Michigan/MIKE Fiber System (MMFS) – Update Apr 2005

On Telescope: 27 science nights since start 2004A 2 dedicated engineering nights

Installation: Process now well documented; takes 3-4 hrs plus overheads (MMFS to MIKE tricky in 1 day)

-- Remove MIKE/guider/baffles on Clay -- Install MMFS -- Remove MIKE optics/rotate CCDs on MIKE -- Replace MIKE on platform -- Install MMFS fiber shoes into MIKE -- Prepare for observing (blocking filter, grating tilts, etc.) -- Focus, calibration, data, observe

Still require a full web-based documentation of process.

Issues

-- Fiber tips still fail about 1 per night; easy to repair. -- Blue CCD developed high dark counts starting in Oct 2004 (acceptable), through Dec/Jan 2004/05 (unacceptable, loss of nights), Feb 2005 (even worse one lost night).

-- High dark with odd, quasi-concentric pattern -- Visible pattern of contamination on CCD with same pattern.

-- IT suggested O2 + heat flood; this solved the problem.

2400 sec image

Dark rate ~ 0.5 e/sec/pix

-- Very few spare fibers; more needed.

-- More blocking filters to isolate more individual orders (Ca IR triplet; H-alpha; Mg complex)

-- Arc control system was flaky (inconsistent operating voltage on HV lamps). New system installed based on MOE controller/GUI and MMFS lamp support system on the secondary.

Operations

Efficiencies: For dSph kinematic studies we can compare. [1-2 km/s to V=20.5-21.0 red giants]

VLT – 10 stars per hr (+ high res spectra) MMT – 8 stars per hr (based on recent run; some light leak problems that should be fixed soon). MMFS – 25 stars per hour

Includes all overheads, standards, etc.

Explicit overheads: 20-45 min for fiber changes 5 min per velocity of abund standard 2 min per arc

MMFS: Data

• Sculptor red giants

• 5130-5190 A (Mg complex)

• V = 20.5-19.0

• ET = 2.5 hours

1991, 1992, 1993, 1994, 2002

Samples are substantially bigger:

1991, 1992, 1993, 1994, 2002 3 hours in October 2004

And growing rapidly:

• Carina red giant

• R ~ 18000

• V ~ 19.6

• CCF precision

~ 1 km/s

Velocity errors can be managed (14% repeat observations), even in faint, metal-poor stars.

. . . The dispersion is sensitive to excess velocity errors only when these errors become large compared to the dSph’s overall dispersion . . . (Kleyna etal. 2005, regarding the history of Sextans velocity error estimates).

Galaxy Ntarg Nobs MV

Sculptor 3200 1068 +0.5Fornax 5000 560 -0.7Carina 1600 1560 +0.0Leo I 1500 -- -1.5Sextans 2200 1190 +0.3Draco 1200 -- +1.0

MMFS/Hectochelle: dSph Status Report

Total = 4300 different stars observed so far; 700 repeats. For comparison: 450 total in Mateo 1998 summary.

Will hear more from WHT, VLT, Keck at this meeting . . .

User concerns

-- Learning curve for MMFS operations is steep. May require a `fiber operator’ who is employed only for MMFS runs and paid for by users as part of the cost of plates and plate fabrication. Need to coord- inate with LCO/Magellan staff.

-- Plate fabrication requires good coordinates from users; all software for plate fabrication are operating and well-tested.

-- Fiber assignment is still primitive; hope to improve this in anticipation of 2005B observations.