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

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

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&

Tunneling of polarized fermions in 3D double wells

We study the tunneling of a spin polarized Fermi gas in a three-dimensional double well potential, focusing on the time dynamics starting from an initial state in which there is an imbalance in the number of particles in the two wells. Although fermions in different doublets of the double well tunnel with different frequencies, we point out that (incoherent) oscillations of a large number of particles can arise, as a consequence of the presence of transverse degrees of freedom. Estimates of the doublet structure and of the occupation of transverse eigenstates for a realistic experimental setup are provided.Comment: 10 pages, Typos corrected and figures changed - published in Laser Physics, issue on the LPHYS'11 conference (Sarajevo, 2011

On boundedness of the generalized Riesz potential in local Morrey-type spaces

For all admissible values of the numerical parameters sharp sufficient conditions on the functional parameters are obtained ensuring the boundedness of the generalized Riesz potential from one general local Morrey-type space to another one, which, for a certain range of the numerical parameters, coincide with the necessary ones

Optical study of the polar BM CrB in low accretion state

This paper presents a spectral and photometric study of the poorly studied polar BM CrB. Three states of the polar brightness and signs of transition from one-pole to two-pole accretion mode were found by an analysis of ZTF data. It is shown that the transition from the low state to the high state changes the longitude of the main accretion spot (by $\approx 17^{\circ}$) and increases its elongation (by $\approx 10^{\circ}$). The spectra contain Zeeman absorptions of the H$\alpha$ line which are formed at a magnetic field strength of $15.5\pm1$ MG. These absorptions are likely produced by a cold halo extending from the accretion spot at $\approx {^1/_4}$ of the white dwarf radius. Modeling of the behavior of the H$\alpha$ emission line shows that the main source of emission is the part of the accretion stream near the Lagrangian point L$_1$, which is periodically eclipsed by the donor star. The spectra exhibit a cyclotron component formed in the accretion spot. Its modeling by a simple accretion spot model gives constraints on the magnetic field strength $B=15-40$ MG and the temperature $T_e\gtrsim15$ keV