The galaxy-electron cross-spectrum with ACT, SPT-3G and DESILS LRGs
Abstract
The galaxy--electron cross-power spectrum Pge(k) measures the small-scale distribution of gas around galaxies, the quantity reshaped by feedback. We measure Pge from the kinetic Sunyaev--Zel'dovich (kSZ) signal of the photometric DESI Legacy Imaging Surveys luminous red galaxies, cross-correlating a velocity-weighted galaxy momentum template with the CMB temperature from ACT DR6 and, for the first time, SPT-3G. The absolute normalization of the cross-spectrum is fixed by a surrogate-field Monte Carlo that propagates the survey mask, lightcone evolution, and photometric-redshift weights, converting the measured pseudo-spectrum into Pge(k) in physical units. We detect Pge at 11.7σ with ACT and 8.4σ with SPT-3G, and at 12.3σ combining SPT-3G with the ACT northern cap, which it does not overlap. The two surveys have independent optics, beams, filtering and noise and share about two thirds of the SPT-3G galaxies; their amplitudes agree channel by channel, the largest difference being 0.7σ. All $26$ null tests on the adopted night maps are consistent with zero signal, among them the six ACT frequency differences, the three SPT-3G frequency differences, and the four ACT cap differences of the main selection. Turning the amplitude into a gas fraction requires the host halo masses of the sample, which the cross-spectrum does not itself measure; taking them from its measured number density and from a published CMB-lensing calibration of the same galaxies, the gas within the virial radius is $25−−33\%$ of the cosmic baryon budget of the halo.
Related
- Measurement of the Dispersion-Galaxy Cross-Power Spectrum with the Second CHIME/FRB Catalog
- Does galaxy-scale compactness regulate nebular electron density? A cross-scale test with DESI
- Broadband radio continuum and host galaxy properties of extremely inverted spectrum compact radio galaxies
- From quantum fluctuations to galaxy power spectrum multipoles
- Euclid preparation. CXV. Galaxy power spectrum and bispectrum modelling
BibTeX
@misc{hotinli2026galaxyelectron,
title = {{The galaxy-electron cross-spectrum with ACT, SPT-3G and DESILS LRGs}},
author = {Selim C. Hotinli},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17676},
eprint = {2609.17676},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17676},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The galaxy-electron cross-spectrum with ACT, SPT-3G and DESILS LRGs
AU - Selim C. Hotinli
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.17676
UR - https://arxiv.org/abs/2609.17676
AB - The galaxy--electron cross-power spectrum P_ge(k) measures the small-scale distribution of gas around galaxies, the quantity reshaped by feedback. We measure P_ge from the kinetic Sunyaev--Zel'dovich (kSZ) signal of the photometric DESI Legacy Imaging Surveys luminous red galaxies, cross-correlating a velocity-weighted galaxy momentum template with the CMB temperature from ACT DR6 and, for the first time, SPT-3G. The absolute normalization of the cross-spectrum is fixed by a surrogate-field Monte Carlo that propagates the survey mask, lightcone evolution, and photometric-redshift weights, converting the measured pseudo-spectrum into P_ge(k) in physical units. We detect P_ge at 11.7σ with ACT and 8.4σ with SPT-3G, and at 12.3σ combining SPT-3G with the ACT northern cap, which it does not overlap. The two surveys have independent optics, beams, filtering and noise and share about two thirds of the SPT-3G galaxies; their amplitudes agree channel by channel, the largest difference being 0.7σ. All $26$ null tests on the adopted night maps are consistent with zero signal, among them the six ACT frequency differences, the three SPT-3G frequency differences, and the four ACT cap differences of the main selection. Turning the amplitude into a gas fraction requires the host halo masses of the sample, which the cross-spectrum does not itself measure; taking them from its measured number density and from a published CMB-lensing calibration of the same galaxies, the gas within the virial radius is $25−−33\%$ of the cosmic baryon budget of the halo.
ER -