Star formation at z=1.47 from HiZELS: an Hα+[O ii] double-blind study

This paper presents the results from the first wide and deep dual narrow-band survey to select Hα and [O ii] line emitters at z= 1.47 ± 0.02, exploiting synergies between the United Kingdom Infrared Telescope and the Subaru telescope by using matched narrow-band filters in the H and z′ bands. The Hα...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2012-03, Vol.420 (3), p.1926-1945
Main Authors: Sobral, David, Best, Philip N., Matsuda, Yuichi, Smail, Ian, Geach, James E., Cirasuolo, Michele
Format: Article
Language:English
Subjects:
cosmology: observations
galaxies: evolution
galaxies: high‐redshift
galaxies: luminosity function, mass function
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Summary:This paper presents the results from the first wide and deep dual narrow-band survey to select Hα and [O ii] line emitters at z= 1.47 ± 0.02, exploiting synergies between the United Kingdom Infrared Telescope and the Subaru telescope by using matched narrow-band filters in the H and z′ bands. The Hα survey at z= 1.47 reaches a 3σ flux limit of F Hα≈ 7 × 10−17 erg s−1 cm−2 (corresponding to a limiting star formation rate (SFR) in Hα of ≈7 M⊙ yr−1) and detects ≈200 Hα emitters over 0.7 deg2, while the much deeper [O ii] survey reaches an effective flux of ≈7 × 10−18 erg s−1 cm−2 (SFR in [O ii] of ∼1 M⊙ yr−1), detecting ≈1400 z= 1.47 [O ii] emitters in a matched comoving volume of ∼2.5 × 105 Mpc3. The combined survey results in the identification of 190 simultaneous Hα and [O ii] emitters at z= 1.47. Hα and [O ii] luminosity functions are derived and both are shown to evolve significantly from z∼ 0 in a consistent way. The SFR density of the Universe at z= 1.47 is evaluated, with the Hα analysis yielding ρSFR= 0.16 ± 0.05 M⊙ yr−1 Mpc−3 and the [O ii] analysis ρSFR= 0.17 ± 0.04 M⊙ yr−1 Mpc−3. The measurements are combined with other studies, providing a self-consistent measurement of the star formation history of the Universe over the last ∼11 Gyr. By using a large comparison sample at z∼ 0.1, derived from the Sloan Digital Sky Survey (SDSS), [O ii]/Hα line ratios are calibrated as probes of dust extinction. Hα emitters at z∼ 1.47 show on average A Hα≈ 1 mag, the same as found by SDSS in the local Universe. It is shown that although dust extinction correlates with SFR, the relation evolves by about ∼0.5 mag from z∼ 1.5 to ∼0, with local relations overpredicting the dust extinction corrections at high z by that amount. Stellar mass is found to be a much more fundamental extinction predictor, with the same relation between mass and dust extinction being valid at both z∼ 0 and ∼1.5, at least for low and moderate stellar masses. The evolution in the extinction-SFR relation is therefore interpreted as being due to the evolution in median specific SFRs over cosmic time. Dust extinction corrections as a function of optical colours are also derived and shown to be broadly valid at both z∼ 0 and ∼1.5, offering simpler mechanisms for estimating extinction in moderately star-forming systems over the last ∼9 Gyr.
ISSN:0035-8711
1365-2966
DOI:10.1111/j.1365-2966.2011.19977.x