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Quasar Continuum Fitting And Silicon Absorption On The Low Redshift Intergalactic Medium
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Book Synopsis Quasar Continuum Fitting and Silicon Absorption on the Low Redshift Intergalactic Medium by : Adam Andrew Miller
Download or read book Quasar Continuum Fitting and Silicon Absorption on the Low Redshift Intergalactic Medium written by Adam Andrew Miller and published by . This book was released on 2006 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present results on the evolution of Ly[alpha] absorption at low redshift, and the first systematic search for Si II absorption systems in the low redshift IGM. Our sample consists of 832 Ly[alpha] absorbers from 328 spectra of 204 QSOs taken from the Hubble Space Telescope archive. We develop a new, reproducible method of quasar continuum fitting, designed to quickly identify absorption lines and measure the relative line strength (a proxy for equivalent width). Our method, which fails to identify the weakest lines, does manage to detect the strong features in a given spectrum and provides enough information to identify metal absorption line systems. We confirm the results of previous studies of Ly[alpha] evolution at low redshift and find the number density of absorbers can be described by a power law in (l+z) that is much flatter than that found for Lya evolution at high redshift. Specifically, we measure a power law index of [gamma] = 0.57 ± 0.16 for lines with a rest relative line strength greater than 0.10 [Angstroms]. We also identify the presence of 14 Si II systems at z [approx] 1. The number of Si ii 1193 and 1260 [Angstroms] systems per unit redshift path length at a mean redshift of z = 0.9 is N(z)= 1.6 ± 0.6. This density is similar to that found for C Ii, Mg ii, and O vi absorbers.
Book Synopsis Structure and Evolution of the Intergalactic Medium from QSO Absorption Line Systems by : Patrick Petitjean
Download or read book Structure and Evolution of the Intergalactic Medium from QSO Absorption Line Systems written by Patrick Petitjean and published by Atlantica Séguier Frontières. This book was released on 1997 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Cosmology from the High Redshift Intergalactic Medium by : John Mark OʹMeara
Download or read book Cosmology from the High Redshift Intergalactic Medium written by John Mark OʹMeara and published by . This book was released on 2004 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Quasar Proximity Effect and the Intergalactic Medium at Low Redshift by : Alice Eltvedt
Download or read book The Quasar Proximity Effect and the Intergalactic Medium at Low Redshift written by Alice Eltvedt and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Probing the Intergalactic Medium with High-redshift Quasars by : Alexander Peter Calverley
Download or read book Probing the Intergalactic Medium with High-redshift Quasars written by Alexander Peter Calverley and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Clues about the timing of reionization and the nature of the ionizing sources responsible are imprinted in the ionization and thermal state of the IGM. In this thesis, I use high-resolution quasar spectra in conjunction with state-of-the-art hydrodynamical simulations to probe the IGM at high redshift, focusing on the ionization and thermal state of the gas. After reionization, the ionization state of the IGM is set by the intensity of the ultraviolet background(UVB), quantified by the hydrogen photoionization rate,?_bkg. At high redshifts this has been estimated by measuring the mean flux in the Ly? forest, and scaling?_bkg in simulations such that the simulated mean flux matches the observed value. In Chapter 3 I investigate whether the precision of these estimates can be improved by using the entire flux probability distribution function (PDF) instead of only the mean flux. Although I find it cannot improve the precision directly, the flux PDF can potentially be used to constrain other sources of error in observational estimates of?_bkg, and somay increase the precision indirectly. The ionizing output of a quasar will locally dominate over the UVB, and this leads to enhanced transmission bluewards of the quasar Ly? line, known as the proximity effect. In Chapter 4 I present the first measurements of?_bkg at z> 5 from the proximity effect. The UVB intensity declines smoothly with redshift over 4.6 z 6.4, implying a smooth evolution in the mean free path of ionizing photons. This suggests that reionization ends at z 6.4. There is a drop in?_bkg by roughly a factor of five, which corresponds to a drop in the ionizing emissivity by about a factor of two. Such a redshift evolution in the emissivity cannot continue to much higher redshift without reionization failing to complete, which suggests that reionization cannot have ended much higher than z = 6.4. Estimates of?_bkg from the proximity effect and the mean flux are generally discrepant at z? 2?4, with those from the proximity effect systematically higher. This is generally attributed to effects of the quasar environment. I investigate the significance of several environmental biases on proximityeffect measurements at z? 5?6 in Chapter 5. The biases are found to be small, and so the proximity effect is expected to give relatively unbiased estimates of?_bkg at z 5, in contrast to lower redshifts. Photoionization heats the gas in the IGM, and so the thermal history of the IGM provides important constraints on reionization. The thermal state of the IGM is reflected in the level of small-scalestructure in the Ly? forest. In Chapter 6 I quantify the small-scale structure using two independent statistics, the curvature and the peakiness, and convert these into a temperature by comparing with simulations. These are the first measurements of the temperature in the general IGM at z> 5. Bothstatistics show an increase in the temperature by a factor of roughly two from z = 4.4 to 5.6. This rise is sensitive, however, to any smoothing of the gas density distribution due to the thermal historyspanning reionization. I find that this should only be a small effect, as otherwise the corrected temperatures at z? 4?5 are implausibly low. The temperature evolution therefore suggests a late reionization. The temperatures at z? 4.8 are well fit by an adiabatic cooling curve, for which reasonablepeak temperatures at the end of reionization are reached at 6? z? 7. The temperatures atz? 4?5 are consistent with reionization being carried out by Pop II stars. In conclusion, the ionization and thermal state of the IGM at z? 5?6 suggest a late hydrogen reionization, driven by star-forming galaxies and ending around 6.5? z? 7. This is consistent with other recent lines of observational evidence, and supports theoretical models that infer a late reionization from the observed star formation rate history.
Book Synopsis Physics of the Interstellar and Intergalactic Medium by : Bruce T. Draine
Download or read book Physics of the Interstellar and Intergalactic Medium written by Bruce T. Draine and published by Princeton University Press. This book was released on 2010-12-20 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a comprehensive and richly illustrated textbook on the astrophysics of the interstellar and intergalactic medium--the gas and dust, as well as the electromagnetic radiation, cosmic rays, and magnetic and gravitational fields, present between the stars in a galaxy and also between galaxies themselves. Topics include radiative processes across the electromagnetic spectrum; radiative transfer; ionization; heating and cooling; astrochemistry; interstellar dust; fluid dynamics, including ionization fronts and shock waves; cosmic rays; distribution and evolution of the interstellar medium; and star formation. While it is assumed that the reader has a background in undergraduate-level physics, including some prior exposure to atomic and molecular physics, statistical mechanics, and electromagnetism, the first six chapters of the book include a review of the basic physics that is used in later chapters. This graduate-level textbook includes references for further reading, and serves as an invaluable resource for working astrophysicists. Essential textbook on the physics of the interstellar and intergalactic medium Based on a course taught by the author for more than twenty years at Princeton University Covers radiative processes, fluid dynamics, cosmic rays, astrochemistry, interstellar dust, and more Discusses the physical state and distribution of the ionized, atomic, and molecular phases of the interstellar medium Reviews diagnostics using emission and absorption lines Features color illustrations and detailed reference materials in appendices Instructor's manual with problems and solutions (available only to teachers)
Book Synopsis Quasar Spectroscopy in Ultraviolet and X-ray- Probing the Intergalactic Medium Using Helium and Oxygen by : Donglai Gong
Download or read book Quasar Spectroscopy in Ultraviolet and X-ray- Probing the Intergalactic Medium Using Helium and Oxygen written by Donglai Gong and published by . This book was released on 2004 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: We employ ultraviolet (UV) and X-ray quasar spectroscopy to study the physical state of the Intergalactic Medium (IGM). First, we quantify the possibility of measuring the temperature of moderately over-dense regions of the IGM at high redshift (z [approx.] 2) using the strongest resonant absorption lines of neutral hydrogen ([lambda]HI = 1215.67 A[ngstroms]) and neutral helium ([lambda]HeI = 584.33 A[ngstroms]). We calculate the fraction of neutral helium in the IGM at z [approx.] 2 by solving a set of photoionization equilibrium equations. Using known distributions of the redshift, column density and Dopper [beta]-parameter of Lyman-[alpha] ac lines, we perform Monte Carlo simulation to create a line list, from which we calculate the number of observable HeI lines. We expect that 4.5% of the HI lines have observable HeI counterparts. Future ultraviolet (UV) telescope with wavelength coverage from 1400 A[ngstroms] to 2400 A[ngstroms] should be able to observe [approx.] 16 HelI lines per line of sight observation. Second, we analyze a combined 171 ksec. spectroscopic observation of the low redshift quasar 3C 273 by the Chandra X-ray Observatory. We search for the high ionization state lines of OVII and OVIII at redshifts of known intervening OVI absorbers. Detection of associated OVII or OVIII absorptions in the X-ray would suggest the existence of a warm hot component of the Intergalactic Medium at temperature T [approx.] 106 - 107 K. We observe an unresolved OVII line at z [approx.]0 with a maximum Doppler [beta] parameter of 190 km/s. We do not see any associated OVII absorption for a z [approx.] 0.12 OVI absorber at the -3.5[sigma] level. We provide most stringent to date (Chandra resolution limited) upper limit on the temperature of the z [approx.] 0.12 absorber and discuss the possibilities of photoionization and collisional ionization.
Book Synopsis Lyman-alpha as an Astrophysical and Cosmological Tool by : Mark Dijkstra
Download or read book Lyman-alpha as an Astrophysical and Cosmological Tool written by Mark Dijkstra and published by Springer Nature. This book was released on 2019-11-12 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydrogen Lyman-alpha line is of utmost importance to many fields of astrophysics. This UV line being conveniently redshifted with distance to the visible and even near infrared wavelength ranges, it is observable from the ground, and provides the main observational window on the formation and evolution of high redshift galaxies. Absorbing systems that would otherwise go unnoticed are revealed through the Lyman-alpha forest, Lyman-limit, and damped Lyman-alpha systems, tracing the distribution of baryonic matter on large scales, and its chemical enrichment. We are living an exciting epoch with the advent of new instruments and facilities, on board of satellites and on the ground. Wide field and very sensitive integral field spectrographs are becoming available on the ground, such as MUSE at the ESO VLT. The giant E-ELT and TMT telescopes will foster a quantum leap in sensitivity and both spatial and spectroscopic resolution, to the point of being able, perhaps, to measure directly the acceleration of the Hubble flow. In space, the JWST will open new possibilities to study the Lyman-alpha emission of primordial galaxies in the near infrared. As long as the Hubble Space Telescope will remain available, the UV-restframe properties of nearby galaxies will be accessible to our knowledge. Therefore, this Saas-Fee course appears very timely and should meet the interest of many young researchers.
Author :Space Telescope Science Institute (U.S.). Symposium Publisher :Cambridge University Press ISBN 13 :9780521630979 Total Pages :328 pages Book Rating :4.6/5 (39 download)
Book Synopsis The Hubble Deep Field by : Space Telescope Science Institute (U.S.). Symposium
Download or read book The Hubble Deep Field written by Space Telescope Science Institute (U.S.). Symposium and published by Cambridge University Press. This book was released on 1998-10-13 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Hubble Deep Field (HDF) is the deepest optical image of the Universe ever obtained. It is the result of a 150-orbit observing programme with the Hubble Space Telescope. It provides a unique resource for researchers studying the formation and evolution of stars and galaxies. This timely volume provides the first comprehensive overview of the HDF and its scientific impact on our understanding in cosmology. It presents articles by a host of world experts who gathered together at an international conference at the Space Telescope Science Institute. The contributions combine observations of the HDF at a variety of wavelengths with the latest theoretical progress in our understanding of the cosmic history of star and galaxy formation. The HDF is set to revolutionize our understanding in cosmology. This book therefore provides an indispensable reference for all graduate students and researchers in observational or theoretical cosmology.
Book Synopsis Probing the Connection Between the Intergalactic Medium and Galaxies with Quasar Absorption-line Spectroscopy by : Charles William Finn
Download or read book Probing the Connection Between the Intergalactic Medium and Galaxies with Quasar Absorption-line Spectroscopy written by Charles William Finn and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Active Galactic Nuclei by : Professor R. D. Blandford
Download or read book Active Galactic Nuclei written by Professor R. D. Blandford and published by Springer. This book was released on 2013-12-14 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Physics of the Interstellar Medium and Intergalactic Medium by : Andrea Ferrara
Download or read book The Physics of the Interstellar Medium and Intergalactic Medium written by Andrea Ferrara and published by . This book was released on 1995 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis High-Velocity Clouds by : Hugo van Woerden
Download or read book High-Velocity Clouds written by Hugo van Woerden and published by Springer Science & Business Media. This book was released on 2004-09-29 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: On the occasion of the retirement of Ulrich Schwarz, a symposium was held in Groningen in May of 1996, celebrating his contributions to the study of the int- stellar medium, including his work on the high-velocity clouds. The coming together of many specialists in the latter ?eld prompted the idea of compiling a book c- taining their contributions, and summarizing the status of our understanding of the high-velocity cloud phenomenon. This seemed especially worthwhile at the time, since many exciting developments were taking place. After the discovery of some H i clouds with high velocities, about 40 years ago, the subject had been dominated by 21-cm observations of H i emission. Starting in the mid-1980s much progress was being made because of the availability of new instruments, such as large ground-based optical telescopes and UV observatories in space. The connections between the work on high-velocity clouds and other studies of the properties of the (hot) interstellar medium also became clearer.
Book Synopsis The Physics and Evolution of Active Galactic Nuclei by : Hagai Netzer
Download or read book The Physics and Evolution of Active Galactic Nuclei written by Hagai Netzer and published by Cambridge University Press. This book was released on 2013-09-16 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.
Download or read book Physics Briefs written by and published by . This book was released on 1993 with total page 1334 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quasar Astronomy by : Daniel W. Weedman
Download or read book Quasar Astronomy written by Daniel W. Weedman and published by Cambridge University Press. This book was released on 1988-04-14 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: A current account of quasar astronomy that not only summarizes existing results from various techniques but refers to the potentialities of new instruments. All aspects of quasar spectroscopy are discussed and techniques for analyzing quasar data are summarized.
Book Synopsis Cosmic Evolution by : Eric J. Chaisson
Download or read book Cosmic Evolution written by Eric J. Chaisson and published by Harvard University Press. This book was released on 2001-02-16 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chaisson addresses some of the most basic issues we can contemplate: the origin of matter and the origin of life, and the ways matter, life, and radiation interact and change with time. He designs for us an expansive yet intricate model depicting the origin and evolution of all material structures.
