[evlatests] L-Band Deep Imaging

[Rick Perley]

    A previous report of a deep field image at X-band provided good 
evidence that the EVLA sees -- and shows! -- the same weak sources that 
the VLA sees.  However, doing this at X-band was not a good choice, for 
although there is a maximum in working EVLA antennas at this band, as 
there are very few background sources to be seen in a modest integration. 

    Having a spare 2 hours to kill this afternoon, I repeated the 
experiment at L-band, where there is certainly no shortage of background 
sources! 

    I used 110 minutes on this endeavor, 10 of these on 3C48, once 10 
minutes, to establish amplitude and phase calibration.  The rest were on 
a randomly chosen field, at 0100+250.    I used spectral line mode, 2AC. 
    Antenna 14C was doing its 150-degree thing, so it was removed.  The 
usual amplitude drops abounded -- they were eliminated (on the 
calibrator) via EDITA (a marvellous AIPS task).  Antenna 21 was still 
AWOL.  Antenna 16 is being rewired.  The other 7 antennas worked well.  
On the VLA side, we  had 18 antennas working. 

    Images were made of the blank field, using (i) all data, (ii) EVLA 
only data, and (iii) VLA only data. 

Mode         Peak Flux            Total Cleaned Flux         rms
---------------------------------------------------------------------------
All                 56.5 mJy                    200 mJy               
0.25 mJy
EVLA           58.0                           117                       0.53
VLA             55.3                            184                      
0.36
--------------------------------------------------------------------------

    The results are just as expected.  The field is far from blank!  
There are dozens of background sources.  The brightest source (far from 
the center) is the same in all images.  The rms varies as expected.  The 
total cleaned flux is less in the EVLA image because the noise is more 
than twice as high -- and the sparse UV coverage makes source 
identification difficult for the deconvolution algorithm.  (Most of the 
sources have flux densities of a few mJy, so are hard to see in the EVLA 
only image). 
    There is no doubt, when viewing the three maps, that we are seeing 
the same field, in the same way, with the same flux density distribution.