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

Journal Article · Wed Mar 01 04:00:00 EST 2017 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8213/AA5FF7· OSTI ID:22869270

Bian, Fuyan ^[1]; Fan, Xiaohui; McGreer, Ian ^[2]; Cai, Zheng ^[3]; Jiang, Linhua ^[4]

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1. Research School of Astronomy and Astrophysics, Mt Stromlo Observatory, Australian National University, Canberra, ACT 2611 (Australia)
2. Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721 (United States)
3. UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
4. Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

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{sub ∗}/M{sub ⊙})=9.14{sub −0.04}{sup +0.07} and SFR is 12.5{sub −7.4}{sup +3.8} M{sub ⊙} yr{sup −1} after correcting the magnification. This galaxy has a young galaxy age of 127 Myr and a compact galaxy size of r{sub 1/2}=2.4 kpc. The HST UV imaging observations cover the rest-frame Lyman continuum (LyC) emission (∼800 Å) 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 f{sub abs,esc}>28%--57% based on the flux density ratio between 1700 and 800 Å (f{sub 1700}/f{sub 800}). The morphology of the LyC emission in the F275W images is extended and follows the morphology of the UV continuum morphology in the F606W images, suggesting that the f {sub 800} is not from foreground contaminants. We find that the region with a high star formation rate surface density has a lower f{sub 1700}/f{sub 800} (higher f{sub 800}/f{sub 1700}) 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.

• OSTI ID: 22869270
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 837; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMOLOGY
FLUX DENSITY
GALAXIES
LYMAN LINES
MASS
MORPHOLOGY
PHOTONS
RED SHIFT
STARS