Molecular Line Research

The molecular lines group at Arecibo Observatory consists of Chris Salter, Tapasi Ghosh and Robert Minchin. Former members (no longer at the Observatory), many of whom are still collaborating on projects, include Mayra Lebron, Barbara Catinella, Emmanuel Momjian and Mikael Lerner. The group has also welcomed a number of undergraduate students to work on summer projects and has formed collaborations with a number of Arecibo users and other astronomers away from the Observatory.

Starburst Galaaxies

The molecular line group at Arecibo Observatory started in 2006 with a proposal to carry out a spectral census of the star-burst galaxy Arp 220. Observations began in 2007, and quickly resulted in the discovery of methanimine (CH2NH) – the first detection of this pre-biotic molecule beyond the local volume. This discovery, along with previously unobserved cm-wavelength transitions of hydrogen cyanide (HCN), was publicly announced at the AAS meeting in Austin, TX, on January 11, 2007 and was subsequently picked up by the media:

(All links working as of March 2014. A more comprehensive list of on-line coverage can be found here.)

These observations were followed up by observations of ‘Arp 220-like’ galaxies. Two of these, IC 860 and Zw 049.057, were also found to contain methanimine and the cm-wavelength transitions of hydrogen cyanide, leading to these galaxies being targetted for further observations. However, the most interesting discovery came from the observations of the polar ring galaxy, NGC 660.

When the first observations of NGC 660 were made in December 2007, we didn't see anything. But by the time we looked again, a year later, lines from the hydroxyl radical (OH) were visible. We kept watching, and found that the OH lines grew in strength and that we were also seeing a rise in continuum emission. In 2012 we obtained high-resolution imaging of the nucleus of NGC 660 with the High Sensitivity Array (VLBA + GBT + Effelsberg + Arecibo). The discoveries were reported at the AAS meeting in Long Beach, CA, in January 7, 2013, with a press conference held on January 10, 2013. Slides from the press conference can be downloaded here and the press conference can be viewed on the AAS website (scroll down to AAS 221 and click on ‘Galaxies in the Extreme’; NGC 660 is from about 10:05 – 17:15):

(All links working as of March 2014.)

Recent activities include continued monitoring and a full spectral survey of NGC 660 and a deeper survey of Arp 200. Research on these projects has involved four undergraduate students so far.


The Arecibo Galactic Chemistry Survey is a collaboration led by Hector Arce. In addition to the members of the Arecibo molecular lines group, collaborators include Mayra Lebron, Esteban Araya and Chris de Vries. The project is making a high-resolution spectral census of the W51 star forming region using the Mock spectrometers with the novel pseudo-DPS observing mode. At present, data reduction and analysis is continuing on this project.