Multi-Wavelength Goals Observations of Star Formation and Active Galactic Nucleus Activity in the Luminous Infrared Galaxy Ic 883

Abstract

New optical Hubble Space Telescope (HST), Spitzer Space Telescope, Galaxy Evolution Explorer, 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 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 Advanced Camera for Surveys 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 ∼3-7 kpc from the position of the mid-infrared core of the galaxy. The luminosity functions of the clusters have an α F435W ∼ −2.17 ± 0.22 and α F814W ∼ −2.01 ± 0.21, compared with V-band-derived values measured for the well-studied LIRG NGC 34 and the Antennae Galaxy of α ∼ −1.7 ± 0.1 and −2.13 ± 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 ×10 7 -10 8 yr (for 10 5 M clusters), but may be as low as few ×10 6 yr with extinction factored in. The X-ray and mid-IR spectroscopies 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 ∼80 M 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 μ IR ∼ 2 × 10 11 L kpc −2 , a factor of 10 less than that of the Orion star-forming region.

Investigation of Dual Active Nuclei, Outflows, Shock-Heated Gas, and Young Star Clusters in Markarian 266

“…Their overall properties indicate they are SCs and associations similar to those observed in other galaxies undergoing extensive bursts of star formation. The detection method followed the procedure described in detail by Modica et al (2012) for SCs in the late stage LIRG merger IC 883. First, masks outlining the galaxy were applied to the images.…”

“…Then Source Extractor (Bertin & Arnouts 1996) was used to fit and subtract the underlying galaxy and perform point-source detection in the B-and I-band images. The extracted objects were processed with IDL routines to perform photometry and apply selection criteria that accepted only reliable sources with an FWHM of 1.7-4 pixels, have S/N > 5, and are detected in both bands; details are given in Modica et al (2012). This procedure resulted in the detection of 120 point sources with 21 mag B 27 mag and 19.5 mag I 25.7 mag (uncorrected for extinction); their coordinates and photometric properties are listed in the Appendix (Table 15).…”

e-MERLIN and VLBI observations of the luminous infrared galaxy IC 883: a nuclear starburst and an AGN candidate revealed

“…This LIRG is probably the result of the merger of two disc galaxies (Smith et al 1995), as suggested by its associated tidal tails, a diffuse one approximately perpendicular to the region where gas and dust preferentially concentrate (i.e., the disc) as seen in optical and near-IR (NIR) studies (e.g., Smith et al 1995;Scoville et al 2000;Modica et al 2012), and a narrow one along the disc itself (Keel 1985).…”

“…However, Yuan et al (2010) reclassified this galaxy as a composite starburst-AGN, based on the revised optical diagnostic diagrams of Kewley et al (2006). The multi-wavelength study of IC 883 by Modica et al (2012) also provides evidence of its composite nature. It is consequently expected that an AGN contributes to A&A 543, A72 (2012) Notes.…”

AGN and Starbursts in Dusty Galaxy Mergers: Insights from the Great Observatories All-sky LIRG Survey

“…A multiwavelength study of the late-stage merger IC 883 (Modica et al 2012) revealed 156 star clusters located primarily in the circumnuclear region (3-7 kpc from the mid-IR core) and throughout the tidal tails. The clusters have a luminosity function similar to clusters in other star-forming galaxies, and the broadband colors are consistent with a starburst population synthesis model with ages of approximately 10 7 − 10 9 yr, or as young as a few Myr considering the (unknown) extinction.…”