Molecular line CO (2->1) observations of ultraluminous IRAS galaxies.

D. Rigopoulou, A. Lawrence, G. J. White, M. Rowan-Robinson, S. E. Church

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CO (J=2->1) observations of six ultraluminous IRAS galaxies are presented. Four of these galaxies have no previous CO J=2->1 data and two have no previous CO detections at all. Based on these observations, molecular hydrogen masses are estimated and range from 5x10^9^ to 1.8x10^10^Msun_. The present data follow the well established correlation that exists between the infrared luminosity L_IR_ and the molecular mass content. The high values of the L_IR_/M_H_2__ suggest either an increased star formation efficiency and / or an additional source of luminosity such as an active nucleus. The ratio R=(J=2->1)/(J=1->0) between the J=2->1 and 1->0 line temperatures, is examined next using our J=2->1 intensities and other published CO J=1->0 data. For Arp 220, Mrk 231, Mrk 273 R lies in the range 0.7 to 1.1; for IRAS 05189 the CO intensity and the ratio R were both found to have extremely low values. The low values of R
Original languageEnglish
Pages (from-to)747
JournalAstronomy and Astrophysics
Publication statusPublished - 1 Jan 1996



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