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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.
| 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
| Bispectrum speckle interferometry of young jet- and outflow-sources.
Not Available
| High-Resolution Mid-Infrared Imaging and Spectroscopic Observations of a Massive Star Forming Region W51 IRS 2
Mid-infrared (7.8-13.5μm) imaging and low-resolution spectroscopicobservations were made for the massive star-forming region W51 IRS 2with spatial resolution of 1". IRS 2 was resolved into seven sourcesbased on the continuum and the emission line maps. The nature of thesesources was investigated using their thermal dust emission, the 9.7μm absorption feature, and/or three fine-structure emission lines of[Ne II] at 12.8 μm, [Ar III] at 8.99 μm, and [S IV] at 10.51μm. Four of the sources were identified as ultracompact H II regionsand one as an embedded protostar candidate. The spectral types of theionizing sources are derived from the line ratios to be all around O9,which is much later than those (O5.5 and O7.5) derived from the radiocontinuum fluxes. The observed line ratios of (ultra-)compact H IIregions in IRS 2 and in the literature follow a single excitation track,but it is different from that predicted from model calculations. Wepropose two possible resolutions for the discrepancy: (1) the employedmodels for the stellar atmosphere are not sufficiently accurate in theUV range, or (2) the (ultra-)compact H II regions are ionized by stellarclusters.
| Dusty Plasmas in Interstellar Clouds and Star Forming Regions
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| Infrared spectra and circumstellar emission of IRAS sources with ten-micron silicate absorption
Results are presented of near-infrared photometry carried out in the J,H, K, and L bands for 33 IRAS sources with a 10-micron silicateabsorption features. The observed sources were found to be mostlycomprised of two groups of stars which showed very different spectralcharacteristics from each other between 1 and 100 microns. These starswere either evolved OH/IR stars, which generally showed IR photometricspectra similar to black-body spectra; or they were young stellarobjects showing much broader spectral energy distributions thanblack-body spectra.
| CO observations of cold IRAS objects - AGB and post-AGB stars
An investigation is presented of a sample of 77 objects with IRAS fluxratios similar to those of evolved AGB stars with very coldcircumstellar envelopes (CSE), and CO observations are used to helpidentify their nature. The 21 post-AGB candidates in the sample werefound to share the characteristics of low color temperature, and, formost, low IRAS variability. They are discussed in terms of threecategories: intermediate spectral type stars with expanding molecularshells, cold circumstellar shells with CO but with no OH emission, andirregular or nonvariable OH/IR stars. The evolved stars with detectedCO, when compared with those in which CO was not detected, exhibit thefollowing characteristics: redder IRAS colors, red low-resolutionspectrometer class but not class 3n, not variable (low VAR), opticalcounterpart, and no OH emission. Evolved stars can be distinguished fromcloud sources on the basis of IRAS flux ratios.
| The giant molecular outflow in MON R2
A large, massive outflow associated with the Mon R2 infrared cluster hasbeen identified and mapped. The outflow line components are found to bewell separated in velocity from the ambient cloud line component. These'detached wings' suggest high optical depths and filling factors thatmay be characteristic of old, evolved flows. The blueshifted lobe showsevidence of shell structure similar to that seen in the L1551 outflow.The redshifted lobe is spatially more confined in the plane of the skyand its structure is uncertain. A dense, flattened, rotating core isfound near the origin of the bipolar outflow. The physical properties ofthis core are consistent with magnetized collapsing cloud models. Thederived dynamical mass of the core, roughly 1013 solar masses, issupercritical by a factor of about 10. The large-scale velocitystructure of the cloud do not appear to be consistent with such angularmomentum conservation.
| SiO and CO emission from carbon stars with silicate features and southern IRAS sources
Forty-one southern IRAS sources have been observed in the CO J = 1-0 andSiO J = 2-1, v = 1 lines with the 15-m Swedish European SubmillimeterTelescope, and CO or SiO emission has been detected in 20 sources. Among41 sources, southern carbon stars with silicate features were observedbut no CO or SiO emission was detected except in IRAS 13442-6109 forwhich the identification with the carbon star C2123 is questionable.Nondetection of SiO masers in carbon stars with silicate features favorsthe transition-phase hypothesis for the origin of these stars. Some SiOemission has been detected in stars with IRAS LRS class 4n, confirmingthat silicate absorption can mimic SiC emission in the coldest 4nsources. The detection rate and chemistry of circumstellar envelopes arediscussed.
| A survey of 12.2 GHz methanol masers and their polarization properties
Methanol emission at 12.1786 GHz, 2 - 3(-1)E, has been searched fortoward 78 nonstellar H2O masers and 33 type I OH/IR stars. Eleven newmethanol sources were found in nonstellar water masers, whereas nosources were found in stellar masers. Most of the new sources shownarrow lines with velocity widths smaller than 1 km/s and are consideredto be masers. Tentative evidence is presented that the methanol masersare not all associated with H2O and OH masers. Polarization propertieshave also been observed for five strong sources including Cepheus A andG188.94 + 0.89, which were detected in this survey. Three sources,G188.94 + 0.89, Cepheus A, and NGC 7538, are completely unpolarized, andthe other two sources show a small amount of linear polarization: a fewpercent for W3(OH) and 10 + or - 3 percent for NGC 6334.
| The large system of molecular clouds in Orion and Monoceros
Emission is noted over about one-eighth of an 850-sq deg region centeredon Orion and Monoceros that has been surveyed in the J = 1 to 0 line ofCO; most of the emission arises from giant molecular clouds associatedwith Orion A and B, and Mon R2. A much smaller area was surveyed forC-13O emission. A comparison of cloud masses obtained by threeindependent methods indicates that CO luminosity is as accurate ameasure of cloud mass as other indicators. The possible relationshipsamong clouds in the survey are discussed, including the conjecture thatthe overall Orion complex of clouds is a much larger system thanpreviously considered, incorporating most of the clouds in the presentsurvey.
| Models for infrared polarization from protostellar sources
Simple dusty models of protostellar infrared sources are developed tomatch the observed infrared polarizations. It is shown that theseobservations are generally consistent with models incorporatingscattering off large dust grains in a bipolar geometry.
| The optical properties of dust in the mid-IR silicate bands
A study of the emission silicate features of 10 supergiants and S Lep,which are all in the solar region of the Galaxy, is discussed. Theoptical efficiency of the circumstellar grain material of M stars isdeduced over the range 8-30 microns. It is shown that the efficiencyclearly peaks at 10 microns and is analogous to that of amorphousMg2SiO4. A similar procedure, using 13 available spectra of protostellarobjects, shows that the dust in molecular clouds and in the ISM, iscomposed of small (less than 1 micron) grains with an optical extinctionefficiency peaking at 9.5 microns and practically identical to that ofamorphous MgSiO3. Combining the two kinds of dust, and allowing forgrain sizes greater than 1 micron, it is possible to reproduce the wide10-micron features emitted by M giants with more or less thick shells.Using the results of meteoritic chemical analysis and of the theory ofcomposite gas condensation, the likelihood of amorphous MgSiO4 andMgSiO3 being present in circumstellar and interstellar dust,respectively, is evaluated.
| On the properties of very young massive infrared sources
The data contained in a catalog of Henning et aI. (1983) of 34 objectsmatching the defining criteria for the class of Becklin-Neugebauer (BN)objects are studied to search for relationships between observedparameters that may help to clarify the nature of these objects.Relationships between the optical depths of the ice and silicate bandsare investigated along with the correlations of these bands with suchsource parameters as shell temperature, luminosity, and polarization inthe infrared. The hydrogen emission line intensities are interpreted,and the high-velocity molecular outflows are discussed with reference toother source parameters. The physical association between BN objects andOH and H2O maser sources is addressed, showing that the objects areclearly more frequently associated with the latter sources than with theformer. Stellar wind models for the ionized region around the embeddedstar are favored after analysis of the hydrogen infrared emission lineand radio continuum intensities.
| The brighter 94 micron sources observed by the far-infrared sky survey experiment
Approximately 9000 sq deg were surveyed in four IR bands with arocket-borne Far-Infrared Sky Survey Experiment (FIRSSE). The surveycovered the galactic plane between 120 deg and 255 deg longitude andincluded the Orion and Taurus molecular clouds. A list of confirmedsources brighter than 1000 Jy at 94 microns plus other objects ofinterest is presented along with their measured fluxes at 20, 27, and 40microns. The sources are associated with galactic H II regions,molecular clouds, and cool stars. Their average extended sourcetemperatures range between about 35 and 70 K, and their IR luminositiesrange between about 100 - 100,000 solar luminosities.
| An infrared luminosity function for star-forming molecular clouds
The available data on the far-infrared luminosity of hot-centeredmolecular clouds have been combined with the known distribution ofmolecular matter to derive a luminosity function for these star-formingclouds. The statistical method of estimating this function from theobserved sample of clouds is discussed in some detail. The derivedfunction is used to estimate the total infrared luminosity in the Galaxycontributed by these discrete sources; the result agrees encouraginglywell with that obtained from radio data.
| Excitation conditions in HII regions
Herter et al. (1981, 1982 and Pipher et al. (1982) have derivedabundances in sixteen galactic HII regions from observations of theinfrared fine structure lines. The ArII/ArIII and SIII/SIV line ratiosprovide an abundance independent technique for assessing the excitationstate of the nebula. The observed ratios can be compared to modelcalculations of HII regions to evaluate the validity of the underlyingphysical assumptions of the models. The present investigation comparesmodel calculations with the observed ArII/ArIII and SIII/SIV ionicabundance ratios for a large sample of HII regions and reevaluates thediscrepancy between observations and models with these abundanceindependent measures of the excitation state of the nebulae.
| Abundances in five nearby galactic H II regions from infrared forbidden lines
Airborne measurements of the Ar II (6.99 micron) and S II (18.7) micronlines for five compact H II regions in the solar neighborhood arepresented, as well as 2-4 micron and 8-13 micron spectroscopy whereavailable. From these data and radio data, lower limits to the elementalabundances of Ar, Ne, and S are deduced. Some of these H II regionssuffer substantial nebular extinction, and some are extended. Aftercorrecting for beam size effects an extinction, it is found that four ofthe objects are consistent with standard abundances, within theuncertainties of correcting for unobserved ionization states. A Perseusarm object, S156, is apparently overabundant in sulfur.
| The search for infrared protostars
A review of the search for infrared sources in star-forming regions, andstudies of these sources and nearby interstellar matter, are presented.Particular attention is given to those objects at infrared wavelengths,and studies are directed toward the early evolution of massive-typestars. Star formation regions, globules and submillimeter sources, andinfrared sources are discussed, and clustering and location of theinfrared sources are considered. It is determined that the probableangular diameters of infrared sources in molecular clouds are less thanor on the order of 10-10 to the 3rd AU, and that the most prominentabsorption features are at 9.7 and 3.07 microns. In addition, infraredsources in molecular clouds are found to be among the most highlypolarized of all astronomical objects. Finally, it is determined that OBstars generally form in groups at molecular cloud peaks and that theycan reach large luminosities and begin ionizing radiation production,and, in the embedded stage and later, luminous stars undergo anisotropicmass loss.
| Infrared polarizations of CRL objects and OH 0739-14.
Abstract image available at:http://adsabs.harvard.edu/abs/1978PASJ...30..377K
| Optical, infrared, and radio studies of AFCRL sources
The southern point sources in the AFCRL infrared (4, 11, and 20 microns)sky survey have been studied at infrared, optical, and radiowavelengths. Searches were performed at 2.2 microns to locate thesources, near-infrared photometry of them was secured, andclassification spectra of those with optical counterparts were obtained.OH observations have yielded 14 new Type II OH/IR sources and suggest acorrelation between the OH flux densities and the infrared colors. Mostof the AFCRL sources are carbon or late M stars similar to the reddestobjects in the IRC but extending to even redder color indices. Inaddition, two emission nebulae are found along with two WC stars, fiveBe stars, and three sources lying in or near reflection nebulae. Theconfirmed sources lie preferentially within a few degrees of thegalactic plane, and the carbon stars show a galactic-longitudedistribution different from that of the remainder. Many of the sourcesprobably vary at infrared wavelengths.
| The Monoceros R2 cloud - Near-infrared and molecular observations of a rotating collapsing cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1977ApJ...215..129L
| The AFCRL Catalogue: Some Southern Sources Studied
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| Untersuchungen über Reflexionsnebel am Palomar Sky Survey I. Verzeichnis von Reflexionsnebeln
Not Available
| Studies of bright diffuse galactic nebulae with special regard to their spatial distribution.
Not Available
| TThe source of luminosity in galactic nebulae.
Not Available
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