Interferometry: now, promise &
future
S. R. Kulkarni
California Institute of Technology
The Really Big Picture
• “You do not understand anything unless you can
measure it precisely” (Lord Kelvin)
• Eventually mature fields demand precise and
accurate measurements
– eg. CMBR: discovery, wilderness, real understanding
– eg. Extra-solar planets: speculation, pulsars timing,
precision RV
– eg. Nuclear Black holes: Galactic center, OH
Megamasers+VLBA
The Promise
• Stellar Astronomy (all areas)
– Birth of stars (e.g. magnetospheric radius)
– Physics of stars at the 1% level
• This will require improvements across board (opacity, 3-D
convection, B fields, rotation)
• Black Hole Astrophysics
– Nuclear Black holes
– Galactic Center
• Dynamics
– Star clusters
– Gloublar clusters
– Milky Way Halo
Nearby Galaxies as Laboratories
The high angular resolution of a sensitive
interferometer could potentially make
nearby galaxies to be studied in great detail
eg. VLA transformed the study of HI from a
purely Galactic field to a major area of research
Such a step is not only a natural evolutionary step
in how our field will progress but is needed for
a quantitative understanding of the evolution of
the Universe
The Scene & the Competition
• The two major players by sheer virtue of geometry
are
– VLTI
– Keck Observatory + Mauna Kea telescopes
• Subaru, Gemini-N, Gemini-S, HET, SALT,
Magellan, GCT, MMT have no future in this area.
• LBT has a unique niche and my prediction is that
their best science will come out of of their
adaptive secondary related science and their
interferometry and not the use of LBT as a pair of
single telescopes.
Keck Interferometry: Based
around Key Projects
•
•
•
•
KI Nulling (exozodi of nearby stars)
KI differential phase (hot Jupiters)
KIA imaging (broad science, PMS)
KOA astrometry (outer planets)
ESO VLTI - the competition
Four 8-m telescopes (=16-m)
Four Auxillary 1.8-m Telescopes
200-m baseline array
MIDI (mid-IR beam combiner)
AMBER (near IR beam combiner)
PRIMA (Phase referencing)
GENIE (ESA Nuller)
Keck: Possible New Areas of
Thrusts
•
•
•
•
Fizeau imager for outriggers
Polarimetric beam combiner (disks)
FTS mode
High Sensitivity interferometer (AO on
outriggers and lasers)
• Push to optical wavelengths
OHANA -- Truly Unique
• Combine major telescopes on Mauna Kea
• 800-m baseline
• Large collecting area
– Analogy: radio astronomers are already on to
such an approach (global fringe fitting)
Now the ground reality
• Interferometry as a subject is lacking a
vigorous feeder pipeline
– Equivalent to having only 10-m telescopes with
no access to smaller telescopes
This is a a very serious problem.
• Sensitivity has been limited (but dual star
mode has overcome this).
– Early days of AO
An example: PHASES
• We have now demonstrated 20
microarcsecond *accuracy* for speckle
binaries (Lane & Mutterspaugh, PTI)
• We have now embarked on the Phases
project at PTI
• Do some aspect of SIM science -microarcsecond precision -- within 3 years
(by doing Phases at Keck)!!
Very Narrow Angle Astrometry
Shao & Colavita
Scanning the Fringe
Lane & Mutterspaugh
PHASES Observations
Multiple Targets
The PHASES Sample
What next?
• We are on the verge (finally) of great progress in
the field.
– Need serious thoughts but need visionary thinking
• Interferometry is an area where we can excel due
to investment and happenstance
• Identify whether interferometry has a role in
CELT/TMT.
• Need a major philosophical rethinking on part of
our community