Interaction of the supernova remnant S 147 with the ambient interstellar gas

Based on RATAN-600 21-cm H I line observations with an angular resolution of 2.4', we studied the neutral-hydrogen distribution in the region of the supernova remnant (SNR) S 147 (G180.0-1.7). We detected a rotating shell of neutral gas immediately adjacent to the SNR that is expanding at a velocity of 20 km s^?1. The H I shell is less distinct in the southeastern part and at negative radial velocities. The outer shell diameter is 90 pc; the H I mass in the shell is 2.2 × 10⁴M_⊙. These data allowed us to estimate the SNR age, 6.5×10⁵ yr, and the initial explosion energy, 2.2×10⁵¹ erg.     

Interaction of the supernova remnant HB3 with the ambient interstellar gas

The well-known shell supernova remnant (SNR) HB3 is part of a feature-rich star-forming region together with the nebulae W3, W4, and W5. We study the HI structure around this SNR using five RATAN-600 drift curves obtained at a wavelength of 21 cm with an angular resolution of 2′ in one coordinate over the radial-velocity range ?183 to +60 km s^?1 in a wider region of the sky and with a higher sensitivity than in previous works by other authors. The spatial-kinematic distribution of HI features around the SNR clearly shows two concentric expanding shells of gas that surround the SNR and coincide with it in all three coordinates (α, δ, and V). The outer shell has a radius of 133 pc, a thickness of 24 pc, and an expansion velocity of 48 km s^?1. The mass of the gas in it is ≈2.3 × 10⁵M_⊙. For the inner shell, these parameters are 78 pc, 36 pc, 24 km s^{? 1}, and 0.9 × 10⁵M_⊙, respectively. The inner shell is immediately adjacent to the SNR. Assuming that the outer shell was produced by the stellar wind and the inner shell arose from the shock wave of the SNR proper, we estimated the age of the outer shell, ≈1.7 × 10⁶ yr, and the mechanical luminosity of the stellar wind, 1.5 × 10³⁸ erg s^?1. The inner shell has an age of ≈10⁶ yr and corresponds to a total supernova explosion energy of ≈10⁵² erg.     

Kinematic parameters of young subsystems and the galactic rotation curve

We analyze the space velocities of blue supergiants, long-period Cepheids, and young open star clusters (OSCs), as well as the H I and H II radial-velocity fields by the maximum-likelihood method. The distance scales of the objects are matched both by comparing the first derivatives of the angular velocity Ω′ determined separately from radial velocities and proper motions and by the statistical-parallax method. The former method yields a short distance scale (for R₀=7.5 kpc, the assumed distances should be increased by 4%), whereas the latter method yields a long distance scale (for R₀=8.5 kpc, the assumed distances should be increased by 16%). We cannot choose between these two methods. Similarly, the distance scale of blue supergiants should be shortened by 9% and lengthened by 3%, respectively. The H II distance scale is matched with the distance scale of Cepheids and OSCs by comparing the derivatives Ω′ determined for H II from radial velocities and for Cepheids and OSCs from space velocities. As a result, the distances to H II regions should be increased by 5% in the short distance scale. We constructed the Galactic rotation curve in the Galactocentric distance range 2–14 kpc from the radial velocities of all objects with allowance for the difference between the residual-velocity distributions. The axial ratio of the Cepheid+OSC velocity ellipsoid is well described by the Lindblad relation, while σ_u≈σ_v for gas. The following rotation-curve parameters were obtained: Ω₀=(27.5±1.4) km s^?1 kpc^?1 and A=(17.1±0.5) km s^?1 kpc^?1 for the short distance scale (R₀=7.5 kpc); and Ω₀=(26.6±1.4) km s^?1 kpc^?1 and A=(15.4±0.5) km s^?1 kpc^?1 for the long distance scale (R₀=8.5 kpc). We propose a new method for determining the angular velocity Ω₀ from stellar radial velocities alone by using the Lindblad relation. Good agreement between the inferred Ω₀ and our calculations based on space velocities suggests that the Lindblad relation holds throughout the entire sample volume. Our analysis of the heliocentric velocities for samples of young objects reveals noticeable streaming motions (with a velocity lag of ～7 km s^?1 relative to the LSR), whereas a direct computation of the perturbation amplitudes in terms of the linear density-wave theory yields a small amplitude for the tangential perturbations.     

Cepheid kinematics and the Galactic warp

The space velocities of 200 long-period (P>5 days) classical Cepheids with known proper motions and line-of-sight velocities whose distances were estimated from the period-luminosity relation have been analyzed. The linear Ogorodnikov-Milne model has been applied, with the Galactic rotation having been excluded from the observed velocities in advance. Two significant gradients have been found in the Cepheid velocities, ?W/?Y = ?2.1 ± 0.7 km s^?1 kpc^?1 and ?V/?Z = 27 ± 10 km s^?1 kpc^?1. In such a case, the angular velocity of solid-body rotation around the Galactic X axis directed to the Galactic center is ?15 ± 5 km s^?1 kpc^?1.     

On a new cluster of H<Subscript>2</Subscript>O maser spots in the source ON2

We present the results of our observations of the H₂O maser emission toward the complex source ON2 associated with an active star-forming region. The observations were performed in a wide range of radial velocities, from ?75 to 90 km s^?1. We have detected an emission with flux densities of 9.2, 4, and 26 Jy at radial velocities of ?33.5, ?24.4, and ?18.8 km s^?1, respectively, at which no emission has been observed previously. The detected emission is most likely associated with a hitherto unknown cluster of maser spots located between the northern (N) and southern (S) components of the source ON2 (closer to the northern one). This cluster may be associated with one of the three CO molecular outflows in the ON2 region. We have also detected an emission at ?22 and ?14.5 km s^?1 in N and at 12.6 km s^?1 in S, which has extended significantly the velocity ranges of the maser emission in these sources and allowed their models to be improved.     

The structure of Galactic gas at high latitudes: The southern polar cap

We analyze the angular structure of the 21-cm interstellar neutral hydrogen emission at six and seven declinations in the northern (published previously) and southern polar caps of the Galaxy (Galactic latitudes from ?40° to ?90°), respectively, with an extent of 90° in right ascension. The RATAN-600 radio telescope has a beam width averaged over these regions of 2.′0×30′. One-dimensional power spectra for the angular distribution of interstellar neutral hydrogen emission were computed in each 6.3-km s^?1-wide spectral channel by using the standard Fast Fourier Transform (FFT) code and were smoothed over 1^h in right ascension. The Galactic latitude dependence of the mean parameters for the sky distribution of H I line emission at high latitudes was found to correspond to the distribution of gas in the form of a flat layer only in the northern region, while in the southern cap, the gas distribution is much less regular. In addition, the mean H I radial velocities are negative everywhere (?3.7±3.0 km s^?1 in the north and ?6.0±2.4 km s^?1 in the south). The power spectra of the angular fluctuations in the range of angular periods from 10′ to 6° appear as power laws. However, the spectral indices change greatly over the sky: from ?3 to ?1.2; on average, as the Galactic latitude increases and the H I column density decreases, the fluctuation spectrum of the interstellar gas emission becomes flatter. In the northern polar region, this behavior is much more pronounced, which probably stems from the fact that the gas column density in the south is generally a factor of 2 or 3 higher than that in the north. Therefore, the spectra are, on average, also steeper in the south, but the dependence on Galactic latitude is weaker. Using simulations, we show that the observed power-law spectrum of the H I emission distribution can be obtained in terms of not only a turbulent, but also a cloud model of interstellar gas if we use our previous spectra of the diameters and masses of H I clouds.     

Estimation of the galactic spiral pattern speed from Cepheids

To study the peculiarities of the Galactic spiral density wave, we have analyzed the space velocities of Galactic Cepheids with propermotions from the Hipparcos catalog and line-of-sight velocities from various sources. First, based on the entire sample of 185 stars and taking R ₀ = 8 kpc, we have found the components of the peculiar solar velocity (u _⊙, v _⊙) = (7.6, 11.6) ± (0.8, 1.1) km s^?1, the angular velocity of Galactic rotation Ω₀ = 27.5 ± 0.5 km s^?1 kpc^?1 and its derivatives Ω′₀ = ?4.12 ± 0.10 km s^?1 kpc^?2 and Ω″₀ = 0.85 ± 0.07 km s^?1 kpc^?3, the amplitudes of the velocity perturbations in the spiral density wave f _R = ?6.8 ± 0.7 and f _θ = 3.3 ± 0.5 km s^?1, the pitch angle of a two-armed spiral pattern (m = 2) i = ?4.6° ± 0.1° (which corresponds to a wavelength λ = 2.0 ± 0.1 kpc), and the phase of the Sun in the spiral density wave χ_⊙ = ?193° ± 5°. The phase χ_⊙ has been found to change noticeably with the mean age of the sample. Having analyzed these phase shifts, we have determined the mean value of the angular velocity difference Ω _p ? Ω, which depends significantly on the calibrations used to estimate the individual ages of Cepheids. When estimating the ages of Cepheids based on Efremov’s calibration, we have found |Ω _p ? Ω₀| = 10 ± 1_stat ± 3_syst km s^?1 kpc^?1. The ratio of the radial component of the gravitational force produced by the spiral arms to the total gravitational force of the Galaxy has been estimated to be f _r0 = 0.04 ± 0.01.     

Kinematic parameters of the galactic spiral pattern from data on open star clusters and OB stars

Data on the positions, radial velocities, and proper motions of open star clusters and OB stars are used to obtain the rotation curve of the Galaxy fitted by a polynomial in inverse powers of the distances from the Galactic rotation axis. We determine the locations of the corotation region and the inner and outer Lindblad resonances using a previously estimated pattern speed. Based on data for objects of the Carina-Sagittarius and Orion arms, we have determined the distortion amplitudes of the velocity field of the Galactic disk, ?_R = ?3.97±4.79 km s^?1 and f_θ=+13.27±2.57 km s^?1.     

Polarization of the H2O maser emission from Orion KL at epoch 2011.7

Polarization observations of the H₂O maser emission at 1.35 cm from the active region Orion KL were carried out at epoch 2011.7 on the Svetloe-Zelenchukskaya radio interferometer. The observational data have been processed on the correlator of the QUASAR network. Fragments of the structure have been identified; the line velocities and profile widths and the emission polarization have been determined. The component at the radial velocity V = 7.0 km s^?1 has been taken as a reference one. Its effective size in the Gaussian approximation is 1.5 mas, the axial ratio is Major/Minor = 3.3, and the orientation is PA = 11°. The component V = 7.6 km s^?1 corresponds to a bipolar outflow with an effective size of 6.2 mas, the axial ratio is Major/Minor = 5.3, and the orientation ?32°. The bipolar outflow is 10 mas away from the reference feature in the direction of 173°. The longitudinal velocity components of the NW and SE parts of the bipolar outflow in the local standard of rest are +0.15 and ?0.15 km s^?1, respectively. The degrees of polarization of the emission from the reference feature (7.0 km s^?1) and the bipolar outflow are m = 39 and 52%, respectively. The difference in polarization orientations of both components ?? _?? does not exceed 3°.     

Polarized emission from the ejector in Orion KL

The superfine structure of the active region in Orion KL has been investigated in the H₂O maser line at two epochs, December 23, 1998, and April 24, 1999, with an angular resolution as high as 0.01 mas. A bright central source, a bipolar outflow ejector with two nozzles spaced 0.008 mas apart, has been identified. The impact of the ejected flows causes precession of the rotation axis and gives rise to a jet structure in the shape of diverging helixes of opposite signs. The longitudinal velocities of the flows differ by 0.12 km s^?1. The flow emission at the exit from the nozzles is linearly polarized and oriented at an angle of 22° relative to the rotation axis or parallel to the flow velocities. Their brightness temperature exceeds T _b > 10¹⁸ K. The width of the emission line profiles is 0.43 km s^?1, their relative shift is ±0.06 km s^?1, and the orientations of the polarization planes differ by 45°, which determines the extraordinary rotation of the polarization plane, 25°/km s^?1.     

Black hole at the center of the globular cluster M15: Estimation of the mass and specific angular momentum

Using the technique of determining the sum of the masses of double stars, we have estimated the mass of the central object in the globular cluster M15. The radial velocities of stars at distances up to 1″ from the cluster center have been used. The parameters of circular orbits and the space velocities of 11 selected field stars relative to the cluster center have been determined from the calculated velocity dispersions with respect to the mean radial velocity. Based on the mean space velocity V, 14 km s^?1, and using the energy integral, we have estimated the mass of the central object to be within the range (1?9) × 10³ M _⊙. We have estimated the kinetic power of the outflow of matter from the region surrounding the black hole in M15 and the specific angular momentum of the black hole.     

Corrections for the Lutz-Kelker bias for Galactic masers

Based on published data, we have collected information about Galactic maser sources with measured distances. In particular, 44 Galactic maser sources located in star-forming regions have trigonometric parallaxes, proper motions, and radial velocities. In addition, ten more radio sources with incomplete information are known, but their parallaxes have been measured with a high accuracy. For all 54 sources, we have calculated the corrections for the well-known Lutz-Kelker bias. Based on a sample of 44 sources, we have refined the parameters of the Galactic rotation curve. Thus, at R ₀ = 8kpc, the peculiar velocity components for the Sun are (U _⊙, V _⊙, W _⊙) = (7.5, 17.6, 8.4) ± (1.2, 1.2, 1.2) km s^?1 and the angular velocity components are ω ₀ = ?28.7 ± 0.5 km s^?1 kpc^?1, ω ₀′ = +4.17 ± 0.10 km s^?1 kpc^?2, and ω₀″ = ?0.87 ± 0.06 km s^?1 kpc^?3. The corresponding Oort constants are A = 16.7 ± 0.6 km s^?1 kpc^?1 and B = ?12.0 ± 1.0 km s^?1 kpc^?1; the circular rotation velocity of the solar neighborhood around the Galactic center is V ₀ = 230 ± 16 km s^?1. We have found that the corrections for the Lutz-Kelker bias affect the determination of the angular velocity ω ₀ most strongly; their effect on the remaining parameters is statistically insignificant. Within themodel of a two-armed spiral pattern, we have determined the pattern pitch angle $i = - 6_.^ \circ 5$ and the phase of the Sun in the spiral wave χ ₀ = 150°.     

New in the optical spectrum and kinematic state of the atmosphere of the variable V1027 Cyg (=IRAS 20004+2955)

Based on our high-spectral-resolution observations performed with the NES echelle spectrograph of the 6-m telescope, we have studied the peculiarities of the spectrum and the velocity field in the atmosphere and envelope of the cool supergiant V1027 Cyg, the optical counterpart of the infrared source IRAS 20004+2955. A splitting of the cores of strong absorptions of metals and their ions (Si II, Ni I, Ti I, Ti II, Sc II, Cr I, Fe I, Fe II, BaII) has been detected in the stellar spectrum for the first time. The broad profile of these lines contains a stable weak emission in the core whose position may be considered as the systematic velocity V _sys = 5.5 km s^?1. Small radial velocity variations with an amplitude of 5–6 km s^?1 due to pulsations have been revealed by symmetric low- and moderate-intensity absorptions. A long-wavelength shift of the Hα profile due to line core distortion is observed in the stellar spectrum. Numerous weak CN molecular lines and the KI 7696 Å line with a P Cyg profile have been identified in the red spectral region. The coincidence of the radial velocities measured from symmetric metal absorptions and CN lines suggests that the CN spectrum is formed in the stellar atmosphere. We have identified numerous diffuse interstellar bands (DIBs) whose positions in the spectrum, V _r (DIBs) = ?12.0 km s^?1, correspond to the velocity of the interstellar medium in the Local Arm of the Galaxy.     

The supernova remnant G78.2+2.1: New optical and X-ray observations

New optical and X-ray observations of the supernova remnant (SNR) G78.2+2.1 are presented. CCD Hα observations with a Fabry-Perot interferometer attached to the 125-cm reflector at the Crimean Station of the Sternberg Astronomical Institute are used to obtain the radial-velocity field toward the SNR and in its vicinity. The brightness distribution and X-ray spectrum of the SNR are obtained from archival ROSAT and ASCA X-ray data. The X-ray image of G78.2+2.1 exhibits a shell structure (ΔR/R?0.3) and is generally similar to its radio image; a comparison with the radio map at ν=1.4 GHz constructed from archival VLA data reveals the coincidence of features on scales of several arcminutes at the eastern boundary of G78.2+2.1. Weak X-ray emission (an outer shell or a halo of size ?2°) has been identified for the first time far outside G78.2+2.1. The X-ray emission from G78.2+2.1 is shown to characterize a young adiabatic SNR [M _X-ray ? 100 M _⊙, V _s?10³km s^?1, t?(5–6)×10³ years], which probably expands inside the cavity swept up by the progenitor's stellar wind. Searches for the corresponding radio structure are required to elucidate the nature of the outer X-ray shell or halo.     

Galactic kinematics from data on open star clusters from the MWSC catalogue

Open star clusters from the MWSC (Milky Way Star Clusters) catalogue have been used to determine the Galactic rotation parameters. The circular rotation velocity of the solar neighborhood around the Galactic center has been found from data on more than 2000 clusters of various ages to be V ₀ = 236 ± 6 km s^?1 for the adopted Galactocentric distance of the Sun R ₀ = 8.3 ± 0.2 kpc. The derived angular velocity parameters are Ω ₀ = 28.48 ± 0.36 km s^?1 kpc^?1, Ω’₀ = ?3.50 ± 0.08 km s^?1 kpc_?2, and Ω″₀ = 0.331 ± 0.037 km s^?1 kpc^?3. The influence of the spiral density wave has been detected only in the sample of clusters younger than 50 Myr. For these clusters the amplitudes of the tangential and radial velocity perturbations are f ^θ = 5.6 ± 1.6 km s^?1 and f _R = 7.7 ± 1.4 km s^?1, respectively; the perturbation wavelengths are λ _θ = 2.6 ± 0.5 kpc (i _θ = ^?11? ± 2?) and λ _R = 2.1 ± 0.5 kpc (i _R = ?9? ± 2?) for the adopted four-armed model (m = 4). The Sun’s phase in the spiral density wave is (χ_⊙)_θ = ?62? ± 9? and (χ_⊙)_R = ?85? ± 10? from the residual tangential and radial velocities, respectively.     

Surveying the Local Supercluster Plane

We investigate the distribution and velocity field of galaxies situated in a band of 100 by 20 degrees centered on M87 and oriented along the Local supercluster plane. Our sample amounts 2158 galaxies with radial velocities less than 2000 km s^?1. Of them, 1119 galaxies (52%) have distance and peculiar velocity estimates. About 3/4 of early-type galaxies are concentrated within the Virgo cluster core, most of the late-type galaxies in the band locate outside the virial radius. Distribution of gas-rich dwarfs with M_HI >M_* looks to be insensitive to the Virgo cluster presence. Among 50 galaxy groups in the equatorial supercluster band 6 groups have peculiar velocities about 500–1000 km s^?1 comparable with virial motions in rich clusters. The most cryptic case is a flock of nearly 30 galaxies around NGC4278 (Coma I cloud), moving to us with the mean peculiar velocity of ?840 km s^?1. This cloud (or filament?) resides at a distance of 16.1 Mpc from us and approximately 5 Mpc away from the Virgo center. Galaxies around Virgo cluster exhibit Virgocentric infall with an amplitude of about 500 km s^?1. Assuming the spherically symmetric radial infall, we estimate the radius of the zero-velocity surface to be R₀ = (7.0±0.3) Mpc that yields the total mass of Virgo cluster to be (7.4 ± 0.9)× 10¹⁴M_⊙ in tight agreement with its virial mass estimates. We conclude that the Virgo outskirts does not contain significant amounts of dark mater beyond its virial core.     

Galactic rotation curve and spiral density wave parameters from 73 masers

Based on kinematic data on masers with known trigonometric parallaxes and measurements of the velocities of HI clouds at tangential points in the inner Galaxy, we have refined the parameters of the Allen-Santillan model Galactic potential and constructed the Galactic rotation curve in a wide range of Galactocentric distances, from 0 to 20 kpc. The circular rotation velocity of the Sun for the adopted Galactocentric distance R ₀ = 8 kpc is V ₀ = 239 ± 16 km s^?1. We have obtained the series of residual tangential, ΔV _θ , and radial, V _R , velocities for 73 masers. Based on these series, we have determined the parameters of the Galactic spiral density wave satisfying the linear Lin-Shu model using the method of periodogram analysis that we proposed previously. The tangential and radial perturbation amplitudes are f _θ = 7.0±1.2 km s^?1 and f _R = 7.8±0.7 km s^?1, respectively, the perturbation wave length is λ = 2.3±0.4 kpc, and the pitch angle of the spiral pattern in a two-armed model is i = ?5.2° ±0.7°. The phase of the Sun ζ _⊙ in the spiral density wave is ?50° ± 15° and ?160° ± 15° from the residual tangential and radial velocities, respectively.     

Active star-forming region in Orion KL, epoch 2012

Polarization measurements of the H₂O maser emission from the active region in Orion KL were carried out at epoch 2011?C2012 on the Svetloe-Zelenchukskaya radio interferometer. The bipolar outflow structure and polarized emission parameters have been determined. The emission from the components at v = 7.6 and 7.0 km s^?1 dominates in the line profile; the relative contribution of the former component has increased. The velocity of the bipolar outflow ejector region is almost equal to that of the local standard of rest v _LSR = 7.65 km s^?1, while the velocity of the remote component is v = 7.0 km s^?1. The emission from the bipolar outflow is observed at a distance up to 11 mas from the ejector. Its diameter does not exceed 0.3 mas. The outflow orientation in the plane of the sky is ?37°. The outflow velocity components along the line of sight differ by ??v = 0.3 km s^?1. The polarization levels of the bipolar outflow and the remote component reach m = 62 and 39%, respectively.     

New observations of the pulsar wind nebula in the supernova remnant CTB 80

We investigated the kinematics of the pulsar wind nebula (PWN) in the old supernova remnant CTB 80 using the Fabry-Perot interferometer of the 6-m Special Astrophysical Observatory telescope. In addition to the previously known expansion of the system of bright filaments with a velocity of 100–200 km s^?1, we detected weak high-velocity features in the Hα line at least up to velocities of 400–450 km s^?1. We analyzed the morphology of the PWN in the Hα, [S II], and [O III] lines using HST archival data and discuss its nature. The shape of the central filamentary shell, which is determined by the emission in the [O III] line and in the radio continuum, is shown to be consistent with the bow-shock model for a significant (about 60°) inclination of the pulsar’s velocity vector to the plane of the sky. In this case, the space velocity of the pulsar is twice as high as its tangential velocity, i.e., it reaches ?500 km s^?1, and PSR B1951+32 is the first pulsar whose radial velocity about 40 km s^?1 has been estimated from PWN observations. The shell-like Hα-structures outside the bow shock front in the east and the west could be associated with both the pulsar’s jets and the pulsar wind breakthrough due to the layered structure of the extended CTB 80 shell.