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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 $&u;m. 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
both with a single exposure.
| SWIMS | Component Assembly |
 |  |
The field of view (FoV) of the telescope is covered with two HAWAII-2RG focal plane arrays . Gaps between arrays are ∼ 2.3 mm or ∼ 130 pixels.
| Imag. FoV | 6.6' × 3.3' |
| Spec. FoV | 2.8' × 3.3' |
| # of arrays per arm | 2 (4096 × 2048 pixels) |
| Pixel scale (arcsec/pix) | 0.095 |
| Array configuration |   |
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 make the spectrum slightly broaden.
| Blue (0.9-1.4 μm) | Red (1.4-2.5 μm) | |
| Broad-band | Y (λc=1.03, Δλ=0.09), J (1.25, 0.16) | H (1.64, 0.30), Ks (2.14, 0.32) |
| Medium-band | J1 (1.17, 0.13), J2 (1.29, 0.12) | H1 (1.50, 0.12), H2 (1.61, 0.11), H3 (1.73, 0.12), K1 (2.02, 0.14), K2 (2.17, 0.14), K3 (2.31, 0.13) |
| Narrow-band | NB1244# (1.244, 0.012), NB1261# (1.261, 0.012), Paβ (1.292, 0.040), Paβ-off (1.326, 0.034) | NB1630# (1.630, 0.016), NB1653# (1.653, 0.016), Paα (1.875, 0.020), Paα-off (1.945, 0.040), NB2137# (2.137, 0.021), NB2167# (2.167, 0.021) |
| Grism | zJ (2.40 Å/pix, R ∼ 700-1200 w/ 0.5" slit) | HKs (4.57 Å/pix, R ∼ 600-1000 w/ 0.5" slit) |
Filters followed by "#" are those for SWIMS-18 survey.
Requests for use for any other purpose will be also welcomed.
| Transmission curves |
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ASCII data for each filter transmittance will be available soon. Please contact us for urgent use.
We utilize an ASIC, called SIDECAR, and its interface board, JADE-2, which control all of readout functions, to efficiently operate HAWAII-2RG arrays.
Under cryogenic condition (∼ 77K), the detector performance has been assessed, as listed below.
| blue left (b2) | blue right (b1) | red left (r1) | red right (r2) | |
| Array ID and grade | #17285 ENG | #16321 SCI | #196 SCI | #206 SCI |
| Dark Current (e-/sec/pix) | < 0.05 | --- | < 0.03 | < 0.06 |
| Readout Noise (CDS and 32 Fowler) | ∼ 22 e-, ∼ 7 e- | ∼ 18 e-, ∼ 4 e- | ∼ 20 e-, ∼ 4 e- | ∼ 20 e-, ∼ 5 e- |
| Frame Readout Time | 1.48 sec (32-ch readout w/ 100 kHz pixel rate) | |||
| Minimum Exposure Time including Overheads | ∼ 8 sec | |||
| FITS creation Time | t_frame (1.48 sec) + t_exp + t_overhead (∼ 6.5 sec + t_frame*n_read) | |||
| - t_frame: time to read 2K × 2K pixels - t_exp: exposure time for each pixel (from the 1st to the 2nd readout) - t_overhead: parameter setting, CDS calculation, # of Fowler. - n_read: # of Fowler sampling. | ||||
Note that Up-the-Ramp sampling mode is not available due to hardware limitation.
The cryogenic performance evaluation of Array #16321 will be completed in the next engineering run scheduled in Oct 2020. We expect to achieve the similar performance as #196 and #206.
The cryogenic storage called the carousel have 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 four slit mask frames for science use, which would constrain the number of frames in a observing night. To use more than 5 frames, it requires thermal cycle of the carousel which takes about 2 days for warming and 3 days for cooling.
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 additional 5 seconds/slot to rotate the carousel).
Note that IFU function is not available in S21A.
Mask design and spectral coverage: The array gap (&sim 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 spatial direction.
Total throughput including the telescope and the atmosphere is evaluated to be ∼ 0.4 for imaging and ∼ 0.3 for spectroscopy.
The following sensitivities (AB mag) are calculated with assumptions of seeing size=0.5 arcsec (photometry aperture radius=0.5 arcsec for point source or spatial extent=5.0 arcsec for extended source), exposure time=1 hr, and S/N=5.
| Point source (mag) | Y=24.9, J=24.8, H=24.6, Ks=24.5 |
| Extended source (mag/arcsec2) | TBW |
| Point source (mag) | J=21.1, H=20.7, Ks=20.9 |
| Extended source (mag/arcsec2) | TBW |
We offer a reduction pipeline for imaging data. The pipeline is written in Python, which has been confirmed to work with Python 2.7 and 3.7, and 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).
If you have any questions, contact us at kmotohara_at_ioa.s.u-tokyo.ac.jp.
