CDROM/APJ/V413/P604 Stellar Photometry of 30 Dor (Hill+ 1993) ================================================================================ 30 Doradus: Ultraviolet and Optical Stellar Photometry Jesse K. Hill, Ralph C. Bohlin, Kwang-Ping Cheng, Michael N. Fanelli, Paul Hintzen, Robert W. O'Connell, Morton S. Roberts, Andrew M. Smith, Eric P. Smith, & Theodore P. Stecher <1993, ApJ, 413, 604> =1993ApJ...413..604H ================================================================================ Abstract: Stellar photometry is presented for 314 stars in a 9.7 x 9.7 arcmin field in the 30 Dor nebula centered on R136. Magnitudes are computed from Ultraviolet Imaging Telescope images in up to 4 bands with effective wavelengths from 1615 to 2558 A, and from a ground-based CCD image in the B band. Spectral types and extinctions are estimated using a least-squares technique, based on a spectrophotometric library compiled from IUE spectra. The fit spectral types agree to one library spectral type bin and two luminosity classes with types determined from optical slit spectra, for 34 of 39 non-WR stars. Approximately 35% of the 314 stars are fitted to main-sequence spectral types earlier than B1. Extinction of the more reddened stars in 30 Dor is shown to follow the Fitzpatrick 30 Dor extinction curve combined with a nebular curve of Fitzpatrick and Savage, where E(B-V) for each component is determined by the least-squares fit. Assuming a foreground extinction of E(B-V) = 0.10, average values of the color excess internal to 30 Dor are E(B-V)_F = 0.11 +/- 0.02, from the Fitzpatrick 30 Dor extinction curve component, and E(B-V)_FS = 0.17 +/- 0.17 from the Fitzpatrick and Savage nebular extinction curve component. Most stars within the high surface brightness area centered near R136 have low nebular extinction [E(B-V)_FS < 0.03], while stars outside this area typically have E(B-V)_FS < 0.30. Dust grains following the nebular extinction curve may have been expelled from the central regions of 30 Dor by stellar winds, or stars in the outer regions may be behind or within dust clouds. We also suggest that the difference between the Galactic extinction curve and the Fitzpatrick 30 Dor extinction curve may result from the lower cumulative nucleosynthesis in the LMC and the long time necessary for the component producing the local maximum at 2200 A (presumably carbon) to reach the interstellar medium in the form of grains. Keywords: dust, extinction -- ISM: individual (30 Doradus) -- Magellanic Clouds -- techniques: photometric -- ultraviolet: stars File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table3.dat 54 314 30 Dor Stellar UV and B Photometry table3.tex 68 365 LaTeX version of table3.dat table5.dat 32 314 Fit Spectral Types and Extinctions table5.tex 66 357 LaTeX version of table5.dat aastab.sty 72 115 Required LaTeX style file emviron.tex 77 125 Required LaTeX environments and macros -------------------------------------------------------------------------------- Comments for file: table3.dat -------------------------------------------------------------------------------- Table 3 lists the results of IDL implementations of DAOPHOT algorithms used to locate stars and perform aperture and PSF-fit photometry. Aperture photometry uses an aperture of radius 3.4 arcsec (3 px). PSF-fit photometry uses a 3.4 arcsec fitting radius, with a PSF determined for each image from 12 isolated stars of about the same aperture magnitudes, near the midpoint of the range for the image. The B photometry uses aperture and fitting radii of 1.6 arcsec (2 px). More detailed discussion of the photometry is given in section 3 of the printed paper. Equatorial coordinates of the stars are determined by locating them on the ground-based Stromgren u image, for which an astrometric solution is found using space telescope guide stars as standards. The estimated errors in the positions are less than 1 arcsec relative to the guide star frame. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- UIT Ultraviolet Imaging Telescope (UIT) number 5 1X --- --- Blank 6-12 F7.1 arcsec X R.A. (2000) offset from R136 (= 05:38:42) 13-19 F7.1 arcsec Y Dec. (2000) offset from R136 (= -69:06:01) 20-26 F7.2 mag m162 m162 magnitude in the UIT B5 band 27-33 F7.2 mag m189 []? m189 magnitude in the UIT A2 band 34-40 F7.2 mag m221 []? m221 magnitude in the UIT A4 band 41-47 F7.2 mag m256 []? m256 magnitude in the UIT A5 band 48-54 F7.2 mag B []? B magnitude in the optical B band -------------------------------------------------------------------------------- Comments for file: table5.dat -------------------------------------------------------------------------------- Table 5 contains spectral types and extinctions determined by comparison to a set of IUE standard spectra using a least-squares minimization technique. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- UIT Ultraviolet Imaging Telescope (UIT) number 5-6 2X --- --- Blank 7-14 A8 --- Sp Estimated spectral type 15-20 F6.2 --- E_B-V_F *Estimated F curve E(B-V)_F 21-26 F6.2 --- E_B-V_FS *Estimated FS curve E(B-V)_FS 27-32 F6.2 --- RMS *Estimated rms magnitude difference -------------------------------------------------------------------------------- Notes for file: table5.dat -------------------------------------------------------------------------------- E_B-V_F: Estimated F curve E(B-V)_F (Fitzpatrick 1985, ApJ, 299, 219) E_B-V_FS: Estimated FS curve E(B-V)_FS (Fitzpatrick & Savage, 1984, ApJ, 279, 578) RMS: Estimated rms magnitude differences between the best-fit model and the observations -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 23-Mar-1995