Matthee, J. and Sobral, D. and Boone, F. and Röttgering, H. and Schaerer, D. and Girard, M. and Pallottini, A. and Vallini, L. and Ferrara, A. and Darvish, B. and Mobasher, B. (2017) ALMA reveals metals yet no dust within multiple components in CR7. The Astrophysical Journal, 851 (2): 145. ISSN 0004-637X
1709.06569v1.pdf - Accepted Version
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Abstract
We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [CII]$_{158 \mu \rm m}$ line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Ly$\alpha$ emitting galaxy at $z=6.6$ that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [CII] emission. The two most luminous components in [CII] coincide with the brightest UV components (A and B), blue-shifted by $\approx 150$ km s$^{-1}$ with respect to the peak of Ly$\alpha$ emission. Other [CII] components are observed close to UV clumps B and C and are blue-shifted by $\approx300$ and $\approx80$ km s$^{-1}$ with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3$\sigma$ limiting luminosity L$_{\rm IR} (T_d = 35 \rm \, K) CR7s clumps have metallicities of $0.1\rm Z/Z_{\odot}0.2$. The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early Universe through complex accretion of satellites.