arXiv subjects

A. N. Burenkov

Publications and source records attributed to A. N. Burenkov.

47 records · Page 3Linked to original sources

arXiv2003

The phenomenon of the galaxy NGC 6286: a forming polar ring or a superwind?

(abridged)We present the observations of the pair of interacting galaxies NGC6285/86 carried out with the 6m SAO RAS telescope by using 1D and 2D spectroscopy. The observations of NGC6286 with a long-slit spectrograph (UAGS) near the H-alpha line revealed the rotation of the gaseous disk around an axis offset by 5''-7'' from the photometric center and a luminous gas at a distance up to 9 kpc in a direction perpendicular to the galactic plane. Using a multipupil fiber spectrograph (MPFS), we constructed the velocity fields of the stellar and gaseous components in the central region of this galaxy, which proved to be similar. The similar line-of-sight velocities of the pair and the wide (5'x 5') field of view of the scanning Fabry-Perot interferometer (IFP) allowed us to obtain images in the H-alpha and [NII]6583 emission lines and in the continuum as well as to construct the line-of-sight velocity fields and to map the distribution of the [NII]6583/H-alpha ratio for both galaxies simultaneously. Based on these data, we studied the gas kinematics in the galaxies, constructed their rotation curves, and estimated their masses. We found no evidence of gas rotation around the major axis of NGC6286, which argues against the assumption that this galaxy has a forming polar ring. The IFP observations revealed an emission nebula around this galaxy with a structure characteristic for superwind galaxies. The large [NII]6583/H-alpha ratio, which suggests the collisional excitation of its emission, and the high infrared luminosity are additional arguments for the hypothesis of a superwind in the galaxy NGC 6286. A close encounter of the two galaxies was probably responsible for the starburst and the bipolar outflow of hot gas from the central region of the disk.

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arXiv2002

Rarefied Gaseous Disk Around Black Hole in the System of V4641 Sgr

The results of photometric CCD monitoring and spectral observations of the black hole binary and microquasar V4641 Sgr in the quiet state are presented. The ellipsoidal light curve with large amplitude of 0.36^m in R band suggests the influence of a massive object orbiting around a normal B9 star. In the spectra taken with the 6-m telescope one hour before black hole inferior conjunction, an absorption component in the red wing of Halpha line is visible. It is formed by gaseous stream moving in the direction to the normal star. That suggests the grazing conjunction in this system. Maximum velocity of the stream is of 650 km/s. Assuming that the stream is moving through the circular Keplerian orbit around black hole, the mass of the black hole is determined to be M_{BH}=7.1-9.5Msun, what confirms the model by Orosz et al.

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arXiv2002

Age and metallicity of a globular cluster in the dwarf spheroidal galaxy DDO78

We present the results of moderate resolution spectroscopy for a globular cluster in the M81 group dwarf spheroidal galaxy DDO~78. The DDO78 globular cluster, 4 Milky Way globular clusters, spectroscopic and radial velocity standards were observed with the Long-slit spectrograph of the 6-m telescope (SAO RAS, Russia). Lick spectrophotometric indices were determined in the bandpasses adopted by Burstein et al. (1984). We have derived the mean metallicity of the globular cluster in DDO78 to be [Fe/H] = -1.6 +- 0.1 dex by taking the weighted mean of metallicities obtained from the strength of several absorption features. We have estimated an age for the globular cluster of 9-12 Gyr similar to that found for the Galactic globular cluster NGC362, which resembles our cluster by chemical abundance and integrated spectrophotometric properties.

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arXiv2001

Radial Velocities of Dwarf Spheroidal Galaxies in the M81 Group

Long-slit observations of 4 dwarf spheroidal galaxies in the M81 group are presented. We have obtained a heliocentric velocity of globular cluster candidate located near the center of DDO78 to be +55 +- 10 km/s by cross-correlation with template stars. We estimated a heliocentric radial velocity of -116 +- 21 km/s for an HII region seen in the K 61. A red diffuse object near the K64 center is found to be a remote galaxy with a heliocentric velocity of +46530 km/s.

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arXiv2001

Intermediate resolution H-beta spectroscopy and photometric monitoring of 3C 390.3 I. Further evidence of a nuclear accretion disk

We have monitored the AGN 3C390.3 between 1995 and 2000.Two large amplitude outbursts, of different duration, in continuum and H beta light were observed ie.: in October 1994 a brighter flare that lasted about 1000 days and in July 1997 another one that lasted about 700 days were detected. The flux in the H beta wings and line core vary simultaneously, a behavior indicative of predominantly circular motions in the BLR.Important changes of the Hbeta emission profiles were detected: at times, we found profiles with prominent asymmetric wings, as those normaly seen in Sy1s, while at other times, we observe profiles with weak almost symmetrical wings, similar to those seen in Sy1.8s. We found that the radial velocity difference between the red and blue bumps is anticorrelated with the light curves of H beta and continuum radiation.e found that the radial velocity difference between the red and blue bumps is anticorrelated with the light curves of H-beta and continuum radiation. Theoretical H-beta profiles were computed for an accretion disk, the observed profiles are best reproduced by an inclined disk (25 deg) whose region of maximum emission is located roughly at 200 Rg. The mass of the black hole in 3C 390.3, estimated from the reverberation analysis is Mrev = 2.1 x 10^9 Msun, ie. 5 times larger than previous estimates

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arXiv2000

Survey of rotation curves for northern spiral edge-on galaxies

Rotational curves are measured for almost complete sample of 308 northern spiral galaxies using the 6-m telescope. For observations we selected edge-on galaxies from RFGC catalog with apparent axial ratio a/b>8, angular diameter a<2', and declinations delta>+38deg above the Arecibo belt. About 97% of the galaxies are detected in the H-alpha line. For them a typical rotation curve extends till 87% of the standard galaxy radius. The rotation curve amplitude shows close correlation with a width of the HI line. The median radial velocity for the galaxies is 7800 km/sec, and the median maximum of the rotation curves is 137 km/s. These new observational data will be used to study cosmic streamings of galaxies seen on a scale of 200 Mpc.

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arXiv2000

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.

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arXiv1998

Chemically Decoupled Nuclei in the Spiral Galaxies NGC 4216 and NGC 4501

By using bidimensional spectral data obtained at the 6m telescope for the Virgo spirals NGC 4216 and NGC 4501, we have found chemically distinct metal-rich nuclei in these galaxies. Under the assumption of equal ages for the nuclear and bulge stellar populations, the metallicity difference between the nuclei and their environments in the galaxies is estimated as a factor of 2. But we have also found an age difference between the nucleus and the bulge in NGC 4216: age-metallicity disentangling on the diagrams (H-beta, Mgb), (H-beta, [MgFe]), and (H-beta, $ $) results in an age estimate for the nucleus of 8 - 12 billion years, the bulge being older by a factor of 1.5 - 2; and the self-consistent metallicity difference estimate is then a factor of 3. The solar magnesium-to-iron ratios in the galactic nuclei show evidence for a long duration of the secondary nuclear star formation bursts which produced the chemically distinct stellar subsystems. Detailed morphological and kinematical analyses made for the stellar and gaseous structures in the centers of NGC 4216 and 4501 have revealed the presence of circumnuclear stellar-gaseous disks with radius of some hundreds parsecs which demonstrate fast axisymmetric rotation and lie exactly in the planes of the main galactic disks.

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arXiv1998

Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XV. Long-Term Optical Monitoring of NGC 5548

We present the results of three years of ground-based observations of the Seyfert 1 galaxy NGC 5548, which combined with previously reported data, yield optical continuum and broad-line H-beta light curves for a total of eight years. The light curves consist of over 800 points, with a typical spacing of a few days between observations. During this eight-year period, the nuclear continuum has varied by more than a factor of seven, and the H-beta emission line has varied by a factor of nearly six. The H-beta emission line responds to continuum variations with a time delay or lag of 10-20 days, the precise value varying somewhat from year to year. We find some indications that the lag varies with continuum flux in the sense that the lag is larger when the source is brighter.

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arXiv1998

The stellar population of the decoupled nucleus in M 31

The results of a spectroscopic and photometric investigation of the central region of M 31 are presented. An analysis of absorption-index radial profiles involving magnesium, calcium, and iron lines has shown that the unresolved nucleus of M 31 is distinct by its increased metallicity; unexpectedly, among two nuclei of M 31, it is the faintest one located exactly in the dynamical center of the galaxy (and dynamically decoupled) which is chemically distinct. The Balmer absorption line H-beta has been included into the analysis to disentangle metallicity and age effects; an age difference by a factor 3 is detected between stellar populations of the nucleus and of the bulge, the nucleus being younger. The morphological analysis of CCD images has revealed the presence of a nuclear stellar-gaseous disk with a radius of some 100 pc, the gas component of which looks non-stationary, well inside the bulge of M 31.

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arXiv1997

Decoupled Nuclei and Nuclear Polar Rings in Regular Spiral Galaxies. NGC 2841

The Sb galaxy NGC 2841 was observed at the 6 m telescope of SAO RAS with the Multi-Pupil Field Spectrograph and at the 1 m telescope of SAO RAS with the long-slit spectrograph. An unresolved nucleus of NGC 2841 is shown to be chemically decoupled both in magnesium and in iron with abundance break estimates of 0.36 dex for Mg and 0.6 dex for Fe; an abundance gradient in the bulge is seen only in the magnesium index and is typical for early-type disk galaxies. The rotation axis of the nuclear ionized gas in NGC 2841 is orthogonal to that of the central stellar population; an existence of a bulge stellar component with decoupled rotation momentum in the radius range 5" -12" is suspected. A possible scenario for the origin of the unusual central structure in NGC 2841 is proposed.

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