A merger in the dusty, z=7.5 galaxy A1689-zD1?
Artikel i vetenskaplig tidskrift, 2017

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 similar to 35-45 K for beta = 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 Pi] 158.8 mu m line at z([C II]) = 7.603. The stringent upper limits on the [C coproduct] L-FIR luminosity ratio suggest a [C coproduct] deficit similar to several bright quasars and massive starbursts.

galaxies: evolution

galaxies: ISM

galaxies: high-redshift

galaxies: formation

submillimetre: galaxies


Kirsten Kraiberg Knudsen

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

D. Watson

Niels Bohr Institute

D. Frayer

NRAO, Green Bank

L. Christensen

Niels Bohr Institute

A. Gallazzi

Osservatorio Astrofisico Di Arcetri

M. J. Michalowski

University of Edinburgh

J. Richard

CRAL Le Centre de Recherche Astronomique de Lyon

J. Zavala

Niels Bohr Institute

University Science Institute Reykjavik

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 466 138-146


Astronomi, astrofysik och kosmologi