NOAO >   Observing Info >   Approved Programs >   2009A-0064

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Proposal Information for 2009A-0064


PI: Christopher Packham, University of Florida, packham@astro.ufl.edu
Address: Department of Astronomy, PO Box 112055, 211 Bryant Space Science Center, Gainesville, FL, 32611-2055, USA

CoI: Tanio Diaz-Santos, Instituto de Estructura de la Materia, CSIC
CoI: Almudena Alonso-Herrero, Instituto de Estructura de la Materia, CSIC
CoI: Luis Colina, Instituto de Estructura de la Materia, CSIC
CoI: Jose M. Rodriguez Espinosa, Instituto de Astrofisica de Canarias, CSIC
CoI: Rachel Mason, Gemini Observatory - North
CoI: James Radomski, Gemini Observatory - South

Title: High spatial resolution mid-infrared observations of LIRGs

Abstract: Luminous Infrared Galaxies (L_IR=L[8-1000 um]=10^11-10^12L_sun) host in their central regions some of the most energetic phenomena: AGN and/or intense star formation. As part of our successful on-going T-ReCS project, we have found that the integrated central (a few kpc) emission of LIRGs shows elevated 8micron to Pa-alpha (i.e., number of ionizing photons) ratios with respect to those of individual HII regions (scales of 200-500 pc). This suggest that the 8micron emission is not only related to the ionizing stellar population but also with more diffuse regions which would account for this difference. We have corroborated this fact for the LIRG NGC5135 where our high-spatial resolution T-ReCS spectroscopy reveals changes in the mid-IR spectral features of the Seyfert nucleus, HII regions, and diffuse emission on scales of only 1-2" (200-500 pc). We have also obtained T-ReCS spectroscopy of the very center ( 80 pc) of the southern nucleus of the LIRG NGC3256 and seen that it is highly extinguished, which is not seen in the Spitzer spectrum. Thus, to gain more insight into the detailed processes responsible for the mid-IR emission of LIRGs at the smallest scales (a few hundred parsecs), we propose to obtain additional T-ReCS N-band low-resolution spectroscopy for three new low-z LIRGs to complete the observations of the sample for this semester. We would like to emphasize that high-spatial resolution ( 0.3'') T-ReCS mid-IR observations uniquely afforded by 8-m class telescopes (which we stress, cannot be achieved by Spitzer telescope due to its limited spatial resolution), is crucial for this kind of study.


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