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We present new observations of Lyman-$\alpha$ (Ly$\alpha$) Blob 1 (LAB1) in the SSA22 protocluster region ($z$ = 3.09) using the Keck Cosmic Web Imager (KCWI) and the Keck Multi-object Spectrometer for Infrared Exploration (MOSFIRE). By…

Astrophysics of Galaxies · Physics 2021-01-21 Zhihui Li , Charles C. Steidel , Max Gronke , Yuguang Chen

Lyman-$\alpha$ photons are resonantly scattered by neutral hydrogen, and may therefore trace both the spatial extent and the kinematics of the gas surrounding galaxies. We present new observations of the extended Ly$\alpha$ halo of…

Astrophysics of Galaxies · Physics 2018-08-08 Dawn K. Erb , Charles C. Steidel , Yuguang Chen

Lyman-$\alpha$ emission, which owing to its resonant nature strongly couples the emergent line profile to gas kinematics, is a key observable for probing outflows from star-forming galaxies in the early universe. Inferences of outflow…

Astrophysics of Galaxies · Physics 2025-07-31 James Nianias , Jeremy Lim , Yik Lok Wong , Gordon Wong

Galactic outflows play a major role in the evolution of galaxies, but the underlying physical processes are poorly understood. This is mainly because we have little information about the outflow structure, especially on large scales. In…

Astrophysics of Galaxies · Physics 2020-05-19 Bingjie Wang , Timothy M. Heckman , Guangtun Zhu , Colin A. Norman

JWST has recently sparked a new era of Ly$\alpha$ spectroscopy, delivering the first measurements of the Ly$\alpha$ escape fraction and velocity profile in typical galaxies at $z\simeq6-10$. These observations offer new prospects for…

We present HI line profiles for various models of circumstellar shells around red giants. In the calculations we take into account the effect of the background at 21 cm, and show that in some circumstances it may have an important effect on…

Solar and Stellar Astrophysics · Physics 2015-03-05 Do Thi Hoai , Pham Thi Nhung , Eric Gérard , Lynn D. Matthews , Eva Villaver , Thibaut Le Bertre

Understanding the escape of Lyman continuum (LyC) and Lyman alpha (Lya) photons from molecular clouds is one of the keys to constraining the reionization history of the Universe and the evolution of galaxies at high redshift. Using a set of…

Understanding the escape of Lyman continuum (LyC) and Lyman $\alpha$ (Ly$\alpha$) photons from giant molecular clouds (GMCs) is crucial if we are to study the reionization of the Universe and to interpret spectra of observed galaxies at…

Astrophysics of Galaxies · Physics 2022-03-14 Taysun Kimm , Rebekka Bieri , Sam Geen , Joakim Rosdahl , Jérémy Blaizot , Léo Michel-Dansac , Thibault Garel

We present predictions for the abundance of Ly-$\alpha$ emitters in hierarchical structure formation models. We use the {\tt GALFORM} semi-analytical model to explore the impact on the predicted counts of varying assumptions about the…

An astrosphere is a vast, tailed bubble-like volume around a star, formed through the interaction between the stellar magnetic field, the stellar wind, and the interstellar medium (ISM). Detecting and characterizing astrospheres are…

Solar and Stellar Astrophysics · Physics 2026-05-28 Ziqi Wu , Tom Van Doorsselaere , Jiansen He , Hugues Sana , Nicholas Jannsen , Tianhang Chen , Weining Wang , Zheng Sun

Prompted by the H I Ly$\alpha$ absorption associated with the X-ray ultra-fast outflow at -17,300 $\rm km~s^{-1}$ in the quasar PG~1211+143, we have searched archival UV spectra at the expected locations of H I Ly$\alpha$ absorption for a…

Astrophysics of Galaxies · Physics 2019-01-24 G. A. Kriss , J. C. Lee , A. Danehkar

We report Hubble Space Telescope/Cosmic Origins Spectrograph observations of the Ly$\alpha$ emission and interstellar absorption lines in a sample of ten star-forming galaxies at $z\sim0.2$. Selected on the basis of high equivalent width…

Astrophysics of Galaxies · Physics 2015-08-19 Alaina Henry , Claudia Scarlata , Crystal L. Martin , Dawn Erb

The Lyman alpha line is a robust tracer of high redshift galaxies. We present estimates of Lyman alpha emission from a protogalactic halo illuminated by UV background radiation fields with various intensities. For this purpose, we performed…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 M. A. Latif , Dominik R. G. Schleicher , M. Spaans , S. Zaroubi

We model the spectra and surface brightness distributions for the Lyman alpha (Lya) radiation expected from protogalaxies that are caught in the early stages of their assembly. We use the results of a companion paper to characterize the…

Astrophysics · Physics 2008-11-26 Mark Dijkstra , Zoltan Haiman , Marco Spaans

One of the current challenges in galaxy evolution studies is to establish the mechanisms that govern the escape of ionizing radiation from galaxies. Here, we investigate the connection between Lyman Continuum (LyC) escape and the conditions…

Hydrodynamic simulations can connect outflow observables to the physical conditions of outflowing gas. Here, we use simulations of isolated disk galaxies ranging from dwarf mass ($M_{200} = 10^{10}\mathrm{M}_{\odot}$) to Milky Way mass…

We present observations of a peculiar Lyman alpha-emitting galaxy at redshift 3.344, discovered in a deep, blind spectroscopic survey for faint Lyman alpha emitters with the Magellan II telescope in the Hubble Ultra Deep Field (HUDF). The…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Michael Rauch , George D. Becker , Martin G. Haehnelt , Jean-Rene Gauthier , Swara Ravindranath , Wallace L. W. Sargent

We examine emission from a young protostellar object (YPO) with three-dimensional ideal MHD simulations and three-dimensional non-local thermodynamic equilibrium (non-LTE) line transfer calculations, and show the first results. To calculate…

Solar and Stellar Astrophysics · Physics 2015-05-13 M. Yamada , M. N. Machida , S. Inutsuka , K. Tomisaka

We investigate the detectability of Lyman-$\alpha$ (Ly$\alpha$) emission from galaxies at the onset of cosmic reionization, aiming to understand the conditions necessary for detecting high-redshift sources like JADES-GS-z13-1-LA at $z=13$.…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-12 Yuxiang Qin , J. Stuart B. Wyithe

Cosmological simulations with gas provide a detailed description of the intergalactic medium, making possible predictions of neutral hydrogen absorption in the spectra of background QSOs. We present results from a high-resolution…

Astrophysics · Physics 2009-10-28 Lars Hernquist , Neal Katz , David H. Weinberg , Jordi Miralda-Escude