R. Riffel — Page 4 | Searcharxiv

arXiv2007

The first detection of near-infrared CN bands in active galactic nuclei: signature of star formation

We present the first detection of the near-infrared CN absorption band in the nuclear spectra of active galactic nuclei (AGN). This feature is a recent star formation tracer, being particularly strong in carbon stars. The equivalent width of the CN line correlates with that of the CO at 2.3 microns, as expected in stellar populations (SP) with ages between ~ 0.2 and ~ 2 Gyr. The presence of the 1.1 microns CN band in the spectra of the sources is taken as an unambiguous evidence of the presence of young/intermediate SP close to the central source of the AGN. Near-infrared bands can be powerful age indicators for star formation connected to AGN, the understanding of which is crucial in the context of galaxy formation and AGN feedback.

astro-ph↗

arXiv2006

A 0.8-2.4 microns spectral atlas of Active Galactic Nuclei

Aims: We present a near-infrared spectral atlas of 47 active galactic nuclei (AGN), of all degrees of activity, in the wavelength interval of 0.8-2.4 microns, including the fluxes of the observed emission lines. We analyze the spectroscopic properties of the continuum and emission line spectra of the sources Methods: In order to exclude aperture and seeing effects we use near-infrared spectroscopy in the short cross-dispersed mode (SXD, 0.8-2.4 microns), taking the JHK-bands spectra simultaneously. Results: We present the most extensive NIR spectral atlas of AGN to date. This atlas offers a suitable database for studying the continuum and line emission properties of these objects in a region full of interesting features. The shape of the continuum of QSOs and Seyfert 1's are similar, being essentially flat in H and K band, in the J band, a strong variation is found. In Seyfert 2 galaxies, the continuum in the F_lambda X lambda space smoothly decreases from 1.2 microns redwards in almost all sources. In J, it smoothly rises bluewards in some sources while in others a small decreased in flux is observed. The spectra are dominated by strong emission features of H I, He I, He II, [S III] and conspicuous forbidden lines of low and high ionization species. Molecular lines of H2 are common features to most objects. The absence of O I and Fe II lines in Seyfert 2 galaxies give observational support to the fact that these lines are formated in the outermost portion of the broad line region. [P II] and coronal lines are detected in all degrees of activity. The [Fe II] 12570A/16436A line ratio becomes a reliable reddening indicator for the narrow-line region of Seyfert galaxies.

astro-ph↗