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| Paper: |
Search for diffuse extended mid-IR emission in Luminous IR Galaxies |
| Volume: |
290, Active Galactic Nuclei: from Central Engine to Host Galaxy |
| Page: |
485 |
| Authors: |
Charmandaris, V.; Le Floc'h, E.; Mirabel, F. I. |
| Abstract: |
The discovery by IRAS of luminous (L(IR) > 1011 L(sun)) and ultraluminous (L(IR) > 1012 L(sun)) IR galaxies (LIRGs / ULIRGs) opened a new window in extragalactic astronomy, since it revealed that they are the dominant population of extragalactic objects in the local Universe (z < 0.3). It is now widely accepted that i) nearly all ULIRGs are advanced mergers harboring powerful nuclear starbursts and/or enshrouded AGN, and ii) the mid-IR is powerful tracer of the star formation activity and bolometric luminosity of galaxies. The poor spatial resolution of IRAS though, due to the large (∼1arcmin) pixels used, made it impossible to resolve the physical extent of the region which produces the bulk of their mid-IR emission. Recently, ground based 10 and 18micron imaging for a number of the nearest and brightest objects, has revealed compact nuclear emission from regions of just few arcsecs in diameter, (i.e. Soifer et al. 2001)., even though the ground measurements are hampered in sensitivity by the low mid-IR atmospheric transmission. Using ISOCAM, the most sensitive provides we searched for extended emission from a sample of nearby luminous IR galaxies (Arp220, Arp299, NGC6240, VV114, IRAS14248-1447, IRAS19254-7245, IRAS23128-5919) for which the 5-16micron spectral energy distribution was available. We find that with the exception of VV114 more than 90% of the integrated IRAS 12 micron flux originates from their nuclear regions (∼5arcsec, < 2kpc). This result suggests that the 10-15micron properties of distant unresolved ULIRGs would likely to also be dominated not by their disks, but by their nuclear region instead. |
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