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A Coherent Study of Emission Lines from Broad-Band Photometry: Specific Star-Formation Rates and OIII/H\beta Ratio at 3 < z < 6

, , , , , , , , , , , , , , , , and . (2016)cite arxiv:1601.07173Comment: 18 pages, 11 figures, 3 tables.

Abstract

We measure the H\alpha and OIII emission line properties as well as specific star-formation rates (sSFR) of spectroscopically confirmed 3<z<6 galaxies in COSMOS from their observed colors vs. 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 H\alpha equivalent-widths (EW) to obtain the sSFR out to z~6 without stellar mass fitting. We find a strongly increasing rest-frame H\alpha EW that is flattening off above z~2.5 with average EWs of 300-600A at z~6. The sSFR is increasing proportional to (1+z)^2.4 at z<2.2 and (1+z)^1.5 at higher redshifts, indicative of a fast mass build-up in high-z galaxies within e-folding times of 100-200Myr at z~6. The redshift evolution at z>3 cannot be fully explained in a picture of cold accretion driven growth. We find a progressively increasing OIIIłambda5007/H\beta ratio out to z~6, consistent with the ratios in local galaxies selected by increasing H\alpha 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.

Description

[1601.07173] A Coherent Study of Emission Lines from Broad-Band Photometry: Specific Star-Formation Rates and [OIII]/H{\beta} Ratio at 3 &lt; z &lt; 6

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