Dissecting the Local Environment of FRB 190608 in the Spiral Arm of its
  Host Galaxy
  We present a high-resolution analysis of the host galaxy of fast radio burst
(FRB)~190608, an SB(r)c galaxy at $z=0.11778$ (hereafter HG 190608), to dissect
its local environment and its contributions to the FRB properties. Our Hubble
Space Telescope Wide Field Camera 3 ultraviolet and visible light image reveals
that the subarcsecond localization of FRB~190608 is coincident with a knot of
star-formation ($\Sigma_{\rm SFR} = 1.5 \times 10^{-2}~ M_{\odot} \, \rm \,
yr^{-1} \, kpc^{-2}$) in the northwest spiral arm of HG~190608. Using H$\beta$
emission present in our Keck Cosmic Web Imager integral field spectrum of the
galaxy with a surface brightness of $\mu_{\rm H\beta}=
\mathrm{(3.36\pm0.21)\times10^{-17}\;erg\;s^{-1}\;cm^{-2}\;arcsec^{-2}}$, we
infer an extinction-corrected H$\alpha$ surface brightness and compute a
dispersion measure (DM) from the interstellar medium of HG 190608 of $\rm
DM_{\rm Host,ISM} = 94 \pm 38~ \;pc\;cm^{-3}$. The galaxy rotates with a
circular velocity $v_{\rm circ} = \rm 141 \pm 8~ km\;s^{-1}$ at an inclination
$i_{\mathrm{gas}} = 37 \pm 3^\circ$, giving a dynamical mass $M_{\rm halo}^{\rm
dyn} \approx 10^{11.96 \pm 0.08}~M_{\odot}$. This implies a halo contribution
to the DM of $\rm DM_{\rm Host,Halo}= \rm 55\pm25 \;pc\;cm^{-3}$ subject to
assumptions on the density profile and fraction of baryons retained. From the
galaxy rotation curve, we infer a bar-induced pattern speed of $\Omega_p=34\pm
6\;\mathrm{km\;s^{-1}\;kpc^{-1}}$ using linear resonance theory. We then
calculate the maximum time since star-formation for a progenitor using the
furthest distance to the arm's leading edge within the localization, and find
$t_{\mathrm{enc}} = 21_{-6}^{+25}$ Myr. Unlike previous high-resolution studies
of FRB environments, we find no evidence of disturbed morphology, emission, or
kinematics for FRB 190608.
