CDROM/APJ/V425/P122 IMFS from UV Stellar Photometry (Hill+ 1994) ================================================================================ Initial Mass Functions from Ultraviolet Stellar Photometry: A Comparison of Lucke and Hodge OB Associations Near 30 Doradus with the Nearby Field Jesse K. Hill, Joan E. Isensee, Robert H. Cornett, Ralph C. Bohlin, Robert W. O'Connell, Morton S. Roberts, Andrew M. Smith, & Theodore P. Stecher <1994, ApJ, 425, 122> =1994ApJ...425..122H ================================================================================ Abstract: UV stellar photometry is presented for 1563 stars within a 40' circular field in the LMC, excluding the 10'x10' field centered on R136 investigated earlier by Hill et al. (1993). Magnitudes are computed from images obtained by the Ultraviolet Imaging Telescope in bands centered at 1615 A and 2558 A. Stellar masses and extinctions are estimated for the stars in associations using the evolutionary models of Schaerer et al. (1993), assuming the age is 4 Myr and that the local LMC extinction follows the Fitzpatrick (1985) 30 Dor extinction curve. The estimated slope of the initial mass function (IMF) for massive stars (>15 Msun) within the Lucke and Hodge (LH) associations is Gamma = -1.08 +/- 0.2. Initial masses and extinctions for stars not within LH associations are estimated assuming that the stellar age is either 4 Myr or half the stellar lifetime, whichever is larger. The estimated slope of the IMF for massive stars not within LH associations is Gamma = -1.74 +/- 0.3 (assuming continuous star formation), compared with Gamma = -1.35, and Gamma = -1.7 +/- 0.5, obtained for the Galaxy by Salpeter (1955) and Scalo (1986), respectively, and Gamma = -1.6 obtained for massive stars in the Galaxy by Garmany, Conti, & Chiosi (1982). The shallower slope of the association IMF suggests that not only is the star formation rate higher in associations, but that the local conditions favor the formation of higher mass stars there. We make no corrections for binaries or incompleteness. Keywords: Magellanic Clouds -- open clusters and associations: individual (30 Doradus) -- stars: luminosity function, mass function -- ultraviolet: stars File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table2.dat 58 1563 Observed and fitted stellar data table2.tex 78 1716 LaTeX table version of table 2 aastab.sty 72 115 Style file for table2.tex environ.tex 77 125 LaTeX environment for table2.tex -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- Star Running number of star 5- 1X --- --- Blank 6-13 F8.1 arcsec X *X offset from J2000 fiducial position 14-21 F8.1 arcsec Y *Y offset from J2000 fiducial position 22-28 F7.2 mag m162 B5 band magnitude (1615 A) 29-35 F7.2 mag m256 A5 band magnitude (2558 A) 36-40 I5 --- LH Lucke and Hodge association number, or zero 41-46 F6.1 Msun Mass Fitted mass 47-52 F6.2 mag E_B-V Fitted E(B-V) within 30 Dor 53-58 F6.2 mag e_E_B-V rms mag. diff. between obs. and best-fit model -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- X, Y: X and Y offsets in arcseconds east and north from the J2000 fiducial position RA = 05h 38m 44s and Dec. = -69d 06m 32s. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 09-May-1994