News from the 30m

GISMO - The Goddard-IRAM Superconducting 2 Millimeter Observer tested at the IRAM 30m observatory

In October 2008, the GISMO team Johannes Staguhn, Stephen Maher, Elmer Sharp, Dale Fixsen, and Dominic Benford spent two weeks at the 30m observatory to first install their GISMO bolometer camera in the lab and then in the receiver cabin to test its performance on the sky. GISMO consists of $8\times16$ pixels with 2mm pitch transition edge sensors (TES). The super conducting TES are read out by time domain SQUID multiplexers built at the National Institute for Standards (NIST), in Boulder, Colorado. The nominal bandwidth of the camera is 125-175 GHz, pixels are spaced by $14\hbox{$^{\prime\prime}$}$, the telescope HPBW is $16\hbox{$^{\prime\prime}$}$ at 2mm. Data are taken while the telescope is performing Lissajous scan patterns, without switching the secondary, to increase the mapping efficiency. An automated pipeline merges the GISMO data with the telescope data streams to create FITS files, being triggered by the IRAM messaging system. Data are then further reduced using the Goddard data reduction package.

The 2mm spectral range provides a unique terrestrial window enabling ground-based observations of the earliest active dusty galaxies in the universe and thereby allowing to derive better constraints on the star formation rate in these objects. Preliminary results from this second observing run at the 30m telescope look very promising. More detailed information will be given in the next Newsletter. Figure 4 shows a quicklook result from Cygnus A observations.

Figure 4: Composite picture showing Cygnus A at 2mm (grey) and at 21cm.

Carsten KRAMER

MAMBO2 - Science highlights from November 2008

After a first visit earlier this year, MAMBO2 was recommissioned in early November by the Bonn bolometer group Ernst Kreysa, Giorgio Siringo, Walter Esch and IRAM staff, in preparation of two weeks of pooled observations. In the weeks before, it was notably Axel Weiss who contributed his expertise of the internals of the pool data base.

During recommissioning, mirrors M5 to M8 had to be realigned and the vibration damping of the optical table had to be optimized again for MAMBO2. Temperature readouts were installed, which now allow to continuously monitor the temperatures of the different stages. The heat pulse needed to recycle He-3 is now set automatically allowing for a well controlled and reproducible recycling. Various problems previously encountered with the ABBA2 backend-PC were addressed and most of them solved.

The following first week of pooled observations enjoyed good to excellent weather conditions reaching below 1mm of water vapor, and some exciting new results were obtained, despite some remaining problems with the hard- and software. During the second week, weather was less favourable. In total 14 MAMBO2 projects were finished, leaving only 3 unfinished. In addition, several of the heterodyne backup projects were observed in this period.

Among the science highlights of these two weeks are: the detection of a quasar at $z=6$, and the detections of four new disks around brown dwarfs. Another highlight is a new MAMBO2 map of the starless cloud L183, conducted by the PI, Laurent Pagani (Fig. 5). L183 is high above the galactic plane and close to us (110 pc). It hosts two prestellar cores inside an elongated ridge, and several secondary cores, some of them having a molecular counterpart (C$^{18}$O peak to the east, SO peak to the west, C$_3$H$_2$ peak to the north, etc...). The main prestellar core with an estimated column density of 1.5 $\times 10^{23}$ cm$^{-2}$ is devoid of most molecular species, and only the H$_2$D$^+$ peak is coincidental with it. It has also revealed itself as being one of the coldest prestellar cores known today with both gas and dust estimated at 7 K.

Figure 5: MAMBO2 1.2mm dust continuum map of the starless cloud L183 by Pagani et al

Carsten KRAMER