lvmsurveysim.ifu

class lvmsurveysim.ifu.IFU(n_fibres=None, centres=None, padding=0, fibre_size=None, allow_rotation=False, name=None)[source]

Bases: object

A generic class representing a LVM hexagonal IFU.

This class is intended to be subclassed into real examples of IFU designs that LVM will use. An IFU is defined by a series of sub-IFU centres (or a single one for a monolithic IFU) and a fibre size, so that the real size of the IFU on the sky can be calculated.

Parameters

  • n_fibres (int) – Number of fibres in each of the sub-IFUs.

  • centres (list) – A list of 2D tuples describing the centres of each of the sub-IFUs. It assumes the diameter of the sub-IFU hexagon is 1.

  • padding (int) – Number of fibres the IFU should overlap when tiling. This will be used to slightly modify the distance between sub-IFUs.

  • fibre_size (float) – The real size, in microns, of each fibre including buffer.

  • gaps (list) – If the IFU is composed of multiple sub-IFUs and gaps exist between them, a list with the same format of centres must be provided, with the list of the hexagonal gap centres.

  • allow_rotation (bool) – Whether this IFU can be rotated.

classmethod from_config()[source]

Returns an IFU object from the configuration file.

get_ifu_size(scale, tile_overlap, sparse)[source]

Returns the size of the IFU in degrees

Calculate and return the size of the IFU in degrees in two dimensions, the first from center to corner of the hexagon (outer radius), the second from center to edge (inner radius). Take into account the amount of overlap we want and the sparse tiling.

Parameters:

scalefloat

The plate scale in degrees per mm.

tile_overlapfloat

The fraction of tile separation to overlap between neighboring tiles (ignored for sparse targets)

sparsefloat

Factor for sparse sampling. Stretches IFU length scale by the number.

Returns:

dx, dytuple of float

The extent of the hexagonal IFU in degrees from center to corner and center to edge scaled by the desired overlap.

get_patch(**kwargs)[source]

Returns a matplotlib patch for the IFU.

Parameters

kwargs (dict) – Parameters to be passed to SubIFU.get_patch.

get_tile_grid(region, scale, tile_overlap=None, sparse=None, geodesic=None)[source]

Returns a grid of positions that tile a region with this IFU.

Parameters

  • region (SkyRegion) – The SkyRegion to tile. It is assumed that x coordinates are RA and y is Declination, both in degrees.

  • scale (float) – The scale in degrees per mm.

  • tile_overlap (float) – The fraction of tile separation to overlap between neighboring tiles (ignored for sparse targets)

  • sparse (float) – Factor for sparse sampling. Stretches IFU length scale by the number.

  • geodesic (use geodesic sphere tiling, sparse gives depth in this case.) –

plot(show_fibres=False, fill=False)[source]

Plots the IFU.

class lvmsurveysim.ifu.SubIFU(id_subifu, parent, centre, n_fibres, fibre_size=None)[source]

Bases: object

Represents a sub-IFU (group of contiguous fibres) within a larger IFU.

A sub-IFU is an hexagonal group of contiguous fibres, separated from other groups of fibres. LVM IFUs are formed by a series of sub-IFUs (a monolithic IFU can be considered as an IFU with a single sub-IFU). It is assumed that all sub-IFUs in an IFU have the same size.

Parameters

  • n_subifu (int) – An integer used to identify the sub-IFU.

  • parent (IFU object) – The parent IFU object.

  • centre (tuple) – A 2D tuple describing the centre of the sub-IFUs. It asumes the diameter of the sub-IFU hexagon is 1.

  • n_fibres (int) – Number of fibres in the sub-IFUs.

  • fibre_size (float) – The real size, in microns, of each fibre including buffer.

get_patch(scale=None, centre=None, pa=None, **kwargs)[source]

Returns a matplotlib patch for the sub-IFU.

Parameters

  • scale (Quantity or float) – The plate scale to be used to convert the IFU to on-sky distances. Either a Quantity or a value in degrees/mm.

  • centre (list) – The coordinates of the centre of the IFU on the sky.

  • pa (float) – The position angle of the IFU on the sky in degrees. Ignored if None.

  • kwargs (dict) – Parameters to be passed to Polygon when creating the patch.

Returns

patch (Polygon) – A Matplotlib patch with the sub-ifu. If scale and centre are passed, the coordinates of the patch are on-sky.

get_patch_collection(ax)[source]

Returns a collection of fibre patches.

lvmsurveysim.ifu.fibres_to_rows(fibres)[source]

Calculates the number of rows for a set of fibres.

Given a total number of fibres, returns the number rows. Given that the IFU is an hexagon, the central row has as many fibres as rows in the IFU. It returns None if the number of fibres can not be arranged in a full IFU.