AIPS HELP file for WARP in 31DEC24
As of Fri Apr 26 2:00:12 2024
WARP: Task to model warps in galaxies
INPUTS
INNAME Image name (name)
INCLASS Image name (class)
INSEQ 0.0 9999.0 Image name (seq. #)
INDISK 0.0 9.0 Disk drive #
IN2NAME Image name (name)
IN2CLASS Image name (class)
IN2SEQ 0.0 9999.0 Image name (seq. #)
IN2DISK 0.0 9.0 Disk drive #
BLC 0.0 4096.0 Bottom left corner of image
0=>entire image
TRC 0.0 4096.0 Top right corner of image
0=>entire image
FACTOR 0.0 1.0 Convergence criterion
0=> 0.001
FUNCTYPE Rot. curve type. 'EX': Expo-
nential, def: constant.
APARM (1),(2) central position;(3),
(4) first guesses to p.a., i.
(5) Vsys;(6) Vmax;(7) Rmax;
(9) 1: residual map(s)
CPARM (4),(5),(6): R(min,max,inc);
(7),(8) guesses b and d in
pa = a + b*R, i = c + d*R.
PIXSTD Estimated rms uncertainty in
the observed radial velocity
at one pixel. 0=>10000
HELP SECTION
WARP
Type: Task
Use: Adverbs:
INNAME......Image name(name). blank=>any
INCLASS.....Image name(class). blank=>any
INSEQ.......Image name(seq. #). 0=>any
INDISK......Disk drive # of image. 0=>any
IN2NAME.....Image name(name) second input map. blank=>no
second input map.
IN2CLASS....Image name(class). blank=>any
IN2SEQ......Image name(seq. #). 0=>any
IN2DISK.....Disk drive # of image. 0=>any
BLC.........The Bottom Left-hand pixel of the subarray of
the image to be analysed. The value (0,0)
means (1,1).
TRC.........The Top Right-hand pixel of the subarray of
the image to be analysed. The value (0,0) means
the top right hand corner of the entire image.
FACTOR......Criterion to stop least squares fitting.
FUNCTYPE....Type of rotation curve to be fitted.
'EX' : Exponential flat curve :
- ln(100.0) * (R / Rmax)
V / Vmax = 1 - e
'CC' : Constant curve (default) :
V / Vmax = 1
APARM.......Same is in GAL.HLP, only (3) and (4) are now ini-
tial guesses, others remain constant.
CPARM (4),(5) Rmin,Rmax. (6) Rinc: width of radius in
which root is sought. (7),(8) guesses b and d in
pa = a + b*R, i = c + d*R.
PIXSTD......Estimated rms uncertainty in observed radial
velocity at one pixel.
EXPLAIN SECTION
WARP : Task which analyzes a velocity field, and models the variation
of position angle and inclination with radius. It is advisible to
use GAL first, and use the resulting central position and systemic
velocities in WARP. Only linear variations are assumed, so
strongly warped galaxies may not be modeled correctly. It can also
model velocity fields with double profiles. In that case, make two
velocity fields, one with velocities using only the profiles
closest to the systemic velocity, and one using the other profiles.
Two such maps can most easily be made using the task XGAUS.
The program searches for roots of the following equation :
r = r (R, pa(R), i(R)),
where r is the observed (projected) radius, pa and i the position
angle and the inclination, and R the unknown true radius. Clearly,
for constant pa and i, there is at most one root, and this R can be
calculated directly, as is done in the task GAL. For varying pa
and i, more than one root is possible, as is demonstrated by the
occurrence of double profiles. The search is performed by the
subroutine WORTEL, which begins its search at R = r, and ends at
Rmax, specified by CPARM(5) It first looks if in the interval (r,
r + increment) the sign of r (R) changes. If so, the root in the
interval is determined. Then the search continues in the next
interval, and this is repeated until Rmax is reached. The size of
the increment is specified by CPARM(6). It should be chosen small
enough to separate neighbouring roots, but not so small to cause an
unnecessary increase in CPU time. The total number of roots found
clearly depends strongly on Rmax, which should be chosen larger
than the largest radius expected. A too low choice of Rmax may
cause pixels to be discarded if the current values of pa and i are
off, whereas a too high choice again results in a waste of CPU
time. If the model results in two (or more) roots in the line of
sight, it will attribute the lowest root to the value in map 2, and
the next root to the value in map 1. If only one root is found in
the line of sight, it is attributed to the value in map 1.
WARP assumes that you have two input maps if you provide a
non-blank IN2NAME. If IN2NAME is blank, it assumes only one input
map, and it always takes the first root it encounters. If APARM(9)
= 1, you will get one or two (depending on the number of input
maps) residual maps, with the same names and volume numbers as the
input maps, but with class RESID1 and RESID2.