MOIRCS Filters
Available Filters
The following table lists the broad-band filters currently installed in MOIRCS, together with their estimated sensitivities. The transmission curves of each filter are from the data sheets supplied by the company. Estimated sensitivities listed are for a 5 sigma detection in 1 hour of integration, assuming good (0.5'') seeing and a moderately dark sky (Please see the Exposures page) . Point sources are measured in a 1.0'' diameter aperture. Extended source sensitivities are per pixel.Broad-Band Filters
| Filter | Wavelength [um] | Sensitivity (Vega magnitude) | mag for 1 e-/s |
||||
|---|---|---|---|---|---|---|---|
| Name | Plot | List | Centre | Width | [mag] | [mag/pixel] | |
| Y(2) |  |
 |
1.02 | 0.10 | --- | --- | --- |
| J |  |
|
1.26 | 0.17 | 23.6 | 25.9 | 26.0 |
| H |  |
|
1.64 | 0.28 | 22.5 | 24.8 | 26.2 |
| Ks(1) | |
|
2.14 | 0.31 | 22.6 | 24.8 | 25.5 |
| K (3) |  |
|
2.20 | 0.40 | --- | --- | --- |
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(!! IMPORTANT !!): We replaced the Ks filter to the new "fringe-free" type in July 2008. The filter was actually the same one used as "Ks_wedge" during S08A as a test. The transimission curve is approximately similar to the old one, but slightly higher throughput. We will measure the sensitivity soon (values on the table is still for the old Ks filter). Transmission curve of the old Ks filter can be found here (jpg, text).
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The Y broadband filter is newly installed in July 2007. However the detail of the performance is still not well determined yet. The turret position of Y-band filter was changed in July 2008, so the flatfielding pattern will change.
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Though the main purpose of the standard (Johnson) K filter is the order sorting of R1300 grism, it is also available for imaging. The filter, however, cannot take the dome-flat data, because the thermal emission from dome itself is too bright.
Notes:
The Imaging Exposure Time Calculator is available. Please note that the Imaging ETC underestimates the entire overhead time, as it does not consider the time for generating fits, dithering, coadding, dummyread option, etc. You can instead calculate the accurate overhead time using the overhead calculator (Excel format). It is available in the "Guide to Imaging Exposure Times" page.
Narrow-Band Filters
Three narrow-band filters (H2v=1-0, [FeII], NB119, and K-continuum) are available for imaging observation. The central wavelength(CW) and the bandwidth (BW: defined by FWHM) of H2, [FeII], and NB119 filters are each 2.116/0.021 um, 1.6444/0.026 um, and 1.1885/0.0141 um, respectively. For K-continuum filter the CW and the BW are slightly different among channel 1 and 2. For channel 1 the CW and the BW are 2.238 and 0.064 respectively, and for channel 2 they are each 2.257 and 0.061, respectively. The peak transmittance of these NB filters are all roughly 80 to 90%.
The actual value of the CW for these filters will slightly shift across the field of view, because the transmission curve moves as a function of the angle of incidence. The CWs described above are all the value at the center of the optics; i.e. around the center of each channel. If you need more information about the detail, please contact to the Support Astronomer.
Note that the background level of NB119 filter is very dark. Minimum exposure of ~30 minutes is sometimes required to reach the background-limited case. Sky subtraction is generally difficult due to the change of the background.
User Filters
We are accepting the user filters since S07A. The detail and the user filter policy can be found in information page. Currently the number of vacant turret slot is very limited.Please note that all data on these pages are subject to change as the evaluation of the performance of MOIRCS progresses.
Created by Yuka Katsuno Uchimoto (Feb 2006)
Revised by Ichi Tanaka (2008-07-30)