Living with Neighbors. VI. Unraveling the Dual Impact of Bars on Star Formation in Paired Galaxies Using DESI

Abstract We present a comprehensive investigation into the influence of stellar bars on star formation (SF) in galaxy pairs, using a large sample of low-redshift galaxies (0.02 < z < 0.08) from the DESI Legacy Imaging Surveys Data Release 8. Our analysis examines whether bars enhance or suppress SF during pair interactions, and how these outcomes depend on the star-forming properties of companion galaxies. We find that bars either catalyze or inhibit SF in their host galaxies, depending on the companion’s SF activity. In particular, barred galaxies paired with actively star-forming companions experience more pronounced central starbursts (with specific star formation rate up to ∼2.5 dex higher) than unbarred counterparts, whereas those with passive companions often have suppressed SF (sometimes below isolated galaxy levels). The notion of the dual role of bars can reconcile conventional conflicting reports of bar-driven enhancement versus quenching of SF activity. Bars, well known to regulate kiloparsec-scale dynamics, may also link to the impact of external environments: When a star-forming companion provides sufficient gas, bars drive central starbursts, whereas in gas-poor interactions, bars hasten gas depletion and contribute to SF suppression. This work highlights the necessity of accounting for both internal structure and companion properties to fully understand SF regulation in interacting galaxies.