TY - JOUR

T1 - On the nature and physical conditions of the luminous Ly alpha emitter CR7 and its rest-frame UV components

AU - Sobral, David

AU - Matthee, Jorryt

AU - Brammer, Gabriel

AU - Ferrara, Andrea

AU - Alegre, Lara

AU - Rottgering, Huub

AU - Schaerer, Daniel

AU - Mobasher, Bahram

AU - Darvish, Behnam

PY - 2019/1

Y1 - 2019/1

N2 - 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.

AB - 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.

KW - galaxies: evolution

KW - galaxies: high-redshift

KW - galaxies: ISM

KW - cosmology: observations

KW - dark ages, reionization, first stars

KW - early Universe

KW - COLLAPSE BLACK-HOLE

KW - CONTINUUM SLOPES

KW - RADIO GALAXIES

KW - NO EVIDENCE

KW - TO 6-7

KW - REIONIZATION

KW - EPOCH

KW - DUST

KW - SPECTROSCOPY

KW - EVOLUTION

U2 - 10.1093/mnras/sty2779

DO - 10.1093/mnras/sty2779

M3 - Journal article

VL - 482

SP - 2422

EP - 2441

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

SN - 0035-8711

IS - 2

ER -