E-ELT
description
Transcript of E-ELT
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E-ELT VLT
HARMONI – the first light integral field
spectrograph for the E-ELT
Niranjan ThatteOn behalf of the
HARMONI consortium
Florence - 29 June 2013
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Outline
Capabilities of HARMONI
AO science + modes
Integral field + AO: an ideal marriage
Acquisition time / observing efficiency
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Modular Construction
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For extended sources &
optimal FoV
For optimal sensitivity
(faint targets)
Best combination of sensitivity and spatial resolution
40 mas
20 mas 10 mas
Highest spatial
resolution (diffraction
limited)
4 mas
7f
2.5” × 5”
5” × 10”
1.25” × 2.5”
0.5” × 1.0”
128 × 256 spaxels at all scales
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Wavelength Ranges & Resolving Powers
Bands RV+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~500-1000
Re-assessing the need for high spectral resolving power at visible wavelengths (< 0.8 micron)
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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
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Different Flavours of AO
SCAOGLAO LTAO
Or even degraded GLAO (NGS only) !!!Florence - 29 June 2013
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Planets & Stars
Stars & Galaxies
Galaxies & Cosmology
Contemporary Science
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5mas per pixel input 10 mas HARMONI scale 20 mas HARMONI scale 40 mas HARMONI scale 100 mas scale on VLT
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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 & FPRequires: diffraction limited R > 4000 spectra, spaxels 5-40mas. @ 0.5 - 2.5.
H in z=2 ULIRG
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Optimal Spaxel Scale
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0 20 40 60 80 100 120 1400
1000
2000
3000
4000
5000
6000LTAO sensitivity @ R=4000, K=23, 42m E-ELT
Spaxel size [mas]
Exp
tim
e f
or
SN
R=
10
Analysis from Phase A (S. Arribas)
• 15-20mas 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
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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!)
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Spectroscopy at the Diffraction Limit
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56mas 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.
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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?
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PSF effects• Strong variation of PSF with wavelength
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• 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.
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PSF Reconstruction
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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
starsFlorence - 29 June 2013