Browsing by Autor "Willem Elbers"

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Constraints on neutrino physics from DESI DR2 BAO and DR1 full shape
(American Physical Society, 2025) Willem Elbers; Alejandro Avilés; H. E. Noriega; D. Chebat; A. Menegas; Carlos S. Frenk; C. García-Quintero; D. Gonzalez; Mustapha Ishak; O. Lahav
The Dark Energy Spectroscopic Instrument (DESI) Collaboration has obtained robust measurements of baryon acoustic oscillations in the redshift range <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>0.1</a:mn> <a:mo><</a:mo> <a:mi>z</a:mi> <a:mo><</a:mo> <a:mn>4.2</a:mn> </a:math> , based on the Lyman- <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>α</c:mi> </c:math> forest and galaxies from data release 2. We combine these measurements with cosmic microwave background (CMB) data from and the Atacama Cosmology Telescope to place our tightest constraints yet on the sum of neutrino masses. Assuming the cosmological <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 and three degenerate neutrino states, we find <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:mo>∑</h:mo> <h:msub> <h:mi>m</h:mi> <h:mi>ν</h:mi> </h:msub> <h:mo><</h:mo> <h:mn>0.0642</h:mn> <h:mtext> </h:mtext> <h:mtext> </h:mtext> <h:mi>eV</h:mi> </h:math> (95%) with a marginalized error of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"> <j:mi>σ</j:mi> <j:mo stretchy="false">(</j:mo> <j:mo>∑</j:mo> <j:msub> <j:mi>m</j:mi> <j:mi>ν</j:mi> </j:msub> <j:mo stretchy="false">)</j:mo> <j:mo>=</j:mo> <j:mn>0.020</j:mn> <j:mtext> </j:mtext> <j:mtext> </j:mtext> <j:mi>eV</j:mi> </j:math> . We also constrain the effective number of neutrino species, finding <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"> <n:msub> <n:mi>N</n:mi> <n:mi>eff</n:mi> </n:msub> <n:mo>=</n:mo> <n:mn>3.2</n:mn> <n:msubsup> <n:mn>3</n:mn> <n:mrow> <n:mo>−</n:mo> <n:mn>0.34</n:mn> </n:mrow> <n:mrow> <n:mo>+</n:mo> <n:mn>0.35</n:mn> </n:mrow> </n:msubsup> </n:math> (95%), in line with the Standard Model prediction. When accounting for neutrino oscillation constraints, we find a preference for the normal mass ordering and an upper limit on the lightest neutrino mass of <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"> <p:msub> <p:mi>m</p:mi> <p:mi>l</p:mi> </p:msub> <p:mo><</p:mo> <p:mn>0.023</p:mn> <p:mtext> </p:mtext> <p:mtext> </p:mtext> <p:mi>eV</p:mi> </p:math> (95%). However, we determine using frequentist and Bayesian methods that our constraints are in tension with the lower limits derived from neutrino oscillations. Correcting for the physical boundary at zero mass, we report a 95% Feldman-Cousins upper limit of <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"> <r:mo>∑</r:mo> <r:msub> <r:mi>m</r:mi> <r:mi>ν</r:mi> </r:msub> <r:mo><</r:mo> <r:mn>0.053</r:mn> <r:mtext> </r:mtext> <r:mtext> </r:mtext> <r:mi>eV</r:mi> </r:math> , breaching the lower limit from neutrino oscillations. Considering a more general Bayesian analysis with an effective cosmological neutrino mass parameter, <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:mrow> <t:mi>ν</t:mi> <t:mo>,</t:mo> <t:mi>eff</t:mi> </t:mrow> </t:msub> </t:math> , that allows for negative energy densities and removes unsatisfactory prior weight effects, we derive constraints that are in <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"> <v:mn>3</v:mn> <v:mi>σ</v:mi> </v:math> tension with the same oscillation limit, while the error rises to <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"> <x:mi>σ</x:mi> <x:mo stretchy="false">(</x:mo> <x:mo>∑</x:mo> <x:msub> <x:mi>m</x:mi> <x:mrow> <x:mi>ν</x:mi> <x:mo>,</x:mo> <x:mi>eff</x:mi> </x:mrow> </x:msub> <x:mo stretchy="false">)</x:mo> <x:mo>=</x:mo> <x:mn>0.053</x:mn> <x:mtext> </x:mtext> <x:mtext> </x:mtext> <x:mi>eV</x:mi> </x:math> . In the absence of unknown systematics, this finding could be interpreted as a hint of new physics not necessarily related to neutrinos. The preference of DESI and CMB data for an evolving dark energy model offers one possible solution. In the <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"> <bb:msub> <bb:mi>w</bb:mi> <bb:mn>0</bb:mn> </bb:msub> <bb:msub> <bb:mi>w</bb:mi> <bb:mi>a</bb:mi> </bb:msub> <bb:mi>CDM</bb:mi> </bb:math> model, we find <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"> <db:mo>∑</db:mo> <db:msub> <db:mi>m</db:mi> <db:mi>ν</db:mi> </db:msub> <db:mo><</db:mo> <db:mn>0.163</db:mn> <db:mtext> </db:mtext> <db:mtext> </db:mtext> <db:mi>eV</db:mi> </db:math> (95%), relaxing the neutrino tension. These constraints all rely on the effects of neutrinos on the cosmic expansion history. Using full-shape power spectrum measurements of data release 1 galaxies, we place complementary constraints that rely on neutrino free streaming. Our strongest such limit in <fb:math xmlns:fb="http://www.w3.org/1998/Math/MathML" display="inline"> <fb:mi mathvariant="normal">Λ</fb:mi> <fb:mi>CDM</fb:mi> </fb:math> , using selected CMB priors, is <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline"> <ib:mo>∑</ib:mo> <ib:msub> <ib:mi>m</ib:mi> <ib:mi>ν</ib:mi> </ib:msub> <ib:mo><</ib:mo> <ib:mn>0.193</ib:mn> <ib:mtext> </ib:mtext> <ib:mtext> </ib:mtext> <ib:mi>eV</ib:mi> </ib:math> (95%).
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>.
PAC in DESI. I. Galaxy stellar mass function into the 106 M⊙ frontier
(Oxford University Press, 2025) Kun Xu; Yipeng Jing; Shaun Cole; Carlos S. Frenk; Sownak Bose; Willem Elbers; Hesheng Wang; Yirong Wang; Shannon Moore; J. Aguilar
ABSTRACT The Photometric objects Around Cosmic webs (PAC) method integrates cosmological photometric and spectroscopic surveys, offering valuable insights into galaxy formation. PAC measures the excess surface density of photometric objects, $\bar{n}_2w_{{\rm {p}}}$, with specific physical properties around spectroscopic tracers. In this study, we improve the PAC method to make it more rigorous and eliminate the need for redshift bins. We apply the enhanced PAC method to the DESI Y1 BGS Bright spectroscopic sample and the deep Dark Energy Camera Legacy Survey (DECaLS) photometric sample, obtaining $\bar{n}_2w_{{\mathrm {p}}}$ measurements across the complete stellar mass range, from $10^{5.3}$ to $10^{11.5}\,{\rm M}_{\odot }$ for blue galaxies, and from $10^{6.3}$ to $10^{11.9}\,{\rm M}_{\odot }$ for red galaxies. We combine $\bar{n}_2w_{{\rm {p}}}$ with $w_{{\rm {p}}}$ measurements from the BGS sample, which is not necessarily complete in stellar mass. Assuming that galaxy bias is primarily determined by stellar mass and colour, we derive the galaxy stellar mass functions (GSMFs) down to $10^{5.3}\,{\rm M}_{\odot }$ for blue galaxies and $10^{6.3}\,{\rm M}_{\odot }$ for red galaxies, while also setting lower limits for smaller masses. The blue and red GSMFs are well described by single and double Schechter functions, respectively, with low-mass end slopes of $\alpha _{\rm {blue}}=-1.54^{+0.02}_{-0.02}$ and $\alpha _{\rm {red}}=-2.50^{+0.08}_{-0.08}$, resulting in the dominance of red galaxies below $10^{7.6}\,{\rm M}_{\odot }$. Stage-IV cosmological photometric surveys, capable of reaching 2–3 mag deeper than DECaLS, present an opportunity to explore the entire galaxy population in the local universe with PAC. This advancement allows us to address critical questions regarding the nature of dark matter, the physics of reionization, and the formation of dwarf galaxies.
Positive Neutrino Masses with DESI DR2 via Matter Conversion to Dark Energy
(American Physical Society, 2025) S. P. Ahlen; Alejandro Avilés; Brian G. Cartwright; Kevin S. Croker; Willem Elbers; D. Farrah; Nicolas Fernandez; Gustavo Niz; J. Rohlf; G. Tarlé
The Dark Energy Spectroscopic Instrument (DESI) is a massively parallel spectroscopic survey on the Mayall telescope at Kitt Peak, which has released measurements of baryon acoustic oscillations determined from over 14 million extragalactic targets. We combine DESI Data Release 2 with CMB datasets to search for evidence of matter conversion to dark energy (DE), focusing on a scenario mediated by stellar collapse to cosmologically coupled black holes (CCBHs). In this physical model, which has the same number of free parameters as ΛCDM, DE production is determined by the cosmic star formation rate density (SFRD), allowing for distinct early- and late-time cosmologies. Using two SFRDs to bracket current observations, we find that the CCBH model: accurately recovers the cosmological expansion history, agrees with early-time baryon abundance measured by BBN, reduces tension with the local distance ladder, and relaxes constraints on the summed neutrino mass ∑m_{ν}. For these SFRDs, we find a peaked positive ∑m_{ν}<0.149 eV (95% confidence) and ∑m_{ν}=0.106_{-0.069}^{+0.050} eV, respectively, in good agreement with lower limits from neutrino oscillation experiments. A peak in ∑m_{ν}>0 results from late-time baryon consumption in the CCBH scenario and is expected to be a general feature of any model that converts sufficient matter to dark energy during and after reionization.