The ALMA REBELS Survey. Epoch of Reionization giants: properties of
  dusty galaxies at $z \approx 7$
  We analyse FIR dust continuum measurements for 14 galaxies ($z\approx 7$) in
the ALMA REBELS LP to derive their physical properties. Our model uses three
input data: (a) the UV spectral slope, $\beta$, (b) the observed UV continuum
flux at $1500$A, $F_{\rm UV}$, (c) the observed continuum flux at $\approx
158\mu$m, $F_{158}$, and considers Milky Way (MW) and SMC extinction curves,
along with different dust geometries. We find that REBELS galaxies have
(28-90.5)% of their star formation obscured; the total (UV+IR) star formation
rates are in the range $31.5 < {\rm SFR}/ (M_\odot {\rm yr}^{-1}) < 129.5$. The
sample-averaged dust mass and temperature are $(1.3\pm 1.1)\times 10^7 M_\odot$
and $52 \pm 11$ K, respectively. In some galaxies dust is abundant (REBELS-14,
$M'_d \approx 3.4 \times 10^7 M_\odot$), or hot (REBELS-18, $T'_d \approx 67$
K). The dust distribution is compact ($<0.3$ kpc for 70% of the galaxies). The
dust yield per supernova is $0.1 \le y_d/M_\odot \le 3.3$, with 70% of the
galaxies requiring $y_d < 0.25 M_\odot$. Three galaxies (REBELS-12, 14, 39)
require $y_d > 1 M_\odot$. With the SFR predicted by the model and a MW
extinction curve, REBELS galaxies detected in [CII] nicely follow the local
$L_{\rm CII}-$SFR relation, and are approximately located on the
Kennicutt-Schmidt relation. The sample-averaged gas depletion time is of
$0.11\, y_P^{-2}$ Gyr, where $y_P$ is the ratio of the gas-to-stellar
distribution radius. For some systems a solution simultaneously matching the
observed ($\beta, F_{\rm UV}, F_{158}$) values cannot be found. This occurs
when the index $I_m = (F_{158}/F_{\rm UV})/(\beta-\beta_{\rm int})$, where
$\beta_{\rm int}$ is the intrinsic UV slope, exceeds $I_m^*\approx 1120$ for a
MW curve. For these objects we argue that the FIR and UV emitting regions are
not co-spatial, questioning the use of the IRX-$\beta$ relation.
