目录
图像
上传图像
DSS Images Other Images
相关文章
Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
| Star formation in the Cepheus Flare region - II. A-type stars associated with IRAS sources
In order to reveal the star-forming history of the molecular cloudcomplex we studied the intermediate mass stellar population in theCepheus Flare region. (Paper I dealt with the distance and the youngstellar object candidates of the region.) Correlating the IRAS PointSource Catalogue and Faint Source Catalogue positions with those of 1214B8-A8 and 1760 F0-F5 type stars brighter thanF12F25ν212ν225 ≈ 4.3, V>> 13mag and classified during an objective prism survey, weidentified 19 stars showing far-infrared excess emission in the CepheusFlare region. In addition to the 16 stars whose counterparts are givenin the IRAS catalogues, we found three more stars with infrared excessnot recognized before. In order to identify the young medium-mass starsassociated with the Cepheus Flare molecular clouds we observed theoptical spectra of the IR-excess stars, and using published opticalphotometry and the IRAS data we examined their spectral energydistributions (SEDs) and IRAS two-colour diagram. The observationsresulted in the discovery of a new Herbig Ae/Be star, BD +68°1118,coinciding with IRAS 21169+6842. More evolved HAe/Be stars may beSAO19953, BD +67°1314 and BD +69°1231, whose Hα linesshowed weak emission components. Possible β Pictoris- or Vega-typestars may be HD 203854, HD 212826 and HD 216486, whereas thefar-infrared fluxes at the positions of BD +72°1018, HD 210806 andHD 217903 can be attributed to the heating of the interstellarenvironment. We used distances and radial velocities of the starsderived from the spectroscopy and published optical photometry asindicators of their relations to the clouds. Information on theenvironment of the observed stars deduced from the diffuse interstellarband at λ6613 is briefly discussed.
| Star Formation in the Cepheus Flare Molecular Clouds. I. Distance Determination and the Young Stellar Object Candidates
Results of an objective prism Schmidt survey are combined with IRASsurvey data in order to assess the star-forming activity in the CepheusFlare, a nearby giant molecular cloud complex at ~+15 deg above theGalactic equator. The distribution of absorbing matter along the line ofsight was also studied. The Wolf diagrams, displaying the cumulativedistribution of field star distance moduli, show that the interstellarmatter in this region is concentrated at three characteristic distances:200, 300, and 450 pc. The three components, though partly overlapping,can be separated along the Galactic latitude. Within the area of theCepheus Flare, distances are determined for 14 Lynds dark clouds and forsome other clouds. In order to compile a sample of young stellar object(YSO) candidates, three types of star formation signposts were searchedfor the following: 1. Prestellar cores in the IRAS 100 mu m opticaldepth image of the region, 2. Far-infrared sources representing embeddedYSOs and optically visible pre-main-sequence star candidates using IRASPoint Source Catalog, Faint Source Catalog, and calibrated IRAS detectorscans, 3. H alpha emission stars appearing on low-dispersion objectiveprism Schmidt plates as candidate pre-main-sequence stars. The IRAS 100mu m optical depth image of the region revealed 107 dense cores. Most ofthem are probably "starless" cores and, as such, potential sites offuture star formation. One hundred twenty-two IRAS point sources wereselected as probable YSOs at various evolutionary stages. An objectiveprism search for H alpha emission stars covering an area of about 150deg2 resulted in the detection of 142 H alpha emission stars. Infraredfluxes taken from the IRAS catalogs or determined from the detectorscans are listed for 95 of them. This sample is expected to consist ofmostly T Tauri stars associated with the cloud complex. Finding chartsand catalogs of the young stellar object candidates are also given.These results may serve as a basis for further dedicated studies of theregion and will be useful for comparison when star-forming activity inother cloud complexes is investigated.
| A Study of the Kinematics of the Local Dark Clouds
Not Available
| The luminosity of reflection nebulae
Consideration is given to the connection between the dispersion inHubble's relation for reflection nebulae and their morphologicalcharacteristics. Statistical estimates show that the reflection nebulaeconnected with more opaque dust-gas clouds, compared to those near lessopaque clouds, have large values of Delta-B (the measure of deviationsin Hubble's relation) and a high surface brightness. These propertiesare more pronounced in the Herbig Ae/Be stars. Stars in the nebulaeconnected with more opaque dust-gas clouds were found to exhibit excessreddening, with R above 3.1. It is concluded that the dispersion in theHubble relation is mainly due to the optical depth of the nebulae.
| BVR observations of polarization parameters of stars in reflection nebulas
The observed polarizations of the nuclei of reflection nebulas and fieldstars in B, V, R filters are given. A connection has been found betweenthe direction of the polarization vector, the structure of thereflection nebula, and the shape of the cloud in which the nebula issituated. The direction of the plane of polarization for stars seenthrough the filamentary structure of a nebula is the same as thedirection of the filaments. Stars situated at the edges of clouds andchannels have direction of the polarization vector the same as theapparent boundary of the cloud.
| Polarization of stars in R-associations - Observational data
Polarimetric data are assembled for 95 stars that are illuminatingreflection nebulae. Most of these belong to 18 standard R-associations.The observed dependence of the percentage polarization P on wavelengthand color excess E(B-V) suggest that the unpolarized light ofR-association members may become polarized as it traverses an ensembleof dust grains aligned by a magnetic field which in some cases (Tau R2,Ori R1/R2, Sco R1, Cep R2) is intrinsic to the association. In certainR-associations the grain size is variable and the stochastic magneticfield component fluctuates on a scale of 10-30 pc.
| Mass spectra of young stars
Data on the mass spectra of young stars from various regions arestudied, with a view to correlations with the properties of theassociated molecular clouds and the spatial distributions of stars, inorder to arrive at a determination of the initial mass function ofstars. The most massive stars seem to form in the dense cores of formingclusters or associations, and the mass of the most massive young starincreases systematically with the mass of the associated molecularcloud, in keeping with the view that molecular cloud cores grow byaccretion and become progressively more massive and condensed. The moremassive stars form by accumulation, rather than fragmentation, in thedense core regions of protoclusters. If stellar winds play an importantrole in limiting the masses that forming stars can attain, the maximumstellar mass should increase with the ambient gas density and withturbulence. These predictions are borne out by observations.
| A study of the nine interstellar dark clouds
An investigation of the physical and chemical properties of nineinterstellar dark clouds, L1407, L1551, L1544, L134N, L63, L1147, L1235,L1253, and L1257 are reported. Observations of a variety of atomic andmolecular species have been obtained, and the clouds have been partiallymapped in the near infrared. The observations have been compared withtheoretical models of the line emission and absorption from interstellarclouds to derive many of the fundamental physical parameters. Thetemperatures, densities, masses, sizes, and abundances of atomic andmolecular species in the clouds have been determined along withvariations of the density and temperature as a function of radius.
| Molecular clouds associated with reflection nebulae. I - A survey of carbon monoxide emission
The paper presents 2.6 mm wavelength CO and (C-13)O observations of 130molecular clouds associated with reflection nebulae. Enhanced COemission was found in the vicinity of the illuminating star in abouthalf the objects studied. There is a tendency for the CO peak to beslightly displaced from the star. Many examples of peaks that appear toresult from heating of the cloud by the nearby star are found, whileothers appear to be associated with independent concentrations ofmaterial.
| Observational studies relating to stars formation. III.
Not Available
| Stars in reflection nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..233R&db_key=AST
| Observations of the Spatial Structre of Interstellar Hydrogen. I. High-Resolution Observations of a Small Region
Abstract image available at:http://adsabs.harvard.edu/abs/1967ApJS...15...97H
| A study of reflection nebulae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966AJ.....71..990V&db_key=AST
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
INHABITED SKY
