Spectroscopic mode tutorial: MOS data

This tutorial provides an easy introduction to the use of PyEmir (via Numina), focusing on the rectification and wavelength calibration of EMIR spectroscopic images.

For detailed documentation concerning the installation of PyEmir, see PyEmir Installation.

As shown in the previous diagram, PyEmir helps to generate a rectified and wavelength calibrated 2D image. From this point, the astronomer can use her favourite software tools to proceed with the spectra extraction and analysis.

The rectification and wavelength calibration of the original 2048x2048-size raw images generates reduced 3400x2090-size images. The spatial and spectral sampling of the raw images are preserved, as much as possible (to minimise resampling problems) in the reduced images, and the spectral direction axis is enlarged to acommodate the varying wavelength ranges covered by the slitlet spectra depending on the location of the slitlets on the plane defined by the CSU (Cold Slit Unit).

At present, PyEmir is able to work with raw images obtained with the following spectroscopic configurations:

Grism	Filter	Useful slitlets	CRVAL1	CDELT1	NAXIS1	NAXIS2
HR J	J	2 - 54	11200	0.77	3400	2090
HR H	H	2 - 54	14500	1.22	3400	2090
HR K	Ksp	2 - 54	19100	1.73	3400	2090
LR	YJ	4 - 55	8900	3.56	1270	2090
LR	HK	4 - 55	14500	6.83	1435	2090

In the previous table, CRVAL1, CDELT1, NAXIS1 and NAXIS2 correspond to the values for the rectified and wavelength calibrated images.

We strongly recommend to follow the different sections of this tutorial in the provided order, starting with the simple handling of (pseudo) longslit data and then facing the proper reduction of MOS observations.

Tutorial index:

• Understanding the data: image distortions
• Simple example: arc exposure
  • Preliminary rectification and wavelength calibration
  • Refined rectification and wavelength calibration
• MOS example
  • Downloading the tutorial data
  • The CSU configuration
  • Preliminary rectification and wavelength calibration using OH lines
  • Refined rectification and wavelength calibration
  • Fast ABBA combination
  • Careful ABBA combination
  • Using a different rectification and wavelength calibration for each image
• NGC7798
  • Reduction of HD209290
  • Reduction of NGC7798