NICS--TNG infrared spectroscopy of NGC1068: the first extragalactic measurement of PII and a new tool to constrain the origin of FeII line emission in galaxies.

by

E. Oliva, A. Marconi, R. Maiolino, L. Testi, et al.

Abstract:

We report 0.9-1.4um spectroscopic observations of NGC1068 collected during the commissioning phase of the near infrared camera spectrometer (NICS) of the Telescopio Nazionale Galileo (TNG). These yielded the first extragalactic measurement of PII (1.188um) line emission. In the central 0.75"x2" the FeII/PII line-intensity ratio is close to unity, similar to that measured in the Orion bar and a factor of <20 smaller than in supernova remnants. This indicates that most of iron is locked into grains and, therefore, argues against shock excitation being the primary origin of FeII line emission in the central regions of NGC1068. We propose the FeII/PII ratio as a simple and effective tool to study and perhaps resolve the long debated questions related to the origin of FeII line emission and, more generally, to constrain the role of shock excitation in active galaxies.


Mantained by: Leonardo Testi