Calculating (ON - OFF)/OFF for all the frequencies (all scans combined) results in the line profile as shown in figure 4. The line profile was corrected to have a baseline of 0 Jy by fitting a least-square quadratic polynomial to the baseline and then subtracting it from the (ON - OFF)/OFF profile. To obtain flux density scales in figure 4, we used an estimate of the system noise flux density equivalent of 10 Jy (20 Kelvin system temperature and 2 Kelvins/Jy antenna gain). The harmonic at 1290 MHz was removed by setting those frequency channels equal to the average of the neighboring channels. The abscissa is converted to Heliocentric velocity from frequency. On the day of observation, the correction due to the component of Earth's orbital velocity along the line of sight was -28.2914 km/s ([Giorgini et al.(1996)]), the negative sign implying that this component is toward the galaxy.
[After blanking] [Before blanking (the dashed lines represent the same lines as in f:line_profile_blanked)]
[Same as f:line_profile_unblanked, but zoomed in to show the profile in detail]
In the figure 4(a), we have also plotted the peak intensity level, the baseline level, and the line corresponding to 20% of the peak intensity level. The line-profile width at which the profile intensity goes to 20% of the peak intensity, W20 is a commonly used parameter to estimate to characterize the width of the HI profile of a galaxy.
Integrating the line profile gives a flux of 1.67 Jy km/s. The various galaxy parameters as measured from the profile are shown in table 1.
The average equivalent radar intensity in figure 3(b) is 2 Jy, which is 500 time the galaxy profile intensity.