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Author : Haojing Yan
Release : 2003
Genre : Galaxies
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Book Synopsis Probing the Luminosity Function of Galaxies at the Epoch of Reionization by : Haojing Yan
Download or read book Probing the Luminosity Function of Galaxies at the Epoch of Reionization written by Haojing Yan. This book was released on 2003. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Vithal Shet Tilvi
Release : 2011
Genre : Galaxies
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Book Synopsis Luminosity Function of Lyman-alpha Emitters at the Reionization Epoch by : Vithal Shet Tilvi
Download or read book Luminosity Function of Lyman-alpha Emitters at the Reionization Epoch written by Vithal Shet Tilvi. This book was released on 2011. Available in PDF, EPUB and Kindle. Book excerpt: Galaxies with strong Lyman-alpha (Lya) emission line (also called Lya galaxies or emitters) offer an unique probe of the epoch of reionization - one of the important phases when most of the neutral hydrogen in the universe was ionized. In addition, Lya galaxies at high redshifts are a powerful tool to study low-mass galaxy formation. Since current observations suggest that the reionization is complete by redshift z~ 6, it is therefore necessary to discover galaxies at z> 6, to use their luminosity function (LF) as a probe of reionization. I found five z = 7.7 candidate Lya galaxies with line fluxes> 7x10-18 cm/2, from three different deep near-infrared (IR) narrowband (NB) imaging surveys in a volume> 4x104Mpc3. From the spectroscopic followup of four candidate galaxies, and with the current spectroscopic sensitivity, the detection of only the brightest candidate galaxy can be ruled out at 5 sigma level. Moreover, these observations successfully demonstrate that the sensitivity necessary for both, the NB imaging as well as the spectroscopic followup of z~ 8 Lya galaxies can be reached with the current instrumentation. While future, more sensitive spectroscopic observations are necessary, the observed Lya LF at z = 7.7 is consistent with z = 6.6 LF, suggesting that the intergalactic medium (IGM) is relatively ionized even at z = 7.7, with neutral fraction xHI 30%. On the theoretical front, while several models of Lya emitters have been developed, the physical nature of Lya emitters is not yet completely known. Moreover, multi-parameter models and their complexities necessitates a simpler model. I have developed a simple, single-parameter model to populate dark mater halos with Lya emitters. The central tenet of this model, different from many of the earlier models, is that the star-formation rate (SFR), and hence the Lya luminosity, is proportional to the mass accretion rate rather than the total halo mass. This simple model is successful in reproducing many observable including LFs, stellar masses, SFRs, and clustering of Lya emitters from z~ 3 to z~ 7. Finally, using this model, I find that the mass accretion, and hence the star-formation in> 30% of Lya emitters at z~ 3 occur through major mergers, and this fraction increases to ~ 50% at z~7.
Author : Andrei Mesinger
Release : 2015-11-28
Genre : Science
Kind : eBook
Book Rating : 57X/5 ( reviews)
Book Synopsis Understanding the Epoch of Cosmic Reionization by : Andrei Mesinger
Download or read book Understanding the Epoch of Cosmic Reionization written by Andrei Mesinger. This book was released on 2015-11-28. Available in PDF, EPUB and Kindle. Book excerpt: The dawn of the first stars, galaxies and black holes signaled a fundamental milestone in our Universe’s evolution: the Epoch of Reionization. The light from these galactic ancestors began spreading out, ionizing virtually every atom in existence. Our Universe transitioned from darkness to light, from cold to hot, from simple and boring to the wondrous cosmic zoo we see around us today. Despite its importance, observations of reionization have been few, and their interpretation has been highly controversial. Fortunately, this is rapidly changing. We will soon enter the "Big Data” era of this mysterious epoch, driven by an upcoming wave of observations with state-of-the-art telescopes as well as new sophisticated analysis tools. The aim of this volume is to summarize the current status and future outlook of the reionization field. We bring together leading experts in many sub-disciplines, highlighting the measurements that will illuminate our understanding of reionization and the cosmic dawn: (i) 21cm interferometry; (ii) high-redshift quasar spectra; (iii) high-redshift galaxy surveys; (iv) primary and secondary anisotropies of the Cosmic Microwave Background; (v) high-resolution studies of the metal content of early galaxies. We seek a roadmap to interpreting the wealth of upcoming observations. What is the best use of limited observational resources? How do we develop theoretical tools tailored for each observation? Ultimately, what will we learn about the epoch of reionization and our galactic ancestors?
Author : Charlotte Mason
Release : 2018
Genre :
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Book Synopsis Galaxies at the Epoch of Reionization by : Charlotte Mason
Download or read book Galaxies at the Epoch of Reionization written by Charlotte Mason. This book was released on 2018. Available in PDF, EPUB and Kindle. Book excerpt: The reionization of intergalactic hydrogen in the universe's first billion years was likely driven by the first stars and galaxies, so its history encodes information about their prop- erties. But the timeline of reionization is not well-measured and it is still unclear whether galaxies alone can produce the required ionizing photons. In my thesis I have focused on two ways to use galaxies at our current observational frontiers to constrain reionization and high redshift galaxy evolution. One tool is the UV luminosity function (LF), which traces the evolution of star-forming galaxies and their ionizing photons. Accurately measuring LFs and understanding their evolution are important for understanding the connections between galaxies and their dark matter halos. I developed a simple, but powerful, semi-analytic model for LF evolution assuming star formation is driven by dark matter accretion. This has proved remarkably consistent with observations, and implies the majority of star formation at high redshifts occurs in low mass galaxies. I also developed a technique to improve the accuracy of LF by accounting for gravitational lensing magnification bias. Secondly, Lyman alpha (Ly ) emission from galaxies can probe the intergalactic medium (IGM) ionization state as Ly photons are strongly attenuated by neutral hydrogen, but this requires disentangling physics on pc to Gpc scales. I developed a new forward-modeling Bayesian framework combining cosmological IGM simulations with interstellar medium models to infer the IGM neutral hydrogen fraction from observations of Ly emission. My thesis presents new measurements of the neutral fraction at z 7 and z 8, which, along with other independent constraints, provide increasing evidence for the bulk of reionization occurring at z 6 8. This is consistent with reionization being driven by ultra-faint galaxies with a low average ionizing photon escape fraction. We also show that reionization impacts Ly emission from different galaxy populations in different ways: UV bright galaxies living in overdense regions that reionize early have potentially visible Ly even in a highly neutral IGM. The upcoming James Webb Space Telescope was designed to observe galaxies at Cosmic Dawn. Throughout this thesis I have made predictions for what JWST may observe in the context of high redshift galaxy evolution.
Author :
Release : 2008
Genre :
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Book Synopsis Probing the Epoch of Reionization by :
Download or read book Probing the Epoch of Reionization written by . This book was released on 2008. Available in PDF, EPUB and Kindle. Book excerpt:
