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THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
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2011 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 740, no 1, 13- p.Article in journal (Refereed) Published
Abstract [en]

The James Webb Space Telescope (JWST) is expected to revolutionize our understanding of the high-redshift universe, and may be able to test the prediction that the first, chemically pristine (Population III) stars are formed with very high characteristic masses. Since isolated Population III stars are likely to be beyond the reach of JWST, small Population III galaxies may offer the best prospects of directly probing the properties of metal-free stars. Here, we present Yggdrasil, a new spectral synthesis code geared toward the first galaxies. Using this model, we explore the JWST imaging detection limits for Population III galaxies and investigate to what extent such objects may be identified based on their JWST colors. We predict that JWST should be able to detect Population III galaxies with stellar population masses as low as similar to 10(5) M(circle dot) at z approximate to 10 in ultra deep exposures. Over limited redshift intervals, it may also be possible to use color criteria to select Population III galaxy candidates for follow-up spectroscopy. The colors of young Population III galaxies dominated by direct starlight can be used to probe the stellar initial mass function (IMF), but this requires almost complete leakage of ionizing photons into the intergalactic medium. The colors of objects dominated by nebular emission show no corresponding IMF sensitivity. We also note that a clean selection of Population III galaxies at z approximate to 7-8 can be achieved by adding two JWST/MIRI filters to the JWST/NIRCam filter sets usually discussed in the context of JWST ultra deep fields.

Place, publisher, year, edition, pages
2011. Vol. 740, no 1, 13- p.
Keyword [en]
dark ages, reionization, first stars, galaxies: high-redshift, stars: Population III
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-69900DOI: 10.1088/0004-637X/740/1/13ISI: 000295256500013OAI: oai:DiVA.org:su-69900DiVA: diva2:479740
Note

authorCount :5

Available from: 2012-01-18 Created: 2012-01-15 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Gravitational lensing as a probe of the first stars and galaxies
Open this publication in new window or tab >>Gravitational lensing as a probe of the first stars and galaxies
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates the potential for detection and identification of primordial stars, galaxies, and supernovae at high redshift.

Simulations indicate that the first Population III stars should appear in minihalos of mass M = 105-106 Msol at z ≈ 10-30. To assess the detectability of these objects, theoretical models of these stars and their surrounding HII regions are used. We assess the plausibility of detection with the upcoming James Webb Space Telescope (JWST), using the gravitational lensing provided by the galaxy cluster MACSJ0717.5+3745. The conclusion is that the detection of these objects is highly improbable but not impossible.

To investigate the prospects of detecting and identifying the first galaxies, the spectral synthesis code Yggdrasil is introduced. According to this code, JWST may be able to detect Population III galaxies with stellar masses as low as 105 Msol at z ≈ 10 in unlensed fields. We find that, over limited redshift intervals, it could be possible to use Hubble Space Telescope (HST) and/or JWST broadband color criteria to single out Population III galaxy candidates.

The prospects of detecting gravitationally lensed Population III galaxies with JWST and HST is investigated. A lower limit to detect ≈1 Population III galaxy of ε ≈ 10-2 (HST/CLASH) and ε ≈ 10-3 (JWST using MACS J0717.5+3745 as lens) is derived, where ε is the baryon fraction converted to Population III stars in a host halo.

By fitting HST/CLASH data to Yggdrasil and comparison grids, two Population III galaxy candidates are discovered. These two candidates are the first Population III galaxy candidates discovered at z > 6.5. A highly-magnified and doubly lensed extremely high-redshift (z ≈ 7.8) object is also identified.

Finally the prospects of detecting core-collapse (CC) supernovae (SN) from the first galaxies at z ≈ 5-12 are investigated. The prediction is that no primordial SN is detectable, but 2-3 CC SN should be discovered by the HST/CLASH.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2015. 54 p.
Keyword
stars: Population III, first stars, Galaxies: high-redshift, Galaxies: Population III, dark ages, reionization, techniques: photometric
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-110070 (URN)978-91-7649-068-6 (ISBN)
Public defence
2015-01-30, FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 6: Submitted. Paper 7: Manuscript.

Available from: 2015-01-08 Created: 2014-12-05 Last updated: 2015-01-12Bibliographically approved

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