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ALMA Reveals Metals yet No Dust within Multiple Components in CR7

Abstract : We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II]{}158μ {{m}} line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Lyα 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 ≈ 150 km s-1 with respect to the peak of Lyα emission. Other [C II] components are observed close to UV clumps B and C and are blueshifted by ≈ 300 and ≈80 km s-1 with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3σ limiting luminosity {L}{IR}({T}d=35 {{K}})< 3.1× {10}10 {L}. 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 {M} yr-1. All clumps have [C II] luminosities consistent within the scatter observed in the local relation between SFR and {L}[{{C}{{II}}]}, implying that strong Lyα 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 0.1< {{Z}}/{{{Z}}}< 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.
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Submitted on : Tuesday, May 24, 2022 - 12:04:18 PM
Last modification on : Monday, July 4, 2022 - 9:11:47 AM

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J. Matthee, D. Sobral, F. Boone, H. Röttgering, D. Schaerer, et al.. ALMA Reveals Metals yet No Dust within Multiple Components in CR7. The Astrophysical Journal, 2017, 851, ⟨10.3847/1538-4357/aa9931⟩. ⟨insu-03676801⟩

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