Galaxy-scale Bars in Late-type Sloan Digital Sky Survey Galaxies Do Not Influence the Average Accretion Rates of Supermassive Black Holes

Galaxy-scale bars are expected to provide an effective means for driving material toward 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∗ ∼ 0.2-30 ×10¹⁰ M_⊙) 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 ≳ 10⁴¹erg s^-1) active galactic nuclei 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 (Ṁ_acc ≈ 3 ×10^-5 M 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.