J/ApJS/99/173 Synthetic UV spectra of massive stars (Leitherer+ 1995)
Atlas of synthetic ultraviolet spectra of massive star populations
Leitherer C., Robert C., Heckman T.M.
<Astrophys. J. Suppl. Ser. 99, 173 (1995)>
=1995ApJS...99..173L 1995ApJS...99..173L
ADC_Keywords: Stars, early-type ; Spectra, ultraviolet
Keywords: atlases - stars: early-type - stars: mass-loss - stars: Wolf-Rayet -
ultraviolet: stars
Abstract:
An atlas of synthetic ultraviolet spectra of a population of massive
stars is presented. The spectra are based on a stellar library of IUE
high-dispersion spectra of O and Wolf-Rayet stars, coupled to an
evolutionary synthesis code. Later spectral types are included via
low-dispersion spectra. Line profiles of N V lambda 1240, Si IV lambda
1400, C IV lambda 1550, He II lambda 1640, and N IV lambda 1720 have
been computed for star-formation histories and initial mass functions
typically found in starburst regions.
It is found that the lines are sensitive indicators for the presence
or absence of massive stars. C IV lambda 1550 is the strongest stellar
line in the ultraviolet spectrum of a typical starburst. If O stars
with zero-age main-sequence masses above 50M☉ are present, C IV
always shows a P Cygni profile. In the absence of such stars, only a
blue-shifted absorption is present. During later epochs of the
starburst, when late-O/early-B stars dominate, an unshifted
photospheric absorption appears.
Si IV lambda 1400 shows a conspicuous wind profile when luminous O
supergiants are present. A strong P Cygni profile is found only for an
instantaneous burst observed at 3 to 5Myr, which has a top-heavy IMF.
The velocity of the blueshifted absorption is strongly correlated with
the age and the upper cutoff mass (or slope) of the IMF.
N V lambda 1240 traces the most massive stars and behaves rather
similar to Si IV lambda 1400. Its usefulness as an indicator of very
massive stars is limited due to the strong blending effect of the
nearby Ly-alpha line. Nevertheless, strong N V lambda 1240 emission in
a starburst suggests the presence of stars with masses in excess of
60M☉.
He II lambda 1640 and N IV lambda 1720 are produced by very hot and
luminous O and Wolf-Rayet stars. Both lines can have weak absorption
or emission in a typical starburst but are predicted to be observable
only under rare circumstances, such as in an instantaneous burst at
t~3Myr.
The profiles presented in the atlas can be compared to high-quality
ultraviolet observations of galaxies with active star formation in
order to constrain the massive star population. The atlas is published
in its entirety in computer-readable form in the AAS CD-ROM series,
Vol. 5.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
models.all 44 123840 *Spectra for 144 models
--------------------------------------------------------------------------------
Note on models.all: There are 8 combinations of cut-off masses and IMF exponents
for each of the 9 timesteps so that there are 2 x 9 x 8 =144 files for the
two star formation laws (burst and continuous).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: models.all
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Form [bc] b: burst star formation
c: continuous star formation
3- 6 F4.2 --- IMF [1.50-3.75] IMF exponents
(1.50, 2.35, 3.00 or 3.75)
8- 10 I3 solMass Mass [30-100] Upper cut-off mass
(30, 40, 60, 80 or 100 M☉)
12- 14 F3.1 Myr Age [1.0-9.0] Age, in intervals of 1.0 Myr
16- 23 F8.3 0.1nm Lambda [1205.5-1849.75] Wavelength
26- 33 F8.5 [uW/nm] log(Lum) Luminosity per wavelength interval (erg/s/A)
36- 44 F9.7 --- Spectrum Normalized spectrum, which is plotted in
the figures in the printed paper.
--------------------------------------------------------------------------------
Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 29-Aug-95
(End) [CDS] 01-Feb-1996