E-ELT VLT HARMONI – the first light integral field spectrograph for the E-ELT Niranjan Thatte On behalf of the HARMONI consortium Florence - 29 June 2013
Outline Capabilities of HARMONI AO science + modes Integral field + AO: an ideal marriage Acquisition time / observing efficiency Florence - 29 June 2013
Outline Capabilities of HARMONI Difference in way of carving up parameter space. Spatial pixel scales (and FoV) Spectral coverage and resolving power No ADC in science path AO science + modes Bright objects – SCAO: solar system targets (ref to Fraser’s talk), high contrast, type of coronagraph for no ADC, serendipitous faint object science Faint objects – LTAO, optimal spaxel scale Integral field + AO: an ideal marriage? Strong variation of PSF with wavelength PSF parameterisation Need for PSF reconstruction Acquisition time / observing efficiency Florence - 29 June 2013
Modular Construction Florence - 29 June 2013
For extended sources & optimal FoV For optimal sensitivity (faint targets) Best combination of sensitivity and spatial resolution 40 mas 20 mas10 mas Highest spatial resolution (diffraction limited) 4 mas 7 7 f f 2.5” × 5” 5” × 10” 1.25” × 2.5” 0.5” × 1.0” 128 × 256 spaxels at all scales
Wavelength Ranges & Resolving Powers BandsR V+R, I+z+J, H+K~4000 I+z, J, H, K~10000 Z, J_high, H_high, K_high~20000 Exploring adding simultaneous V-K coverage at R~ Re-assessing the need for high spectral resolving power at visible wavelengths (< 0.8 micron) Florence - 29 June 2013
Integral field spectrograph does not require ADC, as each narrow wavelength channel can be re-aligned in software to compensate for atmsopheric refraction Blurring within long exposure cannot be compensated post-facto, but improving detector performance allows many shorter exposures to be co-added without penalty. No ADC required Florence - 29 June 2013
Wavelength Ranges & Resolving Powers Band min [µm] max [µm] [Å/pixel] R H+K I+z+J V+R K H J I+z R V K high H high J high z R high V high Florence - 29 June 2013
Different Flavours of AO SCAO GLAOLTAO Or even degraded GLAO (NGS only) !!! Florence - 29 June 2013
Planets & Stars Stars & Galaxies Galaxies & Cosmology Contemporary Science Florence - 29 June 2013
5mas per pixel input10 mas HARMONI scale20 mas HARMONI scale40 mas HARMONI scale100 mas scale on VLT Florence - 29 June 2013
High-z Ultra-luminous IR Galaxies Survey 50 Spitzer candidate ULIRGs 1<z<2.5 Detect & characterise nuclear disks & rings Measure shocks, winds, interaction with IGM Measure dynamical masses Distribution of dust Modes of star formation Measure rotation, masses, dust content, stellar pops & FP Requires: diffraction limited R > 4000 spectra, spaxels . H in z=2 ULIRG Florence - 29 June 2013
Optimal Spaxel Scale Florence - 29 June mas is optimal spaxel size for LTAO point sources Need to re-compute as a function of wavelength using 39m E-ELT, latest telescope PSFs, and HARMONI design
SCAO Provides significantly higher Strehl on-axis (70% v/s 48.5% in K band, median seeing) De-risk LTAO (complex, untested on sky) Key science themes –Characterisation of exo-planets detected by SPHERE / GPI –Detailed studies of outer Solar System (Jovian moons, Neptune, Uranus => see talk by Fraser Clarke Fri morning) –Serendipitous targets (high z galaxies, need ancillary data!) Florence - 29 June 2013
Spectroscopy at the Diffraction Limit Florence - 29 June mas pupil size (grating physical size) 4mas anamorphic pupil size (ignoring diffraction) Instrument designed for coarse (seeing-limited) spaxels gives excellent performance at diffraction limited scales, even including slit diffraction.
High? Contrast with HARMONI M4 actuator density similar to NACO & SINFONI on VLT, expect similar peak Strehl to SINFONI (~70% in K) At these Strehl’s, benefit of coronagraph as a diffraction suppression system remains to be demonstrated ADC would be needed to gain from coronagraph. Apodizer, followed by large field stop (many λ /D) might work better. Occulting bar to get around persistence / duty cycle issues Looking into prism disperser for low R, wide band use. ADI type operation possible, but co-rotate occulting bar? Florence - 29 June 2013
PSF effects Strong variation of PSF with wavelength Florence - 29 June 2013 Parameterize PSF (axi-symmetric) with a few parameters, which vary smoothly with wavelength => see Poster by S. Zieleniewski Allows quick computation of PSF at any wavelength, with high accuracy.
PSF Reconstruction Florence - 29 June 2013
10€ / second! Amortised cost of E-ELT 10x larger than VLT Need to optimise acquisition time / open-shutter efficiency of science instrument Eliminate –Background sky exposures –Need for telluric calibrators (on-sky) –PSF calibration observations –Blind offsets from reference stars (don’t use long slits!!) –Hunting for tip-tilt stars / NGS reference stars Florence - 29 June 2013
Field of View: size & sampling Variable sky & PSF advantage to avoid mosaicing Typical single objects at z>1 128 x 20mas for short dimension of IFU Large objects (QSO hosts) or diffuse emission & stellar pops studies largest possible FoV Linear size of spaxel (pc) Linear size of FoV (kpc) Florence - 29 June 2013
The E-ELT Florence - 29 June 2013
Choices of LGS Asterism Florence - 29 June 2013
New Developments (post Phase A) Smaller telescope Addition of SCAO capability Visible cameras for all spectrographs (32000 spectra at all wavelengths) Fixed format visible camera (TBC) Explore simultaneous large wavelength coverage at low resolving power Emphasis on high contrast performance Florence - 29 June 2013