Search for: All records

Abstract The neutrino signal from the next galactic core-collapse supernova will provide an invaluable early warning of the explosion. By combining the burst trigger from several neutrino detectors, the location of the explosion can be triangulated minutes to hours before the optical emission becomes visible, while also reducing the rate of false-positive triggers. To enable multi-messenger follow-up of nearby supernovae, the SuperNova Early Warning System 2.0 (SNEWS 2.0) will produce a combined alert using a global network of neutrino detectors. This paper describes the trigger publishing and alert formation framework of the SNEWS 2.0 network. The framework is built on the HOPSKOTCH publish-subscribe system to easily incorporate new detectors into the network, and it implements a coincidence system to form alerts and estimate a false-positive rate for the combined triggers. The paper outlines the structure of the SNEWS 2.0 software and the initial testing of coincident signals. 

Abstract We present a new measurement of the Hubble constant,H₀, following the gravitational-wave event GW170817 and Dark Energy Spectroscopic Instrument (DESI) observations. A standard siren measurement with a nearby (luminosity distance ∼40 Mpc) event such as GW170817 is typically sensitive to the peculiar motion of the host galaxy owing to local dynamics. Previous measurements from this event have taken advantage of peculiar velocity measurements of nearby galaxies, including a handful of objects in the galaxy group that the host of the event, NGC 4993, has been associated with. Still, the group’s properties and NGC 4993’s membership were debated. We present DESI observations of thousands of galaxies in the vicinity of NGC 4993, resulting in 39 group galaxies and a fivefold increase in galaxies compared to previous observations, with many contributing to a peculiar velocity measurement. Examining the local dynamics, our observations support the presence of a galaxy group of which NGC 4993 is a part with a halo mass of order ∼10¹³M_⊙. Using peculiar velocity measurements from our fundamental plane galaxy observations, we find $H_0=70.9_{-8.5}^{+6.4}$  km s⁻¹ Mpc⁻¹. In addition, using a peculiar velocity measurement for NGC 4993 from surface brightness fluctuations in Cosmicflows-4, we find $H_0=73.4_{-3.9}^{+3.3}$  km s⁻¹ Mpc⁻¹. We study the impact of different galaxy selection criteria on the determination of the peculiar velocity and, in turn, on theH₀measurement. Our results demonstrate the value of multiplexed spectroscopic observations for probing the local environments of gravitational-wave events used in standard siren measurements. 

Abstract We measure the projected two-point correlation functions of emission-line galaxies (ELGs) from the Dark Energy Spectroscopic Instrument One-Percent Survey and model their dependence on stellar mass and [OII] luminosity. We select ∼180,000 ELGs with redshifts of 0.8 < z < 1.6, and define 27 samples according to cuts in redshift and both galaxy properties. Following a framework that describes the conditional [OII] luminosity–stellar mass distribution as a function of halo mass, we simultaneously model the clustering measurements of all samples at fixed redshift. Based on the modeling result, most ELGs in our samples are classified as central galaxies, residing in halos of a narrow mass range with a typical median of ∼10^12.2−12.4h⁻¹M_⊙. We observe a weak dependence of clustering amplitude on stellar mass, which is reflected in the model constraints and is likely a consequence of the 0.5 dex measurement uncertainty in the stellar mass estimates. The model shows a trend between galaxy bias and [OII] luminosity at high redshift (1.2 < z < 1.6) that is otherwise absent at lower redshifts. 

Abstract The IceCube Neutrino Observatory, a cubic-kilometer detector at the South Pole, identifies neutrino flavor through event morphology. Sparse photon detection makes this classification particularly challenging in the 5–100 GeV regime, the energy range relevant for oscillation measurements and searches for physics beyond the Standard Model. We introduceWavePID, a template-based log-likelihood-ratio classifier that exploits nanosecond-scale timing on individual detector modules through three observables: the distance to the reconstructed vertex, the early-charge fraction, and the module-to-module time difference. Evaluated on a cascade-enriched sample selected by a state-of-the-art graph neural network,WavePIDimproves both cascade purity and classification performance over the neural network alone. This demonstrates that per-module pulse timing carries flavor-identification information complementary to morphology-based classifiers, opening a new physics-motivated observable for low-energy neutrino reconstruction.Geant4simulations associate this signal with differences in Cherenkov emission geometry between muon tracks and electromagnetic showers. These results motivate exploiting nanosecond-scale pulse timing in future low-energy classifiers and in detector designs with improved per-module timing in next-generation neutrino telescopes. 

This Letter extends a recent IceCube sterile neutrino search to include unstable sterile neutrinos within the context of a model termed $3+1+\mathrm{Decay}$ , which expands upon the $3+1$ model by introducing sterile neutrino decay to invisible particles with coupling constant $g^2$ . The model is attractive since it reduces tension between oscillation experiments within the global fits and with constraints that come from cosmological observables. The analysis uses 10.7 years of up-going muon neutrino data with energy 500 GeV to 100 TeV and with improved reconstruction and modeling of systematics. The best-fit point is found to be $g^2=0$ , ${\sin }^2\left(2{\theta }_{24}\right)=0.16$ , and $\mathrm{\Delta }{m}_{41}^2=3.5{\mathrm{eV}}^2$ , in agreement with the recent $3+1$ sterile neutrino search. Values of $g^2\ge \pi$ are excluded at 95% confidence level. This result substantially limits decay parameter space indicated by recent global fits, disfavoring the decay scenario. 

The Dark Energy Spectroscopic Instrument (DESI) Collaboration has obtained robust measurements of baryon acoustic oscillations in the redshift range $0.1<z<4.2$ , based on the Lyman- $\alpha$ forest and galaxies from data release 2. We combine these measurements with cosmic microwave background (CMB) data from and the Atacama Cosmology Telescope to place our tightest constraints yet on the sum of neutrino masses. Assuming the cosmological $\mathrm{\Lambda }\mathrm{CDM}$ model and three degenerate neutrino states, we find $\sum m_{\nu }<0.0642\mathrm{eV}$ (95%) with a marginalized error of $\sigma (\sum m_{\nu })=0.020\mathrm{eV}$ . We also constrain the effective number of neutrino species, finding $N_{\mathrm{eff}}=3.23_{-0.34}^{+0.35}$ (95%), in line with the Standard Model prediction. When accounting for neutrino oscillation constraints, we find a preference for the normal mass ordering and an upper limit on the lightest neutrino mass of $m_l<0.023\mathrm{eV}$ (95%). However, we determine using frequentist and Bayesian methods that our constraints are in tension with the lower limits derived from neutrino oscillations. Correcting for the physical boundary at zero mass, we report a 95% Feldman-Cousins upper limit of $\sum m_{\nu }<0.053\mathrm{eV}$ , breaching the lower limit from neutrino oscillations. Considering a more general Bayesian analysis with an effective cosmological neutrino mass parameter, $\sum m_{\nu ,\mathrm{eff}}$ , that allows for negative energy densities and removes unsatisfactory prior weight effects, we derive constraints that are in $3\sigma$ tension with the same oscillation limit, while the error rises to $\sigma (\sum m_{\nu ,\mathrm{eff}})=0.053\mathrm{eV}$ . In the absence of unknown systematics, this finding could be interpreted as a hint of new physics not necessarily related to neutrinos. The preference of DESI and CMB data for an evolving dark energy model offers one possible solution. In the $w_0{w}_a\mathrm{CDM}$ model, we find $\sum m_{\nu }<0.163\mathrm{eV}$ (95%), relaxing the neutrino tension. These constraints all rely on the effects of neutrinos on the cosmic expansion history. Using full-shape power spectrum measurements of data release 1 galaxies, we place complementary constraints that rely on neutrino free streaming. Our strongest such limit in $\mathrm{\Lambda }\mathrm{CDM}$ , using selected CMB priors, is $\sum m_{\nu }<0.193\mathrm{eV}$ (95%). 

We conduct an extended analysis of dark energy constraints, in support of the findings of the Dark Energy Spectroscopic Instrument (DESI) second data release cosmology key paper, including DESI data, Planck cosmic microwave background observations, and three different supernova compilations. Using a broad range of parametric and nonparametric methods, we explore the dark energy phenomenology and find consistent trends across all approaches, in good agreement with the $w_0{w}_a\mathrm{CDM}$ (cold dark matter) key paper results. Even with the additional flexibility introduced by nonparametric approaches, such as binning and Gaussian processes, we find that extending $\mathrm{\Lambda }\mathrm{CDM}$ to include a two-parameter $w\left(z\right)$ is sufficient to capture the trends present in the data. Finally, we examine three dark energy classes with distinct dynamics, including quintessence scenarios satisfying $w\ge -1$ , to explore what underlying physics can explain such deviations. The current data indicate a clear preference for models that feature a phantom crossing; although alternatives lacking this feature are disfavored, they cannot yet be ruled out. Our analysis confirms that the evidence for dynamical dark energy, particularly at low redshift ( $z\lesssim 0.3$ ), is robust and stable under different modeling choices.