The Study of IFU for the Li Jiang 2.4m Telescope ZHANG Jujia 张居甲 Yun Nan Astronomical Observatory. CAS Sino-French IFU Workshop Nov Li Jiang

Outline 1. An Experiment of IFU for the 2.4m Telescope 2. The Application of IFU for the 2.4m Telescope 3. Conceptual Design of IFU for the 2.4m Telescope 4. Summary

1. An Experiment of IFU for the 2.4m Telescope IFS encodes all the spectral and spatial information in the same exposure resulting in a two dimensional field of view for a given detector format. Why Integral Field Spectrograph? As we enter the age when 8 m class telescopes are producing science on a routine basis, single-object spectroscopy on small telescopes (apertures <4 m) is no longer competitive. There is a need to exploit the immense multiplex advantage that can be provided by the wide-field foci on small telescopes. --Gary J. Hill et al. SPIE 2002 For the good seeing of GMG station and outstanding performance of Li Jing 2.4m telescope, that is a wonderful place to mount an IFU for the studying of local universe.

Collimator Grating Optics layout Mechanical configuration Hexagonal IFU Top Pseudo-Slit

Parameter Fiber ： 143  m, F/6, 4m Sampling ： 1".5 Field of View ： 8" x 10" (Hexagonal Field by 19 Fibers ) Dispersion ：  =1.83Å （ =5500Å, R≈3000 ） Wavelength arrange ： 4000Å~7800Å Solar absorption Spectrum

The integral emission spectrum of M42 Attached to the Cassegrain focus 2.4m Telescope Orion Nebula

Problems Low accuracy of fiber arrangement It’s Hand Made without any machining equipment Plan to contribute a system to do it Epoxy Use common glue Spectrograph Ageing

2. The Application of IFU for the 2.4m Telescope Nearby Galaxies: Velocity distribution Missive Black Holes Abundance and age Global Clusters in the Milk Way: Star population evolution HII regions in the Milk Way: Electron temperature and number density Crowed field: Better background subtraction Extra Galaxies’ Planetary Nebulas or Global Clusters Supernova, AGN From SAURON Project

Flexible parameters of IFU Space Resolution (sampling): 0.5" : The average seeing at GMG is 1" (Sampling Theory) 1": For the bad seeing (Use Focal Reducer) ~3": For wider Field (LAMSOT or VIRUS-P at 2.4m telescope) Field of View: 30"~2' Science Cases and requirements for the IFU The velocity distribution and material abundance of galaxies Material abundance (Visible) ◆ Hydrogen: R~2000 ◆ Metalicity: R>6000 ◆ H  /Fe: R>15000 Velocity (dependent on the magnitude and resolution) 10~100km/s Wavelength range (for the low spectral resolution): 4000~9000 Å

If the IFU under fiber principle: With or without Lenslet array (fill factor: 95%or 65%) 3. The Conceptual Design of IFU for the 2.4m Telescope 3.1 Principle of IFU Lens Array? Fiber Array? Image Slicer? For the better sky subtraction: Sky IFU or Nod and Shuffle Observation (Full field or faint object) What kind of object would be observed

Science cases: specially for nearby galaxies (Also Global Clusters and HII regions in the Milk Way) Principle: Lens array and fibers Sampling: 0.5"/1" or/and 1.5"/3" (F/8 to F/4 Focal Reducer) FOV: 15"/30"(mosaic) or 45"/1.5' Spectral resolution: 1K 、 2K 、 5K (even 10K) Wavelength: 4000~9000 Å (Use High OH fiber made by Polymicro) Micro-Lens: ~150  m(with or without fore optics) Fiber aperture: ~80  m Fiber length and amount: ~20m 900 fibers Fiber focal ration: F/4 Grating: VPH Transmission Grating CCD: 4Kx4K 3.2 One flexible design

Optics Layout （ Sketch ） Lens range CCD Camera VPH Collimator Fiber slit and lens Why ALL Fraction? Low spectrum resolution (chromatism correction will be not too hard) Make optic units smaller Micro lens Front Optics Lens array Fiber Focal Reducer Sampling: 0.5"/1" or/and 1.5"/3"

3.3 Cooperate with MOS (LiMOS?) If we have MOS and IFU why not Multi-IFUs Same alike FLAMES-GIRAFFE at VLT-UT2 (Our French friends are familiar with it) With MOS, Multi-IFUs and a wide fied IFU The Multi-IFUs at 2.4m telescope can be used to study crowed field in the local universe The small IFU under the same sampling with MOS and contains 4x4 fibers then can use the same fiber pedestal Object IFU MOS’ Fiber Sampling: ~1.5" 625 fibers for IFU 25 fibers for Sky 150 fibers for MOS

4. Summary IFU will be a powerful and wonderful equipment for 2.4m telescope to study local universe. (Wide field, low spatial resolution or Seeing limited, low-middle spectral resolution and visible) IFU on the fiber principle will be preferred for 2.4m telescope. To determine the parameters of IFU is an art of balance. If we manufacture a IFU under fibers way: Add MOS will not increases cost sharply And then add multi-IFUs also wont increases cost obviously