We report 0.9-1.4 mu m spectroscopic observations of NGC 1068 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 [P II] (1.188 mu m) line emission. In the central 0.75arcsecx2 arcsec the [Fe II]/[P II] line-intensity ratio is close to unity, similar to that measured in the Orion bar and a factor of la 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 [Fe II] line emission in the central regions of NGC 1068. We propose the [Fe II]/[P II] ratio as a simple and effective tool to study and perhaps resolve the long debated questions related to the origin of [Fe II] line emission and, more generally, to constrain the role of shock excitation in active galaxies.
Oliva E, Marconi A, Maiolino R, Testi L, Mannucci F, Ghinassi F, et al. (2001). NICS-TNG infrared spectroscopy of NGC 1068: The first extragalactic measurement of [P II] and a new tool to constrain the origin of [Fe II] line emission in galaxies. ASTRONOMY & ASTROPHYSICS, 369, 5-8.
NICS-TNG infrared spectroscopy of NGC 1068: The first extragalactic measurement of [P II] and a new tool to constrain the origin of [Fe II] line emission in galaxies
Testi L;
2001
Abstract
We report 0.9-1.4 mu m spectroscopic observations of NGC 1068 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 [P II] (1.188 mu m) line emission. In the central 0.75arcsecx2 arcsec the [Fe II]/[P II] line-intensity ratio is close to unity, similar to that measured in the Orion bar and a factor of la 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 [Fe II] line emission in the central regions of NGC 1068. We propose the [Fe II]/[P II] ratio as a simple and effective tool to study and perhaps resolve the long debated questions related to the origin of [Fe II] line emission and, more generally, to constrain the role of shock excitation in active galaxies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
