Star-forming galaxies as tools for cosmology in new-generation spectroscopic surveys

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 20 de mayo de 2016This Ph.D. thesis is a collection of clustering studies in different galaxy samples selected from the Sloan Digital Sky Survey and the SDSS-III/Baryon Oscillation Spectroscopic Survey. By measuring the two-point correlation function of galaxy populations that differ in redshift, color, luminosity, star-formation history and bias, and using high-resolution large-volume cosmological simulations, I have studied the clustering properties of these galaxies within the large scale structure of the Universe, and those of their host dark matter halos. The aim of this research is to stress the importance of star-forming galaxies as tools to perform cosmology with the new generation of wide-field spectroscopic surveys. Among the galaxies considered, I have focused my investigation on a particular class whose rest-frame optical spectra exhibit strong nebular emission lines. Such galaxies, better known as Emission-Line Galaxies (ELGs), will be the main targets of near-future missions – both ground-based, as the Dark Energy Spectroscopic Instrument, the 4-metre Multi-Object Spectroscopic Telescope, the Subaru Prime Focus Spectrograph, and space-based as EUCLID. All these surveys will use emission-line galaxies up to redshift z 2 to trace star formation and to measure the Baryon Acoustic Oscillations as standard ruler, in the attempt to unveil the nature of dark energy. Therefore, understanding how to measure and model the ELG clustering properties, and how they populate their host dark matter halos, are fundamental issues that I have addressed in this thesis by using state-of-the-art data, currently available, to prepare the clustering prospects and theoretical basis for future experiments.Esta tesis doctoral presenta una colección de estudios del agrupamiento (i.e. clustering) de las galaxias en la estructura a gran escala del Universo en diferentes muestras seleccionadas de los catálogos de galaxias del Sloan Digital Sky Survey y del SDSS-III/Baryon Oscillation Spectroscopic Survey. Midiendo la función de correlación de dos puntos en las poblaciones de galaxias con diferente corrimiento al rojo, color, luminosidad, proceso de formación estelar y bias, he estudiado, utilizando simulaciones cosmológicas de alta resolución y gran volumen, las propiedades de su agrupamiento dentro de la estructura a gran escala del Universo y de los halos de materia oscura en los que residen dichas galaxias. El objetivo de esta investigación es enfatizar la importancia de las galaxias con formación estelar como instrumentos para las medidas cosmológicas en los grandes cartografiados espectroscópicos de nueva generación. Entre las galaxias seleccionadas, he enfocado mi estudio en un tipo particular cuyos espectros muestran líneas de emisión nebular. Dichas galaxias, denominadas ELGs, serán las fuentes principales que observarán los nuevos proyectos, tanto desde tierra, como son el Dark Energy Spectroscopic Instrument, el 4-metre Multi-Object Spectroscopic Telescope, the Subaru Prime Focus Spectrograph, y desde el espacio como EUCLID. Todos estos cartografiados utilizarán galaxias con líneas de emisión hasta redshift z 2 como indicadores de formación estelar y para medir las oscilaciones acústicas bariónicas como medida de distancia, y así poder conocer la naturaleza de la energía oscura. Por lo tanto, entender cómo medir y reproducir teóricamente el agrupamiento de las ELGs, y cómo éstas galaxias pueblan sus halos, son puntos fundamentales que he estudiado en esta tesis utilizando los datos actuales para preparar las bases teóricas y el estudio de sistemáticos de cara a los experimentos futuros

Does jackknife scale really matter for accurate large-scale structure covariances?

The jackknife method gives an internal covariance estimate for large-scale structure surveys and allows model-independent errors on cosmological parameters. Using the SDSS-III BOSS CMASS sample, we study how the jackknife size and number of resamplings impact the precision of the covariance estimate on the correlation function multipoles and the error on the inferred baryon acoustic scale. We compare the measurement with the MultiDark Patchy mock galaxy catalogues, and we also validate it against a set of log-normal mocks with the same survey geometry. We build several jackknife configurations that vary in size and number of resamplings. We introduce the Hartlap factor in the covariance estimate that depends on the number of jackknife resamplings. We also find that it is useful to apply the tapering scheme to estimate the precision matrix from a limited number of resamplings. The results from CMASS and mock catalogues show that the error estimate of the baryon acoustic scale does not depend on the jackknife scale. For the shift parameter $\alpha$, we find an average error of 1.6%, 2.2% and 1.2%, respectively from CMASS, Patchy and log-normal jackknife covariances. Despite these uncertainties fluctuate significantly due to some structural limitations of the jackknife method, our $\alpha$ estimates are in reasonable agreement with published pre-reconstruction analyses. Jackknife methods will provide valuable and complementary covariance estimates for future large-scale structure surveys.Comment: 13 pages, 8 figures, 3 table

The High-Mass End of the Red Sequence at z~0.55 from SDSS-III/BOSS: completeness, bimodality and luminosity function

We have developed an analytical method based on forward-modeling techniques to characterize the high-mass end of the red sequence (RS) galaxy population at redshift $z\sim0.55$, from the DR10 BOSS CMASS spectroscopic sample, which comprises $\sim600,000$ galaxies. The method, which follows an unbinned maximum likelihood approach, allows the deconvolution of the intrinsic CMASS colour-colour-magnitude distributions from photometric errors and selection effects. This procedure requires modeling the covariance matrix for the i-band magnitude, g-r colour and r-i colour using Stripe 82 multi-epoch data. Our results indicate that the error-deconvolved intrinsic RS distribution is consistent, within the photometric uncertainties, with a single point ($<0.05~{\rm{mag}}$) in the colour-colour plane at fixed magnitude, for a narrow redshift slice. We have computed the high-mass end ($^{0.55}M_i \lesssim -22$) of the $^{0.55}i$-band RS Luminosity Function (RS LF) in several redshift slices within the redshift range $0.52<z<0.63$. In this narrow redshift range, the evolution of the RS LF is consistent, within the uncertainties in the modeling, with a passively-evolving model with $\Phi_* = (7.248 \pm 0.204) \times10^{-4}$ Mpc$^{-3}$ mag$^{-1}$, fading at a rate of $1.5\pm0.4$ mag per unit redshift. We report RS completeness as a function of magnitude and redshift in the CMASS sample, which will facilitate a variety of galaxy-evolution and clustering studies using BOSS. Our forward-modeling method lays the foundations for future studies using other dark-energy surveys like eBOSS or DESI, which are affected by the same type of photometric blurring/selection effects.Comment: 27 pages, 20 figures, accepted for publication in MNRA

UNITSIM-Galaxies: Data release and clustering of emission-line galaxies

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Monthly Notices of the Royal Astronomical Society 510.4 (2022): 5392-5407 is available online at: https://academic.oup.com/mnras/article-abstract/510/4/5392/6505155?redirectedFrom=fulltextNew surv e ys such as European Space Agenc ys (ESA's) Euclid mission are planned to map with unprecedented precision the large-scale structure of the Universe by measuring the 3D positions of tens of millions of galaxies. It is necessary to develop theoretically modelled galaxy catalogues to estimate the expected performance and to optimize the analysis strategy of these surv e ys. We populate two pairs of (1 h -1 Gpc) 3 volume dark matter-only simulations from the UNIT project with galaxies using the Semi-Analytic Galaxy Evolution semi-analytic model of galaxy formation, coupled to the photoionization model GET EMLINES to estimate their H αemission. These catalogues represent a unique suite that includes galaxy formation physics and -thanks to the fixed-pair technique used -an ef fecti ve volume of ∼(5 h -1 Gpc ) 3 , which is several times larger than the Euclid surv e y. We present the performance of these data and create five additional emission-line galaxy (ELG) catalogues by applying a dust-attenuation model as well as adjusting the flux threshold as a function of redshift in order to reproduce Euclid-forecast d N /d z values. As a first application, we study the abundance and clustering of those model H αELGs: For scales greater than ∼5 h -1 Mpc, we find a scale- independent bias with a value of b ∼1 at redshift z ∼0.5, that can increase nearly linearly to b ∼4 at z ∼2, depending on the ELG catalogue. Model galaxy properties, including their emission-line fluxes (with and without dust extinction) are publicly availabl

DESI Mock Challenge: Halo and galaxy catalogs with the bias assignment method

We present a novel approach to the construction of mock galaxy catalogues for large-scale structure analysis based on the distribution of dark matter halos obtained with effective bias models at the field level. We aim to produce mock galaxy catalogues capable of generating accurate covariance matrices for a number of cosmological probes that are expected to be measured in current and forthcoming galaxy redshift surveys (e.g. two- and three-point statistics). We use the bias assignment method (BAM) to model the statistics of halo distribution through a learning algorithm using a few detailed $N$-body simulations, and approximated gravity solvers based on Lagrangian perturbation theory. Using specific models of halo occupation distributions, we generate galaxy mocks with the expected number density and central-satellite fraction of emission-line galaxies, which are a key target of the DESI experiment. BAM generates mock catalogues with per cent accuracy in a number of summary statistics, such as the abundance, the two- and three-point statistics of halo distributions, both in real and redshift space. In particular, the mock galaxy catalogues display $\sim 3\%-10\%$ accuracy in the multipoles of the power spectrum up to scales of $k\sim 0.4\,h^{-1}{\rm Mpc}$. We show that covariance matrices of two- and three-point statistics obtained with BAM display a similar structure to the reference simulation. BAM offers an efficient way to produce mock halo catalogues with accurate two- and three-point statistics, and is able to generate a variety of multi-tracer catalogues with precise covariance matrices of several cosmological probes. We discuss future developments of the algorithm towards mock production in DESI and other galaxy-redshift surveys. (Abridged)Comment: Accepted for publication at A&