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Description of INVENTORY Keywords

There are several keywords in the context keyword area which hold the values of parameters which control the performance of INVENTORY. They are listed here. Additional information is also supplied (separated by slashes): Keyword type -- Integer (I) or Real (R) -- and the maximum number of values stored by a keyword. A description is added following each keyword.
-- Default value of this keyword is equal to 0 and corresponds to the case that only the base version of the command ANALYSE/INV is used. Any positive value sets the number of additional iterations. In each of these iterations the contributions from stellar neighbours are subtracted using the empirical one-dimensional point spread function.
-- Divides objects into bright and faint for classification purposes. Should be close to the magnitude corresponding to the beginning of saturation effects.
-- Parameter, which helps to remove spurious faint components of large bright objects. May modify central parts of real objects. Should be disabled by setting to zero when photometric accuracy is important.
-- Many spurious faint objects are detected around very bright ones when this keyword is set to 0. Increasing it helps to eliminate spurious objects. Too large a value may result in disapearance of some real objects.
-- Controls the selection of seed objects for classification. The first component defines half-width of stellar objects band in a magnitude versus relative gradient plot. The second value sets an upper limit for relative gradient for seed galaxies. The third component tells how much brighter in magnitudes the seed objects should be in relation to the limiting magnitude. All three components are used in CLASSIFY/INV. The first component is also used in ANALYSE/INV for picking out objects similar to stars.
-- Controls the calculation of sky background with the help of the subroutine MODE. This subroutine returns the modal value of the pixel distribution when CTRLMODE is set to 3.0. Repetitively clipped means it is returned when CTRLMODE is set to 0.0, with some saving of the execution time.
-- Stops iterations in subroutine MODE, when the difference between the last two iterations for mode is smaller than the last $\sigma$ multiplied by CFCT. Recommended value is 5.0. Smaller values increase execution time with only little improvement of accuracy. Larger values may harm the accuracy.
-- us used ti invoke debuging outputs.
-- Required depth of valley between two components that is necessary for accepting them as two separate objects. Recommended value is 0.02.
-- Limiting distance in a parameters space for including object in a particular class of objects. Used in CLASSIFY/INV
-- Image elongation above which an object is checked for duplicity. Recommended value is 0.25.
-- Petrosian $\eta$-function used in the determination of the Petrosian radius and Petrosian magnitude. Berkeley astronomers are using a value of 2.0. When working with many automatically detected faint objects this large value often fails to give consistent results for all objects. Therefore a smaller value, such as 1.5, is recommended. The value 1.39 corresponds roughly to de Vaucouleur's definition of ``half luminosity radius''.
-- Time of exposure expressed in units referred to in keyword ZEROMAGN.
-- Concerns the character of variations of sky background. It is set to 0 when these variations are additive. It is 0 when they are due to sensitivity changes.
-- Sets slevel of bright pixel filtering.
-- Extend in pixels of 2-dimensional p.s.f.
-- Defines size of a subarray that is used for calculating local sky background, and for profile analysis. It is equal to a distance, measured in pixels, between the central pixel and an edge of a subarray. The size of a subarray is equal to $(1+2\times{\rm IHED})^2$. IHED cannot be larger than 50, so that the maximum size of a subarray is $101\times101$  pixels. Objects of interest should be smaller than the subarray. If the value 50 is too small, then the image should be squeezed. Minimal value is 4. Recommended value for most of applications is between 8 and 12.
-- Sets limits of the investigated area.
-- Controls use of outside values of isophotal radia. When set to 1, then isophotal radia are read from column RAD_ISO into an input table. It is useful when measuring colours of galaxies.
-- Condition for terminating iterations during classification and allowable number of iterations.
-- Low and high cuts applied for more correct treatment of bad pixels and saturated regions. The low cut should be smaller than any valid data. The high cut should be little less than the image saturation level. It is advisable to look carefully at images of bright stars with the help of the image display in order to set a high cut.
-- Width in pixels of frame margins where objects are not detected.
-- Allowed separation of pixels at multiple detections. Individual detections separated not more than by MULTDTCT pixels are treated as the same detection.
-- Used in cases when faint members of clusters of galaxies pretend to be very large. In all other cases should be disabled by setting to zero.
-- Half edge of the regions used to determine preliminary sky background in a net of regions.
-- Sets number of pixels spaced points of objects' profiles recorded in output table.
-- Allowed minimal separation of double objects expressed in pixels. Should be little larger than the size of the seeing disk.
-- Parameters used for profile cleaning.
-- Tells if searched area is defined by physical coordinates.
-- Gives the number of central points of the standard Point Spread Function to be updated by program. Input profile as given by keywords SPROFILx and is used when PRFLCRTL is 0. N central points are updated with the help of stars selected by program when PRFLCRTL is +n, and the program will ask for selecting stars with the help of the cursor when PRFLCRTL is -n. Usually 5 or 6 is sufficient. May depend on frame origin, seeing and pixel size.
-- Factor used to set clipping limits in subroutine MODE. Recommended value is 2.0.
-- Sets accuracy of the sky background determination.
-- Radii of two circular apertures used to determine aperture magnitudes. They are expressed in pixels.
-- Innermost 25 points of one dimensional logarithmic differential Point Spread Function. The spacing of entries is by one pixel. Each k-th value is equal to decimal logarithm of k-1 value of the stellar Point Spread Function divided by its k-th value.
-- Limiting threshold above sky background level used at object detection and at calculating isophotal magnitudes and sizes. It is expressed in units of sky background. Too low a value results in many spurious detections and corresponding long execution time. It is advisable to start with a relatively large value of TRESHOLD and check it on a small part of a frame defined with the help of the EXTRACT command.
-- Undersampling factor.
-- Switched between background units (0) and instrumental units (1)
-- Limits of investigated area in physical units.
-- The ratio of ``Y'' to ``X'' dimensions of a box used at duplicity check. Recommended value is 0.6.
-- Sets a zero point of magnitudes. Its use is controlled by keyword MGNTCTRL.

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Next: Formats of Tables Up: Object Search and Classification Previous: The Classification
Petra Nass