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Photometric and Spectroscopic Study of Stars in the Field of the Young Open Cluster Roslund 4
We present photometric and spectroscopic observations performed in thefield of the Galactic open cluster Roslund 4, which contains the twocataloged nebulae IC 4954 and IC 4955. UBVRI photometry was carried outin a field of 11'×6' around the clustercenter. Medium-resolution optical spectroscopy has been obtained for 41stars, including previously selected main-sequence and pre-main-sequencecandidate cluster members. Narrowband Hα, [S II], and continuumimages have been secured. The observations allow us the measurement ofdifferent physical parameters for the cluster. Assuming an absorptioncoefficient AV/E(B-V)=3.1 and a reddening slopeE(U-B)/E(B-V)=0.72, we obtain a color excess E(B-V)=1.1+/-0.2 and adistance modulus DM0=11.7+/-0.5. Fitting of isochrones to thecolor-magnitude diagrams gives logage(yr)=7.2+/-0.2, and thespectroscopic measurements provide the value VR=-15.7+/-5.2km s-1 for the heliocentric radial velocity. Among the 41stars with spectroscopic data, 11 stars are probable cluster members onthe basis of their radial velocity, and another 10 are considered aspossible members. Two probable member stars of spectral types A5 and G1show hints of absorption in the Li I 6708 Å line, with respectiveequivalent widths of 0.10 and 0.28 Å, and 22 stars of spectraltypes from B2 to G0 show different degrees of emission in Hα, [NII], and [S II] lines. With the exception of three stars of spectraltype earlier than A0, the emission of which is mainly photospheric, allother emissions seen in Hα and forbidden lines have a nebularorigin. They arise in an ionized cloud that surrounds the cluster and iscausing diffuse emission and, possibly, local variations in theextinction law from star to star. In addition to the stars, spectra ofseveral nebular condensations with relatively higher excitation havebeen analyzed. Two of them have been suggested to be Herbig-Haro (HH)objects. Our spectra indicate that only one of these condensations couldbe considered as an HH object.
| A Photometric and [S II] Survey of the Young Cluster Roslund 4
Optical B- and V-band CCD data have been obtained for the young clusterRoslund 4 in conjunction with a large-scale photometric survey of openclusters. In addition, [S II] and off-line continuum CCD emission-lineimaging data have also been obtained, revealing three regions in thecluster field where shock-excited gas is present. Two Herbig-Haro-likeemission features are found, while a more extended emission feature,along an apparent cloud boundary, may be a result of stellar windsencountering the edge of a molecular cloud. The emission-line featuresare located near IRAS sources with properties consistent withstar-forming regions. A previously published age for Roslund 4 (~10 Myr)would seemingly suggest that shocked gas features should not be presentin the cluster region, but an upper limit on the age (less than 4 Myr)derived from the new photometry is more consistent with their presence.Finally, the distance to Roslund 4 is found to be 1700-2000 pc,considerably closer than the previous published estimate.
| 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
| New infrared star clusters and candidates in the Galaxy detected with 2MASS
A sample of 42 new infrared star clusters, stellar groups and candidateswas found throughout the Galaxy in the 2MASS J, H and especiallyKS atlases. In the Cygnus X region 19 new clusters, stellargroups and candidates were found as compared to 6 such objects in theprevious literature. Colour-Magnitude Diagrams using the 2MASS PointSource Catalogue provided preliminary distance estimates in the range1.0 < dsun < 1.8 kpc for 7 Cygnus X clusters. Towardsthe central parts of the Galaxy 7 new IR clusters and candidates werefound as compared to 61 previous objects. A search for prominent darknebulae in KS was also carried out in the central bulge area.We report 5 dark nebulae, 2 of them are candidates for molecular cloudsable to generate massive star clusters near the Nucleus, such as theArches and Quintuplet clusters.
| Strong molecular line emission associated with small Halpha emission regions.
Not Available
| Radio Emission from Small Galactic Nebulae at 606 MHz
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..115T&db_key=AST
| Radio Emission from Small Galactic Nebulae
Abstract image available at:http://adsabs.harvard.edu/abs/1970AJ.....75.1155T
| Untersuchungen über Reflexionsnebel am Palomar Sky Survey I. Verzeichnis von Reflexionsnebeln
Not Available
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