Karen O'Neil, Frank Ghigo

Set-up

• L-band
• 50MHz Bandwidth
  
• 2048 lags
  
• 1 Quad
  
• 8 samplers
  
• 9-level
  
• Linear Polarization
• Band centers offset by 5 MHZ (IF2=13075,13080,13085,13090)
• Observing using position-switching technique

Summary

• Pointing correction was less than 1'.
• Baselines for polarization Y showed a 50MHz ripple (the size of the bandwidth) about 50% of the time. This was not seen for pol. X.
• One observing pair, 39/40, show extremely bad baselines in all IF channels. No individual scan appeared responsible for this behavior
• The inferred sensitivity at 1.4GHz was 1.73 and 1.80 K/Jy for polarizations X & Y, respectively.
• The bandpass shapes and rms levels for the four IFs were virtually identical and equal to the theoretical prediction.
• The determined velocities and fluxes for UGC 9179 agreed, within errors, with those found by Rick Fisher in his Galaxy HI survey
• This mode is ready for general use although observers should be aware of the 50MHz baseline ripple.

Observations

• Data taken on 19 Feb, 2003
  
• Data file is T_LBAND_19FEB03
  

  Scan	Source	ON time	Comments
  25,26	UGC 9179	60s	RA offset=-15' (too small, catches source in off)
  27-30	3C295	N/A	Pointing observations
  31,32	UGC 9179	60s	RA offset=-15' (too small, catches source in off)
  33,34	UGC 9179	300s	RA offset=-87'
  35,36	UGC 9179	300s	RA offset=-87'
  37,38	UGC 9179	300s	RA offset=-87'
  39,40	UGC 9179	300s	RA offset=-87'
  41,42	UGC 9179	300s	RA offset=-87'
  43-50	JUNK
  51,52	3C295	300s	Position Switched observation; RA offset=-87'

Analysis

I. Calibrator - 3C295

Gain inferred from this calibrator was 1.73 & 1.80 for pol. X & Y, respectively. RFI was seen in the calibrator scans every 0.5MHz, with the largest peaks seen at 1399.97, 1409.97, 1430.2, 1432.2 and 1434.2 MHz. The reduced spectrum for IF1 is shown below.

Fig. 1. IF1 for the spectrum of 3C295

Other 3C295 plots available are:

• IF 2
• IF 3
• IF 4
• Combination of all 4 IFs
• All four IFs, overlain

II. Galaxy - UGC 9197o

Five 600s and two 120s positioned-switched observations were made of U9197o. The 120s observations had only 15' between the on and off source observations. As a result, the source was in both the on and off-source observations. Of the 600s scans, only one (39/40) showed any problems while the rest of the scans were fine, albeit 50% showed a 50 MHz ripple in the bandpass of pol. Y, as shown in the averaged scan below.

Fig 2. IF1 for scans 33/34.

Fig 3. IF2 for scans 33/34.

In the one data pair which was unuable, individually none of the subscans look bad. Collectively, though, the reduced data show base lines with considerable structure throughout, particularly in pol. Y. This behavior was the same in all four IFs. The reduced data is shown below.

Fig 4. IF1 for scans 39/40.

For the good data the measured flux, peak, and velocity widths of UGC 9179 falls within the errors of the flux published by Rick Fisher for all IFS and all polarizations. The average of all 4 good 600s scans is below:

Fig 5. Average of scans 33/34, 35/36, 37/38, 41/42 and all IFs.

III. RMS

The rms noise for polarizations X and Y ranged from 0.07 - 0.08 (for the four good scans), with no discernable difference between the four IFs. The RMS of the four averaged scans, with all IFS averaged, was 3.5 and 4.3 mK for polarizations X and Y, respectively. Assuming a Tsys of 18.9 and 18.5 K for the two polarizations (taken from the average values) gives a theoretical value of 3.6 & 3.5 mK (using the full RMS formula given in the GBT observer's manual: