13CO (J = 1 -- 0) Survey of Molecular Clouds toward the Monoceros and Canis Major Region
rough a large-scale 13CO(J=1-0) survey toward a region inMonoceros and Canis Major, we present following results: (1) Weidentified in total 115 clouds. (2) GroupI (CMaOB1 and G220.8 ‑1.7) may physically connected with GroupII (Mon R2 and NGC2149). (3)496YSO candidates were chosen from IRAS point source catalog (IPC). (4)The mass spectrum of the Local clouds shows a power-law relation with anindex of ‑1.55 ± 0.09. (5) The number fraction ofstar-forming clouds increases as the cloud mass increases. Especially,massive clouds of Mcloud≥103.5Modot are all star-forming clouds. (6) Theline width-cloud radius relation is best fitted asΔVcomp ∝ rcloud0.47(correlation coefficient = 0.87). (7) The distribution of(Mvir / Mcloud) shows that star-forming cloudstend to be more virialized than no star-forming clouds. (8) Starformation in GroupI is more active than that in GroupII. (9) Unexpectedsmall number of low-mass clouds in GroupI may be due to strong UVradiation from O-type stars in the vicinity of the clouds. (10) Starformation in GroupII might occurred by self-gravitational, except forthe most massive cloud.
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An Extremely Young Massive Stellar Object near IRAS 07029-1215
In the course of a comprehensive millimeter/submillimeter survey ofmassive-star-forming regions, the vicinities of a sample of 47 luminousIRAS sources were closely investigated with the SubmillimeterCommon-User Bolometric Array and the MPIfR bolometers in order to searchfor massive protostellar candidates. A particularly interesting objecthas been found in the surroundings of the bright far-infrared sourceIRAS 07029-1215. Follow-up line observations show that the object iscold, has a massive envelope, and is associated with an energeticmolecular outflow. No infrared point source has been detected at itsposition. Therefore, it is a very good candidate as a member of thelong-sought group of massive protostars.
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New infrared star clusters in the Northern and Equatorial Milky Way with 2MASS
We carried out a survey of infrared star clusters and stellar groups onthe 2MASS J, H and Ks all-sky release Atlas in the Northernand Equatorial Milky Way (350deg < l < 360deg, 0deg < l < 230 deg). Thesearch in this zone complements that in the Southern Milky Way (Dutra etal. \cite{Dutra03}a). The method concentrates efforts on the directionsof known optical and radio nebulae. The present study provides 167 newinfrared clusters, stellar groups and candidates. Combining the twostudies for the whole Milky Way, 346 infrared clusters, stellar groupsand candidates were discovered, whereas 315 objects were previouslyknown. They constitute an important new sample for future detailedstudies.
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Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is 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/399/141
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The stellar composition of the star formation region CMa R1 - II. Spectroscopic and photometric observations of nine young stars
We present new high- and low-resolution spectroscopic and photometricdata of nine members of the young association CMa R1. All the stars havecircumstellar dust at some distance, as could be expected from theirassociation with reflection nebulosity. Four stars (HD52721, HD53367,LkHα220 and LkHα218) show Hα emission and we arguethat they are Herbig Be stars with discs. Our photometric andspectroscopic observations of these stars reveal new characteristics oftheir variability. We present first interpretations of the variabilityof HD52721, HD53367 and the two LkHα stars in terms of a partiallyeclipsing binary, a magnetic activity cycle and circumstellar dustvariations, respectively. The remaining five stars show no clearindications of Hα emission in their spectra, although theirspectral types and ages are comparable with those of HD52721 andHD53367. This indicates that the presence of a disc around a star in CMaR1 may depend on the environment of the star. In particular we find thatall Hα emission stars are located at or outside the arc-shapedborder of the Hii region, which suggests that the stars inside the archave lost their discs through evaporation by UV photons from nearby Ostars, or from the nearby (<25pc) supernova, about 1Myr ago.
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The distribution of bright OB stars in the Canis Major-Puppis-Vela region of the Milky Way
The picture of the young stellar groups in the Canis Major-Puppis-Vela(215 deg
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The stellar composition of the star formation region CMa R1 - I. Results from new photometric and spectroscopic classifications
A new photometric and spectroscopic survey of the star formation region(SFR) CMa R1 is described. In a sample of 165 stars brighter than 13thmag, 88 stars were found to be probable members of the SFR. They aredefined as early-type stars with E(B-V)>=0.16mag, which correspondsto a distance of about 1kpc. 74 of the probable members are B stars. 19stars are possibly associated with an IRAS point source. We derive amost probable distance of 1050+/-150pc to the association. It appearsthat about 80 candidate members are pre-main-sequence stars with ageslower than 6 million years, while the main sequence extends over6.0-7.6mag, which is consistent with star formation starting about 8million years ago and continuing until at least half a million yearsago. Two bright B stars in the association (GU CMa and FZ CMa) seem tobe much older and probably do not originate from the same star formationepisode. The star formation efficiency appears to increase roughlymonotonically with time up to half a million years ago. From our data,we conclude that only a minor fraction of the stars has been createdthrough the scenario suggested by Herbst & Assousa, in which themembers of CMa R1 form by compression of ambient material by a supernovashock wave. An extensive search for candidate members with Hαemission did not reveal new Herbig Ae/Be candidates, so that the numberof stars in this class seems to be limited to four: Z CMa, LkHα218, LkHα 220 and possibly HD 53367.
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The Cepheid distance to M96 and the Hubble constant
HST WFPC2 observations of Cepheids in M96 (NGC 3368) are used to find adistance to that galaxy of 11.2+/-1.0Mpc. This estimate is based on acalibration of the Cepheid period-luminosity relation in the LargeMagellanic Cloud, and includes a correction for the difference inmetallicity between the two systems. There are good reasons forbelieving M96 is at the same distance as four E/S0 galaxies in the Leo-Igroup, and hence we calibrate secondary distance indicators based on theearly-type galaxies, namely the fundamental plane andsurface-brightness-fluctuation method. Also the Type Ia supernova 1998buoccurred in M96 itself and is used to calibrate the SN Ia distancescale. These methods reach to recession velocities of greater than5000kms-1 and can therefore allow us to evaluate the Hubbleconstant without reference to the peculiar velocity of M96 itself. Infact, these indicators agree well between themselves and hence we findH0=67+/-7kms-1Mpc-1 where the quotederror includes estimates of potential systematic effects.
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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.
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A survey of vacuum-ultraviolet extinction curves based on International Ultraviolet Explorer spectra
This paper presents the interstellar extinction curves derived from theIUE spectra with the aid of the already published 'artificialstandards'. The variety of possible shapes of the curves, demonstratedearlier on spectra from the TD/1 satellite, is fully confirmed.
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Red and infrared colours of B stars and the reddening law in the Galaxy
The red and infrared intrinsic colours of B stars are derived fromphotometric observations through the UBV(RI)_CJHK and Hβ filters of257 early-type stars. Those stars for which the UBV and Hβmeasurements match the published spectral class, and which show no othersigns of peculiarity, are used to determine the intrinsic photometriccolours of B stars in the red and infrared. From these intrinsic coloursthe interstellar reddening relationships for the red and infraredcolours are evaluated, and the results are compared with previousestimates of these quantities. The values of R, E(B-V) and the distanceare then determined for the individual stars. R is confirmed to be closeto 3.1 in most cases, but was found to be much larger in somedirections. The relationship between R and the location of a star in theGalaxy is investigated. Usually the abnormally reddened stars seemed tobe associated with known regions of star formation. The paper alsoidentifies seven likely variable stars and a number of stars withpossible dust shells.
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A Radial Velocity Database for Stephenson-Sanduleak Southern Luminous Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..823R&db_key=AST
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Derivation of the Galactic rotation curve using space velocities
We present rotation curves of the Galaxy based on the space-velocitiesof 197 OB stars and 144 classical cepheids, respectively, which rangeover a galactocentric distance interval of about 6 to 12kpc. Nosignificant differences between these rotation curves and rotationcurves based solely on radial velocities assuming circular rotation arefound. We derive an angular velocity of the LSR of{OMEGA}_0_=5.5+/-0.4mas/a (OB stars) and {OMEGA}_0_=5.4+/-0.5mas/a(cepheids), which is in agreement with the IAU 1985 value of{OMEGA}_0_=5.5mas/a. If we correct for probable rotations of the FK5system, the corresponding angular velocities are {OMEGA}_0_=6.0mas/a (OBstars) and {OMEGA}_0_=6.2mas/a (cepheids). These values agree betterwith the value of {OMEGA}_0_=6.4mas/a derived from the VLA measurementof the proper motion of SgrA^*^.
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Conditions of search for magnetic stars at early evolution stages.
Not Available
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A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
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A Study of the Kinematics of the Local Dark Clouds
Not Available
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An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
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Infrared emission of Canis Major OB1/R1 star forming region
Using IRAS data, the infrared emission character of the star-formingregion CMa OB1/R1 complex was studied in detail and compared with theoptical, CO, and radio continuum observations. The results show that theemission from this complex consists of a diffuse emission and severaldiscrete sources. The infrared diffuse emission can be explained by twoO stars, but the extended H II region may be the combined result of aremnant of an old H II region and those two O stars, which are still onthe main sequence. Most of the discrete sources correspond to theemission or reflection nebulae, but a few have no optical counterparts.The latter may be excited by early-type stars just arriving at the mainsequence and still embedded in dense dust cloud.
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Has interstellar forbidden Fe X been detected in the spectrum of SN 1987 A?
The detection of forbidden Fe X is found to be inconsistent with the lowlevels of diffuse X-ray flux identified with the Einstein and RosatX-ray satellites. The observed line can be interpreted as the slightlyredshifted wavelength 6379.3 of the diffuse interstellar band, in whichcase the velocity would equal that of the strong interstellar atomiclines in the spectrum of SN 1987 A. The unique feature is interpreted tobe evidence of variations in the ratios of interstellar lines forabsorbing clouds.
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The Infrared Emission from the Star Forming Region Canis-Majoris / OB1 / r1 Complex
Not Available
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Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
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Observations of the polarization of the radiation of R-association stars
A Ritchey-Chretien 1-m telescope was used to perform observations of thepolarization parameters of the radiation of stars in the reflectionnebulae in the regions of Cas, Per R1, Ser, and CMa R1. The connectionbetween the polarization vector and the structure of the nebulae isconsidered, and it is shown that the occurrence of polarization is dueboth to the absorption of the light of the stars and to scattering byelongated dust grains. The orientation of the grains is due to themagnetic field.
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Radio continuum observations of the Canis Major R1 region
Observations of the CMa R1 region in the radio continuum at 10 GHz weremade using the 45-m radio telescope at the Nobeyama Radio Observatory.The beam size was 2.7 arcmin in HPBW. An area of 2 x 3 deg containingthree H II regions (S292, S296, and S297) was scanned, and a calibratedmap was obtained. This area has rather uniform foreground extinction andcontains no hidden compact H II region. The emission ring (S296) shows athermal spectrum, confirming the ionization balance between OB stars andionized gases in the CMa OB1 region. A new small radio source is alsofound on the northwest side of the map.
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Exciting stars and the distances of the diffuse nebulae
Not Available
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A survey of ultraviolet objects
An all-sky survey of ultraviolet objects is presented together with astatistical analysis that leads to the conclusion that there is asignificantly higher population of hot subdwarfs lying below themain-sequence than hitherto thought. The distribution of all ultravioletobjects, main sequence ultraviolet objects, and MK unclassifiedultraviolet objects are shown in galactic coordinates, and the absolutemagnitudes and color-color diagrams for these groups are presented.Scale heights are derived, giving values similar to planetary nebulaefor the hottest groups.
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R associations. VI - The reddening law in dust clouds and the nature of early-type emission stars in nebulosity from a study of five associations
Positions, identification charts, UBVRIKLMN photometry and spectraltypes are given for stars, illuminating reflection nebulae that arevisible on the POSS prints, which have been identified in fiveassociations. With a ratio of total to selective extinction of 4.2, thereddening law applicable to the dust clouds in which the stars areembedded is steeper than normal. The five associations exhibit 18early-type stars with circumstellar shells, of which those with spectraltypes earlier than B5 characteristically have weak IR excesses, incontrast to the strong excesses indicative of circumstellar dust, oflater-type stars. Color-magnitude charts show a distribution lying abovethe ZAMS by up to about 2 mag for both the circumstellar shell stars andthose classified as rapid rotators. It is suggested that (1) rapidrotation accounts for the scatter in the color-magnitude diagram, and(2) many of the nebulous early-type emission-line stars are rapidrotators rather than pre-main sequence objects.
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Velocity structure in the Canis Major R1 molecular clouds
CO emission has been mapped over a 5 x 5 deg area in the Canis MajorOB1/R1 region; most of the emission is confined to an elliptical regionof approximately 90 x 60 pc. While most of the emission falls in the LSRvelocity range 10-20 km/s, some material is found over the full velocityrange covered (-30 to +45 km/s). There is no simple pattern that wouldindicate a single expanding shell, but the observations are consistentwith the idea that some energetic process, which occurred in aninitially inhomogeneous cloudy medium, was responsible for the observedmorphology of the region. Simple arguments suggest that a supernovaexplosion is the most likely candidate for the energetic process.
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Molecular clouds associated with reflection nebulae. I - A survey of carbon monoxide emission
The paper presents 2.6 mm wavelength CO and (C-13)O observations of 130molecular clouds associated with reflection nebulae. Enhanced COemission was found in the vicinity of the illuminating star in abouthalf the objects studied. There is a tendency for the CO peak to beslightly displaced from the star. Many examples of peaks that appear toresult from heating of the cloud by the nearby star are found, whileothers appear to be associated with independent concentrations ofmaterial.
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Optical and infrared properties of the newly formed stars in Canis Major R1
Abstract image available at:http://adsabs.harvard.edu/abs/1978ApJ...223..471H
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The differential blanketing of the main-sequence and near-main-sequence M67 stars relative to the Hyades and Coma
The blanketing of main-sequence stars in the Hyades, Coma, and M67, andof F subgiants in M67 is compared on the basis of red photometry. Therequired reddening corrections are derived by several techniques thatare insensitive or probably insensitive to blanketing. The meanreddening values obtained are E(B-V) of approximately 0.016 for theHyades, 0.006 for Coma, and 0.053 for M67. These reddening values areshown to imply that there is measurable reddening well inside 100 pc,that Crawford's (1975) A- and F-star relations must be slightly revised,that significant numbers of relatively nearby field A stars are slightlyreddened, that the North Galactic Pole stars of Hilditch et al. (1976)are reddened by 0.01 to 0.03 in B-V, and that Hyades-field F-star b-ycomparisons must be revised. It is found from the reddening-correctedphotometry that: (1) the differential Hyades-M67 blocking is greater inabsolute value for early G late F stars; (2) effects of evolution on theF IV stars in M67 are clearly discernible in the UV and marginally so inB-V; and (3) the F stars on and very near the M67 main sequence haveapproximately the Coma blocking and considerably less than the Hyadesblocking, which indicates that the zero-age metallicity of M67 issolar-normal.
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