Browsing by Autor "D. Brooks"

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Atacama Cosmology Telescope DR6 and DESI: Structure growth measurements from the cross-correlation of DESI legacy imaging galaxies and CMB lensing from ACT DR6 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>P</mml:mi><mml:mi>l</mml:mi><mml:mi>a</mml:mi><mml:mi>n</mml:mi><mml:mi>c</mml:mi><mml:mi>k</mml:mi></mml:math> PR4
(American Physical Society, 2025) Frank J. Qu; Qianjun Hang; Gerrit S. Farren; Boris Bolliet; J. Aguilar; S. P. Ahlen; Shadab Alam; D. Brooks; Yan-Chuan Cai; E. Calabrese
We measure the growth of cosmic density fluctuations on large scales and across the redshift range <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mn>0.3</a:mn><a:mo><</a:mo><a:mi>z</a:mi><a:mo><</a:mo><a:mn>0.8</a:mn></a:math> through galaxy clustering and the cross-correlation of the ACT data release 6 cosmic microwave background (CMB) lensing map and galaxies from the Dark Energy Spectroscopic Instrument Legacy Survey, using three galaxy samples spanning the redshifts of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mn>0.3</c:mn><c:mo>≲</c:mo><c:mi>z</c:mi><c:mo>≲</c:mo><c:mn>0.45</c:mn></c:math>, <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>0.45</e:mn><e:mo>≲</e:mo><e:mi>z</e:mi><e:mo>≲</e:mo><e:mn>0.6</e:mn></e:math>, <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>0.6</g:mn><g:mo>≲</g:mo><g:mi>z</g:mi><g:mo>≲</g:mo><g:mn>0.8</g:mn></g:math>. We adopt a scale cut where nonlinear effects are negligible, so that the cosmological constraints are derived from the linear regime. We determine the amplitude of matter fluctuations over all three redshift bins using Atacama Cosmology Telescope (ACT) data alone to be <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msub><i:mi>S</i:mi><i:mn>8</i:mn></i:msub><i:mo>≡</i:mo><i:msub><i:mi>σ</i:mi><i:mn>8</i:mn></i:msub><i:mo stretchy="false">(</i:mo><i:msub><i:mi mathvariant="normal">Ω</i:mi><i:mi>m</i:mi></i:msub><i:mo>/</i:mo><i:mn>0.3</i:mn><i:msup><i:mo stretchy="false">)</i:mo><i:mn>0.5</i:mn></i:msup><i:mo>=</i:mo><i:mn>0.772</i:mn><i:mo>±</i:mo><i:mn>0.040</i:mn></i:math> in a joint analysis combining the three redshift bins and ACT lensing alone. Using a combination of ACT and data we obtain <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:msub><n:mi>S</n:mi><n:mn>8</n:mn></n:msub><n:mo>=</n:mo><n:mn>0.765</n:mn><n:mo>±</n:mo><n:mn>0.032</n:mn></n:math>. The lowest redshift bin used is the least constraining and exhibits a <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"><p:mo>∼</p:mo><p:mn>2</p:mn><p:mi>σ</p:mi></p:math> tension with the other redshift bins; thus we also report constraints excluding the first redshift bin, giving <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"><r:msub><r:mi>S</r:mi><r:mn>8</r:mn></r:msub><r:mo>=</r:mo><r:mn>0.785</r:mn><r:mo>±</r:mo><r:mn>0.033</r:mn></r:math> for the combination of ACT and . This result is in excellent agreement at the <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:mn>0.3</t:mn><t:mi>σ</t:mi></t:math> level with measurements from galaxy lensing, but is <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mn>1.8</v:mn><v:mi>σ</v:mi></v:math> lower than predictions based on primary CMB data. Understanding whether this hint of discrepancy in the growth of structure at low redshifts arises from a fluctuation, from systematics in data, or from new physics is a high priority for forthcoming CMB lensing and galaxy cross-correlation analyses.
CMB lensing and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Ly</mml:mi><mml:mi>α</mml:mi></mml:math> forest cross bispectrum from DESI’s first-year quasar sample
(American Physical Society, 2024) Naim Göksel Karaçaylı; Paul Martini; David H. Weinberg; Simone Ferraro; Roger de Belsunce; J. Aguilar; S. P. Ahlen; E. Armengaud; D. Brooks; T. Claybaugh
The squeezed cross-bispectrum ${B}_{\ensuremath{\kappa},\mathrm{Ly}\ensuremath{\alpha}}$ between the gravitational lensing in the cosmic microwave background and the 1D $\mathrm{Ly}\ensuremath{\alpha}$ forest power spectrum can constrain bias parameters and break degeneracies between ${\ensuremath{\sigma}}_{8}$ and other cosmological parameters. We detect ${B}_{\ensuremath{\kappa},\mathrm{Ly}\ensuremath{\alpha}}$ with $4.8\ensuremath{\sigma}$ significance at an effective redshift ${z}_{\mathrm{eff}}=2.4$ using Planck PR3 lensing map and over 280,000 quasar spectra from the Dark Energy Spectroscopic Instrument's first-year data. We test our measurement against metal contamination and foregrounds such as Galactic extinction and clusters of galaxies by deprojecting the thermal Sunyaev-Zeldovich effect. We compare our results to a tree-level perturbation theory calculation and find reasonable agreement between the model and measurement.
Early time solution as an alternative to the late time evolving dark energy with DESI DR2 BAO
(American Physical Society, 2025) E. Chaussidon; Martin White; Arnaud de Mattia; Rafaela Gsponer; S. P. Ahlen; Davide Bianchi; D. Brooks; T. Claybaugh; S. Cole; A. Cuceu
Supplementary material to DESI's publication 'Early time solution as an alternative to the late time evolving dark energy with DESI DR2 BAO' to comply with the data management plan.
Evidence for large baryonic feedback at low and intermediate redshifts from kinematic Sunyaev-Zel’dovich observations with ACT and DESI photometric galaxies
(American Physical Society, 2025) Boryana Hadzhiyska; Simone Ferraro; Bernardita Ried Guachalla; Emmanuel Schaan; José Aguilar; S. P. Ahlen; Nicholas Battaglia; J. Richard Bond; D. Brooks; E. Calabrese
Recent advances in cosmological observations have provided an unprecedented opportunity to investigate the distribution of baryons relative to the underlying matter. In this work, we show that the gas is more extended than the dark matter, and the amount of baryonic feedback at $z\ensuremath{\lesssim}1$ disfavors low-feedback models such as that of state-of-the-art hydrodynamical simulation IllustrisTNG compared with high-feedback models such as that of the original Illustris simulation. This has important implications for bridging the gap between theory and observations and understanding galaxy formation and evolution. Furthermore, a better grasp of the baryon-dark matter link is critical to future cosmological analyses, which are currently impeded by our limited knowledge of baryonic feedback. Here, we measure the kinematic Sunyaev-Zel'dovich (kSZ) effect from the Atacama Cosmology Telescope, stacked on the luminous red galaxy sample of the Dark Energy Spectroscopic Instrument (DESI) imaging survey. This is the first analysis to use photometric redshifts for reconstructing galaxy velocities. Due to the large number of galaxies comprising the DESI imaging survey, this is the highest signal-to-noise stacked kSZ measurement to date; we detect the signal at $13\ensuremath{\sigma}$, finding strong evidence that the gas is more spread out than the dark matter, as well as a preference for larger feedback compared to some commonly used state-of-the-art hydrodynamical simulations. Our work opens up the possibility of recalibrating large hydrodynamical simulations using the kSZ effect. In addition, our findings highlight the importance of properly accounting for baryonic feedback with future surveys such as LSST through direct probes such as the kSZ, and shed light on long-standing enigmas in astrophysics, such as the ``missing baryon'' problem.
Study of the connected four-point correlation function of galaxies from the DESI Data Release 1 luminous red galaxy sample
(American Physical Society, 2025) J. Hou; R. N. Cahn; J. Aguilar; S. Ahlen; D. Bianchi; D. Brooks; T. Claybaugh; P. Doel; S. Ferraro; J. E. Forero-Romero
We present a measurement of the non-Gaussian four-point correlation function (4PCF) from the DESI DR1 luminous red galaxy (LRG) sample. For the gravitationally induced parity-even 4PCF, we detect a signal with a significance of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mn>14.7</a:mn> <a:mi>σ</a:mi> </a:mrow> </a:math> using our fiducial setup. We assess the robustness of this detection through a series of validation tests, including auto and cross-correlation analyses, sky partitioning across multiple patch combinations, and variations in radial scale cuts. Due to the low completeness of the sample, we find that differences in fiber assignment implementation schemes can significantly impact estimation of the covariance and introduce biases in the data vector. After correcting for these effects, all tests yield consistent results. This is one of the first measurements of the connected 4PCF on the DESI LRG sample; the good agreement between the simulation and the data implies that the amplitude of the density fluctuation inferred from the connected 4PCF is consistent with the Planck <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi mathvariant="normal">Λ</c:mi> <c:mi>CDM</c:mi> </c:math> cosmology. The methodology and diagnostic framework established in this work provide a foundation for interpreting parity-odd 4PCF.