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 outer
isophotes. Galaxy belongs to a dynamically young poor cluster Zwicky 1615.8+3505 and has a possible satellite CGCG1516.0+3550 at
the 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.
V image (6m telescope)
DSS image 10’ x 10’
HST image (WFPC2)
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.
B image (6m telescope)
V image (6m telescope)
R image (6m telescope)
V-R image (SCORPIO BTA)
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.
Velocity fields in SII, NII and OIII emission lines
Using of spectroscopic diagnostics for AGN revealed that
gas in the central region has been excited by active nucleus
radiation. Gas in the ring, as it follows from figure, ionized by
hot star radiation that means that massive star burst is going
on.
The IFP velocity field shows almost regular rotation, except
central region (r<9´´) where significant turn of dynamical axes
occurs. 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).
HII
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.
IFP observations: continuum and Ha images, velocity
field of the ionized gas. The last plot shows the rotation
curve and the kinematic position angles. The dotted line
marks the line of nodes PA.
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.
References
Tomita A., Maehara H. et al., 1999, PASJ, 51, 285