The ALPINE-ALMA [CII] survey: dust attenuation curves at z=4.4-5.5
  There is now ample evidence that dust is already present in abundance at high
z. However, given the faintness of distant galaxies in the optical and the NIR,
datasets are still limited and how the dust affects the emerging radiation of
galaxies at very high redshift is not yet fully understood. Using the ALPINE
survey, our objective is to quantify the dust attenuation properties in
galaxies at z=4.4-5.5, and in particular the shape of their attenuation curve.
Using the CIGALE code, we model the stellar populations and their interaction
with the dust in order to measure some of the physical properties of a
subsample of 23 main-sequence ALPINE galaxies. We find that the attenuation
curves span a broad range of properties, from curves that are much steeper than
the SMC extinction curve, to shallower than the starburst attenuation curve.
The shape of the attenuation curves strongly depends on the V-band attenuation.
Galaxies with the lowest attenuation also present the steepest curves. The
steepness of such curves is probably the consequence of the combination of the
intrinsic physical properties of the dust, the relative distribution of stars
and dust in the interstellar medium, and the differential reddening. The broad
range of attenuation curves found at z~5 shows that no single attenuation curve
is appropriate for main sequence galaxies and that assuming a fixed curve can
lead to large errors, for instance in the interpretation and use of the
IRX-beta diagram, if SED modeling is not feasible. Great caution should be
exercised when correcting high redshift galaxies for the presence of dust using
the UV slope beta as it can affect the estimation of both SFR and stellar mass
even at low V-band attenuation due to the steepness of the attenuation curve.
However, when SED modeling can be used, the impact of the choice of the
attenuation curve on the SFR and the stellar mass is limited.
