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J/A+A/341/98       The ionizing cluster of 30 Doradus. I.    (Selman+ 1999)

The ionizing cluster of 30 Doradus. I. Internal reddening from NTT photometry. Selman F., Melnick J., Bosch G., Terlevich R. <Astron. Astrophys. 341, 98 (1999)> =1999A&A...341...98S
ADC_Keywords: Clusters, open ; Photometry, UBV Keywords: stars: early-type - stars: luminosity function, mass function - ISM: dust, extinction - galaxies: Magellanic Clouds - Galaxy: open clusters and associations: general Abstract: UBV profile fitting photometry is presented for 1469 stars within 90arcsec of the center of the ionizing cluster of 30 Doradus (NGC 2070). A value of 0.82±0.03 is found for the extinction parameter S=E(U-B)/E(B-V), constant over almost the whole area covered by this research, with some evidence for local variations. Two reddening components can be identified: a smooth and moderate one that increases towards R136, and a clumpy one varying widely across the face of the cluster. The total-to-selective extinction parameter, RV= AV/E(B-V), is found to be in the range of 3.0 to 3.7, consistent with previous determinations. A new visualization tool, the colour-magnitude stereogram, is introduced and used to argue that: (1) the observations imply mass segregation in a dust filled cluster; (2) that there has been continuous dust formation near the cluster core up to the present; and (3) that an insidious systematic error has plagued previous determinations of IMF slopes. A method to obtain an unbiased estimate of the slope is discussed. Astrometric calibration (from B. Skiff): The source images were taken with the ESO NTT 3.6-meter telescope, with a CCD detector at an image scale of 0.13arcsec/pixel in about 0.8arcsec seeing. Positions were determined via a reference net of 26 relatively bright and isolated stars in the region appearing in either UCAC2 (Cat. I/289) or 2MASS (Cat. II/246). The x,y coordinates were transformed using a quadratic least-squares fit; the rms residuals using all the reference stars were 0.50 pixels in RA, and 0.55 pixels in Dec, i.e. 0.097arcsec total. A similar re-reduction of the survey by Parker (1993AJ....106..560P), which overlaps this one, shows that the Selman linkages with Parker stars (column 'P93') are incomplete and contain some errors. Some of these result from the relatively small image scale (0.49arcsec/pixel) and poor seeing (1.2-2.0arcsec) of Parker's data, such that a single Parker star is sometimes resolved into multiple components by Selman. Among bright stars (V ≲ 15) that have been observed for spectral type there are few such errors in the match-up. But among Parker's fainter entries (V ≳ 17) are numerous false detections (clumps in nebulosity) that are incorrectly linked by Selman with true stars a couple of arcseconds from Parker's non-stellar objects. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 05 38 42.8 -69 06 03 RMC 136 = HD 38268 = 30 Dor 05 38 42. -69 05 30 NGC 2070 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 106 1469 UBV photometry of NGC 2070 star members
See also: II/187 : 30 Doradus OB Associations (Parker 1992) J/AJ/107/1054 : 30 Dor region UBV photometry (Malumuth+, 1994) J/ApJ/413/604 : 30 Dor UV and optical photometry (Hill+, 1993) J/A+A/443/851 : Effective temperature of 30 Dor population (Selman+, 2005) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
2- 5 I4 --- Seq Star number 9- 10 I2 h RAh Right Ascension J2000 (hours) (1) 12- 13 I2 min RAm Right Ascension J2000 (minutes) (1) 15- 20 F6.3 s RAs Right Ascension J2000 (seconds) (1) 22 A1 --- DE- Declination J2000 (sign) (1) 23- 24 I2 deg DEd Declination J2000 (degrees) (1) 26- 27 I2 arcmin DEm Declination J2000 (minutes) (1) 29- 33 F5.2 arcsec DEs Declination J2000 (seconds) (1) 36- 41 F6.1 pix xpos X coordinate (2) 43- 48 F6.1 pix ypos Y coordinate (2) 50- 54 I5 --- P93 ?=-1 Id in Parker's catalogue (3) 58- 63 F6.3 mag Vmag Apparent V magnitude 65- 69 F5.3 mag e_Vmag Error in apparent V magnitude 74- 79 F6.3 mag Bmag Apparent B magnitude 81- 85 F5.3 mag e_Bmag Error in apparent B magnitude 89- 94 F6.3 mag Umag Apparent U magnitude 96-100 F5.3 mag e_Umag Error in apparent U magnitude 104-106 F3.1 --- Chi2 Chi2 parameter from IRAF/DAOPHOT II
Note (1): astrometric solution by B. Skiff, see the "Astrometric calibration" section above. Note (2): x axis East to West, y axis South to North, scale of 0.13arcsec/pix; R136 (J2000 position = 05:38:42.8-69:06:03) is located at (x,y) = (456.4,432.3). Note (3): A -1 in this column indicates no match with the catalogue of Parker (1993AJ....106..560P, Cat. II/187). A negative Parker number (smaller than -1) indicates that the star has spectroscopy.
Acknowledgements: Fernando J. Selman <fselman(at)> History: * 18-Dec-1998: Original version with X and Y positions, prepared by Fernando J. Selman [ESO] and Patricia Bauer [CDS] * 04-Mar-2008: Addition of positions from B. Skiff (Lowell Obs.)
(End) Fernando J. Selman [ESO], Patricia Bauer [CDS] Brian Skiff 04-Mar-2008
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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