MOIRCS Information for Spectroscopy Mode

OPE File Information

Please read the following documents before your observation.

• Sample OPE file for spectroscopy observation can be downloaded here. (Last update 2024-11-08)

  • The appearance may be strange with no line break under the Windows browser -- you may change .ope to .txt if it happens.
  • Edit the following lines suggested as ">>> To Users:" in the ope file and send back to the primary SA beforehand. You don't have to care too much about the detail of the numbers (exposure time, dither length, etc). They will be adjusted on site.

• Observing Time Table Template is also available here.

  • Sharing the plan is very important for better understanding of your plan among the observing staff. Fill it and send back to the Support Staff before your observing run starts.

●Description of the OPE file: Guide to MOS Observation with MOIRCS [Under Construction]

●The list of the current filter and grism configuration alias can be found here (Last update: 2024-03-05)

●Recent dome flat setting log can be found here (internal only).

Flat Fielding/Comparison

We used to use a bare aluminum back surface of the top screen for the dome flat surface until July 2020. Then we updated the dome flat surface to a better quality panels (Parmaflect-94). All the dome flat data after August 2020 has been under the new (and better) dome flat panel.

Dome flat data will be taken before and after the observation. As a default we take 7 dome flat data for each mask. We will also take the lamp-off dome flat data for the spectroscopy observation in the K-band window (HK500 & VPH-K). We usually do not take the lamp-off dome data for the other wavelengths, because it is not essential. Instead, the Dark data under the same exposure will be provided to uses for the hot pixel subtraction purpose. If you need the lamp-off data for YJH spectroscopy, please explicitly request it before the observation.

The Halogen Lamp on the calibration probe may also work as a flat field data, though it can illuminate only a part of the field of view. So, the use of the Halogen Lamp for flat can only be considered for the single-object case. An advantage of Halogen lamp is that there is no absorption between the atmospheric windows (between Y/J/H/K). Ask the SA for more information well before your observations.

The ThAr comparison lamp is available for the wavelength calibration. We take the comparison data by scanning the entire MOS field of view (namely take exposures at the 4-5 position: see the illumination region map). As there are many OH night sky lines available for the NIR window, we recommend to use the OH lines for calibration for medium-resolution spectroscopy. But there are some wavelength region where the OH line is relatively poor (e.g. red side of K window). The night lines may also be blended in the low-dispersion grism (zJ500, HK500) data, especially in YJ window. Therefore, we take the ThAr data for the R500 observation. Be aware that the slit mask position between the science data and the calibration data may be slightly different, which may introduce the systematic error during wavelength calibration. You can check the possible shift by comparing the mask image during the obs and calibration. For more detail, see the Wavelength calibration page.

Autoguider Issue

As the MOIRCS FOV occupies a large fraction of the Cassegrain field of view, the area we can choose an Auto Guider (AG) star without vignetting is fairly limited. A star with visual magnitude of 9 to 16 in the R-band (650 nm) is necessary as the AG star. Such bright stars are relatively sparse in high Galactic latitude, and sometimes it is difficult to find such a star in the non-vignetting area. If the AG vignetting in the imaging data occurs, it would complicate the data reduction. Also in MOS mode, you may lose the data from some slitlets by vignetting. To avoid such troubles, all MOS (or NB119 imaging too) observers should check the availability of an AG star in the "safe" area before the observation to avoid the possible loss of important targets.

The diameter of the shadow by the Autoguider has 72 arcseconds. You can choose any bright star within a 4.6'-radius area from the FOV center in the Cassegrain focal area (See figure below). But if you want to avoid vignetting by the shadow of the AG probe, the area you can choose is limited to at least 72" away from the edge of the MOIRCS f.o.v. or any of your slitlets. The blue-colored area in the bottom figure indicates the "safe" region, where the shadow of the AG probe will never cause vignetting on the area you may put slitlets. For imaging, only the left and the right side of the blue areas can be used for the AG.

The ds9 region file for the AG availability check is available here. It is prepared for the DSS image only.

Another issue is the effect of the Moon, cloud, or twilight onto the AG. As is written in the Imaging Information page, the AG may not work properly if the Moon is close to your target less than 20 degrees. It is the PI's responsibility to check the separation between the moon and your targets when submitting the proposals. Please explicitly state the observing dates you want to avoid the assignment on the "Scheduling Requirement" section of the proposal.

The autoguider may quickly lose the star if cirrus/clouds come into the field of view during the bright nights. Once we completely lose the AG star, the MOS alignment will be lost, forcing us to do the MOS alignment from the beginning (thus time consuming). It is not recommended to do MOS observation under cirrus condition.

Troubled Data Information

The list below is not complete. The use of any archived data should be with enough caution. The date is in HST.

• Some data before Feb 2019
  • Sometimes a small vignetting region is seen on the rightmost edge of the channel-2 imaging data taken before Feb 2019. It gradually gets larger over time in 2018, and the data around the Dec 2018 - Jan 2019 show quite large (~80 pixels) vignetting across all right edge (see example). It was caused by the "mos rail" and we fixed it in Feb 2019. Note that the MCSRED2 tasks can handle the ch2 rail vignetting properly ("ch2rail" parameter).
• Feb 2017 to March 2018
  • The time-related FITS header keywords (HST, UT, MJD) are still in problem. HST-END, UT-END, MJD-END, HST, UT, MJD are totally wrong. "HST" is approximately "HST-STR" + ((N-1)NDR)/2 + 5. HST-END is approximately HST-STR" + (N-1)NDR + 5. It may still have the uncertainty of +-30 sec. We are sorry about this.
• 11 August, 2017
  • There are no channel-2 data due to the hardware trouble (MCSA00241250 -- MCSA00241452, except 241254 and 241256).
• July 2016 to Feb 2017
  • The time-related FITS header keywords (HST, UT, probably MJD too) are still inaccurate. Sometimes values are inconsistent with each other. Error ranges from a few minutes to sometimes a few 10s minutes, depending on the exposure parameter.
• June-July, 2016
  • The time-related FITS header keywords (HST, UT, probably MJD too) are inaccurate by 20-40 seconds.

Before the MOIRCS Upgrade

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• Sep 15 -- 16 2014
  Detector Power supply setting is gone and we could not use the channel-2 side whole night.
• June 10-11, 2014
  Detector power supply had a trouble. Sometimes data for channel-2 showed blank (0 counts).
• Apr 11 -- 15 2014
  We had a bit drop failure on the readout system. As a result, much of channel-1 data (3rd & 4th quadrants) during the period was with unusually-large noise.
• Apr 22 -- June 2013
  The ch2 data of April 22 (morning) and after that (till the end of S13A) are likely to have suffered from the T5 problem.
• March -- May 2013
  Though T5 trouble continues, we have found a workaround. However, a care must be paid for the scientific use for the data taken during other dates (especially the data taken on Apr 6).
• Jan 22 -- 24, 2013
  T5 trouble still persists. All the spectroscopic data during the nights should be okay, though the exact position of filters/grisms may not be exactly the same as before. Note that the fits header informations (FILTER01 to 03) are mostly wrong, due to the trouble of the initialization software.
• Jan 4 -- 5, 2013
  More trouble on turret function. Now channel-2 cold stop turret (T5) is not working good. As a result, channel-2 data showed significant vignetting. All the data taken in that day are not usable. Filter informations on the fits header are mostly useless.
• Sep 29, 2012 to Jan 24, 2013
  Channel-1 Grism Turret (T3) has stacked again, after the fix in May 2011. The channel-1 data during Sep 29 to Oct 2 were just junk. On midnight of Oct 2, while we are trying troubleshoot, T3 has just stacked almost at the correct position of HK500 grism port. The channel-1 data after Oct 2 is useful for HK500 spectroscopy only. Note that, however, the filter information on the fits header of channel-1 data is wrong ("FILTER03" keyword for odd file number).
• All the spectroscopic data during Sep 2011 -- Aug 2012
  The data were taken without Autoguider, as it is unavailable due to the [telescope incident](http://www.nao.ac.jp/releaselist/archive/201109-report-subaru-tel/). Some data may have significant slit loss by poor guiding.
• January to May 2011
  The channel-1 spec data often showed the tilt (~3-7 degrees counterclockwise) due to the trouble of the grism turret (T3). The cause was related to the T3 stack event during S10B. Fixed in middle May 2011.
• September to December 2010
  The channel-1 data was not available due to the stack event of the grism turret (T3).
• 30 Oct to 2 Nov, 2007
  The channel-1 data may have suffered from the affection of trouble in the sensor of the filter turret (T1). Do not use the data during the period.
• October 2007 to June 2008
  We operated with the engineering-grade detector for channel-1 during the period. The data should be handled with enough caution. A large uncertainty in flux is expected. Some more informations can be found from [here](./OLD/chip1info.html).
  It was replaced to the new Science-grade detector in July 2007. It is not the same one as we operated before Aug 2007.
• Aug to Sep 2007
  The channel-1 during the period were not available due to the trouble on the detector.
• Before September 2006
  All the old spectroscopic data before the open use (before Sep 2006) were affected by a significant amount of stray lights. Now the effect if it is relatively minor. All the information about the fixing work in 2006 can be found [here](OLD/stray_info.html).

Important Notice for the MOS Service Program

Important Notice for the MOS Service Program

A conditional access to the Multi-Object Spectroscopy (MOS) Mode for Service Program has been available since S24A. The same as before, the applicants of the MOS mode have to have the MOS masks that were previously-cut (namely, this program is a promotion for the publication of old data by offering the supplement). Maximum number of the masks for service mode are 2. The use of the common-use longslit masks are not allowed.

Who Can Apply?

If your old data can be published by adding small amount (<4hr) of supplementary data, you can consider applying this program. We consider the situation below.

• Loss of critical data by weather loss or technical trouble.
• Failure taking good calibration star.
• The S/N could not reach to the level for publication by unforeseen causes (*).

• MOS masks were cut but never used due to bad weather or technical trouble.

  (*) Please clearly describe the objective evidence in the SJ or TJ part. If not, the observatory may not allow the submission.

Those who wants to apply this promotion program must carefully read below.

In order to avoid any conflict with the Dual-Anonymous Review System introduced for Subaru's proposal reviewing, you must avoid mentioning any information of previously-awarded program (PI name, proposal ID, etc) related to the MOS you want to re-use. You have to make sure that any information related to the previous observation is through "Private Communication". Please make sure to keep it.

Applicants must follow the steps below.

1. Contact the primary SA first!! Please send the detail of the situation to the SA so that they can verify the claim. They will check 1) the availability of the MOS Masks, 2) validity of justification for Service within the observatory. It must be at least 1 week before the deadline.
2. The SA will give you an Approval ID to you.
3. Clearly state the ID on the Technical Justification part.
4. Submit your proposal.

MOS Spectroscopic Data Reduction Software

● "MCSMDP", a MOS data reduction package by Dr. Tomohiro Yoshikawa (Edecs, a member of MOIRCS Builder), is publicly available.

NEWS! We have updated the code to be compatible with the MOIRCS data after upgrade (2016-)*. You can download the source package from here (version 2025-1-28).

• The manual is included in the zip file. Carefully read them before install (see also the "additional_install_note.txt" inside: 2025-1-28).
• We should note that it was developed based on the Ubuntu ver 20.04LTS. Unfortunately, the installer does not work for the most recent version (22.04 or newer: due to the Python 3 environment they set as a default). And also, it might cause some issue if you already installed relatively newer version of anaconda3 (version 4.14.0 or younger: we have a known issue). Our recommendation is to build a dedicated analysis environment using Ubuntu 20.04.6 LTS without any pre-installed software (e.g., the use of the VirtualBox software).

* You can download the MCSDP software for the OLD MOIRCS data before 2015.
Edechs MCSMDP Website (En / JP)
The SA greatly appreciates the author for his contribution to MOIRCS users.

● Spectroscopy Data Reduction Manual

Subaru Data Reduction School used the MOIRCS data for teaching material. You can find the school text below.

Subaru NIR Spectroscopy Data Reduction Manual [ Eng(2014-02-28) / JP(2011) ]

• The document was prepared for the OLD MOIRCS before the detector and system upgrade.
  Though the essence of the document can also be applicable to new data after the upgrade, bad pixel masks, distortion correction data, etc, has changed since then.

If you are developing your own software and want to put the link to your software website here, please contact to the SA. We greatly appreciate your contribution.

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Please note that all data on these pages are subject to change. Any questions/comments should be directed to the SA (Ichi Tanaka: ichi [at] subaru.naoj.org ; change " [at] " to @).

Updated on January 22, 2025