English

Witnessing an extreme, highly efficient galaxy formation mode with resolved Ly$\alpha$ and LyC emission

Astrophysics of Galaxies 2024-10-30 v2

Abstract

J1316+2614 at z=3.613 is the UV-brightest (MUVM_{UV} = -24.7) and strongest Lyman continuum (LyC, fescLyCf_{esc}^{LyC} \approx 90%) emitting star-forming galaxy known, showing also signatures of inflowing gas from its blue-dominated Lyα\alpha profile. Here, we present high-resolution imaging with the HST and VLT of the LyC, Lyα\alpha, rest-UV, and optical emission of J1316+2614. Detailed analysis of the LyC and UV light distributions reveals compact yet resolved profiles, with LyC and UV morphologies showing identical half-light radii of \simeq 220 pc. The continuum-subtracted Lyα\alpha emission reveals an extended filamentary structure of \simeq 6.0 kpc oriented south-north with only weak/residual flux within the stellar core, suggesting a Lyα\alpha "hole". J1316+2614 presents remarkably high SFR and stellar mass surface densities of log(ΣSFR\Sigma_{SFR} [MM_{\odot}/yr/kpc^2]) = 3.47±\pm0.11 and log(ΣM\Sigma_{M} [MM_{\odot}/pc^2]) = 4.20±\pm0.06, respectively, which are among the highest observed in star-forming galaxies. Our findings indicate that J1316+2614 is a powerful, young, and compact starburst, leaking significant LyC photons due to the lack of gas and dust within the starburst. We explore the conditions for gas expulsion using a simple energetic balance and find that, given the strong binding force in J1316+2614, a high star formation efficiency (ϵSF0.7\epsilon_{SF} \geq 0.7) is necessary to remove the gas and explain its exposed nature. Our results thus suggest a close link between high ϵSF\epsilon_{SF} and high fescLyCf_{esc}^{LyC}. This high efficiency can also naturally explain the remarkably high SFR, UV-luminosity, and efficient mass growth of J1316+2614, where at least 62% of its mass formed in the last 6 Myr. J1316+2614 may exemplify an intense, feedback-free starburst with a high ϵSF\epsilon_{SF}, similar to those proposed for UV-bright galaxies at high redshifts. (ABRIDGED)

Keywords

Cite

@article{arxiv.2407.18804,
  title  = {Witnessing an extreme, highly efficient galaxy formation mode with resolved Ly$\alpha$ and LyC emission},
  author = {R. Marques-Chaves and D. Schaerer and E. Vanzella and A. Verhamme and M. Dessauges-Zavadsky and J. Chisholm and F. Leclercq and A. Upadhyaya and J. Alvarez-Marquez and L. Colina and T. Garel and M. Messa},
  journal= {arXiv preprint arXiv:2407.18804},
  year   = {2024}
}

Comments

15 pages and 9 figures. Accepted for publication in A&A