arXiv subjects

A. Carnero Rosell

Publications and source records attributed to A. Carnero Rosell.

At least 19 recordsLinked to original sources

arXiv2026

DESI DR2 Results III: The Mass of the Milky Way

We present measurements of the mass of the Milky Way using distant halo stars selected from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2). We apply four dynamical modeling methods to 10,036 RR Lyrae (RRL) and blue horizontal branch (BHB) stars with 6D phase space coordinates that span from $\sim$10 to 95 kpc from the Galactic center, the largest samples of their kind. All methods are applied to mock surveys based on cosmological simulations that include generating individual tracer stars, convolving their phase-space coordinates with DESI and Gaia DR3-like uncertainties, and tailored models of the survey selection functions. By comparing the performance on these mocks, we quantify how systematic biases from both methodology assumptions and galaxy disequilibrium impact each estimate. The mock-based systematics, which differ by method and tracer, are used to correct the individual estimates and to derive joint estimates using a rigorous formalism that accounts for per-method biases and residual correlations between methods. We obtain a joint estimate of the mass within 80 kpc to be $M(r < 80 \mathrm{\,kpc}) = 6.36^{+0.53}_{-0.48} \times 10^{11}$ M$_\odot$ and a virial mass estimate of $M_\mathrm{200c} = 1.19^{+0.14}_{-0.12} \times 10^{12}$ M$_\odot$, with similar results when combining only RRL-based or BHB-based measurements. These results provide a roadmap for future DESI efforts, as well as those in other spectroscopic surveys, to reliably constrain the mass of our Galaxy.

astro-ph.GA↗

arXiv2026

Mock catalogues for the DESI DR2 Milky Way mass modeling effort

The Dark Energy Spectroscopic Instrument (DESI) survey is an ongoing campaign to obtain millions of spectra, including for stars within the Milky Way. One of DESI's Key Projects for its second data release (DR2) is to measure the mass of the Milky Way using a variety of techniques applied to six-dimensional kinematics of distant halo stars. We present mock surveys generated from the Auriga cosmological simulations (AuriDESI) that are used to validate these techniques in several companion studies. The AuriDESI tracer catalogues are tailored to reflect key features of the DR2 Key Project dataset, including the selection of RR Lyrae and blue horizontal branch stars, uncertainties on line-of-sight velocities and proper motions, and variation in observational completeness within the survey footprint. We discuss how well the resulting AuriDESI tracer catalogues compare to their observed DESI counterparts, including suggesting improvements that can be generalized to similar mock survey efforts within the community. The AuriDESI tracer catalogues are publicly available on Zenodo.

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arXiv2026

Constraining the Milky Way Mass profile with data driven distribution function using DESI DR2 halo stars

We employ a novel data-driven dynamical modeling method, the empirical distribution function (emPDF), to constrain the Milky Way mass profile using a large sample of halo stars from the Dark Energy Spectroscopic Instrument Milky Way Survey (DESI MWS). The method does not assume any functional form of the tracer distribution. Deviations from the steady-state assumption and the effects of observational errors are further tested and calibrated using a number of realistic mock observations (AuriDESI). Applying the calibrated method to two classes of tracers in DESI, we derive a best-constrained virial mass and concentration of $\log M_\mathrm{200c}/M_{\odot}=12.05_{-0.12}^{+0.21}(_{-0.18}^{+0.26})$ and $\log c_\mathrm{200c}=1.20_{-0.16}^{+0.11}(_{-0.24}^{+0.20})$ for BHBs. For RR Lyrae stars we derive $\log M_\mathrm{200c}/M_{\odot}=12.15_{-0.14}^{+0.22}(_{-0.19}^{+0.26})$ and $\log c_\mathrm{200c}=1.16_{-0.12}^{+0.09}(_{-0.18}^{+0.16})$. The uncertainties quoted outside and within brackets are statistical and total errors including systematic errors calibrated from AuriDESI, respectively. The two tracer populations provide overall consistent measurements of the MW halo mass profile. Combining the halo star constraints with the independent constraint from satellite dynamics, we derive a robust and precise final measurement of the MW halo parameters of $\log M_\mathrm{200c}/M_{\odot}=12.12_{-0.05}^{+0.05}(_{-0.04}^{+0.06})$ and $\log c_\mathrm{200c}=1.16_{-0.03}^{+0.05}(_{-0.07}^{+0.05})$, with correlation coefficients of $ρ=-0.90(-0.54)$.

astro-ph.GA↗

arXiv2026

A distribution-function estimate of the Milky Way mass profile from outer halo stars in DESI DR2

We present measurements of the Milky Way mass using blue horizontal-branch (BHB) and RR Lyrae (RRL) stars from the second data release of DESI (DR2), covering its first three years of operations. We employ 279 BHBs and 213 RRLs at $\sim\!50$--$80$\,kpc from the Galactic center, selected from catalogs roughly twice as large as those of DESI DR1, used in our previous mass measurement. We apply the Galactic Mass Estimator (GME), a hierarchical Bayesian framework that assumes power-law forms for the potential and the tracer density, and accounts for distance and velocity uncertainties. Validating the method on 24 AuriDESI mock catalogs (six Auriga halos at four viewing angles), we find that it overestimates the enclosed mass by $\sim\!15\%$ at 80\,kpc, and correct our results accordingly. We obtain $M(<80\,{\rm kpc}) = 0.64^{+0.06}_{-0.06}$ and $0.53^{+0.05}_{-0.05} \times 10^{12}\,M_\odot$ for BHBs and RRLs, respectively, while including Sagittarius stream stars lowers these masses by $\sim\!10$\%. Extrapolating to 100\,kpc, we obtain $M(<100\,{\rm kpc}) = 0.74^{+0.07}_{-0.07}$ and $0.62^{+0.06}_{-0.07} \times 10^{12}\,M_\odot$, and anchoring an NFW halo to our GME constraints at 65\,kpc yields virial masses of $M_{200} = 1.12^{+0.14}_{-0.12}$ and $0.89^{+0.11}_{-0.10} \times 10^{12}\,M_\odot$. BHBs yield systematically higher masses than RRLs across the full radial range, reflecting the impact of tracer choice even within a single method. This work is part of a wider DESI DR2 Key Project effort to measure the Milky Way mass and constrain systematics arising from different samples and methodologies.

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arXiv2026

A multiprobe $Λ$CDM consistency analysis with gravitational-wave standard sirens

Multi-messenger cosmology offers an independent path to stress-test the $Λ$CDM model as gravitational wave (GW) catalogs grow in size. We present the first multiprobe assessment of $Λ$CDM tensions incorporating GW standard sirens: LIGO-Virgo-KAGRA Collaboration (LVK) fifth Gravitational-Wave Transient Catalog (GWTC-5.0) standard sirens are combined with Dark Energy Survey (DES) Year 6 weak lensing and galaxy clustering (3$\times$2pt), baryon acoustic oscillations (BAO), and type Ia supernovae (SNe Ia), together with Dark Energy Spectroscopic Instrument (DESI) BAO, and confronted with primary cosmic microwave background (CMB) measurements from Planck, the Atacama Cosmology Telescope (ACT), and the South Pole Telescope (SPT). All probes are analyzed under homogeneous priors and combined via normalizing flows, and we quantify the $S_8$ discrepancy and $H_0$ tension with respect to CMB. Adding standard sirens to the 3$\times$2pt analysis improves the constraints in the $Ω_m$-$S_8$ plane by $\sim$30%, while constraining $H_0$ to 6.2%. We present cosmological constraints from the low-redshift probes including standard sirens, yielding $S_8 = 0.793 \pm 0.010$, $Ω_m = 0.308^{+0.007}_{-0.006}$, and $H_0 = 69.4^{+4.1}_{-4.4}$ km s$^{-1}$ Mpc$^{-1}$. At current GW sensitivity, however, both the $S_8$ discrepancy and the $H_0$ tension remain essentially unchanged. Our analysis nonetheless delivers the first assessment of $Λ$CDM tensions computed with standard sirens included among the probes, and establishes them as a mature cosmological probe -- ready to be combined on equal footing with established datasets in forthcoming surveys such as the Legacy Survey of Space and Time (LSST), Euclid, and Roman.

astro-ph.CO↗

arXiv2026

Improved constraints on the Milky Way potential using the M68 stream and DESI spectroscopic data

We present a selection of stars belonging to the stellar stream of the M68 (NGC 4590) globular cluster, also known as Fjörm. This star selection is an improvement on previous ones that used only Gaia data, as it incorporates spectroscopic measurements from the DESI survey and photometric data from the DESI Legacy Surveys. The selection contains 96 stars, each with five phase-space parameters from Gaia-DR3 and radial velocity from DESI, covering the entire observed section of the stream. This constitutes the largest selection of M68 stream stars with measured radial velocities to date. The observed stream is wider than expected from N-body simulations, and the stars farthest from the centre of the stream appear to be correlated in radial velocity space. This suggests that these stars cannot have been stripped from the cluster in a static axisymmetric potential. By modelling a mock sample of stream stars created using an N-body simulation, we found that we could reliably constrain the disc mass $M_{\rm d}$ and the dark matter halo axis ratio $q_{\rm h}$ of the Milky Way. This is because the stream flows close to and almost parallel to the disc. Using the 44 stars that are consistent with having been stripped from the cluster, combined with measurements of the Milky Way's rotation curve, we constrain the Galactic potential, obtaining $M_{\rm d} = 5.34 \pm 0.57 \times 10^{10}$ M$_{\rm sun}$ and an oblate halo of $q_{\rm h} = 0.83^{+0.06}_{-0.05}$. Additionally, by fitting the stream track, we estimate the Heliocentric distance of M68 to be $r=10.55\pm0.09$ kpc.

astro-ph.GA↗

arXiv2026

The scale of homogeneity in DESI Data Release 1

We present measurements of the scale of cosmic homogeneity using the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI), the largest publicly available spectroscopic extragalactic survey to date. Using a counts-in-spheres estimator applied to nearly 5 million galaxies and quasars across six independent redshift bins spanning $0.1 < z < 2.1$, we measure the correlation dimension $D_2(r)$ and define the homogeneity scale $R_H$ as the point at which the galaxy distribution reaches within 1\% of the homogeneous asymptotic value. We find that all tracers clearly transition to homogeneity, with the galaxy homogeneity scale ranging from $93.8^{+0.9}_{-0.7}$ to $142.6^{+1.4}_{-1.4}$ $h^{-1}$Mpc depending on the tracer redshift, galaxy bias, and modelling used to extract the scale. Using a cosmology-dependent model, we reconstruct the underlying matter homogeneity scale, finding it decreases monotonically with redshift in excellent agreement with $Λ$CDM predictions. We identify a systematic offset of up to $\sim 10\%$ between measurements in the North and South Galactic Caps, largely due to fiber assignment effects reproduced in our simulations. Accounting for this, and with a complementary demonstration using toy models that our methodology correctly identifies inhomogeneous universes in all but rather finely-tuned observer configurations, this hence provides strong evidence in favour of the cosmological principle across our full redshift range. Our matter homogeneity scale measurements are consistent with, and substantially more precise than, previous constraints from WiggleZ and SDSS, demonstrating the power of DESI data for precision tests of the cosmological principle.

astro-ph.CO↗

arXiv2026

Dark Energy Survey Year 6 Results: improved mitigation of spatially varying observational systematics with masking for the MagLim++ lens sample

As photometric surveys reach unprecedented statistical precision, systematic uncertainties increasingly dominate large-scale structure probes relying on galaxy number density. Defining the final survey footprint is critical, as it excludes regions affected by artefacts or suboptimal observing conditions. For galaxy clustering, spatially varying observational systematics, such as seeing, are a leading source of bias. Template maps of contaminants are used to derive spatially dependent corrections, but extreme values may fall outside the applicability range of mitigation methods, compromising correction reliability. The complexity and accuracy of systematics modelling depend on footprint conservativeness, with aggressive masking enabling simpler, robust mitigation. We present a unified approach to define the DES Y6 JOINT footprint, integrating observational systematics templates and artefact indicators that degrade mitigation performance. This removes extreme values from an initial SEED footprint, leading to the final JOINT footprint. By evaluating the DES Y6 lens sample MagLim++ on this footprint, we enhance the Iterative Systematics Decontamination (ISD) method, detecting non-linear systematic contamination and improving correction accuracy. While the mask's impact on clustering is less significant than systematics decontamination, it remains non-negligible, comparable to statistical uncertainties in certain w(theta) scales and redshift bins. Supporting coherent analyses of galaxy clustering and cosmic shear, the final footprint spans 4,031.04 deg2, setting the basis for DES Y6 1x2pt, 2x2pt, and 3x2pt analyses. This work highlights how targeted masking strategies optimise the balance between statistical power and systematic control in Stage-III and -IV surveys.

astro-ph.CO↗

arXiv2026

Self Calibrated Galaxy Groups from the DESI DR1 Bright Galaxy Survey

We present a galaxy group catalog built from Data Release 1 of the Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey, using the Self Calibrated Group Finder. The algorithm uses clustering data from the observed sample to calibrate the Group Finder's free parameters, rather than simulations. The catalog contains 2,229,741 galaxies from ~$2680$ deg$^2$ of sky with 3-pass coverage and $r$-band fluxes $\lt 19.5$. The catalog classifies all galaxies in the flux-limited sample as centrals or satellites and estimates host dark matter halo masses. We show the satellite fraction $f_{\rm sat}$, luminosity halo mass relation, stellar halo mass relation and halo occupation distributions (HODs) from the catalog. We find these non-parametric HODs can be fit by standard HOD models, with satellite power-law index $α$ values around 0.75 for star-forming galaxies and around 1.1 for quiescent objects. In agreement with recent results, we find that the quenched fraction of central galaxies depends mostly on halo mass and is nearly independent of central galaxy stellar mass for galaxies more massive than $10^{10.3}$ $M_\odot h^{-1}$ and halos more massive than $10^{12.2}$ $M_\odot h^{-1}$. In an appendix, we introduce a new Hybrid Nearest Neighbor (HNN) technique to mitigate systematics from fiber incompleteness. HNN uses photometric redshifts and multiple on-sky neighbors to assign redshifts to unobserved targets. Calibrated on DESI Survey Validation 3 data, our technique yields correct redshifts $\sim 50\%$ of the time and produces unbiased halo occupation statistics.

astro-ph.GA↗

arXiv2026

A census of Dark Energy Survey Year 3 redMaPPer galaxy clusters in a high exposure eROSITA All Sky Survey region

We present the cross-match of galaxy clusters detected by redMaPPer using the first three years of Dark Energy Survey (DESY3RM) operations, and the first release of the eROSITA-All Sky Survey (eRASS1) taken by eROSITA on board the Spectrum Roentgen Gamma telescope. We define a sky region ($60^{\circ}<{\rm R.A.}<90^{\circ}$ and $-58^{\circ}<{\rm Dec}<-48^{\circ}$) whereby the mean eRASS1 exposure time of clusters falling within this footprint is $\sim$2.5 times longer than the mean exposure time of the full eRASS1--DESY3RM overlap. Limiting to a redshift range $0.2 < z < 0.65$ and redMaPPer estimated richnesses to $>$50, we obtain a sample of 57 clusters. We match these clusters to the cluster catalogue constructed for the eRASS1, finding 45 clusters with a match and 12 with no match in the catalogue. X-ray properties of the 12 unmatched clusters are estimated via a forced photometry analysis. We investigate the form of the luminosity-richness relation, finding the relation using the full 57 cluster sample is statistically consistent with using only the 45 matched clusters, and will require the deeper data of future eRASS releases (or dedicated X-ray follow-up) to explore further potential differences. Using external data from XMM, ACT and SPT, we find detections of 5 of the 12 unmatched clusters, indicating the presence of virialised gas. Finally, we found the 12 unmatched clusters occupy a higher redshift range and lower richness range (compared to the matched clusters), and find no evidence for an underlying physical reason for the lack of X-ray emission.

astro-ph.CO↗

arXiv2026

Optical Depths from the Thermal Sunyaev-Zel'dovich Effect with ACT DR6 and DESI DR1 Spectroscopic Galaxies and Optically-Selected Clusters

We present stacked thermal Sunyaev-Zel'dovich (tSZ) effect measurements for three samples of galaxy groups and clusters: those traced by the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) luminous red galaxies (LRG) and the DESI DR1 Bright Galaxy Sample (BGS), and an eROMaPPer optically-selected sample from the DESI Legacy Imaging Survey. We use the latest Atacama Cosmology Telescope DR6 (ACT)+Planck component-separated internal linear combination (ILC) Compton-$y$ maps and ACT+Planck coadded 90, 150, and 220 GHz temperature maps to extract the tSZ signal within a $\sim2'$ disk aperture for sources binned by luminosity, richness, or mass. We measure the average tSZ signal with high statistical significance, with signal-to-noise ratios surpassing 38 for LRG, 27 for BGS, and 39 for the eROMaPPer sample using the 90 GHz ACT DR6+Planck map. We conduct a detailed study of systematics and foregrounds such as dust and cosmic infrared background (CIB) contamination, which remain a core challenge for tSZ analysis. For the LRG and BGS samples, we find that dust and radio source emission dominate the tSZ signal at scales near and below the disk aperture radius. Large-scale ($R>4'$) contamination from the CIB is less significant. We mitigate these contaminants to isolate the tSZ signal and use a combination of simulated and real measurements to develop Compton-$y-$optical depth ($\bar y-\bar τ$) scaling relations to infer optical depths, which are found to be in agreement with values measured using the pairwise kinematic SZ effect for the same tracer samples. The $\bar y-\bar τ$ scaling relation for the eROMaPPer sample is the first such relationship to be derived directly from SZ measurements.

astro-ph.CO↗

arXiv2026

Dark Energy Survey Year 6 Results: fast and interpretable posterior predictive checks for correlated cosmic probes

We present a fast and numerically stable framework for conducting posterior predictive distribution (PPD) tests of internal consistency in correlated cosmological probes. Our method, developed as a validation check for the Dark Energy Survey (DES) Year 6 combined analysis of weak lensing and galaxy clustering, employs a Gaussian-mixture model to efficiently approximate the high-dimensional PPD and introduces a scalar consistency metric, $Δ_{\rm PPD}$, defined as the fraction of the PPD at lower probability density than the observed data. This method avoids challenges related to calibration and numerical stability that impacted PPD methods previously used in DES Year 3. After demonstrating performance with a toy model, we confirm that when applied to DES Year 3 measurements, $Δ_{\rm PPD}$ identifies the same inter-probe tensions as published, calibrated PPD results while requiring only minutes per test. We further validate the method on several noise realizations of simulated DES Y6 analyses, demonstrating that $Δ_{\rm PPD}$ responds coherently to injected inconsistency, while highlighting two effects which can complicate the interpretation of PPD tests for increasingly complex models. First, internal tensions that can be absorbed as shifts in nuisance parameters become more difficult to detect. Second, poorly constrained directions in parameter space can induce projection effects in PPDs for disjoint sets of observables, producing reports of tension even for consistent data. We conclude that $Δ_{\rm PPD}$ provides a practical PPD-based diagnostic for multiprobe unblinding, to be interpreted with care alongside other validation checks. This framework has already played an important role in DES analyses and is well suited for application to forthcoming Stage-IV surveys such as LSST, Euclid, and Roman, where fast, robust internal consistency tests will be essential.

astro-ph.CO↗

arXiv2026

Dark Energy Survey Year 6 Results: Galaxy-galaxy lensing

We present galaxy--galaxy lensing (GGL) measurements from the full six years of data from the Dark Energy Survey (DES Y6), covering $4031\,\mathrm{deg}^2$ and used in the DES Y6 $3\times2$pt cosmological analysis. We use the MagLim++ lens sample, containing $\sim 9$ million galaxies divided into six redshift bins, and the Metadetection source catalog, including $\sim 140$ million galaxies divided into four redshift bins. The mean tangential shear signal achieves a total signal-to-noise ratio (S/N) of $173$, corresponding to a $17\%$ improvement over DES Y3. After applying the scale cuts used in the cosmological analysis, with $R_{\min}=6\,\mathrm{Mpc}/h$ ($4\,\mathrm{Mpc}/h$) for the linear (nonlinear) galaxy-bias model, the S/N is reduced to $75$ (90). A comprehensive suite of validation tests demonstrates that the measurement is robust against observational and astrophysical systematics at the statistical precision required for the DES Y6 analysis. Although not used in the main cosmological analysis, we extract high--signal-to-noise geometric shear-ratio measurements from the galaxy--galaxy lensing signal on small angular scales. These measurements provide an internal consistency check on the photometric redshift distributions and shear calibration used in the $3\times2$pt analysis.

astro-ph.CO↗

arXiv2026

Dark Energy Survey Year 6 Results: Redshift Calibration of the MagLim++ Lens Sample

In this work, we derive and calibrate the redshift distribution of the MagLim++ lens galaxy sample used in the Dark Energy Survey Year 6 (DES Y6) 3x2pt cosmology analysis. The 3x2pt analysis combines galaxy clustering from the lens galaxy sample and weak gravitational lensing. The redshift distributions are inferred using the SOMPZ method - a Self-Organizing Map framework that combines deep-field multi-band photometry, wide-field data, and a synthetic source injection (Balrog) catalog. Key improvements over the DES Year 3 (Y3) calibration include a noise-weighted SOM metric, an expanded Balrog catalogue, and an improved scheme for propagating systematic uncertainties, which allows us to generate O($10^8$) redshift realizations that collectively span the dominant sources of uncertainty. These realizations are then combined with independent clustering-redshift measurements via importance sampling. The resulting calibration achieves typical uncertainties on the mean redshift of 1-2%, corresponding to a 20-30% average reduction relative to DES Y3. We compress the $n(z)$ uncertainties into a small number of orthogonal modes for use in cosmological inference. Marginalizing over these modes leads to only a minor degradation in cosmological constraints. This analysis establishes the MagLim++ sample as a robust lens sample for precision cosmology with DES Y6 and provides a scalable framework for future surveys.

astro-ph.CO↗

arXiv2026

Probing Baryons with the Kinematic Sunyae Zel'dovich Effect and Machine Learning Derived Peculiar Velocities using DESI DR2 and ACT DR6

We present novel empirical constraints on average optical depths and gas density profiles from combining kinematic Sunyaev Zel'dovich effect (kSZ) measurements and nonlinear peculiar velocities, reconstructed using machine learning, for massive halos traced by DESI DR2 luminous red galaxies (LRG). The pairwise kSZ is measured using two ACT DR6 cosmic microwave background (CMB) temperature maps (ILC and 150 GHz maps) for seven luminosity-selected LRG samples. We find consistent results between the two maps and significant detections across the samples. We reconstruct LRG line-of-sight peculiar velocities in two cosmic epochs, centered on $z=$ 0.55 and 0.8, using a simulation-trained Transformer machine learning model to extend beyond the linear approximation. Average optical depths are inferred by comparing the kSZ pairwise correlation to the measured pairwise velocity correlation from the reconstructed velocity field and, separately, from a theoretical prediction using the best fit Planck cosmology, with the highest significance reaching SNR = 14.2 and 15.1 respectively. We also obtain velocity-weighted AP-filtered kSZ-stacked cluster density profiles, which show evidence of extended ionized gas around massive LRG groups and no strong redshift evolution within current measurement uncertainties. These results demonstrate the power of combining spectroscopic galaxy and CMB data, and employing machine learning methods, to probe diffuse baryons and coherent large-scale velocity fields. They open up new avenues to leverage upcoming galaxy survey data from Euclid, Roman and Rubin LSST, in tandem with multi-frequency CMB/sub-mm data from CCAT and Simons Observatory.

astro-ph.CO↗

arXiv2026

Intrinsic Tidal Shear at the Largest Scales: Galaxy Multiplet Alignment in DESI DR2

We measure the intrinsic alignment (IA) of galaxy multiplets with the large-scale tidal field traced by galaxy positions in DESI Data Release 2. Using the BGS, LRG, and ELG samples spanning $0.01 < z < 1.6$, we optimize the scales which define multiplets in each sample to minimize measurement noise. We measure multiplet tidal alignment $\mathcal{E}_+$ on scales beyond 100 $h^{-1}$Mpc in all samples, and detect alignment over 200 $h^{-1}$Mpc, up to 4.5$σ$ in the highest LRG redshift bin. We additionally present the multiplet shape-shape autocorrelation, $\mathcal{E}_{++}$, which is independent of galaxy bias and provides a consistency check of our NLA (nonlinear alignment) model. We do not detect a baryon acoustic feature in the projected estimator. We also find the alignment strength of multiplets is correlated with redshift and galaxy morphology. Multiplet alignment offers direct access to the tidal shear field in all galaxy samples, even where individual galaxy alignment cannot, and extends IA detection to the largest scales yet probed.

astro-ph.CO↗

arXiv2026

Dark Energy Survey Year 6 Results: Weak Lensing and Galaxy Clustering Cosmological Analysis Framework

We present the methodology for the weak lensing and galaxy clustering analyses of the Dark Energy Survey (DES) Year 6 data set. In this work, we design and validate the analysis pipeline for the cosmic shear, galaxy clustering plus galaxy$-$galaxy lensing ($2 \times 2$pt), and the joint analysis in the $3 \times 2$pt. Our framework accounts for key theoretical uncertainties, such as baryonic feedback and galaxy bias, incorporating both linear and non-linear models. We apply scale cuts in regimes where theoretical modeling becomes unreliable. The robustness of the pipeline is validated using mock data and simulations, confirming unbiased cosmological constraints and highlighting the importance of posterior projection effects in the validation process. As a result, we deliver robust and validated analysis pipelines for cosmic shear, $2 \times 2$pt, and $3 \times 2$pt in $Λ$CDM and $w$CDM scenarios, including a well-defined set of scales suitable for real data analysis, a robust prescription for theoretical systematics, and the theoretical covariance of the signal. This comprehensive methodology also lays the groundwork for future galaxy surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time.

astro-ph.CO↗

arXiv2026

Weak Lensing Mass Calibration of the ACT DR5 Galaxy Clusters with the DES Year 3 Weak Lensing Data

We use weak gravitational lensing measurements from Year 3 Dark Energy Survey data to calibrate the masses of 443 galaxy clusters selected via the Sunyaev-Zel'dovich effect from Atacama Cosmology Telescope Data Release 5 maps. We incorporate redshift and SZ measurements for individual clusters into a hierarchical model for the stacked lensing signals and perform Bayesian analyses to constrain hydrostatic mass bias of the clusters. Our treatment of systematic uncertainties includes a prescription for measuring and accounting for the weak lensing boost factor, consideration of a miscentering effect, as well as marginalization over uncertainties in the source galaxy photometric redshift distributions and shear calibration. The constraints on the normalization of the mass-observable relation have a precision of 7%, with the mean WL halo mass $M_{\rm 500c} = 5.4 \times 10^{14} M_{\odot}$. We measure the bias between the true cluster mass and the mass estimated from the SZ signal assuming hydrostatic equilibrium, to be $1-b = 0.74^{+0.06}{-0.05}$ over the full sample. When splitting the clusters into high and low redshift bins, we measure $1-b = 0.58^{+0.06}{-0.05}$ and $0.81^{+0.08}{-0.06}$, respectively. When introducing additional freedom in redshift and mass to the hydrostatic bias model, we find that $1-b$ decreases with redshift (with the power law of $-1.8^{+0.5}{-0.6}$, 99.95% confidence), consistent with findings from other recent studies, while we do not find any significant trend in mass. We also demonstrate that our result is robust against various systematics such as a scale cut, priors on baryonic and miscentering parameters, and degree of scatter in mass-observable relation. The weak-lensing mass calibration presented in this study will be a useful tool for using the ACT clusters as probes of astrophysics, and as a step towards using their abundance as a cosmological probe.

astro-ph.CO↗