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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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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The Medicina survey of methanol masers at 6.7 GHz
A survey of Class II methanol masers at 6.7 GHz was made in the Northernhemisphere with the 32-m Medicina radio telescope. 42 objects weredetected, 20 of them are new detections at 6.7 GHz. Our results showthat the detection rate of 6.7 GHz masers toward the inner part of theGalaxy is higher than in other directions. It is confirmed that most ofthe methanol masers are associated with faint compact HII regions. The6.7 GHz methanol masers show large velocity dispersion and largevelocity offset from the velocity of parent molecular clouds. Table 2 isonly available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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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 CS(2-1) survey of IRAS point sources with color characteristics of ultra-compact HII regions.
We have made a complete survey of the CS(2-1) emission toward IRAS pointsources in the galactic plane. The sources observed were selectedaccording to their far infrared (FIR) colors, which are characteristicof UC HII regions. They have 25μm/12μm flux ratios larger than 3.7and 60μm/12μm flux ratios larger than 19.3. The survey covered aregion from b=-2deg to b=2deg from l=300deg to l=0deg and from l=0deg tol=60deg, and from b=-4deg to b=4deg elsewhere. We detected 843 sourcesout of 1427 sources observed. The distributions of detected andundetected sources in a FIR color-color diagram show some differences,suggesting that more than one type of object is present in our observedsample.
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New detections of 5_1_-6_0_A^+^-methanol masers towards IRAS sources.
We present the results of our second search for 6.7-GHz methanol maserstowards colour-selected IRAS sources. Five hundred and twenty IRASsources that meet the far-infrared colour criteria set by Wood &Churchwell for ultra-compact HII regions were searched for 6.7-GHzmethanol maser emission, to a sensitivity limit of 5Jy. Thirty one newmaser sources were detected. We also compare the FIR colours of thenewly detected maser sources with those detected by Schutte et al.(1993) and the IRAS counterparts of sources that have both methanol andhydroxyl maser emission. It was found that the average flux distributionof the newly detected sources differs significantly from that of allother known 6.7-GHz methanol maser sources. It is argued that thedifferences may be due either to intrinsic differences between the threegroups of sources or to interstellar extinction. An analysis of therelation between the 6.7-GHz maser and IRAS flux densities shows thatthe maser flux density is always less than the 100 μm flux densitywhile only three sources have a maser flux density greater than the 60μm flux density. Far-infrared pumping of the 6.7-GHz methanol masersis therefore in principle viable although it was found that the apparentmaser efficiency will exceed 10 per cent for a significant number ofsources in the case of FIR pumping by photons between 50 and 100μm.The overall detection rates on the IRAS [25-12] vs [60-12] two-colourdiagram are also presented. Possible new search strategies for masers incolour-selected IRAS sources are discussed.
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A search for OH emission from IRAS sources at high galactic latitudes
A survey of high galactic latitude IRAS point sources with colourstypical for ultracompact HII regions was carried out in the main linesof OH. Amongst 70 IRAS sources surveyed, one new OH maser emitting onlyin the 1667 MHz main line was discovered and 6 weaker candidate maserswere found. It is proposed that the masers with dominant 1667 MHzemission are separate from the common main line Class I OH masersemitting mostly at 1665 MHz. The Class I masers could be divided intosubclasses Ia and Ib for 1665 and 1667 MHz emitting sourcesrespectively. A correlation between infrared and OH line emission fluxesis confirmed by a lower detection rate of the present survey as comparedto the survey of stronger IRAS sources. More than one half of thedetected sources show thermal OH emission and are probably associatedwith nearby dust clouds.
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Water masers associated with dense molecular clouds and ultracompact H II regions
Results are reported from a study surveying the occurrence of the H2O22GHz maser emission from bright IR sources in star-forming regions. Asample of 260 sources was selected from the IRAS Point Source Catalog,following the color selection criteria suggested by Richards et al.(1987), to identify dense molecular clouds where star formation might beat the earliest stages. Water vapor emission toward 32 sources wasdetected. Twelve new maser sources were found, all characterized byrather low integrated fluxes and narrow components. On the basis of FIRcolor indices and the maser detection rates, and from a comparison withother classes of objects, it is suggested that the sources included inthe sample not associated with ultracompact H II regions contain a highfraction of candidate molecular clouds with embedded high massprotostars still in the accretion phase.
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New Emission Nebulae
Not Available
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