Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Eleonora Parlanti, Stefano Carniani, Giacomo Venturi, Rodrigo Herrera-Camus, Santiago Arribas
| Summary:
In this study, we present a detailed multiphase analysis of HZ4, a
main-sequence star-forming galaxy at z ~ 5.5, known for being a turbulent
rotating disk and having a detection of a [CII] outflow in the ALMA
observations. We exploit JWST/NIRSpec observations in the integral field
spectroscopy mode with low- and high-spectral resolution that allow us for the
first time to spatially resolve the rest-frame UV and optical emission of the
galaxy to investigate the galaxy properties. In particular, the high-resolution
dataset allows us to study the kinematics of the ionized gas phase, and the
conditions of the interstellar medium, such as the excitation mechanism, dust
attenuation, and metallicity. The lower-spectral resolution observations allow
us to study the continuum emission and infer the stellar populations’ ages and
properties. Our findings suggest that HZ4 is a galaxy merger rather than a
rotating disk as previously inferred from lower resolution [CII] data. The
merger is associated with an extended broad, blueshifted emission, potentially
indicative of an outflow originating from a region of intense star formation
and extending up to 4 kpc. In light of these new observations we reanalyzed the
ALMA data to compare the multiphase gas properties. If we interpret the broad
components seen in [CII] and [OIII]$lambda$5007.A as outflows, the neutral
and ionized components are co-spatial, the mass loading factor of the ionized
phase is significantly lower than that of the neutral phase, aligning with
trends observed in multi-phase systems at lower redshifts. Nonetheless,
additional observations and larger statistical samples are essential to
determine the role of mergers and outflows in the early Universe and to clarify
the origin of the broad emission components observed in this system.
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