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2MASS wide field extinction maps. I. The Pipe nebula
Context: . Aims: . We present a 8°×6°, highresolution extinction map of the Pipe nebula using 4.5 million starsfrom the Two Micron All Sky Survey (2MASS) point source catalog. Methods: . The use of Nicer (Lombardi & Alves 2001, A&A, 377,1023), a robust and optimal technique to map the dust column density,allows us to detect a AV = 0.5 mag extinction at a 3-σlevel with a 1 arcmin resolution. Results: . (i ) We find forthe Pipe nebula a normal reddening law, E(J - H) = (1.85 ± 0.15)E(H - K). (ii ) We measure the cloud distance using Hipparchos and Tychoparallaxes, and obtain 130+24-58 pc. This,together with the total estimated mass, 10^4 {M}_ȯ, makes the Pipethe closest massive cloud complex to Earth. (iii ) We compare the Nicerextinction map to the NANTEN {}12CO observations and derivewith unprecedented accuracy the relationship between the near-infraredextinction and the 12CO column density and hence (indirectly)the 12CO X-factor, that we estimate to be 2.91 ×1020 cm-2 K-1 km-1 s in therange AV in [0.9, 5.4] mag. (iv ) We identify approximately1500 OH/IR stars located within the Galactic bulge in the direction ofthe Pipe field. This represents a significant increase of the knownnumbers of such stars in the Galaxy. Conclusions: . Our analysisconfirms the power and simplicity of the color excess technique to studymolecular clouds. The comparison with the NANTEN {}12CO datacorroborates the insensitivity of CO observations to low columndensities (up to approximately 2 mag in A_V), and shows also anirreducible uncertainty in the dust-CO correlation of about 1 mag ofvisual extinction.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| Photometry of Late Dwarf Stars
Multicolor broadband photometry is presented for 146 stars. For many ofthe stars, a comparison of photometric and trigonometric parallaxes isdiscussed.
| Planetary nebula with a neutral envelope?
The IUE ultraviolet spectral recording for a low excitating planetarynebula NGC 6369 is obtained. The very strong doublet 2800 Mg II inemission as well as not less strong absorption line 2852 Mg I arediscovered in the spectrum of this nebula. It is shown that theresonance line 2852 Mg I may originate only in a neutral envelope,around the nebula, consisting of neutral hydrogen, neutral magnesium,and dust particles (H I + Mg I). The possibility of the existence of onemore envelope, transition zone immediately contacting with the brightthat is ionized part of nebula (H II + Mg II), is also shown. Thetransition zone consists of neutral hydrogen, ionized magnesium and dustparticles (H I + Mg II). The main parameters of this zone are alsoobtained. The temperature of the central star of this nebula is 48,000K. Continuous background in the interval 2600-3000 A is identified withBalmer continuum, with electron temperature T(c) = 12,500 K.
| Preliminary Version of the Third Catalogue of Nearby Stars
Not Available
| G. P. Kuiper's spectral classifications of proper-motion stars
Spectral classifications are listed for over 3200 stars, mainly of largeproper motion, observed and classified by Kuiper during the years1937-1944 at the Yerkes and McDonald Observatories. While Kuiper himselfpublished many of his types, and while improved classifications are nowavailable for many of these stars, much of value remains. For many ofthe objects, no other spectral data exist.
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