Bars Across Time: Tracing Galactic Structures Over 12 Billion Years
Using JWST data, Zoe Le Conte and collaborators traced how stellar bars in disc galaxies evolved over 12 billion years. They found the bar fraction declines from 16% at z ≈ 1–2 to 7% at z ≈ 4, showing that stable discs already existed early in cosmic history. Bar lengths stayed roughly constant, indicating that bars and galaxy discs have grown together over time.
When Bars Take Shape: Tracing the History of Galactic Bars Across Cosmic Time
This study presents the first large sample of bar age measurements in nearby galaxies, using nuclear discs to trace bar formation. The authors find that bars formed across a wide range of cosmic time and that older bars tend to be longer, stronger, and linked to reduced star formation. Surprisingly, bar age doesn’t correlate with galaxy mass, challenging the downsizing theory.
How Do Galactic Bars Form? A Look at Tidal vs. Internal Growth
This study compares bars in galaxies that form internally versus those triggered by tidal interactions. Simulations show that tidal forces mainly affect when a bar forms, not how fast it grows, except in galaxies resistant to bar formation, where bars grow differently. Bars in naturally unstable galaxies follow the same growth pattern whether triggered externally or not, highlighting the dominance of a galaxy’s internal properties in shaping bar evolution.
Unlocking the Secrets of the Stellar Halo: Dynamical Streams and the Galactic Bar
This study explores moving groups of stars in the Milky Way’s halo, revealing two streams influenced by the galaxy’s central bar. Using Gaia data and simulations, the authors show that these streams result from resonances with the bar’s rotation. By analyzing their motion, they estimate the Milky Way’s mass and bar pattern speed, refining our understanding of the galaxy’s structure and dynamics. Their findings highlight the role of resonances in shaping stellar motions.
How Do Bars Affect the Evolution of Disc Galaxies?
Bars in disc galaxies help stabilize their evolution by reducing their dependence on environmental factors. Unbarred galaxies show strong environmental effects on star formation, color, and metallicity, while barred galaxies exhibit weaker variations. Bars likely regulate internal processes, such as gas movement and star formation, making them crucial in galaxy evolution. This study underscores the importance of bars in shaping galactic properties, using data from the MaNGA survey.
The Role of Galactic Bulges in Shaping Stellar Bars and Box-Peanut Features
Rachel McClure and her team explored how classical bulges impact galactic bars and Boxy/Peanut X-Features (BPX) in disk galaxies. Simulations showed heavier bulges stabilize bars, slow their growth, and lead to steady BPX formation, while galaxies without bulges experience rapid, unstable changes. BPX features form through resonant orbital interactions, with bulges moderating their growth and evolution.
Mapping the LMC Bar: A Closer Look at the Structure of a Neighboring Galaxy
Himansh Rathore and colleagues used Gaia DR3 data to map the unusual structure of the Large Magellanic Cloud's (LMC) central bar. They addressed crowding issues that hinder star counts in dense regions by developing a “completeness map” to correct for missing stars. With this method, they measured the bar’s position, size, and orientation precisely, finding it to be offset from the galaxy’s center. Their findings support the idea that recent interactions with the Small Magellanic Cloud (SMC) likely influenced the LMC’s unusual bar structure. This technique could also help study other crowded galaxy systems.