The effect of stellar evolution uncertainties on the rest-frame ultraviolet stellar lines of C iv and He ii in high-redshift Lyman-break galaxies

• Published in: Monthly notices of the Royal Astronomical Society Vol. 419; no. 1; pp. 479 - 489
• Main Authors: Eldridge, John J., Stanway, Elizabeth R.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2012; Wiley-Blackwell
• Subjects: Astronomy; binaries: general; Earth, ocean, space; Exact sciences and technology; galaxies: high redshift; galaxies: starburst; galaxies: stellar content; stars: evolution; stars: Wolf–Rayet; stars: Wolf-Rayet; galaxies: starburst; binaries: general; stars: evolution; galaxies: stellar content; galaxies: high redshift; Rotating star; Red shift; Uncertainty; Mixing; Starburst galaxies; Gravitational lensing; Carbon oxygen ratio; Rapid rotation; Massive stars; Young stars; Emission line; Stellar spectra; Spectroscopy; Stellar content; Ultraviolet spectra; Abundance; Stellar evolution; Wolf-Rayet stars; Spectral analysis; Mass transfer; galaxies: high-redshift; Metallicity; Stellar population; Models
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2011.19713.x

Young, massive stars dominate the rest-frame ultraviolet (UV) spectra of star-forming galaxies. At high redshifts (z > 2), these rest-frame UV features are shifted into the observed-frame optical and a combination of gravitational lensing, deep spectroscopy and spectral stacking analysis allows the stellar population characteristics of these sources to be investigated. We use our stellar population synthesis code Binary Population and Spectral Synthesis (bpass) to fit two strong rest-frame UV spectral features in published Lyman-break galaxy spectra, taking into account the effects of binary evolution on the stellar spectrum. In particular, we consider the effects of quasi-homogeneous evolution (arising from the rotational mixing of rapidly rotating stars), metallicity and the relative abundance of carbon and oxygen on the observed strengths of He iiλ1640 Å and C ivλ1548, 1551 Å spectral lines. We find that Lyman-break galaxy spectra at z ∼ 2-3 are best fitted with moderately sub-solar metallicities, and with a depleted carbon-to-oxygen ratio. We also find that the spectra of the lowest metallicity sources are best fitted with model spectra in which the He ii emission line is boosted by the inclusion of the effect of massive stars being spun-up during binary mass transfer so these rapidly rotating stars experience quasi-homogeneous evolution.