Does radiative feedback make faint z > 6 galaxies look small?

Ploeckinger, Sylvia; Schaye, Joop; Hacar, Alvaro; Maseda, Michael V; Hodge, Jacqueline A; Bouwens, Rychard J

Abstract

Recent observations of lensed sources have shown that the faintest (⁠MUV≈−15mag⁠) galaxies observed at z = 6−8 appear to be extremely compact. Some of them have inferred sizes of less than 40 pc for stellar masses between 106 and 107M⊙⁠, comparable to individual super star clusters or star cluster complexes at low redshift. High-redshift, low-mass galaxies are expected to show a clumpy, irregular morphology and if star clusters form in each of these well-separated clumps, the observed galaxy size would be much larger than the size of an individual star-forming region. As supernova explosions impact the galaxy with a minimum delay time that exceeds the time required to form a massive star cluster, other processes are required to explain the absence of additional massive star-forming regions. In this work, we investigate whether the radiation of a young massive star cluster can suppress the formation of other detectable clusters within the same galaxy already before supernova feedback can affect the galaxy. We find that in low-mass (⁠M200≲1010M⊙⁠) haloes, the radiation from a compact star-forming region with an initial mass of 107M⊙ can keep gas clumps with Jeans masses larger than ≈107M⊙ warm and ionized throughout the galaxy. In this picture, the small intrinsic sizes measured in the faintest z = 6−8 galaxies are a natural consequence of the strong radiation field that stabilizes massive gas clumps. A prediction of this mechanism is that the escape fraction for ionizing radiation is high for the extremely compact, high-z sources.

Citation

Ploeckinger, S., Schaye, J., Hacar, A., Maseda, M. V., Hodge, J. A., & Bouwens, R. J. (2019). Does radiative feedback make faint z > 6 galaxies look small?. Monthly Notices of the Royal Astronomical Society, 484(3), 4379-4392. https://doi.org/10.1093/mnras/stz173

• Journal Article Type: Article
• Acceptance Date: Jan 11, 2019
• Online Publication Date: Jan 16, 2019
• Publication Date: Apr 30, 2019
• Deposit Date: Apr 11, 2019
• Publicly Available Date: Apr 11, 2019
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 484
• Issue: 3
• Pages: 4379-4392
• DOI: https://doi.org/10.1093/mnras/stz173
• Public URL: https://durham-repository.worktribe.com/output/1333267