MIDI design, performance, operations, and science

Markus Schöller (INS)

Why do we use interferometers?

Objects Single Telescope Interferometric Fringes

Angular Resolution: ~ /D ~ /B

Small starSmall star

Big starBig star

MIDI in the VLTI lab

IRIS

FINITO

MIDI in the VLTI lab

The MIDI cold optics

Coaxial beam combination

MIDI lab fringes

The VLTI Telescopes

VLTI Optical Layout

Configurations

The uv-plane

Where do we sample the spatial frequencies?

If you have never tried to FFT-1…

Phase is essential for interferometric imaging

Coming next: MATISSE

MATISSE will provide:

•Four telescope beam combination (six baselines, four closure phases)•L/M/N band•Roughly identical sensitivity•R~30-1000 (L/M), R~30-200 (N)

MIDI design, performance, operations, and science

Christian Hummel (USD)

MIDI Publications

• Nature:– Jaffe et al. 2004 The central dusty torus in

the active nucleus of NGC 1068– Van Boekel et al. 2004 The building blocks of

planets within the terrestrial region of proto-planetary disks

• A&A (72), MNRAS (2), ApJ (9), Icarus (2)

Source: ESO Telescope Bibliography at http://telbib.eso.org

VLTI publications

From: Basic ESO Publication Statistics, 2012, prep. by Grothkopf & Meakins

OLBIN

Science with MIDI

Jaffe et al.

van Boekel et al.

Zhao-Geisler

Science Operations

• VLTI UT scheduled in blocks• Night astronomer selects telescopes from quadruplets• OBs selected from MIDI and AMBER queues• LST intervals allow user to achieve specific projected• Science targets interleaved with interferometric

calibrators

Operational efficiency

MIDI

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Acquisition with Coudé guide stars

Instrument modes

• HIGH_SENS: no photometric channels, separate observation for photometry– GRISM: R=320– PRISM: R=30

• SCI_PHOT: simultaneous photometry, chopping– PRISM GRISM

Spectrum extraction and sky windows

Dispersed interference fringes

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OPD

Courtesy: Th. Ratzka

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Fringe scanning

SCI_PHOT mode (simultaneous chopping)

Visibility amplitude calibration

Calibrator:HD 50778D = 3.8 mas

Calibrator selection

Jean-Marie Mariotti Center (JMMC) tools

Visibility amplitudes of a binary source

Observing with MIDI

• OK with seeing up to 1.5” (limited by MACAO/STRAP)• SCI-CAL or CAL-SCI-CAL sequences in concatenations

(p2pp3)• 25 minutes execution time per OB independent of target• Simple model fitting only, spatial resolution 15 – 130 mas• Resources

– http://www.eso.org/sci/facilities/paranal/instruments/midi/ (MIDI page)– http://www.eso.org/~chummel/midi/midi.html (data reduction)– http://home.strw.leidenuniv.nl/~nevec/MIDI/index.html (software)– http://olbin.jpl.nasa.gov/news/index.html (Long Baseline Interferometry)