Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Xihan Ji, Xihan Ji, , ,
| Summary:
We report the detection of continuum excess in the rest-frame UV between 3000
AA and 3550 AA in the JWST/NIRSpec spectrum of GN-z11, a luminous galaxy
$z=10.603$. The shape of the continuum excess resembles a Balmer continuum but
has a break around 3546 AA. The fitting result of this excess depends on the
assumed origin of the continuum. If the continuum of GN-z11 is dominated by a
stellar population with a small Balmer break, the apparent blueshift of the
Balmer continuum is not significant and the best-fit Balmer continuum model
indicates a temperature of $T_e = 1.78^+0.25_-0.21times 10^4$ K. In
contrast, if the continuum is dominated by AGN emission, a nebular continuum
model cannot fit the spectrum properly. The absence of the Balmer jump
indicates an electron temperature of $sim 3times 10^4$ K, significantly
higher than the temperature of $T_e(rm O^2+) = 1.36pm 0.13times
10^4$ K inferred from [OIII]$lambda 4363$ and [OIII]$lambda 5007$. The
temperature difference can result from mixing of different ionized regions: the
Balmer emission mainly arises from dense and hot clouds in the Broad Line
Region, whereas the forbidden lines originate from less dense and colder gas.
An alternative explanation for the observed continuum excess is the FeII
emission, which shows a characteristic jump blueward of the Balmer limit as
previously seen in the spectra of many lower-redshift quasars. Through
comparisons with Cloudy models, we show an Fe abundance above $sim 1/3$ solar
is likely needed, which could be achieved via enrichment from Type-Ia
supernovae, hypernovae, or pair-instability supernovae.
| Search Query: ArXiv Query: search_query=au:”Roberto Maiolino”&id_list=&start=0&max_results=3