Answer to Question #89394 in Astronomy | Astrophysics for fayoo

Question

(b) What is the difference between the density-bounded medium and the picket fence model?
(c) Explain the spectral shape of the perforated shell model.
(d) What is the Sunburst Arc and how was it discovered?

Answer 1

(b) What is the difference between the density-bounded medium and the picket fence model?

Lyman continuum radiation can be allowed to escape a galaxy mainly by two means. In one scenario, the source region scan be surrounded by a largely isotropic gas with a sufficiently low column density of neutral hydrogen N_HI to not completely attenuate the passing Lyman-continuum radiation. This is usually referred to as the density-bounded medium. In a second scenario, the neutral medium is optically thick, but does not completely cover the ionizing sources. This scenario has been referred to as the picket fence model,or the ionization-bounded medium with holes.

(c) Explain the spectral shape of the perforated shell model

Lyman continuum radiation can escape only through open sight lines between dense clumps, while Lyαcan bounce off the boundaries of clumps and thus escape after a few scatterings and only weak radiative transfer effects. The resulting Lyαspectrum is a narrow single-peaked line whose intrinsic shape is nearly.

(d) What is the Sunburst Arc and how was it discovered?

The recently discovered strongly lensed Lyman continuum (LyC) emitter at z=2.37, known as the "Sunburst" arc. Sources like Sunburst but without lensing magnification might appear as Ion2-like galaxies, in which spatially unresolved massive star clusters dominate the ultraviolet emission. It discovered using spectroscopy.