Abstract
We present Atacama Large Millimeter/Submillimeter Array observations of
the rest-frame far-infrared (FIR) dust continuum emission of six bright
Lyman-break galaxies (LBGs) at z ≃ 7. One LBG is detected
(5.2σ at peak emission), whilst the others remain individually
undetected at the 3σ level. The average FIR luminosity of the
sample is found to be L_FIR ˜eq 2 × 10^{11} L_{⊙},
corresponding to an obscured star formation rate (SFR) that is
comparable to that inferred from the unobscured UV emission. In
comparison to the infrared excess (IRX =L_FIR/L_UV)-β relation, our
results are consistent with a Calzetti-like attenuation law (assuming a
dust temperature of T = 40-50 K). We find a physical offset of 3 kpc
between the dust continuum emission and the rest-frame UV light probed
by Hubble Space Telescope imaging for galaxy ID65666 at
z=7.17^{+0.09}_{-0.06}. The offset is suggestive of an inhomogeneous
dust distribution, where 75 per cent of the total star formation
activity (SFR ˜eq 70 M_{⊙}/yr) of the galaxy is completely
obscured. Our results provide direct evidence that dust obscuration
plays a key role in shaping the bright end of the observed rest-frame UV
luminosity function at z ≃ 7, in agreement with cosmological galaxy
formation simulations. The existence of a heavily obscured component of
galaxy ID65666 indicates that dusty star-forming regions, or even entire
galaxies, that are `UV dark' are significant even in the z ≃ 7
galaxy population.
Original language | English |
---|---|
Pages (from-to) | 1631-1644 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 481 |
Issue number | 2 |
DOIs | |
Publication status | Published - 31 Aug 2018 |
Keywords
- galaxies: evolution
- galaxies: high-redshift