Browsing by Autor "U. Andrade"

Now showing 1 - 3 of 3

DESI DR2 results. I. Baryon acoustic oscillations from the Lyman alpha forest
(American Physical Society, 2025) M. Abdul Karim; J. Aguilar; S. Ahlen; C. Allende Prieto; O. Alves; A. Anand; U. Andrade; E. Armengaud; A. Aviles; S. Bailey
We present the baryon acoustic oscillation (BAO) measurements with the Lyman-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>α</a:mi></a:math> (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>Ly</c:mi><c:mi>α</c:mi></c:math>) forest from the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI) survey. Our BAO measurements include both the autocorrelation of the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>Ly</e:mi><e:mi>α</e:mi></e:math> forest absorption observed in the spectra of high-redshift quasars and the cross-correlation of the absorption with the quasar positions. The total sample size is approximately a factor of 2 larger than the DR1 dataset, with forest measurements in over 820,000 quasar spectra and the positions of over 1.2 million quasars. We describe several significant improvements to our analysis in this paper, and two supporting papers describe improvements to the synthetic datasets that we use for validation and how we identify damped <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>Ly</g:mi><g:mi>α</g:mi></g:math> absorbers. Our main result is that we have measured the BAO scale with a statistical precision of 1.1% along and 1.3% transverse to the line of sight, for a combined precision of 0.65% on the isotropic BAO scale at <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msub><i:mi>z</i:mi><i:mi>eff</i:mi></i:msub><i:mo>=</i:mo><i:mn>2.33</i:mn></i:math>. This excellent precision, combined with recent theoretical studies of the BAO shift due to nonlinear growth, motivated us to include a systematic error term in <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>Ly</k:mi><k:mi>α</k:mi></k:math> BAO analysis for the first time. We measure the ratios <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msub><m:mi>D</m:mi><m:mi>H</m:mi></m:msub><m:mo stretchy="false">(</m:mo><m:msub><m:mi>z</m:mi><m:mi>eff</m:mi></m:msub><m:mo stretchy="false">)</m:mo><m:mo>/</m:mo><m:msub><m:mi>r</m:mi><m:mi>d</m:mi></m:msub><m:mo>=</m:mo><m:mn>8.632</m:mn><m:mo>±</m:mo><m:mn>0.098</m:mn><m:mo>±</m:mo><m:mn>0.026</m:mn></m:math> and <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:msub><q:mi>D</q:mi><q:mi>M</q:mi></q:msub><q:mo stretchy="false">(</q:mo><q:msub><q:mi>z</q:mi><q:mi>eff</q:mi></q:msub><q:mo stretchy="false">)</q:mo><q:mo>/</q:mo><q:msub><q:mi>r</q:mi><q:mi>d</q:mi></q:msub><q:mo>=</q:mo><q:mn>38.99</q:mn><q:mo>±</q:mo><q:mn>0.52</q:mn><q:mo>±</q:mo><q:mn>0.12</q:mn></q:math>, where <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"><u:msub><u:mi>D</u:mi><u:mi>H</u:mi></u:msub><u:mo>=</u:mo><u:mi>c</u:mi><u:mo>/</u:mo><u:mi>H</u:mi><u:mo stretchy="false">(</u:mo><u:mi>z</u:mi><u:mo stretchy="false">)</u:mo></u:math> is the Hubble distance, <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"><y:msub><y:mi>D</y:mi><y:mi>M</y:mi></y:msub></y:math> is the transverse comoving distance, <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:msub><ab:mi>r</ab:mi><ab:mi>d</ab:mi></ab:msub></ab:math> is the sound horizon at the drag epoch, and we quote both the statistical and the theoretical systematic uncertainty. The companion paper presents the BAO measurements at lower redshifts from the same dataset and the cosmological interpretation.
DESI DR2 results. II. Measurements of baryon acoustic oscillations and cosmological constraints
(American Physical Society, 2025) M. Abdul Karim; J. Aguilar; S. P. Ahlen; Shadab Alam; L. Allen; Carlos Allende Prieto; O. Alves; Abhijeet Anand; U. Andrade; E. Armengaud
We present baryon acoustic oscillation (BAO) measurements from more than 14 million galaxies and quasars drawn from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2), based on three years of operation. For cosmology inference, these galaxy measurements are combined with DESI Lyman- <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>α</a:mi> </a:math> forest BAO results presented in a companion paper (M. Abdul-Karim , companion paper, .). The DR2 BAO results are consistent with DESI DR1 and the Sloan Digital Sky Survey, and their distance-redshift relationship matches those from recent compilations of supernovae (SNe) over the same redshift range. The results are well described by a flat <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi mathvariant="normal">Λ</c:mi> </c:math> cold dark matter ( <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:mi mathvariant="normal">Λ</f:mi> <f:mi>CDM</f:mi> </f:math> ) model, but the parameters preferred by BAO are in mild, <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mn>2.3</i:mn> <i:mi>σ</i:mi> </i:math> tension with those determined from the cosmic microwave background (CMB), although the DESI results are consistent with the acoustic angular scale <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msub> <k:mi>θ</k:mi> <k:mo>*</k:mo> </k:msub> </k:math> that is well measured by Planck. This tension is alleviated by dark energy with a time-evolving equation of state parametrized by <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:msub> <m:mi>w</m:mi> <m:mn>0</m:mn> </m:msub> </m:math> and <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:msub> <o:mi>w</o:mi> <o:mi>a</o:mi> </o:msub> </o:math> , which provides a better fit to the data, with a favored solution in the quadrant with <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:msub> <q:mi>w</q:mi> <q:mn>0</q:mn> </q:msub> <q:mo>></q:mo> <q:mo>−</q:mo> <q:mn>1</q:mn> </q:math> and <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msub> <s:mi>w</s:mi> <s:mi>a</s:mi> </s:msub> <s:mo><</s:mo> <s:mn>0</s:mn> </s:math> . This solution is preferred over <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"> <u:mi mathvariant="normal">Λ</u:mi> <u:mi>CDM</u:mi> </u:math> at <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"> <x:mn>3.1</x:mn> <x:mi>σ</x:mi> </x:math> for the combination of DESI BAO and CMB data. When also including SNe, the preference for a dynamical dark energy model over <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"> <z:mi mathvariant="normal">Λ</z:mi> <z:mi>CDM</z:mi> </z:math> ranges from <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline"> <cb:mn>2.8</cb:mn> <cb:mo>−</cb:mo> <cb:mn>4.2</cb:mn> <cb:mi>σ</cb:mi> </cb:math> depending on which SNe sample is used. We present evidence from other data combinations which also favor the same behavior at high significance. From the combination of DESI and CMB we derive 95% upper limits on the sum of neutrino masses, finding <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline"> <eb:mo>∑</eb:mo> <eb:msub> <eb:mi>m</eb:mi> <eb:mi>ν</eb:mi> </eb:msub> <eb:mo><</eb:mo> <eb:mn>0.064</eb:mn> <eb:mtext> </eb:mtext> <eb:mtext> </eb:mtext> <eb:mi>eV</eb:mi> </eb:math> assuming <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML" display="inline"> <gb:mi mathvariant="normal">Λ</gb:mi> <gb:mi>CDM</gb:mi> </gb:math> and <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML" display="inline"> <jb:mo>∑</jb:mo> <jb:msub> <jb:mi>m</jb:mi> <jb:mi>ν</jb:mi> </jb:msub> <jb:mo><</jb:mo> <jb:mn>0.16</jb:mn> <jb:mtext> </jb:mtext> <jb:mtext> </jb:mtext> <jb:mi>eV</jb:mi> </jb:math> in the <lb:math xmlns:lb="http://www.w3.org/1998/Math/MathML" display="inline"> <lb:msub> <lb:mi>w</lb:mi> <lb:mn>0</lb:mn> </lb:msub> <lb:msub> <lb:mi>w</lb:mi> <lb:mi>a</lb:mi> </lb:msub> </lb:math> model. Unless there is an unknown systematic error associated with one or more datasets, it is clear that <nb:math xmlns:nb="http://www.w3.org/1998/Math/MathML" display="inline"> <nb:mi mathvariant="normal">Λ</nb:mi> <nb:mi>CDM</nb:mi> </nb:math> is being challenged by the combination of DESI BAO with other measurements and that dynamical dark energy offers a possible solution.
Validation of the DESI DR2 measurements of baryon acoustic oscillations from galaxies and quasars
(American Physical Society, 2025) U. Andrade; E. Paillas; J. Mena-Fernández; Qinxun Li; Ashley J. Ross; S. Nadathur; M. Rashkovetskyi; A. Pérez-Fernández; Hee‐Jong Seo; Nicole M. Sanders
The Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) galaxy and quasar clustering data represents a significant expansion of data from Data Release 1 (DR1), providing improved statistical precision in baryon acoustic oscillation (BAO) constraints across multiple tracers, including bright galaxies, luminous red galaxies, emission line galaxies, and quasars. In this paper, we validate the BAO analysis of DR2. We present the results of robustness tests on the blinded DR2 data and, after unblinding, consistency checks on the unblinded DR2 data. All results are compared with those obtained from a suite of mock catalogs that replicate the selection and clustering properties of the DR2 sample. We confirm the consistency of DR2 BAO measurements with DR1 while achieving a reduction in statistical uncertainties due to the increased survey volume and completeness. The combined BAO precision, including both statistical and systematic errors, improves from <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mo>∼</a:mo> <a:mn>0.52</a:mn> <a:mo>%</a:mo> </a:math> in DR1 to 0.30% in DR2—a factor of 1.7 gain. We assess the impact of analysis choices, including different data vectors (correlation function vs power spectrum), modeling approaches and systematics treatments, and an assumption of the Gaussian likelihood, finding that our BAO constraints are stable across these variations and assumptions with a few minor refinements to the baseline setup of the DR1 BAO analysis. We summarize a series of pre-unblinding tests that confirmed the readiness of our analysis pipeline, the final systematic errors, and the DR2 BAO analysis baseline. The successful completion of these tests led to the unblinding of the DR2 BAO measurements, ultimately leading to the DESI DR2 cosmological analysis, with their implications for the expansion history of the Universe and the nature of dark energy presented in the DESI key paper (companion paper).