Main sequence of star forming galaxies beyond the Herschel confusion
  limit
  Deep far-infrared (FIR) cosmological surveys are known to be affected by
source confusion, causing issues when examining the main sequence (MS) of star
forming galaxies. This has typically been partially tackled by the use of
stacking. However, stacking only provides the average properties of the objects
in the stack. This work aims to trace the MS over $0.2\leq z<6.0$ using the
latest de-blended Herschel photometry, which reaches $\approx10$ times deeper
than the 5$\sigma$ confusion limit in SPIRE. This provides more reliable star
formation rates (SFRs), especially for the fainter galaxies, and hence a more
reliable MS. We built a pipeline that uses the spectral energy distribution
(SED) modelling and fitting tool CIGALE to generate flux density priors in the
Herschel SPIRE bands. These priors were then fed into the de-blending tool XID+
to extract flux densities from the SPIRE maps. Multi-wavelength data were
combined with the extracted SPIRE flux densities to constrain SEDs and provide
stellar mass (M$_{\star}$) and SFRs. These M$_{\star}$ and SFRs were then used
to populate the SFR-M$_{\star}$ plane over $0.2\leq z<6.0$. No significant
evidence of a high-mass turn-over was found; the best fit is thus a simple
two-parameter power law of the form
log(SFR)$=\alpha[$log(M$_{\star})-10.5]+\beta$. The normalisation of the power
law increases with redshift, rapidly at $z\lesssim1.8$, from $0.58\pm0.09$ at
$z\approx0.37$ to $1.31\pm0.08$ at $z\approx1.8$. The slope is also found to
increase with redshift, perhaps with an excess around $1.8\leq z<2.9$. The
increasing slope indicates that galaxies become more self-similar as redshift
increases, implying that the specific SFR of high-mass galaxies increases over
$z=0.2$ to $z=6.0$, becoming closer to that of low-mass galaxies. The excess in
the slope at $1.8\leq z<2.9$, if present, coincides with the peak of the cosmic
star formation history.
