ALMA Observations of the Submillimeter Dense Molecular Gas Tracers in
  the Luminous Type-1 Active Nucleus of NGC 7469
  We present ALMA Cycle 1 observations of the central kpc region of the
luminous type-1 Seyfert galaxy NGC 7469 with unprecedented high resolution
(0.5$"$ $\times$ 0.4$"$ = 165 pc $\times$ 132 pc) at submillimeter wavelengths.
Utilizing the wide-bandwidth of ALMA, we simultaneously obtained HCN(4-3),
HCO$^+$(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860
$\mu$m continuum. The region consists of the central $\sim$ 1$"$ component and
the surrounding starburst ring with a radius of $\sim$ 1.5$"$-2.5$"$. Several
structures connect these components. Except for CO(3-2), these dense gas
tracers are significantly concentrated towards the central $\sim$ 1$"$,
suggesting their suitability to probe the nuclear regions of galaxies. Their
spatial distribution resembles well those of centimeter and mid-infrared
continuum emissions, but it is anti-correlated with the optical one, indicating
the existence of dust obscured star formation. The integrated intensity ratios
of HCN(4-3)/HCO$^+$(4-3) and HCN(4-3)/CS(7-6) are higher at the AGN position
than at the starburst ring, which is consistent to our previous findings
(submm-HCN enhancement). However, the HCN(4-3)/HCO$^+$(4-3) ratio at the AGN
position of NGC 7469 (1.11$\pm$0.06) is almost half of the corresponding value
of the low-luminosity type-1 Seyfert galaxy NGC 1097 (2.0$\pm$0.2), despite the
more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the
ratio is comparable to that of the close vicinity of the AGN of NGC 1068
($\sim$ 1.5). Based on these results, we speculate that some other heating
mechanisms than X-ray (e.g., mechanical heating due to AGN jet) can contribute
significantly for shaping the chemical composition in NGC 1097.
