The kmos_combine recipe

kmos_combine

Synopsis

Combine reconstructed cubes

Description

This recipe shifts several exposures of an object and combines them. Diffe- rent methods to match the exposures are described here (–method parameter).

The output cube is larger than the input cubes, according to the shifts to be applied. Additionally a border of NaN values is added. The WCS is the same as for the first exposure.

For each spatial/spectral pixel a new value is calculated (according the –cmethod parameter) and written into the output cube.

Only exposures with the same WCS orientation can be combined (except -–method=”none”), north must point to the same direction. It is recommended to apply any rotation possibly after combining.

The behavior of the selection of IFUs to combine differs for some templates and can be controlled with the parameters –name and –ifus.

If the input data cubes stem from templates KMOS_spec_obs_mapping8 or KMOS_spec_obs_mapping24 all extensions from all input frames are combined into a single map by default (like in recipe kmo_sci_red). If just the area of a specific IFU should be combined, the parameter –ifus can be specified, or more easily –name.

If the input data cubes stem from other templates like e.g.

KMOS_spec_obs_freedither all extensions of all input frames are combined into several output frames by default. The input IFUs are grouped according to their targeted object name stored in the keywords ESO OCS ARMx NAME. If just a specific object should be combined, its name can be specified with –name. If arbitrary IFUs shoukd be comined, one can specify these with the parameter –ifus.

The default mapping mode is done via the –name parameter, where the name of the object has to be provided. The recipe searches in input data cubes IFUs pointing to that object.

Input files

DO                  KMOS
category            Type   Explanation                  Required #Frames
--------            -----  -----------                  -------- -------
CUBE_OBJECT         F3I    data frame                       Y      2-n

Output files

DO                      KMOS
category                Type    Explanation
--------                -----   -----------
COMBINE_                F3I     Combined data cube
EXP_MASK                F3I     Exposure time mask
SCI_COMBINED_COLL               (optional) Collapsed combined cube
                                (set --collapse_combined)

Constructor

cpl.Recipe("kmos_combine")

Create an object for the recipe kmos_combine.

import cpl
kmos_combine = cpl.Recipe("kmos_combine")

Parameters

kmos_combine.param.name

Name of the object to combine. (str; default: ‘’) [default=”“].

kmos_combine.param.ifus

The indices of the IFUs to combine. “ifu1;ifu2;…” (str; default: ‘’) [default=”“].

kmos_combine.param.method

The shifting method: ‘none’: no shifting, combined directly (default), ‘header’: shift according to WCS, ‘center’: centering algorithm, ‘user’: read shifts from file (str; default: ‘none’) [default=”none”].

kmos_combine.param.fmethod

The fitting method (applies only when method=’center’): ‘gauss’: fit a gauss function to collapsed image (default), ‘moffat’: fit a moffat function to collapsed image (str; default: ‘gauss’) [default=”gauss”].

kmos_combine.param.filename

The path to the file with the shift vectors (method=’user’) (str; default: ‘’) [default=”“].

kmos_combine.param.flux

Apply flux conservation: (TRUE (apply) or FALSE (don’t apply) (bool; default: False) [default=False].

kmos_combine.param.edge_nan

Set borders of cubes to NaN before combining them.(TRUE (apply) or FALSE (don’t apply) (bool; default: False) [default=False].

kmos_combine.param.skipped_frames

Comma separated List of IFUs to skip for the combination. An IFU is specified with R:I.R is the index (start 1) of the recons. frame, I the IFU nb (str; default: ‘’) [default=”“].

kmos_combine.param.suppress_extension

Suppress arbitrary filename extension. (bool; default: False) [default=False].

kmos_combine.param.collapse_combined

Flag to collapse the combined images (bool; default: False) [default=False].

kmos_combine.param.cmethod

Apply “average”, “median”, “sum”, “min_max.” or “ksigma”. (str; default: ‘ksigma’) [default=”ksigma”].

kmos_combine.param.cpos_rej

The positive rejection threshold for kappa-sigma-clipping (sigma). (float; default: 3.0) [default=3.0].

kmos_combine.param.cneg_rej

The negative rejection threshold for kappa-sigma-clipping (sigma). (float; default: 3.0) [default=3.0].

kmos_combine.param.citer

The number of iterations for kappa-sigma-clipping. (int; default: 3) [default=3].

kmos_combine.param.cmax

The number of maximum pixel values to clip with min/max-clipping. (int; default: 1) [default=1].

kmos_combine.param.cmin

The number of minimum pixel values to clip with min/max-clipping. (int; default: 1) [default=1].

The following code snippet shows the default settings for the available parameters.

import cpl
kmos_combine = cpl.Recipe("kmos_combine")

kmos_combine.param.name = ""
kmos_combine.param.ifus = ""
kmos_combine.param.method = "none"
kmos_combine.param.fmethod = "gauss"
kmos_combine.param.filename = ""
kmos_combine.param.flux = False
kmos_combine.param.edge_nan = False
kmos_combine.param.skipped_frames = ""
kmos_combine.param.suppress_extension = False
kmos_combine.param.collapse_combined = False
kmos_combine.param.cmethod = "ksigma"
kmos_combine.param.cpos_rej = 3.0
kmos_combine.param.cneg_rej = 3.0
kmos_combine.param.citer = 3
kmos_combine.param.cmax = 1
kmos_combine.param.cmin = 1

You may also set or overwrite some or all parameters by the recipe parameter param, as shown in the following example:

import cpl
kmos_combine = cpl.Recipe("kmos_combine")
[...]
res = kmos_combine( ..., param = {"name":"", "ifus":""})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

Please report any problems to Alex Agudo Berbel, Y. Jung. Alternatively, you may send a report to the ESO User Support Department.