J/ApJ/425/122 IMF 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
HILL J.K., ISENSEE J.E., CORNETT R.H., BOHLIN R.C., O'CONNELL R.W.,
ROBERTS M.S., SMITH A.M., STECHER T.P.
<Astrophys. J. 425, 122 (1994)>
=1994ApJ...425..122H 1994ApJ...425..122H (SIMBAD/NED Reference)
ADC_Keywords: Magellanic Clouds; Associations, stellar; Ultraviolet; Positional
data; Magnitudes
Keywords: Magellanic Clouds - stars: luminosity function, mass function -
open clusters and associations: individual (30 Doradus) -
ultraviolet: stars
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 1615A and 2558A. Stellar masses and extinctions are
estimated for the stars in associations using the evolutionary models
of Schaerer et al. (1993), assuming the age is 4Myr 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 (>15M☉) within the Lucke and Hodge (LH) associations is
γ=-1.08±0.2. Initial masses and extinctions for stars not within
LH associations are estimated assuming that the stellar age is either
4Myr or half the stellar lifetime, whichever is larger. The estimated
slope of the IMF for massive stars not within LH associations is
γ=-1.74±0.3 (assuming continuous star formation), compared with
γ=-1.35, and γ=-1.7±0.5, obtained for the Galaxy by
Salpeter (1955) and Scalo (1986), respectively, and γ=-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.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 58 1563 Observed and fitted stellar data
table2.tex 78 1716 LaTeX table version of table2.dat
aastab.sty 72 115 Style file for table2.tex
environ.tex 77 125 LaTeX environment for table2.tex
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Byte-per-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Star Running number of star
7- 13 F7.1 arcsec X X offset from J2000 fiducial position
RA=5h 38m 44s, Decl.=-69deg 6' 32"
15- 21 F7.1 arcsec Y Y offset from J2000 fiducial position
RA=5h 38m 44s, Decl.=-69deg 6' 32"
24- 28 F5.2 mag m162 B5 band magnitude (1615 A)
31- 35 F5.2 mag m256 A5 band magnitude (2558 A)
38- 40 I3 --- LH Lucke and Hodge association number, or zero
43- 46 F4.1 solMass Mass Fitted mass
49- 52 F4.2 mag E(B-V) Fitted E(B-V) within 30 Dor
55- 58 F4.2 mag rms rms magnitude difference between the
observations and the best-fit model
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References:
Fitzpatrick E.L. 1985, ApJ 299, 219
Garmany C.D., Conti P.S. & Chiosi C. 1982 ApJ 263, 777
Hill J.K. et al. 1993, ApJ 413, 604
Salpeter E.E. 1955, ApJ 121, 161
Scalo J.M. 1986, Fund. Cosmic Phys. 11, 1
Schaerer D. et al. 1993, A&AS 98, 523
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Origin: AAS CD-ROM series, Volume 2, 1994
(End) Lee Brotzman [ADS] 09-May-1994, Patricia Bauer [CDS] 25-Oct-1994