Argus144

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The Argus144 Project at the GBT

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

Green Bank Observatory is actively seeking members of the mm-astronomy community to join working groups in the areas of science, technology, software/data considerations and broader impacts, relevant to the instrument. If you are interested in joining one of these groups, or would simply like to be kept up-to-date with the development of the Argus-144 instrument, please fill out and submit the form here.

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 (PI), Kieran Cleary (Caltech), Andrew Harris (U. Maryland) and Joshua Gundersen (U. Miami), 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 Argus144 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 Argus144 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. Argus144 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 Argus144.

Property	Argus	Argus144	Notes
Pixels	16	144	Single Pol
IF Bandwidth	1.5 GHz	7 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	LASSI/metrology
Frequency Range	74 – 116 GHz	74 – 116 GHz
Map time 6’x6′ dv=0.1 km/sec, σT_b=0.1 K	53 hours	5 hours	Includes overhead

In September 2020, Green Bank Observatory hosted a virtual three-day workshop aimed at outlining the technical and scientific aspects of the proposed Argus144, video recordings of the presentations from that meeting, along with the schedule, list of speakers, etc are available here.