### SECTOR

May be used to display the average pixel values within a wedge shaped sector/slice of the image

#### Description:

May be used to display the average pixel values within a wedge shaped sector/slice of the image. The sector is in the form of a wedge (of user defined size) drawn outward from the galaxy origin point.

The results are displayed as mean pixel value (in terms of level relative to sky or surface brightness) versus distance from the galaxy origin. Pixel count values are summed over all the pixels at a given distance from the origin.

Options include:

• summing pixels taken from two equal sized, but diametrically opposite, sectors.

• displaying data using a number of possible radius transformations.

• the use of a graphics cursor to select the image object to be examined.

• refinement of approximate galaxy centre positions if required.

• automatic selection of the maximum radius out from the origin to be considered.

The application is not intended to replace ELLPRO or ELLFOU profiling application, but merely to allow the user to obtain quickly a first approximation to the brightness cross-section of an interactively selected galaxy.

#### Usage:

SECTOR CURSOR ARDFIL BACK SIGMA PSIZE SURF RADISP MIRROR AUTOL ZEROP OUT [IN] [DEVICE] [IMGDEV] [FITLIM] [POSANG] [ANGWID] [RLIM] [SAME] [AGAIN] [ORIGIN] (COLOUR)

#### Parameters:

Should another profile be attempted?
The angular width of the slice/wedge/sector to be considered. Units degrees.
The name of an ARD file to be used to mask out regions of the image that are not to be used.
##### AUTOL = _LOGICAL
Is a simple method to be applied to get a better estimate of the galaxy centre position? The accuracy of the method used is no better than 1 pixel.
The background value for the image. Units counts.
Colour used when showing the galaxy centre and profiling radius.
Whether the galaxy location is to be identified using the graphics cursor or the keyboard.
The name of the display device on which the results graphs should be displayed.
The range of radius values over which the scale length ’fits’ are to be calculated. Units arc seconds.
Name of the graphics device displaying the image.
The name of the source NDF data structure/file.
Whether the summation is to be taken from two sectors/wedges/slices of the same size, but on diametrically opposite sides of the galaxy origin.
Image indices for the origin point to be used. Given in the Current coordinate system of the WCS component of IN.
Image indices for the origin point to be used, in pixel units. This parameter is present to aid the interface with the GAIA system. It should be regarded as an ‘internal’ parameter, and may disappear or change without notice. If present, the value of this parameter overrides any value specified by the ORIGIN parameter.
File name for the output text file containing the profile data.
The position angle of the sector relative to the top of the image. Convention is clockwise increases angle and the image Y axis represents 0 degrees. Units degrees.
The size of each pixel in arc seconds. If the image contains a SKY co-ordinate frame this value will be determined automatically.
The display mode used for the radius axis of the graphs.
• Q=quarter power

• L=logarithmic

• S=square root

• R=linear

Distance out from the origin at which the sector stops. Values are input as arc seconds, but the program works in pixels. A value of 0 causes the application to automatically select the distance at which to stop.
Should the graphs be displayed on the same device as the original image?
The standard deviation of the background value. Units counts.
sector cursor=true ardfil=^ardup.dat back=6200 sigma=390 psize=0.96 surf=true radisp=r mirror=true autol=true zerop=27.5 out=x2windows device=x2windows imgdev=xwindows same=false
sector cursor=false ardfil=^ardfile.dat back=760 sigma=23 surf=true radisp=q mirror=false autol=false zerop=26.4 in=ic3374 out=ic3374.pro device=xwindows fitlim=0,20 posang=25 angwid=5 rlim=25 origin="12:36:53.42 62:12:21.8"