NIRCam: Wavefronts, Images, and Science Marcia Rieke NIRCam PI STScI June 7, 2011

What’s NIRCam? NIRCam is the near-infrared camera (0.6-5 microns) for JWST –Refractive design to minimize mass and volume –Dichroic used to split range into short (  m) and long (  m) sections –Nyquist sampling at 2 and 4  m –2.2 arc min x 4.4 arc min total field of view seen in two colors (40 MPixels) –Coronagraphic capability for both short and long wavelengths NIRCam is the wavefront sensor –Must be fully redundant –Dual filter/pupil wheels to accommodate WFS hardware –Pupil imaging lens to check optical alignment 2 View of the Goddard clean room

Design Overview Fully redundant with mirror image A and B modules Refractive optical design Thermal design uses entire instrument as thermal ballast ; cooling straps attached to the benches SIDECAR ASICs digitize detector signals in cold region Uses two detector types – short wavelength HgCdTe and long wavelength HgCdTe (this one is same as used on NIRSpec & FGS) Focus and alignment mechanism Coronagraph occulting masks First fold mirror Collimator lens group Dichroic beamsplitter Long wave filter wheel assembly Long wave camera lens group Long wave focal plane housing Short wave filter wheel assembly Short wave fold mirror Pupil imaging lens assembly Short wave focal plane housing Light from Telescope Short wave camera lens group

4 2 Channels Per Module Each module has two bands (0.6 microns to 2.3 microns and 2.4 microns to 5 microns)  Deep surveys will use ~7 wide band filters (4 SW, 3 LW, 2x time on longest filter)  Survey efficiency is increased by observing the same field at long and short wavelength simultaneously SW pixel scale is 0.032”/pix; long is 0.064”/pix Long wavelength channelShort wavelength channel Module A Module B 2.2’

NIRCam as a Wavefront Sensor NIRCam provides the imaging data needed for wavefront sensing. Two grisms have been added to the long wavelength channel to extend the segment capture range during coarse phasing and to provide an alternative to the Dispersed Hartmann Sensor (DHS) Alignment steps include: –Telescope focus sweep –Segment ID and Search –Image array –Global alignment –Image stacking –Coarse phasing –Fine phasing uses in and out of focus images (similar to algorithms used for ground base adaptive optics) 5 Coarse phasing w/DHS After coarse phasing Fully aligned Fine phasing First Light After segment capture DHS at pupil Spectra recorded by NIRCam

Following the Light: 1st Stop is the FAM FAM = Focus Adjust Mechanism Pick-off mirror (POM) is attached to the FAM; POM has some optical power to ensure that the pupil location does not move when FAM is moved Ensures correct mapping of NIRCam pupil onto telescope exit pupil 6  FAM being prepped for connector installation. POM Assembly Linear Actuators Sensor & Target Assy Prototype  POM

Following the Light: 2 nd Stop is the Collimator Transmits over entire 0.6 – 5.0 micron band Most of the optical power is in the ZnSe lens with the other two largely providing color correction Excellent AR coatings available 7 LiF BaF 2 ZnSe Light One of the flight collimator triplets

Following the Light: 3 rd Stop is the Beam Splitter LW beam is transmitted, SW beam is reflected –DBS made of Si which greatly reduces problems with short wavelength filter leaks in LW arm Coatings have excellent performance 8 Flight beam splitters

Following the Light: 4 th Stop is the Filter Wheel Assembly (FWA) Dual wheel assembly has a pupil wheel and a filter wheel, twelve positions each, in a back-to-back arrangement Filters are held at 4 degree angle to minimize ghosting Pupil wheel includes an illumination fixture for internal flats and for use with special alignment fixtures Wheels are essential for wavefront sensing as they carry the weak lenses and the dispersed Hartmann sensor 9 One of the flight LW pupil wheels

Bandpass Filters 10 Filters have names indicating wavelength (100x microns) and width (Wide, Medium, or Narrow) Transmission of flight W filters.

Medium & Narrow Filters Isolate Spectral Features 11 “M” filters useful for distinguishing ices, brown dwarfs.

Following the Light: 6 th Stop is the Camera Triplet Camera triplets come in two flavors for the two arms of NIRCam Using same AR coatings as on collimator because they give good performance and it is cheaper to use the same coatings everywhere 12 Operates over SW 0.6 – 2.3 microns Operates over LW 2.4 – 5.0 microns

Following the Light: Last Stop is the Focal Plane Assembly (FPA) NIRCam has two types of detectors: 2.5-  m cutoff and 5-  m cutoff HgCdTe (5-  m same as NIRSpec, FGS) Basic performance is excellent with read noise ~7 e- in 1000 secs, dark current 80% Other performance factors such as latent images and linearity are excellent 13 LW FPA w/ one 2Kx2K readied for performance tests SW FPA with four 2kx2K arrays Qual focal plane assembly mated to ASICs.

Latent Testing of Flight Arrays 14 Illuminate strongly, remove illumination, reset, read non- destructively. DARK Time Signal Repeat 5x All IR arrays suffer from latent images after exposure to light An issue for NIRCam because there will be an over-exposed star in every long exposure 1 ADU = 4 e-

15 Following the Light: Optional Coronagraph Pupil Wheel Collimator Optics Camera Optics NIRCam Pickoff Mirror Telescope Focal Surface Coronagraph Image Masks Coronagraph Wedge JWST Telescope Not to scale NIRCam Optics Field-of-View FPA Coronagraph Image Masks Without Coronagraph WedgeWith Coronagraph Wedge Not to scale Filter Wheel Calibration Source Collimator Optics Camera Optics Wedge FWHM c = 0.58” (4 4.6  m) FWHM c = 0.27” (4 2.1  m) = 0.82” FWHM = 0.82” (6 4.3  m) = 0.64” FWHM = 0.64” (  m) FWHM = 0.40” (6 2.1  m)

Lyot Stops Lyot stop for 6 /D spot occulters Lyot stop for 4 /D wedge occulters Mask clear regions (white) superposed on JWST pupil (grey) Throughput of each is ~19%. Masks similar to those defined by John Trauger & Joe Green

Bench Holds it all Together 17

NIRCam’s Role in JWST’s Science Themes 18 young solar system Kuiper Belt Planets The First Light in the Universe: Discovering the first galaxies, Reionization NIRCam executes deep surveys to find and categorize objects. Period of Galaxy Assembly: Establishing the Hubble sequence, Growth of galaxy clusters NIRCam provides details on shapes and colors of galaxies, identifies young clusters Stars and Stellar Systems: Physics of the IMF, Structure of pre-stellar cores, Emerging from the dust cocoon NIRCam measures colors and numbers of stars in clusters, measure extinction profiles in dense clouds Planetary Systems and the Conditions for Life: Disks from birth to maturity, Survey of KBOs, Planets around nearby stars NIRCam and its coronagraph image and characterize disks and planets, classifies surface properties of KBOs NIRCAM_X000 Inflation Forming Atomic Nuclei Recombination First Galaxies Reionoization Clusters & Morphology Modern Universe NIRCam Quark Soup Inflation Forming Atomic Nuclei Recombination First Galaxies Reionoization Clusters & Morphology Modern Universe NIRCam Quark Soup

NIRCam Team Observing Plan Team has embraced the JWST Science Themes and is divided into an Extragalactic Team, a Star Formation Team, and an Exo-planet-Debris Disk Team. Use of all instruments and collaboration with the other instrument team is assumed. 19

20 NIRCam Team Theme Groups Extragalactic Leader: Daniel Eisenstein Deputy: Alan Dressler Members: Marcia Rieke Stefi Baum Laura Ferrarese Simon Lilly Don Hall Chad Engelbracht Christopher Wilmer Star Formation Leader: Michael Meyer Deputy: Tom Greene Members: Klaus Hodapp Doug Johnstone Peter Martin John Stauffer Tom Roellig Erick Young Doug Kelly Karl Misselt Massimo Robberto Dan Jaffe Exoplanets & Disks Leader: Chas Beichma n Deputy: Don McCarthy Members: René Doyon Tom Greene George Rieke Scott Horner John Trauger John Stansberry John Krist Kailash Sahu

Extragalactic Program 21 NIRCam Team will concentrate on z> 10 = deep survey but lower zs also important -- Survey details TBD but will take data using 6 or 7 filters in SW/LW pairs so 3 or 4 settings will be needed -- likely will spend at least ~15 hours setting -- will collaborate w/ NIRSpec, MIRI, FGS teams NIRCam footprint compared to Goods, UDF Deep Survey Questions What is the luminosity function and size/SB distributions of z>10 galaxies? Is the SF only in the core or spread over the halo? Is there any evidence for cooperative formation, mediated by radiation or reionization? What are the halo masses of these galaxies? What can we learn of reionization from these galaxies?

Sensitivity 22 Finlator et al (~20ksecs) Z=10 M=4x10 8 Msun Z=5 M=4x10 9 Msun “Deep” NIRCam will have the sensitivity to find z~10 galaxies and low mass galaxies at lower redshifts.

Angular Resolution NIRCam Surface Brightness Limit 3-sigma/pix WFC3 JWST 2  m 3.6  m

Star Formation Program Making of Stars and Planets:Testing the Standard Model(s) 1) What physical variables determine the shape of the IMF? 2) How do cloud cores collapse to form isolated protostars? 3) Does mass loss play a crucial role in regulating star formation? 4) What are the initial conditions for planet formation? 5) How do disks evolve in structure and composition? 24 Program takes advantage of JWST’s high sensitivity in the near- and mid-infrared Program will be executed in collaboration with the MIRI and TFI Teams

More on Star Formation 25 Do any of these 8 parameters vary with initial conditions of star formation? From Bastian, Meyer, & Covey (2010) Use imaging of clusters to -- determine IMF to ~ 1M Jupiter -- measure cluster kinematics -- find variable YSOs Will want both high and low metallicity targets Will need multi- color images

Exo-planet and Debris Disk Program Program is aimed at characterizing exo-planets and debris disks, not at finding them JWST’s angular resolution and 1-5 micron capabilities are keys Will be done in collaboration with MIRI and TFI teams NIRCam has three sets of features to enable this program: –Coronagraphic masks and Lyot stops –Long wavelength slitless grisms (installed to support wavefront sensing but useful for science) Because the SW side can also be readout when using one of the grisms, jitter can be tracked directly. –Internal defocusing lenses for high precision photometry = transits (installed for wavefront sensing, only available in the short wavelength arms) 26

Coronagraphic Capabilities: Ground and Space 11  m 4.4  m spot TFI 4.4  m 1.65  m

GTO Imaging Program Large scale surveys of 100s of young stars best left to ground-based AO and/or JWST/GO programs Small targeted surveys take advantage of various criteria to enhance probability of success: –Faint, young, host stars difficult for ground base AO, e.g. M stars with sensitivity to M Jup at AU. –Debris disk systems suggestive of planets –Face-on systems offer 10-20% improved probability of detection (Durst, Meyer, CAB) –High metallicity –Systems with strong RV –Monitoring for temporal changes Majority of GTO program will be imaging and spectra to characterize known systems –Complete spectra (1-5  m w NIRCam and <10  m with MIRI) to compare w. physical models –Search for additional planets –Refine orbits Eccentricity Inclination Prob Detect Log Mass (M Jup ) Orbit (AU) 10 40

29 Transits With NIRCAM Lenses introduce 4,8,12  of defocus to spread light over many hundreds of pixels compared with 25 pixels when in-focus –Reduce flat-field errors for bright stars 5<K<10 mag –Max defocus is 12  ultra-high precision data for bright transits Diffused images (weak lenses) or spectrally dispersed images (grism) reduce brightness/pixel by >5 mag. K=3-5 mag stars not saturated. LED Pupil

30 Fine Phasing Images from ETU: Samples of Defocussed Images Useful for Transits

Transit Spectroscopy If an instrument+telescope combination is sufficiently stable, spectra of a transiting planet’s atmosphere can be obtained. Both emission spectra and transmission spectra can be obtained. HST and Spitzer have produced such data. This is likely to be a very powerful technique for JWST. Whether NIRSpec or NIRCam will be best will depend on systematics that may be difficult to predict 31 Will concentrate on a limited number of interesting targets NIRCam grism range very useful!

NIRCam has been designed to take advantage of JWST’s large and cold primary mirror… and the NIRCam team will scratch the surface of several sciences areas BUT most of the work will done by the general observing community! NIRCam Cheat Sheet and more at And at 32