CDROM/APJS/V99/P173 Synth. UV Spectra of Massive Star Pop. (Leitherer+ 1995) ================================================================================ Atlas of Synthetic Ultraviolet Spectra of Massive Star Populations Claus Leitherer, Carmelle Robert, & Timothy M. Heckman <1995, ApJS, 99, 173> =1995ApJS...99..173L ================================================================================ 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 50 Msun 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 5 Myr, 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 60 Msun. 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 approx. 3 Myr. 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. Keywords: atlases -- stars: early-type -- stars: mass-loss -- stars: Wolf-Rayet -- ultraviolet: stars Description: The data for this paper were supplied as 144 files with names of the form: Ti_j_k_p00.x. 'p00' stands for `plus 0.0', indicating a metallicity of solar. Future models will have non-solar abundances. 'i', 'j', 'k', and 'x' were coded numbers and letters indicating the age, upper cut-off mass, IMF exponent, and burst or continuous star formation, respectively. These file names were not compatible with the ISO 9660 CD-ROM file system standard. The files were renamed to 'model001.dat', 'model002.dat', ... 'model144.dat', and the model parameter values and the new file names were written to a separate table, 'models.dat', so that users can correlate the model parameters with each file. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- models.dat 31 144 List of model parameters for the atlas model001.dat 43 860 First of 144 models in the atlas ... . . . model144.dat 39 860 Last of 144 models in the atlas -------------------------------------------------------------------------------- Byte-by-byte Description of file: models.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1-12 A12 --- File *File name of this model 13-14 2X --- --- Blank 15-17 F3.1 Myr Age [1.0-9.0] Age, in intervals of 1.0 Myr 18-19 2X --- --- Blank 20-22 I3 Msun Mass [30-100] Upper cut-off mass, 30, 40, 60, 80 or 100 Msun 23-24 2X --- --- Blank 25-28 F4.2 --- IMF [1.50-3.75] IMF exponents, 1.50, 2.35, 3.00 or 3.75 29-30 2X --- --- Blank 31 A1 --- Form [bc] Indicator for burst (b) or continuous (c) star formation -------------------------------------------------------------------------------- Notes for file: models.dat -------------------------------------------------------------------------------- File: The file names are 'model001.dat', 'model002.dat', ... 'model144.dat'. 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 files: model001.dat ... model144.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 D9.1 yr Age Age 10-18 D9.3 0.1nm Lambda Wavelength 19-28 D10.5 kW/m Lum Luminosity (erg/s/A) 29-43 D15.7 --- Spectrum Normalized spectrum, which is plotted in the figures in the printed paper. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 29-Aug-95