Galaxy-scale bars are expected to provide an effective means for driving material towards the central region in spiral galaxies , and possibly feeding supermassive black holes ( BHs ) .
Here we present a statistically-complete study of the effect of bars on average BH accretion .
From a well-selected sample of 50,794 spiral galaxies ( with M _ { * } \sim 0.2 - 30 \times 10 ^ { 10 } M _ { \odot } ) extracted from the Sloan Digital Sky Survey Galaxy Zoo 2 project , we separate those sources considered to contain galaxy-scale bars from those that do not .
Using archival data taken by the Chandra X-ray Observatory , we identify X-ray luminous ( L _ { X } \gtrsim 10 ^ { 41 } \hbox { $ { \thinspace erg } { \thinspace s } ^ { -1 } $ } ) active galactic nuclei ( AGN ) and perform an X-ray stacking analysis on the remaining X-ray undetected sources .
Through X-ray stacking , we derive a time-averaged look at accretion for galaxies at fixed stellar mass and star formation rate , finding that the average nuclear accretion rates of galaxies with bar structures are fully consistent with those lacking bars ( \dot { M } _ { acc } \approx 3 \times 10 ^ { -5 } M _ { \odot } yr ^ { -1 } ) .
Hence , we robustly conclude that large-scale bars have little or no effect on the average growth of BHs in nearby ( z < 0.15 ) galaxies over gigayear timescales .