We report new deep observations obtained with the Atacama Large Millimetre Array (ALMA) aimed at investigating the [C II]158 μm line and continuum emission in three spectroscopically confirmed Lyman break galaxies at 6.8 < z ≤ 7.1, i.e. well within the re-ionization epoch. With star formation rates of SFR ~ 5-15M<inf>⊙</inf> yr<sup>-1</sup> these systems are much more representative of the high-z galaxy population than other systems targeted in the past bymillimetre observations. For the galaxy with the deepest observation we detect [C II] emission at redshift z = 7.107, fully consistent with the Ly α redshift, but spatially offset by 0.7 arcsec (4 kpc) from the optical emission. At the location of the optical emission, tracing both the Ly α line and the far-UV continuum, no [CII] emission is detected in any of the three galaxies, with 3s upper limits significantly lower than the [CII] emission observed in lower redshift galaxies. These results suggest that molecular clouds in the central parts of primordial galaxies are rapidly disrupted by stellar feedback. As a result, [C II] emission mostly arises from more external accreting/satellite clumps of neutral gas. These findings are in agreement with recent models of galaxy formation. Thermal far-infrared continuum is not detected in any of the three galaxies. However, the upper limits on the infrared-to-UV emission ratio do not exceed those derived in metal- and dust-poor galaxies.

We report new deep observations obtained with the Atacama Large Millimetre Array (ALMA) aimed at investigating the [C II]158 μm line and continuum emission in three spectroscopically confirmed Lyman break galaxies at 6.8 &lt; z ≤ 7.1, i.e. well within the re-ionization epoch. With star formation rates of SFR ∼ 5–15M⊙ yr− 1 these systems are much more representative of the high-z galaxy population than other systems targeted in the past by millimetre observations. For the galaxy with the deepest observation we detect [C II] emission at redshift z = 7.107, fully consistent with the Ly α redshift, but spatially offset by 0.7 arcsec (4 kpc) from the optical emission. At the location of the optical emission, tracing both the Ly α line and the far-UV continuum, no [C II] emission is detected in any of the three galaxies, with 3σ upper limits significantly lower than the [C II] emission observed in lower redshift galaxies. These results suggest that molecular clouds in the central parts of primordial galaxies are rapidly disrupted by stellar feedback. As a result, [C II] emission mostly arises from more external accreting/satellite clumps of neutral gas. These findings are in agreement with recent models of galaxy formation. Thermal far-infrared continuum is not detected in any of the three galaxies. However, the upper limits on the infrared-to-UV emission ratio do not exceed those derived in metal- and dust-poor galaxies.

The assembly of ‘normal’ galaxies atz ∼ 7 probed by ALMA

MAIOLINO, Roberto;Carniani, S.;VALLINI, LIVIA;FERRARA, ANDREA;GALLERANI, SIMONA;
2015

Abstract

We report new deep observations obtained with the Atacama Large Millimetre Array (ALMA) aimed at investigating the [C II]158 μm line and continuum emission in three spectroscopically confirmed Lyman break galaxies at 6.8 < z ≤ 7.1, i.e. well within the re-ionization epoch. With star formation rates of SFR ∼ 5–15M⊙ yr− 1 these systems are much more representative of the high-z galaxy population than other systems targeted in the past by millimetre observations. For the galaxy with the deepest observation we detect [C II] emission at redshift z = 7.107, fully consistent with the Ly α redshift, but spatially offset by 0.7 arcsec (4 kpc) from the optical emission. At the location of the optical emission, tracing both the Ly α line and the far-UV continuum, no [C II] emission is detected in any of the three galaxies, with 3σ upper limits significantly lower than the [C II] emission observed in lower redshift galaxies. These results suggest that molecular clouds in the central parts of primordial galaxies are rapidly disrupted by stellar feedback. As a result, [C II] emission mostly arises from more external accreting/satellite clumps of neutral gas. These findings are in agreement with recent models of galaxy formation. Thermal far-infrared continuum is not detected in any of the three galaxies. However, the upper limits on the infrared-to-UV emission ratio do not exceed those derived in metal- and dust-poor galaxies.
Settore FIS/05 - Astronomia e Astrofisica
galaxies - evolution; galaxies - formation; galaxies - high-redshift; galaxies - ISM; galaxies - star formation
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11384/60045
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