Astrophys. J., 851, 145-145 (2017/December-3)
ALMA reveals metals yet no dust within multiple components in CR7.
MATTHEE J., SOBRAL D., BOONE F., ROTTGERING H., SCHAERER D., GIRARD M., PALLOTTINI A., VALLINI L., FERRARA A., DARVISH B. and MOBASHER B.
Abstract (from CDS):
We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II]_158µm_ 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 LIR(Td=35 K) 3.1×1010 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[CII], 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.
© 2017. The American Astronomical Society. All rights reserved.
dark ages, reionization, first stars - galaxies: formation - galaxies: high-redshift - galaxies: ISM - galaxies: kinematics and dynamics - galaxies: kinematics and dynamics
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