NGC4948 Scan 1


Observing log information

  Object:           NGC4948
  On scan num:      1 7 57 59 61 63 65 67 69 71
  Off scan num:     2 8 58 60 62 64 66 68 70 72
  R.A.:             13.082138 hrs
  Dec.:             -7.946560 deg
  On azimuth:       118.770498 deg
  On zenith dist.:  69.623092 deg
  Off azimuth:      118.788862 deg
  Off zenith dist.: 69.606471 deg
  MJD:              52806
  UTC:              0.874028
  Center freq.:     1414.382099 MHz
  Doppler:          -0.00008897
  Num. correlators: 2
  Spectrom. atten.: 0 0 dB
  Bandwidth:        12.5 MHz
  Num. channels:    8192
  Eff. integration: 2940 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

Edited spectrum

This spectrum is the same as Figure 1 but with 4 60-second sub-integrations manually deleted because of interference or a bad baseline.

Figure 2. Edited 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 third-order least squares fit baseline removed using most of the baseline shown in Figure 2.

Figure 3. Measured spectrum

Measured parameters

  Peak intensity:      0.031 Jy
  Lower 20% velocity: 1265.2 km/s
  Upper 20% velocity: 1435.9 km/s
   Systemic velocity: 1350.5 km/s
   Line width (20%):   170.7 km/s
  Profile integral:    4.45 Jy * km/s
                 A:    4.00
                 B:    4.90
         Ratio B/A:   1.224
  Flux integral
     velocity range:  1244.9 - 1450.3 km/s