4.1. Example 1 - Datasets descriptions

4.1.1. Dithered Point Source Longslit

This is a GMOS longslit observation. The primary target is a DB white dwarf candidate. We will use this observation to show how a basic longslit sequence is reduced with DRAGONS. The sequence dithers along the dispersion axis and along the slit. DRAGONS will adjust for the difference in central wavelength and spatial positions, and then stack the aligned spectra automatically.

The data were obtained in 2017 using the B600 grating on GMOS South. GMOS was equipped with the Hamamatsu detectors at the time. The central wavelengths are 515 nm and 530 nm. We are using a subset of the original sequence to keep the data volume low. The effective sequence is:

[Science, Flat,  Science, Arc], [Science, Flat, Science, Arc]

with the first group of four at 515 and the second at 530 nm. The spectrophotometry standard was obtained about a month before 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 2x2 binning GMOS-S 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.

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

Science
S20171022S0087,89 (515 nm)
S20171022S0095,97 (530 nm)

Science biases
S20171021S0265-269
S20171023S0032-036

Science flats
S20171022S0088 (515 nm)
S20171022S0096 (530 nm)

Science arcs
S20171022S0092 (515 nm)
S20171022S0099 (530 nm)

Standard (LTT2415)
S20170826S0160 (515 nm)

Standard biases
S20170825S0347-351
S20170826S0224-228

Standard flats
S20170826S0161 (515 nm)

Standard arc
S20170826S0162 (515 nm)

BPM
bpm_20140601_gmos-s_Ham_22_full_12amp.fits