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Nizhniy Arkhyz, Russia

Moiseev A.V.,Special Astrophysical Observatory
Astronomy and Astrophysics | Year: 2012

Context. Knotty structures of Herbig-Haro jets are common phenomena, and knowing the origin of these structures is essential for understanding the processes of jet formation. Basically, there are two theoretical approaches: different types of instabilities in stationary flow, and velocity variations in the flow. Aims. We investigate the structures with different radial velocities in the knots of the HL Tau jet as well as its unusual behaviour starting from 20′′ from the source. Collation of radial velocity data with proper motion measurements of emission structures in the jet of HL Tau makes it possible to understand the origin of these structures and decide on the mechanism for the formation of the knotty structures in Herbig-Haro flows. Methods. We present observations obtained with a 6 m telescope (Russia) using the SCORPIO camera with scanning Fabry-Perót interferometer. Two epochs of the observations of the HL/XZ Tau region in Hα emission (2001 and 2007) allowed us to measure proper motions for high and low radial velocity structures. Results. The structures with low and high radial velocities in the HL Tau jet show the same proper motion. The point where the HL Tau jet bents to the north (it coincides with the trailing edge of so-called knot A) is stationary, i.e. does not have any perceptible proper motion and is visible in Hα emission only. Conclusions. We conclude that the high-and low-velocity structures in the HL Tau jet represent bow-shocks and Mach disks in the internal working surfaces of episodic outflows. The bend of the jet and the brightness increase starting some distance from the source coincides with the observed stationary deflecting shock. The increase of relative surface brightness of bow-shocks could be the result of the abrupt change of the physical conditions of the ambient medium as well as the interaction of a highly collimated flow and the side wind from XZ Tau. © 2012 ESO. Source


Katkov I.Y.,Moscow State University | Sil'Chenko O.K.,Moscow State University | Afanasiev V.L.,Special Astrophysical Observatory
Monthly Notices of the Royal Astronomical Society | Year: 2014

A sample of completely isolated S0 galaxies has been studied by means of long-slit spectroscopy at the Russian 6-m telescope. Seven of 12 galaxies have revealed the presence of extended ionized-gas discs whose rotation is mostly decoupled from the stellar kinematics. Five of these seven (71 ± 17 per cent) galaxies show a visible counterrotation of the ionized-gas component with respect to the stellar component. The emission-line diagnostics demonstrates a wide range of gas excitation mechanisms, although pure excitation by young stars is rare. We conclude that in all cases the extended gaseous discs in our sample S0s are of external origin, despite the visible isolation of the galaxies. Possible sources of external accretion, such as systems of dwarf gas-rich satellites or cosmological cold-gas filaments, are discussed. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source


Doroshkevich A.,RAS Lebedev Physical Institute | Verkhodanov O.,Special Astrophysical Observatory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We show that the popular internal linear combination approach is unstable with respect to division of the observed map pixels to a set of "homogeneous" subsamples. For various choices of such subsamples we can obtain a restored CMB signal with amplitudes ranging from zero to the amplitude of the observed signal. We propose an approach which allows us to obtain corrected estimates of the CMB power spectrum C at ≤30 and provides results similar to WMAP for larger . Using this approach, we eliminate some anomalies of the WMAP results. In particular, our estimate of the quadrupole is consistent with the theoretically expected one. The effect of the "axis of evil" is suppressed, and the symmetry of the north and south galactic hemispheres increases. These results can change estimates of quadrupole polarization and the redshift of reionization of the Universe. We also propose a new simple approach which can improve the WMAP estimates of the high power spectrum. © 2011 American Physical Society. Source


Verkhodanov O.V.,Special Astrophysical Observatory
Physics of Particles and Nuclei | Year: 2015

We consider the main anomalies of cosmic microwave background observed at low multipoles of the WMAP and Planck cosmic missions. The possible origin of these features is discussed. We study difference between WMAP and Planck data which is apparently connected with the local sources emission and/or systematics. © 2015, Pleiades Publishing, Ltd. Source


Medvedev A.,Moscow State University | Fabrika S.,Special Astrophysical Observatory
Monthly Notices of the Royal Astronomical Society | Year: 2010

We analysed the XMM-Newton spectra of SS 433 using a standard model of adiabatically and radiatively cooling X-ray jets. The multitemperature thermal jet model reproduces the strongest observed emission line fluxes well. Fitting the He- and H-like iron line fluxes, we find that the visible blue jet base temperature is ∼17 keV, the jet kinetic luminosity Lk ∼ 2 × 1039 erg s-1 and the absorbing column density NH ∼ 1.5 × 1022 cm-2. All these parameters are in line with previous studies. The thermal model alone cannot reproduce the continuum radiation in the XMM spectral range, nor the fluorescent iron line and some of the broad spectral features. Using the thermal jet-plus-reflection model, we find a notable contribution of ionized reflection to the spectrum in the energy range from ∼3 to 12 keV. The reflecting surface is highly ionized (∼~ 300), and the illuminating radiation photon index changes from Γ ap; 2 (a flat spectrum) in the range 7-12 keV to Γ ≈ 1.6 in the range 4-7 keV, and to Γ≲ 1 in the range 2-4 keV. We conclude that the reflected spectrum is evidence of the supercritical disc funnel, whereby the illuminating radiation comes from deeper funnel regions, to be further reflected in the outer visible funnel walls r≳ 2 × 1011 cm). In the multiple scatterings in the funnel, the harder radiation >7 keV may survive absorption, but softer radiation is absorbed, making the illuminating spectrum curved. We have not found any evidence of reflection in the soft 0.8-2 keV energy range; instead, a soft excess is detected, which does not depend on the details of the thermal jet model. However, the soft component spectrum is basically unknown. This soft component might prove to be the direct radiation of the visible funnel wall. It is represented here either as blackbody radiation with a temperature of θbb≈ 0.1 keV and a luminosity of Lbb∼ 3 × 1037 erg s-1, or with a multicolour funnel model. The soft spectral component has parameters roughly the same as those found in ultraluminous X-ray sources. © 2009 The Authors. Journal compilation © 2009 RAS. Source

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