Year: 2026
Type: preprint
Abstract: We present a data-driven measurement of galaxy bias and scale-dependent relative bias for elliptical and spiral galaxies using angular auto- and cross-power spectra from DES and DESI Legacy Imaging Surveys DR8. We introduce the cross-tracer clustering ratio (CTCR), the ratio of auto- to cross-power spectra, which isolates the relative clustering of morphological tracers as a function of angular multipole $\ell$. Across both surveys, ellipticals are more strongly clustered than spirals; the cleanest constraints come from DESI, where the two redshift distributions are well matched. The difference is scale dependent: the relative bias is near unity on large scales ($\ell \lesssim 50$) and rises toward smaller scales, reaching $2.9$--$4.0σ$ per bin at $\ell = 200$ with an inverse-variance-weighted amplitude $Δb = +0.56 \pm 0.06$. A complementary linear-bias analysis confirms that ellipticals are positively biased relative to the matter field, while spirals are consistent with weak bias or anti-bias. The results are robust to two covariance estimators, contamination tests, luminosity splits, and comparisons with two N-body mock catalogs. Throughout, we present the CTCR as an \emph{effective} clustering ratio that is an upper bound on the physical bias ratio, adopting an assumption-light strategy appropriate for a first measurement; the joint multi-spectrum decomposition required to extract the physical bias ratio is identified as future work. These findings provide empirical evidence that galaxy morphology imprints both the amplitude and scale dependence of galaxy bias, and establish the CTCR as a useful observable for testing halo occupation and assembly-bias models with future imaging surveys.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, University of Pennsylvania, Ohio State University, University of Chicago, University of Portsmouth, University College London, University of Sussex, Deutsche Forschungsgemeinschaft, Generalitat de Catalunya, Ministério da Ciência, Tecnologia e Inovação, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Financiadora de Estudos e Projetos, Zhejiang University, Institut de Física d'Altes Energies, University of Illinois at Urbana-Champaign, Science and Technology Facilities Council, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Agencia Estatal de Investigación, National Key Research and Development Program of China, Integrated Electronics Engineering Center, Binghamton University, Argonne National Laboratory, Fermilab, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory
Awards: G1175115578, G1272927172, G1275292511, G2064873908, G2262748287, G2469010403, G2756433129, G2988934680, G3005324705, G300979063, G3418218065, G34346518, G3452655474, G3480869486, G3546882995, G425668148, G4526231891, G4728539003, G5080475149, G5180915604, G5608897973, G5779771523, G5826275554, G5922099756, G6027777510, G69051668, G7084143925, G7391010604, G7496233463, G863151887, G8836406373
OpenAlex ID: W7169766085