Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2017

A merger in the dusty, $z=7.5$ galaxy A1689-zD1?

Kirsten K. Knudsen
  • Fonction : Auteur
Darach Watson
  • Fonction : Auteur
David Frayer
  • Fonction : Auteur
Lise Christensen
  • Fonction : Auteur
Anna Gallazzi
Michał J. Michałowski
  • Fonction : Auteur
Jesús Zavala
  • Fonction : Auteur

Résumé

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.

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hal-01554290 , version 1 (24-08-2025)

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Kirsten K. Knudsen, Darach Watson, David Frayer, Lise Christensen, Anna Gallazzi, et al.. A merger in the dusty, $z=7.5$ galaxy A1689-zD1?. Monthly Notices of the Royal Astronomical Society, 2017, 466 (1), pp.138-146. ⟨10.1093/mnras/stw3066⟩. ⟨hal-01554290⟩
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