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Macclesfield, United Kingdom

Willott C.J.,National Research Council Canada | Carilli C.L.,U.S. National Radio Astronomy Observatory | Carilli C.L.,University of Cambridge | Wagg J.,Square Kilometre Array Organization | Wang R.,Peking University
Astrophysical Journal | Year: 2015

We present Atacama Large Millimeter Array (ALMA) detections of atomic carbon line and dust continuum emission in two UV-luminous galaxies at redshift 6. The far-infrared (far-IR) luminosities of these galaxies are substantially lower than similar starbursts at later cosmic epochs, indicating an evolution in the dust properties with redshift, in agreement with the evolution seen in ultraviolet (UV) attenuation by dust. The [C ii] to FIR ratios are found to be higher than at low redshift showing that [C ii] should be readily detectable by ALMA within the reionization epoch. One of the two galaxies shows a complex merger nature with the less massive component dominating the UV emission and the more massive component dominating the FIR line and continuum. Using the interstellar atomic carbon line to derive the systemic redshifts we investigate the velocity of Ly emission emerging from high-z galaxies. In contrast to previous work, we find no evidence for decreasing Ly velocity shifts at high-redshift. We observe an increase in velocity shifts from to , consistent with the effects of increased intergalactic medium absorption. © 2015. The American Astronomical Society. All rights reserved.. Source

Castellano M.,National institute for astrophysics | Dayal P.,Durham University | Dayal P.,University of Groningen | Pentericci L.,National institute for astrophysics | And 23 more authors.
Astrophysical Journal Letters | Year: 2016

We present an analysis of deep Hubble Space Telescope (HST) multi-band imaging of the BDF field specifically designed to identify faint companions around two of the few Lyα emitting galaxies spectroscopically confirmed at z ∼ 7. Although separated by only 4.4 proper Mpc these galaxies cannot generate H ii regions large enough to explain the visibility of their Lyα lines, thus requiring a population of fainter ionizing sources in their vicinity. We use deep HST and VLT-Hawk-I data to select z ∼ 7 Lyman break galaxies around the emitters. We select six new robust z ∼ 7 LBGs at Y ∼ 26.5-27.5 whose average spectral energy distribution is consistent with the objects being at the redshift of the close-by Lyα emitters. The resulting number density of z ∼ 7 LBGs in the BDF field is a factor of approximately three to four higher than expected in random pointings of the same size. We compare these findings with cosmological hydrodynamic plus radiative transfer simulations of a universe with a half neutral IGM: we find that indeed Lyα emitter pairs are only found in completely ionized regions characterized by significant LBG overdensities. Our findings match the theoretical prediction that the first ionization fronts are generated within significant galaxy overdensities and support a scenario where faint, "normal" star-forming galaxies are responsible for reionization. © 2016. The American Astronomical Society. All rights reserved. Source

Maiolino R.,University of Cambridge | Carniani S.,University of Cambridge | Carniani S.,Universitaia Of Firenze | Fontana A.,National institute for astrophysics | And 13 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

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 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. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

Aravena M.,Diego Portales University | Aravena M.,European Southern Observatory | Hodge J.A.,U.S. National Radio Astronomy Observatory | Wagg J.,Square Kilometre Array Organization | And 9 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We present detections of the CO(J = 1-0) emission line in a sample of four massive starforming galaxies at z~1.5-2.2 obtained with theKarlG. JanskyVery LargeArray. Combining these observations with previous CO(2-1) and CO(3-2) detections of these galaxies, we study the excitation properties of the molecular gas in our sample sources. We find an average line brightness temperature ratios of R21 = 0.70 ± 0.16 and R31 = 0.50 ± 0.29, based on measurements for three and two galaxies, respectively. These results provide additional support to previous indications of sub-thermal gas excitation for the CO(3-2) line with a typically assumed line ratio R31 ~ 0.5. For one of our targets, BzK-21000, we present spatially resolved CO line maps. At the resolution of 0.18 arcsec (1.5 kpc), most of the emission is resolved out except for some clumpy structure. From this, we attempt to identify molecular gas clumps in the data cube, finding four possible candidates. We estimate that <40 per cent of the molecular gas is confined to giant clumps (~1.5 kpc in size), and thus most of the gas could be distributed in small fainter clouds or in fairly diffuse extended regions of lower brightness temperatures than our sensitivity limit. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

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