Kavli Affiliate: Claudio Ricci
| First 5 Authors: Thomas Bohn, Hanae Inami, Aditya Togi, Lee Armus, Thomas S. -Y. Lai
| Summary:
We present James Webb Space Telescope (JWST) Integral Field Spectrograph
observations of NGC 3256, a local infrared-luminous late-stage merging system
with two nuclei roughly 1$;rm{kpc}$ apart, both of which have evidence of
cold molecular outflows. Using JWST/NIRSpec and MIRI datasets, we investigate
this morphologically complex system on spatial scales of $<$100$;rm{pc}$,
where we focus on the warm molecular H$_2$ gas surrounding the nuclei. We
detect collimated outflowing warm H$_2$ gas originating from the southern
nucleus, though we do not find significant outflowing H$_2$ gas surrounding the
northern nucleus. We measure maximum intrinsic outflow velocities of
$sim$1,000$;rm{km};rm{s}^{-1}$, which extend out to a distance of
0.7$;rm{kpc}$. Based on H$_2$ S(7)/S(1) ratios, we find a larger fraction of
warmer gas near the S nucleus, which decreases with increasing distance from
the nucleus, signifying the southern nucleus as a primary source of H$_2$
heating. The gas mass of the warm H$_2$ outflow component is estimated to be
$Mrm{_{warm,out}}=(1.4pm0.2)times10^6;rm{M}_{odot}$, as much as 6$%$ of
the cold H$_2$ mass estimated using ALMA CO data. The outflow time scale is
about $7times10^5;rm{yr}$, resulting in a mass outflow rate
$dot{M}rm{_{warm,out}}=2.0pm0.8;rm{M}_{odot};rm{yr}^{-1}$ and kinetic
power $Prm{_{warm,out}};sim;4times10^{41};rm{erg};rm{s}^{-1}$. Lastly,
regions within our 3.0"x3.0" NIRSpec data where the outflowing gas reside show
high [Fe II]/Pa$beta$ and H$_2$/Br$gamma$ line ratios, indicate enhanced
mechanical heating caused by the outflows. The fluxes and ratios of Polycyclic
Aromatic Hydrocarbons (PAH) in these regions are not significantly different
compared to those elsewhere in the disk, suggesting the outflows may not
significantly alter the PAH ionization state or grain size.
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