A Study of the Gas-Star Formation Relation over Cosmic Time - Astrophysics > Cosmology and Nongalactic AstrophysicsReportar como inadecuado




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Abstract: We use the first systematic data sets of CO molecular line emission in z~1-3normal star forming galaxies for a comparison of the dependence ofgalaxy-averaged star formation rates on molecular gas masses at low and highredshifts, and in different galactic environments. Although the current high-zsamples are still small and biased toward the luminous and massive tail of theactively star-forming -main-sequence-, a fairly clear picture is emerging.Independent of whether galaxy integrated quantities or surface densities areconsidered, low- and high-z SFG galaxy populations appear to follow similarmolecular gas-star formation relations with slopes 1.1 to 1.2. Thegas-depletion time scale in these SFGs grows from 0.5 Gyrs at z~2 to 1.5 Gyrsat z~0. Because star formation depletion times are significantly smaller thanthe Hubble time at all redshifts sampled, star formation rates and gasfractions are set by the balance between gas accretion from the halo andstellar feedback. In contrast, very luminous gas rich major mergers at bothlow-z and high-z produce on average 4 to10 times more far-infrared luminosityper unit gas mass. Only some fraction of this difference can be explained byuncertainties in gas-mass or luminosity estimators; much of it must beintrinsic. The most likely interpretation is that the star formation relationis driven by global dynamical effects. For a given mass, the more compactmerger systems produce stars more rapidly because their gas clouds are morecompressed with shorter dynamical times, so that they churn more quicklythrough the available gas reservoir than the typical normal disk galaxies. Whenthe dependence on galactic dynamical time scale is explicitly included, diskgalaxies and mergers appear to follow similar gas to star-formation relations.The mergers may be forming stars at slightly higher efficiencies than thedisks.



Autor: R.Genzel, L.J.Tacconi, J.Gracia-Carpio, A.Sternberg, M.C.Cooper, K.Shapiro, A.Bolatto, N.Bouche, F.Bournaud, A.Burkert, F.Combes,

Fuente: https://arxiv.org/







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