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:

• Science Daily
• Phys.org
• National Geographic
• NASA's Astrobiology Magazine
• Financial Express (India)

(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):

• Yahoo! News
• Discovery News
• Huffington Post
• Science Daily
• Phys.org
• Space.com

(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.

AGCS

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.

Papers

• Molecular Lines in NGC 660 Arias de Saavedra Benitez et al., 2014, AAS Meeting 223, #454.12
• A Deep Arecibo Spectral Scan of Arp 220 Vick et al., 2014, AAS Meeting 223, #242.06
• The Interstellar Media of the Luminous Infra-Red Galaxies, IC 860 and Zw 049.057 Nieves et al. 2013, AAS Meeting 221, #349.25
• Arecibo Spectral Line Scan of the Hot Molecular Core in W51: Results from the C-Band High Frequency Range Araya et al. 2013, AAS Meeting 221, #216.07
• A Radio Continuum and Spectral Line Outburst in the Nearby Galaxy NGC 660 Minchin et al. 2013, AAS Meeting 221, #157.06
• Radio Recombination Lines Toward W51A Rivera et al. 2011, AAS Meeting 217, #434.33
• MERLIN Imaging Of Methanimine Molecule (CH₂NH) In Arp 220 Qasim et al. 2010, AAS Meeting 215, #412.14/BAAS, 42, 248
• A cm-Wavelength Search for Pre-Biotic Molecules in Starburst Galaxies. Minchin et al. 2009, AAS Meeting 213, #445.02/BAAS, 41, 328
• The Arecibo ARP 220 Spectral Census. I. Discovery of the Pre-Biotic Molecule Methanimine and New Cm-Wavelength Transitions of Other Molecules Salter et al. 2008, AJ, 136, 389
• The Detection of Prebiotic Molecules in the ULIRG Arp 220 Ghosh et al. 2007, AAS Meeting 211, #141.07/BAAS, 39, 992 Poster (PDF)
• Excited-OH And Methanol Absorption In The ULIRG Arp220 Salter et al. 2007, AAS Meeting 211, #141.06/BAAS, 39, 992 Poster (PDF)
• Arecibo discovery of the pre-biotic molecule methanimine in Arp220 and new cm-wavelength transitions of other molecules Momjian et al. 2007, Modern Radio Universe, Proc. Sci., 118 Poster (PDF)