{\bf CO In A Dynamically Spectacular Ringlike Luminous IR Merger}
Session 77 -- Starbursts
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [77.05] {\bf CO In A Dynamically Spectacular Ringlike Luminous IR Merger}

Yu Gao, P.M. Solomon (SUNY, Stony Brook), S.J.E. Radford, D. Downes (Institut de Radio Astronomie Millim\'etrique, France)

NGC 1144, the eastern component of an interacting galaxy system Arp 118 which has an elliptical companion --- NGC 1143, has a distorted disk and an extended ringlike structure of HII regions. Using the IRAM 30-m telescope, we have detected extremely strong and wide CO emission line (FWZI $\sim 1100 \ km s^{-1}$) from the nuclei of NGC 1144 which itself is an interacting, infrared-luminous, ring-like Seyfert II. The extended ring structure, $\sim 10 \ kpc$ from the nuclei also shows very strong CO emission. The total molecular mass is $M_{H_2} \sim 4 \times 10^{10} \ M_{\odot}$, exceeds that of Arp 220 and is one of the highest in the local universe. About $1 \times 10^{10}$ ms molecular gas is contained in the ring'' $\sim 10 \ kpc$ from the nuclear region. Although the galaxy has a huge molecular mass, the OB star formation efficiency, indicated by the ratio of $L_{IR}/M_{H_2}$ $\sim 5$ , is comparable to the Milky Way and is one of the lowest observed for any interacting IR-luminous galaxy.

Arp 118 (in particular NGC 1144) is one of the most fascinating merging systems yet observed. It clearly has huge quantities of molecular gas and may be a merger at an early stage with a strong Extranuclear starburst, but a very low massive star formation efficiency. Our future interferometry of the CO(1-0) line will provide the best opportunity to study the distribution and kinematics of the molecular gas in this spectacular merging/interacting galaxy system.