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Spectral signature of cosmological infall of gas around the first quasars


Recent observations have shown that, only a billion years after the Big Bang, the Universe was already lit up by bright quasars1 fuelled by the infall of gas onto supermassive black holes. The masses of these early black holes are inferred from their luminosities to be >109 solar masses (M), which is a difficult theoretical challenge to explain. Like nearby quasars, the early objects could have formed in the central cores of massive host galaxies. The formation of these hosts could be explained if, like local large galaxies, they were assembled gravitationally inside massive (> 1012M) haloes of dark matter2. There has hitherto been no observational evidence for the presence of these massive hosts or their surrounding haloes. Here we show that the cosmic gas surrounding each halo must respond to its strong gravitational pull, where absorption by the infalling hydrogen produces a distinct spectral signature. That signature can be seen in recent data3,4.

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Figure 1: Schematic illustration of how infall produces a unique spectral signature.
Figure 2: Comparison between models of cosmological infall and observed quasar spectra.


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We thank E. Turner and H. Netzer for discussions, and are grateful for the hospitality of the Institute for Advanced Study where this work was completed. R.B. acknowledges the support of an Alon Fellowship at Tel Aviv University and of the Israel Science Foundation. A.L. acknowledges support from the Institute for Advanced Study and a John Simon Guggenheim Memorial Fellowship. This work was also supported by the National Science Foundation.

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Correspondence to Rennan Barkana or Abraham Loeb.

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Barkana, R., Loeb, A. Spectral signature of cosmological infall of gas around the first quasars. Nature 421, 341–343 (2003).

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