ALMA Reveals Metals yet No Dust within Multiple Components in CR7

• Published in: The Astrophysical journal 2017-12, Vol.851 (2), p.145
• Main Authors: Matthee, J., Sobral, D., Boone, F., Röttgering, H., Schaerer, D., Girard, M., Pallottini, A., Vallini, L., Ferrara, A., Darvish, B., Mobasher, B.
• Format: Article
• Language: English
• Subjects: Astrophysics; Clumps; Continuum radiation; dark ages; dark ages, reionization, first stars; Deposition; Dust; Emissions; first stars; Galaxies; galaxies: formation; galaxies: high-redshift; galaxies: ISM; galaxies: kinematics and dynamics; Luminosity; Photoionization; Red shift; reionization; Sciences of the Universe; Spatial resolution
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/aa9931

We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C ii] line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Ly emitting galaxy at z = 6.6 that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [C ii] emission. The two most luminous components in [C ii] coincide with the brightest UV components (A and B), blueshifted by km s−1 with respect to the peak of Ly emission. Other [C ii] components are observed close to UV clumps B and C and are blueshifted by and 80 km s−1 with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3 limiting luminosity . This allows us to mitigate uncertainties in the dust-corrected SFR and derive SFRs for the three UV clumps A, B, and C of 28, 5, and 7 yr−1. All clumps have [C ii] luminosities consistent within the scatter observed in the local relation between SFR and , implying that strong Ly emission does not necessarily anti-correlate with [C ii] luminosity. Combining our measurements with the literature, we show that galaxies with blue UV slopes have weaker [C ii] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionization. Comparison with hydrodynamical simulations suggests that CR7's clumps have metallicities of . 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.