Gemini observations of disks and jets in young stellar objects and in active galaxies

We present first results from the Near-infrared Integral Field Spectrograph (NIFS) located at Gemini North. For the active galaxies Cygnus A and Perseus A we observe rotationally-supported accretion disks and adduce the existence of massive central black holes and estimate their masses. In Cygnus A we also see remarkable high-excitation ionization cones dominated by photoionization from the central engine. In the T-Tauri stars HV Tau C and DG Tau we see highly-collimated bipolar outflows in the [Fe II] λ 1.644 micron line, surrounded by a slower molecular bipolar outflow seen in the H₂ lines, in accordance with the model advocated by Pyo, T.-S., et al., Astrophys. J. 570, 724 (2002).     

The CaT strength in Seyfert nuclei revisited: analysing young stars and non-stellar light contributions to the spectra

In a former paper, we have presented spectra of 64 active, nine normal and five starburst galaxies in the region around the near-infrared calcium triplet (CaT) absorption lines and the [S  iii ]λ9069 line. In the present paper, we analyse the CaT strength ( W _CaT) and kinematical products derived in that study, namely stellar  (σ_★)  and ionized gas (σ_gas) velocity dispersions. Our main results may be summarized as follows. (1) Type 2 Seyfert galaxies show no sign of dilution in W _CaT with respect to the values spanned by normal galaxies, even when optical absorption lines such as the Ca  ii K band at 3933 Å are much weaker than in old, bulge-like stellar populations. (2) The location of type 2 Seyfert galaxies in the   W _CaT– W _CaK  plane is consistent with evolutionary synthesis models. The implication is that the source responsible for the dilution of optical lines in these active galactic nuclei (AGN) is a young stellar population, rather than an AGN featureless continuum, confirming the conclusion of the pioneer study of Terlevich, Díaz & Terlevich. (3) In type 1 Seyfert galaxies, both   W _{[S  iii ]}  and W _CaT tend to be diluted due to the presence of a non-stellar component, in agreement with the unification paradigm. (4) A comparison of  σ_★  with σ_gas (obtained from the core of the [S  iii ] emitting line) confirms the existence of a correlation between the typical velocities of stars and clouds of the narrow line region. The strength and scatter around this correlation are similar to those previously obtained from the [O  iii ]λ5007 linewidth.     

On the nature of the near-UV extended light in Seyfert galaxies

We study the nature of the extended near-UV emission in the inner kiloparsec of a sample of 15 Seyfert (Sy) galaxies which have both near-UV (F330W) and narrow-band [O  iii ] high-resolution Hubble images. For the majority of the objects, we find a very similar morphology in both bands. From the [O  iii ] images, we construct synthetic images of the nebular continuum plus the emission-line contribution expected through the F330W filter, which can be subtracted from the F330W images. We find that the emission of the ionized gas dominates the near-UV extended emission in half of the objects. A further broad-band photometric study, in the bands F330W ( U ), F547M ( V ) and F160W ( H ), shows that the remaining emission is dominated by the underlying galactic bulge contribution. We also find a blue component whose nature is not clear in four out of 15 objects. This component may be attributed to scattered light from the active galactic nuclei, to a young stellar population in unresolved star clusters, or to early disrupted clusters. Star-forming regions and/or bright off nuclear star clusters are observed in 4/15 galaxies of the sample.