%0 Generic %1 vanzella2016hubble %A Vanzella, E. %A de Barros, S. %A Vasei, K. %A Alavi, A. %A Giavalisco, M. %A Siana, B. %A Grazian, A. %A Hasinger, G. %A Suh, H. %A Cappelluti, N. %A Vito, F. %A Amorin, R. %A Balestra, I. %A Brusa, M. %A Calura, F. %A Castellano, M. %A Comastri, A. %A Fontana, A. %A Gilli, R. %A Mignoli, M. %A Pentericci, L. %A Vignali, C. %A Zamorani, G. %D 2016 %K escape fraction imaging %T Hubble imaging of the ionizing radiation from a star-forming galaxy at z=3.2 with fesc>50% %U http://arxiv.org/abs/1602.00688 %X Star-forming galaxies are considered to be the leading candidate sources that dominate the cosmic reionization at z>7, and the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently a active line of research. We have observed a star-forming galaxy at z=3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730-890A rest-frame, and detect LyC emission. This galaxy is very compact and also has large Oxygen ratio OIII5007/OII3727 (>=10). No nuclear activity is revealed from optical/near-infrared spectroscopy and deep multi-band photometry (including the 6Ms X-ray, Chandra). The measured escape fraction of ionizing radiation spans the range 50-100\%, depending on the IGM attenuation. The LyC emission is detected at S/N=10 with m(F336W)=27.57+/-0.11 and it is spatially unresolved, with effective radius R_e<200pc. Predictions from photoionization and radiative transfer models are in line with the properties reported here, indicating that stellar winds and supernova explosions in a nucleated star-forming region can blow cavities generating density-bounded conditions compatible with optically thin media. Irrespective to the nature of the ionizing radiation, spectral signatures of these sources over the entire electromagnetic spectrum are of central importance for their identification during the epoch of reionization, when the LyC is unobservable. Intriguingly, the Spitzer/IRAC photometric signature of intense rest-frame optical emissions (OIII+Hbeta) observed recently at z~7.5-8.5 is similar to what is observed in this galaxy. Only the James Webb Space Telescope will measure optical line ratios at z>7 allowing a direct comparison with lower redshift LyC emitters, as reported here.

@misc{vanzella2016hubble, abstract = {Star-forming galaxies are considered to be the leading candidate sources that dominate the cosmic reionization at z>7, and the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently a active line of research. We have observed a star-forming galaxy at z=3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730-890A rest-frame, and detect LyC emission. This galaxy is very compact and also has large Oxygen ratio [OIII]5007/[OII]3727 (>=10). No nuclear activity is revealed from optical/near-infrared spectroscopy and deep multi-band photometry (including the 6Ms X-ray, Chandra). The measured escape fraction of ionizing radiation spans the range 50-100\%, depending on the IGM attenuation. The LyC emission is detected at S/N=10 with m(F336W)=27.57+/-0.11 and it is spatially unresolved, with effective radius R_e<200pc. Predictions from photoionization and radiative transfer models are in line with the properties reported here, indicating that stellar winds and supernova explosions in a nucleated star-forming region can blow cavities generating density-bounded conditions compatible with optically thin media. Irrespective to the nature of the ionizing radiation, spectral signatures of these sources over the entire electromagnetic spectrum are of central importance for their identification during the epoch of reionization, when the LyC is unobservable. Intriguingly, the Spitzer/IRAC photometric signature of intense rest-frame optical emissions ([OIII]+Hbeta) observed recently at z~7.5-8.5 is similar to what is observed in this galaxy. Only the James Webb Space Telescope will measure optical line ratios at z>7 allowing a direct comparison with lower redshift LyC emitters, as reported here.}, added-at = {2016-02-03T10:01:40.000+0100}, author = {Vanzella, E. and de Barros, S. and Vasei, K. and Alavi, A. and Giavalisco, M. and Siana, B. and Grazian, A. and Hasinger, G. and Suh, H. and Cappelluti, N. and Vito, F. and Amorin, R. and Balestra, I. and Brusa, M. and Calura, F. and Castellano, M. and Comastri, A. and Fontana, A. and Gilli, R. and Mignoli, M. and Pentericci, L. and Vignali, C. and Zamorani, G.}, biburl = {https://www.bibsonomy.org/bibtex/2bf756b8b011d8b7fd54f1cc8640ea2f4/miki}, description = {[1602.00688] Hubble imaging of the ionizing radiation from a star-forming galaxy at z=3.2 with fesc&gt;50%}, interhash = {11df8f36b34fc0e9fd8e1a52b4bf5711}, intrahash = {bf756b8b011d8b7fd54f1cc8640ea2f4}, keywords = {escape fraction imaging}, note = {cite arxiv:1602.00688Comment: 6 pages, 5 figures, ApJ submitted (comments welcome)}, timestamp = {2016-02-03T10:01:40.000+0100}, title = {Hubble imaging of the ionizing radiation from a star-forming galaxy at z=3.2 with fesc>50%}, url = {http://arxiv.org/abs/1602.00688}, year = 2016 }