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1.
We present narrow-band emission line (Hα + [N II]λλ 6548, 6583, [O III] λλ 4959, 5007)as well as green or red continuum images of selected Seyfert galaxies. The sample includes NGC 7214, IC 4218, Akn 479, Mrk 915, IC 1515 and F 348. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
We present Hα, [N  II ]6583 and 6-cm continuum images of the emission line nebula K 3-35. The optical images reveal an extended nebula (size ≃ 11 × 9 arcsec2 in [N  II ]) in which most of the emission originates in a very narrow (width 0.7–1.3 arcsec) S-shaped region which extends almost all along the nebula (≃ 7 arcsec). The 6-cm continuum emission also arises in this narrow region, which is characterized by an exceedingly high point-symmetry and systematic and continuous changes of the orientation with respect to the nebular centre. The properties of the narrow region suggest that it represents a system of precessing bipolar jet-like components. Two low-excitation, compact bipolar knots near the tips of the jet-like components are observed in the deduced [N  II ]/Hα image ratio. These knots may be generated by the interaction of the collimated outflows with surrounding material. A comparison of the optical and radio images shows the existence of differential extinction within the nebula. Maximum extinction is observed in a disc-like region which traces the equator of the elliptical shell previously observed at 20-cm continuum. All available data strongly suggest that K 3-35 is a very young planetary nebula in which we could be observing the first stages of the formation of collimated outflows and point-symmetric structures typically observed in planetary nebulae. The properties of the jet-like components in K 3-35 are in good agreement with models of binary central stars in which highly collimated outflows originate either from a precessing accretion disc or via magnetic collimation in a precessing star.  相似文献   

3.
High dispersion CCD spectra are used to study the profiles of the Hα and Hβ lines of 48 stars in early spectral classes in the young diffuse binary cluster h/χ Per. In addition, moderate resolution spectra of 15 B and Be stars were taken over the interval 4400–4960 Å. One or, possibly, two new Be stars are discovered. The major parameters of the Hα line are measured for the observed B and Be stars. The spectra over 4400–4960 Å are used to estimate Teff, logg, and υsin i. No traces of emission are detected in the Hα line profiles for 28 of the stars and emission is observed in the Hα line for 20. During our observations an absorption profile of the Hα line was observed for some of the stars, such as Oo146, Oo566, Oo922, and Oo1268, although they have previously been identified as Be stars. A significant long-term variability of the Hα line is discovered for the Be stars Oo1161 and Oo2242. Oo2371 manifests a variability in its faint emission spectrum which is typical of close binary systems that include a Be star. __________ Translated from Astrofizika, Vol. 51, No. 2, pp. 305–319 (May 2008).  相似文献   

4.
H α and [O  iii ] narrow-band, wide-field (7×7 deg2), CCD images of the Small Magellanic Cloud were compared, and a catalogue of candidate planetary nebulae and H α emission-line stars was compiled. The catalogue contains 131 planetary nebulae candidates, 23 of which are already known to be or are probable planetary nebulae or very low excitation objects. Also, 218 emission-line candidates have been identified, with 113 already known. Our catalogue therefore provides a useful supplement to those of Meyssonnier & Azzopardi and Sanduleak, MacConnell & Davis Phillip. Further observations are required to confirm the identity of the unknown objects.  相似文献   

5.
Coudé spectra taken in the red region of 49 bright B and Be stars were examined for the behaviour of Hα and the He I λλ 5876 and 6678 line profiles. 51 per cent of the stars were found to show Hα emission to some degree and 22 per cent showed helium emission. Evidence is presented for the existence of drastic changes in the line profile and the radial velocity in some of the stars on a time scale of fractions of a day. Visiting Astronomer, Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.  相似文献   

6.
The populations of B and Be-stars in the young open clusters NGC 7419 and NGC 659 are studied. Lowresolution spectral observations in the region of the Hα line are used to study 34 members of NGC 7419 and additional spectra in the range λ3700-6200 ? are obtained for 12 stars. During the period of our observations, four previously identified Be-stars manifested an absorption profile for the Hα line. Emission in the Hα line is observed in the spectra of 21 objects. The members of the cluster NGC 7419 are classified as to spectral type. The position of the Be-stars on a two-color IR diagram and a comparison with the position of the objects in other clusters with similar ages cast doubt on the existence of two starformation waves. Moderate resolution spectra were obtained for 22 stars in the cluster NGC 659 over wavelengths of λ4050-5200 ? and for 7 objects in the neighborhood of the Hα line. Emission is observed in both the Hα and Hβ lines for two of the five Be-stars that were studied, while faint emission appears only in the Hα line in one of the stars. The other members of the cluster show no signs of emission in these spectra. Teff, log g, and Vsini are estimated for the observed stars. It is found that 5 of the objects are not members of the cluster.  相似文献   

7.
Results from a spectrophotometric study of the galaxy Kaz 701 are presented. Spectra of this galaxy were obtained on the 2.6-m telescope at the Byurakan Observatory with the SCORPIO spectral camera. In the spectra of Kaz 701, strong Hα, [OIII] λλ5007, 4959, and Hβ emission were observed, and the [SII]λλ6731, 6717 lines were observed with moderate intensities, while the [NII]λ6584 line was scarcely noticeable in the spectra obtained in 2004, but was much more intense in the spectra of 2009. The lines observed in the spectrum of this galaxy are typical of type Sy2 galaxies. A component was observed in the red wings of both the Hα and Hβ lines in the data of 2004, but, although these lines were stronger, these components were absent in the spectra taken in 2009. The relative intensities, equivalent widths, and half widths of these lines are given. These data, obtained in different observation periods (2004 and 2009), differ greatly; that is, the emission is variable.  相似文献   

8.
Optical spectroscopic data are presented on nova LW Serpentis 1978, obtained during its decline fromV 9.0 to ≃10.2 (compared to a value of ∼ 8.0 at recorded maximum). The spectrum and its evolution compare well with a typical nova, though the principal absorption (∼ −750 km s−l) was very weak in comparison with the diffuse-enhanced absorption (∼ −1300 km s−1). The principal absorption could be identified only in the lines of O I λλ7774, 8446, and in moderate-resolution observations of Hα. The salient features of spectral evolution follow: The near-infrared triplet of Ca n continuously weakened. O I λ8446 was always brighter than O I λ 7774, indicating continued importance of Lyman Β fluorescence. The lines due to [O I], [N II] and N n brightened considerably near the end of our observations (37 days from maximum). The Hα emission line was asymmetric all through with more emission towards the red. Its emission profile showed considerable structure. Based on the individual peaks in the Hα line profile, a kinematical model is proposed for the shell of LW Ser. The model consists of an equatorial ring, and a polar cone on the side away from the earth. The nearer polar cone did not show significant emission of Hα during our observations. The polar axis of the shell is inclined at a small angle (∼ 15‡) to the line of sight.  相似文献   

9.
The relationships among traditional wind and disk diagnostics - Hα and [OI]λ6300 lines and IR luminosity excesses, respectively - and star parameters are critically analysed. The total sample includes 109 PMS stars - 20 Weak-line T Tauri (WTTS), 45 Classical T Tauri (CTTS) and 44 HAeBe stars-. Our results suggest that Hα is neither a wind nor an accretion tracer. Hα and [OI] emissions seem to correlate very well with the photospheric luminosity and not with ΔLIR/Lph, a parameter related to the origin of the IR excesses. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

10.
We have used the Australia Telescope Compact Array to image four southern luminous blue variable stars: AG Car, He3-519, HR Car and WRA 751, at wavelengths of 3 and 6 cm, and resolutions of 1 and 2 arcsec respectively. With the partial exception of HR Car, all radio images show an unresolved stellar core surrounded by a large ionized gaseous nebula, and agree well with published H α and [N  ii ] optical images. The image of WRA 751 shows a stellar torus or disc. HR Car's radio image is unusual, and seems best explained by the presence of a hot binary companion.  相似文献   

11.
The CCD echelle spectra of the chromospherically active binary HR 5553 are obtained using the 2.16 m telescope with Coudé echelle spectrograph of Beijing Observatory in April 1996. The features of Ca II H & K, Hα, He I D3 and Ca II IRT2 (λ 8542 AA) & IRT3 (λ 8662 AA) are presented. The absolute fluxes of these lines which provide the useful information to study the chromospheric activity of HR 5553 are given. The fundamental parameters of the cool dwarf component of HR 5553 are determined using the analysis of the observed spectra with a resolution of R ≃ 60000 and signal-to-noise ratio S/N = 100 ∼ 300. A detailed spectroscopic analysis has yielded the following fundamental parameters: Effective temperature: Teff = 4881 K Surface gravity: log(g) = 3.65 Logarithmic iron abundance: [Fe/H] = –0.30 as well as that of other 12 metal elements (relative to the Sun) are listed in the Table II and Table III. Microturbulence: ζ = 1.20 km s-1. Magnetic field measurements of the cool dwarf component of HR 5553 have been made using the Stenflo-Lindegren statistical analysis and the profile-addition technique. The magnetic field strength and filling factor are obtained. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

12.
The radio maps of ten small Hii regions at λλ=2.8, 6 and 11 cm, obtained with the 100-m MPIR radiotelescope, are given. A comparison of the radio fluxes obtained with parameters of exciting stars is carried out. For four compact Hii regions — namely, S146, S152, S237 and S297 — we present the results of observations with the radiotelescope of the U.S.S.R. Academy of Sciences, RATAN-600. The paper also presents estimates of the physical conditions in nebulae, and conclusions are drawn about the possible stage of their evolution.  相似文献   

13.
The evolution of the Star Formation Rate (SFR) density of the Universe as a function of look-back time is a fundamental parameter in order to understand the formation and evolution of galaxies. The current picture, only outlined in the last years, is that the global SFR density has dropped by about an order of magnitude from a redshift of z∼1.5 to the current value at z=0. Because these SFR density studies are now extended to the whole range in redshift, it becomes mandatory to combine data from different SFR tracers. At low redshifts, optical emission lines are the most widely used. Using Hα as current-SFR tracer, the Universidad Complutense de Madrid (UCM) Survey provided the first estimation of the global SFR density in the Local Universe. The Hα flux in emission is directly related to the number of ionizing photons and, modulo IMF, to the total mass of stars formed. Metallic lines like [OII]λ3727 and [OIII]λ5007 are affected by metallicity and excitation. Beyond redshifts z∼0.4, Hα is not observable in the optical and [OII]λ3727 or UV luminosities have to be used. The UCM galaxy sample has been used to obtain a calibration between [OII]λ3727 luminosity and SFR specially suitable for the different types of star-forming galaxies found by deep spectroscopic surveys in redshifts up to z∼1.5. These calibrations, when applied to recent deep redshift surveys confirm the drop of the SFR density of the Universe since z∼1 previously infered in the UV. However, the fundamental parameter that determines galactic evolution is mass, not luminosity. The mass function for local star-forming galaxies is critical for any future comparison with other galaxy populations of different evolutionary status. Hα velocity-widths for UCM galaxies indicate that besides a small fraction of 1010-1011 M⊙ starburst nuclei spirals, the majority have dynamical masses in the ∼109 M⊙ range. A comparison with published data for faint blue galaxies suggests that star-forming galaxies at z∼1 would have SFR per unit mass and burst strengths similar to those at z=0, but being intrinsically more massive. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

14.
We present near-infrared spectra of seven radio-loud quasars with a median redshift of 2.1, five of which were previously known to have Ly α nebulae. Extended [O  iii ] λ 5007 and H α emission are evident around six objects, at the level of a few times 10−16 erg cm−2 arcsec−2 s−1 within ≃2 arcsec of the nucleus (≡16 kpc in the adopted cosmology). Nuclear [O  ii ] λ 3727 is detected in three of the five quasars studied at this wavelength and clearly extended in one of them.
The extended [O  iii ] tends to be brighter on the side of the nucleus with the stronger, jet-like radio emission, indicating at least that the extranuclear gas is distributed anisotropically. It is also typically redshifted by several hundred km s−1 from the nuclear [O  iii ], perhaps because of the latter being blueshifted from the host galaxy's systemic velocity. Alternatively, the velocity shifts could be due to infall (which is suggested by linewidths ∼1000 km s−1 FWHM) in combination with a suitable dust geometry. Ly α /H α ratios well below the case B value suggest that some dust is present.
Photoionization modelling of the [O  iii ]/[O  ii ] ratios in the extended gas suggests that its pressure is around or less than a few times 107 cm−3 K; any confining intracluster medium is thus likely to host a strong cooling flow. A comparison with lower redshift work suggests that there has been little evolution in the nuclear emission-line properties of radio-loud quasars between redshifts 1 and 2.  相似文献   

15.
We present new high- and low-resolution spectroscopic and photometric data of nine members of the young association CMa R1. All the stars have circumstellar dust at some distance, as could be expected from their association with reflection nebulosity. Four stars (HD 52721, HD 53367, LkH α  220 and LkH α  218) show H α emission and we argue that they are Herbig Be stars with discs. Our photometric and spectroscopic observations of these stars reveal new characteristics of their variability. We present first interpretations of the variability of HD 52721, HD 53367 and the two LkH α stars in terms of a partially eclipsing binary, a magnetic activity cycle and circumstellar dust variations, respectively. The remaining five stars show no clear indications of H α emission in their spectra, although their spectral types and ages are comparable with those of HD 52721 and HD 53367. This indicates that the presence of a disc around a star in CMa R1 may depend on the environment of the star. In particular we find that all H α emission stars are located at or outside the arc-shaped border of the H  ii region, which suggests that the stars inside the arc have lost their discs through evaporation by UV photons from nearby O stars, or from the nearby (<25 pc) supernova, about 1 Myr ago.  相似文献   

16.
The velocity field in the galaxy Mark 8 is studied by means of observations with the 2.6-m telescope at the Byurakan Astrophysical Observatory using the VAGR spectrograph. In the optical range, the central portion of this galaxy consists of five bright condensations which are superassociations (SA). These studies were made in a wavelength range that encompasses images of the galaxy in the Hα and [NII] λλ6548 and 6583Å emission lines. The radial velocity field was obtained. The velocities of all the superassociations were measured and a rotation curve constructed for the galaxy. The relative intensities of the emission lines have been determined. Images are constructed in the Hα and [NII] lines and in the red continuum. It is concluded that the superassociations were formed together and are, as a whole, young. The shape of the rotation curve shows that Mark 8 is an isolated galaxy with a composite multicomponent nucleus. Translated from Astrofizika, Vol. 51, No. 4, pp. 543–553 (November 2008).  相似文献   

17.
The abundances of the light (Na to Ca) elements in disc and halo stars are reviewed. New analyses are emphasized. Elements considered are the α-nuclei (Mg, Si, and Ca), and the odd-even nuclei (Na and Al, also25Mg and26Mg). The α-nuclei are overabundant (relative to Fe) in the old disc and halo stars. Halo stars ([Fe/H] < —1.2) have [α/Fe] ∼0.3 with extreme halo ([Fe/H] ≲ −2.0) stars showing possibly higher overabundances. The scatter in [α/Fe] at a given [Fe/H] is small. To within the observational errors, the abundance patterns for Mg, Si, and Ca are identical. For disc stars, the Na and Al abundances relative to Mg are almost independent of the [Fe/H]. Halo stars ([Fe/H] < −1) show [Na/Mg] < 0 and [AI/Mg] < 0, but the form of the mean relation and the scatter about the relation between [odd-even/Mg] and [Fe/H] remains uncertain.  相似文献   

18.
The central stars of two of the new planetary nebulae found during scans of the AAO/UKST H α Survey of the Milky Way have been found to exhibit Wolf–Rayet (WR) emission features. One (PMR 1) is an early-type star of class either [WO4] or [WC4]. The other (PMR 2) is a late [WC] star which, depending on the classification scheme used, is either intermediate in class between [WC9] and [WC10] or the sole member of the [WC10] class. Both stars exhibit unusual spectral features which may be attributed to enhanced nitrogen in their atmospheres and could be indicative of unusual stellar evolution.  相似文献   

19.
A 16-inch Schmidt-Cassegrain telescope on the campus of Naresuan University of Thailand and several similar-size telescopes in China equipped with CCD cameras were used to observe 14 high amplitude delta Scuti stars: GP And, CY Aqr, BS Aqr, YZ Boo, AD CMi, VZ Cnc, EH Lib, DY Her, V927 Her, KZ Hya, BE Lyn, V1162 Ori, DY Peg, and CW Ser, between the years 1999 and 2010. Data were also collected from scientific journals and sources on the Internet for these variable stars. Times of light maximum of these delta Scuti stars were then either determined from the observations or obtained from the literature to analyze the pulsation period variations. For the 14 delta Scuti stars we concluded that 7 stars (BS Aqr, CY Aqr, AD CMi, EH Lib, KZ Hya, BE Lyn and DY Peg) are binary or multiple systems. 10 delta Scuti stars are found with periods increasing with rates between 5.86×10−9 and 2.34×10−6 per year and the other 4 stars (BS Aqr, DY Her, BE Lyn and DY Peg) show periods decreasing with rates of about 10−9 to 10−8 per year.  相似文献   

20.
We present preliminary results of long-slit spectroscopic observations of the extended emission line region (hereafter, EELR) in NGC 4388. We detect broad emission lines in the line complexes Hα+[NII] and [SII] which can be modelled by the superposition of several narrow components. Multicomponent line profiles appear at positions very close to the ionization cone axis. There is also some correspondence with the radio emission, which suggests that there is interaction between the radio jets and the ionized gas. We do not confirm the claim of a broad Hα component (FWZI=4000 km/s) by Shields and Filippenko (1996). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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