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arXiv · 2310.02314

Bursty star formation and galaxy-galaxy interactions in low-mass galaxies 1 Gyr after the Big Bang

Yoshihisa Asada·Marcin Sawicki·Roberto Abraham·Maruša Bradač·Gabriel Brammer·Guillaume Desprez·Vince Estrada-Carpenter·Kartheik Iyer·Nicholas Martis·Jasleen Matharu·Lamiya Mowla·Adam Muzzin·Gaël Noirot·Ghassan T. E. Sarrouh·Victoria Strait·Chris J. Willott·Anishya Harshan
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Abstract

We use CANUCS JWST/NIRCam imaging of galaxies behind the gravitationally-lensing cluster MACS J0417.5-1154 to investigate star formation burstiness in low-mass ($M_\star\sim10^8\ M_\odot$) galaxies at $z\sim4.7-6.5$. Our sample of 123 galaxies is selected using the Lyman break selection and photometric emission-line excess methods. Sixty per cent of the 123 galaxies in this sample have H$\alpha$-to-UV flux ratios that deviate significantly from the range of $\eta_{1500}$ values consistent with smooth and steady star formation histories. This large fraction indicates that the majority of low-mass galaxies is experiencing bursty star formation histories at high redshift. We also searched for interacting galaxies in our sample and found that they are remarkably common ($\sim40$ per cent of the sample). Compared to non-interacting galaxies, interacting galaxies are more likely to have very low H$\alpha$-to-UV ratios, suggesting that galaxy-galaxy interactions enhance star formation burstiness and enable faster quenching (with timescales of $\lesssim100$ Myr) that follows the rapid rise of star formation activity. Given the high frequency of galaxy-galaxy interactions and the rapid SFR fluctuations they appear to cause, we conclude that galaxy-galaxy interactions could be a leading cause of bursty star formation in low-mass, high-$z$ galaxies. They could thus play a significant role in the evolution of the galaxy population at early cosmological times.

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Yoshihisa Asada, Marcin Sawicki, Roberto Abraham, Maruša Bradač, Gabriel Brammer, Guillaume Desprez, Vince Estrada-Carpenter, Kartheik Iyer, Nicholas Martis, Jasleen Matharu, Lamiya Mowla, Adam Muzzin, Gaël Noirot, Ghassan T. E. Sarrouh, Victoria Strait, Chris J. Willott, Anishya Harshan. 2023-10-03. Bursty star formation and galaxy-galaxy interactions in low-mass galaxies 1 Gyr after the Big Bang. https://arxiv.org/abs/2310.02314

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