Deeper multi-redshift upper limits on the Epoch of Reionization 21-cm signal power spectrum from LOFAR between z=8.3 and z=10.1

Abstract

We present new upper limits on the 21-cm signal power spectrum from the Epoch of Reionization (EoR), at redshifts $z\approx 10.1,9.1,\text{ and }8.3$, based on reprocessed observations from the Low-Frequency Array (LOFAR). The analysis incorporates significant enhancements in calibration methods, sky model subtraction, radio-frequency interference (RFI) mitigation, and an improved signal separation technique using machine learning to develop a physically motivated covariance model for the 21-cm signal. These advancements have markedly reduced previously observed excess power due to residual systematics, bringing the measurements closer to the theoretical thermal noise limit across the entire $k$-space. Using comparable observational data, we achieve a 2 to 4-fold improvement over our previous LOFAR limits, with best upper limits of ${\Delta }_{21}^2<(68.7\mathrm{mK}{)}^2$ at $k=0.076h{\mathrm{cMpc}}^{-1}$, ${\Delta }_{21}^2<(54.3\mathrm{mK}{)}^2$ at $k=0.076h{\mathrm{cMpc}}^{-1}$ and ${\Delta }_{21}^2<(65.5\mathrm{mK}{)}^2$ at $k=0.083h{\mathrm{cMpc}}^{-1}$ at redshifts $z\approx 10.1,9.1$, and $8.3$, respectively. These new multi-redshift upper limits provide new constraints that can be used to refine our understanding of the astrophysical processes during the EoR. Comprehensive validation tests, including signal injection, were performed to ensure the robustness of our methods. The remaining excess power is attributed to residual foreground emissions from distant sources, beam model inaccuracies, and low-level RFI. We discuss ongoing and future improvements to the data processing pipeline aimed at further reducing these residuals, thereby enhancing the sensitivity of LOFAR observations in the quest to detect the 21-cm signal from the EoR.

Accepted in A&A

References in corpus (37)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The evolution of the galaxy UV luminosity function at redshifts z ~ 8-15 from deep JWST and ground-based near-infrared imaging
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• Stress Testing $\Lambda$CDM with High-redshift Galaxy Candidates
• Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\mathbf{z}\approx 9.1$ from LOFAR
• Foreground simulations for the LOFAR - Epoch of Reionization Experiment
• Revealing Galaxy Candidates out to $z\sim 16$ with JWST Observations of the Lensing Cluster SMACS0723
• Deep multi-redshift limits on Epoch of Reionisation 21cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
• The brightest galaxies at Cosmic Dawn
• The Epoch of Reionization Window: II. Statistical Methods for Foreground Wedge Reduction
• Confirmation and refutation of very luminous galaxies in the early universe
• Signature of Excess Radio Background in the 21-cm Global Signal and Power Spectrum
• Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
• A Significantly Neutral Intergalactic Medium Around the Luminous z=7 Quasar J0252-0503
• First Season MWA EoR Power Spectrum Results at Redshift 7
• Evolution of the UV LF from z~15 to z~8 Using New JWST NIRCam Medium-Band Observations over the HUDF/XDF
• 21 cm signal from cosmic dawn: Imprints of spin temperature fluctuations and peculiar velocities
• Constraining the intergalactic medium at $z\approx$ 9.1 using LOFAR Epoch of Reionization observations
• Distributed Radio Interferometric Calibration
• Characterisation of the ionosphere above the Murchison Radio Observatory using the Murchison Widefield Array
• Mitigating Internal Instrument Coupling II: A Method Demonstration with the Hydrogen Epoch of Reionization Array
• The impact of interference excision on 21-cm Epoch of Reionization power spectrum analyses
• Comparing Foreground Removal Techniques for Recovery of the LOFAR-EoR 21cm Power Spectrum
• First upper limits on the 21 cm signal power spectrum from cosmic dawn from one night of observations with NenuFAR
• Reionization inference from the CMB optical depth and E-mode polarization power spectra
• New EoR Power Spectrum Limits From MWA Phase II Using the Delay Spectrum Method and Novel Systematic Rejection
• Assessing the impact of two independent direction-dependent calibration algorithms on the LOFAR 21-cm signal power spectrum
• Statistical analysis of the causes of excess variance in the 21 cm signal power spectra obtained with the Low-Frequency Array
• Trajectory Based RFI Subtraction and Calibration for Radio Interferometry
• Beyond the horizon: Quantifying the full sky foreground wedge in the cylindrical power spectrum
• Constraints on the state of the IGM at $z\sim 8-10$ using redshifted 21-cm observations with LOFAR
• Ionospheric contributions to the excess power in high-redshift 21-cm power-spectrum observations with LOFAR
• Spectral modelling of Cygnus A between 110 and 250 MHz. Impact on the LOFAR 21-cm signal power spectrum
• Near-field imaging of local interference in radio interferometric data: Impact on the redshifted 21 cm power spectrum
• Effects of model incompleteness on the drift-scan calibration of radio telescopes
• A novel radio imaging method for physical spectral index modelling

Cited by in corpus (16)

• Constraints on the state of the IGM at $z\sim 8-10$ using redshifted 21-cm observations with LOFAR
• Improved upper limits on the 21-cm signal power spectrum at $z=17.0$ and $z=20.3$ from an optimal field observed with NenuFAR
• Field-level Reconstruction from Foreground-Contaminated 21-cm Maps
• Robust direction-dependent gain-calibration of beam-modelling errors far from the target field
• Impact of Calibration and Position Errors on Astrophysical Parameters of the HI 21cm Signal
• The 21cm-galaxy cross-correlation: Realistic forecast for 21cm signal detection and reionisation constraints
• Narrowing the discovery space of the cosmological 21-cm signal using multi-wavelength constraints
• From ANN to BNN: Inferring Reionization Parameters using Uncertainty-aware Emulators of 21-cm Summaries
• Fundamental Physics in 2025: Status, Decisive Targets, and Path Forward
• Impact of anisotropic photon emission from sources during the epoch of reionisation
• Mapping neutral islands during end stages of reionization with photometric intergalactic medium tomography
• CosmoUiT: A Vision Transformer-UNet Hybrid for Fast and Accurate Emulation of 21-cm Maps from the Epoch of Reionization
• Impact of 21-cm foreground mitigation strategies on reionization power spectrum constraints
• Mitigating incoherent excess variance in high-redshift 21 cm observations with multi-output cross-Gaussian process regression
• Mitigating gain calibration errors from EoR observations with SKA1-Low AA*
• POLAR-II: modeling star formation history of galaxies on the 21-cm signal from Epoch of Reionization