Detection of isolated population III stars with the James Webb Space Telescope

The first population III stars are predicted to form in minihalos at a redshift of approximately 10-30. The James Webb Space Telescope (JWST), tentatively scheduled for launch in 2018, will probably be able to detect some of the first galaxies, but whether it will also be able to detect the first stars remains more doubtful. Here, we explore the prospects of detecting an isolated population III star or a small cluster of population III stars down to redshift 2 in either lensed or unlensed fields. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. We find that unlensed population III stars are beyond the reach of JWST, and that even lensed population III stars will be extremely difficult to detect. However, the main problem with the latter approach is not necessarily that the lensed stars are too faint, but that their surface number densities are too low. To detect even one population III star of 60 solar masses when pointing JWST through the galaxy cluster MACS J0717.5+3745, the lensing cluster with the largest Einstein radius detected so far, the cosmic star formation rate of population III stars would need to be approximately an order of magnitude higher than predicted by the most optimistic current models.Comment: 8 pages, 6 figures, 1 table, published in MNRAS. The main change in version 2 is the inclusion of lower redshifts, down to 2. There was also one more SFR comparison model (Tornatore 2007) adde

A search for Population III galaxies in CLASH. I. Singly-imaged candidates at high redshift

Population III galaxies are predicted to exist at high redshifts and may be rendered sufficiently bright for detection with current telescopes when gravitationally lensed by a foreground galaxy cluster. Population III galaxies that exhibit strong Lya emission should furthermore be identifiable from broadband photometry because of their unusual colors. Here, we report on a search for such objects at z > 6 in the imaging data from the Cluster Lensing And Supernova survey with Hubble (CLASH), covering 25 galaxy clusters in 16 filters. Our selection algorithm returns five singly-imaged candidates with Lya-like color signatures, for which ground-based spectroscopy with current 8-10 m class telescopes should be able to test the predicted strength of the Lya line. None of these five objects have been included in previous CLASH compilations of high-redshift galaxy candidates. However, when large grids of spectral synthesis models are applied to the study of these objects, we find that only two of these candidates are significantly better fitted by Population III models than by more mundane, low-metallicity stellar populations.Comment: 18 pages, 10 figures, accepted by Ap

Erratum: Observational constraints on supermassive dark stars

No abstract is available for this article

Finding high-redshift dark stars with the James Webb Space Telescope

The first stars in the history of the Universe are likely to form in the dense central regions of 10^5-10^6 Msolar cold dark matter halos at z=10-50. The annihilation of dark matter particles in these environments may lead to the formation of so-called dark stars, which are predicted to be cooler, larger, more massive and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with the upcoming James Webb Space Telescope (JWST). We find that dark stars at z>6 are intrinsically too faint to be detected by JWST. However, by exploiting foreground galaxy clusters as gravitational telescopes, certain varieties of cool (Teff < 30000 K) dark stars should be within reach at redshifts up to z=10. If the lifetimes of dark stars are sufficiently long, many such objects may also congregate inside the first galaxies. We demonstrate that this could give rise to peculiar features in the integrated spectra of galaxies at high redshifts, provided that dark stars make up at least 1 percent of the total stellar mass in such objects.Comment: 12 pages, 7 figures; v2: matches published versio

Nature and chemical abundances of a sample of Lyman-α emitter objects at high redshift

We built a grid of photoionization models and compiled already available observational emission line intensities (1000 53. Values for C/O abundance ratio derived for the LAEs seem to be consistent with those derived for local star forming objects with similar metallicities, while an overabundance of N/O was found for most of the LAEs.Instituto de Astrofísica de La Plat

Nature and chemical abundances of a sample of Lyman-α emitter objects at high redshift

We built a grid of photoionization models and compiled already available observational emission line intensities (1000 53. Values for C/O abundance ratio derived for the LAEs seem to be consistent with those derived for local star forming objects with similar metallicities, while an overabundance of N/O was found for most of the LAEs.Instituto de Astrofísica de La Plat