A distribuição e cinemática do gás em Mrk 766 vistas em detalhes a partir de observações no infravermelho

Abstract

We have mapped emission-line flux distributions and ratios as well as the gaseous kinematics of the inner 450 pc radius of the Seyfert galaxy Mrk 766 using integral field near-IR J- and Kl-band spectra obtained with the Gemini North instrument NIFS at a spatial resolution of ≈60 pc and velocity resolution of ≈40 kms−1. Emission-line flux distributions in Pa β and Brγ extend to ≈300 pc from the nucleus in all directions, while the [Fe II] emission is extended to a similar distance but mostly along PA≈130◦. The coronal lines traced by [S IX] are resolved, presenting emission up to ≈150 pc from the nucleus. The molecular H2 gas emission is extended also to ≈300 pc from the nucleus but along PA≈50º, approximately perpendicularly to the orientation of the [Fe II] emission. The H2 gas has an excitation temperature Texc = 2360±45K and its emission is dominated by thermal processes, mainly due X-ray heating by the active nucleus. The [Fe II] emission seems also to be produced by these thermal processes, but with an important contribution from shocks, as evidenced by the correlation between enhanced [Fe II]/[P II] line ratios, the [Fe II] velocity dispersion and the radio structure. The gas velocity field is dominated by rotation, and the fit of a circular model gives a position angle of 59º for the line of nodes, which is the approximate orientation of the extended H2 emission. This fact, combined with the low H2 velocity dispersion close to the velocity resolution of the data supports a location of the H2 emitting gas in the galaxy plane, and its association with the feeding of the supermassive black hole. There is about 103 M⊙ of hot H2, implying ≈109 M⊙ of cold molecular gas in the inner 450 pc radius. On the other hand, the higher velocity dispersion (150 kms−1) for [Fe II] to the southeast of the nucleus, and the presence of both blueshifts and redshifts in the channel maps at the corresponding locations, supports the presence of an outflow to the southwest with an axis lying close to the plane of the sky. The ionized gas outflow rate is estimated to be 2.18 M⊙ yr−1, and the power of the outflow 0.011 Lbol. The distinct flux distributions and kinematics of the H2 and [Fe II] emitting gas, with the first more restricted to the plane of the galaxy and in rotation and the second related with the radio jet and in outflow are common characteristics of 8 Seyfert galaxies (ESO428-G14, NGC4051, NGC7582, NGC4151, Mrk 1066, Mrk 1157, Mrk 79 and Mrk 766) we have studied so far using similar integral-field observations and 2 others (Circinus and NGC2110) using long-slit observations. These results support the conclusion that the H2 emission is tracer of the AGN feeding, while the [Fe II] is a tracer of its feedback.