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Saitta, Francesco. "Walks in the Lyman and Metal-line Forests." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2565.
Повний текст джерелаThe aim of this PhD thesis is the study of the properties of the Inter-Galactic Medium (IGM) through Quasi Stellar Objects (QSOs) absorption lines at redshifts z~2-4. The study of the IGM provides a unique picture of the Universe in the early phases of structure formation and is crucial to test cosmological models. Furthermore, the metal content of the IGM can be used to constrain the nature of the enrichment mechanisms at high redshifts. Two main mechanisms have been proposed predicting different distribution of metals in the IGM: a late enrichment, due to the observed galaxies at redshift ~3, and an early enrichment, due to a population of very massive first stars (the so called popIII stars), not yet observed, at higher redshift. The existing observations are not sufficient to discriminate between the two mechanisms. QSO spectra show interesting features to study the IGM: 1. The Lyman-alpha (Lya) forest : the forest of absorption lines blue-ward of the Lya emission arising in large scale neutral hydrogen density fluctuations of moderate amplitude in the warm photo-ionized IGM. Since the dynamical state of the low density IGM is governed mainly by the Hubble expansion, gravitational instabilities and photo-ionization, the involved physics is quite simple and mildly non-linear. The Lyman forest is then a fair tracer of the underlying matter density field. 2. Metal absorptions: many absorption features due to ionic transitions in chemical elements heavier than He (``metals'') are clearly present red-ward of the Lya emission. Some of them are associated with the QSO itself but the majority are tracers of intervening metals belonging to structures of different nature, from diffuse gas to galaxies. Chapter 1 of the thesis presents in detail how the physics of the IGM can be understood studying QSO absorption lines, and the classical results obtained in this field. Then the thesis focuses on the work done during the PhD, which has addressed three research areas: 1. Study of lines of sight (LOSs) to isolated QSOs (Chapter 2,3): (i) a sample of 22 high-resolution QSO spectra has been studied. Classical statistics have been applied: all the absorption features in the spectra have been fit with Voigt profiles to extract physical parameters associated with the absorbing material; quantities like the evolution in redshift of the number density of the lines and the two-point correlation function of the line distribution along the spectra have been studied and compared with measurements available in the literature; (ii) a new method to analyze the Lya forest has been implemented. Traditionally, absorption spectra are resolved in a collection of discrete absorption systems. This method instead reconstructs the underlying density field processing the lines on the basis of the physical properties of the IGM. Therefore, a continuous density field is built and the main drawbacks of the Voigt fitting approach are overcome. (iii) the new algorithm has been tested with N-body hydrodynamical simulations of the IGM; (iiii) the new algorithm has been applied to the observational data sample to study the hydrogen density field ( its evolution with redshift and its clustering properties ) and the so called proximity effect of QSO, estimating the overdensity around the object. 2. Study of lines of sight to multiple QSOs (Chapter 4,5): The thesis presents also the work done studying multiple QSO LOSs, i.e. studying the properties of the IGM not only with the spectrum of a single object, by trying to get transversal informations comparing different LOSs, close both in angular separation and in the emission redshift of the source. A sample of 15 QSO forming 21 pairs have been studied to get the transverse correlation function, using the statistics of the transmitted flux of the objects. Furthermore, we have observed a pair of close QSO during two nights (7-8 august 2007) with UVES, the high resolution spectrograph at the ESO Very Large Telescope (VLT) located at Cerro Paranal, in Chile. These two objects have been observed to study the correspondence between metal absorptions and galaxies in the field; preliminary results and the description of the work in progress are presented in detail in the thesis (Chapter 5). 3. New instrumentation (Chapter 6): Looking ahead to new possibilities of advance in this field of research, an important role will be played by the high sensitivity and medium resolution spectrograph X-shooter. It will receive first light at the ESO VLT in July 2008 and will start operating in early 2009. When in operation, its wide spectral-range observing capability will be unique at very large telescopes and extremely relevant for the study of QSO spectra. The thesis describes the Science Case "Tomography of the IGM" for the instrument, and the work done at ESO within the X-shooter project. For the operation of this instrument we have carried out laboratory measurements of calibration sources for the Near-InfraRed arm and I participated to an observational project to build a spectro-photometric flux catalogue of standard stars for the instrument.
Scopo di questa tesi di dottorato e` lo studio delle proprieta` del mezzo intergalattico (IGM) attraverso le righe in assorbimento negli spettri di quasar (QSO) osservate a redshift z~2-4. Lo studio dell'IGM e` di fondamentale importanza per verificare modelli cosmologici in quanto rende possibile l'osservazione dell'universo nelle prime fasi del processo di formazione delle strutture cosmiche. Inoltre, le tracce di elementi chimici piu` pesanti dell'He (detti ``metalli'') contenuti nell'IGM possono essere utilizzate per comprendere i meccanismi di arricchimento metallico dell'universo ad alti redshift. La distribuzione osservata di questi metalli e` al momento oggetto di un intenso dibattito all'interno della comunita` scientifica; recentemente sono stati proposti due scenari per spiegare questa distribuzione: il cosiddetto di ``late enrichment'', per cui i metalli osservati nell'IGM sarebbero dovuti principalmente alle galassie osservate a redshift ~3, e l'``early enrichement'', per cui una popolazione di stelle massicce (``popIII stars'', non ancora osservate) a redshift ancora maggiore, sarebbe responsabile della maggior parte di metalli presenti nell'IGM. Al momento le osservazioni non sono sufficienti per falsificare o confermare i meccanismi proposti.L'IGM viene studiato attraverso l'analisi di spettri di QSOs ed in particolare: 1. La foresta Lyman-alpha (Lya): l'insieme delle righe in assorbimento che si osservano a lunghezze d'onda minori rispetto all'emissione Lya negli spettri di QSOs; questi assorbimenti sono dovuti a piccole fluttuazioni su larga scala del campo di idrogeno neutro presente nell'IGM. La fisica che descrive l'IGM e` relativamente semplice. Il gas si trova in regime lineare o moderatamente non-lineare ed in equilibrio di fotoionizzazione. La sua dinamica, alla densita` media, e` dominata dall'espansione di Hubble e dall'instabilita` gravitazionale, percio` la foresta Lya risulta essere un buon candidato per la descrizione del campo di densita` presente a questi redshift. 2. Gli assorbimenti metallici: a lunghezze d'onda maggiori dell'emissione Lya sono chiaramente presenti molti assorbimenti dovuti a transizioni di ioni metallici. Alcuni di essi hanno origine in gas associato al QSO stesso, ma la maggior parte di questi assorbimenti riflette la presenza di sistemi metallici lungo la linea di vista tra l'oggetto e l'osservatore. Questi sistemi non associati sembrano essere dovuti ad una grande varieta` di strutture, da componenti di gas diffuso fino alle galassie di campo. Il capitolo 1 della presente tesi descrive nel dettaglio come si possa comprendere la fisica dell'IGM studiando i sistemi in assorbimento degli spettri di QSO, presentando i principali risultati ottenuti tradizionalmente in questo campo. Sucessivamente la tesi si concentra sul lavoro svolto durante il periodo di dottorato, ed in particolare sulle tre principali aree di ricerca affrontate: 1. Studio di linee di vista (LOSs) verso QSO singoli (Capitoli 2,3): (i) e` stato analizzato un campione di 22 spettri di QSO ad alta risoluzione, al quale sono state applicate le statistiche tradizionali: tutti gli assorbimenti Lya negli spettri sono stati fittati con profili di Voigt, al fine di ottenere parametri fisici associati ai sistemi di assorbimento; in particolare sono state studiate, e confrontate con risultati ottenuti in passato, quantita` come l'evoluzione in redshift della densita` in numero di righe e la funzione di correlazione a due punti; (ii) e` stato sviluppato un nuovo metodo per analizzare la foresta Lya. A differenza dell'approccio tradizionale, dove da uno spettro di QSO si ottiene semplicemente un insieme discreto di assorbitori, questo metodo ricostruisce il campo di densita` di idrogeno responsabile degli assorbimenti partendo da assunzioni sulla fisica dell'IGM. Il risultato e` un campo di densita` continuo la cui analisi permette di risolvere alcuni problemi introdotti invece dalla classica analisi di profili di Voigt. (iii) il nuovo algoritmo e` stato testato con simulazioni idrodinamiche ``N-body'' dell'IGM; (iiii) il nuovo algoritmo e` stato applicato ai dati osservativi citati in precedenza per studiare il campo di densita` di idrogeno (la sua evoluzione con il redshift e la funzione di correlazione a due punti) ed il cosiddetto ``effetto di prossimita`'', portando ad una stima della sovradensita` del campo nella regione dove si trova un QSO. 2. Studio di linee di vista verso sistemi di QSOs (Capitoli 4,5): la tesi presenta anche uno studio di linee di vista multiple; il confronto di diverse linee di vista, vicine in separazione angolare e in redshift di emissione, permette di avere informazioni non solo sulle regioni di universo tracciate dalle linee di vista, ma anche sulle regioni tra le linee di vista stesse. A questo riguardo e` stata studiata la ``funzione di correlazione trasversale'' ottenuta dall'analisi del flusso trasmesso da un campione di 15 QSO che formano 21 coppie. Per lo studio di linee di vista multiple e` stata osservata una coppia di QSO per due notti (7-8 agosto 2007); le osservazioni sono state fatte con lo spettrografo ad alta risoluzione UVES, al ``Very Large Telescope'' (VLT), situato al Cerro Paranal, in Cile. Questi oggetti sono stati osservati per studiare le corrispondenze tra assorbimenti metallici e galassie di campo. Il lavoro fatto ed i risultati preliminari ottenuti fino ad ora sono presentati nel capitolo 5. 3. Nuova strumentazione (Capitolo 6): Un ruolo importante per il progresso della scienza dell'IGM verra` svolto dal nuovo spettrografo a media risoluzione ed alta` sensibilita`, X-shooter. X-shooter ricevera` la prima luce all'osservatorio ESO VLT in luglio 2008 per poter essere in pieno funzionamento agli inizi del 2009. L'ampio intervallo spettrale coperto e le caratteristiche di questo strumento sono particolarmente vantaggiose per lo studio di spettri di QSOs. Nella tesi viene descritto il caso scientifico ``Tomography of the IGM'' per lo strumento, ed il lavoro svolto all'ESO nel contesto del progetto X-shooter. Questo lavoro include le misure di laboratorio di sorgenti di calibrazione per il braccio nel vicino infrarosso dello strumento e la partecipazione al progetto osservativo per la costruzione di un catalogo spettro-fotometrico di stelle standard per la calibrazione assoluta in flusso degli oggetti che si osserveranno con X-shooter.
XX Ciclo
1980
Leonard, Anthony Patrick Burford. "Simulating the Lyman-#alpha# forest." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300815.
Повний текст джерелаLiske, Jochen Physics Faculty of Science UNSW. "Cosmology with the Lyman alpha forest." Awarded by:University of New South Wales. School of Physics, 2000. http://handle.unsw.edu.au/1959.4/17870.
Повний текст джерелаParnell, Helen Clare. "Properties of the Lyman alpha forest." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316772.
Повний текст джерелаWilliger, Gerard Michael. "Evolutionary paths in the Lyman alpha forest." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385499.
Повний текст джерелаBechtold, J., and S. A. Shectman. "Statistical Properties of the Lyman-alpha Forest." Steward Observatory, The University of Arizona (Tucson, Arizona), 1988. http://hdl.handle.net/10150/623892.
Повний текст джерелаTie, Suk Sien. "Lyman-alpha forest cosmology with the Dark Energy Spectroscopic Instrument (DESI)." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1594035656891479.
Повний текст джерелаNasir, Fahad. "Probing the IGM with the Lyman-alpha forest through cosmic time." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49347/.
Повний текст джерелаCocke, W. J., and W. G. Tifft. "Redshift Quantization in the Lyman-alpha Forest and the Measurement of qo." Steward Observatory, The University of Arizona (Tucson, Arizona), 1988. http://hdl.handle.net/10150/623916.
Повний текст джерелаMarble, Andrew R. "QSO Pairs and the Lyman-alpha Forest: Observations, Simulations, and Cosmological Implications." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/193945.
Повний текст джерелаAriño, i. Prats Andreu. "Physics of the Intergalactic Medium: a Study of the Power Spectrum ot the Lyman Alpha Forest and the Metal Content of Damped Lyman Alpha Systems." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/289625.
Повний текст джерелаThe Intergalactic Medium (IGM), by means the Lyα absorption in quasar spectra ( this is called Lyα forest), is a unique tool allowing the study of the large scales of the universe, which in this way constrains several cosmological, the growth factor of the structure. Moreover the IGM also plays primordial role in galaxy formation. Understanding the physics of the IGM and the way non-linear processes affect the observed Lyα forest, hydrodynamical simulations are necessary because the non linear evolution of the physics cannot be treated in any analytic framework. At the same time, a large number of observations, which have been obtained from the Barionic Oscilation Spectrographic survey (BOSS) to be used in thesis allow studding in unprecedented large number of Lyα forest from quasar spectra, allowing to achieve major breakthroughs. In the 2nd chapter of this thesis we describe the methodology that we developed to extract the power spectrum from the transmission flux of the Hydrodynamical simulations. Using a set of simulations provided by various collaborators we study the effects of various simulation characteristics, such as resolution, box size, particles, and cell division, to see how they might affect the extracted power spectrum. Then we proceed to develop a model to fit the power spectrum of each of the simulations and in this way see the effects of different simulation and physical properties on the predictions from the power spectrum. Once the model fit has been obtained, the non linear power spectrum of the transmission can be related on the matter power spectrum, which on the form of its biased relation with the matter power spectrum contains the cosmological information. This relation is measured by the bias and redshift distortions that can be directly measured from simulations, making predictions for these values that could be later tested with the observations. In the 3rd chapter we use the data from the large catalogue of Damped Lyα systems (DLAs) provided by BOSS. These DLAs, broad regions of completely absorbed flux in the spectra of about 10% of the high redshift objects, the quasars. The DLAs are a large repository of neutral hydrogen, that is why they absorb all the flux that corresponds to their redshift. Since there is so much Neutral Hydrogen the absorption is damped, meaning that wavelength close to the one of the DLA also get absorbed, forming characteristic Lorenz wings that are sensitive to the column density of Hydrogen of the DLA. DLAs are interesting objects that are expected to be very relevant for galaxy formation, and also because they trace the large structure, therefore also being relevant for cosmology. They are, similarly to IGM of which they form part, a bridge between the large cosmological framework and the galaxies that populate the universe. The BOSS survey has allowed us for the first time have a set of thousands of DLAs. Given this amount of data and the interest of the DLAs, we developed a new method and a new parameterization to study the DLAs in the framework of large surveys such as BOSS. First we constructed a method to measure the equivalent width of several metal absorption lines associated with each DLA, even if individually they are not detected because they can not be observed due to the noise and resolution of the spectrum. The equivalent width are combined in a newly defined parameter called Metal Strength, which is a an optimal combination of the equivalent width of the metals measured for a DLA. This classification can then have many applications to measure the mean stack, mean bias and mean redshift evolution with respect this new parameter. The Metal Strength is therefore used to analyse the evolution and characteristics of the various populations of DLAs.
Renard, Guiral Pablo. "Lyman-alpha Intensity Mapping forecast with the PAU Survey." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/671939.
Повний текст джерелаEn los próximos años, la cantidad de datos observacionales disponibles para la astrofísica en conjunto, y particularmente la cosmología, se incrementará en órdenes de magnitud. Para aprovechar totalmente estas próximas observaciones, se han de desarrollar nuevos métodos estadísticos para extraer resultados científicos. Uno de estos nuevos métodos es el Intensity Mapping, que consiste en trazar una línea de emisión en coordenadas angulares y redshift, sin considerar objetos resueltos. Esta tesis está enfocada en la simulación y evaluación del Intensity Mapping con la línea Lyman-alpha haciendo la correlación cruzada de dos tipos de surveys ópticas: la survey fotométrica de banda estrecha PAUS y las surveys espectroscópicas eBOSS y DESI. La primera debe contener emisión Lyman-alpha extensa proveniente del medio intergaláctico del fondo de las imágenes, mientras que las segundas contienen el bosque Lyman-alpha (el conjunto de líneas de absorción generadas por el medio intergaláctico) en los espectros de sus quásares. Al hacer la correlación cruzada de ambas, deberíamos obtener una señal de la emisión de Lyman-alpha difusa, a pesar de los objetos no correlacionados y el ruido en las imágenes de PAUS. Para simular esta correlación cruzada, se ha usado una simulación hidrodinámica especialmente diseñada para el estudio de Lyman-alpha en el medio intergaláctico para simular tanto la emisión como absorción Lyman-alpha, mientras que los objetos no correlacionados de las imágenes de PAUS han sido modelados usando un catálogo simulado profundo al que se le han ajustado plantillas de emisión espectrales a sus objetos. El ruido instrumental y atmosférico se ha añadido a las imágenes de PAUS simuladas midiendo directamente el ruido de conjuntos de imágenes apiladas y enmascaradas, y se ha introducido en la simulación como una distribución gaussiana. Además, se ha desarrollado, optimizado y validado un código de correlación cruzada desde cero dentro del marco de esta tesis, para calcular las correlaciones. Los resultados se presentan de forma probabilística: para los diferentes casos (PAUS-eBOSS, PAUS-DESI y dos extensiones hipotéticas de PAUS) se han calculado 1.000 correlaciones cruzadas con diferentes realizaciones del ruido instrumental y atmosférico, así como las posiciones de los quásares. Con la aproximación optimista del ruido instrumental no correlacionado (lo que requeriría más trabajo reduciendo los datos), incluso la extensión más larga de PAUS considerada tiene tan solo una probabilidad de detección del 15%; si empleamos el ruido correlacionado que se observa en las imágenes, todas las probabilidades pasan a ser despreciables. A pesar de estos resultados negativos, podemos extraer algunas conclusiones valiosas. Los diferentes tipos de de funciones de correlación de dos puntos (monopolo, paralela y perpendicular a la línea de visión) muestran comportamientos complementarios: el monopolo y la paralela tienen un mejor rendimiento a escalas más grandes, mientras que la perpendicular sondea mejor las escalas menores de 10 Mpc/h. Además, el suavizado en redshift de la señal Lyman-alpha debido a los filtros fotométricos se ha implementado de forma adecuada en el modelo teórico, e incluso puede ser utilizada para predecir las escalas con mejor ratio entre señal y ruido para cada función de correlación. Por tanto, estos descubrimientos indican que esta metodología puede ser más adecuada para las surveys de banda ancha; concluimos la tesis dando algunas directrices básicas de cómo este estudio se puede replicar para este tipo de datos.
In the upcoming years, the amount of observational data available for astrophysics as a whole, and particularly cosmology, is expected to increase by ordersof magnitude due to the new observational programs and technological advancements. To fully capitalise on these upcoming observations, new statistical methodsto draw scientific results have to be developed and applied. Intensity Mapping isone of such new methods, which consists on the tracing of a sharp spectral feature(e.g., a emission line) in angular coordinates and redshift, without considering resolved objects.This thesis is focused on the simulation and evaluation of Intensity Mappingwith the Lyα ; line by cross-correlating two kinds of optical surveys: the narrowband photometric survey PAUS, and the spectroscopic surveys eBOSS and DESI.The former should contain extended Lyα ; emission from the intergalactic medium inthe background of the images, while the latter contains the Lyα ; forest (i.e., the setof absorption lines generated by the intergalactic medium) in their quasar spectra.Cross-correlating both then should yield a signal of the diffuse Lyα ; emission, despitethe foregrounds and noise in PAUS images.In order to simulate this, a hydrodynamic simulation specifically designed forthe study of Lyα ; in the intergalactic medium has been used to simulate both Lyα ;emission and absorption, while the foregrounds in PAUS images have been modeled using a deep lightcone mock catalogue and fitting spectral energy distributions to its objects. Instrumental/atmospheric noise has been added to the simulated PAUS images by directly measuring the noise from sets of masked and stackedimages, and introducing it on the simulation as a Gaussian distribution. Besides, across-correlation code in Python has been developed from scratch, optimised andvalidated in the framework of the thesis to compute the cross-correlations.The results are presented in a probabilistic manner: for different cases (PAUSeBOSS, PAUS-DESI and two hypothetical PAUS extensions with DESI) 1,000 crosscorrelations are computed with different realisations of the instrumental/atmosphericnoise of PAUS images, as well as quasar positions. With the optimistic approximation of uncorrelated instrumental noise (which would require further work in datareduction), even the largest PAUS extension considered only yields a probability of detection of - 15%; using the actual correlated noise all the probabilities becomenegligible.In spite of these negative results, some valuable conclusions are extracted. Thedifferent kinds of two-point correlation functions (monopole, parallel and perpendicular to the line of sight) show complementary behaviours: monopole and parallel perform better at larger scales, while perpendicular samples better the scalessmaller than 10 Mpc/h. Besides, the redshift smoothing in the Lyα ; signal due to the photometric filters has been properly implemented in the theoretical model, andcan even be used to predict the scales with better SNR for each correlation function.Therefore, these findings indicate that this methodology may be more suitable forbroad-band surveys; we conclude the thesis giving some basic guidelines on howthis study could be replicated for broad-band data.
Universitat Autònoma de Barcelona. Programa de Doctorat en Física
Calverley, Alexander Peter. "Probing the Intergalactic Medium with high-redshift quasars." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/241943.
Повний текст джерелаChabanier, Solène. "Neutrinos and dark matter cosmology with the Lyman-α forest : the interplay between large-scale evolution and small-scale baryonic physics". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP034.
Повний текст джерелаEven if the standard cosmological LCDM model provides a remarkably successful framework to explain many independent observations, it still faces many challenges. In particular, the masses of neutrinos are still unknown and significantly alter structure formation because of their free-streaming that suppresses density fluctuations below a typical length scale inversely proportional to their rest mass. In addition, the cold dark matter (CDM) scenario is in tension with observations on scales smaller than the Mpc. In this thesis work, I use the power spectrum of the transmitted flux in the Lyman-α forest of distant quasar spectra to constrain the sum of neutrino masses, Σ mν, and determine the plausibility of a warm dark matter model, which is conveniently consistent with cold dark matter predictions on large scales while circumventing its issues at small scales because of its non-negligible velocity dispersion. First I measure the 1D power spectrum of the Lyα forest of 43,751 high quality quasar spectra between 2 ≤ z ≤ 4.6 from the BOSS and eBOSS programs of the SDSS spectroscopic survey. To obtain robust results given the unprecedented statistical power of the data I perform a careful investigation of observational systematic sources and their sources. Modeling the Lyα flux power spectrum requires to run hydrodynamical cosmological simulations because it arises from the complex interplay between large-scale structure evolution and small-scale baryonic physics. Indeed, astrophysical processes such as star formation or AGN feedback inject energy in the ambient medium and strongly impact the thermal state and gas distribution in the intergalactic medium. Including such processes in hydrodynamical simulations requires to rely on arbitrary parameters calibrated on astrophysical observations leading to discrepancies between different state-of-the-art simulations. In order to improve theoretical predictions of the Lyα forest, I constrain the impact of AGN feedback using a series of 8 hydro-cosmological simulations covering the whole plausible range of feedback models. I provide upper and lower limit for this signature for 2 ≤ z ≤ 4.25 and also show that ignoring this effect leads to 2σ shift on n_s and 1σ shift on σ_8. Finally, I combine the Lyα flux power spectrum measurements with CMB data, BAO data and theoretical predictions from hydrodynamical simulations to enhance the previously established constraints on the sum of neutrino masses from Σ mν < 0.12 eV to the most stringent constraints to date Σ mν < 0.09 eV in the most extreme case with 95% confidence, which tends to favor the normal hierarchy neutrino mass scenario. Combining eBOSS with XQ-100 Lyα data the mass m_X of hypothetical thermal relics is constrained to m_X > 5.3 keV at the 95% confidence level in the case of a pure warm dark matter scenario, which translates into mν_s > 34 kev for non-resonantly produced sterile neutrinos. Also, a mild-tension is found on n_s between eBOSS Lyα and CMB data, which translates into a preference for a non-zero running of n_s at the level of about 3σ
Etourneau, Thomas. "Les forêts Lyman alpha du relevé eBOSS : comprendre les fonctions de corrélation et les systématiques." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP029.
Повний текст джерелаThis PhD thesis is part of eBOSS and DESI projects. These projects, among other tracers, use the Lyman-α (Lyα) absorption to probe the matter distribution in the universe and measure thebaryon acoustic oscillations (BAO) scale. The measurement of the BAO scale to the sound horizon ratio allows to constrain the universe expansion and so the ΛCDM model, the standard model of cosmology. This thesis presents the development of mock data sets used in order to check the BAO analyses carried out by the Lyα group within the eBOSS and DESI collaborations. These mocks make use of gaussian random fields (GRF). GRF allow to generate a density field δ. From this density field, quasar (QSO) positions are drawn. From each quasar, a line of sight is constructed. Then, the density field δ is interpolated along each line of sight. Finally, the fluctuating Gunn Peterson approximation (FGPA) is used to convert the interpolated density into the optical depth τ , and then into the Lyα absorption. Thanks to a program developed by the DESI community, a continuum is added to each Lyα forest in order to produce quasar synthetic spectra. The mocks presented in the manuscript provide a survey of quasars whose Lyα forests in the quasar spectra have the correct Lyα×Lyα auto-correlation, Lyα×QSO cross-correlation, as well as the correct QSO×QSO and HCD×HCD (High Column Density systems) auto-correlation functions. The study of these mocks shows that the BAO analysis run on the whole Lyα eBOSS data set produces a non-biaised measurement of the BAO parameters αk et α⊥. In addition, the analysis of the model used to fit the correlation functions shows that the shape of the Lyα×Lyα auto-correlation, which is linked to the bias bLyα and redshift space distorsions (RSD) parameter βLyα, are understood up to 80 %. The systematics affecting the measurement of the Lyα parameters (bLyα et βLyα) come from two different effects. The first one originates from thedistortion matrix which does not capture all the distortions produced by the quasar continuum fittingprocedure. The second one is linked to the HCD modelling. The modelling of these strong absorbers is not perfect and affects the measurement of the Lyα parameters, especially the RSD parameter βLyα. Thus, the analysis of these mocks allows to validate the systematic control of the BAO analyses done with the Lyα. However, a better understanding of the measurement of the Lyα parameters is required in order to consider using the Lyα, which means combining the Lyα×Lyα autocorrelation and Lyα×QSO cross-correlation, to do a RSD analysis
Fu, Nicole Christina. "Physical Properties of Massive, Star-Forming Galaxies When the Universe Was Only Two Billion Years Old." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19956.
Повний текст джерелаSainte, Agathe Victoria de. "Mesure de la position du pic d'oscillations acoustiques baryoniques dans les forêts Lyα et Lyβ des spectres des quasars du relevé eBOSS-SDSS IV". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS373.
Повний текст джерелаThe propagation of the baryonic acoustic oscillations has been unprinted in the matter distribution in the Universe as a probability excess for two objets to be separated by the acoustic scale. Measuring the acoustic scale in the matter 2 point correlation function at redshift z, along and transversally to the line-of-sight, gives access to the DH(z)/rd et DM(z)/rd ratios, with DH the Hubble distance, DM the comoving angular distance and rd the acoustic horizon. We are able to trace the matter in the Universe by using the Lyman-alpha absorptions which shape the spectra of the high redshift quasars. Since each spectrum contain hundreds of absorption, this allow us to measure the acoustic scale even if the observed quasar density is low. In this thesis, I describe the analysis of about 200,000 spectra from the eBOSS-SDSS IV survey which conducts to the measurements DH(2.34)/rd = 8.86 0.29 et DM(2.34)/rd = 37.41 1.86. By combining these results with measurements of the acoustic scale at other redshifts, I obtain the strongest current constraints at low redshift on the Omega-m and Omega-Lambda Lambda-CDM parameters
Hee, Sonke. "Computational Bayesian techniques applied to cosmology." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273346.
Повний текст джерелаLiske, Jochen. "Cosmology with the Lyman alpha forest /." 2000. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20011205.030418/index.html.
Повний текст джерелаKuo, Jui-Lin, and 郭瑞麟. "Cosmological Simulation of Fuzzy Dark Matter with Uncertainty Discussion and Comparison with Lyman-Alpha Forest." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/vu9d46.
Повний текст джерела國立清華大學
物理學系
106
Fuzzy dark matter is one of the dark matter candidates, which can not only have the same large-scale success of cold dark matter but also alleviates the ”small scale crisis” of it when the fuzzy dark matter mass is smaller than 10^{−22} eV. With recent Lyman-alpha forest data from BOSS and XQ-100, some studies suggested that the lower mass limit on the fuzzy dark matter particles is lifted up to 10^{−21} eV. However, such a limit was obtained by cold dark matter simulations with the fuzzy dark matter initial condition and the quantum pressure of fuzzy dark matter was not taken into account which could have generated non-trivial effects on small scales. After checking the validity of our methodology using one-dimensional simulation, we investigate the effects of quantum pressure in cosmological simulations systematically, and find that quantum pressure leads to further suppression on the matter power spectrum on small scales, as well as the halo mass function in the low mass end. Furthermore, we estimate the one-dimensional flux power spectrum of Lyman-alpha forest, and compare it with the data from BOSS and XQ-100. We carefully estimate the uncertainty in the calculation of one-dimensional flux power spectrum due to the temperature of hydrogen gas. We conclude that if one properly takes into account the effect of quantum pressure and the temperature of the hydrogen gas, one cannot exclude the fuzzy dark matter of mass smaller than 10^{−22} eV, which is the interesting mass range for solving the small scale crisis, at statistically significant levels.