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 µm, 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 used near-infrared spectroscopy in the short cross-dispersed mode (SXD, 0.8-2.4 µm), 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 Sy 1's are similar, being essentially flat in the H and K bands, while a strong variation is found in the J band. In Seyfert 2 galaxies, the continuum in the Fλ × λ space smoothly decreases in flux from 1.2 µm redwards in almost all sources. In J, it smoothly rises bluewards in some sources, while in others a small decrease in flux is observed. The spectra are dominated by strong emission

Abstract. Near-infrared spectroscopy is used to study the kinematics and excitation mechanisms of H 2 and [Fe ] lines in a sample of mostly Seyfert 1 galaxies. The spectral coverage allows simultaneous observation of the JHK bands, thus eliminating the aperture and seeing effects that have usually plagued previous works. The H 2 lines are unresolved in all objects in which they were detected while the [Fe ] lines have widths implying gas velocities of up to 650 km s −1 . This suggests that, very likely, the H 2 and [Fe ] emission does not originate from the same parcel of gas. Molecular H 2 lines were detected in 90% of the sample, including PG objects, indicating detectable amounts of molecular material even in objects with low levels of circumnuclear starburst activity. Analysis of the observations favors thermal excitation mechanisms for the H 2 lines. Indeed, in NGC 3227, Mrk 766, NGC 4051 and NGC 4151, the molecular emission is found to be purely thermal but with heating processes that vary between the objects. Thermal excitation is also confirmed by the rather similar vibrational and rotational temperatures in the objects for which data were available. [Fe ] lines are detected in all of the sample AGN. The [Fe ] 1.254 µm/Paβ ratio is compatible with excitation of the [Fe ] lines by the active nucleus in most Seyfert 1 galaxies, but in Mrk 766 the ratio implies a stellar origin. A correlation between H 2 /Brγ and [Fe ]/Paβ is found for our sample objects supplemented by data from the literature. The correlation of these line ratios is a useful diagnostic tool in the NIR to separate emitting line objects by their level of nuclear activity. X-ray excitation models are able to explain the observed H 2 and part of the [Fe ] emission but fail to explain the observations in Seyfert 2 galaxies. Most likely, a combination of X-ray heating, shocks driven by the radio jet and circumnuclear star formation contributes, in different proportions, to the H 2 and [Fe ] lines observed. In most of our sample objects, the [Fe ] 1.257 µm/1.644 µm ratio is found to be 30% lower than the intrinsic value based on current atomic data. This implies either that the extinction towards the [Fe ]-emitting clouds is very similar in most objects or there are possible inaccuracies in the A-values in the Fe  transitions.

We employ IRTF SpeX NIR (0.8µm-2.4µm) spectra to investigate the stellar population (SP), active galactic nuclei (AGN) featureless continuum (F C) and hot dust properties in 9 Sy 1 and 15 Sy 2 galaxies. Both the STARLIGHT code and the hot dust as an additional base element were used for the first time in this spectral range. We found evidence of correlation among the equivalent widths (W λ ) Si I 1.59µm × Mg I 1.58µm, equally for both kinds of activity. Part of the W Na I 2.21µm and W CO 2.3µm strengths may be related to galaxy inclination. Our synthesis shows significant differences between Sy 1 and Sy 2 galaxies: the hot dust component is required to fit the K-band spectra of ∼90% of the Sy 1 galaxies, and only of ∼25% of the Sy 2; about 50% of the Sy 2 galaxies require a F C component contribution 20%, while this fraction increases to about 60% in the Sy 1; also, in about 50% of the Sy2, the combined FC and young components contribute with more than 20%, while this occurs in 90% of the Sy1, suggesting recent star formation in the central region. The central few hundred parsecs of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1µm CN band can be used as a tracer of intermediate-age SPs. The simultaneous fitting of SP, F C and hot dust components increased in ∼ 150% the number of AGNs with hot dust detected and the mass estimated. The NIR emerges as an excellent window to study the stellar population of Sy 1 galaxies, as opposed to the usually heavily attenuated optical range. Our approach opens a new way to investigate and quantify the individual contribution of the three most important NIR continuum components observed in AGNs.

Near-infrared spectroscopy is used to study the kinematics and excitation mechanisms of H 2 and [Fe II] lines in a sample dominated by Seyfert 2 galaxies. The spectra simultaneously cover the JHK bands, allowing us to compare line fluxes emitted in the interval 0.8-2.4 µm and avoiding aperture and seeing effects. The H 2 lines are systematically narrower than the narrow-line region lines, suggesting that, very likely, the H 2 does not originate from the same parcel of gas that forms the narrow-line region. Emission-line ratios between H 2 lines favour thermal excitation mechanisms for the molecular gas in active galactic nuclei. It was found that non-thermal excitation contributes, at most, 30 per cent of the observed H 2 . Thermal excitation is also confirmed by the rather similar vibrational and rotational temperatures in the objects (∼2000 K). The mass of hot H 2 ranges from 10 2 to 10 3 M , with nearly half of objects showing values of <500 M . It shows that the fraction of molecular mass present in the nuclear region and emitting in the near-infrared is a very small fraction of the warm molecular mass present in the centre. A diagnostic diagram composed of the line ratios H 2 /Brγ and [Fe II]/Paβ proves to be a useful tool in the near-infrared for separating emission-line objects by their degree of nuclear activity. We found that active galactic nuclei are characterized by H 2 2.121 µm/Brγ and [Fe II] 1.257 µm/Paβ flux ratios between 0.6 and 2. Starburst/H II galaxies display line ratios <0.6 while low-ionization nuclear emission-line regions are characterized by values larger than 2 in either ratio.

All together indicate a stratification in the ionized gas, usually interpreted in terms of nuclear photoionization as the driving ionization mechanism. However, CL profiles show various peculiarities: they are broader by a factor of 2 than lower ionization lines, the broadening being in terms of asymmetric blue wings, and their centroid position at the nucleus is blueshifted by a few hundred km s À1 . Moreover, in NGC 1386 and NGC 1068, a doublepeaked [Fe vii] line is detected in the nuclear and extended coronal region, this being the first report of this type of profile in CLs in active galactic nuclei. If interpreted as outflow signatures, the total broadening of the lines at zerointensity levels implies gas velocities up to 2000 km s À1. Although the stratification of ions across the coronal region means that photoionization is the main power mechanism, the high velocities deduced from the profiles, the relatively large spatial extension of the emission, and the results from photoionization models indicate that an additional mechanism is at work. We suggest that shocks generated by the outflow could provide the additional required power for line formation.