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|New catalogue of blue stragglers in open clusters|
We present a catalogue of blue-straggler candidates in galactic openclusters. It is based on the inspection of the colour-magnitude diagramsof the clusters, and it updates and supersedesthe first version(Ahumada & Lapasset 1995). A new bibliographical search was made foreach cluster, and the resulting information is organised into twotables. Some methodological aspects have been revised, in particularthose concerning the delimitation of the area in the diagrams where thestragglers are selected.A total of 1887 blue-straggler candidates have been found in 427 openclusters of all ages, doubling the original number. The catalogued starsare classified into two categories mainly according to membershipinformation.The whole catalogue (Tables 8, 9, notes, and references) is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/463/789
|Photometric survey of marginally investigated open clusters. I. Basel 11b, King 14, Czernik 43|
Aims.To progress in galactic studies based on open clusters, e.g.cluster formation rate or kinematical properties, one needs to improvethe number of open clusters observed. However, only half of the 1700known galactic open clusters have been properly observed so far, makingany statistical investigation insignificant, especially at largerdistances from the Sun. Methods: .We study marginallyinvestigated or neglected open clusters with Bessell CCD BVR photometry,whose data were used to fit isochrones to the individual color-magnitudediagrams. Results: .We examined the galactic clusters Basel 11b,King 14 and Czernik 43, the last being observed for the first time tothis extent. As well as a careful comparison to available photometry,their parameters such as age, interstellar reddening, distance andapparent diameter were determined. The obtained cluster properties wereverified by near infrared 2MASS data. The three investigatedintermediate age clusters are all located in the galactic disk withdistances between 1.8 and 3.0 kpc from the Sun.
|A photometric study of the two poorly known northern open clusters NGC 133 and NGC 1348|
We present CCD UBVI observations obtained in the field of the previouslyunstudied northern open clusters NGC 133 and NGC 1348. We argue that NGC133 is a heavily contaminated cluster, for which we identify 13candidate members down to V=14.50 mag on the basis of the position inthe two-color Diagram. Membership has been checked against propermotions from Tycho 2, whenever available. The cluster turns out to havea reddening E(B-V)=0.60+/-0.10 mag, to be 630+/-150 pc distant from theSun, and to have an age less than 10 Myrs. NGC 1348 is a more reddenedclusters (E(B-V)=0.85+/-0.15 mag) for which we isolate 20 members. Thecluster lies at a distance of 1.9+/-0.5 kpc away from the Sun, and hasan age greater than 50 Myrs. Based on observations carried out at MtEkar, Asiago, Italy. Photometry is only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/479
|Protogalactic Starbursts at High Redshift|
We have computed the evolving ultraviolet-millimeter spectral energydistribution (SED) produced by protogalactic starbursts at highredshift, incorporating the chemical evolution of the interstellarmedium in a consistent manner. Dust extinction is calculated in a novelway that is not based on empirical calibrations of extinction curves,but rather on the lifetime of molecular clouds which delays theemergence of each successive generation of stars at ultravioletwavelengths by typically 15 Myr. The predicted rest-framefar-infrared-to-millimeter-wave emission includes the calculation ofmolecular emission-line luminosities (12CO and O2among other molecules) consistent with the evolving chemical abundances.Here we present details of this new model along with the results ofcomparing its predictions with several high-redshift observables,namely, the ultraviolet SEDs of Lyman limit galaxies, the high-redshiftradio galaxies 4C 41.17 and 8C 1435, the SCUBA submillimeter survey ofthe Hubble Deep Field (HDF), and the SEDs of intermediate-redshiftelliptical galaxies. With our new reddening method, we are able to fitthe spectrum of the Lyman limit galaxy 1512-cB58, and we find anextinction of about 1.9 mag at 1600 Å. This extinction applies tostarbursts with spectral slope α in the range0<~α<~1.5. The model also predicts that most Lyman limitgalaxies should have a value of α inside that range, as isobserved. The 850 μm flux density of a typical Lyman limit galaxy isexpected to be only ~=0.5 mJy, and therefore the optical counterparts ofthe most luminous submillimeter sources in the HDF (or any othercurrently feasible submillimeter survey) are unlikely to be Lyman breakgalaxies. The passive evolution of our starburst model is also comparedwith Keck observations of the reddest known elliptical galaxy at z~1.5and with the SED of a typical nearby elliptical galaxy. The SED of thehigh-redshift elliptical is nicely matched by the starburst model withan age of 4 Gyr and the SED of the nearby elliptical galaxy with an ageof 13 Gyr.
|Star-forming loops in the IRAS sky images|
Loops containing diffuse and discrete emission are a feature of the IRASsky images. Some of these loops are limb-brightened shells resultingfrom supernovae or stellar winds acting on the interstellar medium.Secondary star formation appears to have occurred at the surface ofthese shells. A significant proportion of the early-type stars in thesolar neighborhood appear to have formed in stellar loops.
|Neutral hydrogen towards 3C 10, the remnant of Tycho's supernova|
Aperture synthesis observations of neutral hydrogen towards the remnantof Tycho's supernova (AD 1572), 3C 10, have been made with the CambridgeHalf-Mile Telescope. Details of the absorption features indicate thatthe distance of 3C 10 is in the range of 1.7-3.7 kpc. The neutralhydrogen in a cloud in the local arm has a spin temperature of about 80K and an optical depth of order unity. Numerous arc and filamentarystructures are seen in emission; some have been analyzed in terms ofexpanding shells. These are found to have H I masses between 500 solarmasses and 280,000 solar masses, and H I kinetic energies between 3.5 x10 to the 40th J and 6 x 10 to the 43rd J. Stellar winds are proposed asenergy sources for two of the arcs because three open clusters are nearthe center of curvature of one, and a bright star near the center of theother. An open cluster, three 9th mag stars and two CO clouds are seento coincide with various minima in the H I emission. Two other CO cloudscoincide with bright H I emission features, as does the small H IIregion S175.
|Three colour photometry and spectral classification of stars in the region of NGC133, NGC146, and K-14|
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