The Constant Average Relationship between Dust-obscured Star Formation
  and Stellar Mass from $z=0$ to $z=2.5$
  The total star formation budget of galaxies consists of the sum of the
unobscured star formation, as observed in the rest-frame ultraviolet (UV),
together with the obscured component that is absorbed and re-radiated by dust
grains in the infrared. We explore how the fraction of obscured star formation
depends on stellar mass for mass-complete samples of galaxies at $0<z<2.5$. We
combine GALEX and WISE photometry for SDSS-selected galaxies with the 3D-HST
treasury program and Spitzer/MIPS 24$\mu$m photometry in the well-studied 5
extragalactic CANDELS fields. We find a strong dependence of the fraction of
obscured star formation
($f_{\mathrm{obscured}}$=SFR$_{\mathrm{IR}}$/SFR$_{\mathrm{UV+IR}}$) on stellar
mass, with remarkably little evolution in this fraction with redshift out to
$z$=2.5. 50\% of star formation is obscured for galaxies with
log(M/M$_{\odot}$)=9.4; although unobscured star formation dominates the budget
at lower masses, there exists a tail of low mass extremely obscured
star-forming galaxies at $z>1$. For log(M/M$_{\odot}$)$>$10.5, $>$90\% of star
formation is obscured at all redshifts. We also show that at fixed total SFR,
$f_{\mathrm{obscured}}$ is lower at higher redshift. At fixed mass,
high-redshift galaxies are observed to have more compact sizes and much higher
star formation rates, gas fractions and hence surface densities (implying
higher dust obscuration), yet we observe no redshift evolution in
$f_{\mathrm{obscured}}$ with stellar mass. This poses a challenge to
theoretical models to reproduce, where the observed compact sizes at high
redshift seem in tension with lower dust obscuration.
