Rights statement: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version David Sobral, Jorryt Matthee, Gabriel Brammer, Andrea Ferrara, Lara Alegre, Huub Röttgering, Daniel Schaerer, Bahram Mobasher, Behnam Darvish; On the nature and physical conditions of the luminous Ly α emitter CR7 and its rest-frame UV components, Monthly Notices of the Royal Astronomical Society, Volume 482, Issue 2, 11 January 2019, Pages 2422–2441, https://doi.org/10.1093/mnras/sty2779 is available online at: https://academic.oup.com/mnras/article/482/2/2422/5144221
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
| <mark>Journal publication date</mark> | 11/01/2019 |
|---|---|
| <mark>Journal</mark> | Monthly Notices of the Royal Astronomical Society |
| Issue number | 2 |
| Volume | 482 |
| Number of pages | 20 |
| Pages (from-to) | 2422-2441 |
| Publication Status | Published |
| Early online date | 24/10/18 |
| <mark>Original language</mark> | English |
We present new Hubble Space Telescope (HST)/WFC3 observations and re-analyse VLT data to unveil the continuum, variability, and rest-frame ultraviolet (UV) lines of the multiple UV clumps of the most luminous Ly alpha emitter at z = 6.6, CR7 (COSMOS Redshift 7). Our re-reduced, flux-calibrated X-SHOOTER spectra of CR7 reveal an HeII emission line in observations obtained along the major axis of Ly alpha emission with the best seeing conditions. He II is spatially offset by approximate to+ 0.8 arcsec from the peak of Ly alpha emission, and it is found towards clump B. Our WFC3 grism spectra detects the UV continuum of CR7' s clump A, yielding a power law with beta = -2.5(-0.7) (+ 0.6) and M-UV = -21.87(-0.20) (+ 0.25) . No significant variability is found for any of the UV clumps on their own, but there is tentative (approximate to 2.2 sigma) brightening of CR7 in F110W as a whole from 2012 to 2017. HST grism data fail to robustly detect rest-frame UV lines in any of the clumps, implying fluxes less than or similar to 2 x 10(-17) erg s(-1) cm(-2) (3 sigma). We perform CLOUDY modelling to constrain the metallicity and the ionizing nature of CR7. CR7 seems to be actively forming stars without any clear active galactic nucleus activity in clump A, consistent with a metallicity of similar to 0.05-0.2 Z(circle dot). Component C or an interclump component between B and C may host a high ionization source. Our results highlight the need for spatially resolved information to study the formation and assembly of early galaxies.