New galactic open cluster candidates from DSS and 2MASS imagery
An inspection of the DSS and 2MASS images of selected Milky Way regionshas led to the discovery of 66 stellar groupings whose morphologies,color-magnitude diagrams, and stellar density distributions suggest thatthese objects are possible open clusters that do not yet appear to belisted in any catalogue. For 24 of these groupings, which we consider tobe the most likely to be candidates, we provide extensive descriptionson the basis of 2MASS photometry and their visual impression on DSS and2MASS. Of these cluster candidates, 9 have fundamental parametersdetermined by fitting the color-magnitude diagrams with solarmetallicity Padova isochrones. An additional 10 cluster candidates havedistance moduli and reddenings derived from K magnitudes and (J-K) colorindices of helium-burning red clump stars. As an addendum, we alsoprovide a list of a number of apparently unknown galactic andextragalactic objects that were also discovered during the survey.
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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 13CO Survey of Molecular Clouds in Gemini and Auriga
A large-scale survey for molecular clouds in 13CO(J = 1-0) was performedtoward the Gemini and Auriga regions (170 deg < l <= 196 deg and-10 deg <= b < 10 deg) with velocity coverages of -30 < VLSR< +30 km s-1 and -20 < VLSR < +40 km s-1 for 170 deg < l<= 188 deg and 188 deg < l <= 196 deg, respectively, by usingthe two 4 m millimeter-wave telescopes at Nagoya University. An area of520 deg2 was covered at an 8' grid spacing with a 2.'7 beam, and 29,250positions were observed. Significant 13CO emission (>=1.2 K km s-1 =3 sigma ) is detected at 1032 positions, and 139 distinct 13CO cloudsare identified. Physical properties such as molecular column density,size, and mass are derived for each cloud. Comparison with known H IIregions and other associated visible objects indicates that 98 of the139 clouds are located at ~2 kpc, while the rest lie at <~ 1 kpc. Thecandidates for protostars are selected from IRAS point sources and 141sources are identified as protostellar candidates associated with the13CO clouds. A statistical study of the 13CO clouds and of thecandidates for protostars shows the following results: 1. The massspectra of the 13CO clouds are well represented by a power law,Ncloud(>=Mcloud) = 1.4 x 104(Mcloud/Mȯ)-0.83 - 1.4 for theclouds at ~2 kpc and Ncloud(>=Mcloud) = 3.5 x102(Mcloud/Mȯ)-0.64 - 2.4 for the rest. 2. The line width, DeltaVcomp, and the size, R, of the 13CO clouds show a power-law relationwith an index 0.24 +/- 0.06, where the dispersion in the fitting isfairly large. 3. A virial analysis made for the 13CO clouds indicatesthat the relation between the virial mass, Mvir, and the mass measuredin 13CO, Mcloud, is aproximated well by (Mvir/Mȯ) = 2.0 x101(Mcloud/Mȯ)0.72, which suggests that smaller clouds tend to bemore weakly bound gravitationally than larger clouds or are dispersingif the external pressure is negligible. This is probably the cuase of asmall index value of the line width-size relation. 4. The luminosityfunction of the IRAS point sources associated with 13CO clouds are wellrepresented by a power law withN_⋆(>=L_⋆)=4.0x102L^{-0.29}_⋆-1.9x10 forthose at ~2 kpc and N_⋆(>=L_⋆)=2.3x10L^{-0.27}_⋆-3.2for the rest. 5. The luminosity of the most luminous IRAS point sourcein a given molecular cloud increases systematically with the mass of theassociated cloud. 6. The 13CO clouds associated with IRAS point sources,which are regarded as ongoing star-forming clouds, tend to be moremassive and larger in size and to have higher column densities thanthose without any sign of star formation. These relations are found tobe consistent with those derived in Cygnus by Dobashi, Bernard, &Fukui and in Cepheus-Cassiopeia by Yonekura et al. In order to study thestar formation activities, we studied the ratio of virial mass and themass measured in 13CO, Mvir/Mcloud, and its relation with starformation. It is clearly seen that the star-forming 13CO clouds have lowMvir/Mcloud, and all the clouds with high Mvir/Mcloud exhibit no sign ofstar formation. This suggests that star formation rarely occurs inclouds with overall kinetic energy higher than the gravitational energy.
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Derivation of the Galactic rotation curve using space velocities
We present rotation curves of the Galaxy based on the space-velocitiesof 197 OB stars and 144 classical cepheids, respectively, which rangeover a galactocentric distance interval of about 6 to 12kpc. Nosignificant differences between these rotation curves and rotationcurves based solely on radial velocities assuming circular rotation arefound. We derive an angular velocity of the LSR of{OMEGA}_0_=5.5+/-0.4mas/a (OB stars) and {OMEGA}_0_=5.4+/-0.5mas/a(cepheids), which is in agreement with the IAU 1985 value of{OMEGA}_0_=5.5mas/a. If we correct for probable rotations of the FK5system, the corresponding angular velocities are {OMEGA}_0_=6.0mas/a (OBstars) and {OMEGA}_0_=6.2mas/a (cepheids). These values agree betterwith the value of {OMEGA}_0_=6.4mas/a derived from the VLA measurementof the proper motion of SgrA^*^.
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Radio Recombination Lines from Inner Galaxy Diffuse Gas. II. The Extended Low-Density Warm Ionized Medium and the ``Worm-ionized Medium''
Abstract image available at:http://adsabs.harvard.edu/abs/1996ApJ...466..191H
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Peculiar motions of OB associations and their associated molecular clouds.
Not Available
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IRAS sources beyond the solar circle. VI. Analysis of the FIR, H_2_O, and CO emission.
For a sample of 1357 IRAS sources with FIR colours of young stellarobjects we have compared the occurrence and properties of H_2_O maser-and ^12^CO(1-0) emission with the observed and derived IRAS parameters.We find that the distribution of differences between the CO and H_2_Ovelocities is a Gaussian with a FWHM of about 11km/s. The mean velocitydifference is nearly zero. The velocity of the peak H_2_O emission isnot at a preferred location within the velocity interval where emissionis detected. The H_2_O maser detection rate increases with both the FIRluminosity and the ^12^CO(1-0) line width: belowlog(L_FIR_/Lsun_)=3.5, less than 10% of the sources showmaser emission, whereas H_2_O is detected towards almost all of thesources above log(L_FIR_/Lsun_)=4.5. For the sources withH_2_O maser emission, the average CO line width (FWHM about 5.0km/s) isapproximately twice as large as for those without detected H_2_Oemission, an effect which is independent of the sources' FIR luminosity.However a significant fraction of sources with no detected H_2_Oemission still have line widths larger than 1.9km/s, the median valuefor the quiescent gas not associated with the IRAS sources. The maximumH_2_O maser luminosity at each FIR luminosity is proportional to L_FIR_:L_H_2_O_/Lsun_=10^-7.4^(L_FIR_/Lsun_). In IRAScolour-colour plots, sources can be distinguished in maser-like andnon-maser-like sources according to their CO line widths and FIRluminosity. At a given L_FIR_ the maximum T^*^_A_ found for ^12^CO(1-0)decreases with distance from the Sun, likely due to beam fillingeffects. Few sources with maser emission have T^*^_A_ below 7.5K, whenobserved with the IRAM 30-m telescope. There is no difference in themaximum T^*^_A_ of sources with maser-like and non-maser-like IRAScolours. We have derived the intrinsic luminosity- and mass distributionof sources with (non)-maser-like IRAS colours, correcting forincompleteness effects at lower luminosities. The slope of the IMF forsources with maser-like colours and mass larger than 10Msun_is found to be -2.8+/-0.3.
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The Velocity Field of the Outer Galaxy
Abstract image available at:http://adsabs.harvard.edu/abs/1993A&A...275...67B
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Eine Beobachtungsnacht im Herbst.
Not Available
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Investigation of the open star cluster Stock 8
Photographic UBV photometry for 1000 stars brighter than V = 16.0 m wascarried out in a region of Stock 8. The cluster size, the extinction oflight in the direction of the cluster, and the distance are derived. Thedifferential luminosity function is constructed, and the cluster age andmass are estimated.
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IRAS sources beyond the solar circle. II - Distribution in the Galactic warp
The shape of the outer Galaxy derived from the distribution of molecularclouds with embedded IRAS sources is compared with the shape revealed byH I observations. Of the 1302 selected IRAS sources, 1077 revealed CO J= 1-0 emission and subsequently provided a kinematic distance. COemission is found at velocities as extreme as 110 km/s, corresponding toheliocentric distances of 15 kpc or galactocentric distances of 20 kpc.The ensemble of clouds features the same warped shape and flaringthickness as shown by the outer-Galaxy H I gas layer. The distributionof IRAS sources is found to end more abruptly at large R than that of HI.
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Fabry-Perot H-alpha observations of Galactic H II regions
The radial velocity and linewidth of H-alpha emission from 284 objectslisted in Galactic H II region catalogs were observed using aFabry-Perot spectrometer. A few of these objects are supernova remnantsor planetary nebula. The rest of this sample encompasses most of the HII regions that are visible optically from the Northern Hemisphere.These observations are compared to previous H-alpha observations as wellas to radio recombination line and CO observations. The averageradial-velocity difference V(CO) - V(H-alpha) is 0.50 + or - 0.48 km/sand the (1-sigma) dispersion is 6.44 km/s. The implications of thesevalues are discussed in terms of a very simple kinematic and extinctionH II region model. Total H-alpha luminosities for the sample areestimated, and the Galactic H II region luminosity function is comparedto that recently found for other galaxies.
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The rotation curve of the Milky Way to 2 R(0)
A unified analysis of the Galactic rotation curve is presented using H ICO, and spectrophotometric data obtained in the northern hemisphere areused to determine the rotation curve from R = 3-17 kpc. A number ofdifferent functional forms are examined to fit the data, and the errorsand uncertainties that go into its determination are discussed. Theresults are compared with nine recent studies of the rotation curve, andspecific recommendations are made on the choice of curves to use inkinematic studies and mass modeling.
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Kinematics of molecular clouds. II - New data on nearby giant molecular clouds
The best currently available data on positions, distances, andvelocities of giant molecular clouds within 3 kpc of the sun areanalyzed to yield a one-dimensional rms cloud-to-cloud velocitydispersion of 7.8 +0.6, -0.5. Velocity dispersion is defined here as theroot mean square of cloud peculiar velocities, a quantity which includessmall-scale streaming. It is argued that this value for the velocitydispersion is pausible, based on examples of clouds whose velocitiescannot be explained purely by galactic rotation. The mean motion ofnearby molecular clouds is drifting by about 4 km/s with respect to theLSR.
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Kinematics of star forming regions
The cubic approximation of a general two-dimensional velocity field isused to study the radial velocities of 218 star forming regions up to 10kpc from the sun. It is found that departures from the Galactic circularflow are generally related to complexes of star forming regions 1-2 kpcin size. It is suggested that complexes are a consequence of clumpedstar formation and subsequent expansion of multisupernova remnants. Theresults imply that the negative departure from circular motion observedin complexes P(1)-P(4) may be due to the influence of the Perseus spiralarm.
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An optical spiral arm beyond the Perseus arm
In the second galactic quadrant, optical spiral arm tracers have beencollected in a systematic literature search. A uniform reduction of thedata led to the detection of a distinct structure (probably a spiralarm) beyond the Perseus arm that is separated by a statisticallysignificant gap from the latter.
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Young stellar-gas complexes in the Galaxy
It is found that about 90 percent of OB-associations and o-b2 clusterssituated within 3 kpc of the sun can be united into complexes withdiameters of 150-700 pc. Almost all of these clusters contain giantmolecular clouds with a mass greater than about 100,000 solar masses. Anumber of complexes are associated with giant H I clouds; a few of thesmall complexes are situated in the HI caverns. The concentration ofOB-associations and young clusters in star complexes attests to theircommon origin in the supergiant gaseous clouds.
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An HCN J = 1-0 line survey of molecular clouds associated with H II regions from the Sharpless catalog - Results of observations
Not Available
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Kinematics of molecular clouds. I - Velocity dispersion in the solar neighborhood
The rms velocity dispersions of molecular clouds within 3 kpc arecalculated on the basis of published data. Observations of the 1-0transition of CO (Stark, 1979) in the region l = 180 deg, b = -9 to +8deg are analyzed for clouds of mass 100-10,000 solar mass; data on giantclouds (10,000-316,000 solar mass) are taken from the catalog of Blitzet al. (1982). The results are presented in graphs and tables. Theone-dimensional dispersions for the low-mass and giant clouds are foundto be about 9.1 and 6.6 km/s, respectively, with near constancy overseveral orders of magnitude and no equipartition of energy.
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Optical H II regions in the outer galaxy
The results of the CO survey of optical H II regions of Blitz, Fich, andStark (1982) are used to obtain the distribution of H II regions andtheir associated molecular clouds beyond the solar circle. H II regionsare observed in the Milky Way to distances as large as R = 20 kpc, butthere are very few beyond this distance. This limiting distance does notappear to be the result of extinction and appears to be the approximateedge of the stellar disk of the Galaxy. The scale height of H II regionsat 10 kpc is about 100 pc as measured by the z distance dispersion, butthere is considerable variation in this quantity. The smallest scaleheights appear to be related to the major spiral arms. Beyond 12 kpc theH II regions follow the warp of the H I plane. H II regions are smalleron average at large R and few very large H II regions are observedbeyond 12 kpc.
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Decameter observations of the nebulae IC 405 and IC 410
Results are presented of absorption measurements of the H II regions IC405 and IC 410 obtained at five freequencies between 12.6 and 25 MHzwith 0.5-1.0 deg resolution using the UTR-2 radio telescope. The averagenonthermal radiation density of the interstellar medium at 12.6 MHztoward IC 405 is determined to be 135 K/pc, whereas it is found to be 37K/pc toward IC 410. It is found that the kinetic temperature of IC 410is 11,000 K and that the electron density is approximately 12/cu cm.Calculations are presented for several other physical parameters towardthe center of IC 410: optical depth at 25 MHz = 8, emission measure =8,000 pc/cm exp 6, and mass = 3400 solar masses.
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Catalog of CO radial velocities toward galactic H II regions
This is a catalog of 242 molecular cloud complexes which are associatedwith optical H II regions. CO observations were made toward all but fiveof the H II regions in the Sharpless catalog and toward 62 additionalsuspected H II regions, 33 of which are previously uncataloged. Radialvelocities are tabulated for each molecular cloud complex found to beassociated with an H II region. The CO antenna temperature and linewidth are given for the most intense CO line seen toward each source.The catalog also summarizes previous CO observations as well as theoptical distances to the stars exciting the H II regions. Radio-quiet HII regions (those with 1.4 GHz flux densities less than 100 mJy) arefound to be well correlated with objects having no associated CO. A listof kinematically distinct complexes is tabulated to facilitateinvestigations of the motions of the complexes.
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Photometric and spectroscopic investigation of a new carbon star in the Auriga region
Photometric and spectroscopic observations of a carbon star discoverednear the open star cluster Stock 8 in the Auriga region are reported.Coordinates and proper motions are derived, yielding coordinates (1950)of 5 h 24 m 44.11 s right ascension and +37 deg 27 min 46.9 secdeclination, a proper motion in right ascension of 0.0004 s/yr, and aproper motion in declination of -0.002 arcsec/yr. It is shown that thestar is variable and extremely red, that the Swan bands of C2 are quitestrong in its spectrum, and that hydrogen emission lines and spectralfeatures due to CN, CH, and TiO are also present in the spectrum. Lineidentifications are provided, along with evidence that the star isprobably a member of the Stock 8 cluster. It is concluded that thestar's spectrum is consistent with that of a normal carbon star of typeC0 or C1.
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Observations of optical nebulae at 2695 MHz.
Abstract image available at:http://adsabs.harvard.edu/abs/1973A&A....23..117C
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Application of the Density-Wave Theory of Spiral Structure: Shock Formation Along the Perseus Arm
Abstract image available at:http://adsabs.harvard.edu/abs/1972ApJ...173..259R
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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
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Spectral classification and photometry of stars in two HII regions
Not Available
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Radio Emission from Small Galactic Nebulae
Abstract image available at:http://adsabs.harvard.edu/abs/1970AJ.....75.1155T
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A Comparison between Radio and Optical Radial Velocities of H N Regions
Abstract image available at:http://adsabs.harvard.edu/abs/1970A&A.....7..322G
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