HLS091828

Brief analysis of the faint source HLS091828 (z=5.243)

Coordinates:

• R.A. = 09h18m28.6s
• Dec. = 51d42'23.3"

Expected luxes (Combes et al. 2012):

• F1.3sma= 55+-7mJy
• F0.88mm= 125+-8mJy
• F2mm= 15+-7mJy

NIKA obsevations:

• Day: 13/06/2013

• Scans: 9 Lissajous of 5 min (<=> 45 min) each with followed by tracks (for tuning), 180 to 197

• Size of the map:90"x90"

• Opacity at 225 GHz: 0.7-0.8

• Elevation of the source: ~50 deg

• We detect the source at both wavelenghts, shown on the maps given bellow. The standard deviation of the Jack-Knife map gives the noise level:
• ~8 mJy/Beam at 1mm
• ~1 mJy/Beam at 2mm

  1mm_map.pdf	2mm_map.pdf

Profiles:

• The profiles are computed by averaging the map in concentric annuli, and we check that the measured flux is, a priori, consistent with what we expect at 2mm but too high at 1mm.

  1mm_profile.pdf	2mm_profile.pdf

Time per pixel:

• The time per pixel maps are also shown. It is equivalent to the number of hit map, divided by the sampling frequency. The pixels are 2"x2" here.

  1mm_time.pdf	2mm_time.pdf

Noise estimates:

• By multiplying the Jack-Knife maps with the squarre root of the time per pixel maps and computing the histogram of the obtained map, we are able to estimate the noise level in the data. Note that this is in the case of high opacity (we can expect the noise to be reduced by a factor of about exp(-tau/sin(elevation)) ~ 2, and even more since the resonances are larger under large optical load), and at 1mm it might even be reduced again by a factor of ~2 since we are apparently over calibrated.
• If this is correct, the noise is:

• ~50 mJy/Beam.sqrt(s) at 1mm

• ~15 mJy/Beam.sqrt(s) at 2mm

  1mm_noise.pdf	2mm_noise.pdf

• We can estimate the noise on the Jack-Knife maps dirrectly. With the brut map (2"x2" pixels, not filtered), we obtain at the at center of the map:
• 42 mJy/Beam at 1mm
• 6 mJy/Beam at 2mm
• If we smooth the map with a gaussian filter with FWHMs equals the the respective beams, we get:
• 3.4 mJy/Beam at 1mm
• 0.3 mJy/Beam at 2mm
• Since the array is always on-source, the sensitivity might be estimated to be:
• 3.4 x sqrt(45 min) = 180 mJy/Beam.sqrt(s)
• 0.3 x sqrt(45 min) = 15.6 mJy/Beam.sqrt(s)