‘OHANA Towards kilometric infrared arrays Visions for InfraRed Astronomy Paris March 21, 2006 Guy Perrin (+ many others including Pierre)

VLTI Very Large Telescope Interferometer: 4 x 8 m telescopes + 4 x 1.8 m telescopes Maximum baseline: 200 m

NGC 1068 at different spatial 12 µm (Poster by Poncelet et al.) Based on VISIR data in Burst Mode analyzed in the speckle way

First interferometric measurements of an AGN at VLTI NGC 8-13 µm with MIDI (Jaffe et al. 2004)

The putative torus spatially and spectrally resolved (Poncelet, Perrin & Sol, 2006)

Active Galactic Nuclei scenario AGN 2 like NGC 1068 AGN 1

NGC 4151 (Seyfert 2.2 µm with Keck : the compact core is not resolved (résolution = 5 mas) NGC 4151 (Swain et al. 2003) First interferometric measurements of an AGN at Keck

Angular resolution B = 200 m  m   (mas)       100 Mpc

Link the 7 largest Mauna Kea telescopes with infrared single-mode fibers 800 m synthesized pupil No immediate competition ‘OHANA (Optical Hawaiian Array for Nanoradian Astronomy) Link CAT and the 3.60 m in La Silla (2 nd year of PhD program of V. Coudé du Foresto) Low cost VLTI proposal (1995)

Goals Demonstrate the potential of fibers for beam propagation in kilometric arrays Demonstrate the sensitivity of interferometers that combine large apertures, AO correction and single-mode fibers -> fibers transmit 60-95% of the light over a 1 km in the near-infrared Go to a few 0.1 mas angular resolution in the near-infrared Demonstrate the astrophysical potential of the instrument Build ‘OHANA and make it work

Detector Single-mode fibers Beam combiner Delay line Injection module OA Injection OA Injection ‘O H A N A

FLUOR (Fiber Linked Unit for Optical Recombination) Partnership with Le Verre Fluoré

Cleaning beams with single-mode fibers Trade phase (coherence) fluctuations against intensity fluctuations which can be easily measured Requirement: focus light in a tiny core  adaptive optics core ~ 5 µm

The gain (Perrin et al. 1998) (Benson et al. 1993)

Detector Single-mode fibers Beam combiner Delay line Injection module OA Injection OA Injection ‘O H A N A

Injection tests ( ) Fibers Injection moduleAdaptive Optics Gemini North Cassegrain focus

Injection tests Injection tests at: CFHT (July 2002)(K)(3 nights) Keck (December 2002)(K)(2 half nights) Gemini North (July 2003)(H)(2 half nights) Results: best injection efficiency CFHT: 20%(24% theoretical) best injection efficiency Keck: 50% (60% theoretical) Green light to proceed with first baselines

Interferograms at different wavelengths form at Different zero optical path difference Chromatic differential dispersion No differential dispersion With differential dispersion

The starting point Coudé du Foresto, Perrin & Boccas (1995) Coupler (a few meters of fibers) 77 m long fibers

‘OHANA fibers: example in the K band 2x300 m fluoride glass fibers No differential dispersion !!! Kotani et al. (2005, K) Vergnole et al. (2005, J&H)

First tests with the two Kecks

CFHT - Gemini (159 m) Gemini - UKIRT (188 m) CFHT - UKIRT (338 m) Keck I - Keck II (85 m) Subaru - Keck II (214 m) Keck II - IRTF (251 m) Subaru - IRTF (454 m) VLTI

Set-up 2 x 300 m cables Equivalent to a 500 m interferometer

First fringes on 107 Herculis (June 2005) Perrin et al. (2006)

First fringes on 107 Herculis (June 2005) Perrin et al. (2006)

First (technical) results Fringe contrast: 25% on 107 Herculis because of dispersion in adaptive optics 75% in autocollimation Transmission : 0.5% on 107 Herculis: cloudy night, 2 magnitudes of V potentially 4% with the current system and 10% if improved to be compared to the 1% of Keck (the same order as VLTI) We have been granted with a science night (NASA + Keck time) : May 8, 2006

Elasticity of fibers ~ 0.1-1%  1 µm amplitude every millimeter Measured amplitude: 3 µm Sources: motors, fans, oil and glycol hoses running in cable wraps … Solutions: damping (insulating fibers) servoing of fiber lengths A difficulty: fibers are very efficient antennas for vibrations

What’s next ?

CFHT - Gemini (159 m) Gemini - UKIRT (188 m) CFHT - UKIRT (338 m) Keck I - Keck II (85 m) Subaru - Keck II (214 m) Keck II - IRTF (251 m) Subaru - IRTF (454 m) VLTI

The Gemini - CFHT baseline (156 m)

Set-up in the Coudé room at CFHT GEMINI CFHT

The ‘OHANA stream

Optical ALMA L eap for E xtraordinary N anoradian A stronomy ´

Some more technology required Fibered incremental delay line opd modulator (±100 µm) Long stroke delay line (several 100 m) Hollow Photonic Crystal Fibers