The optical morphology of A3667 re-examined
The galaxy cluster A3667 was observed using the Two-degree Field (2dF)multifibre spectroscopic system on the Anglo-Australian Telescope in aprogram designed to examine the velocity structure in the region.Specifically, we sought evidence from the optical data for the putativecluster merger believed to be responsible for the observed radio andX-ray emission. We present 184 new redshifts in the region, of which 143correspond to member galaxies of A3667. We find the cluster velocitydistribution to be well modelled by a single Gaussian in agreement withprevious results. In addition, new redshift-selected isodensity plotssignificantly reduce the prominence of the previously reported subgroupto the north-west of the main cluster. Instead, we find the galaxydistribution to be elongated and well mixed, with a high velocitydispersion and no significant evidence for substructure. These resultsare consistent with the axis of the proposed merger being close to theplane of the sky.
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Prospects for population synthesis in the H band: NeMo grids of stellar atmospheres compared to observations
Context: .For applications in population synthesis, libraries oftheoretical stellar spectra are often considered an alternative totemplate libraries of observed spectra, because they allow a completesampling of stellar parameters. Most of the attention in publishedtheoretical spectral libraries has been devoted to the visual wavelengthrange.Aims.The goal of the present work is to explore the near-infraredrange where few observed fully calibrated spectra and no theoreticallibraries are available.Methods.We make a detailed comparison oftheoretical spectra in the range 1.57-1.67 μm for spectral types fromA to early M and for giant and dwarf stars, with observed stellarspectra at resolutions around 3000, which would be sufficient todisentangle the different groups of late-type stars. We selected theNeMo grids of stellar atmospheres to perform this comparison.Results.Wefirst demonstrate that observed spectral flux distributions can bematched very well with theoretical ones for almost the entire parameterrange covered by the NeMo grids at moderate resolution in the visualrange. In the infrared range, although the overall shape of the observedflux distributions still matches reasonably well, the individualspectral features are reproduced by the theoretical spectra only forstars earlier than mid F type. For later spectral types the differencesincrease, and theoretical spectra of K type stars have systematicallyweaker line features than those found in observations. Thesediscrepancies are traced back to stem primarily from incomplete data onneutral atomic lines, although some of them are also related tomolecules.Conclusions.Libraries of theoretical spectra for A to early Mtype stars can be successfully used in the visual regions for populationsynthesis, but their application in the infrared is restricted to earlyand intermediate type stars. Improving atomic data in the near infraredis a key element in making the construction of reliable libraries ofstellar spectra feasible in the infrared.
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
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New Elements for 80 Eclipsing Binaries IV.
This research presents new elements for 80 eclipsing binaries found withthe help of the ASAS-3, Hipparcos and NSVS databases.
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New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
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The 2dF Galaxy Redshift Survey: spectra and redshifts
The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshiftsfor approximately 250000 galaxies. This paper describes the surveydesign, the spectroscopic observations, the redshift measurements andthe survey data base. The 2dFGRS uses the 2dF multifibre spectrograph onthe Anglo-Australian Telescope, which is capable of observing 400objects simultaneously over a 2° diameter field. The sourcecatalogue for the survey is a revised and extended version of the APMgalaxy catalogue, and the targets are galaxies with extinction-correctedmagnitudes brighter than bJ=19.45. The main survey regionsare two declination strips, one in the southern Galactic hemispherespanning 80°×15° around the SGP, and the other in thenorthern Galactic hemisphere spanning 75°×10° along thecelestial equator; in addition, there are 99 fields spread over thesouthern Galactic cap. The survey covers 2000deg2 and has amedian depth of z=0.11. Adaptive tiling is used to give a highly uniformsampling rate of 93 per cent over the whole survey region. Redshifts aremeasured from spectra covering 3600-8000Å at a two-pixelresolution of 9.0Å and a median S/N of 13pixel-1. Allredshift identifications are visually checked and assigned a qualityparameter Q in the range 1-5 Q>=3 redshifts are 98.4 per centreliable and have an rms uncertainty of 85kms-1. The overallredshift completeness for Q>=3 redshifts is 91.8 per cent, but thisvaries with magnitude from 99 per cent for the brightest galaxies to 90per cent for objects at the survey limit. The 2dFGRS data base isavailable on the World Wide Web at http://www.mso.anu.edu.au/2dFGRS.
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A new library of stellar optical spectra
Attention is given to a new digital optical stellar library consistingof spectra covering 3510-8930 R at 11-A resolution for 72 differentstellar types. These types extend over the spectral classes O-M andluminosity classes I-V. Most spectra are of solar metallicity stars butsome metal-rich and metal-poor spectra are included. This new library isquantitatively compared to two previously published libraries. It offersseveral advantages over them: it is photometrically well-calibratedindividually and consistently from star to star. Good temperature andluminosity coverage has been achieved. The incorporation of stars withwell-determined temperature, metallicity, and surface gravity parametersincreases the accuracy of the spectral type assigned to each compositelibrary star.
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A library of stellar spectra
Spectra for 161 stars having spectral classes O-M and luminosity classesV, III, and I have been incorporated into a library available onmagnetic tape. The spectra extend from 3510 to 7427 A at a resolution ofabout 4.5 A. The typical photometric uncertainty of each resolutionelement in the spectra is on the order of 1 percent while broad-bandvariations are smaller than 3 percent. Potential uses for the libraryinclude population synthesis of galaxies and clusters, tests of stellaratmosphere models, spectral classification, and the generation of colorindices having arbitrary wavelength and bandpass.
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Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
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Prediction of spectral classification from photometric observations-application to the UVBY beta photometry and the MK spectral classification. I - Prediction assuming a luminosity class
An algorithm based on multiple stepwise and isotonic regressions isdeveloped for the prediction of spectral classification from photometricdata. The prediction assumes a luminosity class with reference touvbybeta photometry and the MK spectral classification. The precisionattained is about 90 percent and 80 percent probability of being withinone spectral subtype respectively for luminosity groups I and V and forluminosity groups III and IV. A list of stars for which discrepanciesappear between photometry and spectral classification is given.
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Detection of errors in spectral classification by cluster analysis
Cluster analysis methods are applied to the photometric catalogue ofuvby-beta measurements by Hauck and Lindemann (1973) and point out 249stars the spectral type of which should be reconsidered or thephotometric indices of which should be redetermined.
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Photoelectric UBV observations made on the Palomar 20-inch telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.164..133P&db_key=AST
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Interstellar reddening near the north galactic pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972PASP...84..497F&db_key=AST
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INHABITED SKY
