7.1. Example 4 - Datasets descriptions

7.1.1. Nod-and-Shuffle Correct for Extra Order

This is a GMOS longslit nod-and-shuffle observation. The target is a high redshift quasar. We will use this observation to show how to recognize when the light from the second order shows up and how to correct for it using the interactive tools.

The particularity with this data is that the setting is quite red and the second order shows up in the spectrum. The configuration uses the OG515 blocking filter and the second order light appears at 1030nm.

The data uses the R400 grating on GMOS North equipped with the EEV CCDs. The central wavelengths are 880 nm, 890 nm, and 900 nm. The sequence is:

[Flat, Science], [Science, Flat], [Flat - Science]

with the first group of four at 900nm, the second at 890nm, and the last at 880nm. The arcs were obtained in the morning. The spectrophotometry standard was obtained about 2 months after the science observation.

The calibrations we use for this example are:

  • BPM. The bad pixel masks are now found in the Gemini Science Archive instead of being packaged with the software. They are associated like the other calibrations. Here we need the 1x2 binning GMOS-N Hamamatsu BPM valid for data taken in 2017. (The date in the name is the “valid from” date.)

  • Biases. The science and the standard observations are often taken with different Region-of-Interest (ROI) as the standard uses only the central area. Therefore we need two sets of biases, one for the science’s “Full Frame” ROI, and one for the standard’s “Central Spectrum” ROI. Here we use only 5 biases for each setting to minimize the amount of data needed. For a science reduction, please consider using 10 to 20 biases.

  • Darks. For the EEV CCDs, nod-and-shuffle darks are required to map the the charge trapping that happens when the electrons are shuffle around.

  • Spectroscopic flats taken with each of the science and standard observations.

  • Arcs, for both the science and the standard observations.

  • A spectrophotometric standard.

Warning

The Bad Pixel Masks (BPMs) are now found in the archive rather than packaged with the software. You must get the static BPM from the archive. See Getting Bad Pixel Masks from the archive in Tips and Tricks.

Here is the files breakdown. All the files are included in the tutorial data package. They can also be downloaded from the Gemini Observatory Archive (GOA).

Science
N20080830S0261 (900 nm)
N20080830S0262 (890 nm)
N20080830S0265 (880 nm)

Science biases
N20080830S0527-531

Science flats
N20080830S0260 (900 nm)
N20080830S0263 (890 nm)
N20080830S0264 (880 nm)

Science arcs
N20080830S0491 (900 nm)
N20080830S0492 (890 nm)
N20080830S0493 (880 nm)

Standard (G191B2B)
N20190902S0046 (900 nm)

Standard biases
N20081011S0313-317

Standard flats
N20081010S0534 (900 nm)

Standard arc
N20081010S0552 (900 nm)

BPM
bpm_20010801_gmos-n_EEV_22_full_3amp.fits