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include <gset.h>
# EQWIDTH_CP -- Equivalent width following algorithm provided by
# Caty Pilachowski. This assumes a Gaussian line profile
# and fits to the specified core level, the width at the
# specified flux level above the core, and the specified
# continuum. The line position is found by searching
# near the vertical cursor for the nearest minimum.
define LEFT 1 # Fit to left edge
define RIGHT 2 # Fit to right edge
define BOTH 3 # Fit to both edges
procedure eqwidth_cp (sh, gfd, center, cont, ylevel, y, n, key, fd1, fd2,
xg, yg, sg, lg, pg, ng)
pointer sh
int gfd
real center, cont, ylevel
real y[n]
int n
int key
int fd1, fd2
pointer xg, yg, sg, lg, pg # Pointers to fit parameters
int ng # Number of components
int i, i1, i2, isrch, icore, edge
double xleft, xright, rcore, rinter, yl, gfwhm, lfwhm, flux, eqw, w, w1, w2
double xpara[3], ypara[3], coefs[3], xcore, ycore
double shdr_lw(), shdr_wl()
# Initialize reasonable values
# isrch -- nr of pixels on either side of cursor to search for min
data isrch /3/
begin
# Check continuum.
if (cont <= 0.) {
call eprintf ("Continuum cannot be less than zero.\n")
return
}
# Determine which edges of the line to use.
switch (key) {
case 'a', 'l':
edge = LEFT
case 'b', 'r':
edge = RIGHT
default:
edge = BOTH
}
# Search for local minimum or maximum
icore = max (1, min (n, nint (shdr_wl (sh, double(center)))))
i1 = max (1, icore-isrch)
i2 = min (n, icore+isrch)
# If half lines is selected, restrict the search
if (edge == LEFT)
i2 = max (i2-2, icore+1)
if (edge == RIGHT)
i1 = min (i1+2, icore-1)
# Search for core.
# Someday it may be desirable to use parabolic interpolation
# to locate an estimated minimum or maximum for the region
do i = i1, i2 {
if (abs (y[i] - cont) > abs (y[icore] - cont))
icore = i
}
# Fit parabola to three points around minimum pixel
xpara[1] = icore - 1
xpara[2] = icore
xpara[3] = icore + 1
ypara[1] = y[icore-1]
ypara[2] = y[icore]
ypara[3] = y[icore+1]
call para (xpara, ypara, coefs)
# Compute pixel value at minimum
xcore = -coefs[2] / 2.0 / coefs[3]
ycore = coefs[1] + coefs[2] * xcore + coefs[3] * xcore**2
# Locate left and right line edges. If the ylevel is INDEF then use
# the half flux point.
if (IS_INDEF (ylevel))
yl = (cont + ycore) / 2.
else
yl = ylevel
rcore = abs (ycore - cont)
rinter = abs (yl - cont)
if (rcore <= rinter) {
call eprintf (
"Y cursor must be between the continuum and the line core\n")
return
}
# Bound flux level of interest
if ((edge == LEFT) || (edge == BOTH)) {
for (i=icore; i >= 1; i=i-1)
if (abs (y[i] - cont) < rinter)
break
if (i < 1) {
call eprintf ("Can't find left edge of line\n")
return
}
xleft = float (i) + (yl - y[i]) / (y[i+1] - y[i])
if (edge == LEFT)
xright = xcore + (xcore - xleft)
}
# Now bound the right side
if ((edge == RIGHT) || (edge == BOTH)) {
for (i=icore; i <= n; i=i+1)
if (abs (y[i] - cont) < rinter)
break
if (i > n) {
call eprintf ("Can't find right edge of line\n")
return
}
xright = float (i) - (yl - y[i]) / (y[i-1] - y[i])
if (edge == RIGHT)
xleft = xcore - (xright - xcore)
}
# Compute in wavelength
w = shdr_lw (sh, double(xcore))
w1 = shdr_lw (sh, double(xleft))
w2 = shdr_lw (sh, double(xright))
# Apply Gaussian model
gfwhm = 1.665109 * abs (w2 - w1) / 2. / sqrt (log (rcore/rinter))
lfwhm = 0.
rcore = ycore - cont
flux = 1.064467 * rcore * gfwhm
eqw = -flux / cont
call printf (
"center = %9.7g, eqw = %9.4g, gfwhm = %9.4g\n")
call pargd (w)
call pargd (eqw)
call pargd (gfwhm)
if (fd1 != NULL) {
call fprintf (fd1, " %9.7g %9.7g %9.6g %9.4g %9.6g %9.4g %9.4g\n")
call pargd (w)
call pargr (cont)
call pargd (flux)
call pargd (eqw)
call pargd (ycore - cont)
call pargd (gfwhm)
call pargd (lfwhm)
}
if (fd2 != NULL) {
call fprintf (fd2, " %9.7g %9.7g %9.6g %9.4g %9.6g %9.4g %9.4g\n")
call pargd (w)
call pargr (cont)
call pargd (flux)
call pargd (eqw)
call pargd (ycore - cont)
call pargd (gfwhm)
call pargd (lfwhm)
}
# Mark line computed
call gline (gfd, real(w), cont, real(w), real(ycore))
call gline (gfd, real(w1), real(yl), real(w2), real(yl))
w1 = w - 2 * gfwhm
w2 = cont + rcore * exp (-(1.665109*(w1-w)/gfwhm)**2)
call gseti (gfd, G_PLTYPE, 2)
call gseti (gfd, G_PLCOLOR, 2)
call gamove (gfd, real(w1), real(w2))
for (; w1 <= w+2*gfwhm; w1=w1+0.05*gfwhm) {
w2 = cont + rcore * exp (-(1.665109*(w1-w)/gfwhm)**2)
call gadraw (gfd, real(w1), real(w2))
}
call gseti (gfd, G_PLTYPE, 1)
call gseti (gfd, G_PLCOLOR, 1)
# Save fit parameters
if (ng == 0) {
call malloc (xg, 1, TY_REAL)
call malloc (yg, 1, TY_REAL)
call malloc (sg, 1, TY_REAL)
call malloc (lg, 1, TY_REAL)
call malloc (pg, 1, TY_INT)
} else if (ng != 1) {
call realloc (xg, 1, TY_REAL)
call realloc (yg, 1, TY_REAL)
call realloc (sg, 1, TY_REAL)
call realloc (lg, 1, TY_REAL)
call realloc (pg, 1, TY_INT)
}
Memr[xg] = w
Memr[yg] = rcore
Memr[sg] = gfwhm
Memr[lg] = lfwhm
Memi[pg] = 1
ng = 1
end
# PARA -- Fit a parabola to three points
procedure para (x, y, c)
double x[3], y[3], c[3]
double x12, x13, x23, x213, x223, y13, y23
begin
x12 = x[1] - x[2]
x13 = x[1] - x[3]
x23 = x[2] - x[3]
if (x12 == 0. || x13 == 0. || x23 == 0.)
call error (1, "X points are not distinct")
# Compute relative to an origin at x[3]
x213 = x13 * x13
x223 = x23 * x23
y13 = y[1] - y[3]
y23 = y[2] - y[3]
c[3] = (y13 - y23 * x13 / x23) / (x213 - x223 * x13 / x23)
c[2] = (y23 - c[3] * x223) / x23
c[1] = y[3]
# Compute relative to an origin at 0.
c[1] = c[1] - x[3] * (c[2] - c[3] * x[3])
c[2] = c[2] - 2 * c[3] * x[3]
end
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