Program: GS-2006B-Q-9

Recent {\it Spitzer} cosmological surveys have demonstrated that the majority of IR-selected galaxies at $z<1$ are in the LIRG class ($L_{\rm IR}=L[8-1000\mu {\rm m}] = 10^{11}-10^{12} L_\odot$) and that LIRGs make a significant contribution to the IR galaxy population at $1<z<2$. We propose to obtain T-ReCS Si2 ($8.7\,\mu$m) narrow-band imaging of a sample of six low-$z$ LIRGs. These galaxies are part of a complete volume ($v<5200\,$km s$^{-1}$) limited sample of LIRGs for which we have obtained {\it HST}/NICMOS images to identify star clusters and H\,{\sc ii} regions. The sample covers different morphologies and a range of IR luminosities. The combination of high spatial resolution ($\simeq 0.3\arcsec$) mid-IR imaging and spectroscopy (the latter to be proposed in the coming semesters) uniquely afforded by 8\,m class telescopes, and NICMOS observations will allow us to peer for the first time into the dust-enshrouded nuclear regions of LIRGs with the appropriate spatial resolution ($50-135\,$pc). Our goals are: (1) to identify heavily obscured AGN, not detected in the optical and near-IR, (2) to calibrate the mid-IR emission as a tracer of the star formation rate, (3) to investigate the nature of the dominant energy source (AGN vs stellar emission), and (4) to produce local templates to be compared with the high-redshift bright-IR sources currently being detected by {\it Spitzer}.