Star formation in outer rings of S0 galaxies. I. NGC 6534 and MCG 11-22-015

Though S0 galaxies are usually thought to be `red and dead', they often demonstrate star formation organized in ring structures. We try to clarify the nature of this phenomenon and its difference from star formation in spiral galaxies. Two early-type galaxies with outer rings, NGC 6534 and MCG 11-22-015, are selected to be studied. The ionized gas is excited by young stars in the ring of NGC 6534 and partly by shocks -- in MCG 11-22-015. The oxygen abundances in the HII regions of the rings are close to solar. We estimate the star formation rates (SFR) in the two outer rings of the galaxies by using several SFR indicators derived from narrow-band photometry in the H-alpha emission line and archival GALEX ultraviolet images of the galaxies. The derived SFRs allow to qualitatively restore star formation histories (SFH) in the rings: in NGC 6534 the SFH is flat during the last 100-200 Myr, and in MCG 11-22-015 the star formation has started only a few Myr ago. We suggest that the rings in NGC 6534 and MCG 11-22-015 have different natures: the former is a resonant one supplied with gas perhaps through tidal effects, and the latter has been produced by a satellite accretion. Recent outer gas accretion is implied in both cases.Comment: 5 pages, 6 figures, accepted into the Astronomy and Astrophysic

Possibly interacting Vorontsov-Velyaminov galaxies. I. Observations of VV432, VV543 and VV747

Among the galaxies which were included in the Atlas and Catalogue of Interacting galaxies by Vorontsov-Velyaminov (hereafter VV) as multiple systems ("nests", "chains" and similarly looking systems), there are many objects, where the interaction is not evident. Some of them are single objects, including low-mass galaxies with active star formation (SF). In this work we present the description of observations and results of the long-slit spectrophotometry with the Russian 6-m telescope of three VV-galaxies looking like double or multiple systems, and HI-observations of one of them in order to elucidate their nature, determine their metallicity, kinematic properties and the evolution status. Galaxies VV432 and VV747 are found to be dwarf systems with low oxygen abundance (O/H = 1/22 and 1/12 of the solar value, respectively). Their velocity curves indicate quite slow rotation with respective maximum velocities of about 60 and 80 km/s, in agreement with their low luminosities. The distance to VV432 is rather uncertain. If it is a member of Virgo Cluster, this is the most metal-deficient known galaxy of this aggregate. For galaxy VV543 the measured emission-line redshift 0.047 appeared ten times larger than it was given in the original paper and is cited in databases. This "system" evidently represents an optical pair of two galaxies with large velocity difference. The fainter western component is an HII-galaxy, while the brighter one is an absorption-line early-type galaxy with the radial velocity being 1600 km/s lower.Comment: 11 pages, A&AS in press. Version of the paper with Figures 1-3 of the higher quality is available via http://precise.sao.ru/Laboratory/Publications/2000_pub.htm

Spectral monitoring of AGNs: Preliminary results for Ark 564 and Arp 102B

We present preliminary results of the long term spectral monitoring of two active galactic nuclei with different broad line shapes: Ark 564 and Arp 102B. Ark 564 is a bright nearby narrow line Syfert 1 (NLS1) galaxy with relatively narrow permitted optical emission lines and a high FeII/H${\beta}$ ratio, while Arp 102B is a nearby broad-line radio galaxy with broad double-peaked Balmer emission lines. The spectra of Ark 564 were observed during 11-year period (1999-2009) and the spectra of Arp 102B in the 12-year period (1998-2009), with SAO 6-m and 1-m telescopes (Russia) and the GHAO 2.1-m telescope (Cananea, Mexico).Comment: Presented on "8th Serbian Conference on Spectral Line Shapes in Astrophysics". In revised version minor changes in the tex

Two epoch spectro-imagery of FS Tau B outflow system

Herbig-Haro (HH) flows exhibit a large variety of morphological and kinematical structures such as bow shocks, Mach disks, and deflection shocks. Both proper motion (PM) and radial velocity investigations are essential to understand the physical nature of such structures. We investigate the kinematics and PM of spectrally separated structures in the FS~Tau~B HH flow. Collating these data makes it possible to understand the origin of these structures and to explain the unusual behavior of the jet. On the other hand, the study of emission profiles in the associated reflection nebulae allows us to consider the source of the outflow both from edge-on and pole-on points of view. We present the observational results obtained with the 6 m telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences using the SCORPIO multimode focal reducer with a scanning Fabry-Perot interferometer. Two epochs of the observations of the FS~Tau~B region in H$\alpha$ emission (2001 and 2012) allowed us to measure the PM of the spectrally separated inner structures of the jet. In addition to already known emission structures in the FS~Tau~B system, we discover new features in the extended part of the jet and in the counter-jet. Moreover, we reveal a new HH knot in the HH~276 independent outflow system and point out its presumable source. In the terminal working surface of the jet, structures with different radial velocities have PMs of the same value. This result can be interpreted as the direct observation of bow-shock and Mach disk regions. A bar-like structure, located southwest from the source demonstrates zero PM and can be considered as one more example of deflection shock. An analysis of H$\alpha$ profiles in the reflection nebulae R1 and R3 indicates the uniqueness of this object, which can be studied in pole-on and edge-on directions simultaneously.Comment: 8 pages, 11 figure

Long-term variability of the optical spectra of NGC 4151: II. Evolution of the broad Ha and Hb emission-line profiles

Results of the long-term (11 years, from 1996 to 2006) H$\alpha$ and H$\beta$ line variations of the active galactic nucleus of NGC 4151 are presented. High quality spectra (S/N>50 and R~8A) of H$\alpha$ and H$\beta$ were investigated. We analyzed line profile variations during monitoring period. Comparing the line profiles of H$\alpha$ and H$\beta$, we studied different details (bumps, absorption features) in the line profiles. The variations of the different H$\alpha$ and H$\beta$ line profile segments have been investigated. Also, we analyzed the Balmer decrement for whole line and for line segments. We found that the line profiles were strongly changing during the monitoring period, showing blue and red asymmetries. This indicates a complex BLR geometry of NGC 4151 with, at least, three kinematically distinct regions: one that contributes to the blue line wing, one to the line core and one to the red line wing. Such variation can be caused by an accelerating outflow starting very close to the black hole, where the red part may come from the region {closer to the black hole than the blue part, which is coming} from the region having the highest outflow velocities. Taking into account the fact that the BLR of NGC 4151 has a complex geometry (probably affected by an outflow) and that a portion of the broad line emission seems to have not a pure photoionization origin, one can ask the question whether the study of the BLR by reverberation mapping may be valid in the case of this galaxy.Comment: 24 pages, 18 figures, accepted for publications in A&