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]_(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 L_(IR)(T_d = 35 K) < 3.1 x 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.
Additional Information
© 2017 The American Astronomical Society. Received 2017 September 19; revised 2017 October 31; accepted 2017 November 6; published 2017 December 21. We thank the referee for their constructive comments, which have helped improve the quality and clarity of this work. We thank Raffaella Schneider for comments on an earlier version of this paper. We thank Leindert Boogaard, Steven Bos, Rychard Bouwens, and Renske Smit for discussions. J.M. acknowledges the support of a Huygens PhD fellowship from Leiden University. D.S. acknowledges financial support from the Netherlands Organisation for Scientific research (NWO) through a Veni fellowship and from Lancaster University through an Early Career Internal Grant A100679. A.F. acknowledges support from the ERC Advanced Grant INTERSTELLAR H2020/740120. B.D. acknowledges financial support from NASA through the Astrophysics Data Analysis Program (ADAP), grant number NNX12AE20G. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 294.A-5018. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2015.1.00122.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. Facilities: ALMA (band 6) - , HST (WFC3) - , VLT (X-SHOOTER) - , Keck (DEIMOS) - , VISTA (Vircam) - , Subaru (S-Cam).Attached Files
Published - Matthee_2017_ApJ_851_145.pdf
Submitted - 1709.06569.pdf
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Additional details
- Eprint ID
- 84016
- Resolver ID
- CaltechAUTHORS:20171222-084108368
- Leiden University
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)
- A100679
- Lancaster University
- 740120
- European Research Council (ERC)
- NNX12AE20G
- NASA
- Created
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2017-12-22Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field