A 2-3 mm high-resolution molecular line survey towards the centre of the nearby spiral galaxy NGC 6946. (arXiv:2201.02209v2 [astro-ph.GA] UPDATED)

A 2-3 mm high-resolution molecular line survey towards the centre of the nearby spiral galaxy NGC 6946. (arXiv:2201.02209v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Eibensteiner_C/0/1/0/all/0/1">Cosima Eibensteiner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barnes_A/0/1/0/all/0/1">Ashley T. Barnes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bigiel_F/0/1/0/all/0/1">Frank Bigiel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schinnerer_E/0/1/0/all/0/1">Eva Schinnerer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_D/0/1/0/all/0/1">Daizhong Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Meier_D/0/1/0/all/0/1">David S. Meier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Usero_A/0/1/0/all/0/1">Antonio Usero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leroy_A/0/1/0/all/0/1">Adam K. Leroy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosolowsky_E/0/1/0/all/0/1">Erik Rosolowsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Puschnig_J/0/1/0/all/0/1">Johannes Puschnig</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lazar_I/0/1/0/all/0/1">Ilin Lazar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pety_J/0/1/0/all/0/1">Jérôme Pety</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_L/0/1/0/all/0/1">Laura A. Lopez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Emsellem_E/0/1/0/all/0/1">Eric Emsellem</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beslic_I/0/1/0/all/0/1">Ivana Bešlić</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Querejeta_M/0/1/0/all/0/1">Miguel Querejeta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Murphy_E/0/1/0/all/0/1">Eric J. Murphy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brok_J/0/1/0/all/0/1">Jakob den Brok</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schruba_A/0/1/0/all/0/1">Andreas Schruba</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chevance_M/0/1/0/all/0/1">Mélanie Chevance</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Glover_S/0/1/0/all/0/1">Simon C. O. Glover</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gao_Y/0/1/0/all/0/1">Yu Gao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grasha_K/0/1/0/all/0/1">Kathryn Grasha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hassani_H/0/1/0/all/0/1">Hamid Hassani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henshaw_J/0/1/0/all/0/1">Jonathan D. Henshaw</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jimenez_Donaire_M/0/1/0/all/0/1">Maria J. Jimenez-Donaire</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Klessen_R/0/1/0/all/0/1">Ralf S. Klessen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kruijssen_J/0/1/0/all/0/1">J. M. Diederik Kruijssen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pan_H/0/1/0/all/0/1">Hsi-An Pan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Saito_T/0/1/0/all/0/1">Toshiki Saito</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sormani_M/0/1/0/all/0/1">Mattia C. Sormani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Teng_Y/0/1/0/all/0/1">Yu-Hsuan Teng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Williams_T/0/1/0/all/0/1">Thomas G. Williams</a>

The complex physical, kinematic, and chemical properties of galaxy centres
make them interesting environments to examine with molecular line emission. We
present new $2-4$” (${sim}75{-}150$ pc at $7.7$ Mpc) observations at 2 and 3
mm covering the central $50$” (${sim}1.9$ kpc) of the nearby double-barred
spiral galaxy NGC 6946 obtained with the IRAM Plateau de Bure Interferometer.
We detect spectral lines from ten molecules: CO, HCN, HCO$^+$, HNC, CS,
HC$_3$N, N$_2$H$^+$, C$_2$H, CH$_3$OH, and H$_2$CO. We complemented these with
published 1mm CO observations and 33 GHz continuum observations to explore the
star formation rate surface density ${Sigma_{mathrm{SFR}}}$ on 150 pc scales.
In this paper, we analyse regions associated with the inner bar of NGC 6946 $-$
the nuclear region (NUC), the northern (NBE), and southern inner bar end (SBE)
and we focus on short-spacing corrected bulk (CO) and dense gas tracers (HCN,
HCO$^+$, and HNC). We find that HCO$^+$ correlates best with
${Sigma_{mathrm{SFR}}}$, but the dense gas fraction ($f_{mathrm{dense}}$)
and star formation efficiency of the dense gas (${mathrm{SFE_{dense}}}$) fits
show different behaviours than expected from large-scale disc observations.The
SBE has a higher ${Sigma_{mathrm{SFR}}}$, $f_{mathrm{dense}}$, and shocked
gas fraction than the NBE. We examine line ratio diagnostics and find a higher
CO(2-1)/CO(1-0) ratio towards NBE than for the NUC. Moreover, comparison with
existing extragalactic datasets suggests that using the HCN/HNC ratio to probe
kinetic temperatures is not suitable on kiloparsec and sub-kiloparsec scales in
extragalactic regions. Lastly, our study shows that the HCO$^+$/HCN ratio might
not be a unique indicator to diagnose AGN activity in galaxies.

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