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The escape fraction of Lyman-continuum (LyC) photons (f(esc)) is a key parameter for determining the sources of cosmic reionization at z >= 6. At these redshifts, owing to the opacity of the intergalactic medium, the LyC emission cannot be measured directly. However, LyC leakers during the epoch of reionization could be identified using indirect indicators that have been extensively tested at low and intermediate redshifts. These include a high [OIII]/[OII] flux ratio, high star-formation surface density, and compact sizes. In this work, we present observations of 29 4.5 = 6 have provided a substantial contribution to cosmic reionization.

The escape fraction of Lyman-continuum (LyC) photons (f(esc)) is a key parameter for determining the sources of cosmic reionization at z >= 6. At these redshifts, owing to the opacity of the intergalactic medium, the LyC emission cannot be measured directly. However, LyC leakers during the epoch of reionization could be identified using indirect indicators that have been extensively tested at low and intermediate redshifts. These include a high [OIII]/[OII] flux ratio, high star-formation surface density, and compact sizes. In this work, we present observations of 29 4.5 = 6 have provided a substantial contribution to cosmic reionization.

We present our lens mass model of SMACS J0723.3-7327, the first strong gravitational lens observed by the James Webb Space Telescope (JWST). We use data from the Hubble Space Telescope and the Multi Unit Spectroscopic Explorer (MUSE) to build our 'pre-JWST' lens model and then refine it with newly available JWST near-infrared imaging in our JWST model. To reproduce the positions of all multiple lensed images with good accuracy, the adopted mass parameterisation consists of one cluster-scale component, accounting mainly for the dark matter distribution, the galaxy cluster members, and an external shear component. The pre-JWST model has, as constraints, 19 multiple images from six background sources, of which four have secure spectroscopic redshift measurements from this work. The JWST model has more than twice the number of constraints: 30 additional multiple images from another 11 lensed sources. Both models can reproduce the multiple image positions very well, with a delta(rms) of 0 ''.39 and 0 ''.51 for the pre-JWST and JWST models, respectively. The total mass estimates within a radius of 128 kpc (roughly the Einstein radius) are 7.9(-0.2)(+0,3) x 10(13) M-circle dot and 8.7(-0.2)(+0.2) x 10(13) M-circle dot for the pre-JWST and JWST models, respectively. We predict with our mass models the redshifts of the newly detected JWST sources, which is crucial information, especially for systems without spectroscopic measurements, for further studies and follow-up observations. Interestingly, one family detected with JWST is found to be at a very high redshift, z > 7.5 (68% confidence level), and with one image that has a lensing magnification of vertical bar mu vertical bar = 9.5(-0.8)(+0.9), making it an interesting case for future studies. The lens models, including magnification maps and redshifts estimated from the model, are made publicly available, along with the full spectroscopic redshift catalogue from MUSE.

We present our lens mass model of SMACS J0723.3-7327, the first strong gravitational lens observed by the James Webb Space Telescope (JWST). We use data from the Hubble Space Telescope and the Multi Unit Spectroscopic Explorer (MUSE) to build our 'pre-JWST' lens model and then refine it with newly available JWST near-infrared imaging in our JWST model. To reproduce the positions of all multiple lensed images with good accuracy, the adopted mass parameterisation consists of one cluster-scale component, accounting mainly for the dark matter distribution, the galaxy cluster members, and an external shear component. The pre-JWST model has, as constraints, 19 multiple images from six background sources, of which four have secure spectroscopic redshift measurements from this work. The JWST model has more than twice the number of constraints: 30 additional multiple images from another 11 lensed sources. Both models can reproduce the multiple image positions very well, with a delta(rms) of 0 ''.39 and 0 ''.51 for the pre-JWST and JWST models, respectively. The total mass estimates within a radius of 128 kpc (roughly the Einstein radius) are 7.9(-0.2)(+0,3) x 10(13) M-circle dot and 8.7(-0.2)(+0.2) x 10(13) M-circle dot for the pre-JWST and JWST models, respectively. We predict with our mass models the redshifts of the newly detected JWST sources, which is crucial information, especially for systems without spectroscopic measurements, for further studies and follow-up observations. Interestingly, one family detected with JWST is found to be at a very high redshift, z > 7.5 (68% confidence level), and with one image that has a lensing magnification of vertical bar mu vertical bar = 9.5(-0.8)(+0.9), making it an interesting case for future studies. The lens models, including magnification maps and redshifts estimated from the model, are made publicly available, along with the full spectroscopic redshift catalogue from MUSE.

© 2017. The American Astronomical Society. All rights reserved. L.B. and K.I.C. acknowledge the support of the Nederlandse Onderzoekschool voor de Astronomie (NOVA). K.I.C. also acknowledges funding from the European Research Council through the award of the Consolidator Grant ID 681627-BUILDUP. O.L.F. acknowledges funding from the European Research Council Advanced Grant ID 268107-EARLY. P.G. P.-G. acknowledges support from the Spanish Government MINECO Grants AYA2012-31277 and AYA2015-70815-ERC. L.C. acknowledges support from the Spanish Government MINECO Grants AAYA2012-32295., Imaging with the James Webb Space Telescope (JWST) will allow observations of the bulk of distant galaxies at the epoch of reionization. The recovery of their properties, such as age, color excess E(B-V), specific star formation rate (sSFR), and stellar mass, will mostly rely on spectral energy distribution fitting, based on the data provided by JWST's two imager cameras, namely the Near Infrared Camera (NIRCam) and the Mid Infrared Imager (MIRI). In this work we analyze the effect of choosing different combinations of NIRCam and MIRI broadband filters, from 0.6 to 7.7 mu m, on the recovery of these galaxy properties. We performed our tests on a sample of 1542 simulated galaxies, with known input properties, at z = 7-10. We found that, with only eight NIRCam broadbands, we can recover the galaxy age within 0.1 Gyr and the color excess within 0.06 mag for 70% of the galaxies. Additionally, the stellar masses and sSFR are recovered within 0.2 and 0.3 dex, respectively, at z = 7-9. Instead, at z = 10, no NIRCam band traces purely the lambda > 4000 angstrom regime and the percentage of outliers in stellar mass (sSFR) increases by > 20% (> 90%), in comparison to z = 9. The MIRI F560W and F770W bands are crucial to improve the stellar mass and the sSFR estimation at z = 10. When nebular emission lines are present, deriving correct galaxy properties is challenging at any redshift and with any band combination. In particular, the stellar mass is systematically overestimated in up to 0.3 dex on average with NIRCam data alone and including MIRI observations only marginally improves the estimation., Unión Europea. H2020, Unión Europea. FP7, Ministerio de Economía y Competitividad (MINECO), Nederlandse Onderzoekschool voor de Astronomie (NOVA), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub