Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
A peculiar planetary nebula candidate in a globular cluster in the Fornax dwarf spheroidal galaxy
Context: Until now, only one planetary nebula (PN) has been known in theFornax dwarf spheroidal galaxy. Aims: The discovery of a secondPN candidate, associated with one of the 5 globular clusters in theFornax dwarf, is reported. Methods: Spectra of the globularcluster H5, obtained with the UVES echelle spectrograph on the ESO VeryLarge Telescope, show [O III] line emission at a radial velocityconsistent with membership of the Fornax dwarf. A possible counterpartof the [O III] emission is identified in archival images from the WideField Planetary Camera 2 on board the Hubble Space Telescope. The sourceof the emission is located about 1.5 arcsec (less than one core radius)southwest of the centre of the cluster. Results: The emissionline source is identified as a likely PN, albeit with several peculiarproperties. No H?, He I, or He II line emission is detected and the[O III]/H? ratio is >25 (2?). The expansion velocityinferred from the [O III] 5007 Å line is Ve ? 55 kms-1, which is large for a PN. The diameter measured on theHST images is about 0.23 arcsec or 0.15 pc at the distance of the FornaxdSph. Conclusions: This object doubles the number of known PNe inFornax, and is only the 5th PN associated with an old GC for whichdirect imaging is available. It may be a member of the rare class ofextremely H-deficient PNe, the second such case found in a GC.Based on observations collected at the European Southern Observatory,Chile under programme 078.B-0631(A), and with the NASA/ESA Hubble SpaceTelescope.
| The Michigan/MIKE Fiber System Survey of Stellar Radial Velocities in Dwarf Spheroidal Galaxies: Acquisition and Reduction of Data
We introduce a stellar velocity survey of dwarf spheroidal galaxies,undertaken using the Michigan/MIKE Fiber System (MMFS) at theMagellan/Clay 6.5 m telescope at Las Campanas Observatory. As of 2006November we have used MMFS to collect 6415 high-resolution(R=20,000-25,000) spectra from 5180 stars in four dwarf spheroidalgalaxies: Carina, Fornax, Sculptor, and Sextans. Spectra sample therange 5140-5180 Å, which includes the prominent magnesium tripletabsorption feature. We measure radial velocity (RV) to a medianprecision of 2.0 km s-1 for stars as faint as V~20.5. Fromthe spectra we also are able to measure the strength of iron andmagnesium absorption features using spectral indices that correlate witheffective temperature, surface gravity, and chemical abundance.Measurement of line strength allows us to identify interlopingforeground stars independently of velocity and to examine themetallicity distribution among dSph members. Here we present detaileddescriptions of MMFS, our target selection and spectroscopicobservations, the data reduction procedure, and error analysis. Wecompare our RV results to previously published measurements forindividual stars. In some cases we find evidence for a mild,velocity-dependent offset between the RVs that we measure using themagnesium triplet and previously published RV measurements derived fromthe infrared calcium triplet. In companion papers we will present thecomplete data sets and kinematic analyses of these new observations.This paper includes data obtained with the 6.5 m Magellan Telescopeslocated at Las Campanas Observatory, Chile.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Internal Kinematics of the Fornax Dwarf Spheroidal Galaxy
We present new radial velocity results for 176 stars in the Fornax dwarfspheroidal galaxy, of which at least 156 are probable Fornax members. Wecombine with previously published data to obtain a radial velocitysample with 206 stars, of which at least 176 are probable Fornaxmembers. We detect the hint of rotation about an axis near Fornax'smorphological minor axis, although the significance of the rotationsignal in the galactic rest frame is sensitive to the adopted value ofFornax's proper motion. Regardless, the observed stellar kinematics isdominated by random motions, and we do not find kinematic evidence oftidal disruption. The projected velocity dispersion profile of thebinned data set remains flat over the sampled region, which reaches amaximum angular radius of 65'. Single-component King models in whichmass follows light fail to reproduce the observed flatness of thevelocity dispersion profile. Two-component (luminous plus dark matter)models can reproduce the data, provided that the dark component extendssufficiently beyond the luminous component and the central dark matterdensity is of the same order as the central luminous density. Theserequirements suggest a more massive, darker Fornax than standardcore-fitting analyses have previously concluded, with M/LVover the sampled region reaching 10-40 times the M/LV of theluminous component. We also apply a nonparametric mass estimationtechnique, introduced in a companion paper. Although it is designed tooperate on data sets containing velocities for >1000 stars, theestimation yields preliminary results suggesting M/LV~15inside r<1.5 kpc.
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| The shape and scale of Galactic rotation from Cepheid kinematics
A catalog of Cepheid variables is used to probe the kinematics of theGalactic disk. Radial velocities are measured for eight distant Cepheidstoward l = 300 deg; these new Cepheids provide a particularly goodconstraint on the distance to the Galactic center, R0. We model the diskwith both an axisymmetric rotation curve and one with a weak ellipticalcomponent, and find evidence for an ellipticity of 0.043 +/- 0.016 nearthe sun. Using these models, we derive R0 = 7.66 +/- 0.32 kpc andv(circ) = 237 +/- 12 km/s. The distance to the Galactic center agreeswell with recent determinations from the distribution of RR Lyraevariables and disfavors most models with large ellipticities at thesolar orbit.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
| The position corrections of 1400 stars observed with PA II in San Juan.
Not Available
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. II - Faint southern potential radial-velocity standards
Abstract image available at:http://adsabs.harvard.edu/abs/1984A&AS...57..275M
| Polarization measurements of 313 nearby stars
The linear polarization of 313 low galactic latitude stars has beenmeasured. With few exceptions all program stars have a spectral typelater than B9 and are within 600 parsec of the sun. 181 stars aresituated at the southern sky and 132 at the northern sky.
| The stellar aggregate surrounding HD 101205 (IC 2944).
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&A....54..233A&db_key=AST
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Légszivattyú |
| Rektaszcenzió: | 09h38m02.51s |
| Deklináció: | -35°04'35.8" |
| Vizuális fényesség: | 8.638 |
| Távolság: | 173.913 parszek |
| RA sajátmozgás: | -36.2 |
| Dec sajátmozgás: | -49.9 |
| B-T magnitude: | 9.858 |
| V-T magnitude: | 8.739 |
Katalógusok és elnevezések:
|
