Browsing by Autor "S. Nadathur"

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Cosmological implications of DESI DR2 BAO measurements in light of the latest ACT DR6 CMB data
(American Physical Society, 2025) C. Garcia-Quintero; H. E. Noriega; A. de Mattia; Alejandro Avilés; K. Lodha; D. Chebat; J. Rohlf; S. Nadathur; Willem Elbers; José Aguilar
We report cosmological results from the Dark Energy Spectroscopic Instrument (DESI) measurements of baryon acoustic oscillations (BAO) when combined with recent data from the Atacama Cosmology Telescope (ACT). By jointly analyzing ACT and data and applying conservative cuts to overlapping multipole ranges, we assess how different <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>P</a:mi><a:mi>l</a:mi><a:mi>a</a:mi><a:mi>n</a:mi><a:mi>c</a:mi><a:mi>k</a:mi><a:mo>+</a:mo><a:mi>ACT</a:mi></a:mrow></a:math> dataset combinations affect consistency with DESI. While ACT alone exhibits a tension with DESI exceeding <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mn>3</c:mn><c:mi>σ</c:mi></c:mrow></c:math> within the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi mathvariant="normal">Λ</e:mi><e:mi>CDM</e:mi></e:math> model, this discrepancy is reduced when ACT is analyzed in combination with . For our baseline DESI DR2 <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mrow><h:mi>BAO</h:mi><h:mo>+</h:mo><h:mi>P</h:mi><h:mi>l</h:mi><h:mi>a</h:mi><h:mi>n</h:mi><h:mi>c</h:mi><h:mi>k</h:mi></h:mrow></h:math> <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mrow><j:mi mathvariant="normal">P</j:mi><j:mrow><j:mi mathvariant="normal">R</j:mi><j:mn>4</j:mn><j:mo>+</j:mo><j:mi>ACT</j:mi></j:mrow></j:mrow></j:math> likelihood combination, the preference for evolving dark energy over a cosmological constant is about <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mrow><n:mn>3</n:mn><n:mi>σ</n:mi></n:mrow></n:math>, increasing to over <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"><p:mrow><p:mn>4</p:mn><p:mi>σ</p:mi></p:mrow></p:math> with the inclusion of type Ia supernova data. While the dark energy results remain quite consistent across various combinations of and ACT likelihoods with those obtained by the DESI collaboration, the constraints on neutrino mass are more sensitive, ranging from <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"><r:mrow><r:mo>∑</r:mo><r:msub><r:mrow><r:mi>m</r:mi></r:mrow><r:mrow><r:mi>ν</r:mi></r:mrow></r:msub><r:mo><</r:mo><r:mn>0.061</r:mn><r:mtext> </r:mtext><r:mtext> </r:mtext><r:mi>eV</r:mi></r:mrow></r:math> in our baseline analysis, to <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:mo>∑</t:mo><t:msub><t:mi>m</t:mi><t:mi>ν</t:mi></t:msub><t:mo><</t:mo><t:mn>0.077</t:mn><t:mtext> </t:mtext><t:mtext> </t:mtext><t:mi>eV</t:mi></t:math> (95% confidence level) in the CMB likelihood combination chosen by ACT when imposing the physical prior <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mo>∑</v:mo><v:msub><v:mi>m</v:mi><v:mi>ν</v:mi></v:msub><v:mo>></v:mo><v:mn>0</v:mn><v:mtext> </v:mtext><v:mtext> </v:mtext><v:mi>eV</v:mi></v:math>.
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).