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A search for Population III galaxies in CLASH. II. A multiply-imaged candidate at z ~ 7.8 behind Abell 2261
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
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2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

While the Lyα emission line has served as an important tool in the study of galaxies at z < 6.5, Lyα emitters (LAE) have proved to be elusive at higher redshifts. If galaxies exhibiting high Lyα equivalent widths exist at z > 6.5, such rare objects may potentially stand out in multiband imaging surveys because of their unusual colors. We have conducted a search for such objects in the Cluster Lensing And Supernova survey with Hubble (CLASH) survey, and here report on the discovery of three gravitationally lensed images of a single LAE candidate behind the Abell 2261 cluster. Model fits to the CLASH broadband photometry suggests very strong Lyα emission (rest-frame Lyα equivalent width EW(Lyα) > 200 Å, prior to any IGM correction) at a redshift of z ≈ 7.8.

Place, publisher, year, edition, pages
2014.
Keyword [en]
Galaxies: high-redshift -- dark ages, reionization, first stars -- techniques: photometric
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-110260OAI: oai:DiVA.org:su-110260DiVA: diva2:770553
Available from: 2014-12-10 Created: 2014-12-10 Last updated: 2016-01-29Bibliographically 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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