Description
This function calculates the width and average velocity of a galaxy spectrum.
The two halves of the double horned profile are treated separately. For each
half, the peak is determined (it is assumed that the two peaks are on either
side of the center of the user specified limits first and LAST). Then on each
side of the profile a polynomial (by default 1st order) is fit to a user
specified portion of the profile. If the fit is poor, (i.e. (chisqr -
deg.of.freedom) > 3 times sqrt(2*deg.of.freedom)), the user is given the
option of fitting a 2nd degree polynomial and/or changing the levels between
which to fit. The FR points (where FR is a user specified fraction of the peak
flux) on either side of the profile are located by interpolation between the
two data points that bracket the FR point. The interpolaton is done by channel
number and then the velocity corresponding to the interpolated channel number
is computed. The average velocity is taken to be the mean of these two
velocities
and the width is taken to be the difference between these two velocities. The
uncertainity in the velocity measurment is then calculated from the rms in the
baseline and the coefficients of the fitted polynomial. Finally the area
between the channels first and last is computed as in the other methods.
Example
- d.msr().areape(rms=0.005,levs=[0.8,0.2,0.4],usecurs=T)
Upper and lower profile points of left peak coincide!
Poor fit to profile: the normalized chisqr are nan14.2039694
Number of points used to fit left and right halves are 23
[type=areape, lchans=[329 328 329] , rchans=[351 353 351] , badfit=T,
vwidth=116.518171, vel=1111.61462, vrms=0.109011172, badpeak=F,
limits=[320.401001 358.420601] , fluxint=98.4090931]
Arguments
| lv |
|
an SDRecord |
| |
|
Allowed: |
SDRecord - Not enabled |
| |
|
Default: |
F |
| first |
|
first channel number in range to integrate |
| |
|
Allowed: |
integer |
| |
|
Default: |
F |
| last |
|
last channel number in range to integrate |
| |
|
Allowed: |
integer |
| |
|
Default: |
F |
| levs |
|
define levels relative to each peak flux |
| |
|
Allowed: |
vector |
| |
|
Default: |
[0.8,0.2,0.4] |
| rms |
|
rms of the spectrum (non-line) |
| |
|
Allowed: |
float |
| |
|
Default: |
0.0 |
| usecurs |
|
optionally set ranges with cursor |
| |
|
Allowed: |
boolean |
| |
|
Default: |
F |
| norder |
|
order of the fit |
| |
|
Allowed: |
integer |
| |
|
Default: |
1 |
News 
