High lyman continuum escape fraction in a lensed young compact dwarf galaxy at z = 2.5

Fuyan Bian, Xiaohui Fan, Ian McGreer, Zheng Cai, Linhua Jiang

Research output: Contribution to journalArticlepeer-review


We present the HST WFC3/F275W UV imaging observations of A2218-Flanking, a lensed compact dwarf galaxy at redshift z ≈ 2.5. The stellar mass of A2218-Flanking is log(M/M☉) = 9.14+0−0..0704 and SFR is 12.5+3−7..84 M☉ yr−1 after correcting the magnification. This galaxy has a young galaxy age of 127 Myr and a compact galaxy size of r1/2 = 2.4 kpc. The HST UV imaging observations cover the rest-frame Lyman continuum (LyC) emission (∼ 800Å) from A2218-Flanking. We firmly detect (14σ) the LyC emission in A2218-Flanking in the F275W image. Together with the HST F606W images, we find that the absolute escape fraction of LyC is fabs,esc > 28 − 57% based on the flux density ratio between 1700Å and 800Å (f1700/f800). The morphology of the LyC emission in the F275W images is extended and well follows the morphology of the UV continuum morphology in the F606W images, suggesting that the f800 is not from foreground contaminants. We find that the region with a high star formation rate surface density has a lower f1700/f800 (higher f800/f1700) ratio than the diffused regions, suggesting that LyC photons are more likely to escape from the region with the intensive star-forming process. We compare the properties of galaxies with and without LyC detections and find that LyC photons are easier to escape in low mass galaxies.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Feb 21 2017


  • Cosmology: observations
  • Galaxies: high-redshift
  • Gravitational lensing: strong
  • Reionization

ASJC Scopus subject areas

  • General

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