J/ApJ/466/254 NIR Imaging of R136 in 30 Dor (Brandl+ 1996)
Adaptive optics near-infrared imaging of R136 in 30 Doradus: the stellar
population of a nearby starburst.
Brandl B., Sams B.J., Bertoldi F., Eckart A., Genzel R., Drapatz S.,
Hofmann R., Loewe M., Quirrenbach A.
<Astrophys. J. 466, 254 (1996)>
=1996ApJ...466..254B 1996ApJ...466..254B
ADC_Keywords: Stars, dwarfs ; Photometry, UBVRIJKLMNH
Keywords: H II regions - infrared: stars - ISM: individual (30 Doradus) -
Magellanic Clouds - stars: early type - techniques: image processing
Abstract:
We report 0.15" resolution near-infrared (NIR) imaging of R136, the
central region of 30 Doradus in the Large Magellanic Cloud. Our
12.8"x12.8" images were recorded with the MPE camera SHARP II at the
3.6m ESO telescope, using the adaptive optics system COME ON+. The
high spatial resolution and sensitivity (20th magnitude in K) of our
observations allow our H- and K-band images to be compared and
combined with recent Hubble Space Telescope (HST) WFPC2 data of R136.
We fit theoretical models with variable foreground extinction to the
observed magnitudes of ∼1000 stars (roughly half of which were
detected in HST and NIR bands) and derive the stellar population in
this starburst region. We find no red giants or supergiants; however,
we detect ∼110 extremely red sources which are probably young,
pre-main-sequence low- or intermediate-mass stars. We obtained
narrow-band images to identify known and new Wolf-Rayet stars by their
He II (2.189um) and BrGamma (2.166um) emission lines. The presence
of W-R stars and absence of red supergiants narrow the cluster age to
3-5Myr, while the derived ratio of W-R to O stars of 0.05 in the
central region favors an age of ∼3.5Myr, with a relatively short
starburst duration. For the O stars, the core radius is found to be
0.1pc and appears to decrease with increasing stellar mass. The slope
of the mass function is Gamma=-1.6 on average, but it steepens with
increasing distance from the cluster center from Gamma=-1.3 in the
inner 0.4pc to Gamma=-2.2 outside 0.8pc for stars more massive
than 12 Msun. The radial variation of the mass function reveals strong
mass segregation that is probably due to the cluster's dynamical
evolution.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 51 971 The 971 main sequence stars in our field of view
(YSO candidates and WR stars were excluded)
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Byte-per-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Star Star number from Hunter et al.
(1995ApJ...488..179H 1995ApJ...488..179H)
8- 10 I3 pix Xpos X position on detector (512x512 grid)
13- 15 I3 pix Ypos Y position on detector (512x512 grid)
18- 23 F6.2 mag Umag *?=-99.99 U magnitude
25- 30 F6.2 mag Vmag *?=-99.99 V magnitude
32- 37 F6.2 mag Imag *?=-99.99 I magnitude
39- 44 F6.2 mag Hmag *?=-99.99 H magnitude
46- 51 F6.2 mag Kmag *?=-99.99 K magnitude
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Note on Umag, Vmag, Imag:
The U, V & I band magnitudes were converted from WFPC2 magnitudes
according the the relations in Hunter et al. (1995ApJ...488..179H 1995ApJ...488..179H).
Extinction was not taken into account.
Note on Hmag, Kmag:
The H & K magnitudes were derived from the authors' observations
with adaptive optics. Extinction is not taken into account.
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Origin: AAS CD-ROM series, Volume 7, 1996 Lee Brotzman [ADS] 22-Oct-96
(End) [CDS] 03-Feb-1997