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1.
In this paper the southern cometary nebula GRV10 and its environment are investigated. The object is connected with a molecular cloud (its dimensions are ~4 pc). 12CO (1-0) observations toward GRV10 revealed the presence of two molecular outflows (a bipolar outflow), a red and a blue-shifted outflow, which coincide in position, indicating that they are moving along the line of sight in opposite directions. Near GRV10 a bright IR star, GRV10 IR, is discovered (near the southern edge of the nebula) and since its spectra and near IR colors favor it to be a Mira type star, a distance of ~4.4 kpc can be estimated. Star GRV10 IR appears connected with the IRAS point source IRAS 10406-6256. The grouping of stars (YSOs - young stellar objects) connected with GRV10 and embedded in a dark nebulosity is also discussed. This grouping is associated with the IRAS point source IRAS 10406-6253, which has FIR colors typical for embedded, not evolved, YSOs.  相似文献   

2.
Recent studies of the star formation region BBW 36 and associated molecular clouds are presented. The 12CO (1-0) observations, carried out with the 15-m SEST (Swedish-ESO) telescope (Cerro La Silla, Chile), revealed the existence of cloud a, connected with BBW 36 and of cloud b, having elongation in SE-NW direction. A red-shifted molecular outflow with velocity ∼+5 km/s (with respect to cloud a), having a direction parallel to the line of sight, was also observed. VLA observations showed the presence of a source VLA 2 at 3.6 cm with an elongation in the N-S direction. It is suggested that the VLA 2 source coincides with a dust disc (surrounding the object BBW 36). The star 3, which is one of the YSOs in the star-forming region BBW 36 and is connected with a bright comma-like nebula, can be the source of the molecular outflow. The star 3 has very high IR colors and is associated with an IRAS point source IRAS 07280-1829, which has IR colors, typical for an IRAS point source, connected with a water maser. On the 2MASS K image of BBW 36 we can see the existence of a bright nebula; a group of stars is embedded in that nebula, and among these stars there are stars with dust discs (or envelopes). On the 2MASS K image several spiral jets are also present, some of them with a condensation at the end. Published in Astrofizika, Vol. 51, No. 3, pp. 469–477 (August 2008).  相似文献   

3.
We present H α , [N  ii ] and [O  iii ] ground-based and HST archive images, VLA–A 3.6-cm continuum and H92 α emission-line data and high-resolution long-slit [N  ii ] spectra of the planetary nebula Hu 2-1. A large number of structural components are identified in the nebula: an outer bipolar and an inner shell, two pairs of collimated bipolar structures at different directions, monopolar bow-shock-like structures, and an extended equatorial structure within a halo. The formation of Hu 2-1 appears to be dominated by anisotropic mass ejection during the late-AGB stage of the progenitor and by variable, 'precessing' collimated bipolar outflows during the protoplanetary nebula and/or early planetary nebula phases. Different observational results strongly support the existence of a binary central star in Hu 2-1, among them (1) the observed point-symmetry of the bipolar lobes and inner shell, and the departures from axial symmetry of the bipolar lobes, (2) the off-centre position of the central star, (3) the detection of mass ejection towards the equatorial plane, and (4) the presence of 'precessing' collimated outflows. In addition, (5) an analysis of the kinematics shows that the systemic velocity of the bipolar outflows does not coincide with the systemic velocity of the bipolar shell. We propose that this velocity difference is a direct evidence of orbital motion of the ejection source in a binary system. From a deduced orbital velocity of ∼10 km s−1, a semimajor axis of ∼ 9–27 au and period of ∼ 25–80 yr are obtained, assuming a reasonable range of masses. These parameters are used to analyse the formation of Hu 2-1 within current scenarios of planetary nebulae with binary central stars.  相似文献   

4.
The first mapping observations of the bipolar HII region S106 in HCN J = 3 - 2 line were made by KOSMA submillimeter telescope in April, 2004. The results show that there is a bipolar outflow centered on the high-mass star S106 IRS4 and that the flat structure of molecular cloud core is perpendicular to the axis of the outflow. This image roughly corresponds to the optical image where a dark lane bisects the bipolar HII region. Together with the optical, infrared and radio data, we conclude that the central UC HII region and molecular outflow formed before the  相似文献   

5.
In this paper, we compute theoretically the flux density and the spectral index of the free–free radiation at radio wavelengths produced by shocks in the inner bipolar emission nebula called the little Homunculus around the star η Carinae. The little Homunculus is believed to have formed as a result of the minor eruption suffered by the star in the 1890s. In our model, we consider a simplified interacting stellar wind scenario where the post-outburst η Carinae wind collides with the eruptive outflow (both assumed to be bipolar with conical symmetry). As a result of the interaction, shock-wave structures are formed and generate the development of two polar caps moving in opposite directions. After ∼100 yr (i.e. at present times), the polar caps are located ±2.3 arcsec on each side of the star, and remain embedded within the larger bipolar Homunculus that extends from −8 to +8 arcsec along its major axis. Using observational estimates of the characteristics of the eruptive event of the 1890s, and of the ambient wind powered by η Carinae in the decades after the eruption ended, we study the evolution of the polar caps formed as a result of a sudden increase in the wind velocity and an instantaneous drop in the mass-loss rate (just after the eruption) at the injection radius. We found that the little Homunculus emits continuum radiation that can be detected at radio frequencies and that indeed represents an important contribution to the total free–free emission detected from the η Carinae nebula.  相似文献   

6.
Integral spectroscopy data for the nebula GM 1-29 and the source star PV Cep obtained on the 2.6-m telescope at the Byurakan Observatory are presented. The structure and kinematics of a collimated emission outflow directed along the axis of the nebula are studied. Changes in the radial velocity and intensity of the absorption component of the nebular Hα line are observed and studied; these are interpreted as a result of an anisotropy in the stellar wind at distances on the order of several stellar radii, where this absorption is formed. __________ Translated from Astrofizika, Vol. 51, No. 3, pp. 461–468 (August 2008).  相似文献   

7.
We present results from observations of H110 α recombination-line emission at 4.874 GHz and the related 4.8-GHz continuum emission towards the Carina nebula using the Australia Telescope Compact Array. These data provide information on the velocity, morphology and excitation parameters of the ionized gas associated with the two bright H  ii regions within the nebula, Car I and Car II. They are consistent with both Car I and Car II being expanding ionization fronts arising from the massive star clusters Trumpler 14 and Trumpler 16, respectively. The overall continuum emission distribution at 4.8 GHz is similar to that at lower frequencies. For Car I, two compact sources are revealed that are likely to be young H  ii regions associated with triggered star formation. These results provide the first evidence of ongoing star formation in the northern region of the nebula. A close association between Car I and the molecular gas is consistent with a scenario in which Car I is currently carving out a cavity within the northern molecular cloud. The complicated kinematics associated with Car II point to expansion from at least two different centres. All that is left of the molecular cloud in this region are clumps of dense gas and dust which are likely to be responsible for shaping the striking morphology of the Car II components.  相似文献   

8.
In this paper the results of multiwavelength investigation of an unusual nebular object SNO 85 are presented. In 2MASS images this object looks like a star with a jet. In DSS2 R image the end of the jet is connected with an interesting symmetric structure, consisting of arcs and loops. Such a structure is seen also in the opposite direction from the central star; it favors the existence of two opposite jets, which repeat the rotation and precession movements of the central star. The results of 12CO observations of the dark nebula LDN 288, connected with SNO 85, are also given. From these observations the following results were obtained: SNO 85 is situated in a dense condensation and the neighbor B type star GSC 0625400181 is surrounded by a hollow cavity. The velocity of the dark cloud is ∼2.5 km/s and its distance is estimated as (380–990) pc. The object SNO 85 itself is associated with an IRAS point source IRAS 17547-1832, the infrared colors of this source are typical for a non-evolved source embedded in the dense dark cloud. This region is perhaps a star formation one because there is also another star with a straight jet in the vicinity of B type star GSC 0625400181. Published in Astrofizika, Vol. 49, No. 4, pp. 621–629 (August 2006).  相似文献   

9.
Circumstellar structure of RU Lupi down to au scales   总被引：1，自引：0，他引：1  
We have used the technique of spectro-astrometry to study the milliarcsecond scale structure of the emission lines in the T Tauri star RU Lupi. The wings of the H α emission are found to be displaced from the star towards the south-west (blue wing) and north-east (red wing) with angular scales of 20–30 mas. This structure is consistent with a bipolar outflow from the star. From a study of the variability of the intensity and position spectra, we argue that a combination of magnetically driven bipolar outflow and accreting gas contributes to the H α emission. On the other hand, the [O  i ] and [S  ii ] emission are displaced from the star to the south-west but at much larger distances than the H α , hundreds of milliarcseconds for the high-velocity component (HVC) and down to 30 mas for the low-velocity components (LVCs). The presence of both redshifted and blueshifted outflows in H α but only a blueshifted outflow in the forbidden lines can be explained if the disc obscures the redshifted forbidden line outflow, but a disc gap with outer radius 3–4 au allows the redshifted H α to be seen. This gap could be induced by an unseen companion.  相似文献   

10.
We have undertaken echelle spectroscopy and narrow-band line imaging of the bipolar planetary nebula M 1-8. This has permitted us to map the outflow in [N  ii ]λλ 6548+6583 Å, Hα, and in the v = 1–0 S(1) transition of H2 at λ 2.122 μm. It has also permitted us to acquire high-resolution spectra for [N  ii ]λ 6583 Å, Hα and He  ii λ 6560 Å. Our observations support the results of a previous 2MASS analysis by two of the authors (J. P. Phillips and G. Ramos-Larios), and confirm that there is strong H2 emission outside of the ionized zone, as well as along the major axis of the outflow. Finally, we have investigated the spatial structure of the outflow in low and high excitation lines, and noted evidence for strong ionization stratification within the envelope of the source. We also note that major axis spectra show asymmetries attributable to outflow along the lobes, oriented at an angle i ∼ 35°–40° to the line of sight. Asymmetries along the minor axis, by contrast, appear to be associated with the central collimating disc, and may be interpretable in terms of asymmetries in disc structure, or rotation at an angular velocity of Ω∼ 1.4 10−12 rad s−1. If the disc arises due to common-envelope evolution, then it seems that angular momentum constraints must be relatively tight, and can only be satisfied given fairly extreme physical assumptions (such as low disc mass, high primary star mass, a low distance to the source and so forth).  相似文献   

11.
M 1–92 is a very well studied bipolar pPN that can be considered an archetype of this type of sources; it shows a clear axial symmetry, along with the kinematics characteristic of this class of envelopes around post-AGB stars. We performed sub-arcsecond resolution observations of the J=2–1 rotational line of 13CO in M 1–92 with the new extended configurations of the IRAM Plateau de Bure interferometer, for studying the morphology and velocity field of the molecular gas better in the nebula, particularly in its central parts. We found that the equatorial structure dividing the two lobes is a thin flat disk, which expands radially with a velocity proportional to the distance to the central stellar system. The kinetic age of this equatorial flow is very similar to that measured in the two lobes, suggesting that the whole structure was formed as a result of a single event some 1200 yr ago, after which the nebula reached an expansion velocity field with axial symmetry. The small widths and velocity dispersion in the gas forming the lobe walls confirm that the acceleration responsible for the nebular shape could not last more than 100–120 yr. In view of the similarity to η Car, we speculate on the possibility that the whole nebula was formed as a result of a magneto-rotational explosion in a common-envelope system. The study of the possible importance of this mechanism in the context of global PNe and pPNe reshaping should be one on the fields in which future ALMA observations will make a crucial contribution. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).  相似文献   

12.
The infrared star cluster RCW 38 IR Cluster, which is also a massive star-forming region, is investigated. The results of observations with the SEST (Cerro La Silla, Chile) telescope on the 2.6-mm 12CO spectral line and with SIMBA on the 1.2-mm continuum are given. The 12CO observations revealed the existence of several molecular clouds, two of which (clouds 1 and 2) are connected with the object RCW 38 IR Cluster. Cloud 1 is a massive cloud, which has a depression in which the investigated object is embedded. It is not excluded that the depression was formed by the wind and/or emission from the young bright stars belonging to the star cluster. Rotation of cloud 2, around the axis having SE-NW direction, with an angular velocity ω = 4.6 · 10−14 s−1 is also found. A red-shifted outflow with velocity ∼+5.6 km/s, in the SE direction and perpendicular to the elongation of cloud 2 has also been found. The investigated cluster is associated with an IR point source IRAS 08573-4718, which has IR colors typical for a non-evolved embedded (in the cloud) stellar object. The cluster is also connected with a water maser. The SIMBA image shows the existence of a central bright condensation, coinciding with the cluster itself, and two extensions. One of these extensions (the one with SW-NE direction) coincides, both in place and shape, with cloud 2, so that the possibility that this extension might also be rotating like cloud 2 is not excluded. In the vicinity of these extensions there are condensations resembling HH objects. Published in Astrofizika, Vol. 51, No. 1, pp. 29–40 (February 2008).  相似文献   

13.
The physical nature and evolution of the Orion Nebula has begun to be revealed by calibrated emission line images and high resolution spectroscopy. We review the evidence that the nebula is a thin wall of emission on the near side of the Orion Molecular Cloud and that its separation from the dominant ionizing star is about 0.3 pc. The density of the nebula decreases rapidly away from the ionization front and the ionized gas is moving at 8 km s–1 away from the front. A three dimensional model of the surface is presented and its peaks and valleys interpreted as due to irregularities in the density of the molecular cloud. The front is moving rapidly into the molecular cloud, so that objects previously shielded from ionization are continuously being revealed. Recent Hubble Space Telescope images are reviewed and they indicate that protoplanetary disks around pre-main sequence stars are both common and rendered visible by ionization and projection against the bright nebula. A large body of velocity data is discussed and it is seen that Kolmogorov type turbulence seems to only apply to material in the ionization front and the statistical fluctuations become less correlated away from the front.  相似文献   

14.
Spatially resolved, broad Hα line profiles from both the luminous blue variable star ε Carinae (ε Car) and the surrounding filamentary Car II ('Keyhole') nebula, where they have been scattered and reflected by dust, have been observed periodically from 1985 to 1997. The Hα line profiles from ε Car in this 12-yr period show some, albeit not dramatic, changes. The sharp and deep P Cygni-type absorption feature that was observed first in 1985 in the broad, scattered/reflected profiles from the surrounding Keyhole nebula is not present in any of the direct ε Car profiles. This distinctive feature is now shown to be spatially variable over the Keyhole nebula and most prominent along the direction of the axis of the bipolar Homunculus nebula at PA 132°. No evidence of any temporal variability of this sharp feature has been found in 12 yr of monitoring, even from the most well-defined scattering/reflecting cloud along PA 132°.
It is concluded that a 46°-wide cone of light from ε Car is relatively unobscured along the axis of the Homunculus nebula and that this must be the consequence of a dense torus close to the star.  相似文献   

15.
Observations obtained with the Midcourse Space Experiment (MSX) satellite reveal for the first time the complex mid-infrared morphology of the entire Carina Nebula (NGC 3372). On the largest size scale of approximately 100 pc, the thermal infrared emission from the giant H ii region delineates one coherent structure: a (somewhat distorted) bipolar nebula with the major axis perpendicular to the Galactic plane. The Carina Nebula is usually described as an evolved H ii region that is no longer actively forming stars, clearing away the last vestiges of its natal molecular cloud. However, the MSX observations presented here reveal numerous embedded infrared sources that are good candidates for sites of current star formation. Several compact infrared sources are located at the heads of dust pillars or in dark globules behind ionization fronts. Because their morphology suggests a strong interaction with the peculiar collection of massive stars in the nebula, we speculate that these new infrared sources may be sites of triggered star formation in NGC 3372.  相似文献   

16.
During the period 1979–1999, we investigated the hyperfine structure of the H2O supermaser region located in the core of the molecular cloud OMC-1 in Orion KL. The angular resolution is 0.1 mas, which corresponds to 0.045 AU. The detected structure, which consists of a central object, an accretion disk, a bipolar outflow, and an envelope, corresponds to the initial formation stage of a low-mass star. The accretion disk is at the stage of separation into groups of concentric rings. The bipolar outflow is a neutral, highly collimated jet of accreted material that includes H2O molecules and dust grains in the icy envelope. The injector is a bright compact source with a size <0.05 AU and a brightness temperature Tb≈1017 K. The velocity of the bipolar outflow is v≈10 km s?1. The rotation velocity of the jet is vrot≈1.5 km s?1. The jet has the shape of a conical helix due to the precession of the rotation axis. Occasionally, dense blobs (comet-shaped bullets) are ejected. The envelope amplifies the radio emission from the structures in a ～0.5 km s?1 maser window band with velocities v≈7.65 km s?1 by more than two orders of magnitude.  相似文献   

17.
We report the discovery of the first probable Galactic [WN] central star of a planetary nebula (CSPN). The planetary nebula candidate was found during our systematic scans of the AAO/UKST Hα Survey of the Milky Way. Subsequent confirmatory spectroscopy of the nebula and central star reveals the remarkable nature of this object. The nebular spectrum shows emission lines with large expansion velocities exceeding 150 km s−1, suggesting that perhaps the object is not a conventional planetary nebula. The central star itself is very red and is identified as being of the [WN] class, which makes it unique in the Galaxy. A large body of supplementary observational data supports the hypothesis that this object is indeed a planetary nebula and not a Population I Wolf–Rayet star with a ring nebula.  相似文献   

18.
The T Tauri variable V1331 Cyg is characterized by an intensive emission spectrum, by signatures of a high rate of mass loss, and also by presence of a circular reflection nebula. According to these characteristics, the star can be considered as a possible pre-FUor star. Up to the present the photospheric spectrum of the star has not been recorded. In this work we analyze the high-resolution spectra of V1331 Cyg that were obtained by G.H. Herbig with the HIRES spectrograph at the Keck-1 telescope in 2004 and 2007. For the first time the numerous photospheric lines of the star have been detected and the spectral class has been estimated, viz., G7-K0 IV. It is revealed that the projection of the rotation velocity is lower than the width of instrumental profile (vsini < 6 km/s); this means that the angle between the stellar axis of rotation and the line of sight is small. The radial velocity of the star derived from the photospheric lines is RV = ?15.0 ± 0.3 km/s. The difference in radial velocities for 2004 and 2007 is lower than the measurement error. The photospheric spectrum is veiled considerably, but the amount of veiling is not the same in different lines. This depends on the line strength in the template spectrum of the G7 IV star: in the weakest lines (EW = 5–10 mÅ in the template spectrum) VF ≈ 1 and it increases up to 4–5 in stronger lines. The Hα and Hβ lines demonstrate classical P Cyg profiles, which testifies to an intensive wind with a maximal velocity of about 400 km/s. In addition, the emission lines of Fe II, Mg I and K I and of several other elements are accompanied by a narrow blue-shifted absorption at ?150...?250 km/s. The emission spectrum of V1331 Cyg is rich in the narrow (FWHM = 30–50 km/s) lines of neutral and ionized metals showing the excitation temperature T exc = 3800 ± 300 K. The stellar mass M* ≈ 2.8M ⊙ and radius R* ≈ 5R ⊙ are estimated.  相似文献   

19.
使用4米毫米波望远镜和中澳合作研制的高分辨率声光频谱仪完成了暗星云DC337.7—4.0的CO分子J=1-0谱线的成图观测。数据处理包含有消干扰步骤。获得云的平均辐射温度为7.3K,平均视向速度3.7km/s,平均谱线半宽1.1km/s。观测结果没显示出云中有恒星形成活动的迹象。  相似文献   

20.
We study the bending of jets in binary stellar systems. A compact companion accretes mass from the slow wind of the mass-losing primary star, forms an accretion disc and blows two opposite jets. These fast jets are bent by the slow wind. Disregarding the orbital motion, we find the dependence of the bending angle on the properties of the slow wind and the jets. Bending of jets is observed in planetary nebulae which are thought to be the descendants of interacting binary stars. For example, in some of these planetary nebulae, the two bubbles (lobes) which are inflated by the two opposite jets are displaced to the same side of the symmetry axis of the nebula. Similar displacements are observed in bubble pairs in the centre of some clusters and groups of galaxies. We compare the bending of jets in binary stellar systems with that in clusters of galaxies.  相似文献   

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