New optical Hubble Space Telescope ( HST ) , Spitzer Space Telescope , GALEX , and Chandra observations of the single-nucleus , luminous infrared galaxy ( LIRG ) merger IC 883 are presented .
The galaxy is a member of the Great Observatories All-sky LIRG Survey ( GOALS ) , and is of particular interest for a detailed examination of a luminous late-stage merger due to the richness of the optically-visible star clusters and the extended nature of the nuclear X-ray , mid-IR , CO and radio emission .
In the HST ACS images , the galaxy is shown to contain 156 optically visible star clusters distributed throughout the nuclear regions and tidal tails of the merger , with a majority of visible clusters residing in an arc \sim 3–7 kpc from the position of the mid-infrared core of the galaxy .
The luminosity functions of the clusters have an \alpha _ { F 435 W } \sim - 2.17 \pm 0.22 and \alpha _ { F 814 W } \sim - 2.01 \pm 0.21 , compared with V-band derived values measured for the well-studied LIRG NGC 34 and the Antennae Galaxy of \alpha \sim - 1.7 \pm 0.1 and -2.13 \pm 0.07 , respectively .
Further , the colors and absolute magnitudes of the majority of the clusters are consistent with instantaneous burst population synthesis model ages in the range of a few \times 10 ^ { 7 } -10 ^ { 8 } yrs ( for 10 ^ { 5 } M _ { \odot } clusters ) , but may be as low as few \times 10 ^ { 6 } yrs with extinction factored in .
The X-ray and mid-IR spectroscopy are indicative of predominantly starburst-produced nuclear emission , and the star formation rate , estimated based on the assumption that the radio and far-infrared luminosities are tracing the starburst population , is \sim 80 M _ { \odot } yr ^ { -1 } .
The kinematics of the CO emission and the morphology of both the CO and radio emission are consistent with the nuclear starburst being situated in a highly inclined disk 2 kpc in diameter with an infrared surface brightness \mu _ { IR } \sim 2 \times 10 ^ { 11 } L _ { \odot } kpc ^ { -2 } , a factor of 10 less than that of the Orion star-forming region .
Finally , the detection of the [ Ne V ] 14.32 \mu m emission line is evidence that an AGN is present .
The faintness of the line ( i.e. , [ Ne V ] / [ Ne II ] 12.8 \mu m \sim 0.01 ) and the small equivalent width of the 6.2 \mu m PAH feature ( = 0.39 \mu m ) are both indicative of a relatively weak AGN .