1 / 38

EXAOC SCIENCE MIDTERM MEETNG

This document provides an overview of direct imaging searches and specific science goals. It discusses the benefits of adaptive modal gain control, speckle suppression, and flat field noise. The document also covers thermal background analysis and the utility of high contrast imaging for various scientific applications.

pparks
Download Presentation

EXAOC SCIENCE MIDTERM MEETNG

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EXAOC SCIENCE MIDTERM MEETNG James Graham UC Berkeley HIA/DAO 21st October 2004

  2. SCIENCE TEAM • Adam Burrows, UofA • Eugene Chiang, UCB • Rene Doyon, UdM • Doug Johnstone, HIA • Paul Kalas, UCB • Bruce Macintosh, LLNL/UCSC • Franck Marchis, UCB • Geoff March, UCB • Ben Oppenheimer, AMNH • Jenny Patience, CIT • Inseok Song, Gemini • Yanqim Wu, UT

  3. CONTENTS • Science overview • Brief overview of direct imaging searches & specific science goals • Analysis • Benefits of adaptive modal gain control • Speckle suppression • Specifying form (vs. separation, spectrum) • Flat field noise • Detection threshold and application of the central limit theoremt to Rician stats • Thermal background analysis • Astrometry • Neptune at 30 pc moves 39 mas/yr • Young associations (N vs. S) • Requirements matrix • Draft OCDD

  4. HIGH CONTRAST SCIENCE GOALS • Imaging planets & planetary systems • Improved statistics (4–40 AU vs. 0.4–4 AU) • Sample beyond the snow line ( a > 3 AU, P > 5 yr) • Probe planetary atmospheres • Protoplanetary disks • Structure & evolution of dust & gas orbiting T Tauri & Herbig Ae/Be stars • Debris disks & zodi dust • Structure in inner disks where planets form & orbit • Disk/planet interactions • Brown dwarfs • Frequency of brown companions (e.g., HR 7672 & LHS 2397) • Mass loss from from evolved stars • Destruction of planetary systems while seeding the Galaxy for the next generation of solar systems

  5. UTILITY OF HIGH CONTRAST IMAGING • Broad scientific application • Exoplanet detection • Circumstellar disks (proto-planetary & debris disks) • Mass transfer & loss in cataclysmic variables, symbiotic stars, & supergiants • Instant gratification • Indirect searches need 10-103 yr for 5-100 AU orbits to complete • Common proper motion companions confirmed in ~ 1 yr • Resolve M sin(i ) ambiguity • Complex & multiple-planet systems established unambiguously • Imaging provides a snap-shot of: • Planets, zodi dust blobs & brown dwarfs or stellar companions • Fourier approach of indirect searches requires many orbits for complex systems ( ~ 1/t) • Sensitivity to planets orbiting non-solar analogs • Doppler is ineffective for early F & A stars • High detection efficiency for young systems • E.g., ~ 50% in a nearby (50 pc) young (10 Myr) association

  6. ARCHITECTURE OF PLANETARY SYSTEMS • 110 Doppler exoplanets • 5% of targeted stars possess massive planets • A diversity of exoplanet systems exist… • How do planets form? • Is the solar system typical? • What is the abundance of solar systems? • Doppler surveys raise new questions, e.g., • What produces the dynamical diversity in exoplanet systems? • Direct imaging can answer these questions • Fast alternative to Doppler surveys • Improved statistics • Worst case, dN/d log(a) ~ const. • Oligarchy, dN/d log(a) ~ a • Searching at large semimajor axis • Characterizing the frequency & orbital geometries of planets > 3 AU will show if our solar system is unique • Reveal the zone where planets may form by gravitational instability • Uncover traces of planetary migration

  7. Simulations Speckle Suppression & Flat Field Noise

  8. LATEST SIMULATIONS • With adaptive modal gain control • 2500 Hz • x 16 Speckle suppression, 0.1% flat field errors • Performance optimized for I = 2,4 6, & 8 • 17.1 cm & 12.8 cm subapertures (48 & 68) * -10 <  < 50, π > 20 mas

  9. SPECKLE SUPPRESSION • Speckle suppression is key to efficient planet detection • > x16-32 suppression of speckle noise is required (field star survey detection rate > 5%) • What is the correct way to model speckle noise suppression? • Currently incorporated as a flat factor • Gain noise • Systematic errors can compromise speckle suppression • How do we specify flat field accuracy? • How do we specify linearity?

  10. SPECKLE SUPPRESSION • Optimizing AO loop parameters & speckle suppression • 18 cm subaperture • I = 7 mag • AO loop rate of 500, 1000, 1500 & 2000 Hz • Speckle noise suppression of x1, x4 & x16

  11. FLAT FIELD NOISE • I < 7 mag. 18-cm subaperture, 51 nm WFE (1500 Hz)

  12. Thermal Background

  13. THERMAL INSTRUMENT BACKGROUND • What is the effect of thermal emission from the AO system & the coronagraph? • Noise associated with the thermal background from telescope, AO & coronagraph can be ignored at H (1.65 µm) • Not true atKS and LP • Important wavelengths because • Predicted planet fluxes are less model dependent at longer wavelengths • Colors are diagnostic both for planets & debris disks

  14. NOISE BUDGET @ KS • When there is no speckle suppression • Speckle noise dominates (!) • No advantage in Ks from cooling the AO or the coronagraph if there is no speckle suppression

  15. Coronagraph thermal noise AO thermal noise Ks Speckle noise Noise sources Median values All planets Detected planets, 5 

  16. Speckle Coronagraph thermal AO thermal Ks Star halo All planets Detected planets, 5 

  17. Ks Number of planets detected No improvement below T ≈ 250 K

  18. Ks Steep gradient Number of planets detected No improvement below T ≈ 250 K

  19. NOISE BUDGET @ KS WITH SPECKLE SUPPRESSION • Speckle suppression alone yields 100 planets if the AO & coronagraph are at ≈ 273 K • AO & coronagraph must not operate at “room temperature” (293 K) • Cooling from 270 K to ≈ 250 K yields only a few more planets • More critical to cool the coronagraph than the AO if using a binary pupil mask

  20. AO thermal Speckle Coronagraph thermal Lp

  21. Lp 5.2% detection rate No improvement below T ≈ 200 K

  22. THERMAL BACKGROUND • Broadly there are two choices • Cool (< 280 K) for H & Ks • Substantial speckle suppression (≈ 10-100) • Detector • NICMOS recipe Hg1-XCdXTe • Cold (< 180 K) for Lp • Thermal background renders speckle suppression irrelevant • Warm ExAOC will be outperformed at LP by a regular AO system optimized for long wavelength operation, e.g., one that uses a deformable secondary • Detector • InSb or JWST style long-wave Hg1-XCdXTe

  23. Astrometry

  24. ASTROMETRIC PROPERTIES OF DETECTED PLANETS • H-band • x10 speckle suppression • 51 nm rms WFE • 3600 s, SNR > 5 • 80% of detected planets have an annual astrometric signature due to orbital motion > 1 pixel (13 mas)

  25. Young Stellar Associations & Clusters

  26. YOUNG STARS I < 9 mag

  27. Young Associations • AB Dor, Beta Pic, Chameleon, Tuc/Hor, & TWA (8-50 Myr)

  28. Ursa Majoris • 300 Myr, d = 9 - 130 pc (median distance = 26 pc)

  29. Hyades • 660 Myr, d ~ 30-60 pc, DEC ~ +15o

  30. Coma Ber. • 400 Myr, d ~ 85 pc, DEC ~ +25o

  31. Pleiades • 125 Myr, d ~ 130 pc, DEC ~ +24o

  32. Alpha Per • 90 Myr, d ~ 165 pc, DEC ~ +50o

  33. Gemini N vs. S • Number of N vs. S targets for I < 7 and < 8 mag • Young (< 700 Myr) • Nearby (< 100 pc) • Need a I < 8 mode • N/S dichotomy is heavily dependent on weight placed on the Hyades

  34. Typical Observing Sequence Young Association / Open Cluster Surveys Algorithm selects a set of several targets with similar magnitude and zenith angle which provide a check on possible AO artifacts Field Star / Nearby Young Star Surveys Algorithm selects a group of targets based on LST & current conditions 1. Target Selection 2. Target Acquisition & Initial System Configuration Control systems retrieves RA/DEC proper motion, VRI mags, SpT from catalogue & sends information to telescope control & instrument Current conditions information sent to AO control Science Instrument Shutter closed / ND filter selected Array in continuous reset to mitigate persistence Telescope Slew to target AO System Open loops, close hatch Estimate control loop parameters from target & conditions information Spatial filter aperture set to open WFS ND filter selected if necessary ADC selected Coronagraph Pupil mask selected and slewed to PA Focal plane stop selected and slewed to PA Calibration System / Slow WFS Configured for target brightness, observing l Science Instrument Select H-band filter and possibly ND filter Set exposure time for unsaturated image Acquire SNR~100 unsaturated image Pipeline confirms centering & Strehl Reacquire target if unsatisfactory AO System AO hatch opens to receive starlight Close AO loops Offload low order modes to telescope ADC begin tracking Flexure control/beam stabilization enabled Wait for AO loop optimization to update Close spatial filter iris Wait for AO loop optimization 3. Final System Configuration after Target Acquistion Calibration System Enable & wait for updates to take effect Companion Confirmation and Characterization Repeat H-band detection exposure from previous epoch with increased SNR if needed to measure companion position Repeat unsaturated image to measure star position If the companion is physically associated: Obtain JHK broadband images for color information Obtain narrow H-band filter images filters on H2O, CH4 features and continuum regions Combine coronagraph with grism to obtain R~2000 spectra J band: KI, FeH, H2O temperture/gravity sensitive features K band: H2O absorption features correlated with spectral type Companion Detection Configure science camera on RG subarray Select total exposure time based on target age/distance algorithm will provide estimates Repeat exposures for pupil mask angles 90°, 180°, 270° Repeat with pupil mask offsets of +5, -5 degrees Offset field and obtain an equal amount of sky data sky frames can be shared between cluster members individual sky frames must be obtained for field targets Obtain equivalent images on a PSF star for field targets 4. Take Science Exposures 5. Data Pipeline

  35. CONCERNS & OUTSTANDING ACTIONS • Thermal background calculations assume no stray light • Only in-beam elements contribute to the background • How do we achieve 1-pixel astrometric stability & what is the algorithm for extraction of astrometric signature? • How important are the Hyades and  Per • Star-by-star planet detection probability for young associations and clusters • Adjunct science • Minimum mission and alternatives for reduced performance

  36. Fin

More Related