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Article

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

CIT Disciplines

1.3 PHYSICAL SCIENCES

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Astrophysics and Astronomy

Publication Details

Published in the journal Astronomy & Astrophysics in the section Extragalactic Astronomy.

Metcalfe, L. et al., A&A, 444., 777-790, 2005, reproduced with permission, © ESO

We would like to thank the referee, Dr. Vassilis Charmandaris, for detailed comments which greatly improved the paper. We gratefully thank Dr. Qi Feng Yin for providing us with his VLA radio maps for study and for the radio data reproduced in Fig. 8. We thank Dr. Avishay Gal-Yam for helpful comments ans suggestions. The ISOCAM data presented in this paper were analysed using CIA, a joint development by the ESA Astrophysics Division and the ISOCAM Consortium. The ISOCAM Consortium is led by the ISOCAM PI, C. Cesarsky. The ISOPHOT data presented in this paper was reduced using PIA, which is a joint development by the ESA Astrophysics Division and the ISOPHOT consortium. LIA is a joint development of the ISO-LWS Instrument Team at Rutherford Appleton Laboratories and the Infrared Processing and Analysis Center (IPAC). The research of M. Burgdorf was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and sponsored by the National Aeronautics and Space Administration. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

Abstract

Markarian (Mkn) 297 is a complex system comprised of two interacting galaxies that has been modelled with a variety of scenarios. Observations of this system were made with the Infrared Space Observatory (ISO) using the ISOCAM, ISOPHOT and LWS instruments. ISOCAM maps at 6.7 µm, 7.7 µm, 12 µm and 14.3 µm are presented which, together with PHT-S spectrometry of the central interacting region, probe the dust obscured star formation and the properties of the organic dust. The ISOCAM observations reveal that the strongest emission in the four bands is at a location completely unremarkable at visible and near-IR (e.g. 2MASS) wavelengths, and does not coincide with the nuclear region of either colliding galaxy. This striking characteristic has also been observed in the overlap region of the colliding galaxies in the Antennae (NGC 4038/4039), the intragroup region of Stephan’s Quintet, and in IC 694 in the interacting system Arp 299, and again underlines the importance of infrared observations in understanding star formation in colliding/merging systems. At 15 µm, the hidden source in Mkn 297 is, respectively, 14.6 and 3.8 times more luminous than the hidden sources in the Antennae (NGC 4038/4039) and Stephan’s Quintet. Numerical simulations of the Mkn 297 system indicate that a co-planar radial penetration between two disk galaxies yielded the observed wing formation in the system about 1.5 × 108 years after the collision. A complex emission pattern with knots and ridges of emission was detected with ISOCAM. The 7.7 µm map predominantly shows the galaxy in emission from the 7.7 µm feature attributed to PAHs (Polycyclic Aromatic Hydrocarbons). The 14.3/7.7 µm ratio is greater than unity over most of the galaxy, implying widespread strong star formation. Strong emission features were detected in the ISOPHOT spectrum, while [O I], [O III] and [C II] emission lines were seen with LWS. Using data from the three instruments, luminosities and masses for two dust components were determined. The total infrared luminosity is approximately 1011 L, which (marginally) classifies the system as a luminous infrared galaxy (LIRG). A supernova that exploded in 1979 (SN 1982aa) gave rise to one of the most powerful known radio remnants which falls close to the strongest mid-infrared source and is identified with star forming region 14 in the optical. This supernova explosion may have been accompanied by a gamma-ray burst (GRB), consistent with the idea that GRBs are associated with supernovae in star forming regions, and a search for a GRB consistent with the direction to Mkn 297, in satellite data from July to December 1979, is recommended.

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