Ultraviolet emission lines in young low-mass galaxies at z similar or equal to 2: physical properties and implications for studies at z > 7
2014 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 445, no 3, 3200-3220 p.Article in journal (Refereed) Published
We present deep spectroscopy of 17 very low mass (M* similar or equal to 2.0 x 10(6)-1.4 x 10(9) M-circle dot) and low luminosity (M-UV similar or equal to -13.7 to -19.9) gravitationally lensed galaxies in the redshift range z similar or equal to 1.5-3.0. Deep rest-frame ultraviolet spectra reveal large equivalent width emission from numerous emission lines (N IV], O III], C IV, Si III], C III]) which are rarely seen in individual spectra of more massive star-forming galaxies. C III] is detected in 16 of 17 low-mass star-forming systems with rest-frame equivalent widths as large as 13.5 angstrom. 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(circle dot)), young stellar populations (6-50 Myr), and large ionization parameters (log U = -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 greater than or similar to 6 galaxies. Given the strong attenuation of Ly alpha in z greater than or similar to 6 galaxies, we suggest that C III] 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 greater than or similar to 10 galaxies with the James Webb Space Telescope.
Place, publisher, year, edition, pages
2014. Vol. 445, no 3, 3200-3220 p.
galaxies: evolution, galaxies: formation, galaxies: high-redshift, cosmology: observations
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-112898DOI: 10.1093/mnras/stu1618ISI: 000346962900081OAI: oai:DiVA.org:su-112898DiVA: diva2:782974