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Coronagraphy with HST/NICMOS* *The Near Infrared Camera & Multi-Object Spectrometer Extending HST’s UV/Optical Panchromatic Vision into the Near IR (0.8mm —2.4 mm) Glenn Schneider Steward Observatory, University of Arizona (NICMOS/IDT) Hubble Space Telescope Third Calibration Workshop 18 October 2002 Baltimore, Maryland http://nicmosis.as.arizona.edu:8000 [email protected] NICMOS Coronagraphy Takes Advantage of HST’s Unique Venue for High Contrast Imaging • Diffraction Limited Imaging in Optical/Near-IR •> 98% Strehl Ratios @ all ls Background Rejection* • Highly STABLE PSF 1.6mm: ~10-6 pix-1 @ 1” 1.1mm: ~10-5 in 2”-3” annulus • Highly Accurate Pointing Repeatability & Control *w.r.t. central pixel • Intra-Orbit Fcentral(H) = 11% Fstar Field Rotation NIR High Dynamic Range Sampling NICMOS/MA: Dmag=19.4 (6 x 4m) Scientific Areas of Investigation Enabled With Today’s Capabilities on HST via PSF-Subtracted Coronagraphic Imaging Young Extra-Solar Planet* & Brown Dwarf Companions HR 4796A 1" Circumstellar Disks fdisk/f* > few x 10-4 at 1” q = 0.1” TWA 6 * < few x 106 yr at 1” Damped La Absorbers LBQS 1210+1713 Cooling Curves for Substellar Objects 0 Evolution of M Dwarf Stars, Brown Dwarfs and Giant Planets (from Adam Burrows) Log L/L(sun) -2 200M jup 80M jup -4 -6 14M jup -8 STARS (Hydrogen burning) BROWN DWARFS (Deuterium burning) JUPITER PLANETS -10 6 7 SATURN 8 Log10 Age (years) 9 10 Planet-Building Timeline Taurus, Ophiuchus star forming regions TW Hydrae Tucanae Hyades Assoc Pleiades Assoc a Persei 106 yr s Collapsing protostar forms protoplanetary disk 107 yr s 108 yr s Giant planets accrete gaseous atmospheres Rocky cores of giant planets form Era of heavy bombarment by comets Terrestrial planets form Disk Evolution/Dissipation(?) Primary Dust (≤ mm) Secondary Dust (≥mm) Locked to Gas Collisional erosion Sun 109 yr s Current age of the Sun: 5x109 yrs . Clearing of inner solar system, formation of a Kuiper cometary belt? Clearing Timescales: P-R drag few 10 6 Rad. Pressure: ~ 104 From: R. Webb Coronagraphic Companion Detection PSF “Roll Subtraction” Separate into Positive & Negative Conjugates Coronagraphic Images D Orientation = 30° HD 102982 H = 6.9 G3V DH = 5.3 r = 0.9" Difference Image Rotate about Hole Center and Co-Add (Resampled) (Multiaccum) Imaging at two S/C orientations in a single HST visability period. Background objects rotate about occulted Target. PSF and optical artifacts do not. DRoll = 30°, DTime ≈ 20 min., Total time per Orientation ≈ 11 min. Combined detection floor in absence of background light: H ≈ 23 Combined detection floor in absence of background light: H ≈ 23 H = 21.9 r = 9.36” DH = 12.6 TA Persistence Ghost Images H = 22.3 r = 13.34” DH = 12.9 LHS 3003 H = 9.3 Coronagraphic Performance (G2V) . Radius (Pixels) from Hole Center 5 7 9 11 13 B A C K G R O U N D 16 R E D U C T I O N 9 15 14 13 12 11 10 8 INTENSITY (AZIMUTHAL AVERAGE) 10 0 5 17 19 21 23 25 27 29 31 33 35 37 REDUCTION IN BACKGROUND FLUX FROM F160W PSF w.r.t. central pixel Fcentral(H) = 11% Fstar 10-1 Unocculted PSF Coronagraph Coronagraph & PSF Subtraction 10-2 1 pixel 10-3 10-4 10-5 7 6 15 10-6 0 Coronagraphic Hole Radius = 0.3" 0.075 0.15 0.225 0.3 0.375 0.45 0.525 0.6 0.675 0.75 0.825 0.9 0.975 1.05 ARCSECONDS 4 3 2 0.3 0.45 0.6 0.75 0.9 1.05 1.2 1.35 1.5 1.65 1.8 1.95 2.1 2.25 2.4 2.55 2.7 2.85 Radius (Arcsec) from Hole Center General Description Coronagraphic Field of View • NICMOS Coronagraph is in Camera 2*: 256 x 256 pixels @ ~ [76.2, 75.5] mas / pixel FOV ~ 19.49” x 19.33” (377 ”) 0.9% X:Y Linear Geometrical Distortion • Radius of Occulted Region = 0.3” Size “Optimized” for H-band Imaging (1st Airy Ring fully contained) ~ [+73, -45] pixels (or [+5.6”, -3.4”] from [-X,+Y] corner of FOV • Field Asymetric w.r.t Occulted Star For maximum S/C Roll (at one epoch) of 29.9°: 475 ” Survey Area with 280 ” Overlap Area * http://www.stsci.edu/hst/nicmos/performance/platescale/rel_platescale.html Coronagraphic Companion Detection PSF “Roll Subtraction” EXAMPLE: TWA 6, H = 6.9 Two Integrations from Median of 3 Multiaccums Each Total Integration Time = 640 seconds at Each Orientation DRoll = 30°, D Time = 20 minutes Linear Display 0—20 ADU/sec/pixel; 2.19E-6 Janskys/ADU/sec/pixel Coronagraphic Companion Detection Unresolved (Point-Like) Object: H =20.1, DH = 13.2, r=2.5” Linear Display 0—2 ADU/sec/pixel; 2.19E-6 Janskys/ADU/sec/pixel Coronagraphic Companion Detection PSF “Roll Subtraction” Difference Image: H =20.1, DH = 13.2 (La/Lb = 200,000:1), r=2.5” At r=2.5” background brightness is reduced by an ADDITIONAL factor of ~50 over raw coronagraphic gain (of appx 4). Linear Display -0.4 — +0.4 ADU/sec/pixel; 2.19E-6 Janskys/ADU/sec/pixel Coronagraphic Companion Detection PSF “Roll Subtraction” Each independent point- Geometrical Rectification And De-Spiking* source image is S/N ~ 20 *NICMOS/IDT Post-Processing & Analysis S/W: DSKP & IDP3 ftp://nicmos.as.arizona.edu/ Linear Display -0.4 — +0.4 ADU/sec/pixel; 2.19E-6 Janskys/ADU/sec/pixel Coronagraphic Companion Detection PSF “Roll Subtraction” “Final” Image After Additional Post-Processing 2.0 1.0 0.0 1.0 Arc Seconds 2.0 TWA6 PSF FWHM = 0.16" Image Combination & Spatial Filtering A spatial filter is applied to the combined image to further reject image artifacts with characteristic frequencies not commensurate with the size of a stellar PSF. 1 S/N ~ 35 I(r)/I(peak) 0.8 0.6 0.4 0.2 NICMOS F160W 25 OCT 1998 Camera 2 (0.076"/pixel) Coronagraph (0.3" radius) Integration Time =1280s 0 0 1 2 3 4 Radius (Pixels) 5 6 Sensitivity (S/N=25) vs. Detectability (50% Probability*) H-Band Two-Roll Coronagraphic PSF Subtraction 22m Total Integration DH(50%) = 9.7±0.3 + 2.1 x r {M–G Stars} Delta-H TWA6 and Median of 50 G-K Stars in NICMOS Survey * Determined by Noise Statistics AND Model Star Implantation PRELIMINARY Post SM-3B Coronagraphic Performance Characterization for HST Cycle 11/12 Data from SMOV3B Test Programs: • Coronagraphic Target Acquisition Test* • Coronagraphic Focus Verification* • Initial (Part 1) Performance Check - Characterization† *Executed Prior to “Final” Plate Scale / Aperture Rotation Updates †Executed Prior to Low Scatter Point Determination / Adjustment To Be Executed (Next Week) Under Cycle 11 Cal Program • Coronagraphic Light-Scatter Minimization • “Final” (Part 2) Performance Check - Calibration Coronagraphic First Light Post-SM3B “Out of the Box” CYCLE 7 GTO/7227 CYCLE 11 SMOV3B/8983 0 — +2.0 ADU/sec/pixel 2.19E-6 Jy/ADU/sec/pixel 0 — +2.75 ADU/sec/pixel 1.59E-6 Jy/ADU/sec/pixel Coronagraphic First Light Post-SM3B “Out of the Box” CYCLE 7 GTO/7227 CYCLE 11 SMOV3B/8983 -0.4 — +0.4 ADU/sec/pixel 2.19E-6 Jy/ADU/sec/pixel -0.55 — +0.55 ADU/sec/pixel 1.59E-6 Jy/ADU/sec/pixel I(Direct)/I(Coronagraphic) 25 F 1 6 0 W Coronagraphic Performance (M9.5V+) Direct/Coronagraphic 20 15 10 5 100-3 Coronagraphic Direct (Total = 23700 ADU/sec) I(pixel)/I(star) 10-4 10-5 10-6 10-7 10-8 Direct Coronagraphic 10 20 30 Radius (Pixels) 40 50 Coronagraphic PSF-Subtraction Induced Image Artifacts The Dominant Source of Systematic Error (“Noise”)* Imperfections in PSF-subtractions result in residuals larger than expected from pure photon noise. Systematics: OTA “Breathing” Target Re-centration Coronagraphic Hole Edge Effects Cold-Mask “Wiggles” Opto-Mechanical Stability *For properly reduced/calibrated images “Breathing” - The Coronagraphic Nemesis De-spaceing of the HST secondary mirror along the telescope optical axis from (orbit driven) thermal instabilities in the OTA causes variations in the PSF structures which are typically THE dominant source of systmatic errors in coronagraphic PSF subtraction. The thermal time constant of the OTA is longer than sub-orbit timescales. “Two roll” coronagraphic observations should be completed in a single target visibility period to minimize PSF variations. Reference PSFs should be obtained as close in time (very preferabley in the same visibility period) as target images WITHOUT any intervening changes in Sun angle. Coronagraphic Optics General Description • Coronagraphic “Hole” On Camera 2 Field Divider Mirror @ OTA f/24 Focus Physical Radius: 170mm Projected Radus: 0.3” • Lyot Stop (85% Unobscured Area) At Cold Pupil in VCS (near Filters) Obscurations for (warm): Primary Mirror Outer Edge Secondary Mirror Housing Primary Mirror Hold-Down Pads F160W PSF “Mapped” Onto Coronagraphic Hole A small change in energy distribution in the first Airy ring (due to breating induced focus shifts) cause scattering sites on the hole-edge to “light up” and change, significantly, the downstream scattering. HH30 Obscured A Few GMWords AUR on Unembedded Circumstellar (AvDisks… < 0.5) Red Polar Lobes 10 mJy arcsec-2 Direct Image Lower Scattering Surface 0.2 mJy arcsec-2 Faint Blue Ribbon J* = 0.33 Jy H* = 0.40 Jy Observing young circumstellar disks Coronagraph + With obscured central stars isPSF notSubtraction difficult. Disk systems with unembedded, or only marginally obscured central stars are much more observationally challenging and require PSF-subtracted coronagraphy. For Disk Imaging, to Minimize Image Artifacts Resulting from Reference Subtraction, Reference PSFs Should Be: • Obtained in the same visability period as the target whenever possible • Of Similar Spectral Type (Within One Spectral Class) • At Least as Bright as The Target HR 4796A For Disk Imaging, to Minimize Image Artifacts Resulting from Reference Subtraction, Target Images Should Be • Obtained at Two or More Spacecraft Roll Orientations TW HYDRAE HD 141569A Calibrating Coronagraphic Data Be Critical of “Pipeline” Results Performance Levels Discussed ASSUME Properly Calibrated Data Local and Global Deviations from True Photometric Backgrounds MUST Be Corrected (Zeroed) Before PSF-Subtraction, Otherwise: Loss of Sensitivity (Against Residual Background) Degraded Detectability in PSF-Subtracted Images Photometric Zero-Point Errors Spatial Non-Uniformity in Detection Limits Calibrating Coronagraphic Data Be Critical of “Pipeline” Results REFERENCE FLATS: - Hole “imprint” in CDBS flats is static, in reality it moves. Augment Reference Flats with Contemporaneous TA Lamp Flats. - Construct Reference Flats So As Not To Rely on Assumed High Fidelity of Knowledge of Linearity Transfer When Approaching Saturation. I.e., “throw away” reads > 50—70% full well when making reference flats. REFERENCE DARKS: See Silverstone Poster (This Workshop) - “Synthetic” (Decomposed Models) Generated by OTFR vs. Three Day “Snapshot” - Median ObservedOf vs.Coronagraphic Hole - Combined (Temperature &Motion SAA Decay) Selected Calibrating Coronagraphic Data Be Critical of “Pipeline” Results OTFR/CALNIC 10 October 2002 Using “Best” Ref Data Flat-Field Imprint Non-Zero Background Quadrant Offsets “Photometrically Challenged” Column Dead, Grotty, Excessively Hot Pixels CALNICA ANALOG (+ Bad Pixel Replacement) ObsDARKS/LinFLATS Or… Post-Processing Tools Exist To Mitigate Calibration Errors, But Often Do Not Work Well In Regions of High Flux Densities and Large Signal Gradients Calibrating Coronagraphic Data Be Critical of “Pipeline” Results OTFR/CALNIC 10 October 2002 Using “Best” Ref Data Progressively “Better” Flat-Field / Zero-Point Calibration Sequentially Through the Orbit Is a Tell-Tale Sign of A DC Offset Matching Problem. Calibrating Coronagraphic Data Be Critical of “Pipeline” Results OTFR/CALNIC 10 October 2002 Using “Best” Ref Data CALNICA ANALOG (+ Bad Pixel Replacement) ObsDARKS/LinFLATS Post-Processing to Remove Electronic Image Artifacts: Saturation Bands & Echos “Mode 2” Target Acquisition (TA) Target Blind-Pointed into 128x128 Pixel Acquisition Sub-Array Allowing for GSC errors co-ordinates must be known to ± 3.8” Central region of TA field-of-regard nearly free of detector defects. CYCLE 11 BRIGHT OBJECT LIMIT: H = 4.0* *Using F187N (1%) filter TA Performance Verified: SMOV 8979 CYCLE 11 FAINT OBJECT LIMIT: H ~ 18* *Acquisition in one orbit, imaging in subsequent orbit(s) “Mode 2” Target Acquisition (TA) Cycle 11 (77K) Exposure Time Requirements (F160W) “Mode 2” Target Acquisition (TA) ASTROMETRIC ANCHOR (Where is My Target?) TA Images with S/C Pointing & Acquisition (“Engineering”) Data Provide Necessary Information to Accurately Determine Occulted Target Position AFTER Offset Slew Maneuver - Early Cycle 7: SPT file in raw “engineering” units - Later Cycle 7: SPT file in detector pixels in FSW coordinates - Cycle 11: _RAW, _CAL files in detector pixels (FSW) SIAF[X, Y] = 256 - FSW[Y, X] May Need to Correct “Requested” vs. Actual Post-Slew Target Position Due to Secular Change(s) in Image Scale and/or Aperture Rotation Angle. (FSW uses Fixed constatnts). “Mode 2” Target Acquisition (TA) PHOTOMETRIC ANCHOR (How Bright is My Target?) Stellar PSF Cores Will Saturate at Shortest (0.2s) Exposure Times for: F160W: H < 7.2 F165M: H < 6.5 F171M: H < 5.5 F187N: H < 4.0 If H < 4 Need Mode-1 Target Acquisition TA Images Can Be Used To Establish In-Band Magnitudes of Target for Acquisition Filter Used. “Hole Locate” Lamp-Flat Background (2x7s ACCUM) Images May Be Used to Obtain H-Band Magnitude of Target. For subsequent Coronagraphic Imaging in Other Filters Take Unsaturated UNOCCULTED Images (when possible) to Establish PSF Core Photometry “Mode 2” Target Acquisition (TA) ASTROMETRY / PHOTOMETRY BUT… TA Images are *NOT* Calibrated in OPUS Pipeline. Shading Biases Target Centroids With Horizontal Field Gradients AND Photometry Through Flat-Field Errors TA Process PROVIDES: - Two F160W Lamp Flat Images & Backgrounds (used by on-board hole-location algorithm) And… Necessary To Augment Reference Flats Used In Calibrating Follow-On Coronagraphic Imaging (But Not Used in OPUS Pipeline) - Two Acquisition “ACCUM” Mode Images (for CR Minimization) “Mode 2” Target Acquisition (TA) ASTROMETRY / PHOTOMETRY Dark Current is (Generally) Not An Issue, Shading Is TA Images may also be corrupted by “the bands”, which could be a problem if they go through the target OPUS Does Not Currently Use Observed or “Synthetic” ACCUM Darks for TA Image Processing Options: - Take “ACCUM” Mode Darks (+0.025s) - Build Source-Clipped Column-Medians from TA Images to Remove Shading Signature & DC Offsets Before Flat-Fielding EXAMPLE….. Note: 7s F160W Target Images in Background Frames A contemporaneous reference flat for the region around the coronagraphic hole can (should) be made from the TA lamp flats & backgrounds (S/N ~120, combined), And used to flatfield the subsequent coronagraphic Images. Coronagraphy with HST/NICMOS SUMMARY SMOV3B Program Has Demonstrated Full Return of Capabilities Coronagraphic Diffracted & Scattered Light Rejection Comparable to Cycle 7. Should be Fully Restored After Low Scatter-Point Mapping and Compensation. Coronagraphic Detectability (Direct and with PSF-Subtraction) Comparable to Cycle 7, with Increased Sensitivity Due to QE Improvement @ 77K (DQE~37% in H-band relative to cycle 7). Final Performance Metrics and Calibration Pending Completion of Cycle 11 Calibration Test Plan. Ready to Resume NICMOS Coronagraphic Science (if any proposals are accepted for HST Cycle 12). Coronagraphy with HST/NICMOS* *The Near Infrared Camera & Multi-Object Spectrometer Extending HST’s UV/Optical Panchromatic Vision into the Near IR (0.8mm —2.4 mm) Glenn Schneider Steward Observatory, University of Arizona (NICMOS/IDT) http://nicmosis.as.arizona.edu:8000 [email protected] General Description “Coronagraphic Focus” • The f/24 (FDM) and f/45 (detector) image planes are suppose to be confocal. Because of the “dewar anomoly” they are not. 1200 DIRECT DET DIRECT FDA C O 1000 U N T 800 CORON DET CORON FDA R A T 600 E / P 400 I X E 200 L 0.3 0.45 0.6 0.75 RADIUS 0.9 1.05 ( ARCSECONDS) 1.2 1.35 To achieve “Best Focus” at the detector (for “direct” imaging), a star image on the FDA mirror is de-focused, so light from the 1st Airy ring scatters off the edge of the coronagraphic hole with much greater intensity (3x at 1.51.6mm). General Description “Coronagraphic Focus” • The f/24 (FDM) and f/45 (detector) image planes are suppose to be confocal. Because of the “dewar anomoly” they are not. 1200 DIRECT DET DIRECT FDA C O 1000 U N T 800 CORON DET CORON FDA R A T 600 E / P 400 I X E 200 L 0.3 To reduce edge scattering, and recover image contrast, the PAM mirror is moved (by ~ 2mm) for coronagraphic imaging. As a result the unocculted PSF is slightly de-focused. 0.45 0.6 0.75 RADIUS 0.9 1.05 ( ARCSECONDS) 1.2 1.35 1.5 Question: Can you comment on the Coronagraphic Focus? Answer: Follows… SMOV/3B Coronagraphic Focus Check Detector F187N F160W F110W Intermediate Field Divider Mirror Coronagraphic Focus Check - F187N Azimuthal Average Per Pixel Intensity Focus @ Detector Focus @ FDA Mirror Coronagraphic Focus Check - F160W Azimuthal Average Per Pixel Intensity Focus @ Detector Focus @ FDA Mirror Coronagraphic Focus Check - F110W Azimuthal Average Per Pixel Intensity Focus @ Detector Focus @ FDA Mirror “Coronagraphic Focus” The peak of an unocculted stellar PSF at the coronagraphic focus is reduced in intensity by ~ 17%. This is more than an acceptable trade given the reduction by a factor of 3 in the scattered background near the coronagrahic hole. DATA from SMOV/7157 (Cycle 7) and SMOV/8984 (Cycle 11). PSF CORE FWHM DIRECT CORON INTENSITY General Description . 1.934 pix 0.1466” 1.954 pix 0.1481” I N T E N S I T Y RADIUS (PIXELS)