Predicted UV properties of very metal-poor starburst galaxies

By A. Raiter, Daniel Schaerer, R. Fosbury. 2010

156 citations recorded by the source corpus.

Aims. We study the expected properties of starburst galaxies in order to provide the point of reference for interpretation of high-z galaxy surveys and of very metal-poor galaxies. We concentrate mainly on the UV characteristics such as the ionizing spectra, the UV continuum, the Lyα and He ii λ1640 line and two-photon continuum emission. Methods. We use evolutionary synthesis models covering metallicities from Pop III to solar and a wide range of IMFs. We also combine the synthetic SEDs with the CLOUDY photoionization code for more accurate predictions of nebular emission, and to study possible departures from case B assumed in the synthesis models. Results. The ionizing fluxes, UV continuum properties, and predicted Lyα and He ii λ1640 line strengths are presented for synthesis models covering a wider range of parameter space than our earlier calculations. Strong departures from case B predictions are obtained for Lyα and 2γ continuum at low metallicities. At low nebular densities both are shown to be enhanced proportionally to the mean energy carried by the Lyman continuum photons emitted by the ionizing source. Larger Lyα equivalent widths are therefore predicted at low metallicity. The He ii λ1640 line can be weaker than case B predicts (in terms of flux as well as the equivalent width) due to its ionization parameter dependence and to the enhanced underlying 2γ continuum. Conclusions. Our results have implications for the interpretation of star-forming metal-poor and/or high redshift galaxies, for galaxies among the Lyα emitters (LAE) and Lyman Break galaxy (LBG) populations, and for searches of Population III stars in the distant Universe.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/83baa0034046689caa5422594f6228392ae6ee25

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Citations in the corpus

AN INTENSELY STAR-FORMING GALAXY AT z ∼ 7 WITH LOW DUST AND METAL CONTENT REVEALED BY DEEP ALMA AND HST OBSERVATIONS (2013, methodology): “Figure 9 shows that the data points of Himiko fall on the tracks of star-formation photoionization models (Raiter et al. 2010) within the measurement errors and the dust-extinction correction uncertainties, and indicates that Lyα emission of Himiko can be explained by the photoionization by massive…”
Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “However, the same signature can be attributed population III stars (e.g. Raiter et al. 2010), and/or galaxies forming stars with a top-heavy initial mass function (IMF, e.g. Malhotra & Rhoads 2002), or stochastic sampling of the IMF (Forero-Romero & Dijkstra 2013).”
THE RELATION BETWEEN STAR FORMATION RATE AND STELLAR MASS FOR GALAXIES AT 3.5 ⩽ z ⩽ 6.5 IN CANDELS (2014, background): “Nebular Continuum Evolutionary synthesis modeling suggests that nebular continuum emission can impact broadband photometry (Leitherer & Heckman 1995; Mollá et al. 2009; Raiter et al. 2010).”
The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, methodology): “The ionising emissivity and spectrum of the star particles is computed from stellar synthesis models for both Pop III (Raiter et al. 2010) and Pop II (Leitherer et al. 1999) stars, taking into account the age and metallicity of the stellar population.”
Extended Lyman α haloes around individual high-redshift galaxies revealed by MUSE (2015, background): “The few extreme EW objects are certainly interesting, and one possibility is very metal-poor underlying stellar populations (e.g. Raiter et al. 2010).”
CEERS Key Paper. I. An Early Look into the First 500 Myr of Galaxy Formation with JWST (2022, background): “Raiter et al. (2010) explored the impact of differing IMFs on the UV luminosity (specifically investigating the conversion from UV luminosity to star formation rate).”
ON THE REDSHIFT EVOLUTION OF THE Lyα ESCAPE FRACTION AND THE DUST CONTENT OF GALAXIES (2010, background): “To explain an increase by a factor ∼ 4 would require a decrease of the average metallicity from solar down to less than 10−3 solar (Raiter et al. 2010), which seems highly unlikely.”
EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, background): “The exact strength of these emission lines is very sensitive to the “details” of the population, such as the upper end of the IMF, the age or star formation history (see more details in e.g. Raiter et al. 2010).”
Star Formation in the Milky Way and Nearby Galaxies (2012, methodology): “These have been estimated by several authors using evolutionary synthesis models (e.g., Smith et al. 2002; Raiter et al. 2010), but the precise dependences are sensitive to the details of the input stellar models, in particular how effects of stellar rotation are modelled.”
THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES (2011, methodology): “We caution, however, that the β parameter does depend on the exact wavelength range sampled (e.g. Raiter et al. 2010b), especially for models involving nebular emission.”
The MUSE Hubble Ultra Deep Field Survey - VIII. Extended Lyman-α haloes around high-z star-forming galaxies (2017, background): “In any case, given that the EW depends on stellar metallicity and initial mass function and can be affected by bursty star formation histories (Schaerer 2003; Raiter et al. 2010), the objects with EW>200Å values may be interpreted without invoking other Lyα production channels.”
The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5 (2023, background): “Such a change would decrease the mass-to-UV-light ratio by factors of up to several ( e.g., Raiter et al. 2010; Zackrisson et al. 2011 ) .”