JWST/NIRSpec and MIRI observations of an expanding, jet-driven bubble of warm H_2 in the radio galaxy 3C 326 N
arxiv(2024)
摘要
The physical link between AGN activity and the suppression of star formation
in their host galaxies is one of the major open questions of AGN feedback. The
Spitzer space mission revealed a subset of nearby radio galaxies with unusually
bright line emission from warm (T≥ 100 K) H_2, while typical
star-formation tracers were exceptionally faint or undetected. We present JWST
NIRSpec and MIRI IFU observations of 3C 326 N at z=0.09 and identify 19
ro-vibrational H_2 emission lines that probe hot (T∼ 1000 K) gas as well
as the rotational lines of H_2 0–0 S(3), S(5), and S(6) which probe most of
the 2× 10^9 M_⊙ of warm H_2 in this galaxy. CO band heads show a
stellar component consistent with a "slow-rotator", typical of a massive
3×10^11 M_⊙ galaxy, and provide us with a reliable redshift of
z=0.08979± 0.0003. Extended line emission shows a bipolar bubble expanding
through the molecular disk at velocities of up to 380 km s^-1, delineated
by several bright clumps along the Northern outer rim, potentially from gas
fragmentation. Throughout the disk, the H_2 is very broad, FWHM 100-1300 km
s^-1, and shows dual-component Gaussian line profiles. [FeII]λ1.644
and Paα follow the same morphology, however [NeIII]λ15.56 is
more symmetric about the nucleus. We show that the gas, with the exception of
[NeIII]λ15.56, is predominantly heated by shocks driven by the radio
jet and that the accompanying line broadening is sufficient to suppress star
formation. We also compare the rotational and ro-vibrational lines, finding
that the latter can be a good proxy to the global morphology and kinematic
properties of the former in strongly turbulent environments. This enables
studies of turbulence in galaxies at intermediate and high redshifts while most
rotational lines are redshifted out of the MIRI bandpass for z>1.5.
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