Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Gravitational lensing as a probe of the first stars and galaxies
Stockholm University, Faculty of Science, Department of Astronomy.
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 [en]
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: urn:nbn:se:su:diva-110070ISBN: 978-91-7649-068-6 (print)OAI: oai:DiVA.org:su-110070DiVA: diva2:769052
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
List of papers
1. THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES
Open this publication in new window or tab >>THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES
Show others...
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.

Keyword
dark ages, reionization, first stars, galaxies: high-redshift, stars: Population III
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-69900 (URN)10.1088/0004-637X/740/1/13 (DOI)000295256500013 ()
Note

authorCount :5

Available from: 2012-01-18 Created: 2012-01-15 Last updated: 2017-12-08Bibliographically approved
2. The Hubble Space Telescope colours of high-redshift Population III galaxies with strong Lya emission
Open this publication in new window or tab >>The Hubble Space Telescope colours of high-redshift Population III galaxies with strong Lya emission
2011 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 418, no 1, L104-L108 p.Article in journal (Refereed) Published
Abstract [en]

Population III (pop III) galaxies, made partly or exclusively of metal-free stars, are predicted to exist at high redshifts and may produce very strong Lya emission. A substantial fraction of these Lya photons are likely absorbed in the intergalactic medium at z > 6, but recent simulations suggest that significant Lya emission may be detectable up to z similar to 8.5, i.e. well into the reionization epoch. Here, we argue that high-redshift pop III galaxies with strong Lya emission can be identified in Hubble Space Telescope imaging data because of their unusual colours. We quantify this effect in some of the filters used in Y-band dropout searches for galaxies at z approximate to 8 and find that pop III galaxies with high Lya fluxes may exhibit much bluer J-H colours at z approximate to 8-10 than any normal type of galaxy at these redshifts. This colour signature can arise even if pop III stars account for as little as similar to 10(-3) to 10(-2) of the stellar mass in these galaxies. Some of the anomalously blue objects reported in current Y-band dropout samples do in fact meet the colour criteria for Lya-emitting pop III galaxies.

Keyword
stars: Population III, galaxies: high-redshift, dark ages, reionization, first stars
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-70880 (URN)10.1111/j.1745-3933.2011.01153.x (DOI)000297045700022 ()
Note

authorCount :4

Available from: 2012-01-25 Created: 2012-01-24 Last updated: 2017-12-08Bibliographically approved
3. Detecting gravitationally lensed Population III galaxies with the Hubble Space Telescope and the James Webb Space Telescope
Open this publication in new window or tab >>Detecting gravitationally lensed Population III galaxies with the Hubble Space Telescope and the James Webb Space Telescope
Show others...
2012 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 427, no 3, 2212-2223 p.Article in journal (Refereed) Published
Abstract [en]

Small galaxies consisting entirely of Population III (pop III) stars may form at high redshifts, and could constitute one of the best probes of such stars. Here, we explore the prospects of detecting gravitationally lensed pop III galaxies behind the galaxy cluster J0717.5+3745 (J0717) with both the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST). By projecting simulated catalogues of pop III galaxies at z similar to 715 through the J0717 magnification maps, we estimate the lensed number counts as a function of flux detection threshold. We find that the ongoing HST survey Cluster Lensing And Supernova survey with Hubble (CLASH), targeting a total of 25 galaxy clusters including J0717, potentially could detect a small number of pop III galaxies if similar to 1 per cent of the baryons in these systems have been converted into pop III stars. Using JWST exposures of J0717, this limit can be pushed to similar to 0.1 per cent of the baryons. Ultradeep JWST observations of unlensed fields are predicted to do somewhat worse, but will be able to probe pop III galaxies with luminosities intermediate between those detectable in HST/CLASH and in JWST observations of J0717. We also explain how current measurements of the galaxy luminosity function at z = 710 can be used to constrain pop III galaxy models with very high star formation efficiencies (similar to 10 per cent of the baryons converted into pop III stars).

Keyword
stars: Population III, galaxies: high-redshift, dark ages, reionization, first stars
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-84799 (URN)10.1111/j.1365-2966.2012.22078.x (DOI)000311414800026 ()
Funder
Swedish Research Council, 2011-5349
Note

AuthorCount:9;

Available from: 2013-01-02 Created: 2013-01-02 Last updated: 2017-12-06Bibliographically approved
4. Detection of isolated Population III stars with the James Webb Space Telescope
Open this publication in new window or tab >>Detection of isolated Population III stars with the James Webb Space Telescope
2013 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 429, no 4, 3658-3664 p.Article in journal (Refereed) Published
Abstract [en]

The first Population III stars are predicted to form in minihaloes at z approximate to 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 z = 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 60 M-circle dot Population III star 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.

Keyword
stars: Population III, dark ages, reionization, first stars
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-90800 (URN)10.1093/mnras/sts653 (DOI)000318272600074 ()
Funder
Swedish Research Council, 2011-5349
Note

AuthorCount:4;

Available from: 2013-06-12 Created: 2013-06-11 Last updated: 2017-12-06Bibliographically approved
5. A search for Population III galaxies in CLASH. I. Singly-imaged candidates at high redshift
Open this publication in new window or tab >>A search for Population III galaxies in CLASH. I. Singly-imaged candidates at high redshift
Show others...
(English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357Article in journal (Refereed) Submitted
Abstract [en]

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 Lyα 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 Lyα-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 Lyα 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.

Keyword
Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-110254 (URN)
Available from: 2014-12-10 Created: 2014-12-10 Last updated: 2017-12-05
6. DETECTING ANCIENT SUPERNOVAE AT z ~ 5 - 12 WITH CLASH
Open this publication in new window or tab >>DETECTING ANCIENT SUPERNOVAE AT z ~ 5 - 12 WITH CLASH
Show others...
(English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213Article in journal (Refereed) Submitted
Abstract [en]

Supernovae are important probes of the properties of stars at high redshifts because they can be detected at early epochs and their masses can be inferred from their light curves. Finding the first cosmic explosions in the universe will only be possible with the James Webb Space Telescope, the Wide-Field Infrared Survey Telescope and the next generation of extremely large telescopes. But strong gravitational lensing by massive clusters, like those in the Cluster Lensing and Supernova Survey with Hubble (CLASH), could reveal such events now by magnifying their flux by factors of 10 or more. We find that CLASH will likely discover at least 2 - 3 core-collapse supernovae at 5 < z < 12 and perhaps as many as ten. Future surveys of cluster lenses similar in scope to CLASH by the James Webb Space Telescope might find hundreds of these events at z < 15 - 17. Besides revealing the masses of early stars, these ancient supernovae could also constrain cosmic star formation rates in the era of first galaxy formation.

Keyword
Astrophysics - Cosmology, Extragalactic Astrophysics
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-110259 (URN)
Available from: 2014-12-10 Created: 2014-12-10 Last updated: 2017-12-05
7. A search for Population III galaxies in CLASH. II. A multiply-imaged candidate at z ~ 7.8 behind Abell 2261
Open this publication in new window or tab >>A search for Population III galaxies in CLASH. II. A multiply-imaged candidate at z ~ 7.8 behind Abell 2261
Show others...
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.

Keyword
Galaxies: high-redshift -- dark ages, reionization, first stars -- techniques: photometric
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-110260 (URN)
Available from: 2014-12-10 Created: 2014-12-10 Last updated: 2016-01-29Bibliographically approved

Open Access in DiVA

fulltext(47593 kB)135 downloads
File information
File name FULLTEXT01.pdfFile size 47593 kBChecksum SHA-512
9493cefcea82f67935b337ca2be27a649fb84d79b5ece860f7c8671e2761d346caf5e72ef48ffc055d7771253d97009ba5ebdc7ca09115c3d849832fa7e9e1d5
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Rydberg, Claes-Erik
By organisation
Department of Astronomy
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
Total: 135 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 584 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf