It has recently been suggested1,2 that galaxies in the early Universe could have grown through the accretion of cold gas, and that this may have been the main driver of star formation and stellar mass growth3,4,5. Because the cold gas is essentially primordial, it has a very low abundance of elements heavier than helium (referred to as metallicity). If funnelled to the centre of a galaxy, it will result in the central gas having an overall lower metallicity than gas further from the centre, because the gas further out has been enriched by supernovae and stellar winds, and not diluted by the primordial gas. Here we report chemical abundances across three rotationally supported star-forming galaxies at redshift z ≈ 3, only 2 Gyr after the Big Bang. We find ‘inverse’ gradients, with the central, star-forming regions having lower metallicities than less active ones, which is opposite to what is seen in local galaxies6,7. We conclude that the central gas has been diluted by the accretion of primordial gas, as predicted by ‘cold flow’ models.
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Dekel, A. et al. Cold streams in early massive hot haloes as the main mode of galaxy formation. Nature 457, 451–454 (2009)
Bournaud, F. & Elmegreen, B. G. Unstable disks at high redshift: evidence for smooth accretion in galaxy formation. Astrophys. J. 694, L158–L161 (2009)
Förster Schreiber, N. M. et al. The SINS survey: SINFONI integral field spectroscopy of z ∼ 2 star-forming galaxies. Astrophys. J. 706, 1364–1428 (2009)
Daddi, E. et al. Multiwavelength study of massive galaxies at z ∼ 2. I. Star formation and galaxy growth. Astrophys. J. 670, 156–172 (2007)
Tacconi, L. J. et al. High molecular gas fractions in normal massive star forming galaxies in the young Universe. Nature 463, 781–784 (2010)
Garnett, D. R., Shields, G. A., Skillman, E. D., Sagan, S. P. & Dufour, R. J. Interstellar abundance gradients in NGC 2403: comparison to M33. Astrophys. J. 489, 63–86 (1997)
Magrini, L., Sestito, P., Randich, S. & Galli, D. The evolution of the Galactic metallicity gradient from high-resolution spectroscopy of open clusters. Astron. Astrophys. 494, 95–108 (2009)
Steidel, C. C. et al. Lyman break Galaxies at redshift z ∼ 3: survey description and full data set. Astrophys. J. 592, 728–754 (2003)
Maiolino, R. et al. AMAZE. I. The evolution of the mass-metallicity relation at z > 3. Astron. Astrophys. 488, 463–479 (2008)
Mannucci, F. et al. LSD: Lyman-break galaxies stellar populations and dynamics – I. Mass, metallicity and gas at z ∼ 3.1. Mon. Not. R. Astron. Soc. 398, 1915–1931 (2009)
Pozzetti, L. et al. The VIMOS VLT deep survey. The assembly history of the stellar mass in galaxies: from the young to the old universe. Astron. Astrophys. 474, 443–459 (2007)
Hopkins, A. M. & Beacom, J. F. On the normalization of the cosmic star formation history. Astrophys. J. 651, 142–154 (2006)
Kennicutt, R. C., Jr Star formation in galaxies along the Hubble sequence. Annu. Rev. Astron. Astrophys. 36, 189–231 (1998)
Eisenhauer, F. et al. SINFONI – Integral field spectroscopy at 50 milli-arcsecond resolution with the ESO VLT. Proc. SPIE 4841, 1548–1561 (2003)
Nagao, T., Maiolino, R. & Marconi, A. Gas metallicity diagnostics in star-forming galaxies. Astron. Astrophys. 459, 85–101 (2006)
van Zee, L., Salzer, J. J., Haynes, M. P., O'Donoghue, A. A. & Balonek, T. J. Spectroscopy of outlying H II regions in spiral galaxies: abundances and radial gradients. Astron. J. 116, 2805–2833 (1998)
Dopita, M. A. et al. Modeling the pan-spectral energy distribution of starburst galaxies. III. Emission line diagnostics of ensembles of evolving H II regions . Astrophys. J. 167 (Suppl.). 177–200 (2006)
Levesque, E. M., Kewley, L. J. & Larson, K. L. Theoretical modeling of star-forming galaxies. I. Emission-line diagnostic grids for local and low-metallicity galaxies. Astron. J. 139, 712–727 (2010)
Martín-Manjón, M. L., García-Vargas, M. L., Mollá, M. & Díaz, A. I. POPSTAR evolutionary synthesis models. II: optical emission-line spectra from giant HII regions. Mon. Not. R. Astron. Soc. 403, 2012–2032 (2010)
Molla, M., Ferrini, F. & Diaz, A. I. Evolution of spiral galaxies. VII. Time evolution of the radial distributions of abundances. Astrophys. J. 475, 519–533 (1997)
Hou, J. L., Prantzos, N. & Boissier, S. Abundance gradients and their evolution in the Milky Way disk. Astron. Astrophys. 362, 921–936 (2000)
Tinsley, B. M. Stellar lifetimes and abundance ratios in chemical evolution. Astrophys. J. 229, 1046–1056 (1979)
Kereš, D., Katz, N., Weinberg, D. H. & Davé, R. How do galaxies get their gas? Mon. Not. R. Astron. Soc. 363, 2–28 (2005)
Cresci, G. et al. The SINS survey: modeling the dynamics of z ∼ 2 galaxies and the high-z Tully-Fisher relation. Astrophys. J. 697, 115–132 (2009)
Genzel, R. et al. From rings to bulges: evidence for rapid secular galaxy evolution at z ∼ 2 from integral field spectroscopy in the SINS survey. Astrophys. J. 687, 59–77 (2008)
Kennicutt, R. C., Jr The global Schmidt law in star-forming galaxies Astrophys . J. 498, 541–552 (1998)
Bouché, N. et al. Dynamical properties of z ∼ 2 star-forming galaxies and a universal star formation relation. Astrophys. J. 671, 303–309 (2007)
Erb, D. K. A model for star formation, gas flows, and chemical evolution in galaxies at high redshifts. Astrophys. J. 674, 151–156 (2008)
Mannucci, F., Cresci, G., Maiolino, R., Marconi, A. & Gnerucci, A. A fundamental relation between mass, SFR and metallicity in local and high redshift galaxies. Mon. Not. R. Astron. Soc. . (in the press); preprint at 〈http://arXiv.org/abs/1005.0006〉 (2010)
Chabrier, G. Galactic stellar and substellar initial mass function. Publ. Astron. Soc. Pacif. 115, 763–795 (2003)
SINFONI data were obtained from observations made with the ESO Telescopes at the Paranal Observatories. We thank the ESO staff for their work and support. This work was supported by INAF and ASI.
The authors declare no competing financial interests.
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Cresci, G., Mannucci, F., Maiolino, R. et al. Gas accretion as the origin of chemical abundance gradients in distant galaxies. Nature 467, 811–813 (2010). https://doi.org/10.1038/nature09451
The Astronomy and Astrophysics Review (2019)