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Daugėjant įrodymų, kad žvaigždės formuojasi spiečiais, jų masių funkcijos ir evoliucijos savybes kol kas galima nustatyti empiriniais stebėjimais. Tačiau tirti žvaigždėdaros procesą mūsų Galaktikoje galima ribotai. Andromedos galaktika (M31) yra artimiausia žvaigždžių sistema, panaši į Galaktiką. Todėl ji tinkamiausia žvaigždžių spiečių populiacijai tirti, tačiau ilgą laiką buvo tirta ribotai dėl tankių žvaigždžių laukų stebėjimo sudėtingumo. Naudojant „Subaru“ teleskopo Suprime-Cam plataus lauko nuotraukas, buvo ištirti žvaigždžių spiečiai M31 galaktikos disko srityje, kuri pagal cheminę sudėtį, žvaigždinį tankį ir mažą žvaigždėdaros spartą yra analogiška Saulės aplinkai mūsų Galaktikoje. Buvo sukurti, išbandyti ir pritaikyti duomenų analizės metodai ir programos tankiems plataus lauko vaizdams apdoroti ir pusiau išskiriamų žvaigždžių spiečių evoliuciniams parametrams nustatyti. Pagrindiniai rezultatai: (1) žvaigždžių spiečių formavimosi spartos sustiprėjimas M31 galaktikoje įvyko prieš ~70 mln. m.; (2) maždaug 10% žvaigždžių spiečių gyvena ilgiau nei 100 mln. m.; (3) būdingoji ~10^4 Saulės masių spiečiaus gyvavimo trukmė yra ~300 mln. m.; (4) žvaigždžių spiečių masių pasiskirstymas panašus į kitų mažos žvaigždėdaros spartos galaktikų žvaigždžių spiečių pasiskirstymą ir jį gerai nusako Schechter'io funkcija, kurios charakteringoji masė ~2x10^5 Saulės masių. Tai rodo, kad M31 galaktikoje yra gausi vidutinės masės žvaigždžių spiečių populiacija, kuri mūsų Galaktikoje yra... [toliau žr. visą tekstą] Observational evidence that star formation proceeds in a clustered manner raises a question on the mass function of star clusters and their evolution. However, we have a limited scope of these processes in the Milky Way galaxy. The M31 galaxy is the nearest stellar system similar to our Galaxy, therefore, it is the most suitable one to provide clues for understanding the star cluster population and the evolution of galactic structures. However, detailed study of stellar populations and star clusters is a challenging task for ground-based observations due to crowded stellar fields. Using Subaru telescope Suprime-Cam wide-field images, a survey of clusters was carried out in the disk region of the M31 galaxy southwest field, which is a close analogue to that of the Solar neighborhood in terms of chemical composition, stellar density, and quiescent star formation. Data analysis methods and programs were developed, tested, and applied for crowded wide-field image reduction and evolutionary parameter determination of semi-resolved star clusters. The main results are: (1) enhanced star cluster formation activity in M31 occurred ~70 Myr ago; (2) approximately 10% of stars born in star clusters remain there at 100 Myr age; (3) the characteristic lifetime of a cluster of ~10^4 solar masses mass is ~300 Myr; (4) the mass function of star clusters in M31 is similar to that in other low star formation activity galaxies and it is best described by the Schechter's function with a... [to full text]

A new code for the evaluation of light absorption and scattering by interstellar dust grains is presented. The radiative transfer problem is solved by using ray-tracing algorithm in a self-consistent and highly efficient way. The code demonstrates performance and accuracy similar or better than that of previously published results, achieved using Monte-Carlo methods, with an accuracy better than ˜ 1% for most cases. The intended application of the code is spectrophotometric modeling of disk galaxies, however, it can be easily applied to other cases that require a detailed spatial evaluation of scattering, such as circumstellar disks and shells containing both point and extended light sources.

We have analyzed 1+2+4+6 cm VLBA polarization data for the TeV BL Lac object Mrk 501 obtained at three epochs separated by 3--4 weeks in 1998 March--April. These observations show no significant total-intensity or polarization variability over the interval covered by the observations, supporting previous claims that variability in the parsec-scale structure of this source (e.g., motions in its VLBI jet) is modest. The B field structure is complex, and shows a sheath-like structure. The rotation-measure distribution shows evidence for variations across the jet, suggesting the presence of a helical B field associated with the VLBI jet.

A sample of BL Lac objects at radio wavelengths with arcsecond and milliarcsecond resolution is investigated. The sample consists of 30 objects, with redshift z < 0.2 and all previously observed with HST. The objects, nearby and mostly X-ray selected, are weak in the radio and little information in this band is available. The observations with the VLA, VLBA, EVN and MERLIN are completed. We present and discuss the morphology of the objects and the overall properties of the sample. In particular, the parent population and a comparison to the optical HST nuclei are considered.

Radio observations of gravitational lenses are an important case in which the data reduction and scientific analysis should and need not be separated. We present results of LENSCLEAN applied to a lensed BL Lac object B0218+357 showing the power of combining the two tasks. LENSCLEAN produces improved maps and constrains the lens model by minimizing the residuals between the best lensed source emission model and the observed data. One important result is an estimate of the Hubble constant from the time-delay in the lens B0218+357.

Seventy years after the start of radio astronomical observations and over 50 years after the first observations of the 21 cm H.

We assume a large-scale feature of the Galactic background, the North Polar Spur (NPS), being a jet of the Milky Way galaxy. The suggested interpretation explains the visible circular structure of NPS. The jet may be enveloped by an extended cocoon of a jet-long diameter. The hypothesis is supported by analysis of the physical parameters of NPS.

The space distribution of stars of various types is investigated in a 1.5 square degree area at the Galactic equator (l = 146 degrees, b = +2.6 degrees) in Camelopardalis, in the direction of the association Cam OB3. The study is based on photometric classification, interstellar extinction and distance determination of 1303 stars down to 15.5 mag (in the violet). The limiting distance of the study is about 5 kpc, thus our line of sight crosses the Perseus and the Outer spiral arms. The space density of stars of different spectral types and the luminosity function are determined.

Using the VLA and the VLBA we have observed water maser emission in the proto-planetary nebula candidate IRAS 19134+2131, in which the water maser spectrum has double radial-velocity peaks separated by ˜100 km s-1. The main purpose of this study is to reveal the 3-D kinematics of the masers in detail, which indicates a fast ( ˜110 km s-1) bipolar flow seen only during ≤100 years at the proto-planetary forming stage. At the same time, we have measured the Galactic rotation of IRAS 19134+2131 and its distance on the basis of differential VLBI technique to precisely measure relative positions of the maser features with respect to the nearby extragalactic reference source J1925+2106. We obtain a secular motion of IRAS 19134+2131 of μ l=: -4.6±0.7 mas yr-1 along the Galactic plane toward the Galactic center. This indicates a ``far distance" (≥16 kpc) for IRAS 19134+2131, located in the fourth quadrant in the Galaxy, if the Galactic rotation curve remains flat at 220 km s-1.

ESO 422-G028 denotes the central galaxy of the giant radio source B0503-286. Here we present new high-frequency total-power and polarization radio maps of the source obtained with the Effelsberg 100 m radio telescope. Also we correlate the radio data with optical and X-ray observations to investigate the physical conditions of the host galaxy and the extended structure.

We present the first results of analysis of WMAP foreground extragalactic sources from the 1-22 GHz broad-band spectra obtained with the RATAN-600 radio telescope in 1997--2003. The following characteristics of the sources are discussed: correlation of WMAP-RATAN data, spectral features, variability over the 2.3--22 GHz range, WMAP sample completeness. We compare them with characteristics of an about ten times larger sample of AGN, which is correlated flux density limited at 2.3 GHz. We infer that the WMAP sample is complete down to about 1.5 Jy. WMAP has selected, in general, sources with dominated variable emission of relativistic jets. The sample consists, on the average, of objects with higher variability and flatter spectra and is a tail of the general population of extragalactic radio sources.

Powerful radio galaxies often display regions of enhanced optical/ UV emission, elongated and aligned with the radio jet axis. The expanding radio source strongly affects the surrounding IGM, and the properties of the aligned emission regions vary considerably with both radio source properties and cosmic epoch. The results of deep rest-frame UV and optical imaging of high redshift 6C radio galaxies are discussed, considering the influence of radio power on the strength of the observed alignment effect, the galaxy colors and the dominant emission mechanisms.

An earlier comparison of simultaneous optical and 6 cm VLBI observations of polarization showed a correlation of their position angles which were either aligned or perpendicular. Gabuzda et al. (2005) proposed that the radio cores with their polarization aligned with optical polarization were predominantly optically thin, while the radio cores whose polarization was perpendicular to optical polarization were optically thick. We present the first results from new coordinated optical and high-frequency VLBA polarization observations of 15 AGNs designed to test this hypothesis.

The redshifts of faint radio galaxies identified with giant radio galaxy candidates selected from the sample of Machalski et al. (2001) have been measured. Given the redshift, the projected linear size and radio luminosity are then determined. The above data, supplemented with the axial ratio of the sources (evaluated from the radio maps) allow to constrain their jet power and the dynamical age using the analytical model of Kaiser et al. (1997) but modified by allowing the axial ratio of the source cocoon to evolve in time.

For investigation of the nature of GPS/HFP (`gigahertz peaked-spectrum / high-frequency peakers', possible young developing radio sources) it is important to construct robust, representative flux-density-limited samples. To look for spectra of the GPS/HFP type, we have used our RATAN-600 instantaneous broad-band 1--22 GHz spectra measurements of about 2000 compact extragalactic radio sources done in 1997--2003. We have found that some objects from published GPS/HFP samples change their spectra in time becoming non-GPS/HFP sources. We call such objects ``temporary GPS/HFP'' and suggest to use them cautiously. GPS/HFP-like type of spectrum can often be produced by an AGN during early stages of strong radio flares, and usually such a spectrum evolves to a flat one. A GPS-type spectrum could also be observed during a quiescent state of a relativistic jet when emission of an extended, slowly variable component of the source dominates. Some new GPS candidates are also found.

An improved theoretical multiplicity function by means of the excursion set approach is found. The barrier shape used implicitly takes into account the total angular momentum acquired by the proto-structure during evolution and the non-zero cosmological constant. The theoretical multiplicity function obtained in the present paper is compared with analytical and numerical multiplicity functions of other authors. It is shown that when one takes into account the total angular momentum., acquired by the proto-structure during evolution, the multiplicity function obtained is in a better agreement with Yahagi, Nagashima & Yoshii (2004) simulations than with the results of other previous models. Differently from some previous multiplicity function models, the theoretical mass function of the present paper is obtained from a sound theoretical background and not by a simple numerical fit. However. the current level of disagreement between different simulations is not sufficient,to favor one mass function over another when the differences are at the 10 percent level. Hence, at the present time all of these mass functions are essentially equivalent.

We are in the process of performing a circular polarization analysis of 2, 4 and 6 cm VLBA data for a complete sample of 34 1 Jy Northern BL Lac objects based on the method developed by Homan & Wardle (1999). We present here our results to date for about 70% of the sample. We have detected circular polarization in the core regions of about 20% of these sources at 2 cm and 6 cm, and in a somewhat higher fraction, 30--35%, at 4 cm. The degrees of circular polarization are similar to those detected for compact AGN in previous studies, with typical values of a few tenths of percent.

A method of obtaining jet physical parameter combinations (such as magnetic field strength, jet or knot velocity, etc.) is offered by studying knot “flares” in radio- and X-ray domains.

The time evolution of giant (D > 1 Mpc) lobe-dominated galaxies is analyzed on the basis of dynamical evolution of the entire FR II-type population.

Very deep 4.9 GHz observations with the VLA are used to supplement available radio maps at the frequencies of 325 MHz (WENSS, survey) and 1.4 GHz (NVSS survey) in order to study the synchrotron spectra and radiative ages of relativistic particles in the extended lobes of distant giant radio galaxies selected from the sample of Machalski et al. (2001).

The widely accepted AGN unification model has been developed by introduction of a constant factor representing deceleration. Assuming special relativity formulae and the orientation of the outflow with respect to the observer, we are able to model the main shapes of the radio emission structures of FR 1 and FR 2 types. The differences of radio structures of both types can be reproduced by changing the model parameters.

If the transverse jet B fields observed in BL Lac objects on parsec-scales represent the toroidal component of the jet B fields, this should give rise to rotation-measure gradients across the jets, due to the systematic change in the line-of-sight component of the jet B field. We have found evidence for such rotation-measure gradients in one-third to one-half of the 1 Jy BL Lac objects we have analyzed. We present and discuss these new results, together with some of their implications for our understanding of the parsec-scale jets of AGN.

The results of the VLA observations at sub-arcsec angular resolutions of 22 GHz H2O masers in the starburst galaxy M 82 and active galaxies NGC 4051 and NGC 6240 are presented. The VLA measurements enable one to explore the connection of these masers with active galactic nucleus (AGN)-activity. The masers in these galaxies have relatively low luminosity, which suggests that the origin of these H2O masers is due not to the nuclear activity of host galaxies but to the exotic extragalactic star formation.

A sample of the 6.7 GHz methanol maser sources found in the unbiased survey of the Galactic plane taken with the Toruń 32 m dish has been observed using the Mk II -- Ca baseline of MERLIN. The phase-referencing observations resulted in maser positional accuracies of 50 mas in RA and 100 mas in Dec for strong single-peak targets. Preliminary results are presented for the first set of sources. The coordinates of methanol sources are given. Comparison with infrared and radio continuum maps revealed that 7 out of 8 targets are associated with far infrared emission at 60 μ m, while 2 of them show 2.2 μ m emission and are accompanied by ultracompact H II regions seen in the 5 and/or 21 cm continuum.

In 1999 November we carried out S2 VLBI observations of several BL Lacertae objects and quasars at 1.66 GHz. Six antennas participated in the experiment (Bear Lakes, Svetloe, Pushchino, Noto, HartRAO and Seshan). The total intensity images of six sources (0420+022, 0420-014, 1308+326, 1345+125, 1803+784 and DA193) are presented and discussed together with their 1-22 GHz broad-band spectra taken by us on RATAN-600 close to the epoch of the VLBI experiment.