4,955 research outputs found
Technique of Polarimetric Observations of Faint Objects at the 6-m BTA Telescope
We describe the technique of spectropolarimetric observations allowing for
the measurements of the Stokes parameters in one of the observational modes of
the SCORPIO focal reducer of the 6-m BTA telescope of the SAO RAS. The
characteristics of the instrument in the spectropolarimetric mode of
observations are given. We present the algorithm of observational data
reduction. The capabilities of the SCORPIO spectropolarimetric mode are
demonstrated on the examples of observations of various astronomical objects.Comment: 15 pages, 10 figure
Global Structure and Kinematics of the Spiral Galaxy NGC 2841
Investigation of gaseous and stellar kinematics and of broad-band VRI and
narrow-band H-alpha and [NII]6583 images is performed for the central part (R <
4 kpc) of the regular spiral galaxy NGC 2841. We have found emission-line
splitting at R < 20" and three-component LOSVD for the stars in the radius
range 6" - 100". Morphological analysis reveals strong narrow shock fronts
close to the major axis in the radius range of 30" - 50", a turn of the
isophote major axis by 5 degrees and strongly negative Fourier coefficient a4
(boxy isophotes) in the radius range of 15" - 33". In principle, all these
features may be explained in the frame of a triaxial bulge hypothesis.Comment: 20 pages, Latex aasms4.sty, 9 Postscript figures, accepted to A
The intraday variations of polarization vector direction in radio source S5 0716+714
The bright radio source S5 0716+714, that is usually classified as BL Lac
object, is one of the most intensively studied. S5 0716+714 demonstrates
extremely peculiar properties such as the shortest time-scale of optical and
polarimetric variations observed in blazars. In given paper, the results of
9-hour polarimetric monitoring of S5 0716+714 with the 70-second
resolution, carried out by the 6-m telescope BTA of SAO RAS, are presented. The
observation data analysis reveals the variability both in total and polarized
light on the 1-1.5-hour time-scale. Since polarization is generated by plasma
motion in the magnetic field, the variations of polarization vector are bounded
with the magnetic field configuration and the average time-scales specify the
size of the emitting region, unresolved directly. We suggest a processed
numerically model of polarization in the jet with the precessing helical
magnetic field. Fitting the model discovers that observed short-term variations
with the complicated trajectory of polarization vector could be induced by the
magnetic field precession with the period days.Comment: 7 pages, 9 figures; submitted to MNRA
New Extended Radio Sources From the NVSS
We report the results of the spectroscopic observations carried out at the
SAO RAS 6-m telescope for the optical components of nine new extended radio
sources found in the NVSS catalog. The measured redshifts of the host galaxies
are in the range of z=0.1-0.4. The physical sizes of radio sources were
calculated within the standard cosmological model. The two most extended
objects, 0003+1512 and 0422+0351 reach the sizes of 2.1 Mpc and 4.0 Mpc,
respectively. This is close to the maximum size of known radio sources.Comment: 5 pages, 9 figures, to be published in Astrophysical Bulletin, v. 70,
N
NGC 4245: one or two bars, and where does the gas inflow stop?
We have studied stellar and gaseous kinematics as well as stellar population
properties in the center of the early-type barred galaxy NGC 4245 by means of
integral-field spectroscopy. We have found a chemically distinct compact core,
more metal-rich by a factor of 2.5 than the bulge, and a ring of young stars
with the radius of 300 pc. Current star formation proceeds in this ring; its
location corresponds to the inner Lindblad resonance of the large-scale bar.
The mean age of stars in the chemically distinct core is significantly younger
than the estimate by Sarzi et al. (2005) for the very center, within R=0.25",
made with the HST spectroscopy data. We conclude that the `chemically distinct
core' is in fact an ancient ultra-compact star forming ring with radius less
than 100 pc which marks perhaps the past position of the inner Lindblad
resonance. In general, the pattern of star formation history in the center of
this early-type gas-poor galaxy confirms the predictions of dynamical models
for the secular evolution of a stellar-gaseous disk under the influence of a
bar.Comment: 4 pages, 3 figures. To appear in "Tumbling, twisting, and winding
galaxies: Pattern speeds along the Hubble sequence", E. M. Corsini and V. P.
Debattista (eds.), Memorie della Societa` Astronomica Italian
Polarization in the broad lines of NLSy1 and BLSy1 galaxies
We give an overview of the polarization in the broad lines of Active Galactic
Nuclei (AGNs), where we can use the polarization angle for determination of the
black hole masses (as given in [1]). Especially, we considered nine AGNs with
strong optical Fe II lines in the spectra, where five of them are typical
Narrow Line Sy1 (NLSy1) and four Broad Line Sy1 (BLSy1) AGNs . Comparing the
polarization parameters and black hole masses (obtained from polarization) we
confirmed that NLSy1 have smaller black hole masses than BLSy1, and seem to
have more compact Broad Line Region (BLR) and smaller inner torus radius than
BLSy1Comment: presented at conference "Revisiting narrow-line Seyfert 1 galaxies
and their place in the Universe - NLS1" Padova 9-13 April 2018 Padova
Botanical Garden, Ital
Spectropolarimetry of Seyfert 1 galaxies with equatorial scattering: Black hole masses and Broad Line Region characteristics
Here we present the spectropolarimetric observations of a sample of 30 Type 1
AGNs and an analysis of the observed polarization in these AGNs. The
observations have been performed with the 6-meter telescope of SAO RAS using
the modified SCORPIO-2 spectropolarimeter. We measured the Stokes parameters
for the continuum and the broad H line and obtained the values of
polarization degree and the angle of polarization. We found that equatorial
scattering is dominant polarization mechanism in the sample, that allows us to
use the observed polarization in the broad lines for determination of the
central black hole (BH) masses and characteristics (the inclination and
emissivity) of the Broad Line Region (BLR). We demonstrated that the recently
proposed method of \cite{ap15} for BH mass measurement gives accurate BH masses
which are in a good correlation with the stellar velocity dispersion, and
consequently the masses determined by the polarization method can be used with
calibration purposes. Additionally we found that the BLR in the sample of 30
AGN has an averaged inclination of (mostly between 20 and
40 degrees) and emissivity that is more flat than one
expected for the classical accretion disc .Comment: 19 pages, 15 figures, MNRAS accepte
IR Spectrometer Project for the BTA Telescope
We introduce a project of new cooled infrared spectrometer-photometer for 6-m
telescope BTA (Special Astrophysical Observatory of Russian Science Academy).
The device would extend the wavelength range accessible for observations on the
6-m BTA telescope toward near infrared (0.8-2.5 um)
Spectropolarimetric monitoring of active galaxy 3C390.3 with 6m telescope SAO RAS in the period 2009-2014
Here we present the spectropolarimetric observations of the radio loud active
galaxy 3C 390.3 in the period 2009-2014 (24 epochs). The galaxy has been
observed with the 6-meter telescope of SAO RAS using the SCORPIO
spectropolarimeter. We explore the variability and lags in the polarized light
of the continuum and broad H line. We give the Stokes parameters , degree of linear polarization and the position angle of the
polarization plane, , for 24 epochs.
We find a small lag~(10-40 days) between the unpolarized and polarized
continuum that is significantly smaller than the estimated lags for the
unpolarized broad emission lines (lag(H)138-186 and
lag(H)60-79 days). This shows that the region of the variable
polarized continuum is significantly smaller than the broad line region,
indicating that a part of the polarized continuum is coming from the jet. The
lag of the polarized light in the H line (89-156 days) indicates an
additional component to the disc one that has an outflowing velocity of
-1200 km s. This region seems to depolarize the polarized broad
H line emitted from the disc and scattered in the inner part of the
torus.Comment: 12 pages, 7 figures, MNRAS accepte
Variability in Spectropolarimetric properties of Sy 1.5 galaxy Mrk 6
Here we present an analysis of spectro-polarimetric observations of type 1.5
AGN Mrk 6, performed with 6m telescope SAO RAN in 12 epochs (2010 -- 2013).
Additionally, the inter-stellar mater (ISM) polarization has been observed and
its contribution to the AGN spectral polarization is taken into account.
We measured Stokes parameters and determined the polarization parameters in
12 spectra with and without correction for the ISM polarization. We estimated
the time lag between the unpolarized and polarized continuum flux variation of
about ~2 days, that indicates a compact scattering region which contributes to
the polarized continuum variability. The polarization in H{\alpha} is complex,
showing three prominent components in the BLR, one redshifted around +3000 km/s
that corresponds to the red shoulder in H{\alpha}, and two blue-shifted around
-2000 km/s and -6000 km/s.
We found that the ISM polarization has a very significant influence on the
measured AGN polarization parameters. After correcting the observations for the
ISM polarization we were able to detect the Keplerian motion in the BLR.
We give a new method for the black hole mass estimation using
spectro-polarimetric observation in the line profile, finding the black hole
mass in Mrk 6 of , that is in a good
agreement with reverberation estimates.Comment: Version submitted to MNRAS, after minor revisio
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