Digging process in NGC 6951: the molecular disc bumped by the jet

Abstract

We present a study of the central 200 pc of the galaxy NGC 6951, SAB(rs)bc, an active twin of the Milky Way, at a distance of 24 Mpc. Its nucleus has been observed in the optical with the GMOS-IFU, showing an outflow, and with the HST/ACS, revealing two extended structures with similar orientation, suggesting the presence of a collimating and/or obscuring structure. In order to ascertain this hypothesis, adaptive optics assisted NIR integral field spectroscopic observations were obtained with the NIFS spectrograph in the Gemini North telescope. We detected a compact structure of H 2 molecular gas, interpreted as a nearly edgeon disc with diameter of ∼47 pc, PA=124°and velocity range from-40 to +40 km s −1. This disc is misaligned by 32°with respect to the radio jet and the ionization cones seen in the optical. There are two regions of turbulent gas, with position angles similar to the jet/cones, seen both in molecular and ionized phases; these regions are connected to the edges of the molecular disc and coincide with a high ratio of [N II]/Hα=5, suggesting that these regions are shock excited, partially ionized or both. We explain these structures as a consequence of a "digging process" that the jet inflicts on the disc, ejecting the molecular gas towards the ionization cones. The dynamical mass within 17 pc is estimated as 6.3 × 10 6 M. This is an interesting case of an object presenting evidence of a connected feeding-feedback structure.

A two-stage outflow in NGC 1068

“…The secondary wind is responsible for redirecting and spreading the collimated energetics of the jet, and this process could take place always when a dense molecular cloud is impacted by a jet without being completely wiped out. Even if the jet is not deflected, the ejected material may follow a different orientation from that of the jet, which may be the case in NGC 6951 (May et al 2016). This combination of effects likely accounts for the high velocities reached by the blobs into the cone for distances up to ∼150 pc from the nucleus.…”

“…The starting point is the evaluation of the molecular mass contained in the emitting southwest wall of the bubble, which is not disrupted. Assuming thermal equilibrium during the expansion, according to the calculations performed in Scoville et al (1982); Riffel et al (2008); May et al (2016):…”

“…After the reduction, we performed a data treatment procedure described in more detail in Menezes et al (2014Menezes et al ( , 2015 and May et al (2016). The Differential Atmospheric Refraction (DAR), although known to have a small effect on the NIR, can displace the data cube centroids by up to 0.2 arcsec.…”

The nuclear architecture of NGC 4151: on the path toward a universal outflow mechanism in light of NGC 1068

“…Curiously, the results found for the galaxy NGC 6951 in May et al (2016) (where a jet interacts with a nuclear molecular thick disc), may indicate a good connection between molecular outflows for small and larger scales. There, the interaction is more dramatic because it involves a misaligned jet/accretion disc with respect to a thick molecular disc surrounding the nucleus (r∼24 pc).…”

“…Once a PSF has been choose, the last step is the application of the Richardson-Lucy PSF deconvolution method (Richardson 1972;Lucy 1974). For the H-band, we could not find a reliable PSF from the data, then we have opted to use a PSF extracted from the standard star, similar to what was performed in May et al (2016). The PSF profiles are shown in Fig.…”