תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
3D mapping of the dense interstellar gas around the Local Bubble
We present intermediate results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,motivated by the availability of accurate and consistent parallaxes fromthe Hipparcos satellite. Equivalent widths of the interstellar NaID-line doublet at 5890 Å are presented for the lines-of-sighttowards some 311 new target stars lying within ~ 350 pc of the Sun.Using these data, together with NaI absorption measurements towards afurther ~ 240 nearby targets published in the literature (for many ofthem, in the directions of molecular clouds), and the ~ 450lines-of-sight already presented by (Sfeir et al. \cite{sfeir99}), weshow 3D absorption maps of the local distribution of neutral gas towards1005 sight-lines with Hipparcos distances as viewed from a variety ofdifferent galactic projections.The data are synthesized by means of two complementary methods, (i) bymapping of iso-equivalent width contours, and (ii) by densitydistribution calculation from the inversion of column-densities, amethod devised by Vergely et al. (\cite{vergely01}). Our present dataconfirms the view that the local cavity is deficient in cold and neutralinterstellar gas. The closest dense and cold gas ``wall'', in the firstquadrant, is at ~ 55-60 pc. There are a few isolated clouds at closerdistance, if the detected absorption is not produced by circumstellarmaterial.The maps reveal narrow or wide ``interstellar tunnels'' which connectthe Local Bubble to surrounding cavities, as predicted by the model ofCox & Smith (1974). In particular, one of these tunnels, defined bystars at 300 to 600 pc from the Sun showing negligible sodiumabsorption, connects the well known CMa void (Gry et al. \cite{gry85}),which is part of the Local Bubble, with the supershell GSH 238+00+09(Heiles \cite{heiles98}). High latitude lines-of-sight with the smallestabsorption are found in two ``chimneys'', whose directions areperpendicular to the Gould belt plane. The maps show that the LocalBubble is ``squeezed'' by surrounding shells in a complicated patternand suggest that its pressure is smaller than in those expandingregions.We discuss the locations of several HI and molecular clouds. Usingcomparisons between NaI and HI or CO velocities, in some cases we areable to improve the constraints on their distances. According to thevelocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 arecloser than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI cloudsare seen at less than 90 pc and 85 pc in the directions of the MBM 12and MBM 41-43 clouds respectively, but the molecular clouds themselvesmay be far beyond. The above closest molecular clouds are located at theneutral boundary of the Bubble. Only one translucent cloud, G192-67, isclearly embedded within the LB and well isolated.These maps of the distribution of local neutral interstellar NaI gas arealso briefly compared with the distribution of both interstellar dustand neutral HI gas within 300 pc.Tables 1 and 2 are 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/411/447
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| The Hercules H I shell - Distances of the gas clouds and topography of the shell
The structure and distances of high-latitude (l between 35 and 75 deg)neutral gas clouds constituting the galactic H I shell GS 57 + 41(which, due to its location in the constellation of Hercules was named'Hercules shell') are investigated, using the results of an extensivesurvey of interstellar Na I D absorption lines to determine distances tothe various neutral clouds and filaments in this field of the sky. Basedon the distances, conclusions are drawn with regard to the morphologicalstructure and the physical parameters of the GS 57 + 41. The results ofoptical high-resolution absorption and 21 cm emission line measurementsof the various H I clouds were compared with the cirrus of IRAS 100micron dust emission, as well as with the diffuse X-ray backgroundemission in this area.
| Meridian observations made in Brorfelde (Copenhagen University Observatory) 1975-76.
This catalogue presents positions for selected faint stars mainly fromAGK3 observed with the 7" transit circle at Brorfelde. The stars aredistributed in 43 selected areas around radio sources and are suitableas reference stars for measuring the optical counterparts to the radiosources. The obscr 'itioi cre carried out from 1975.16 to 1976.04, andevery star was observed at least two times giving a m.s.e. of "13 forthe catalogue positions given in the FK4 system. These positions usedtogether with AGK3 proper motions will in the period 1975 to 1980 have am.s.e. at the epoch ranging from `:13 to `:15, which is less than halfof what is expected when using AGK3 positions. Key words: transit circle- catalogue of positions
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | כתר צפוני |
| התרוממות ימנית: | 16h14m46.28s |
| סירוב: | +34°30'59.0" |
| גודל גלוי: | 8.499 |
| מרחק: | 170.94 פארסק |
| תנועה נכונה: | -8.9 |
| תנועה נכונה: | 19.2 |
| B-T magnitude: | 8.94 |
| V-T magnitude: | 8.536 |
קטלוגים וכינוים:
|
