Astronomy Department

Instrument

We are currently applying a radical upgrade to the AzTEC website ... a reasonable version of this page will appear shortly (on cosmological time scales at least) Instrument Parameters In the 1.1mm wavelength configuration Band center frequency (assuming flat spectrum): 270.5 GHz Effective bandwidth: 49.0 GHz Effective throughput (etendu*efficiency at JMCT): 0.2 mm^2 sr Beam Sizes (FWHM):

JCMT: 18 arcseconds
ASTE: 28 arcseconds
LMT: 5 arcseconds

Below is a histogram of raw detector sensitivities for our JCMT run for three different values of effective atmospheric opacity, tau at 225 GHz = 0.11 (thick line), 0.16 (medium line), and 0.21 (light line).

sensplot

Mapping Speed

An approximation for AzTEC's mapping speed at 1.1mm at the JCMT for a viariety of raster-mapped targets is shown below. These mapping speeds are empirical, and so are a very good estimate of what one should expect for sparse point source searches when not including observing overheads (pointing, calibration, focus observations, load curves, etc.) and when not including inefficiencies due to the observing strategy.

Note also that mapping speeds given here are based on a very aggressive cleaning of the atmosphere from the data. Thus, while these mapping speeds are accurate for point-source searches (such as submillimeter galaxy surveys), they are an overestimate for mapping extended sources such as the dust around nearby galaxies or mapping of the Sunyaev-Zel'dovich effect in clusters. As we gain experience reducing data based on those types of projects, we will post additional results here.

mapping_speed

As is seen in the plot below, the mapping speed is tightly correlated to the effective opacity of the observation. The best fit quadratic fit is shown in the plot.

Bandpass

The spectral response of AzTEC is set by a sequence of low-pass filters and some waveguide high-pass filtering. Thus far we have only operated AzTEC in its 1.1mm wavelength configuration, however, in the future we expect to configure the instrument to do SZE studies at 2mm wavelength.

Below is the AzTEC system bandpass (peak normalized) for the JCMT05B run. In the linked data file, the negative values just below the bandpass have been artificially trimmed to 0. These values arise from a problem with the phase in our FTS measurement.

bandpass

data file for the bandpass

1) Cold Electronics

2) Readout Electronics

3) Cryogenics

4) Bolometers