Large Scale Spectrophotometric Relative Flux Calibration for the Roman High Latitude Wide Area Survey

arXiv (Cornell University) · 2026-03-25

We consider the application of a ubercalibration-like relative flux calibration to the grism observations of the Roman High Latitude Wide Area Survey (HLWAS). We propose a simplified model of the calibration with an independent flat field for each detector in each exposure of the focal plane. In addition, we include two wavelength dependent components: a single wavelength throughput curve, modulated by a simple parabolic model for the throughput as a function of a source's focal plane position. We consider the impact of the dither scale, as well as the calibrator magnitude cuts. We show that the width of the calibration residuals can be reduced to less than 1.5 mmag, or 0.15% in flux, within the optimal dither range 50-240". This wide range allows for significant flexibility in optimising other parts of the observing program without diminishing the effectiveness of the relative flux calibration. We also discuss some improvements to the methodology that must be strongly considered before the calibration can be applied to real data. Finally, although we focused on spectroscopic component of the HLWAS here, our formalism and results should carry over to the imaging surveys as well.

Extensive analysis of reconstruction algorithms for DESI 2024 baryon acoustic oscillations

Journal of Cosmology and Astroparticle Physics · 2026-05-01 · 6 citations

Abstract Reconstruction of the baryon acoustic oscillation (BAO) signal has been a standard procedure in BAO analyses over the past decade and has helped to improve the BAO parameter precision by a factor of ∼2 on average. The Dark Energy Spectroscopic Instrument (DESI) BAO analysis for the first year (DR1) data uses the “standard” reconstruction framework, in which the displacement field is estimated from the observed density field by solving the linearized continuity equation in redshift space, and galaxy and random positions are shifted in order to partially remove non-linearities. There are several approaches to solving for the displacement field in real survey data, including the multigrid (MG), iterative Fast Fourier Transform (iFFT), and iterative Fast Fourier Transform particle (iFFTP) algorithms. In this work, we analyze these algorithms and compare them with various metrics including two-point statistics and the displacement itself using realistic DESI mocks. We focus on three representative DESI samples, the emission line galaxies (ELG), quasars (QSO), and the bright galaxy sample (BGS), which cover the extreme redshifts and number densities, and potential wide-angle effects. We conclude that the MG and iFFT algorithms agree within 0.4% in post-reconstruction power spectrum on BAO scales with the RecSym convention, which does not remove large-scale redshift space distortions (RSDs), in all three tracers. The RecSym convention appears to be less sensitive to displacement errors than the RecIso convention, which attempts to remove large-scale RSDs. However, iFFTP deviates from the first two; thus, we recommend against using iFFTP without further development. In addition, we provide the optimal settings for reconstruction for five years of DESI observation. The analyses presented in this work pave the way for DESI DR1 analysis as well as future BAO analyses.

Combined tracer analysis for DESI 2024 BAO

Journal of Cosmology and Astroparticle Physics · 2026-04-01

Abstract This paper demonstrates how the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) and future baryon acoustic oscillations (BAO) analyses can optimally combine overlapping tracers (galaxies of distinct types) in the same redshift range. We make a unified catalog of Luminous Red Galaxies (LRGs) and Emission Line Galaxies (ELGs) in the redshift range 0.8 < z < 1.1 and investigate the impact on the BAO constraints. DESI DR1 contains ∼ 30% of the final DESI LRG sample and less than 25% of the final ELG sample, and the combination of LRGs and ELGs increases the number density and reduces the shot noise. We developed a pipeline to merge the overlapping tracers using galaxy bias as an approximately optimal weight and tested the pipeline on a suite of Abacus simulations, calibrated on the final version of the DESI Early Data Release. When applying our pipeline to the DESI DR1 catalog, we find an improvement in the BAO constraints of 11% for α iso and ∼ 7.0% for α AP consistent with our findings in mock catalogs. Our analysis was integrated into the DESI DR1 BAO analysis to produce the LRG+ELG result in the 0.8 < z < 1.1 redshift bin, which provided the most precise BAO measurement from DESI DR1 with a 0.86% constraint on the BAO distance scale and a 9.1 σ detection of the isotropic BAO feature.

Large Scale Spectrophotometric Relative Flux Calibration for the Roman High Latitude Wide Area Survey

ArXiv.org · 2026-03-25

We consider the application of a ubercalibration-like relative flux calibration to the grism observations of the Roman High Latitude Wide Area Survey (HLWAS). We propose a simplified model of the calibration with an independent flat field for each detector in each exposure of the focal plane. In addition, we include two wavelength dependent components: a single wavelength throughput curve, modulated by a simple parabolic model for the throughput as a function of a source's focal plane position. We consider the impact of the dither scale, as well as the calibrator magnitude cuts. We show that the width of the calibration residuals can be reduced to less than 1.5 mmag, or 0.15% in flux, within the optimal dither range 50-240". This wide range allows for significant flexibility in optimising other parts of the observing program without diminishing the effectiveness of the relative flux calibration. We also discuss some improvements to the methodology that must be strongly considered before the calibration can be applied to real data. Finally, although we focused on spectroscopic component of the HLWAS here, our formalism and results should carry over to the imaging surveys as well.

The DESI Single Fiber Lens Search. I. Four Thousand Spectroscopically Selected Galaxy–Galaxy Gravitational Lens Candidates

The Astrophysical Journal · 2026-03-03

Abstract We present 4110 strong gravitational lens candidates, 3887 of which are new discoveries, selected from a sample of 5,837,154 luminous red galaxies (LRGs) observed with the Dark Energy Spectroscopic Instrument (DESI). Candidates are identified via the presence of background ionized oxygen [O ii ] nebular emission lines in the foreground LRG spectra, which may originate from the lensing of higher-redshift star-forming galaxies. Using the measured foreground redshift, background redshift, and integrated flux of the background [O ii ] doublet, we integrate over impact parameters to compute the probability that each candidate is a lens. We expect 53% of candidates to be true lenses with Einstein radii ranging from 0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>″</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 1–4″, which can be confirmed with high-resolution imaging. Confirmed strong lenses from this sample will form a valuable cosmological data set, as strong gravitational lensing is the only method to directly measure dark matter halo substructure at cosmological distances. We independently recover the host of the multiply imaged gravitationally lensed type Ia supernova iPTF16geu. Monitoring these lenses for future multiply lensed transients will enable (a) H 0 measurements via time-delay cosmography and (b) substructure measurements via flux ratios.

Illuminating the Physics of Cosmic Origin and Evolution: A UK Space Frontiers 2035 White Paper

arXiv (Cornell University) · 2026-01-23

Understanding the Universe's origins and evolution remains one of the most fundamental challenges in modern cosmology. This white paper explores three key science priorities in this field: unravelling the physics of cosmic inflation, investigating the accelerating expansion of the Universe, and precisely measuring the sum of the neutrino masses. Achieving these goals requires a dedicated survey to map the large-scale structure at high redshift in unprecedented detail. We describe how this can be achieved through a mission concept called SIRMOS, providing a high-throughput, highly multiplexed spectroscopic capability to obtain accurate redshifts for over 100 million galaxies over a wide sky area. Such a survey would leverage the deepest existing wide-area photometric catalogues for targeting, with spectra offering continuous 1.25-2.5~$μ$m wavelength coverage at moderate resolution, allowing precise redshift measurements in the $1

Illuminating the Physics of Cosmic Origin and Evolution: A UK Space Frontiers 2035 White Paper

ArXiv.org · 2026-01-23

Understanding the Universe's origins and evolution remains one of the most fundamental challenges in modern cosmology. This white paper explores three key science priorities in this field: unravelling the physics of cosmic inflation, investigating the accelerating expansion of the Universe, and precisely measuring the sum of the neutrino masses. Achieving these goals requires a dedicated survey to map the large-scale structure at high redshift in unprecedented detail. We describe how this can be achieved through a mission concept called SIRMOS, providing a high-throughput, highly multiplexed spectroscopic capability to obtain accurate redshifts for over 100 million galaxies over a wide sky area. Such a survey would leverage the deepest existing wide-area photometric catalogues for targeting, with spectra offering continuous 1.25-2.5~$μ$m wavelength coverage at moderate resolution, allowing precise redshift measurements in the $1<z<4$ range with minimal bias. We outline the scientific opportunities this presents. Recent years have seen significant advances in instrumentation, including digital micromirror devices, complex telescope mirrors, large detector arrays, and data processing pipelines. While these technologies have been demonstrated in terrestrial applications, such a survey is a unique opportunity to apply these proven capabilities in space to address fundamental questions in cosmology. Participation in such a mission will simultaneously deliver a compelling science case, help align UK Space Agency and STFC strategies, demonstrate the UK's growing capability in end-to-end space missions, and strengthen the national space economy through high-value industrial participation.

Postmortem Associations Between Alzheimer Disease Pathology and Plasma pTau217, GFAP, and NfL in AD and AD-Related Dementias

Neurology · 2026-01-29 · 2 citations

BACKGROUND AND OBJECTIVES: Alzheimer disease (AD) and its related disorders (ADRDs) are characterized by a high frequency of copathologies. We aimed to determine the specificity of plasma pTau217, glial fibrillary acidic protein (GFAP), and neurofilament light chain (NfL) for AD neuropathological change (ADNC) in the presence of common ADRD copathologies. METHODS: pTau217, GFAP, and NfL were measured using S-PLEX immunoassays from Meso Scale Discovery in banked plasma samples from 2 groups of participants in the Massachusetts Alzheimer's Disease Research Center (MADRC) Longitudinal Cohort study: (1) participants spanning the cognitive spectrum, who underwent brain autopsy, and blood collection within 6 years before death, and (2) participants with normal cognition and no neurologic diagnosis during 5 years of follow-up, but no autopsy data (normal controls [NCs]). Cross-sectional associations between biomarker levels and ADNC, primary neuropathologic diagnosis (NPDx1), and presence of non-AD copathologies were evaluated using linear regression models controlling for age, sex, and time to death. RESULTS: One hundred eighty-seven participants with brain autopsy (NPDx1: AD n = 85; other n = 102; mean age: 74.3 years, 38.5% female; interval blood collection-death [mean ± SD]: 2.8 ± 1.6 years) and 67 NC without brain autopsy (mean age: 66.5 years, 71.6% female) were included. pTau217, but not GFAP, levels increased stepwise with increasing Thal phases (β = 0.61; 95% CI [0.24-0.97] to β = 0.91 [0.55-1.27]) and Braak stages (β = 0.59; [0.16-1.01] to β = 0.74 [0.33-1.15]). Although 23% of individuals with a non-AD NPDx1 had increased pTau217 levels using a cutoff defined by the contrast between ADNC and NC, the majority (62%) had intermediate/high ADNC copathology and the remaining pTau217+ individuals had borderline increased levels. By contrast, 48% of individuals without ADNC had increased GFAP levels. pTau217 and GFAP were not different in the presence or absence of cerebral amyloid angiopathy, α-synuclein or TDP-43 proteinopathies, or primary tauopathies. NfL was not specifically associated with ADNC. DISCUSSION: Plasma pTau217, but not GFAP or NfL, levels accurately reflect the presence of ADNC in the brain even in individuals with an NPDx1 of a non-AD dementia. Thus, a positive plasma pTau217 test in an individual with a suspected non-AD dementia should not necessarily be considered a misdiagnosis of the presumed non-AD dementia or as a false positive, but rather as evidence of ADNC copathology.

Association of plasma biomarkers with recurrence in glioblastoma.

Journal of Clinical Oncology · 2025-05-28

e14017 Background: Adult-type diffuse gliomas are common malignant tumors known for their high recurrence rates, regardless of grade. High recurrence is due to incomplete resection of the tumors and the infiltrative nature of the tumor cells. Unfortunately, prediction of recurrence relies solely on MRI, a method that is expensive and susceptible to errors, treatment and pseudo-progression effects. Capturing recurrence prior to MRI is an unmet clinical need and could allow for earlier intervention or enrolment of patients into clinical trials. Liquid biopsy has emerged as a promising approach. Methods: Previously collected patient plasma was retrieved from three sites: Northwestern University Tumor Biobank, Penn State Neuroscience Biorepository and University Health Network Biobank (Cross-sectional samples(all primary vs all recurrent) n = 264, patients with multiple samples (longitudinal) n = 44; Groups = Glioblastoma (GBM), astrocytoma, oligodendroglioma) and analyzed retrospectively for seven proteomic markers: GFAP, NEFL, FABP4, MMP1, MMP3, MMP9 and total tau (tTau) using research-use-only electrochemiluminescence assays available from Meso Scale Discovery. For the cross-sectional analysis (independent samples per patient), Wilcoxon rank sum test with post hoc Holm’s correction was used to compare biomarker values in samples from individuals with primary and recurrent tumors, after adjusting for sex differences. For the longitudinal analysis of paired primary and recurrence samples, Wilcoxon signed-rank test was used. Survival probability was tested through Kaplan-Meier survival curves. Results: In the cross-sectional analysis of the diffuse gliomas (GBM = 77+129 [Batch 1 + Batch 2], Oligodendroglioma = 23 +11, Astrocytoma = 26 + 25), we found that in the GBM group, the median values of MMP9 and GFAP were lower during recurrence. The median NEFL value was higher during GBM recurrence but did not achieve statistical significance, although the same effect was observed in the longitudinal analysis. In survival analyses, higher MMP3 and MMP9 in primary case samples across all diffuse gliomas were significantly associated with poorer survival, but this significance was lost during recurrence, indicating potentially important differences between a primary and a recurrent state. Conclusions: This cross-sectional and longitudinal retrospective pilot study evaluated seven plasma markers for the potential capability of predicting tumor recurrence in adult-type diffuse gliomas. While we found no significant differences across diffuse gliomas overall, subgroup analyses revealed recurrence-associated patterns. These findings suggest that certain markers could complement imaging for recurrence detection and perhaps prediction. Larger and more comprehensive studies are warranted.

Fiducial-cosmology-dependent systematics for the DESI 2024 BAO analysis

Journal of Cosmology and Astroparticle Physics · 2025-01-01 · 20 citations

Abstract When measuring the Baryon Acoustic Oscillations (BAO) scale from galaxy surveys, one typically assumes a fiducial cosmology when converting redshift measurements into comoving distances and also when defining input parameters for the reconstruction algorithm. A parameterised template for the model to be fitted is also created based on a (possibly different) fiducial cosmology. This model reliance can be considered a form of data compression, and the data is then analysed allowing that the true answer is different from the fiducial cosmology assumed. In this study, we evaluate the impact of the fiducial cosmology assumed in the BAO analysis of the Dark Energy Spectroscopic Instrument (DESI) survey Data Release 1 (DR1) on the final measurements in DESI 2024 III. We utilise a suite of mock galaxy catalogues with survey realism that mirrors the DESI DR1 tracers: the bright galaxy sample (BGS), the luminous red galaxies (LRG), the emission line galaxies (ELG) and the quasars (QSO), spanning a redshift range from 0.1 to 2.1. We compare the four secondary AbacusSummit cosmologies against DESI's fiducial cosmology (Planck 2018). The secondary cosmologies explored include a lower cold dark matter density, a thawing dark energy universe, a higher number of effective species, and a lower amplitude of matter clustering. The mocks are processed through the BAO pipeline by consistently iterating the grid, template, and reconstruction reference cosmologies. We determine a conservative systematic contribution to the error of 0.1% for both the isotropic and anisotropic dilation parameters α iso and α AP . We then directly test the impact of the fiducial cosmology on DESI DR1 data.