AAOmega - SPIRAL IFU
AAT Instrument.| In Brief: | The SPIRAL Integral Field Unit (IFU) is a 512 element fibre feed for the AAOmega spectrograph. SPIRAL provides a 2D spectroscopy over a Field of View of 22.4x11.2 arcsec at a spatial resolution of 0.7arcsec. |
|---|---|
| Instrument Scientist: | Rob Sharp <rgs@aao.gov.au> |
| Manual: | On-line
manuals and information SPIRAL acquisition and overheads There is currently no independent manual for the SPIRAL system. SPIRAL uses the AAOmega spectrograph and so much of the information relevant to AAOmega MOS mode is also relevant for SPIRAL. There is a separate IFU ETC. The user should note when selecting gratings that the smaller IFU fibres will give x1.5 increased spectral resolution (but with a less well resolved PSF) than MOS. SPIRAL is designed with Nod and Shuffle observations in minded but for many programs this will not be the optimal mode of operation due to overheads and increased (but systematic free subtraction) background noise for this mode. The original SPIRAL instrument was first commissioned for use with the RGO spectrograph and had a limited operational wavelength range. Due to material availabilities at the time of construction, and matching to the capabilities of the RGO spectrograph, the glasses and fibres used in the SPIRAL IFU feed which is currently used with AAOmega have a poor UV performance (below ~4000A) and have a significant absorption band (due to water in the fibres used to construct SPIRAL) in the I band. A full characterization of these effects when used with the broad wavelength coverage of AAOmega, is under way. U band observations are effectively impossible with SPIRAL. Concerned users should contact the support Rob Sharp (rgs@aao.gov.au) for more details. |
| Other Info: |
AAOmega home
page and Detailed
information on AAOmega
|
Service observations: |
A service program is available for projects requiring < 6 hrs. |
Detector: |
2xE2V 2024x4096 CCDs (note that dispersion is along the 2k axis) |
Focal Station: |
Cass focus. Note: since SPIRAL is mounted at Cass and uses the f/8 secondary, dual instrument runs using SPIRAL and 2dF observations cannot not made. An afternoon change over is required. It is, in principle, possible to rapidly switch between SPIRAL and IRIS2 if the observational program justified the overhead. |
Spectral Resolution*: |
R= 1,500 to 10,000 Please read the notes on gratings at : http://local.aao.gov.au/AAO/2df/aaomega/aaomega_gratings.html Also, due to the materials used in the construction of SPIRAL, the user should note that the system has very low U band response in comparison with the AAOmega MOS system. |
Fibre diameter: |
0.7 arcsec |
Gratings: |
See the AAOmega
gratings page and the AAOmega
Grating calculator for more information on the VPH gratings
available Please read the notes on gratings at : http://local.aao.gov.au/AAO/2df/aaomega/aaomega_gratings.html |
Sensitivities: |
AAOmega
S/N Calculator (IFU) Note: The IFU S/N calculator assumes that the object presents a uniform surface brightness which will result in the given magnitude when integrated over an aperture of the radius selected by the user. The effect of this is that S/N will be lower, as presented by the calculator, for a constant magnitude and increasing aperture size. This is in contrast to the result that would be obtained if the input magnitude was a constant surface brightness per square arcsecond, which is a mode of operation often assumed by some users. |
Rob Sharp (rgs@aao.gov.au)