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Interstellar Nai D lines towards the Southern Coalsack
The interstellar Nai D absorption-line profiles observed for 15 starswith lines of sight towards the Southern Coalsack are analysed. Themethod of profile fitting was used in an attempt to determine columndensities, linewidths and velocities for the individual interstellarclouds contributing to the observed absorption lines. In common, theobserved spectra show a prominent component which is probably associatedwith the nearest absorbing material composing the Coalsack. The obtainedspatial velocity distribution shows great similarity with earlierresults from CO emission. In addition, the Nai D data reveal evidencefor the existence of two or three other structures with radialvelocities of about -22, -33 and -40kms-1. Such componentsmay be the counterparts of interstellar structures observed in diffuseHα and CO emission. The assumption that at least one of thesecomponents originated in the Carina arm imposes ~0.9-1.0kpc as themaximum distance to the near side of that arm.
| The Southern Coalsack - Extinction and distance
H-beta and uvby photometric observations are reported for 236 stars oftypes B, A, and F in the region of the Southern Coalsack. Data obtainedwith the 50-cm Stromgren Automatic Telescope at ESO are presented inextensive tables, graphs, and maps and characterized in detail. Threedistinct structures are identified: (1) a nearby region (d less than 200pc) dominated by stars in front of the Coalsack, with evidence of a verydiffuse feature; (2) an intermediate region (d = 200-1100 pc) with starsreddened by Coalsack dust and/or the ISM behind it; and (3) a distantregion (d = 1.1-3.0 kpc) in which the reddening of 22 early B starsimplies a color-excess lower limit of E(b-y) = 0.230 mag, consistentwith a 10,000-solar-mass cloud at d = 1.2 kpc. The average upper-limitdistance to the main Coalsack components is estimated as 180 + or - 26pc, with some material possibly as near as 120 pc.
| Stromgren and H-beta photometry of stars earlier than G0 in the Southern Coalsack direction
Four-color and H-beta photometry have been obtained for 236 starsearlier than G0 in order to study the color excess distribution in theSouthern Coalsack direction. The beta histogram of the stars reveals arelative absence of stars in the range of A4 to A9. The (b-y)distribution for B-type stars suggests the existence of three differenttypes of stars located at different distances.
| CCD measurements of visual binaries
CCD measurements of visual double stars were obtained with the ESO 1.5 mdanish reflector. All binaries observed are candidates for the HIPPARCOSInput Catalogue. More than 400 observations have been made in four clearnights. The accuracy obtained is comparable to the accuracy of thephotographic technique, but the observing and reduction times are oneorder of magnitude smaller.
| Photographic measurements of southern double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985PASP...97..579K&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Mosca |
| Ascensione retta: | 12h49m02.47s |
| Declinazione: | -65°35'35.5" |
| Magnitudine apparente: | 7.318 |
| Distanza: | 1250 parsec |
| Moto proprio RA: | -14.4 |
| Moto proprio Dec: | -11.4 |
| B-T magnitude: | 7.28 |
| V-T magnitude: | 7.315 |
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