MUSTANG-2 Mapping Information

MUSTANG-2 Mapping Information#

MUSTANG-2’s primary scanning method is that of a Lissajous Daisy of varying radii. The mapping speed profiles have been scaled to a zenith opacity of 0.1 and elevation of 45 degrees.

../../../_images/AverageMappingSpeedsTogether_April2021.png

This sensitivity assumes an effective smoothing of 10.0” FWHM. If heavier smoothing is acceptable the sensitivity is better by a factor of (FWHM/10.0 arcsec).

Historically, we have reported mapping speeds based on the RMS within a circle of radius 2 arcminutes. These values have now been extended to a range of scan sizes seen below.

Mapping speeds and corresponding sensitivities#

We define mapping speed (ms) as \(\sigma \times \sqrt{t}\). Historically, we have reported mapping speeds based on the RMS within a circle of radius 2’. These values have now been extended to a range of scan sizes. Listed below are the mapping speeds within the central 2’ in various units. Each mapping speed can be thought of as the corresponding sensitivity/RMS reached within one hour of observation which gives that \(\mathrm{ms}=\sigma \times \sqrt{1}\) so the mapping speeds below can be thought of the sensitivity/RMS reached within one hour for a given daisy radius.

Scan size (radius, arcminutes)

Mapping speed \(( \mu \mathrm{K~hr}^{1/2})\)

Mapping speed \(( \mu \mathrm{Jy/beam~hr}^{1/2})\)

Mapping speed \((\mathrm{Compton-y~hr}^{1/2})\)

2.5

73

56.2

2.0E-5

3.0

74

57

2.0E-5

3.5

77

59.3

2.1E-5

4.0

85

65.5

2.3E-5

4.5

98

75.5

2.7E-5

5.0

117

90.1

3.2E-5
Notes on the above table:

  • The mapping speeds above are calculated based on the RMS in the central 2 arcminutes. For small scans, this region has roughly uniform noise.

  • The conversion from \(\mu \mathrm{K}\) to \(\mu \mathrm{Jy/beam}\) is roughly 0.77; i.e. multiply the \(\mu \mathrm{K}\) noise by 0.77 to get a noise estimate in \(\mu \mathrm{Jy/beam}\).

  • The conversion from \(\mu \mathrm{K}\) to Compton-y is roughly 2.74E-7; i.e. multiple the \(\mu \mathrm{K}\) noise by 2.74E-7 to get a noise estimate in Compton-y.

  • Extended signal on scales up to 5’ should be imaged with reasonable fidelity, but faint signal more extended than this may be difficult to detect. Bright emission (20 mJy/beam or more) can be reconstructed over scales of many arcminutes. The angular resolution of MUSTANG on the GBT is typcally 9” (FWHM) and the instantaneous field of view is a 4’ diameter circle. Recovery of signal depends on data processing.

Mapping Memo#

Here is a MUSTANG-2 mapping speeds memo.