Robert F. Minchin

Kinematic clues to the origins of starless HI clouds : dark galaxies or tidal debris?

Isolated Hu2009i clouds with no optical counterparts are often taken as evidence for galaxy–galaxy interactions, though an alternative hypothesis is that these are primordial ‘dark galaxies’ that have not formed stars. Similarly, certain kinematic features in Hu2009i streams are also controversial, sometimes taken as evidence of dark galaxies but also perhaps explicable as the result of harassment. We numerically model the passage of a galaxy through the gravitational field of cluster. The galaxy consists of smoothed particle hydrodynamics particles for the gas and N-bodies for the stars and dark matter, while the cluster includes the gravitational effects of substructure using 400 subhaloes (the effects of the intracluster medium are ignored). We find that harassment can indeed produce long Hu2009i streams and these streams can include kinematic features resembling dark galaxy candidates such as VIRGOHI21. We also show that apparent clouds with diameter 100 km s−1 is negligible – making this a very unlikely explanation for the observed clouds in the Virgo cluster with these properties.

The Arecibo galaxy environment survey - a sensitive survey for neutral hydrogen in the local Universe

R. F. Minchin∗a, R. Auldb, L. Corteseb, J. I. Daviesb, E. Momjianc, R. Taylorb, B. Catinellad, P. A. Henninge, S. Linder f , E. Mullerg, K. L. O’Neilh, J. Rosenbergi, S. Sabatini j, S. E. Schneiderk, M. D. Stagek, W. van Driell a Arecibo Observatory b Cardiff University c NRAO Socorro d MPIfA Garching e University of New Mexico f University of Hamburg g ATNF h NRAO Green Bank i George Mason University j Osservatorio Astronomico di Roma k University of Massachusetts l Observatoire de Paris

Arecibo discovery of the pre-biotic molecule methanimine in Arp220 and new cm-wavelength transitions of other molecules

An on-going Arecibo line search between 1.1 and 10 GHz of the prototypical starburst/megamaser galaxy, Arp 220, has revealed a spectrum rich in molecular transitions. These include the prebiotic molecules: methanimine (CH2NH) in emission, three v2 = 1 direct l-type absorption lines of HCN, and an absorption feature from either 18OH or formic acid (HCOOH). In addition, we report three transitions of λ4-cm excited OH not previously detected in Arp 220 which are seen in absorption, and a possible absorption feature from the 6.668 GHz line of methanol. Our results mark the first distant extragalactic detection of methanimine, a molecule with high relevance to the origins of life. Further, the strong, previously undetected, cm-wave HCN v2 = 1 direct l-type lines can aid the study of dense molecular gas and active star-forming regions in this starburst galaxy.