共查询到20条相似文献，搜索用时 31 毫秒
1.
L. V. Shalyapina A. V. Moiseev V. A. Yakovleva V. A. Hagen-Thorn A. N. Burenkov 《Astronomy Letters》2004,30(1):1-13
We present our observations of the pair of interacting galaxies NGC 6285/86 carried out with the 6-m Special Astrophysical Observatory (SAO) telescope using 1D and 2D spectroscopy. The observations of NGC 6286 with a long-slit spectrograph (UAGS) near the Hα 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 close radial velocities of the pair and the wide (5′×5′) field of view of the scanning Fabry-Perot interferometer (IFP) allowed us to simultaneously obtain images in the Hα and [N II]λ6583 lines and in the continuum, as well as to construct the radial velocity fields and to map the distribution of the [N II]λ6583/Hα ratio for both galaxies. Based on all these data, we studied the gas kinematics in the galaxies, constructed their rotation curves, and estimated their masses (2 × 1011M⊙ for NGC 6286 and 1.2 × 1010M⊙ for NGC 6285). We found no evidence of gas rotation around the major axis of NGC 6286, 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 of superwind galaxies. The large [N II]λ6583/Hα 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 between the two galaxies was probably responsible for the starburst and the bipolar outflow of hot gas from the central region of the disk. 相似文献
2.
Spectrophotometric monitoring of the nucleus of the galaxy NGC 4151 was carried out for 13 nights from 23 January to 10 June 1988 in the wavelength range 4000–7000 Å. A 0.5-m meniscus telescope, a slitless spectrograph, and the highly sensitive, digital television complex of the Crimean Astrophysical Observatory were used. The exposure time was 150–300 sec, while the time resolution, allowing for recording spectra of the comparison star, was about 30 min. The results show that the galaxy’s nucleus was in a deep minimum. On a time scale of days to months, the synthetic magnitudes Vsyn and the fluxes Fcon in the continuum had a similar time dependence; the amplitude of variability reached 15% in January-April, while a brightness increase of 30% was recorded on 13 and 14 May. The time variations of the fluxes in the first (Hβ + [O III] 4959 Å + 5007 Å) and second (Hα + [NII] 6548 Å + 6584 Å) blends were different. 相似文献
3.
We present the results of spectroscopy of 39 H II regions in the spiral galaxy NGC 6946. The spectral observations were carried out at the 6-m BTA telescope of the SAO RAS with the SCORPIO focal reducer in the multi-slit mode with the dispersion of 2.1 Å/px and spectral resolution of 10 Å. The absorption estimates for 39 H II regions were obtained. Using the “strong line” method (NS-calibration) we determined the electron temperature, and the abundances of oxygen and nitrogen for 30 H II regions. The radial gradients of O/H and N/H were constructed. 相似文献
4.
We present a new survey for Hα emission objects in the Circinus cloud complex and introduce an efficient photometric method for detecting Hα emission via observations in a narrow‐band filter. The observed flux is compared to a blackbody fit of the continuum. Our search strategy reveals 20 stars with strong Hα emission (EW > 10 Å), eight of them being new detections. All Hα stars display infrared excess corroborating their youth. On the other hand, the region contains a number of infrared excess objects that do not show Hα emission. Our results support the picture that accretion – as witnessed by Hα emission – is a highly variable phenomenon. Therefore, Hα surveys can only trace the temporarily active objects. In contrast, infrared excess is a more robust tracer that reveals most of the population of young stellar objects in a star forming region. Our analysis of the general stellar content of the region yields a reliable distance of 450 pc for the Circinus cloud. Moreover, we find a ratio of total‐to‐selective extinction of RV = 2.8 suggesting that smaller‐than‐normal dust grains may be present. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
We present an image of T Tauri N reconstructed from speckle interferometry observations made at the 3.6 m Canada-France-Hawaii telescope (CFHT). Two spectral windows, at Hα [6540-6580 Å] and red continuum [6580-6840 Å] were used. The star is unresolved in the continuum (θ ≤ 0″038), setting an upper limit for its size of ≤ 5.3 AU (assuming a 140 pc distance). At Hα (continuum subtracted) two components are observed, an unresolved one with 70% of the Hα flux and a resolved 0″106 × 0″043 (15 × 6 AU) with 30 %. The extended component is elongated in the North-South direction. The extended Hα component scale, it's non-detection in the continuum, and TTau Hα profile shape suggest that the extension is a disk corona. 相似文献
6.
We present a new method for the automatic identification and classification of dynamic Hα dark features found in time series of full-disk solar images at three Hα wavelengths (center, and ± 0.8 Å). The simultaneous Hα observations are obtained by the multi-channel Flare Monitoring Telescope (FMT) at Hida Observatory. The program was developed in order to replace the present visual detection and classification of the phenomena. Usually, an obvious dark feature found in the Hα ?0.8 Å observations probably corresponds to some phenomenon such as a surge or chromospheric network enhancement, or filament activity. Thus, one of our aims in this program is to distinguish each phenomenon by its own properties and key parameters. We optimized the threshold values of the key parameters such as the area and darkness of the transiently darkening features in Hα ?0.8 Å so that the computer can reasonably identify surges and filament activations. In comparison, for a 7-day observation period, the number of dark events detected by the program contains 89% of the events recognized visually. However, 10 times more events are detected automatically. The missing events are mainly caused by the deletion of data with poor visibility. It is found that the dark events can be identified with more precise starting and ending times by a machine than by a human. Some statistical studies of surges or other activities can be carried out based on the computer-produced database. With some modifications the program can be applied to monitor real-time dynamic features on disk, including flare ribbons. 相似文献
7.
Jongchul Chae Hyung-Min Park Kwangsu Ahn Heesu Yang Young-Deuk Park Jakyoung Nah Bi Ho Jang Kyung-Suk Cho Wenda Cao Philip R. Goode 《Solar physics》2013,288(1):1-22
For high resolution spectral observations of the Sun – particularly its chromosphere, we have developed a dual-band echelle spectrograph named Fast Imaging Solar Spectrograph (FISS), and installed it in a vertical optical table in the Coudé Lab of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. This instrument can cover any part of the visible and near-infrared spectrum, but it usually records the Hα band and the Ca ii 8542 Å band simultaneously using two CCD cameras, producing data well suited for the study of the structure and dynamics of the chromosphere and filaments/prominences. The instrument does imaging of high quality using a fast scan of the slit across the field of view with the aid of adaptive optics. We describe its design, specifics, and performance as well as data processing 相似文献
8.
Handy B.N. Tarbell T.D. Wolfson C.J. Korendyke C.M. Vourlidas A. 《Solar physics》1999,190(1-2):351-361
Since shortly after launch in April 1998, the Transition Region and Coronal Explorer (TRACE) observatory has amassed a collection of H?i Lα (1216 Å) observations of the Sun that have been not only of high spatial and temporal resolution, but also span a duration in time never before achieved. The Lα images produced by TRACE are, however, composed of not only the desired line emission, but also local ultraviolet continuum and longer wavelength contamination. This contamination has frustrated attempts to interpret TRACE observations in H?i Lα. The Very Advanced Ultraviolet Telescope (VAULT) sounding rocket payload was launched from White Sands Missile range 7 May 1999 at 20:00 UT. The VAULT telescope for this flight was a dedicated H?i Lα imaging spectroheliograph. We use TRACE observations in the 1216 Å and 1600 Å channels along with observations from the VAULT flight to develop a method for removing UV continuum and longer wavelength contamination from TRACE Lα images.
相似文献9.
We present an investigation of line-of-sight (LOS) velocity oscillations in solar faculae and sunspots. To study the phase relations between chromospheric and photospheric oscillations of the LOS velocity, we measured the time lag of the chromospheric signal relative to the photospheric one for several faculae and sunspots in a set of spectral line pairs. The measured time lags are different for different objects. The mean measured delay between the oscillations in the five-minute band in faculae is 50?s for the Si?i 10?827?Å?–?He?i 10?830?Å pair; for the pair Fe?i 6569?Å?–?Hα 6563?Å the mean delay is 20?s; for the pair Fe?i 4551?Å?–?Ba?ii 4554?Å the mean delay is 7?s; for the pair Si?i 8536?Å?–?Ca?ii 8542?Å the mean delay is 20?s. For the oscillations in the three-minute band in sunspot umbrae the mean delay is 55?s for the Si?i 10?827?Å?–?He?i 10?830?Å pair; for the Fe?i 6569?Å?–?Hα 6563?Å pair it was not possible to determine the delay; for the Fe?i 4551?Å?–?Ba?ii 4554?Å pair the mean delay is 6?s; for the Si?i 8536?Å?–?Ca?ii 8542?Å pair the mean delay is 21?s. Measured delays correspond to the wave propagation speed, which significantly exceeds the generally adopted speed of sound in the photosphere. This raises the question of the origin of these oscillations. The possibility that we deal with slow MHD waves is not ruled out. 相似文献
10.
11.
We present near-infrared observations of NGC 1068 obtained with the SHARP camera at the ESO 3.5 m telescope, and with SHARP II attached to the COME-ON+ adaptive optics system at the ESO 3.6 m telescope. From the SHARP observations we obtain a K band image of the stellar bar with 0.″4 resolution, and an upper limit to the size of the nuclear K band source of 0.″05 (3.5 pc). The adaptive optics observations are used to determine the position of the infrared nucleus with respect to the visible continuum. The centroid of the 5000 to 9000 Å continuum is displaced 0.″23 ± 0.″10 to the east and 0.″41 ± 0.″10 to the north of the K bank peak. 相似文献
12.
A large filament was observed during a multi-wavelength coordinated campaign on June 19, 1998 in the Hα line with the Swedish Vacuum Solar Telescope (SVST) at La Palma, in the coronal lines Fe ix/x 171 Å and Fe xi 195 Å with the Transition Region and Coronal Explorer (TRACE) and in EUV lines with the SOHO/CDS spectrometer and the hydrogen Lyman series with the SOHO/SUMER spectrometer. Because of its high-latitude location, it is possible to disentangle the physical properties of the Hα filament and the filament channel seen in EUV lines. TRACE images point out a dark region fitting the Hα fine-structure threads and a dark corridor (filament channel), well extended south of the magnetic inversion line. A similar pattern is observed in the CDS EUV-line images. The opacity of the hydrogen and helium resonance continua at 171 Å is almost two orders of magnitude lower than that at the Hi head (912 Å) and thus similar to the opacity of the Hα line. Since we do not see the filament channel in Hα, this would imply that it should also be invisible in TRACE lines. Thus, the diffuse dark corridor is interpreted as due to the coronal ‘volume blocking’ by a cool plasma which extends to large altitudes. Such extensions were also confirmed by computing the heights from the projection geometry and by simulations of the CDS and TRACE line intensities using the spectroscopic model of EUV filaments (Heinzel, Anzer, and Schmieder, 2003). Finally, our NLTE analysis of selected hydrogen Lyman lines observed by SUMER also leads to a conclusion that the dark filament channel is due to a presence of relatively cool plasma having low densities and being distributed at altitudes reaching the Hα filament. 相似文献
13.
Observations using a narrow band Hα filter still remain one of the best ways to investigate the fine structures and internal dynamics of solar filaments. Hα observations, however, have been usually carried out with the peak response of the filter fixed at a single wavelength, usually at the centerline, in which the investigation is limited to the Hα morphology and its time evolution. In this paper, we demonstrate that the Hα spectroscopy that takes Hα images successively at several wavelengths is a useful tool in the study of solar filaments on the solar disk. Our observation of a filament was carried out on August 3, 2004 at Big Bear Solar Observatory using the 10-inch refractor. The Lyot Hα filter was successively tuned to five wavelengths: ?0.6, ?0.3, 0.0, +0.3, and +0.6 Å from the Hα line center. Each set of wavelength scan took 15 s. After several steps of data reduction, we have constructed a five-wavelength spectral profile of intensity contrast at every spatial point. The contrast profile at each spatial point inside the filament was reasonably well fit by the cloud model as far as the contrast is high enough, and allowed us to construct the maps of τ0, v, Δ λD and S in the filament. We also found that the line center method that is often used, always yields line-of-sight velocities that are systematically lower than the cloud model fit. Our result suggests that taking Hα images at several wavelengths using a tunable filter provides an effective way of deriving physically meaningful parameters of solar filaments. Particularly constructing the time sequence of v maps appears to be a useful tool for the study of internal dynamics, like counterstreaming, in filaments. 相似文献
14.
D. N. Rustamov 《Astronomy Letters》2010,36(5):355-361
Based on 24 high-resolution echelle spectrograms of the Wolf-Rayet star HD 192163 taken in 2005–2007 at the Cassegrain focus of the 2-m Zeiss-2000 telescope at the Shemakha Astrophysical Observatory (National Academy of Sciences of Azerbaijan), we have investigated the profiles of five emission lines: He II 4859, He II 5411, CIV 5808, He I 5875, (He II + Hα) 6560. We have analyzed the echelle spectrograms using the DECH20 code. Various emission line parameters have been determined: the equivalent widths, radial velocities, central intensities, and FWHMs. The violet wing of the He II + Hα emission band has been found to be variable (from 6496 Å to 6532 Å). Significant differences in the equivalent widths and radial velocities of the He II + Hα emission band in 2005 and 2007 were revealed. This can be a manifestation of long-term variations in the star HD 192163. We have confirmed that HD 192163 belongs to the WN6 spectral subtype. 相似文献
15.
We describe a filament destabilization which occurred on 5 May 2001 in NOAA AR 9445, before a flare event. The analysis is based on Hα data acquired by THEMIS operating in IPM mode, Hα data and magnetograms obtained at the Big Bear Solar Observatory, MDI magnetograms and 171 Å images taken by TRACE. Observations at 171 Å show that ～ 2.5 hours before the flare peak, the western part of the EUV filament channel seems to split into two parts. The bifurcation of the filament in the Hα line is observed to take place ～ 1.5 hours before the flare peak, while one thread of the filament erupts ～10 min before the peak of the flare. Our analysis of longitudinal magnetograms shows the presence of a knot of positive flux inside a region of negative polarity, which coincides with the site of filament bifurcation. We interpret this event as occurring in two steps: the first step, characterized by the appearance of a new magnetic feature and the successive reconnection in the lower atmosphere between its field lines and the field lines of the old arcade sustaining the filament, leads to a new filament channel and to the observed filament bifurcation; the second step, characterized by the eruption of part of the filament lying on the old PIL, leads to a second reconnection, occurring higher in the corona. 相似文献
16.
Using the spectral data of representative solar flares observed with the infrared detector system of the solar spectrograph at Purple Mountain Observatory, we study the spectroscopic characteristics of solar flares in the Hα, the Ca i i 8?542 Å, and the He i 10?830 Å lines in different phases and various locations of flares and discuss their possible implications coupled with space observations. Our results show that in the initial phase of a flare the Hα line displays a red shift only with no wide wing. Large broadenings of the Hα line are observed a few minutes after the flare onset within small regions of 3?–?5′′ in both disk and limb flares with and without nonthermal processes. Far wings similar to those of damping broadening appear not only in the Hα line but in the He i 10?830 Å line as well in flares with nonthermal processes. Sometimes we even detect weak far-wing emission in the Ca i i 8?542 Å line in disk flares. Such large broadenings are observed in both the footpoints and the flare loop-top regions and possibly result from strong turbulence and/or macroscopic motions. Therefore, the so-called nonthermal wing of the Hα line profile is not a sufficient condition to distinguish whether nonthermal electrons are accelerated or not in a flare. The Ca i i 8?542 Å line shows lower intensity in the loop-top regions and higher intensity in the parts close to the solar surface. Emissions larger than nearby continuum in the He i 10?830 Å line are detected only in small regions with strong X-ray emissions and avoid sunspot umbrae. 相似文献
17.
Patrick F. Roche Christopher Packham David K. Aitken Rachel E. Mason 《Monthly notices of the Royal Astronomical Society》2007,375(1):99-104
Spectroscopy at 8–13 μm with T-ReCS on Gemini-S is presented for three galaxies with substantial silicate absorption features, NGC 3094, NGC 7172 and NGC 5506. In the galaxies with the deepest absorption bands, the silicate profile towards the nuclei is well represented by the emissivity function derived from the circumstellar emission from the red supergiant, μ Cephei which is also representative of the mid-infrared absorption in the diffuse interstellar medium in the Galaxy. There is spectral structure near 11.2 μm in NGC 3094 which may be due to a component of crystalline silicates. In NGC 5506, the depth of the silicate absorption increases from north to south across the nucleus, suggestive of a dusty structure on scales of tens of parsecs. We discuss the profile of the silicate absorption band towards galaxy nuclei and the relationship between the 9.7-μm silicate and 3.4-μm hydrocarbon absorption bands. 相似文献
18.
Guillermo F. Hägele Ángeles I. Díaz Mónica V. Cardaci Elena Terlevich Roberto Terlevich 《Astrophysics and Space Science》2009,324(2-4):341-342
We present high-resolution (R～20,000) spectra in the blue and the far red of circumnuclear star-forming regions (CNSFRs) in three early-type spirals (NGC3351, NGC2903 and NGC3310), which have allowed the study of the kinematics of the stars and the ionized gas in these structures and, for the first time, the derivation of their dynamical masses for the first two. In some cases, these regions, about 100 to 150 pc in size, are composed of several individual star clusters with sizes between 1.5 and 4.9 pc, estimated from Hubble Space Telescope images. The stellar dispersions have been obtained from the Calcium triplet (CaT) lines at λ λ 8494, 8542, 8662 Å, while the gas velocity dispersions have been measured by means of Gaussian fits to the Hβ and [Oiii]λ 5007 Å lines in the high-dispersion spectra. Values of the stellar velocity dispersions are between 30 and 68 km?s?1. We apply the virial theorem to estimate dynamical masses of the clusters, assuming that systems are gravitationally bounded and spherically symmetric, and using previously measured sizes. The measured values of the stellar velocity dispersions yield dynamical masses of the order of 107 to 108 M⊙ for the entire CNSFRs. Stellar and gas velocity dispersions are found to differ by about 20 to 30 km?s?1, with the Hβ emission lines being narrower than both the stellar lines and the [Oiii]λ 5007 Å lines. The douby-ionized oxygen, on the other hand, exhibits velocity dispersions comparable to those of the stars or, in some cases, even larger. We have found indications of the presence of two different kinematical components in the ionized gas of the regions. We have mapped the velocity field in the central kpc of the spiral galaxies NGC3351 and NGC2903. For the first object, the radial velocity curve shows deviations from circular motions for the ionized hydrogen consistent with its infall towards the central regions of the galaxy, at a velocity of about 25 km?s?1. For NGC3310, we present preliminary results for the velocity dispersions for one of the two observed slit position angles, two CNSFRs and the nucleus. 相似文献
19.
We have derived fundamental parameters for the previously unstudied concentrated Galactic open clusters Berkeley 77, NGC2587, BH58 and ESO324‐SC15 by means of integrated spectroscopy in the range 3800–6800 Å. The cluster integrated spectra are compared with those of solar metallicity template spectra of Galactic open clusters with known parameters. The spectra were obtained at CASLEO (San Juan, Argentina) with a resolution of 14 Å.We estimated simultaneously age and foreground interstellar reddening by comparing the continuum distribution and line strengths of the cluster spectra with those of template spectra. Berkeley 77 was found to be an old cluster of 3–4 Gyr, while the remaining three clusters are between 400 and 1000 Myr old. The derived foreground reddening values range from E (B – V) = 0.0 in NGC2587 and ESO324‐SC15 to approximately 0.30 in Berkeley 77. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
Morgenthaler Jeffrey P. Harris Walter M. Roesler Frederick L. Scherb Frank Anderson Christopher M. Doane Nathaniel E. Oliversen Ronald J. 《Earth, Moon, and Planets》2002,90(1-4):77-87
The University of Wisconsin–Madison and NASA–Goddard conducted acomprehensive multi-wavelength observing campaign of coma emissionsfrom comet Hale–Bopp, including OH 3080 Å, [O I] 6300 Å H2O+ 6158 Å, H Balmer-α 6563 Å, NH2 6330 Å, [C I] 9850 ÅCN 3879 Å, C2 5141 Å, C3 4062 Å,C I 1657 Å, and the UV and optical continua. In thiswork, we concentrate on the results of the H2O daughter studies.Our wide-field OH 3080 Å measured flux agrees with other, similarobservations and the expected value calculated from published waterproduction rates using standard H2O and OH photochemistry.However, the total [O I] 6300 Å flux determined spectroscopically overa similar field-of-view was a factor of 3-4 higher than expected.Narrow-band [O I] images show this excess came from beyond theH2O scale length, suggesting either a previously unknown source of[O I] or an error in the standard OH + ν→ O(1 D) + H branching ratio. The Hale–Bopp OH and[O I] distributions, both of which were imaged tocometocentric distances >1 × 106 km, were more spatiallyextended than those of comet Halley (after correcting for brightnessdifferences), suggesting a higher bulk outflow velocity. Evidence ofthe driving mechanism for this outflow is found in the Hα lineprofile, which was narrower than in comet Halley (though likelybecause of opacity effects, not as narrow as predicted by Monte-Carlomodels). This is consistent with greater collisional coupling betweenthe suprathermal H photodissociation products and Hale–Bopp's densecoma. Presumably because of mass loading of the solar wind by ionsand ions by the neutrals, the measured acceleration of H2O+ downthe ion tail was much smaller than in comet Halley. Tailwardextensions in the azimuthal distributions of OH 3080 Å,[O I], and [C I] , as well as a Doppler asymmetry in the[O I] line profile, suggest ion-neutral coupling. While thetailward extension in the OH can be explained by increased neutralacceleration, the [O I] 6300 Å and [C I] 9850 Å emissions show 13%and >200% excesses in this direction (respectively), suggesting anon-negligible contribution from dissociative recombination of CO+and/or electron collisional excitation. Thus, models including theeffects of photo- and collisional chemistry are necessary for the fullinterpretation of these data. 相似文献