Haro 11: Where is the Lyman Continuum Source?

Abstract

Identifying the mechanism by which high energy Lyman continuum (LyC) photons escaped from early galaxies is one of the most pressing questions in cosmic evolution. Haro 11 is the best known local LyC leaking galaxy, providing an important opportunity to test our understanding of LyC escape. The observed LyC emission in this galaxy presumably originates from one of the three bright, photoionizing knots known as A, B, and C. It is known that Knot C has strong Lyα emission, and Knot B hosts an unusually bright ultraluminous X-ray source, which may be a low-luminosity AGN. To clarify the LyC source, we carry out ionization-parameter mapping (IPM) by obtaining narrow-band imaging from the Hubble Space Telescope WFC3 and ACS cameras to construct spatially resolved ratio maps of [Oiii]/[Oii] emission from the galaxy. IPM traces the ionization structure of the interstellar medium and allows us to identify optically thin regions. To optimize the continuum subtraction, we introduce a new method for determining the best continuum scale factor derived from the mode of the continuumsubtracted, image flux distribution. We find no conclusive evidence of LyC escape from Knots B or C, but instead, we identify a high-ionization region extending over at least 1 kpc from Knot A. Knot A shows evidence of an extremely young age ( 1 Myr), perhaps containing very massive stars (> 100 M ). It is weak in Lyα, so if it is confirmed as the LyC source, our results imply that LyC emission may be independent of Lyα emission.

Gravitational-wave astronomy: delivering on the promises

“…GW151226 [8] and GW170104 [9]-have shown that the early estimates for binary sources were, if anything, not optimistic enough. And shortly after the meeting, LIGO and the upgraded Virgo detector [10] announced not only a further binary black hole detection [11] but, most excitingly, the first detection of a binary neutron star merger [12], an event that was accompanied by a massive campaign of electromagnetic observations [13]. In view of these discoveries, we shall assess the promise of the very bright new era of gravitational-wave astronomy.…”

“…Over 70 different observing partners of LIGO and Virgo responded, locating the counterpart within half a day. The details of all this activity are reported in the first-ever gravitational-wave multi-messenger observation paper [13].…”

No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations

“…High-resolution, spatially resolved spectroscopic data of some LyC leakers in the nearby Universe have been obtained recently to address this question (e.g. Keenan et al 2017;Micheva et al 2018;Menacho et al 2019). A comparably detailed theoretical investigation is demanded by these observations.…”

Bayesian approach to gravitational wave multi-messenger astronomy

“…比如在引力 波-电磁波对应体的一个清楚的物理联系就是双中 子星并合提供了引力波与电磁波的能量源. 与电磁 波宿主星系(例如文献 [90][91][92])已经有了很好的研究 不同, 目前仅仅观测到一个引力波源的宿主星系 [3] , 引力波宿主星系的更多性质将是未来更多引力波事 件被发现后, 在群族性质方向重要的课题(参见第4 节). 在这个观测大三角的图景下, 我们需要一个数 学方法来获取共同参数的信息以实现联合探测, 获 取其他有内秉联系的物理参数以探究二者之间物理 联系.…”