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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A survey of the 6.7 GHz methanol maser emission from IRAS sources. I. Data
We report the first results of a search for 6.7 GHz methanol masers inthe direction of 1399 IRAS objects north of declination-20deg with the flux densities greater than 100 Jy at 60 mu mand the flux density ratio F60/F25>1.Observations were made with the sensitivity of 1.7 Jy and the velocityresolution of 0.04 km s-1 using the 32-m Toruń radiotelescope. Maser emission was found in 182 sources, including 70 newdetections. 32 new sources were identified with objects of radioemission associated with star-forming regions. Comparison of the presentdata set with other observations suggests that about 65% of methanolmasers exhibit moderate or strong variations on time-scales of about 4and 8 years. Table 2 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/Abstract.html
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Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds
We present a full-sky 100 mu m map that is a reprocessed composite ofthe COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground andconfirmed point sources removed. Before using the ISSA maps, we removethe remaining artifacts from the IRAS scan pattern. Using the DIRBE 100and 240 mu m data, we have constructed a map of the dust temperature sothat the 100 mu m map may be converted to a map proportional to dustcolumn density. The dust temperature varies from 17 to 21 K, which ismodest but does modify the estimate of the dust column by a factor of 5.The result of these manipulations is a map with DIRBE qualitycalibration and IRAS resolution. A wealth of filamentary detail isapparent on many different scales at all Galactic latitudes. Inhigh-latitude regions, the dust map correlates well with maps of H Iemission, but deviations are coherent in the sky and are especiallyconspicuous in regions of saturation of H I emission toward denserclouds and of formation of H2 in molecular clouds. In contrast,high-velocity H I clouds are deficient in dust emission, as expected. Togenerate the full-sky dust maps, we must first remove zodiacal lightcontamination, as well as a possible cosmic infrared background (CIB).This is done via a regression analysis of the 100 mu m DIRBE map againstthe Leiden-Dwingeloo map of H I emission, with corrections for thezodiacal light via a suitable expansion of the DIRBE 25 mu m flux. Thisprocedure removes virtually all traces of the zodiacal foreground. Forthe 100 mu m map no significant CIB is detected. At longer wavelengths,where the zodiacal contamination is weaker, we detect the CIB atsurprisingly high flux levels of 32 +/- 13 nW m-2 sr-1 at 140 mu m andof 17 +/- 4 nW m-2 sr-1 at 240 mu m (95% confidence). This integratedflux ~2 times that extrapolated from optical galaxies in the Hubble DeepField. The primary use of these maps is likely to be as a new estimatorof Galactic extinction. To calibrate our maps, we assume a standardreddening law and use the colors of elliptical galaxies to measure thereddening per unit flux density of 100 mu m emission. We find consistentcalibration using the B-R color distribution of a sample of the 106brightest cluster ellipticals, as well as a sample of 384 ellipticalswith B-V and Mg line strength measurements. For the latter sample, weuse the correlation of intrinsic B-V versus Mg2 index to tighten thepower of the test greatly. We demonstrate that the new maps are twice asaccurate as the older Burstein-Heiles reddening estimates in regions oflow and moderate reddening. The maps are expected to be significantlymore accurate in regions of high reddening. These dust maps will also beuseful for estimating millimeter emission that contaminates cosmicmicrowave background radiation experiments and for estimating soft X-rayabsorption. We describe how to access our maps readily for general use.
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Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
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A survey of star-forming regions in the 5 CM lines of OH.
We have undertaken a comprehensive search for 5 cm OH masers in regionsvisible from Effelsberg with the 100-m telescope (i.e., those withdeclinations above -29^o^). Our sample is based on bright sources takenfrom the IRAS Point Source Catalog and/or from previous 18 cm OH and H_2_O surveys. Among the 165 sources observed, 16 are new (15 exhibitemission and one source shows both absorption and emission). Two newabsorption line sources have been tentatively detected. The generalproperties of the 5 cm OH sources are presented and discussed. The6035MHz line is more often detected than the 6031MHz line. Nevertheless,the latter line is frequently present, a fact that is not explained bypresent OH excitation models. Simple calculations tend to show thatthere are enough FIR photons to pump the 6035 and 6031MHz masers, and wefound that the statistics of the ratio S_ radio_/S_ IR_ at 18, 5 and 6cm suggest that the maser pumping efficiency decreases with increasingOH excitation. Variability on short (months) or long (years) time-scalesis a common feature in many 5 cm OH sources. We also presentobservations of the 6 GHz satellite lines and report, besides W3(OH), ontwo certain and perhaps two newly detected weak sources. Someimplications on the excitation of OH are briefly discussed. Clearly,there is no efficient maser mechanism for the satellite lines. We derivethe percentage of circular polarization in detected 6035 and 6031 MHzemission sources and suggest the identifications of possible Zeemanpatterns. We have found several features having > 90 % polarization.Combining our magnetic field measurements with other published resultswe find that the dominant field alignment is consistent with thedirection of the Galactic rotation. However, there is no convincingcorrelation of the field direction with the Galactic spiral pattern, andit is possible that the field direction is not preserved in the starformation process.
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SAO stars with infrared excess in the IRAS Point Source Catalog
We have undertaken a search for SAO stars with infrared excess in theIRAS Point Source Catalog. In contrast to previous searches, the entireIRAS (12)-(25)-(60) color-color diagram was used. This selection yieldeda sample of 462 stars, of which a significant number are stars withcircumstellar material. The stars selected can be identified aspre-main-sequence stars, Be stars, protoplanetary systems, post-AGBstars, etc. A number of objects are (visual) binary stars.Characteristic temperatures and IR excesses are calculated and theirrelations to spectral type are investigated.
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Young stellar objects detected by IRAS
Fluxes of 453 IRAS point sources selected for proximity to dense gashave been accurately determined by co-adding IRAS data. From this set,258 sources are detected in all four bands: 12, 25, 60, and 100 microns.As distance from dense molecular material increases, these sourcesexhibit systematic trends in color and a markedly decreasing luminosity.These trends are broadly consistent with expected evolutionary changesin these stars, with younger objects found closer to dense gas. Thesedata suggest a subtle variation on the criterion for identifying theyoungest objects detectable by IRAS, in addition to that of steeplyrising spectra: a color temperature which is uniform across all fourIRAS bands in the range 40-50 K. These characteristics are used as acriterion to select point sources as candidate very youngpre-main-sequence stars.
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The luminosity of reflection nebulae
Consideration is given to the connection between the dispersion inHubble's relation for reflection nebulae and their morphologicalcharacteristics. Statistical estimates show that the reflection nebulaeconnected with more opaque dust-gas clouds, compared to those near lessopaque clouds, have large values of Delta-B (the measure of deviationsin Hubble's relation) and a high surface brightness. These propertiesare more pronounced in the Herbig Ae/Be stars. Stars in the nebulaeconnected with more opaque dust-gas clouds were found to exhibit excessreddening, with R above 3.1. It is concluded that the dispersion in theHubble relation is mainly due to the optical depth of the nebulae.
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Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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Structure and physical conditions of the dense gas in the Monoceros R2 molecular cloud
Observations of (C-13)O, S, and NH3 in the Mon R2 molecular cloud arepresented. The existence of a dense 3-pc 4000-solar mass region isrevealed. The high-resolution observations of the (1,1) and (2,2) linesof NH3 show the presence of 1-65-solar mass clumps. A minimum in the NH3emission is observed toward the compact H II region.
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Polarization of stars in R-associations - Observational data
Polarimetric data are assembled for 95 stars that are illuminatingreflection nebulae. Most of these belong to 18 standard R-associations.The observed dependence of the percentage polarization P on wavelengthand color excess E(B-V) suggest that the unpolarized light ofR-association members may become polarized as it traverses an ensembleof dust grains aligned by a magnetic field which in some cases (Tau R2,Ori R1/R2, Sco R1, Cep R2) is intrinsic to the association. In certainR-associations the grain size is variable and the stochastic magneticfield component fluctuates on a scale of 10-30 pc.
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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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R associations. V. MON R2.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81..840H&db_key=AST
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Stars in reflection nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..233R&db_key=AST
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A study of reflection nebulae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966AJ.....71..990V&db_key=AST
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Studies of bright diffuse galactic nebulae with special regard to their spatial distribution.
Not Available
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TThe source of luminosity in galactic nebulae.
Not Available
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The color of the nebulous stars.
Not Available
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INHABITED SKY
