%0 Generic %1 vanzella2019ionising %A Vanzella, E. %A Caminha, G. B. %A Calura, F. %A Cupani, G. %A Meneghetti, M. %A Castellano, M. %A Rosati, P. %A Mercurio, A. %A Sani, E. %A Grillo, C. %A Gilli, R. %A Mignoli, M. %A Comastri, A. %A Nonino, M. %A Cristiani, S. %A Giavalisco, M. %A Caputi, K. %D 2019 %K library %T Ionising the Intergalactic Medium by Star Clusters ? The first empirical evidence %U http://arxiv.org/abs/1904.07941 %X We present a VLT/X-Shooter spectroscopy of the Lyman continuum (LyC) emitting galaxy Ion2 at z=3.2121 and compare it to that of the recently discovered strongly lensed LyC-emitter at z=2.37, known as the "Sunburst" arc. Three main results emerge from the X-Shooter spectrum: (a) the Lya has three distinct peaks with the central one at the systemic redshift, indicating a ionised tunnel through which both Lya and LyC radiation escape; (b) the large O32 oxygen index (OIII5007 / OII3727) of 9.18_-1.32^+1.82 is compatible to those measured in local (z~0.4) LyC leakers; (c) there are narrow nebular high-ionisation metal lines with \sigma_v < 20 km/s, which confirms the presence of young hot, massive stars. The HeII 1640 appears qualitatively broad, consistent with a young stellar component including Wolf-Rayet stars. Similarly, the Sunburst LyC-emitter shows a triple-peaked Lya profile and spectral features arising from young hot and massive stars. The strong lensing magnification, (> 30-50), makes this exceptional object the very likely first case of gravitationally-bound star cluster ever observed at a cosmological distance, with a stellar mass M ~< 10^7 Msun and an effective radius smaller than 20 pc. Intriguingly, sources like Sunburst but without lensing magnification might appear as Ion2-like galaxies, in which spatially unresolved massive star clusters dominate the ultraviolet emission. This work supports the idea that dense young star clusters can contribute to the ionisation of the IGM through holes created by stellar feedback.

@misc{vanzella2019ionising, abstract = {We present a VLT/X-Shooter spectroscopy of the Lyman continuum (LyC) emitting galaxy Ion2 at z=3.2121 and compare it to that of the recently discovered strongly lensed LyC-emitter at z=2.37, known as the "Sunburst" arc. Three main results emerge from the X-Shooter spectrum: (a) the Lya has three distinct peaks with the central one at the systemic redshift, indicating a ionised tunnel through which both Lya and LyC radiation escape; (b) the large O32 oxygen index ([OIII]5007 / [OII]3727) of 9.18_{-1.32}^{+1.82} is compatible to those measured in local (z~0.4) LyC leakers; (c) there are narrow nebular high-ionisation metal lines with \sigma_v < 20 km/s, which confirms the presence of young hot, massive stars. The HeII 1640 appears qualitatively broad, consistent with a young stellar component including Wolf-Rayet stars. Similarly, the Sunburst LyC-emitter shows a triple-peaked Lya profile and spectral features arising from young hot and massive stars. The strong lensing magnification, (\mu > 30-50), makes this exceptional object the very likely first case of gravitationally-bound star cluster ever observed at a cosmological distance, with a stellar mass M ~< 10^7 Msun and an effective radius smaller than 20 pc. Intriguingly, sources like Sunburst but without lensing magnification might appear as Ion2-like galaxies, in which spatially unresolved massive star clusters dominate the ultraviolet emission. This work supports the idea that dense young star clusters can contribute to the ionisation of the IGM through holes created by stellar feedback.}, added-at = {2019-04-18T05:00:23.000+0200}, author = {Vanzella, E. and Caminha, G. B. and Calura, F. and Cupani, G. and Meneghetti, M. and Castellano, M. and Rosati, P. and Mercurio, A. and Sani, E. and Grillo, C. and Gilli, R. and Mignoli, M. and Comastri, A. and Nonino, M. and Cristiani, S. and Giavalisco, M. and Caputi, K.}, biburl = {https://www.bibsonomy.org/bibtex/28e91e84631c286b75128b2741dff6166/gpkulkarni}, description = {Ionising the Intergalactic Medium by Star Clusters ? The first empirical evidence}, interhash = {e19e76f8a3a2fe4b5f76b427e29f8bf6}, intrahash = {8e91e84631c286b75128b2741dff6166}, keywords = {library}, note = {cite arxiv:1904.07941Comment: 9 pages, 6 figures and 1 table, submitted to MNRAS. Comments welcome}, timestamp = {2019-04-18T05:00:23.000+0200}, title = {Ionising the Intergalactic Medium by Star Clusters ? The first empirical evidence}, url = {http://arxiv.org/abs/1904.07941}, year = 2019 }