The current state of speckle imaging

Nic Scott

NASA ARC

  • brief history and introduction

    • milestones

    • technology

  • publications

  • instrument programs

  • science programs  & recent highlights

  • future

The Rayleigh criterion and the tyranny of the atmosphere

\Theta = 1.22 \lambda/d
\approx \lambda / r_0

but in atmosphere, turbulent cells limit resolution to 

Fizeau & Michelson

Brown & Twiss

1850s

1890s

1920 - measured Betelgeuse (with Pease)

1956 - HBT effect, correlation b/t coherent photons

detail lost to the atmosphere can be regained through interferometric analysis 

Intensity interferometry

Labeyrie

1970

Text

a method to obtain diffraction-limited resolution across the full aperture of a large telescope

 long exposure

speckles blur

produce Airy pattern

true images are impossible, only centrosymmetric objects can be reconstructed

speckle pattern is the Fourier transform of telescope pupil

autocorrelation of speckles

(in Fourier space)

modulus

(time-averaged intensity)

Knox & Thompson

cross-spectrum, a 2nd order correlation

1974

non-symmetric input

long exposure avg

Labeyrie technique

Knox & Thompson method

mean square of the image transform

modulus of the object transform

autocorrelation of the image transform

phase of the object transform

diffraction-limited image of the object

unambiguous reconstruction of arbitrary shapes but has            ambiguity

+

180\degree

In 1980’s bispectral analysis was found to have higher S/N and be less susceptible to systematic error.

Weigelt & Lohmann

1977-1983

double star simulation

bispectrum modulus

triple correlation

record PSF of object

produce synthetic reference star by shifting the speckle pattern

phase is preserved

Speckle masking/triple correlation theory/bispectral analysis, a 3rd order correlation

deconvolve

  true images

An aside on Lucky Imaging

  • reaches higher resolution than typical seeing
  • does not utilize Fourier analysis
  • not capable of reaching the diffraction limit
  • requires a very large number of  images

http://inspirehep.net/record/823349/plots

Fried

1978

record a large series of images

discard instances of poor resolution

combine the remainder through shift-and-add techniques

Can reach high angular resolution and is often confused with speckle imaging.

Changes in technology

ICCDs

EMCCDs

  • CCD + image intensifier tube
  • tube gating and amplification
  • up to 500kHz
  • lower resolution and low QE
  • interline detector      50% QE
  • CCD + series of HV gain registers
  • + photoelectric events w/ each register
  • greatly amplified signal w/ single readout of the array
  • 2008: Tokovinin published the first speckle imaging results
  • frame transfer, QE > 90%, low readout noise
  • higher S/N than ICCDs
  • 10-100 times faster than a CCD
  • active pixel sensor: amplification and  conversion happens directly on each pixel
  • cheap, less power and lower gain needed
  • higher S/N, 
  • fast readout
  • no clocking the charge across the array
  • further on-chip processing can be added

CMOS (complementary metal–oxide–semiconductor)

EMCMOS

  • each pixel has a series of HV registers
  • + photoelectric events w/ each register

2015: first EMCMOS results reported by Brugière

Publications

Text

blue bars are refereed citations to refereed papers

green bars are non-refereed citations to refereed papers

SAO/NASA ADS “Bumblebee” search: ‘‘speckle’’ - ‘‘speckle noise’’

  • limited to astronomy and refereed
  • removed AO speckle noise references
  • excluded AO and spectroscopic techniques
  • constrained to 1970+ sorted by citation count

This search returned 1,139 papers with 24,181 total citations

release of EMCCDs

& start of large speckle survey programs.

Instrument Programs -

  • often non-hierarchical or bottom-up
  • if successful, use may spread to the broader community
  • many for a specific use and have a finite lifespan
  • limitations of the technology or availability of people
  • many have quiescent phases
  • information is limited to what is publicly available (update your websites)

The following table lists current or recently active major optical speckle imaging programs along with a few IR speckle and lucky imaging instruments and selected other high-resolution programs.

Disclaimer

Title Text

Text

Source: Wikimedia​

Author:

Cmglee

 

DSSI/NESSI/`Alopeke/Zorro

Speckle

  • 10mas/pxl
  • mag limit ~17
  • contrast limit ~8

Wide Field

  • 73mas/pxl

Speckle

  • 18mas/pxl
  • mag limit ~14
  • contrast limit ~6

Wide Field

  • 81mas/pxl

0.011'' @u

0.026'' @832nm

0.025'' @u

0.060'' @832nm

6.7''

60''

19''

56''

Science Programs

40 total proposals

110.04 total nights

(NOAO 2016A to 2018B)

  • Constrain NEA diameters. Image SS objects
  • Determine multiplicity of nearby K and M-dwarfs, does it vary across spectral type?
  • Imaging of brown dwarfs and distant large planets, particularly around M dwarfs
  • Investigate differences in planetary system architectures between multiple vs not (known) multiple host stars
  • Examine long-term RV trends/determine binarity of RV planet hosts.  
  • K2, TESS follow-up
  • Provide an unbiased sample for TESS, so statistical determinations of planet occurrence rates can be made
  • Occultations, transit photometry, pulsar time scales, observe pulsating WDs at high cadence

Some proposals so far:

Recent Science Results

  • optical, NIR imaging of host stars of KOIs
  • ~ 90% of the confirmed and candidate exoplanet hosts
  • separations, PA, and dm for all detected, bound and LoS companion stars.
  • 2297 companions around 1903 primary stars ~ 10% of the observed stars 1+ companions detected w/i 1”
  • correction factors for exoplanet radii caused by the dilution of the transit depth decreases the number of KOI planets with radii smaller than 2 Earth radii by 2% - 23%

Furlan's previous results applied to planets w/ known masses & radii, analyze the effects of a close stellar companion on planetary density.

  • 50 planets orbiting 26 stars in the Kepler field
  • a transit dilution requires the planet radii to be revised upward, decreasing the density of the planet
  • if planet orbits a faint companion star, density may decrease by ~ 3x

The effect of close ~ 0.5” companions of Kepler and K2 planet candidate hosts had on the inferred exoplanet radius distribution.

  • Fulton gap is robust regarding undetected stellar companions
  • gap became broader & shallower when accounting for possible undetected stellar companions
  • core composition of super-Earth and sub-Neptune exoplanets may not have so strong a divide as is suggested initially
  • w/o high-resolution imaging of Kepler and TESS host stars, the exoplanet radius distribution will be incorrectly inferred.

(2018, in press)

Fulton

mini-neptunes

super-Earths

  • Large radius errors originally hid distribution features
  • Fulton gap revealed after CKS (10% stellar radius errors)
  • Accounting for binarity shifts gap in the distribution

brightest companion 1''

brightest companion 2''

Shift from 1.8 to 2.2 

  • increased water/ice vs pure Si rock
R_E
  • 170 KOI companions < 2” using AO, speckle, lucky, or the HST
  • constrained their stellar properties and assessed the probability that the companions are physically bound
  • 60 - 80% of companions < 1” & > 90% of companions < 0.5” were found to be bound
  • assuming the planet is equally likely to be orbiting the primary or secondary, unless they are vetted, nearly half of all Kepler planets may have radii underestimated by an average of 65%.
  • DSSI @ G-S
  • highest-resolution images to date
  • 27 mas
  • imaging from 0.32 to 14.5 au
  • excludes all possible stellar and brown dwarf companions

Future

  • Quad-channel
  • Wave-front sensing
  • Possible near-IR channel?
  • DSSI heritage at the DCT+NPOI
  • novel construction

QWSSI

NEAs

  • sizes
    • radar typically quotes 40% uncertainties
    • albedo/radar size mismatch
  • shapes
    • adapt stellar surface modeling tools
    • light curve inversion/illumination model 

a~2.8AU

d~270km x 80km

(neck~50-65km)

model: Franck Marchis

Phaethon

Dec 2017 ~ 0.07AU

d~6km

Point source PS

Phaethon power spectrum (resolved)

Seeing-limited

Reconstructed

42''

Two-color wide-field speckle reconstruction

from NESSI

  • 0.25'' resolution from 500 frames (20s)
  • compromise b/t angres and contrast
  • Seeing ~ 0.85''

Urban telescope WF speckle

 Wide-field speckle techniques for small, urban telescopes, Nicole M. Granucci, Elliott P. Horch, Southern Connecticut State Univ. (USA)  talk Tues (coming up next actually)[10701-20]

Text

Text

M13

  • astrometry of clusters
  • very early results and little calibration or modelling over the FoV

Reconstructed

Seeing-limited

Abs astrometry residuals

~6-7 mas

4.2 mas

Further improvement possible to obtain ~0.02 pix (~0.4mas)

  • optics, dither, deeper obs

0.05 mag accuracy on aperture photometry

FWHM ~7pix (0.57'')

FWHM ~4pix (0.3'')

MuSIC

  • Davidson, Horch, and Majewski
  • coherent fiber bundles to feed images from the focal plane to a speckle camera
  • diffraction-limited imaging over a wide FoV
  • analogous to integral field unit spectrograph
  • simultaneous diffraction-limited speckle images for each object
  • could go into place at the WIYN

Speckle imaging through a coherent fiber bundle, James W. Davidson, University of Virginia (USA), et al.  poster Tues [10701-105]

Conclusions

  • a brief history and introduction has attempted to set the stage for the current research
  • highlighting the relevance of high angular resolution imaging to exoplanet and stellar research
  • high demand for speckle imaging observing
  • development of future community instruments
  • small space telescopes, optimized for large surveys of the sky, like TESS and GAIA, perform relatively poorly at high-contrast, sub-arcsecond resolution where speckle imaging excels
  • a cost-effective, efficient means to reach the diffraction limit with single aperture telescopes

Selected References -full list in manuscript

Brown, R. H. and Twiss, R. Q., Nature 177, 27{29 (Jan. 1956).
Hanbury Brown, R., Davis, J., and Allen, L. R., MNRAS 137, 375 (1967).
Labeyrie, A., A&A 6, 85 (May 1970).
Knox, K. T. and Thompson, B. J., ApJ 193, L45{L48 (Oct. 1974).
Weigelt, G., Scientifc Importance of High Angular Resolution at Infrared and Optical Wavelengths, Ulrich, M. H. and Kjaer, K., eds., 95{114 (1981).
Weigelt, G., Lowell Observatory Bulletin 9, 144{152 (1983).
Weigelt, G. P., Optics Communications 21, 55{59 (Apr. 1977).
Lohmann, A. W., Weigelt, G., and Wirnitzer, B., Appl. Opt. 22, 4028{4037 (Dec. 1983).

Fried, D. L., Journal of the Optical Society of America (1917-1983) 68, 1651–1658 (Dec. 1978).
Horch, E. P., Veillette, D. R., Baena Galle, R., Shah, S. C.,O'Rielly, G. V., and van Altena, W. F., AJ 137, 5057{5067 (June 2009).

Brugière, T., Mayer, F., Fereyre, P., Gu´erin, C., Dominjon, A., and Barbier, R.,  Nuclear Instruments and Methods in Physics Research A 787, 336–339 (July 2015).
Scott, N. J., Howell, S. B., Horch, E. P., and Everett, M. E., PASP 130, 054502 (May 2018).
Hofmann, K.-H. and Weigelt, G., A&A 278, 328-339 (Oct. 1993).
Law, N. M., Mackay, C. D., and Baldwin, J. E.,  A&A 446, 739{745 (Feb. 2006).
Tokovinin, A. and Cantarutti, R., PASP 120, 170 (Feb. 2008).
Andor, CCD, EMCCD and ICCDComparions & Minimizing Clock Induced Charge.
Howell, S. B., Everett, M. E., Sherry, W., Horch, E., and Ciardi, D. R., AJ 142, 19 (July 2011).

Furlan, E., Ciardi, D. R., Everett, M. E., Saylors, M., Teske, J. K., Horch, E. P., Howell, S. B., van Belle, G. T., Hirsch, L. A., Gautier, III, T. N., Adams, E. R., Barrado, D., Cartier, K. M. S., Dressing C. D., Dupree, A. K., Gilliland, R. L., Lillo-Box, J., Lucas, P. W., and Wang, J.,  AJ 153, 71 (Feb. 2017).
Furlan, E. and Howell, S. B., AJ 154, 66 (Aug. 2017).
Teske, J. K., Ciardi, D. R., Howell, S. B., Hirsch, L. A., and Johnson, R. A.,  ArXiv e-prints (Apr. 2018).
Fulton, B. J., Petigura, E. A., Howard, A. W., Isaacson, H., Marcy, G. W., Cargile, P. A., Hebb, L., Weiss, L. M., Johnson, J. A., Morton, T. D.,Sinuko , E., Cross eld, I. J. M., and Hirsch, L. A., AJ 154, 109 (Sept. 2017).
Hirsch, L. A., Ciardi, D. R., Howard, A. W., Everett, M. E., Furlan, E., Saylors, M., Horch, E. P., Howell, S. B., Teske, J., and Marcy, G. W., AJ 153, 117 (Mar. 2017).

Matson, R. A., Howell, S. B., Horch, E. P., Everett, M. E., ArXiv e-prints (May. 2018)

Backup Slides

Open to the community

  • NOAO proposal process
  • NESSI - WIYN@KPNO
  • `Alopeke - Gemini-N
  • DSSI - Gemini-S
  • Transitioning from block queue operation to Facility Instrument status

NPP & internship opportunities: see me for details

Detection percentage as a function of projected angular separation for the 883 nm speckle image of TRAPPIST-1. The curve is the 5σ detection limit from our image convolved with the detection likelihood (see the text). The result eliminates all companions in the blue region at separations of 0.32–17 au for the observed contrast ratios. Numbers on the plot represent the delta magnitude and spectral type limits at the corresponding points. For example, all companions earlier than T7 are eliminated to an inner separation of ∼8 au.

observed

bound (simulated)

line-of-sight (simulated)

K2 binaries detectable with DSSI-

Matson et al. 2018 (submitted)