After Observing

IGRINS Data from Gemini

Data distribution will occur a couple weeks after each IGRINS observing block.

In 2022, we will plan to distribute data every two weeks.

At Gemini, the slit size is 0.34ʺ x 5ʺ.

The plate scale on the imaging detector is ~0.041"/pix, and ~0.091"/pix in the spatial direction of the 2-D spectrum.

The IGRINS PLP, and the distributed reduced data, do not necessary correct tellluric contamination at the level needed for all science.

Data Format and Reduction

Cross-dispersed IGRINS H- and K-band spectra are saved as 2D FITS files. The figure below shows the AB sky-subtracted images of an emission line source observed with IGRINS.

Data Reduction

The IGRINS Pipeline Package (PLP) can be used to optimally extract 1D spectra, telluric correct, and to provide 2D rectified spectra for post-processing. The PLP is python-based, available publicly, and requires minimal interaction for reducing IGRINS data. The IGRINS Team does not provide reduced data to all users. We encourage you to collaborate with an IGRINS Team member if you wish to have your spectra reduced by us. Email igrins.contact [at] gmail.com if you need help locating an experienced IGRINS collaborator in your field of study.

PLP Outputs

spec_A0v.fits

The data for your target spectra that has had A0 (to flatten) and Vega (to flux) corrections applied, including the data used to create this. Each extension is a 2048 x 28 array, with the same header (except for the PRIMARY) other than EXTNAME, which is near the end.

[0] Primary: The corrected target spectrum = (TGT_SPEC/A0V_SPEC)*VEGA_SPEC

[1] Wavelength: The wavelength solution - in um in vacuum (so 1.42um for instance)

[2] TGT_SPEC: The extracted target spectrum (from the target spec.fits file)

[3] A0V_SPEC: The extracted A0V spectrum (from the A0V spec.fits file)

[4] VEGA_SPEC: A model of the Vega spectrum (from plp directory: master_calib/A0V/vegallpr25.50000resam5.npy) - for more info, http://kurucz.harvard.edu/stars.html.

sn.fits (target and A0)

Signal-to-Noise per pixel matching to the spec.fits output.

variance.fits (target and A0)

Variance per pixel matching spec.fits output.

spec.fits (target and A0)

The source spectrum. It says the spectral unit is ADUs.

spec_flattened.fits (A0)

The flattened A0 spectrum.

spec2d.fits (target and A0)

var2d.fits (target and A0)

wave.fits (target and A0) - The IGRINS wavelength solution is in vacuum, not air.

The wavelength solution for a given source, in nm (so 1429nm for instance). The A0 should have an improved wavelength solution.

Data Distribution Package

After your targets have been observed and the data is cataloged, you will be contacted with instructions to collect your data. IGRINS data is not currently handled by the Gemini Online Archive, but it will be in the future.

Some files are available to all IGRINS PIs. These include DARKS, FLATS, SKY, and A0V telluric standard (STD) star observations.

All telluric stars are included in the folders labeled 'GS-CAL'.

To reduce your own data you will need FLATS, SKY frames, and raw data files for both H and K bands. DARKS are not used by the PLP. Science frames with exposure times >120 seconds can be used in the place of SKY frames.

PIs will receive a folder that contains all raw FITS data corresponding to their Program ID. This includes slit-view, H-band and K-band files labeled 'SDCS', 'SDCH', 'SDCK'. They will also receive a recipe file to reduce their data in addition to the PLP products from that recipe file. This reduced data is for initial inspection - the PI should reduce their data on their own or contact igrins.contact [at] gmail.com for a Team collaborator that can check data quality and describe the reduction in more detail.

If the PI wishes to reduce the data differently than has been provided by the IGRINS Team, they will need to install the PLP (see above). Once the PLP is installed, the PI can copy the FLATS, SKY and science files into a single folder (e.g. /plp/indata/20180503/) and run the recipe file.

The 'cal_logs' directory provides digital text logs of calibration sources for each night that IGRINS was at Gemini. PIs can use these logs to identify other possible telluric correction stars for their science data.

Publications using IGRINS data

The standard acknowledgement for IGRINS must be in every publication using IGRINS data:

“This work used the Immersion Grating Infrared Spectrometer (IGRINS) that was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the Mt. Cuba Astronomical Foundation, of the US National Science Foundation under grants AST-1229522 and AST-1702267, of the McDonald Observatory of the University of Texas at Austin, of the Korean GMT Project of KASI, and Gemini Observatory."

The facility that the IGRINS data was obtained with should be acknowledged as required by Gemini.

http://www.gemini.edu/sciops/data-and-results/acknowledging-gemini

The resolving power of IGRINS is R~45,000.

Any paper using IGRINS science or engineering data must reference the designated IGRINS instrument citations(s):

Park, C. et al., “Design and early performance of IGRINS (Immersion Grating Infrared Spectrometer),” Proc. SPIE 9147 (2014).

Lee, Jae-Joon & Gullikson, Kevin. (2016). plp: v2.1 alpha 3 [Data set]. Zenodo. http://doi.org/10.5281/zenodo.56067

Mace, G. et al., “IGRINS at the Discovery Channel Telescope and Gemini South,” Proc. SPIE 10702 (2018).

Authors should inform the IGRINS team of the submission of all papers, refereed and non-refereed, at the time of acceptance, giving the title, journal, volume, and author list. This allows us to track instrument use for grant requirements.

Instrument Team Referee

The IGRINS team has an internal refereeing process for observing and instrumentation papers. Since we verify the representation and use of IGRINS in all published papers, it is in the best interest of the author to provide us with a copy at submission in order to ensure that the above guidelines have been followed. We strongly recommend that all papers to be submitted to a refereed journal, and using IGRINS data or technical information, go through the IGRINS internal refereeing process. Papers for non-refereed conference proceedings may also make use of this service. First authors should submit papers that are ready for publication directly to igrins.contact [at] gmail.com for comment. Revisions in response to these comments can be made at the discretion of the authors.