TMTAstrometry

Astrometry with the TMT: 

Astrometry with the TMT S. R. Kulkarni California Institute of Technology Interdisciplinary Scientist Space Interferometry Mission

“You understand something truly only when you can measure it precisely.” Lord Kelvin : 

“You understand something truly only when you can measure it precisely.” Lord Kelvin Confucius says “One excellent measurement is better than many mediocre measurements.”

Astrometry: 

Astrometry Wide angle [Requires an inertial grid (quasars)] Parallax Proper Motion of similar stars Narrow Angle [Requires suitably bright reference stars] Companions Proper Motion of dissimilar stars

Space Interferometry Mission PlanetQuest: 

Space Interferometry Mission PlanetQuest Global astrometry (5yr mission) 4 µas position (inertial) 2.5 µas/yr proper motion 4 µas parallax Narrow Angle Performance, 1 µas

Slide5: 

10 11 12 19 10 0 30 GAIA SIM 20 40 Milky Way Globular clusters Active Galactic Nuclei Radio Ref Frame 9 13 14 15 16 17 18 Magnitude Accuracy arcsec Nearby Galaxies Precision masses Wide Angle, end-of-mission limit performance SIM and GAIA – Wide Angle Astrometry Science Targets

Slide6: 

Magnitude Accuracy arcsec SIM and GAIA - Exo-Planet Detection Capability Young Planets

Golden Astrometry Decade: 

Golden Astrometry Decade SIM: Nonpareil in parallax and proper motion Fundamental astrophysics (Galactic distance scale) Dark Matter GAIA: Superb stellar astrometry machine TMT: Unique for read and faint objects Latch on to GAIA frame Dense fields Transients

Precision Astrometry: 

Precision Astrometry Thesis work of P. Brian Cameron

Bright Star Limit (NGS): 

Bright Star Limit (NGS) Cluster M5 at Palomar 1.4s exposures 600 images Differential offsets are elongated parallel to the displacement Offsets are correlated over the field

Differential Tilt: 

Differential Tilt Stars separated by some angle sample same turbulence at low altitudes In principle correction is exact only for guide star Thus error will grow with  Removing correlated differential tilts results in a fundamental limit for single guide star AO astrometry DT ~ 20 mas (/20”)(5m/D)6/7

Achieved precision: 

Achieved precision Resolving the differential tilt allows determination of the target star position to improve faster than 1/sqrt(N) The tilt jitter also averages away as 1/sqrt(t) Estimated precision of 50 microarcsecond in ~15 minutes of integration time Achieved 100 uas in ~2 min Future work will focus on longer intergrations Apparently stable for 2-min data for timescales of weeks

Magnetars: 

Magnetars Sources heavily extincted AV ~ 3-30 mag 4/6 magnetars visible to Keck have published faint NIR/optical counterparts. Kp ~ 19.5-22.5 mag Two possible new counterparts based on astrometry and variability. Kp~1 mag 1E 1841-045 Thesis work of P. Brian Cameron

Magnetar Proper Motions: 

Magnetar Proper Motions Proper motion limits show magnetars have relatively low velocities ~200-300 km/s Implies the population is older than previously thought Draws into question popular theories of magnetar formation. 9/2005 8/2006 10,12/2006 2005 2006 4U 0141+61 1E 2259+586

Very Narrow Angle Astrometry: 

Very Narrow Angle Astrometry

Slide17: 

PHASES: Demonstrated 20 microrcseconds precision See Lane, Muterspaugh et al.

Some Applications: 

Some Applications

Slide22: 

I. HST (WFPC2) Proper Motion of M4 Bedin et al.

Slide23: 

II. Proper Motions of Halo Objects Piatek et al. 2007 Fornax Proper Motion: 485, -365 mas/century (WFPC2, STIS)

Slide24: 

TMT Goals Measure the mass and location of the supermassive black hole in M31. Study the detailed kinematics of the eccentric disk of old stars. Understand the origin of the young stars. Study the mechanism for ejecting hypervelocity stars. Keck’s View LGS-AO imaging shows individual point sources at r > 2” and is confusion limited at r < 2” (7.6 pc). TMT View Measure proper motions in 1-3 years (3 sigma) with an astrometric precision of 0.03 mas. See poster by Jessica Lu, Andrea Ghez, & Keith Matthews III. M31 Nucleus

Slide25: 

Gaudi et al. IV. Halloween Transient in Cas

Slide27: 

Movie by Christopher Night (CfA) Rosanne di Stefano (CfA) Exciting Fly by Events

Rates relative to M-dwarfs: 

Rates relative to M-dwarfs R. Di Stefano

Why TMT?: 

Why TMT? Narrow angle astrometry (faint, red): Substellar binaries Rare binaries (black hole…) Nearby centers of galaxy (M31) Medium angle astrometry (crowded field) Globular Clusters Dwarf Spheroidals Wide angle astrometry (faint, red) Limited to GAIA precision Access to Sky for Transient Events Mesolensing events Transients