NGC3321 Scan 646


Observing log information

  Object:           NGC3321
  On scan num:      646
  Off scan num:     647
  R.A.:             10.647392 hrs
  Dec.:             -11.648202 deg
  On azimuth:       149.051709 deg
  On zenith dist.:  55.408603 deg
  Off azimuth:      148.983555 deg
  Off zenith dist.: 55.434000 deg
  MJD:              52242
  UTC:              0.402685
  Center freq.:     1408.853130 MHz
  Doppler:          0.00009489
  Num. correlators: 2
  Spectrom. atten.: 31 38 dB
  Bandwidth:         5.0 MHz
  Num. channels:    1024
  Eff. integration: 300 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. Narrow band interference was removed from 5 channels by interpolation between the nearest valid channels

Figure 2. Measured spectrum

Measured parameters

  Peak intensity:      0.110 Jy
  Lower 20% velocity: 2345.0 km/s
  Upper 20% velocity: 2629.4 km/s
   Systemic velocity: 2487.2 km/s
   Line width (20%):   284.4 km/s
  Profile integral:   20.99 Jy * km/s
                 A:   16.89
                 B:   21.78
         Ratio B/A:   1.290
  Flux integral
     velocity range:  2327.6 - 2648.2 km/s