Interest amongst the Mauna Kea community?

To asses such questions, a preliminary and informal meeting was held on March 16^th and 17^th at CFHT's headquarters in Waimea. Participants included members from CFHT, Keck, Gemini, IfA (UH), NOAO and NASA. The goal of the meeting was twofold. First, we wanted to see if collaborations would be possible and if OHANA would be interesting the the various observatories. Second, we wanted to pinpoint the difficulties of such a project and the possible scientific objectives that would be unique to such an array.

The answer to the first question was a definite yes, and this meeting really turned into a kick-off meeting. The minutes of the meeting are available on the OHANA web document repository⁴. A committee was formed at this meeting with the objective to coordinate and organize its member institutions in the planning and operations of OHANA until a more formal project structure is in place. The OHANA committee would also communicate plans and activities to the astronomy community, and serve as a contact point for potential additional partners who would wish to participate in OHANA. The initial institutional participation to the OHANA committee consists of:

• Canada-France-Hawaii Telescope Corporation (O. Lai - chairman)
• Départment Spatial, Observatoire de Paris-Meudon (Pierre Léna, Guy Perrin)
• Gemini Observatory (François Rigaut)
• University of Hawaii, Institute for Astronomy (François Roddier)
• W.M. Keck Observatory (Peter Wizinowich)
• National Optical Astronomy Observatories (Steve Ridgway)

The second question proved harder to answer because even though many parts of the array already exist (the "collectors", and such devices as fiber couplers), such an all-fiber interferometer has never been built, and there are some site specifics details that need to be considered (due to building restrictions on top of Mauna Kea, existing buildings, such as CFHT's lower Coudé room, could host the delay lines; the existing ducts - for power and optical fibers - could possibly be used to route our fibers; etc).

However, such an interferometer opens up new and exciting scientific horizons that are quite complimentary to existing very high angular resolution interferometers. On the one hand, nanoradians resolutions achievable only with VLBI techniques will now be open the optical/IR domain. On the other hand, OHANA will provide an increase in resolution with respect to interferometers such as VLTI and KeckI (Figure 2). For example in the case of Mauna Kea, three different orders of magnitudes of resolutions will be available:

 

$$\longrightarrow$$ 8 - 10 meters 50 mas

$$\longrightarrow$$ KeckI 5 mas⁵

$$\longrightarrow$$ OHANA 0.5 mas

KeckI and VLTI will answer many questions in many domains, but OHANA will make it possible to refine the models that will be developed to fit their observations with even larger baselines.

 

Figure 2: Left: uv plane coverage for the OHANA array for a source at $50^{\circ}$ declination for 8 hours of tracking (super-synthesis). Right: Associated PSF at 2.0 $\mu$m; note that the scale on the axes is in milliarcseconds. For reference, the declination of Markarian 231, one of the brightest Ultra Luminous Infrared galaxies is $+56^{\circ}52'28''$.

For example, in the case of Ultra Luminous InfraRed Galaxies (ULIRGs), adaptive optics allows to probe the Narrow Line Region (NLR) and the close environment of the nucleus. KeckI and VLTI will allow to resolve the molecular torus and explore the Broad Line Region (BLR), while OHANA will allow to start exploring the environment of the accretion disk and may be resolve the sources that are responsible for the broad lines.