This thesis explores topics related to the formation and development of the large-scale structure in the Universe, with the focus being to compute properties of the evolved non-linear density field in an approximate way. The first three chapters form an introduction: Chapter 1 contains the theoretical basis of modern cosmology, Chapter 2 discusses the role of N-body simulations in the study of structure formation and Chapter 3 considers the phenomenological halo model. In Chapter 4 a novel method of computing the matter power spectrum is developed. This method uses the halo model directly to make accurate predictions for the matter spectrum. This is achieved by fitting parameters of the model to spectra from accurate simulations. The final predictions are good to 5% up to k = 10 hMpc-1 across a range of cosmological models at z = 0, however accuracy degrades at higher redshift and at quasi-linear scales. Chapter 5 is dedicated to a new method of rescaling a halo catalogue that has previously been generated from a simulation of a specific cosmological model to a different model; a gross rescaling of the simulation box size and redshift label takes place, then individual halo positions are modified in accord with the large scale displacement field and their internal structure is altered. The final power spectrum of haloes can be matched at the 5% level up to k = 1 hMpc-1, as can the spectrum of particles within haloes reconstituted directly from the rescaled catalogues. Chapter 6 applies the methods of the previous two chapters to modified gravity models. This is done in as general a way possible but tests are restricted to f(R) type models, which have a scale-dependent linear growth rate as well as having 'chameleon screening' - by which modifications to gravity are screened within some haloes. Taking these effects into account leads to predictions of the matter spectrum at the 5% level and rescaled halo distributions that are accurate to 5% in both real and redshift space. For the spectrum of halo particles it is demonstrated that accurate results may be obtained by taking the enhanced gravity in some haloes into account.

In this thesis, I explore both obscured and unobscured star formation over a large fraction of cosmic time. I use the HAWK-I Y -band science verification data over GOODS-South, in conjunction with optical and infrared data to search for Lyman-break galaxies at z >∼ 6.5 (i.e. within the first billion years of the Universe). I find four possible (two robust) z′-drop candidates (z >∼ 6.5) and four possible (but no robust) Y -drop candidates (z >∼ 7). I use my results to place constraints on the luminosity function at z ∼ 6.5 and find significant evolution in the population of Lyman-break galaxies between 3 < z <∼ 6.5. I also explore obscured star formation with a population of 70μm selected galaxies over the COSMOS field. I use AAT spectroscopy in conjunction with other available spectroscopic redshifts for my sample, and photometric redshifts otherwise, to calculate the total infrared luminosity of each galaxy. Two libraries of spectral energy distributions are considered; Siebenmorgen & Krügel (2007) templates and Chary & Elbaz (2001) models. We have supplemented our data with that of Huynh et al. (2007) collected over the GOODS-North field and adapted it to directly compare with the results of this work. The far-infrared luminosity function is then determined using the 1/Vmax technique. A double power law parameterisation is found to provide the best fit to the data. The far-infrared luminosity function was fitted for all parameters and the evolution was measured out to z ∼ 1. Three different types of evolution were allowed, pure luminosity, pure density and luminosity dependent density evolution. In all cases strong positive evolution was evident with the best-fit case being pure luminosity evolution where p = 2.4+0.6 −0.7. Due to the larger volume surveyed compared to previous studies, this work provides better constraints on the bright end of the far-infrared luminosity function displaying a shallower bright end slope (α2 ∼ −1.6) than previously determined, implying a higher number density of the most luminous objects and thereby a greater contribution from these objects to the total infrared energy density. However the shallower slope determined here can be reconciled with other work if the Chary & Elbaz (2001) models are used instead of the Siebenmorgen & Krügel templates; demonstrating that spectral energy distribution model selection is a key component in determining luminosity functions at far-infrared wavelengths. The far-infrared–radio correlation (FIRC; qIR) was determined for the sample of 70μm selected star-forming galaxies using 1.4GHz radio data over the COSMOS field, and no evolution was found out to z ∼ 2. The 70μm monochromatic evolution in the FIRC was also examined (q70) and no evolution was found in this parameter with redshift.

In my thesis I investigate the luminous z ~ 3 Lyman break galaxies in deep wide field surveys. In the first part of the thesis, I use the LBT/LUCIFER to observe a lensed high-redshift star-forming galaxy (J0900+2234) at z = 2.03. With the high S/N near-IR spectroscopic observations, I reveal the detailed physical properties of this high-redshift galaxy, including SFR, metallicity, dust extinction, dynamical mass, and electron number density. In the second part of the thesis, I select a large sample of LBGs at z ~ 3 from our new LBT Bootes field survey, and study the bright end luminosity function (LF), stellar mass function (SMF) and clustering properties of bright LBGs (1L* < L < 2.5L*). Together with other LF and SMF measurements, the evolution of LF and SMF can be well described by continuously rising star formation history model. Using the clustering measurements in this work and other works, a tight relation between the average host galaxy halo mass and the galaxy star formation rate is found, which can be interpreted as arising from cold flow accretion. The relation also suggests that the cosmic star formation efficiency is about 5%-20% of the total cold flow mass. This cosmic star formation efficiency does not evolve with redshift (from z ~ 5 to z ~ 3), hosting dark matter halo mass (10¹¹-10¹³ M⊙), or galaxy luminosity (from 0.3L* to 3L*).In the third and fourth parts, with the spectroscopic follow-up observations of the bright LBGs, I establish a sample of spectroscopically-confirmed ultra-luminous LBGs (ULBGs) in NOAO Bootes field. With this new ULBG sample, the rest-frame UV LF of LBG at M(1700Å) = -23.0 was measured for the first time. I find that the ULBGs have larger outflow velocity, broader Lyα emission and ISM absorption line profiles, and more prominent CIV P-Cygni profile. This profile may imply a top-heavy IMF in these ULBGs. The ULBGs have larger stellar mass and SFR, but smaller dust extinction than the typical L* LBGs at z ~ 2 - 3. We proposed two evolutionary scenarios, pre-burst and post-burst. The properties of the ULBGs, especially the morphologies, prefer the pre-starburst scenario. Further high spatial resolution HST imaging and IFU spectroscopic observations will allow us to distinguish these two scenarios.

No description available.

This thesis describes a new approach to the study of high-redshift star-formation and its environments that can be applied to large high-redshift surveys. Instead of relying on spectroscopy or narrow-band photometry to study galaxy line emission in detail, the properties of large emission line galaxy (ELG)populations are estimated from broadband photometry by measuring colour-residuals against colours drawn from a set of line-free stochastic burst models-based on (Bruzual & Charlot, 2003). Simulated star-formation histories drawn from semi-analytic and adaptive-mesh-refinement codes were converted into mock galaxy colours, but neither could-span the range of observed galaxy colours at high redshift. Instead, an existing set of exponentially declining star-formation models with stochastic bursts was used, because it closely spanned the range in observed galaxy colours in the bandsthat were line-free at each redshift. Small colour offsets were measured between the models and the observations, corresponding to the equivalent widths (EWs)of Hα, [OIII] and [OII]. In this way, I measure the rest-frame Equivalent Widths of the Hα, [OIII]and [OII] emission lines as they are redshifted through all filters from CANDELS(near-continuous U to 4.5μm coverage) for a large sample of galaxies from z=0.1up to z=5. This approach relies solely on the line-free models, a set of existing reliable photometric redshifts, and a colour cut (B−K < 2 or equivalent) to select only the dust-free young objects (the majority of identified emission-line galaxies). Once correctly identified, I apply this method to the CANDELS-UDS photometry to characterise the properties of Emission-Line Galaxies (ELGs) through these lines. I find that in this sample the Hα and [OIII] ELG fraction with EW > 150Årises from < 5% at z < 1 up to 40% at z > 2. The co-moving ELG density rises from 5 to 30 ×10 −4 /Mpc −3 at z=2.3. The evolution of median Hα EW with redshift is consistent with results from HiZELS and 3D-HST yielding median EW ∼ M 0.25 (1+z) 1.75 up to z=2.3, from which it departs to values of 450Å atz=4.3. [OIII] remains weaker than Hα for z < 3 and matches its values above that redshift. [OIII] also displays a larger fraction of extreme EWs than Hα. [OII], while correctly identified, never becomes as extreme as the other two lines lines, even when corrected for the evolving continuum. This is evidence of an increasing [OIII]/[OII] ratio with increasing z through-out this sample. While these results agree with spectroscopic and narrow-band surveys, the use of the deeper broadband filter coverage enables a systematic measurement of the increasingly prevalent high EWs ( > 500Å) in galaxies at every redshift spanning the 10 8 to 10 10.5 M range. Subsequently, this method was applied to all the other CANDELS fields (GOODS-South and North, COSMOS and EGS) and further corroborates these results. These results further show that EW dependence on mass is steeper for [OIII] than for Hα. Line EWs are then converted into luminosities for the three lines and fitting formulas are obtained, displaying L Hα ∼(1+z) 3.2 M 0.45−0.6log(1+z), with similar results for the other lines. L Hα is converted into star-formation rate and specific star-formation rate (sSFR). sSFR at low-z aligns approximately with the main sequence (with a steeper dependence in mass), but at high-redshift sSFR remains above the main sequence by a factor of 2 and rising towards medians SFR=100/Gyr around log(M/M )=9, showing a departure of the main sequence of star formation at lower masses log(M/M ) < 9.5. The SFRD of ELGs is 1% at low redshift, but rises to 30% at z=4.5. The L [OIII] /L Hα ratio is used to estimate L [OIII] /L Hβ and the ionization parameter q, for which the median atz > 0.5 stays approximately constant at 10 8 cm/s, and increases with mass. Using the L [OIII] /L [OII] ratio and q, median metallicity is shown to be sub-solar, and can be tentatively estimated for z > 0.5 to be Z/Z ∼0.3. The errors are large, but this could also mean a large range in metallicity from Z to 0.1Z . L [OIII] /L [OII] rises with sSFR as shown in the literature. This method shows great potential to survey emission-line-derived physical quantities for large galaxy populations with a low computational footprint, which could be particularly useful for pixel-by-pixel EW imaging. It is also flexibile, which allows it to be applied to any future deep multi-broadband fields.

Magíster en Ciencias, Mención Astronomía / La observación de emisión Lyman alpha (Lyα) proveniente de galaxias es una técnica ampliamente utilizada para el estudio del universo a alto redshift (e.g. Shapley et al. 2003, Ouchi et al. 2008, Stark et al. 2010, Blanc et al. 2011). Sin embargo, a pesar de su importancia, los estudios estadísticos de esta emisión no abordan posibles sesgos al elaborar las muestras de objetos, induciendo discrepancias. Diferentes metodologías inducen selecciones en masa estelar (M∗), tasa de formación estelar (SFR) y metalicidad. Los perjuicios asociados a la forma actual de estudiar la emisión Lyα no solamente se restringen a sesgos en los resultados obtenidos, sino que también limitan nuestro entendimiento de este proceso radiativo en la población de galaxias. En consecuencia, nuestra comprensión de la emisión Lyα en dicha población es actualmente altamente especulativo. Todas estas razones justifican la necesidad de llevar a cabo un estudio de emisión Lyα en la población de galaxias, lo cual es el objetivo de esta tesis. El presente trabajo detalla los resultados de un exhaustivo análisis de emisión Lyα a alto redshift. Para ello, primero diseñamos una muestra de 629 galaxias observadas por CANDELS (Koekemoer et al. 2011, Grogin et al. 2011). Dicha muestra se encuentra especialmente di- señada para abarcar el rango de masa estelar 7.6 < log (M∗[M⊙]) < 10.6 y rango de redshift 3 < z < 4.6. Tras esta selección, realizamos espectroscopía de los objetos con el Michigan/- Magellan Fiber System (M2FS; Mateo et al. 2012). De esta forma, contamos con mediciones de flujo de Lyα, además de la fotometría CANDELS, la cual permite obtener masa estelar, luminosidad, tasa de formación estelar, y extinción para cada galaxia. Observamos que el Ancho Equivalente y Fracción de escape de Lyα decrecen con la masa estelar, luminosidad en el UV, tasa de formación estelar, y extinción de las galaxias. Además, introducimos aplica- ciones de estadística Bayesiana en este campo de la astrofísica. Esto nos permite concluir que un modelo de distribución exponencial es el más apropiado para reproducir nuestras distri- buciones de Ancho Equivalente de Lyα, además de caracterizar la completitud y significancia de las correlaciones que observamos. También estudiamos los impactos que tienen diferentes técnicas de selección de galaxias en las estadísticas observadas de Lyα. Lyman Break Galaxies y estudios de Lyα emitters seleccionan preferentemente galaxias de baja masa estelar y poco polvo interestelar. Finalmente, realizamos la primera predicción semi-analítica de la fracción de Lyα emitters hasta redshift 7, la cual se puede utilizar para restringir observacionalmente la época de reionización. Todos estos resultados no solamente contribuyen a comprender de mejor manera este tipo de radiación, sino que también establecen un nuevo marco para el análisis estadístico de este trazador del universo temprano.

abstract: New measurements of the Hα luminosity function (LF) and star formation rate (SFR) volume density are presented for galaxies at z∼0.62 in the COSMOS field. These results are part of the Deep And Wide Narrowband Survey (DAWN), a unique infrared imaging program with large areal coverage (∼1.1 deg 2 over 5 fields) and sensitivity (9.9 × 10 −18 erg/cm 2 /s at 5σ). The present sample, based on a single DAWN field, contains 116 Hα emission- line candidates at z∼0.62, 25% of which have spectroscopic confirmations. These candidates have been selected through comparison of narrow and broad-band images in the infrared and through matching with existing catalogs in the COSMOS field. The dust-corrected LF is well described by a Schechter function with L* = 10 42.64±0.92 erg s −1 , Φ* = 10 −3.32±0.93 Mpc −3 (L* Φ* = 10 39.40±0.15 ), and α = −1.75 ± 0.09. From this LF, a SFR density of ρ SF R =10 −1.37±0.08 M○ yr −1 Mpc −3 was calculated. An additional cosmic variance uncertainty of ∼ 20% is also expected. Both the faint end slope and luminosity density that are derived are consistent with prior results at similar redshifts, with reduced uncertainties. An analysis of these Hα emitters’ sizes is also presented, showing a direct corre- lation between the galaxies’ sizes and their Hα emission. / Dissertation/Thesis / Masters Thesis Astrophysics 2017

We report the results of a faint quasar survey in a one-square-degree field. The aim is to test the Y - K/g - z and J - K/i - Y color selection criteria for quasars at faint magnitudes to obtain a complete sample of quasars based on deep optical and near-infrared color-color selection and to measure the faint end of the quasar luminosity function (QLF) over a wide redshift range. We carried out a quasar survey based on the Y - K/g - z and J - K/i - Y quasar selection criteria, using the deep Y-band data obtained from our CFHT/WIRCam Y-band images in a two-degree field within the F22 field of the VIMOS VLT deep survey, optical co-added data from Sloan Digital Sky Survey Stripe 82 and deep near-infrared data from the UKIDSS Deep Extragalactic Survey in the same field. We discovered 25 new quasars at 0.5 < z < 4.5 and i < 22.5 mag within one-square-degree field. The survey significantly increases the number of faint quasars in this field, especially at z similar to 2-3. It confirms that our color selections are highly complete in a wide redshift range (z < 4.5), especially over the quasar number density peak at z similar to 2-3, even for faint quasars. Combining all previous known quasars and new discoveries, we construct a sample with 109 quasars and measure the binned QLF and parametric QLF. Although the sample is small, our results agree with a pure luminosity evolution at lower redshift and luminosity evolution and density evolution model at redshift z > 2.5.

We present a survey of the [C II] 158 mu m line and underlying far-infrared (FIR) dust continuum emission in a sample of 27 greater than or similar to 6 quasars using the Atacama Large Millimeter Array (ALMA) at similar to 1 '' resolution. The [C II] line was significantly detected (at > 5-sigma) in 23 sources (85%). We find typical line luminosities of L-[C (II]) = 10(9-10) L-circle dot, and an average line width of similar to 385 km s(-1). The [C II]-to-far-infrared luminosity ratios ([C II]/FIR) in our sources span one order of magnitude, highlighting a variety of conditions in the star-forming medium. Four quasar host galaxies are clearly resolved in their [C II] emission on a few kpc scales. Basic estimates of the dynamical masses of the host galaxies give masses between 2 x 10(10) and 2 x 10(11) M-circle dot, i.e., more than an order of magnitude below what is expected from local scaling relations, given the available limits on the masses of the central black holes (> 3 x 10(8) M-circle dot, assuming Eddington-limited accretion). In stacked ALMA [C II] spectra of individual sources in our sample, we find no evidence of a deviation from a single Gaussian profile. The quasar luminosity does not strongly correlate with either the [C II] luminosity or equivalent width. This survey (with typical on-source integration times of 8 minutes) showcases the unparalleled sensitivity of ALMA at millimeter wavelengths, and offers a unique reference sample for the study of the first massive galaxies in the universe.

We report the discovery and constrain the physical conditions of the interstellar medium of the highest-redshift millimeter-selected dusty star-forming galaxy to date, SPT-S J031132-5823.4 (hereafter SPT0311-58), at z = 6.900 +/- 0.002. SPT0311-58 was discovered via its 1.4 mm thermal dust continuum emission in the South Pole Telescope (SPT)-SZ survey. The spectroscopic redshift was determined through an Atacama Large Millimeter/submillimeter Array 3 mm frequency scan that detected CO(6-5), CO(7-6), and [C I](2-1), and subsequently was confirmed by detections of CO(3-2) with the Australia Telescope Compact Array and[C II] with APEX. We constrain the properties of the ISM in SPT0311-58 with a radiative transfer analysis of the dust continuum photometry and the CO and [C I] line emission. This allows us to determine the gas content without ad hoc assumptions about gas mass scaling factors. SPT0311-58 is extremely massive, with an intrinsic gas mass of M-gas = 3.3 +/- 1.9 x 10(11) M-circle dot. Its large mass and intense star formation is very rare for a source well into the epoch of reionization.