A COHERENT STUDY OF EMISSION LINES FROM BROADBAND PHOTOMETRY: SPECIFIC STAR FORMATION RATES AND [O iii]/Hβ RATIO AT 3 < z < 6

Journal Article · Wed Apr 20 00:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/821/2/122· OSTI ID:22862999

Faisst, A. L.; Capak, P.; Masters, D.; Steinhardt, C. ^[1]; Hsieh, B. C. ^[2]; Laigle, C.; McCracken, H. J. ^[3]; Salvato, M. ^[4]; Tasca, L.; Cassata, P.; Davidzon, I.; Ilbert, O.; Le Fèvre, O. ^[5]; Silverman, J. D. ^[6]; De Barros, S. ^[7]; Hasinger, G. ^[8]

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1. Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)
2. Academia Sinica, Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)
3. Institut d’Astrophysique de Paris, CNRS and UPMC, UMR 7095, 98 bis Boulevard Arago, F-75014, Paris (France)
4. Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85748, Garching bei München (Germany)
5. Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France)
6. Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan)
7. INAF—Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127, Bologna (Italy)
8. Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, HI 96822 (United States)

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){sup 2.4} at z < 2.2 and to (1+z){sup 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.

• OSTI ID: 22862999
• Journal Information: Astrophysical Journal, Vol. 821, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COHERENT RADIATION
COSMIC DUST
EMISSION
IONIZATION
MASS
METALLICITY
MILKY WAY
PHOTOMETRY
RED SHIFT
STAR EVOLUTION
STARS
UNIVERSE