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|CCD BVI photometry and Coravel observations of stars in the open cluster NGC2489|
We present CCD BVI photometry for the southern open cluster NGC2489 andits surrounding field. The sample consists of 2182 stars measured in anarea of 13.6 × 13.6 arcmin2, extending down to V ~21.5. These data are supplemented with CORAVEL radial-velocityobservations for seven red giant candidates. A cluster angular radius of6.7 +/- 0.6 arcmin, equivalent to 3.5 +/- 0.3 pc, is estimated from starcounts carried out inside and outside the cluster region. The comparisonof the cluster colour-magnitude diagrams with isochrones of the Padovagroup yields E(B - V) = 0.30 +/- 0.05, E(V - I) = 0.40 +/- 0.05 and V -MV = 12.20 +/- 0.25 for log t = 8.70 (t =500+130-100 Myr) and Z = 0.019. NGC2489 is thenlocated at 1.8 +/- 0.3 kpc from the Sun and 25 pc below the Galacticplane. The analysis of the kinematical data allowed us to confirmcluster membership for six red giants, one of them being a spectroscopicbinary. A mean radial velocity of 38.13 +/- 0.33 km s-1 wasderived for the cluster red giants. The properties of a sample of openclusters aligned along the line of sight of NGC2489 are examined.
|First estimates of the fundamental parameters of the relatively bright Galactic open cluster NGC 5288|
In this paper we present charge-coupled device (CCD) images in theJohnson B and V and Kron-Cousins I passbands for the previouslyunstudied open cluster NGC 5288. The sample consists of 15688 starsreaching down to V~ 20.5. The cluster appears to have a relatively smallbut conspicuous nucleus and a low-density extended coronal region. Starcounts carried out in 25 × 25 pixel2 boxes distributedthroughout the whole observed field allowed us to estimate the angularcore and corona radii as ~1.3 and 6.3arcmin, respectively. Our analysissuggests that NGC 5288 is moderately young and probably more metal-richthan the Sun. Adopting the theoretical metal content Z= 0.040, whichprovides the best global fit, we derive an age of130+40-30Myr. Simultaneously, we have obtainedcolour excesses E(B-V) = 0.75 and E(V-I) = 0.95 and an apparent distancemodulus V-MV= 14.00. The law of interstellar extinction inthe cluster direction is found to be normal. NGC 5288 is located at 2.1+/- 0.3kpc from the Sun beyond the Carina spiral feature and ~7.4kpcfrom the Galactic Centre. The cluster metallicity seems to be compatiblewith the cluster position in the Galaxy, given the recognized radialabundance gradient in the disc. For the first time, in this paper wedetermine the basic parameters for the open cluster NGC 5381, situatedin the same direction as NGC 5288. This determination was reached byusing CCD VI data published almost a decade ago by Pietrzyński etal. (1997) for NGC 5381. The properties of some open clusters alignedalong the line of sight of NGC 5288 are examined. The properties ofclusters of similar ages to NGC 5288 are also looked into. Evidence ispresented that these did not form mainly along the spiral arms butrather in the thin Galactic disc (Z~+/-100pc).
|Distances to eight nearby isolated low-luminosity galaxies|
Eight isolated dwarf galaxies with radial velocities between 350 and 500km/s have been resolved into stars for the first time. Based onphotometry of the brightest blue and red stars, we obtained thefollowing distance estimates (in Mpc) for these galaxies: 6.5 (UGC2684), 6.9 (NGC 2537), 6.8 (UGC 5288), 5.3 (UGC 5423), 6.2 (UGC 5672),7.4 (UGC 5918), 5.4 (NGC 5023), and 5.1 (NGC 5229). A wide variety ofmorphological features is noted in the isolated galaxies underconsideration, which is clearly attributable to a difference in theirstar-formation activity. The median value of individual estimates of theHubble parameter H = V_0/D for these galaxies is 68 km/s per Mpc.
|Uniform survey of clusters in the southern Milky Way.|
Abstract image available at:http://adsabs.harvard.edu/abs/1975AJ.....80...11V
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