Ultraviolet emission lines in young low-mass galaxies at z ≃ 2: Physical properties and implications for studies at z > 7

Daniel P Stark, Johan Richard, Brian Siana, Stéphane Charlot, William R. Freeman, Julia Gutkin, Aida Wofford, Brant E Robertson, Rahman Amanullah, Darach Watson, Bo Milvang-jensen

Research output: Contribution to journalArticle

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Abstract

We present deep spectroscopy of 17 very low mass (M* ≃ 2.0 × 106-1.4 × 109 M) and low luminosity (MUV ≃-13.7 to -19.9) gravitationally lensed galaxies in the redshift range z ≃ 1.5-3.0. Deep rest-frame ultraviolet spectra reveal large equivalent width emission from numerous emission lines (N IV], OIII], CIV, Si III], CIII]) which are rarely seen in individual spectra of more massive star-forming galaxies. C III] is detected in 16 of 17 low-mass starforming systems with rest-frame equivalent widths as large as 13.5Å. Nebular C IV emission is present in the most extreme C III] emitters, requiring an ionizing source capable of producing a substantial component of photons with energies in excess of 47.9 eV. Photoionization models support a picture whereby the large equivalent widths are driven by the increased electron temperature and enhanced ionizing output arising from metal-poor gas and stars (0.04-0.13 Z), young stellar populations (6-50 Myr), and large ionization parameters (logU = -2.16 to -1.84). The young ages implied by the emission lines and continuum spectral energy distributions (SEDs) indicate that the extreme line emitters in our sample are in the midst of a significant upturn in their star formation activity. The low stellar masses, blue UV colours, and large specific star formation rates of our sample are similar to those of typical z ≳ 6 galaxies. Given the strong attenuation of Lya in z ≳ 6 galaxies, we suggest that CIII] is likely to provide our best probe of early star-forming galaxies with ground-based spectrographs and one off the most efficient means of confirming z ≳ 10 galaxies with the James Webb Space Telescope.

Original languageEnglish (US)
Pages (from-to)3200-3220
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume445
Issue number3
DOIs
StatePublished - Sep 5 2014

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ultraviolet emission
physical property
physical properties
galaxies
young population
emitters
early stars
energy
James Webb Space Telescope
ionization
spectroscopy
probe
ultraviolet spectra
star formation rate
spectral energy distribution
stellar mass
massive stars
electron
spectrographs
young

Keywords

  • Cosmology: observations
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: high-redshift

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Ultraviolet emission lines in young low-mass galaxies at z ≃ 2 : Physical properties and implications for studies at z > 7. / Stark, Daniel P; Richard, Johan; Siana, Brian; Charlot, Stéphane; Freeman, William R.; Gutkin, Julia; Wofford, Aida; Robertson, Brant E; Amanullah, Rahman; Watson, Darach; Milvang-jensen, Bo.

In: Monthly Notices of the Royal Astronomical Society, Vol. 445, No. 3, 05.09.2014, p. 3200-3220.

Research output: Contribution to journalArticle

Stark, DP, Richard, J, Siana, B, Charlot, S, Freeman, WR, Gutkin, J, Wofford, A, Robertson, BE, Amanullah, R, Watson, D & Milvang-jensen, B 2014, 'Ultraviolet emission lines in young low-mass galaxies at z ≃ 2: Physical properties and implications for studies at z > 7', Monthly Notices of the Royal Astronomical Society, vol. 445, no. 3, pp. 3200-3220. https://doi.org/10.1093/mnras/stu1618
Stark, Daniel P ; Richard, Johan ; Siana, Brian ; Charlot, Stéphane ; Freeman, William R. ; Gutkin, Julia ; Wofford, Aida ; Robertson, Brant E ; Amanullah, Rahman ; Watson, Darach ; Milvang-jensen, Bo. / Ultraviolet emission lines in young low-mass galaxies at z ≃ 2 : Physical properties and implications for studies at z > 7. In: Monthly Notices of the Royal Astronomical Society. 2014 ; Vol. 445, No. 3. pp. 3200-3220.
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abstract = "We present deep spectroscopy of 17 very low mass (M* ≃ 2.0 × 106-1.4 × 109 M⊙) and low luminosity (MUV ≃-13.7 to -19.9) gravitationally lensed galaxies in the redshift range z ≃ 1.5-3.0. Deep rest-frame ultraviolet spectra reveal large equivalent width emission from numerous emission lines (N IV], OIII], CIV, Si III], CIII]) which are rarely seen in individual spectra of more massive star-forming galaxies. C III] is detected in 16 of 17 low-mass starforming systems with rest-frame equivalent widths as large as 13.5{\AA}. Nebular C IV emission is present in the most extreme C III] emitters, requiring an ionizing source capable of producing a substantial component of photons with energies in excess of 47.9 eV. Photoionization models support a picture whereby the large equivalent widths are driven by the increased electron temperature and enhanced ionizing output arising from metal-poor gas and stars (0.04-0.13 Z⊙), young stellar populations (6-50 Myr), and large ionization parameters (logU = -2.16 to -1.84). The young ages implied by the emission lines and continuum spectral energy distributions (SEDs) indicate that the extreme line emitters in our sample are in the midst of a significant upturn in their star formation activity. The low stellar masses, blue UV colours, and large specific star formation rates of our sample are similar to those of typical z ≳ 6 galaxies. Given the strong attenuation of Lya in z ≳ 6 galaxies, we suggest that CIII] is likely to provide our best probe of early star-forming galaxies with ground-based spectrographs and one off the most efficient means of confirming z ≳ 10 galaxies with the James Webb Space Telescope.",
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T1 - Ultraviolet emission lines in young low-mass galaxies at z ≃ 2

T2 - Physical properties and implications for studies at z > 7

AU - Stark, Daniel P

AU - Richard, Johan

AU - Siana, Brian

AU - Charlot, Stéphane

AU - Freeman, William R.

AU - Gutkin, Julia

AU - Wofford, Aida

AU - Robertson, Brant E

AU - Amanullah, Rahman

AU - Watson, Darach

AU - Milvang-jensen, Bo

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N2 - We present deep spectroscopy of 17 very low mass (M* ≃ 2.0 × 106-1.4 × 109 M⊙) and low luminosity (MUV ≃-13.7 to -19.9) gravitationally lensed galaxies in the redshift range z ≃ 1.5-3.0. Deep rest-frame ultraviolet spectra reveal large equivalent width emission from numerous emission lines (N IV], OIII], CIV, Si III], CIII]) which are rarely seen in individual spectra of more massive star-forming galaxies. C III] is detected in 16 of 17 low-mass starforming systems with rest-frame equivalent widths as large as 13.5Å. Nebular C IV emission is present in the most extreme C III] emitters, requiring an ionizing source capable of producing a substantial component of photons with energies in excess of 47.9 eV. Photoionization models support a picture whereby the large equivalent widths are driven by the increased electron temperature and enhanced ionizing output arising from metal-poor gas and stars (0.04-0.13 Z⊙), young stellar populations (6-50 Myr), and large ionization parameters (logU = -2.16 to -1.84). The young ages implied by the emission lines and continuum spectral energy distributions (SEDs) indicate that the extreme line emitters in our sample are in the midst of a significant upturn in their star formation activity. The low stellar masses, blue UV colours, and large specific star formation rates of our sample are similar to those of typical z ≳ 6 galaxies. Given the strong attenuation of Lya in z ≳ 6 galaxies, we suggest that CIII] is likely to provide our best probe of early star-forming galaxies with ground-based spectrographs and one off the most efficient means of confirming z ≳ 10 galaxies with the James Webb Space Telescope.

AB - We present deep spectroscopy of 17 very low mass (M* ≃ 2.0 × 106-1.4 × 109 M⊙) and low luminosity (MUV ≃-13.7 to -19.9) gravitationally lensed galaxies in the redshift range z ≃ 1.5-3.0. Deep rest-frame ultraviolet spectra reveal large equivalent width emission from numerous emission lines (N IV], OIII], CIV, Si III], CIII]) which are rarely seen in individual spectra of more massive star-forming galaxies. C III] is detected in 16 of 17 low-mass starforming systems with rest-frame equivalent widths as large as 13.5Å. Nebular C IV emission is present in the most extreme C III] emitters, requiring an ionizing source capable of producing a substantial component of photons with energies in excess of 47.9 eV. Photoionization models support a picture whereby the large equivalent widths are driven by the increased electron temperature and enhanced ionizing output arising from metal-poor gas and stars (0.04-0.13 Z⊙), young stellar populations (6-50 Myr), and large ionization parameters (logU = -2.16 to -1.84). The young ages implied by the emission lines and continuum spectral energy distributions (SEDs) indicate that the extreme line emitters in our sample are in the midst of a significant upturn in their star formation activity. The low stellar masses, blue UV colours, and large specific star formation rates of our sample are similar to those of typical z ≳ 6 galaxies. Given the strong attenuation of Lya in z ≳ 6 galaxies, we suggest that CIII] is likely to provide our best probe of early star-forming galaxies with ground-based spectrographs and one off the most efficient means of confirming z ≳ 10 galaxies with the James Webb Space Telescope.

KW - Cosmology: observations

KW - Galaxies: evolution

KW - Galaxies: formation

KW - Galaxies: high-redshift

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