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Register a new userThe star-forming main sequence and the contribution of dust-obscured star formation since $zsim4$ from the FUV+IR luminosity functions
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Aldo Rodriguez-Puebla
Publication date
2020
fields
Physics
and research's language is
English
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An analytical approach is proposed to study the evolution of the star-forming galaxy (SFG) main sequence (MS) and the fraction of dust-obscured SF up to $zsim4$. Far-ultraviolet (FUV) and infrared (IR) star formation rates, SFRs, are described as conditional probability functions of $M_{ast}$. We convolve them with the galaxy stellar mass function (GSMF) of SFGs to derive the FUV and IR LFs. The 2 SF modes formalism is used to describe starburst galaxies. By fitting observed FUV and IR LFs, the parametrization of SFR$_{rm FUV}-M_{ast}$ and SFR$_{rm IR}-M_{ast}$ are constrained. Our derived SFR$_{rm FUV+IR}-M_{ast}$ reproduces the evolution of the MS as compared to other observational inferences. At any redshift, we find that the sSFR$_{rm FUV+IR}-M_{ast}$ relation for MS SFGs approaches to a power law at the high-mass end. At lower masses, it bends and eventually the slope sign changes from negative to positive at very low masses. At $zsim0$, this change of sign is at $M_{ast}sim5times10^{8}{rm M}_{odot}$ close to dust-obscured SF regime, $M_{ast}sim6times10^{8}{rm M}_{odot}$. The slope sign change is related to the knee of the FUV LF. Our derived dust-obscured fractions agree with previous determinations at $0leq zleq2.5$. Dust-obscured fractions depend strongly on mass with almost no dependence with redshift at $zgtrsim1.2$. At $zlesssim0.75$ high-mass galaxies become more transparent compared to their high redshift counterparts. On the opposite, low- and intermediate-mass galaxies have become more obscured by dust. The joint evolution of the GSMF and the FUV and IR LFs is a promising approach to study mass growth and dust formation/destruction mechanisms.
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We derive two-dimensional dust attenuation maps at $sim1~mathrm{kpc}$ resolution from the UV continuum for ten galaxies on the $zsim2$ Star-Forming Main Sequence (SFMS). Comparison with IR data shows that 9 out of 10 galaxies do not require further obscuration in addition to the UV-based correction, though our sample does not include the most heavily obscured, massive galaxies. The individual rest-frame $V$-band dust attenuation (A$_{rm V}$) radial profiles scatter around an average profile that gently decreases from $sim1.8$ mag in the center down to $sim0.6$ mag at $sim3-4$ half-mass radii. We use these maps to correct UV- and H$alpha$-based star-formation rates (SFRs), which agree with each other. At masses $<10^{11}~M_{rm sun}$, the dust-corrected specific SFR (sSFR) profiles are on average radially constant at a mass-doubling timescale of $sim300~mathrm{Myr}$, pointing at a synchronous growth of bulge and disk components. At masses $>10^{11}~M_{rm sun}$, the sSFR profiles are typically centrally-suppressed by a factor of $sim10$ relative to the galaxy outskirts. With total central obscuration disfavored, this indicates that at least a fraction of massive $zsim2$ SFMS galaxies have started their inside-out star-formation quenching that will move them to the quenched sequence. In combination with other observations, galaxies above and below the ridge of the SFMS relation have respectively centrally-enhanced and centrally-suppressed sSFRs relative to their outskirts, supporting a picture where bulges are built due to gas `compaction that leads to a high central SFR as galaxies move towards the upper envelope of SFMS.
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