Regularity Underlying Complexity: A Redshift-independent Description of the Continuous Variation of Galaxy-scale Molecular Gas Properties in the Mass-star Formation Rate Plane

摘要: Star-forming galaxies (SFGs) display a continuous distribution of specific star formation rates (sSFR) which can be approximated by the superposition two log-normal distributions. The 1st these encompasses main sequence (MS) SFGs, 2nd one rarer population starbursts (SB). We show that sSFR-distribution SBs regarded as result physical process (plausibly merging) taking mathematical form boosting kernel and enhancing activity. explore utility splitting star-forming into MS SB - an approach we term "2-Star Formation Mode" (2-SFM) framework for understanding their molecular gas properties. Variations efficiency (SFE) fractions among SFGs take simple, redshift-independent form, once quantities are normalized to value average galaxy. change in SFE undergoing starburst event scales supra-linearly with SFR-increase, expected mergers. This implies Schmidt-Kennicutt plane separates more clearly loci normal than observed SFR vs. M* space. largest deviations (>10-fold) from MS, like many local ULIRGs, not SBs, but even events progenitors having larger typical galaxies. statistically infer decrease factor 2 3 respect direct progenitors, occur short-term SFR-boosts during internal reservoirs drained quickly is accreted cosmic web. predict variations CO-to-H2 conversion SFR-M* provide evidence higher sSFR distant consequence fraction systems.