Detailed investigation of Seyfert galaxy NGC6104 and its environment.

Smirnova A.A., Moiseev A.V. & Afanasiev V.L (SAO RAS, Russia) e-mail: alexiya@sao.ru

Introduction NGC6104 is a peculiar barred galaxy (type S(R)pec in NED) with bright ring and active Sy 1.5 nucleus. The systemic velocity V=8430(z=0.0281) corresponds to the distance 112 Mpc (scale is 0.54 kpc/´´). DSS2 image of NGC 6104 reveals a distorted ìorphology of outerisophotes. Galaxy belongs to a dynamically young poor cluster Zwicky 1615.8+3505 and has a possible satellite CGCG1516.0+3550 atthe distance of 4 arcmin (Tomita et al., 1999). We have performed observations of NGC 6104 on the Russian 6m telescope, the observational program included deep optical imaging, long-slit spectroscopy and panoramic spectroscopy with integral-field spectrograph MPFS and scanning Interferometer Fabry-Perot (IFP). See http://www.sao.ru/hq/lsfvo/devices.html for the description of these devices.

Tomita A., Maehara H. et al., 1999, PASJ, 51, 285References

Direct images and spectroscopy of neighbor galaxies On the our deep B, V, R images we have detected arc like structures in outer parts of the galaxy, located on distances 70-90´´ (38-50 kpc) from the center. These arcs have red colors, they are very asymmetric towards galactic nucleus. Moreover, as could be seen on HST image, spiral arm is highly disturbed. All these features argue about merging or a recent tidal disruption. On the optical images we have detected 4 candidates to dwarf galaxies near NGC6104. In order to find out if anyone of these galaxies interacts with NGC6104 we have obtained their spectra. All these galaxies appeared to be background objects with z=0.10-0.36, therefore they can’t interact with NGC6104 and consequently can’t distorted galaxy morphology.

Panoramic spectroscopy MPFS takes simultaneously 256 spectra in 16x16´´ field. We have combined observations in two fields including nucleus, so the total field of view was 20x22´´. Based on these data we have mapped monochromatic images in the different emission lines ([OIII], [NII], [SII], Ha, Hb ). The velocity fields of the ionized gas and stars were constructed. Also we have obtained a large-scale ionized-gas velocity field of the galaxy from observations with scanning IFP in the Ha emission line.

Using of spectroscopic diagnostics for AGN revealed that gas in the central region has been excited by active nucleusradiation. Gas in the ring, as it follows from figure, ionized byhot star radiation that means that massive star burst is goingon. The IFP velocity field shows almost regular rotation, exceptcentral region (r<9´´) where significant turn of dynamical axesoccurs. That deviation is caused by the presence of bar. The velocity of stars agrees with ionized gas kinematics at least in the central region (in the MPFS field of view).

Based on our detail study of Sy galaxy NGC 6104 we can conclude that galaxy experienced impact with another galaxy, as result of this impact we can see arc like structures in the outer part of galaxy. This collision triggered and nuclei activity, distorted the spiral pattern and also created outer ``arcs’’. The impact there was about 0.5-1 Gyr ago, because the gas and stellar velocity maps already have not merging-like features, but outer tidal structures have not disappeared yet (time of turn on these distances is about 0.6 Gyr). The possible candidate to the impact is CGCG1516.0+3550 with characteristic time of flight this galaxy near NGC 6104 at least 1.2 Gyr.

HII

DSS image 10’ x 10’ V image (6m telescope) HST image (WFPC2)

B image (6m telescope) V image (6m telescope) R image (6m telescope) V-R image (SCORPIO BTA)

Velocity fields in SII, NII and OIII emission lines

IFP observations: continuum and Ha images, velocityfield of the ionized gas. The last plot shows the rotationcurve and the kinematic position angles. The dotted linemarks the line of nodes PA.

Line-ratio diagnostic diagram. Crosses mark the points in the nucleus, stars ans squares correspond to HII regions on the ends of the bar.

The diagram of main frequencies calculated from Ha rotation curve. The dashed line indicates the inner ring positions on the 4:1 resonance. The dotted line marks the possible angular velocity of the bar/spiral pattern.