can we do it now?
• Learn how to do differential image astrometry.
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Work on Gaia-proof (faint, really red, crowded) topics.
PS1 Status in May 2011 – 77,619 3π exposures
Don’t Forget About Kepler
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AΩ (etendue) is about 100.
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Example of cadence optimized for time not space.
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Same sky every 15 minutes for 3.5 (or more) years.
Experiment optimized for high SNR:
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Larger than anything other than LSST.
CDPP is 20 parts per million (= 20 μmag) every 6 hours.
Astrometry well beyond 0.001 pixel.
Really cool astrophysics:
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So much more than finding planets.
Asteroseismology – study cores of stars in detail.
Variable stars, eclipsing binary, planetary weather, etc.
Q0 and Q1 public now, Q2 (maybe more) in September 2011.
-0.01
Pixel
+0.01
Residuals after Affine transformation
Sample of 11 known giants on Channel 50 in Q5
Conclusions - 1
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Given astrometry, how to follow up neat stuff?
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Example – Kepler has totally saturated RV assets.
How can we possibly follow up PS1, SkyMapper, Gaia, LSST?
• Prepare for success, not failure.
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Data fusion?
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How do we do V&V on 1e10 objects?
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Astrometry is just an enabling technique.
Practice on PS and SkyMapper before deluge from Gaia, LSST.
Real opportunities in -30≤δ≤0 PS1+SM overlap zone.
Our colleagues might actually believe values in the database.
Cadence is everything!
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The Cadence Wars are coming.
Each science collaboration needs to be prepared.
Conclusions - 2
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Current ground-based optical astrometry programs are toast.
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Throw us to the sharks to please managers?
• “Turn things OFF!” is their mantra.
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Close facilities like USNO? (or maybe !)
Fire astrometrists as being obsolete.
Game over!
New imaging surveys should have astrometric “self follow up”.
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You put us out of business.
No other facilities that can do this.
Even if you are targeting galaxies or gravity, stars get in the way.
• Astrometry is nothing more than FWHM/SNR.
• Please think about it as part of the survey strategy.