Browsing by Autor "J. E. Forero-Romero"

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Cosmic web classification through stochastic topological ranking
(Oxford University Press, 2025) J. E. Forero-Romero; Alejandro Palomino; Felipe Leonardo Gómez-Cortés; Xiao-Dong Li
ABSTRACT This paper introduces ASTRA (Algorithm for Stochastic Topological RAnking), a new method for classifying galaxies into cosmic web structures – voids, sheets, filaments, and knots – specifically designed for large spectroscopic surveys. ASTRA operates on observed galaxy positions and a corresponding random catalogue, generating probabilistic cosmic web classifications for both data sets. The method’s key innovation lies in using random points to trace underdense regions, enabling robust identification of cosmic voids that are poorly sampled by galaxies. We evaluate ASTRA using N-body simulations (dark matter-only and hydrodynamical) and SDSS observational data, performing both visual inspections and quantitative analyses of mass and volume distributions. The algorithm successfully produces void catalogues with size functions following theoretical expectations and demonstrates consistent environmental statistics across diverse data sets. Comparative analysis against established cosmic web classifiers confirms ASTRA’s effectiveness, particularly for filament identification. By incorporating both observed and random points in its classification scheme, ASTRA provides a full cosmic web characterization without requiring density field interpolation or fixed geometric assumptions. The method’s ability to quantify spatial correlations among different cosmic web components offers promising avenues for enhancing cosmological parameter constraints through non-standard clustering statistics.
Detection of the large-scale tidal field with galaxy multiplet alignment in the DESI Y1 spectroscopic survey
(Oxford University Press, 2024) C Lamman; Daniel J. Eisenstein; J. E. Forero-Romero; J. Aguilar; S. P. Ahlen; S. Bailey; D. Bianchi; David J. Brooks; T. Claybaugh; Axel de la Macorra
ABSTRACT We explore correlations between the orientations of small galaxy groups, or ‘multiplets’, and the large-scale gravitational tidal field. Using data from the Dark Energy Spectroscopic Instrument (DESI) Y1 survey, we detect the intrinsic alignment (IA) of multiplets to the galaxy-traced matter field out to separations of $100\,h^{-1}$ Mpc. Unlike traditional IA measurements of individual galaxies, this estimator is not limited by imaging of galaxy shapes and allows for direct IA detection beyond redshift $z=1$. Multiplet alignment is a form of higher order clustering, for which the scale-dependence traces the underlying tidal field and amplitude is a result of small-scale ($\lt 1h^{-1}$ Mpc) dynamics. Within samples of bright galaxies, luminous red galaxies (LRG) and emission-line galaxies, we find similar scale-dependence regardless of intrinsic luminosity or colour. This is promising for measuring tidal alignment in galaxy samples that typically display no IA. DESI’s LRG mock galaxy catalogues created from the A bacusS ummitN-body simulations produce a similar alignment signal, though with a 33 per cent lower amplitude at all scales. An analytic model using a non-linear power spectrum (NLA) only matches the signal down to 20 $h^{-1}$ Mpc. Our detection demonstrates that galaxy clustering in the non-linear regime of structure formation preserves an interpretable memory of the large-scale tidal field. Multiplet alignment complements traditional two-point measurements by retaining directional information imprinted by tidal forces, and contains additional line-of-sight information compared to weak lensing. This is a more effective estimator than the alignment of individual galaxies in dense, blue, or faint galaxy samples.
Improving SDSS cosmological constraints through <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>β</mml:mi></mml:mrow></mml:math>-skeleton weighted correlation functions
(American Physical Society, 2024) Fenfen Yin; Jiacheng Ding; Limin Lai; Wei Zhang; Liang Xiao; Zihan Wang; J. E. Forero-Romero; Le Zhang; Xiao-Dong Li
The $\ensuremath{\beta}$-skeleton approach can be conveniently utilized to construct the cosmic web based on the spatial geometry distribution of galaxies, particularly in sparse samples. This method plays a key role in establishing the three-dimensional structure of the Universe and serves as a tool for quantitatively characterizing the nature of the cosmic web. This study is the first application of $\ensuremath{\beta}$-skeleton information as weights in mark weighted correlation functions (MCFs), presenting a novel statistical measure. We have applied the $\ensuremath{\beta}$-skeleton approach to the CMASS NGC galaxy samples from SDSS BOSS DR12 in the redshift interval $0.45\ensuremath{\le}z\ensuremath{\le}0.55$. Additionally, we applied this approach to three COLA cosmological simulations with different settings (${\mathrm{\ensuremath{\Omega}}}_{m}=0.25$, ${\mathrm{\ensuremath{\Omega}}}_{m}=0.31$, ${\mathrm{\ensuremath{\Omega}}}_{m}=0.4$) for comparison. We measured three MCFs, each weighted by (i) the number of neighboring galaxies around each galaxy, (ii) the average distance of each galaxy from its surrounding neighbors, and (iii) the reciprocal of the average distance of each galaxy from its surrounding neighbors. By comparing measurements and calculating corresponding ${\ensuremath{\chi}}^{2}$ statistics, we observe high sensitivity to the cosmological parameter ${\mathrm{\ensuremath{\Omega}}}_{m}$ through a joint analysis of the two-point correlation and three MCFs.
Spectroscopic search for optical emission lines from dark matter decay
(American Physical Society, 2024) Hanyue Wang; Daniel J. Eisenstein; J. Aguilar; S. P. Ahlen; S. Bailey; David J. Brooks; T. Claybaugh; Axel de la Macorra; Peter Doel; J. E. Forero-Romero
We search for narrow-line optical emission from dark matter decay by stacking dark-sky spectra from the Dark Energy Spectroscopic Instrument (DESI) at the redshift of nearby galaxies from DESI's Bright Galaxy and Luminous Red Galaxy samples. Our search uses regions separated by 5 to 20 arcsec from the centers of the galaxies, corresponding to an impact parameter of approximately 50 kpc. No unidentified spectral line shows up in the search, and we place a line flux limit of ${10}^{\ensuremath{-}19}\text{ }\text{ }\mathrm{ergs}/\mathrm{s}/{\mathrm{cm}}^{2}/{\mathrm{arcsec}}^{2}$ on emissions in the wavelength range of $2000--9000\stackrel{\ensuremath{\circ}}{\mathrm{A}}$. This places the tightest constraints yet on the two-photon decay of dark matter in the mass range of 5 to 12 eV, with a particle lifetime exceeding $3\ifmmode\times\else\texttimes\fi{}{10}^{25}\text{ }\text{ }\mathrm{s}$. This detection limit also implies that the line surface brightness contributed from all dark matter along the line of sight is at least 2 orders of magnitude lower than the measured extragalactic background light (EBL), ruling out the possibility that narrow optical-line emission from dark matter decay is a major source of the EBL.