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Notice for the S22B CfP at the Subaru Telescope†

SWIMS will be open with shared risk in S22B at the Subaru Telescope as a PI-type instrument.

All applicants are required to contact the SWIMS team in advance and to include (at least) the SWIMS PI (Kentaro Motohara) as a Co-investigator.

Acceptable observing modes are normal, intensive , ToO, and service (only imaging) programs.

Notice for Service Program†

• ./Service Program Summary

Brief Introduction to SWIMS†

Simultaneous-color Wide-field Infrared Multi-object Spectrograph, or SWIMS, is an imager and multi-object spectrograph in the NIR wavelength of 0.9--2.5 μm. The major feature is simultaneous two-color observing capability using two optical arms (blue=0.9--1.40 μm and red=1.45--2.5 μm). It provides us with

• two-color simultaneous imaging with 6.7 × 3.3 arcmin^2 and 0.095 arcsec/pix sampling
• R ∼ 1000 multi-object slit spectroscopy (MOS) covering 0.9--2.5 μm for ∼ 40 objects/mask at maximum.

both with a single exposure.

Field of Views†

The field of view (FoV) of the telescope is covered with two HAWAII-2RG focal plane arrays . Gaps between arrays are ∼ 130 pixels.

Light-shaded regions show the FoV for the imaging mode while dark-shaded regions for the spectroscopy mode (for full range of spectra).

Black dots represent positions of source in the imaging mode which are also equivalent to the spectral positions of undeviated wavelength (λ ∼ 1.027 μm for blue, ∼ 1.734 μm for red).

Each stripe indicates the full range of the spectrum obtained (from shorter on the left to longer wavelength on the right). Note that any optical aberrations are not considered which would slightly broaden spectra.

Available filters/grisms†

Filters followed by "#" are those for SWIMS-18 survey. Requests for use for any other purpose will be also welcome.

ASCII data for each filter transmittance : swims-filter-data.zip

Detector Performance†

HAWAII-2RG arrays are controlled by individual readout electronics consisting of a SIDECAR ASIC and its interface board JADE-2.

Under cryogenic condition (blue ∼ 90K, red ∼ 80K), the detector performance has been assessed, as listed below.

Note that Up-the-Ramp sampling mode is not available due to hardware limitations.

Dome flat images as of May 2021:

Multi-object Spectroscopy Unit†

Instrument information†

The cryogenic storage called the carousel has 23 slots. Of them, several kinds of engineering-use masks and long-slit masks (one slot each), and one Integral Field Spectroscopy Unit (IFU) module (occupying two slots) are exclusively assigned. Other (∼ 15) slots can be used for users' MOS masks. At the moment, there are only 8 slit mask frames for science use, which would constrain the number of frames available in an observing night. To use more than 9 frames requires a thermal cycle of the carousel which takes about 2 days for warming and 3 days for cooling.

Time required for operation†

The time for target acquisition is about 15 minutes. The time required to exchange from one mask to another is about 2.5 minutes (and an additional 5 seconds/slot to rotate the carousel).

Missing spectral range†

Mask design and spectral coverage: The array gap (∼ 130 pix) produces a lack of spectral data (∼ 312 Å for blue and 594 Å for red). Pay attention to that in designing your slit mask(s). The only way to obtain the full spectral information between 0.9--2.5 μm is to prepare another slit mask in which the slit pattern is the same but all the slits are moved (more than 130 pix) along the spatial direction.

The wavelength range where the spectra falls into the gap when using the default long-slit mask is roughly 1.125--1.158 μm (blue) and 1.898--1.955 μm (red).

Integral Field spectroscopy Unit†

The Integral Field spectroscopy unit for SWIMS is a "handy-size" IFU module using image-slicer optics to be installed into the MOS exchanger unit as one of the MOS masks. A notable feature is that a slice width of 0.4 arcsec is optimized for typical seeing size so that it provides the largest field of views among near-infrared IFUs for 8--10m telescopes, together with the wide wavelength coverage.

Note that the availability of the IFU mode will be decided by the Observatory in early April based on the result of the engineering observations.

Sensitivity†

Total throughput including the telescope and the atmosphere is evaluated to be ∼ 0.4 for imaging and ∼ 0.3 for spectroscopy.

Note that the sensitivities described below may change according to the background conditions of OH airglow and thermal emission.

• Imaging (S/N=5, 1hr integration, 0.5 arcsec seeing, 1.0 arcsec aperture)

  Point source [ABmag]	Y=25.2, J=24.9, H=24.2, Ks=24.4	J1-2~25.0, H1-3~23.7, K1-K3~24.0
  Extended source [ABmag/arcsec^2]	TBW	TBW

  • The limiting magnitudes may be worsen by max ~0.5mag according to the atmospheric background fluctuations.
  • Expected limiting magnitudes of narrow-band filters are available in Workshop Presentation, page 16. Note that these values are highly uncertain.

• Spectroscopy (S/N=5, 1hr integration, 0.6 arcsec seeing, slit width=0.4" assumed, no binning applied along wavelength direction)

  Point source [ABmag]	Y=20.1, J=20.5, H=20.5, Ks=20.4
  Extended source [ABmag/arcsec^2]	TBW

Data Reduction Pipeline†

A reduction pipeline for imaging data is available at here. The pipeline is written in Python, which follows standard procedures from flat-fielding to final stacking.

We have no dedicated tools for spectroscopic data at the moment. Other pipelines such as MCSMDP for MOIRCS may work with SWIMS data, or certainly, IRAF is also useful (although it has not been maintained anymore).

Instrument Papers†

Overview†

• Konishi, M., et al., The University of Tokyo Atacama Observatory 6.5m telescope: On-sky performance of the near-infrared instrument SWIMS on the Subaru telescope, Proceedings of the SPIE 11447, 114475H (2020)
• Konishi, M., et al., Development status of the simultaneous two-color near-infrared multi-object spectrograph SWIMS for the TAO 6.5m telescope, Proceedings of the SPIE 10702, 1070226 (2018)
• Motohara, K., et al., NIR camera and spectrograph SWIMS for TAO 6.5m telescope: overview and development status, Proceedings of the SPIE 9908, 99083U (2016)
• Motohara, K., et al., Development of a simultaneous two-color near-infrared multi-object spectrograph SWIMS for the TAO 6.5-m telescope, Proceedings of the SPIE 9147, 91476K (2014)

Detector Control†

• Terao, Y., et al., NIR camera and spectrograph SWIMS for TAO 6.5m telescope: array control system and its performance, Proceedings of the SPIE 9915, 99151W (2016)
• Todo, S., et al., Optimization and performance of H2RG detectors and SIDECAR ASICs for SWIMS, Proceedings of the SPIE 9154, 91541L (2014)

Multi-Object Spectroscopy Unit (MOSU)†

• Takahashi, H., et al., Development of multi-object spectroscopy unit for simultaneous-color wide-field infrared multi-object spectrograph, Proceedings of the SPIE 9147, 91476N (2014)

Contact†

If you have any questions, contact us at kmotohara_at_ioa.s.u-tokyo.ac.jp.