NGC6822 Scan 153


Observing log information

  Object:           NGC6822
  On scan num:      153 155 157
  Off scan num:     154 156 158
  R.A.:             19.748929 hrs
  Dec.:             -14.801314 deg
  On azimuth:       159.380694 deg
  On zenith dist.:  55.584433 deg
  Off azimuth:      159.338295 deg
  Off zenith dist.: 55.594611 deg
  MJD:              52353
  UTC:              0.500359
  Center freq.:     1420.802312 MHz
  Doppler:          0.00008896
  Num. correlators: 2
  Spectrom. atten.: 35 42 dB
  Bandwidth:        10.0 MHz
  Num. channels:    1024
  Eff. integration: 900 seconds

Raw spectrum

This spectrum is the integration of all data for the scan with spectra from both polarizations added together. The spectral intensities are Ssys * (on - off) / off, where Ssys is the system temperature in Jy. The system noise flux density equivalent is calibrated for each scan with a calibration noise source firing during each scan. The cal value, in Jy, is calibrated by comparison with a number of continuum sources as described in the summary web page

Figure 1. Unedited spectrum

Measured spectrum

This is the section of spectrum measured to obtain the parameters listed below. The three horizontal dotted lines are the baseline, the peak level selected, and 20% of the peak level. The two vertical dotted lines mark the selected 20% line width edges. The solid horizontal line marks the velocity range chosen for the the line profile flux density integral. This spectrum has a second-order least squares fit baseline removed using most of the baseline shown in Figure 1.

Figure 2. Measured spectrum

Measured parameters

  Peak intensity:     11.733 Jy
  Lower 20% velocity:  -89.1 km/s
  Upper 20% velocity:  -29.9 km/s
   Systemic velocity:  -59.5 km/s
   Line width (20%):    59.2 km/s
  Profile integral:   466.76 Jy * km/s
                 A:   428.79
                 B:   470.51
         Ratio B/A:   1.097
  Flux integral
     velocity range:  -135.3 -  -17.9 km/s


quite confused with local HI