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|The Southern Galactic Plane Survey: Polarized Radio Continuum Observations and Analysis|
The Southern Galactic Plane Survey (SGPS) is a radio survey in the 21 cmH I line and in 1.4 GHz full-polarization continuum, observed with theAustralia Telescope Compact Array and the Parkes 64 m single-dishtelescope. The survey spans a Galactic longitude of253deg
|MSX mid-infrared imaging of massive star birth environments - II. Giant HII regions|
We conduct a Galactic census of giant HII (GHII) regions, based on theall-sky 6-cm data set of Kuchar & Clark, plus the kinematicdistances obtained by Russeil. From an inspection of mid-infrared (MIR)Mid-course Space Experiment (MSX) and far-IR IRAS Sky Survey Atlasimages, we identify a total of 56 GHII regions in the Milky Way, ofwhich 15 per cent (65 per cent) can be seen at optical (near-IR)wavelengths. The mid to far-IR fluxes from each GHII region aremeasured, and sample the thermal emission from the ubiquitous dustpresent within the exciting clusters of OB stars, arising from theintegrated luminosity of the hot stars heating the cluster dust, forwhich we obtain log L(IR) = 5.5-7.3Lsolar. The MIR 21-μmspatial morphology is presented for each GHII region, and oftenindicates multiple emission sources, suggesting complicated clusterformation. IR colour-colour diagrams are presented, providinginformation concerning the temperature distribution and the opticaldepth of the dust. For the clusters of our study, the dust is notoptically thick to all stellar radiation, thus the measured infraredluminosity is lower than Lbol. As the dust environment of acluster begins to dissipate, the thermal emission and its optical depthought to decrease even before the stars evolve appreciably. We seeevidence of this in our empirical relationship between the integrated IRand Lyman continuum luminosities.
|New infrared star clusters in the southern Milky Way with 2MASS|
We carried out a 2MASS J, H and Ks survey of infrared starclusters in the Milky Way sector 230deg< l <350deg. This zone was the least studied in the literature,previously including only 12 infrared clusters or stellar groups with|b|< 10deg, according to the recent catalogue by Bica etal. (2003). We concentrated efforts on embedded clusters, which arethose expected in the areas of known radio and optical nebulae. Thepresent study provides 179 new infrared clusters and stellar groups,which are interesting targets for detailed future infrared studies. Thesample of catalogued infrared clusters and stellar groups in the Galaxyis now increased by 63%.
|All-Sky 4.85 GHz Flux Measurements of H II Regions|
We present an all-sky flux catalog of 760 H II regions with angularsizes ranging up to 10' at 4.85 GHz. The data were compiled in aself-consistent manner from existing images of the Green Bank andParkes-MIT-NRAO 4.85 GHz radio continuum surveys. Nearly 35% of these HII regions have fluxes measured from these surveys for the first time.We compared our results to the previously published source catalogs thatfit the same data. The new flux measurements agree within 5%--7% ofthese values and fall well within the formal errors. The diameters fallwithin 16% of the previously published fits to the same data, which iswithin the formal uncertainties of these values.
|Long-Slit Spectrophotometry of the H II Regions GUM 38a and GUM 38b|
We present new long-slit spectrophotometric observations in the range3700--7200 Angstroms of the H II regions Gum 38a and Gum 38b (RCW 57).We study the spatial distribution of reddening and excitation throughoutthe complex by means of emission-line intensities. From the strongreddening difference, we confirm that Gum 38a and Gum 38b are twoindividual complexes, the former being in the foreground. We derivechemical abundances in both nebulae, the results of which are similar tothose of the Orion Nebula. This is consistent with the fact that thethree nebulae are located at similar Galactocentric distances. We alsodiscuss the general ionization structure of the complexes based on thespectral properties of several filaments and diffuse emission around thecentral bright knots of Gum 38a and beyond. In particular, we found aninteresting filament with strong [O I] lambda lambda 6300, 6364 lines.
|The Parkes-MIT-NRAO (PMN) surveys. 2: Source catalog for the southern survey (delta greater than -87.5 deg and less than -37 deg)|
We present a catalog of radio sources discovered at a frequency of 4850MHz in the southern zone (delta greater than -87.5 and less than -37deg) of the Parkes-MIT-NRAO (PMN) survey. This survey covers 2.50 sr andcontains 23,277 sources to a flux limit which varies as a function ofdeclination from 20 mJy at the southern survey limit to about 50 mJy atthe northern limit. The new survey increases the number of radio sourcesknown in the area surveyed by a factor of approximately 5 over thosefound by either of the earlier Parkes or Molonglo surveys. We describedour data taking and reduction methods for the PMN survey in a previouspaper. In this paper we tabulate the sources for the southern survey.Instructions are also given for obtaining the data in machine-readableform. Later papers in the series will list objects for other surveyzones and provide analysis of the data.
|A CCD survey of galaxies in the Coma supercluster|
The analysis of 82 V and 43 B CCD frames of disk CGCG galaxies in theComa and Hercules Supercluster region is presented. These observationsrepresent the first step toward the completion of a CCD survey of allspiral galaxies in this region, but by themselves they do not form acomplete sample. Morphology, diameters, magnitudes at the 25th mag/sqarcsec isophote are determined. V band light profiles and two-colorsurface photometry (when available) are presented. The lightconcentration indices of the studied galaxies are found to correlatewith both their Hubble classification and color indices. However, fordisk galaxies, standard concentration indices cannot be used toextrapolate with sufficient accuracy aperture photometrical measurementsto obtain total magnitudes. Color distributions show that, even amongearly-type disk galaxies, there are examples of objects not exhibitingradial color gradients.
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