Version 1 (modified by trac, 6 months ago) ( diff )


Attendance: Nick(UW), Bill(NMSU), Suzanne(UW), Charly(UW), John H(NMSU), Bruce(JHU), Don(UC), Steve(UVA), and Jen S(UVA).

Review current routing and potential focal plane configuration

Community Interest

Suzanne - So far interest from the users comity has been slow. Colorado is interested and has some science cases. We would like to see the fiber feed used 5 to 10% of the time to justify the cost of instillation. users interest in order to consider an ARC funded project.

On this call there did seem to be a good amount of interest in a fiber feed system for a number of APOGEE follow up projects. John commented that the use of the 1 m fiber feed to APOGEE has been far higher than expected. Both John and Jen seemed to think they would use the instrument, Steve well supportive of hte project in general dose not think he would have any time to use this fiber feed.

Comments and suggestions

Steve - I've always envisioned a fiber feed that consisted of 1 IFU and a number of free rovers. One way we could do this is to allow the option down the line for A MOS mode.

Following this comment from Steve we had a long conversation about the potential alternate configurations. Nicks explanation for only presenting a single IFU is that this is the simplest mode we could come up with for a full 300 fiber run. The cost and complexity of a MOS system would certainly add a significant amount of money to the project budget. There seemed to be general agreement that a basic deployment of a single IFU was probably best but that we should leave room in the design to add a configurable focal plane in the future.

The was also a good conversation about the size and configuration of the IFU it self. Basic questions which should be answers based on the science case regarding the IFU are as follows.

  • What is the best geometry of the IFU? Would a oblong IFU offer a better match to the potential targets.
  • Should we consider a sparse packed IFU for increasing the foot print of the IFU on sky.
  • Is there any game we can play to increase the spaxal size above the 1.4 arcsec/fiber delivered by the 3.5m telescope converted to f/5?

Don York - Is primarily interested in using a fiber bundle on the reflection nebulae. This would be an optical spectrograph application so dose not fit well with the APOGEE fiber feed. A future spectrograph may be able to do this. The requested FOV is 1 arc-min

==Other options for a fiber feed==

A comment that was comment to many in this group was a request to see a scaled back project which could reduce total project cost yet still deliver a fiber feed between the APOGEE spectrograph and the 3.5m focal plane. Bruce specifically suggests a 'bare bones' project which would run one or a few fibers in existing trenches. This scaled back version could use the focal plane of the Echelle further reducing cost by using the existing Echelle guider. Another advantage is that using existing conduits would not require Forest Service approval.

Nick is going to look at the cost of a few different options and present this back to the group in a few weeks. This would include the following options.

  1. Bare Bones single fiber feed. This would consist of a single (or a few) fibers running in existing conduits and would use the echelle focal plane.
  1. Bare fiber IFU option. This would include removing all of the work associated with lenslet coupling the IFU. The fill ratio would suffer farly heavaly within the IFU but the project cost would be reduced.
  1. Fewer fiber option. A large project expense is the cost of materials for the long 200 m fiber run. WE will look at options to feed a lower number of fibers to try and reduce over all cost without sacrificing the usefulness of hte IFU. This could be combined with option two to produce a lower fiber count bare fiber IFU.

Identify key science cases.

  • Individual object follow up . Dose not require and IFU but would work with an IFU.
    • High cadence RV follow up.
  • Northern Globular clusters. Jen, John H
    • Integrated light spectroscopy of globular cluster in the IR - Jen
    • How far would we penetrate into the core?
    • How far out is interesting?
  • Dwarf Spheroidal - John H
  • Star forming regions - Bally
  • Dwarf Galaxies - John H
  • Integrated light on supernovae

Task List

Nick MacDonald - Develop 3 more project options which could reduce overall cost.

John H - Develop science case for single object observations and/or GC science case.

Jen S - Develop science case for GC work and Dwarf Spheroidals.

John B - Flesh out science case on nebular kinematics, Classification of CMZ massive stars, and Star formation.

Due date for all is 2 days before the next 3.5m users meeting 1/26/15.

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