Karen O'Neil

Set-up

• L-band
• 200Hz Bandwidth
  
• 4096 channels
  
• 1 Quad
  
• 4 samplers (total)
  
• 1 IF/pol/bank
• 3-level
  
• Linear Polarization
• Observing using position-switching technique

Summary

• Pointing corrections was less than 1'.
• All of the data has fairly ratty baselines, with approx 50-60 MHz ripples.
• The bandpass shapes and rms levels for the IFs/samplers for each bank were virtually identical.
• The determined velocities for UGC 9179 agreed, within 10%, with those found by Rick Fisher in his Galaxy HI survey (and with other published values). Due to the poor baselines, though, the fluxes vary quite a bit from the published values (they are off by 30%) and the measured rms values are higher than the theoretical ones.
• Although this mode passes the spectrometer checkout, observers should be wary of the baselines.

Observations

• Data taken on 08/09 April, 2003
  
• Data file is T_LBAND_08APR03
  

  Scan	Source	ON time	Comments
  85,86	UGC 9179	60s	RA offset=-87'
  87,88	UGC 9179	60s	RA offset=-87'
  89,90	UGC 9179	300s	RA offset=-87'
  91,92	UGC 9179	300s	RA offset=-87'
  93,94	UGC 9179	300s	RA offset=-87'
  95,96	UGC 9179	300s	RA offset=-87'
  97,98	3C295	60s	RA offset=-87'

Analysis

I. Calibrator - 3C295 Gain inferred from this calibrator was 2.10/2.19 & 1.90/2.00 for pol. X/Y and IFs 1 & 2, respectively. The values are likely high due to the large ripples in the baseline which made determining the true gain difficult. The reduced spectrum are shown below.

Fig 1. 3C295, IF1.

Fig 2. 3C295, IF2.

II. Galaxy - UGC 9179

Four 600s positioned-switched observations were made of U9179. In all cases, the baseline showed considerable structure, as exemplified below:

Fig 3. Baseline in IF 1 for scans 89/90.

Fig 4.Baseline in IF2 for scans 89/90.

Fig 5. Baseline in IF 1 for all scans, averaged.

Fig 6.Baseline in IF2 for all scans, averaged.

The measured flux and peak of UGC 9179 falls about 30% short of the previously published values for both banks and all polarizations (Flux_obs = 85-95 km/s; Flux_{Rick, others}=116 Jy km/s). This is likely due to the dip in the baseline near the galaxy (only a 1st order polynomial was fit for baseline subtraction). The velocity widths and central valocity fall within the errors of previously published values (v_obs = 308 km/s; v_Rick= 304 km/s).

Fig 7. U9179, IF 1, Scan 90.

Fig 8. U9179, IF 2, Scan 90.

Fig 13. Average of all scans for IF 1.

Fig 14. Average of all scans for IF 1.

Fig 15. Average of all scans for IF 2.

Fig 16. Average of all scans for IF 2.

III. RMS

The rms noise for polarizations X and Y ranged from 8 - 12 mK, with no discernable difference between the banks/IFs/samplers. The RMS of the four averaged scans for IF 1 & IF 2 was 3-6 mK for polarizations X and Y. Assuming a Tsys of 17.5K for the two polarizations (taken from the average values) gives a theoretical value of 5 mK for one 600s scan and 3 mK for the average of the four scans. This is a bit lower than the measured values, again due to the large ripples present in the baselines.