Argus+

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The Argus+ Project at the GBT

The Argus receiver highlighting the amplifier modules at top and the 4 x 4-pixel card array.

The GBT is now into its second winter season with Argus, the 16-pixel camera for spectroscopy in the molecule-rich 3mm atmospheric window between 74 – 116 GHz. Argus is the brainchild of Sarah Church of Stanford University and collaborators, who received an NSF ATI grant to design a modular receiver system for the GBT that could be replicated and expanded in a straightforward way. With the unique combination of angular resolution (6.5 – 9 arcseconds), sensitivity, and field of view of the GBT, Argus is being used for ground-breaking surveys of dense gas in galaxies and nearby star-forming regions. Recent Argus results were highlighted at the American Astronomical Society 2018 Winter Meeting in Washington D.C.

The link to the Argus+ Astro-2020 white paper is here.

Left: Filament in DR21 mapped in 13CO. This map took 40 minutes in only moderate weather (τ=0.4). The footprint of the Argus array is shown upper right. Right: part of OMC-1 mapped by Argus in HNC(1-0). This map took 4.5 hours, including pointing, surface setting and calibration. The white circle shows the Argus beam (figure courtesy of Alvaro Hacar)

The Green Bank Observatory and the original Argus team are now collaborating on an Argus+ project, which would take advantage of the technical development afforded by Argus to produce a camera with ten times the mapping speed and includes a new spectrometer. Argus+ has the capability to routinely produce spectral line maps of key species such as CO, N2H+, HCN, and HCO+ with a spatial dynamic range (map area / pixel size) of 104 to 105.

The project leverages the NSF’s investment in the prototype Argus to produce a uniquely powerful scientific instrument accessible to the U.S. scientific community.

Below is a quick comparison of the original Argus and Argus+.

PropertyArgusArgus+Notes
Pixels16144Single Pol
IF Bandwidth1.5 GHz7 GHz 
Spectrometer

16 pix x 2 win x 23.4 MHz x 4096 ch
16 pix x 1250 MHz x 1024 ch

144 pix x 600 MHz x 131k ch
16 pix x 1250 MHz x 1024 ch

 
Receiver Tsys

40 – 80K

30 – 60K

 
Usable 3mm hours/year

~500

>1,000

TLS metrology
Frequency Range

74 – 116 GHz

74 – 116 GHz

 
Map time 6’x6′
dv=0.1 km/sec,
σTb=0.1 K

 53 hours

 5 hours

Includes overhead