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The CALYMHA survey: Lyα escape fraction and its dependence on galaxy properties at z = 2.23

Matthee, J.; Sobral, D.; Oteo, I.; Best, P.; Smail, I.; Röttgering, H.; Paulino-Afonso, A.

The CALYMHA survey: Lyα escape fraction and its dependence on galaxy properties at z = 2.23 Thumbnail


Authors

J. Matthee

D. Sobral

I. Oteo

P. Best

H. Röttgering

A. Paulino-Afonso



Abstract

We present the first results from our CAlibrating LYMan-α with Hα (CALYMHA) pilot survey at the Isaac Newton Telescope. We measure Lyα emission for 488 Hα selected galaxies at z = 2.23 from HiZELS in the COSMOS and UDS fields with a specially designed narrow-band filter (λc = 3918 Å, Δλ= 52 Å). We find 17 dual Hα-Lyα emitters (fLyα > 5 × 10−17 erg s−1 cm−2, of which 5 are X-ray AGN). For star-forming galaxies, we find a range of Lyα escape fractions (fesc, measured with 3″ apertures) from 2%−30%. These galaxies have masses from 3 × 108 M⊙ to 1011 M⊙ and dust attenuations E(B − V) = 0 − 0.5. Using stacking, we measure a median escape fraction of 1.6 ± 0.5% (4.0 ± 1.0% without correcting Hα for dust), but show that this depends on galaxy properties. The stacked fesc tends to decrease with increasing SFR and dust attenuation. However, at the highest masses and dust attenuations, we detect individual galaxies with fesc much higher than the typical values from stacking, indicating significant scatter in the values of fesc. Relations between fesc and UV slope are bimodal, with high fesc for either the bluest or reddest galaxies. We speculate that this bimodality and large scatter in the values of fesc is due to additional physical mechanisms such as outflows facilitating fesc for dusty/massive systems. Lyα is significantly more extended than Hα and the UV. fesc continues to increase up to at least 20 kpc (3σ, 40 kpc [2σ]) for typical SFGs and thus the aperture is the most important predictor of fesc.

Citation

Matthee, J., Sobral, D., Oteo, I., Best, P., Smail, I., Röttgering, H., & Paulino-Afonso, A. (2016). The CALYMHA survey: Lyα escape fraction and its dependence on galaxy properties at z = 2.23. Monthly Notices of the Royal Astronomical Society, 458(1), 449-467. https://doi.org/10.1093/mnras/stw322

Journal Article Type Article
Acceptance Date Feb 8, 2016
Online Publication Date Feb 10, 2016
Publication Date May 1, 2016
Deposit Date Feb 16, 2016
Publicly Available Date Mar 28, 2024
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 458
Issue 1
Pages 449-467
DOI https://doi.org/10.1093/mnras/stw322
Keywords Galaxies: high-redshift, Galaxies: evolution, Galaxies: ISM.
Related Public URLs http://adsabs.harvard.edu/abs/2016MNRAS.tmp..106M

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Copyright Statement
Advance online version This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


Published Journal Article (Final published version) (4.8 Mb)
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