Stellar bars can lead to gas inflow toward the center of a galaxy and stimulate nuclear star formation .
However , there is no compelling evidence on whether they also feed a central supermassive black hole : by measuring the fractions of barred active and inactive galaxies , previous studies have yielded conflicting results .
In this paper , we aim to understand the lack of observational evidence for bar-driven active galactic nucleus ( AGN ) activity by studying a sample of 41 nearby ( d < 35 Mpc ) barred galaxies from the Spitzer Survey for Stellar Structure in Galaxies .
We use Chandra observations to measure nuclear 2–10 keV X-ray luminosities and estimate Eddington ratios , together with Spitzer 3.6 \mu m imaging to quantify the strength of the stellar bar in two independent ways : ( 1 ) from its structure , as traced by its ellipticity and boxiness , and ( 2 ) from its gravitational torque Q _ { b } , taken as the maximum ratio of the tangential force to the mean background radial force .
In this way , rather than discretizing the presence of both stellar bars and nuclear activity , we are able to account for the continuum of bar strengths and degrees of AGN activity .
We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray luminosity and Eddington ratio of L _ { \mathrm { X } } = 4.3 \times 10 ^ { 38 } erg s ^ { -1 } and L _ { \mathrm { bol } } / L _ { \mathrm { Edd } } = 6.9 \times 10 ^ { -6 } respectively , consistent with low-luminosity AGN activity .
Including upper limits for those galaxies without nuclear detections , we find no significant correlation between any of the bar strength indicators and the degree of nuclear activity , irrespective of galaxy luminosity , stellar mass , Hubble type , or bulge size .
Strong bars do not favor brighter or more efficient nuclear activity , implying that at least for the low-luminosity regime , supermassive black hole fueling is not closely connected to large scale features .