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Distribution of early type stars and dusty matter in the direction of the star cluster NGC 2175
The distribution of 120 O-B9-A2 stars and of the interstellar dust inthe direction of the star clusters NGC 2175 and NGC 2175s (the complexS252) is studied in terms of V, (B-V), and (U-B) data. Ten star groups(associations) are found at distances of 410, 720, 1000, 1500, 2200,3100, 4000, 5200, 7000, and 8100 pc. Three of these, at distances of410, 720, and 1000 pc, are type B associations. The remaining seven areOB associations. They are designated as Gem B 0.41, Gem B 0.72, Gem B1.0, Gem OB 1.5, Gem OB 2.2, Gem OB 3.1, Gem OB 4.0, Gem OB 5.2, Gem OB7.0, and Gem OB 8.1. The V absorption (AV) for stars No.2, 18, 20, 23,24, 26, 40, 41, 47, 69, 87, 88, 90, 95, 100 and 109 is estimated to be2m.78,4m.72, 2m.69, 3m.33, 2m.61, 2m.86, 4m.67, 6m.21, 3m.14, 3m.92,2m.69, 3m.04, 5m.95, 5m.95, 3m.20 and 5m.66, respectively. For most ofthese stars the absorption lies between 0m.5 and 2m.5. This largeabsorption may be caused by circumstellar absorption. The dust in theassociations Gem B 0.41 and Gem B 0.72 is distributed nonuniformly.There is no dust in the space between the associations. Essentiallythere is no dust inside those groups (associations) which lie atdistances greater than 1 kpc.
| Stellar tracers of the Cygnus Arm. I. Spectroscopic study of bright photometric candidates
We present medium-resolution spectroscopy of a sample of stars in thesecond Galactic quadrant selected from the literature because theircolours suggest that they are moderately-reddened early-type stars atvery large distances. From the derived spectral types and observedcolours, we calculate distances to all these objects. For a sizablefraction of our sample, we find distances well in excess of what isexpected for Perseus Arm objects, even allowing for rather generouserrors. In the interval l=150degr -180degr , there is a large number ofobjects with distances in excess of 4 kpc, which are likely tracing theOuter or Cygnus Arm. In particular, we find that the association Cam OB3is placed on this Arm. Based on our results, the extent and definitionof the associations Cas OB4 and Aur OB2 need to be reevaluated.Based on observations made at Observatoire de Haute Provence (CNRS),France.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| UBVRI photometry and polarimetry of the stars in S252 (NGC 2175). II. Interpretation.
Photoelectric UBVRI photometry and polarimetry and photographic UBVRphotometry have been used to study the stellar cluster NGC2175associated with the Hii region-molecular cloud complex Sharpless252. Thecolour excess E_B-V_ of stars in NGC2175 ranges from the foregroundcolour excess of 0.4mag up to 1.7mag. The distance modulus of S252obtained by fitting ZAMS to the colour-magnitude diagrams of NGC2175 is11.7+/-0.3mag (2.2+/-0.3kpc). The lower part of the colour-magnitudediagrams of the main cluster contains stars still contracting towardsZAMS indicating an age of the order of one million years for thecluster. The age of a small subcluster to the east of the Hii region isa few million years. High stellar polarizations up to 12% have beenobserved. The average wavelength of the maximum polarization in S252 is0.53+/-0.01μm and the polarization efficiency is near the empiricalmaximum value 3A_v_. The polarization field in S252 is regular butcannot be explained by a single magnetic field direction.
| UBVRI photometry and polarimetry of the stars in S 252 (NGC 2175). I. The observations.
Photoelectric UBVRI photometry and polarimetry and photographic UBVRphotometry of stars in the direction of the galactic H II regionSharpless 252 are reported
| Diffuse Infrared Emission of the S:252 HII Region - Molecular Cloud Complex
Not Available
| The List of the Pairs of Stars with Different Light Absorptions in the Circumstellar Environments
Not Available
| Further observations of stars associated with the Sharpless H II region SH 2-252, and of the Herbig A0e star SH 2-252b
JHKLM photometry (obtained with the 2.1-m telescope of San Pedro MartirNational Observatory in December 1986) and high-resolution 646-676-nmcoude spectroscopy (obtained with the 2.2-m telescope at Calar Alto inJanuary 1986) are reported for stars in the H II region Sh 2-252. Thedata are presented in tables, maps, and sample spectra and discussed indetail. Embedded radio source E is found to be a bright H-alpha knotwith a smooth 8-km/sec velocity gradient; its second-brightest star, Sh2-252b, is classified as a Herbig A0e star. Source C has a normalspectrum and is close to the emission-line star IRS 7, probably ofHerbig type B9e.
| Precise positions, separations, and position angles of visual binaries
Astrometric observations of 212 large visual binaries are reported. Dataobtained with a GG 495 yellow filter on IIaD photographic plates usingthe Zen astrograph (aperture 20 cm and focal length 2077 mm) of theOsservatorio Astronomico di Brera during 1985-1986 are presented inextensive tables. The potential significance of these measurements forthe catalog being constructed for the Hipparcos space observatory isindicated.
| Eight-colour photometry of stars associated with selected Sharpless H II regions at L exp II of about 190 deg - S 252, S 254, S 255, S 257, and S 261
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&A...171..216C&db_key=AST
| Exciting stars and the distances of the diffuse nebulae
Not Available
| NGC 2175 - The cluster age and the nature of the nebulosity surrounding S 252a
The galactic cluster NGC 2175 has been proposed as an extraordinarilyyoung stellar association. New photometric and spectroscopic data do notsupport this suggestion. There do not appear to be any pre-main-sequenceB stars present in the cluster. We have derived an age for the clusterof 2 million years. The physical nature of an optical nebulosityassociated with the B star S 252a was investigated. It is concluded thatthe object is primarily a reflection nebula due to a dense neutralcloud. This cloud is surrounded by a thin, high density, low excitationionized zone. An evolutionary model for the cloud is proposed.
| The bright condensation 3C153.1 inside the HII region NGC 2175
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&A....14..408G&db_key=AST
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