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  • A merger in the dusty, z = ...
    Knudsen, Kirsten K; Watson, Darach; Frayer, David; Christensen, Lise; Gallazzi, Anna; Michałowski, Michał J; Richard, Johan; Zavala, Jesús

    Monthly notices of the Royal Astronomical Society, 04/2017, Letnik: 466, Številka: 1
    Journal Article

    Abstract The gravitationally lensed galaxy A1689-zD1 is one of the most distant spectroscopically confirmed sources (z = 7.5). It is the earliest known galaxy where the interstellar medium (ISM) has been detected; dust emission was detected with the Atacama Large Millimetre Array (ALMA). A1689-zD1 is also unusual among high-redshift dust emitters as it is a sub-L ★ galaxy and is therefore a good prospect for the detection of gaseous ISM in a more typical galaxy at this redshift. We observed A1689-zD1 with ALMA in bands 6 and 7 and with the Green Bank Telescope (GBT) in band Q. To study the structure of A1689-zD1, we map the mm-thermal dust emission and find two spatial components with sizes about 0.4 − 1.7 kpc (lensing-corrected). The rough spatial morphology is similar to what is observed in the near-infrared with HST and points to a perturbed dynamical state, perhaps indicative of a major merger or a disc in early formation. The ALMA photometry is used to constrain the far-infrared spectral energy distribution, yielding a dust temperature (T dust ∼ 35–45 K for β = 1.5 − 2). We do not detect the CO(3-2) line in the GBT data with a 95 per cent upper limit of 0.3 mJy observed. We find a slight excess emission in ALMA band 6 at 220.9 GHz. If this excess is real, it is likely due to emission from the C ii 158.8 μm line at $z_{\rm C\,\small {II}} = 7.603$ . The stringent upper limits on the C ii L FIR luminosity ratio suggest a C ii deficit similar to several bright quasars and massive starbursts.