Pushing the Envelope Unleashing the Potential of High
- Slides: 66
Pushing the Envelope: Unleashing the Potential of High Contrast Imaging with HST Glenn Schneider Elizabeth Stobie Steward Observatory, University of Arizona (NICMOS/IDT)
HST Provides a Unique Venue for High Contrast Imaging • Diffraction Limited Imaging in Optical/Near-IR • Highly STABLE PSF Background Rejection • Very High Strehl Ratios 1. 6 mm: ~10 -6 pix-1 @ 1” 1. 1 mm: ~10 -5 in 2”-3” annulus • Coronagraphy: NICMOS STIS, ACS • Intra-Orbit Field Rotation NIR High Dynamic Range Sampling NICMOS/MA: Dmag=19. 4 (6 x 4 m)
H-Band (F 160 W) Point-Source Detectability Limits Two-Roll Coronagraphic PSF Subtraction 22 m Total Integration DH(5 s) = 7. 14 + 3. 15 r” - 0. 286 r” 2 Photon Noise Dominated Read Noise Dominated . . H=6. 9
Scientific Areas of Investigation via PSF-Subtracted Coronagraphic Imaging Extra-Solar Planet & Brown Dwarf Companions Circumstellar Disks
The Dusty Disk/Planet Connection? Current theories of disk/planet evolution suggest a presumed epoch of planet-building via the formation and agglomerative growth of embryonic bodies, and the subsequent accretion of gaseous atmospheres onto hot giant planets, is attendant with a significant decline in the gas-to-dust ratios in the remnant protostellar environments. In this critical phase of newly formed (or forming) extra-solar planetary systems, posited from a few megayears to a few tens of megayears, megayears the circumstellar environments become dominated by a second-generation population of dust containing larger grains arising from the collisional erosion of planetesimals.
Young Substellar Objects are Much Easier to Detect. . .
A Brief Overview Coronagraphic Imaging Analysis/Processing File Load Image Save Image Load List Save All Images Delete Images Print Edit Preferences Set Colors Save List Parameters Restore List Parameters New Capabilities Need New Tools IDP 3 * High Precision Photometry & Astrometry On Stacks of Images *Special Thanks to: D. Lytle
Stack Oriented Inter-Image Arithmetic Operations Add Subtract Average Minimum Exclusive Or Divide Multiply Positive Abs(Negative) After Application of Image Attributes: • Flux: Scale and Offset (Bias) • Geometry: Position, Rotation, Distortion
Interactive & Dynamic Control Of Image Attributes
Global Interactive Session Control via “On the Fly Preferences” Plus, Static Session Control via “IDP 3 Preference File”
Global Images Operations Show Images Select Image Resample (Zoom) All Off All On All Flip Y All Add All Subtract All Average All Minimum All Pad All Remove Pad Median Images Sigma-Clipped Median Sigma-Clipped Mean
CORONAGRAPHIC COMPANION DETECTION Multiaccum Imaging at two S/C orientations In a single visability period. Background objects rotate about occulted Target. PSF structures and optical artifacts do not. TWA 6. Two Integrations: Median of 3 Multiaccum Each D Roll = 30° D Time = 20 minutes
At r=2. 5” (where image of companion emerges, background brightness is reduced by an ADDITIONAL factor of 50 over raw coronagraphic gain (of appx 4). Each image of TWA 6 B is S/N ~20 in difference frame. Above: Coronagraphic Images H companion = 20. 1 DH = 13. 2 D Roll: 30° Left: Difference Image Same display dynamic range
Extract subarray from difference image into a “region of interest” window. . .
Adjust Position to. . .
Minimize local residuals in region near companion image while constraining background to be statistically zero. . .
Correct Image Geometrically for Field Distortions
Before Distortion Correction
After Distortion Correction
Positive Image Extracion
Negative Image Extraction (Inverted)
Rotate Negative Extraction About Occulted Target And Add After Inversion
Model and Remove Diffraction Spike Residuals* *DSPK
Photometry And, is it a Point source?
Radial Profile, Photocentric Moment & Gaussian Fitting
Residuals from 2 D Gaussian Model Subtracted from Data Are Identical to Those Expected from NICMOS Camera 2 F 160 W PSF at the Coronagraphic Focus.
Sensitivity: Noise Equavalent Background Assessment
Detectability: (r, q) Dependence via Model PSF Implantation Observed Model* Nulled Implant *Tiny. Tim 5. 0 PSF Sequential Implantation by IDP 3 Paramater Filename Xoffset Yoffset Rotation Scale Bias Zoom Pad Xpad Ypad Rotxcen Rotycen Xpixscale Ypixscale Mov. Amt Rot. Amt Scl. Amt Flipy Clipmin Cminval Clipmax Cmaxval Xpix Ypix Nxpix Nypix Centroidy Display Visible
Detectability: (r, q) Dependence via Model PSF Implantation
Detectability: (r, q) Dependence via Model PSF Implantation
. Photometric Efficacy & Statistical Significance 25 S/N (Positive Implant Only) % Recovered Flux 20 16 12 8 4
TWA 6 B Detection Illustrates Performance Repeatability Two-Roll Coronagraphic PSF Subtraction 22 m Total Integration DH(5 s) = 7. 14 + 3. 15 r” - 0. 286 r” 2. .
TWA 6 A/B TW Hya Assn D = 55 pc Age = 10 Myr r=2. 54”, 140 AU DH =13. 2 (LB/A)[H]=5 x 10 -6 Habs = 16. 6 Implies: • Mass ~ 2 Jupiter S/NTWA 6 B = 35 • Teff ~ 800 K IF Companion. . .
Is it, or Isn’t It? • Undetected in NICMOS 0. 9 mm Followup Observation I-H > 3 • Marginally Detected in 6 -Orbit Binned STIS G 750 L Spectrum • Colors Consistent with 2 Mjup, 10 Mjup, “Hot” Giant Planet Instrument Bandpass Mag NICMOS/C 2 F 160 W 1. 40— 1. 80 20. 1 NICMOS/C 2 F 090 M 0. 80— 1. 00 >23. 1 STIS/G 750 L I extract 0. 81— 0. 99 ~25. 4 STIS/G 750 L R extract 0. 63— 0. 77 >27. 2
Is it, or Isn’t It? • Undetected in NICMOS 0. 9 mm Followup Observation I-H > 3 • Marginally Detected in 6 -Orbit Binned STIS G 750 L Spectrum • Colors Consistent with 2 Mjup, 10 Mjup, “Hot” Giant Planet ~25. 4 >27. 2 >23. 1 20. 1 • Keck/AO Astrometric (PM) Follow-up Thus-Far Inconclusive
Direct (Scattered Light) Imaging of Dusty Debris Observing scattered light from circumstellar debris has been observationally challenging because of the very high Star: Disk contrast ratios in such systems. Until very recently the large, and nearly edge-on disk around b Pictoris remained the only such disk imaged. Resolved imaging 1984 - B. A. Smith & R. J. Terrile 6" radius coronagraphic mask, Las Campanas (discovery image) b Pictoris spatial distribution of dust/debris. Asymmetries (radial & azimuthal): • May implicate low-mass perturbers (planets) from: Rings, Central Holes, Gaps, Clumps, Arclets • Help Elucidate the scattering & physical properties of the grains.
Arc Seconds (Y) NICMOS Observations of the HR 4796 A Circumstellar Debris Ring GEOMETRY -1. 0 F 160 W PA = 26. 8°± 0. 6° i = 73. 1°± 1. 2° -0. 5 a = 1. 05”± 0. 02” MORPHOLOGY 0. 0 N r = 70 AU width < 14 AU 0. 5 E “abrupt” truncation m. Jy/pixel “clear” @ r < 50 AU 1. 0 0 20 40 60 80 FLUX DENSITY 12. 8± 1. 0 m. Jy @ 1. 1 mm -1. 0 F 110 W 12. 5± 2. 0 m. Jy @ 1. 6 mm -0. 5 H(F 160 W) = 12. 35± 0. 16 0. 19 J(F 110 W) = 12. 92± 0. 08 0. 0 N Tdust ~ Ldisk/L* -3 @ 1. 1 mm 1. 4± 0. 2 x 10 0. 5 E -3 @ 1. 6 mm m. Jy/pixel 2. 4± 0. 5 x 10 1. 0 0 20 40 60 80 100 NIR scattered flux in good agreement with visible 1. 5 1. 0 0. 5 0. 0 -0. 5 -1. 0 -1. 5 Arc Seconds (X) absorption & mid-IR re-radiation.
NICMOS Observations of the HR 4796 A Circumstellar Debris Ring -1. 0 F 160 W Anisotropies NE ansa ~ 15% brighter than SW ansa. -0. 5 0. 0 N Arc Seconds (Y) 0. 5 E m. Jy/pixel 1. 0 0 -1. 0 20 40 60 80 F 110 W Implications Possible dynamical confinement of particles by one or more unseen bodies. -0. 5 0. 0 N 0. 5 E m. Jy/pixel 1. 0 0 1. 5 1. 0 Suggestion of preferential (forward) scattering to SE. 20 40 0. 5 0. 0 -0. 5 Arc Seconds (X) 60 -1. 0 80 100 -1. 5 Mean particle size > few mm. debris origin, not I. S. dust.
HR 4796 A Circumstellar Debris Ring NICMOS Additional processing recovered ring flux closer in and suggested somewhat higher inclination (~76°). “Clumpiness” due to residuals in PSF subtraction, not attributed to structure of ring.
STIS Observations of the HR 4796 A Circumstellar Debris Ring HR 4748 (PSF) HR 4796 A Orient #1 Orient #2 DOrient = 16°
STIS Observations of the HR 4796 A Circumstellar Debris Ring HR 4748 (PSF) HR 4796 A Orient #1 Orient #2 + _
STIS Observations of the HR 4796 A Circumstellar Debris Ring PSF Orient #1 PSF Orient #2 Better Focus Match Better Position Match Better Focus Match Varience Minimized (Flux & Position Adjusted) PSF Subtractions
STIS Observations of the HR 4796 A Circumstellar Debris Ring PSF Orient #1 PSF Orient #2 2 -rolls samples regions otherwise obscured by wedge & spikes N E Varience Minimized (Flux & Position Adjusted) PSF Subtractions
STIS Observations of the HR 4796 A Circumstellar Debris Ring Weighted Image Combination - Resampled
HR 4796 A RING GEOMETRY (Least-Squares Isophotal Ellipse Fit) Ansal Separation (Peaks) = 2. 107” ± 0. 0045” Major Axis of BFE = 2. 114” ± 0. 0055" P. A. of Major Axis (E of N) = 27. 06° ± 0. 18° Major: Minor Axial Length = (3. 9658 ± 0. 034): 1 Inclination of Pole to LOS = 75. 73° ± 0. 12° Photocentric Offset from BFE(Y) = -0. 0159" ± 0. 0048" Photocentric Offset from BFE(X) = +0. 0031" ± 0. 0028"
HR 4796 A Circumstellar Debris Ring - WIDTH Brightness (Normalized to NE Ansa) WIDTH AT NE ANSA FWHM: 12. 9± 0. 7 AU 9. 6% Dring * 1 -e-1: 7. 5± 0. 4 AU 11. 9% Rring Measured = 0. 197” PSF point source = 0. 043” FWHM ring = 0. 192” * 1 -e-1 = 0. 126” Slightly asymmetric
RING GEOMETRY - Least-Squares Isophotal Ellipse Fit Ansal Separation (Peaks) = 2. 107” ± 0. 0045” Major Axis of BFE = 2. 114” ± 0. 0055" P. A. of Major Axis (E of N) = 27. 06° ± 0. 18° Major: Minor Axial Length = (3. 9658 ± 0. 034): 1 Inclination of Pole to LOS = 75. 73° ± 0. 12° Photocentric Offset from BFE(Y) = -0. 0159" ± 0. 0048" Photocentric Offset from BFE(X) = +0. 0031" ± 0. 0028"
“FACE-ON” PROJECTION - With Flux Conservation
Spatially Resolved Relative PHOTOMETRY of the Ring
Photometric Error Estimation
N-Sigma Brightness Ratio (Percent) NW: SE Surface Brightness Anisotropy
N-Sigma Brightness Ratio (Percent) Front: Back Surface Brightness Anisotropy
Aperture Photometry STI�S( leff 0. 58 mm): F(ring[unobscured])/F(star) = 0. 00049 ± 0. 0 NICMOS (leff 1. 10 mm): F(ring[unobscured])/F(star) = 0. 00083 ± 0. 00012 (14. 3%) NICMOS (leff 1. 60 mm): F(ring[unobscured])/F(star) = 0. 00140 ± 0. 00029 (20. 8%)
Wavelength Dependent Scattering Efficiency (Color)
HR 4796 A SUMMARY Ring geometry/astrometry defined by NICMOS improved by higher resolution STIS observations. Notably, i 2. 6° larger than original (published) NICMOS solution. Spatially resolved photometry of ring with ± 2% uncertainty at ansae (1”), and ± 6— 8% uncertainty at 0. 6— 0. 5”. Characteristic width ~ 10% of 70 AU radius ring. “Left/Right” brightness anisotropy or ~20% along at least 50° wide diametrically opposed arcs centered on ansae. “Front/Back” brightness anisotropy, roughly symmetric in both L/R “hemispheres”, increasing with longitudinal distance from ansae to 35% difference at 30° from ansae. Ring is uniformly RED from “V” to H with 1: 1. 7: 2. 9 spectral reflectance in CCD 50(“V”): F 110 W(1. 1 mm): F 160 W(H).
Brightness Anisotropies, Confinement & Color Consistent with Dynamical Interactions with Co-Orbital Unseen Planet-Mass Bodies
And, other examples of disk morphologies which May implicate the existance of unseen planets are revealed by HST coronagraphy. . . (eg. , HD 141569 A) … with the help of IDP 3.
IDP 3 is an IDL based application and may be downloaded from the NICMOS Project server at: http: //nicmos. arizona. edu It has found many uses.
IDP 3 is an IDL based application and may be downloaded from the NICMOS Project server at: http: //nicmos. arizona. edu It has found many uses.
IDP 3 is an IDL based application and may be downloaded from the NICMOS Project server at: http: //nicmos. arizona. edu It has found many uses.
IDP 3 is an IDL based application and may be downloaded from the NICMOS Project server at: http: //nicmos. arizona. edu It has found many uses.
IDP 3 is an IDL based application and may be downloaded from the NICMOS Project server at: http: //nicmos. arizona. edu It has found many uses.
IDP 3 is an IDL based application and may be downloaded from the NICMOS Project server at: http: //nicmos. arizona. edu It has found many uses.
IDP 3 is an IDL based application and may be downloaded from the NICMOS Project server at: http: //nicmos. arizona. edu
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