Galaxy-scale bars in late-type Sloan Digital Sky Survey galaxies do not influence the average accretion rates of supermassive black holes.

Abstract

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 ${M}_{* }\sim 0.2\mbox{--}30\times {10}^{10}\,{M}_{\odot }$) 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 (${L}_{{\rm{X}}}\gtrsim {10}^{41}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$) 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 (${\dot{M}}_{\mathrm{acc}}\approx 3\times {10}^{-5}$ ${M}_{\odot }$ yr−1). Hence, we robustly conclude that large-scale bars have little or no effect on the average growth of BHs in nearby ($z\lt 0.15$) galaxies over gigayear timescales.