A Coherent Study of Emission Lines from Broadband Photometry: Specific Star Formation Rates and [O III]/Hβ Ratio at 3 > z > 6
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We measure the Hα and [O III] emission line properties as well as
specific star formation rates (sSFRs) of spectroscopically confirmed 3
<z <6 galaxies in COSMOS from their observed colors versus
redshift evolution. Our model describes consistently the ensemble of
galaxies including intrinsic properties (age, metallicity, star
formation history), dust attenuation, and optical emission lines. We
forward-model the measured Hα equivalent widths (EW) to obtain the
sSFR out to z ∼ 6 without stellar mass fitting. We find a strongly
increasing rest-frame Hα EW that is flattening off above z ∼
2.5 with average EWs of 300-600 Å at z ∼ 6. The sSFR is
increasing proportionally to {(1+z)}2.4 at z <2.2 and to
{(1+z)}1.5 at higher redshifts, indicative of a fast build-up
of mass in high-z galaxies within e-folding times of 100-200 Myr at z
∼ 6. The redshift evolution at z > 3 cannot be fully explained in
a picture of growth driven by cold accretion. We find a progressively
increasing [O III]λ5007/Hβ ratio out to z ∼ 6,
consistent with the ratios in local galaxies selected by increasing
Hα EW (I.e., sSFR). This demonstrates the potential of using
“local high-z analogs” to investigate the spectroscopic
properties and relations of galaxies in the re-ionization epoch.
Original language | English |
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Article number | 122 |
Journal | Astrophysical Journal |
Volume | 821 |
Issue number | 2 |
Number of pages | 15 |
ISSN | 0004-637X |
DOIs | |
Publication status | Published - 1 Apr 2016 |
Externally published | Yes |
- galaxies: evolution, galaxies: high-redshift, galaxies: star formation
Research areas
ID: 240309260