The Lyman-alpha and Continuum Origins Survey II: the connection between the escape of ionizing radiation and Lyman-alpha halos in star-forming galaxies

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Bibliographic Details
Main Authors:	Saldana-Lopez, A., Hayes, M. J., Reste, A. Le, Scarlata, C., Melinder, J., Henry, A., Leclercq, F., Garel, T., Amorin, R., Atek, H., Bait, O., Carr, C. A., Chisholm, J., Flury, S. R., Heckman, T. M., Jaskot, A. E., Jung, I., Ji, Z., Komarova, L., Lin, Y-H., Oey, M. S., Ostlin, G., Pentericci, L., Runnholm, A., Schaerer, D., Thuan, T. X., Xu, X.
Format:	Preprint
Published:	2025
Subjects:	Astrophysics of Galaxies
Online Access:	Acceder al recurso
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_version_	1866914345286369280
author	Saldana-Lopez, A. Hayes, M. J. Reste, A. Le Scarlata, C. Melinder, J. Henry, A. Leclercq, F. Garel, T. Amorin, R. Atek, H. Bait, O. Carr, C. A. Chisholm, J. Flury, S. R. Heckman, T. M. Jaskot, A. E. Jung, I. Ji, Z. Komarova, L. Lin, Y-H. Oey, M. S. Ostlin, G. Pentericci, L. Runnholm, A. Schaerer, D. Thuan, T. X. Xu, X.
author_facet	Saldana-Lopez, A. Hayes, M. J. Reste, A. Le Scarlata, C. Melinder, J. Henry, A. Leclercq, F. Garel, T. Amorin, R. Atek, H. Bait, O. Carr, C. A. Chisholm, J. Flury, S. R. Heckman, T. M. Jaskot, A. E. Jung, I. Ji, Z. Komarova, L. Lin, Y-H. Oey, M. S. Ostlin, G. Pentericci, L. Runnholm, A. Schaerer, D. Thuan, T. X. Xu, X.
contents	One of the current challenges in galaxy evolution studies is to establish the mechanisms that govern the escape of ionizing radiation from galaxies. Here, we investigate the connection between Lyman Continuum (LyC) escape and the conditions of the Circumgalactic Medium (CGM), as probed by Ly$α$ halos (LAHs) in emission. We use Ly$α$ and UV continuum imaging data from the Lyman alpha and Continuum Origins Survey (LaCOS), targeting 42 nearby ($z \simeq 0.3$), star-forming galaxies with LyC observations (escape fractions of $f_{\rm esc}^{\rm LyC} \simeq 0.01-0.49$). LaCOS galaxies show extended Ly$α$ emission ubiquitously, with LyC emitters (LCEs) having more compact Ly$α$ morphologies than non-LCEs, and Ly$α$ spatial offsets that do not exceed the extent of the UV continuum. We model the diffuse LAHs using a combined Sérsic plus exponential 2D profile, and find that the characteristic scale length of the Ly$α$ halo is ten times larger than the UV, on average. We unveil a significant anti-correlation between $f_{\rm esc}^{\rm LyC}$ and the Ly$α$ Halo Fraction (HF, or contribution of the halo to the total Ly$α$ luminosity), that we propose as a new LyC indicator. Our observations show that halo scale lengths and HFs both scale positively with the optical depth of the neutral gas in the ISM, revealing a picture in which Ly$α$ and LyC photons in LCEs either emerge directly from the central starbursts or escape isotropically and, in the case of Ly$α$, minimize the number of scattering interactions in a less-extended CGM.
format	Preprint
id	arxiv_https___arxiv_org_abs_2504_07074
institution	arXiv
publishDate	2025
record_format	arxiv
spellingShingle	The Lyman-alpha and Continuum Origins Survey II: the connection between the escape of ionizing radiation and Lyman-alpha halos in star-forming galaxies Saldana-Lopez, A. Hayes, M. J. Reste, A. Le Scarlata, C. Melinder, J. Henry, A. Leclercq, F. Garel, T. Amorin, R. Atek, H. Bait, O. Carr, C. A. Chisholm, J. Flury, S. R. Heckman, T. M. Jaskot, A. E. Jung, I. Ji, Z. Komarova, L. Lin, Y-H. Oey, M. S. Ostlin, G. Pentericci, L. Runnholm, A. Schaerer, D. Thuan, T. X. Xu, X. Astrophysics of Galaxies One of the current challenges in galaxy evolution studies is to establish the mechanisms that govern the escape of ionizing radiation from galaxies. Here, we investigate the connection between Lyman Continuum (LyC) escape and the conditions of the Circumgalactic Medium (CGM), as probed by Ly$α$ halos (LAHs) in emission. We use Ly$α$ and UV continuum imaging data from the Lyman alpha and Continuum Origins Survey (LaCOS), targeting 42 nearby ($z \simeq 0.3$), star-forming galaxies with LyC observations (escape fractions of $f_{\rm esc}^{\rm LyC} \simeq 0.01-0.49$). LaCOS galaxies show extended Ly$α$ emission ubiquitously, with LyC emitters (LCEs) having more compact Ly$α$ morphologies than non-LCEs, and Ly$α$ spatial offsets that do not exceed the extent of the UV continuum. We model the diffuse LAHs using a combined Sérsic plus exponential 2D profile, and find that the characteristic scale length of the Ly$α$ halo is ten times larger than the UV, on average. We unveil a significant anti-correlation between $f_{\rm esc}^{\rm LyC}$ and the Ly$α$ Halo Fraction (HF, or contribution of the halo to the total Ly$α$ luminosity), that we propose as a new LyC indicator. Our observations show that halo scale lengths and HFs both scale positively with the optical depth of the neutral gas in the ISM, revealing a picture in which Ly$α$ and LyC photons in LCEs either emerge directly from the central starbursts or escape isotropically and, in the case of Ly$α$, minimize the number of scattering interactions in a less-extended CGM.
title	The Lyman-alpha and Continuum Origins Survey II: the connection between the escape of ionizing radiation and Lyman-alpha halos in star-forming galaxies
topic	Astrophysics of Galaxies
url	https://arxiv.org/abs/2504.07074