Abstracts of Interest
Selected by:
Caleb Lotstra
Abstract: 2503.12898
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Title:A Sample of Low-mass AGNs Extended to z $\approx$ 0.6
View PDFAbstract:We present a catalog of 927 low-mass active galactic nuclei (AGNs) with black hole mass of $M_{BH}\leqslant2\times10^{6} M_{\odot}$ characterized by broad H$\alpha$ or H$\beta$ emission lines,uniformly selected from the Seventeenth Data Release (DR17) of the Sloan Digital Sky Survey (SDSS) spectra. Taking advantages of the wide wavelength coverage of BOSS/eBOSS spectra of the SDSS, this sample significantly extends the redshift range to $z\leqslant0.57$, a marked improvement over the previous studies which were generally limited to $z\leqslant0.35$. This sample encompasses black hole masses from $10^{3.7}$ to $10^{6.3} M_{\odot}$, with Eddington ratios ranging from 0.01 to 3.3. Preliminary analysis of this sample reveals a marked decline in maximum accretion rates (namely $L/L_{Edd}$) and broad-H$\alpha$ luminosities with decreasing redshift, analogous to the passive ``downsizing'' evolutionary trend observed in high-mass AGNs. This systematic catalog of low-redshift low-mass AGNs, the largest so far, will benefit the studies on accretion physics, AGN--galaxy connection and the origin of supermassive black holes.
Abstract: 2503.12950
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Title:JWST/MIRI detects the dusty SN1993J about 30 years after explosion
View PDF HTML (experimental)Abstract:Core-collapse supernovae (CCSNe) have long been considered to contribute significantly to the cosmic dust budget. New dust cools quickly and is therefore detectable at mid-infrared (mid-IR) wavelengths. However, before the era of the James Webb Space Telescope (JWST), direct observational evidence for dust condensation was found in only a handful of nearby CCSNe, and dust masses (~10$^{-2}-10^{-3} M_{\odot}$, generally limited to <5 yr and to >500K temperatures) have been 2-3 orders of magnitude smaller than either theoretical predictions or dust amounts found by far-IR/submm observations of Galactic SN remnants and in the very nearby SN 1987A. The combined angular resolution and mid-IR sensitivity of JWST finally allow us to reveal hidden cool (~100-200K) dust reservoirs in extragalactic SNe beyond SN 1987A. Our team received JWST/MIRI time for studying a larger sample of CCSNe to fill the currently existing gap in their dust formation histories. The first observed target of this program is the well-known Type IIb SN~1993J appeared in M81. We generated its spectral energy distribution (SED) from the current JWST/MIRI F770W, F1000W, F1500W, and F2100W fluxes. We fit single- and two-component silicate and carbonaceous dust models to the SED. We found that SN 1993J still contains a significant amount (~0.01 $M_{\odot}$) of dust ~30 yr after explosion. Comparing these results to those of the analysis of earlier {Spitzer Space Telescope data, we see a similar amount of dust now that was detected ~15-20 yr ago, but at a lower temperature. We also find residual background emission near the SN site (after point-spread-function subtraction on the JWST/MIRI images) that may plausibly be attributed to an IR echo from more distant interstellar dust grains heated by the SN shock-breakout luminosity or ongoing star formation in the local environment.
Abstract: 2503.13118
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Title:Gravitational Wave Effects on Radio Spectral Lines of Atomic Hydrogen: Hyperfine Splitting and Broadening Mechanisms
View PDF HTML (experimental)Abstract:We explore the effects of gravitational waves (GWs) on hydrogen's radio spectral lines, focusing on the ground-state hyperfine transition and radiative transitions in highly excited Rydberg states. To analyze GW impacts on hyperfine structure, we derive Maxwell's equations in a gravitational-wave background using linearized gravity and the $3+1$ formalism. Our findings reveal that GWs induce energy shifts in hyperfine magnetic substates, modifying the 21 cm line. However, these energy shifts fall well below the detection limits of current radio astronomical instruments. For transitions in highly excited states, which produce radio recombination lines (RRL), the influence of GW manifests itself as spectral broadening, with the fractional linewidth for $\mathrm{H}n\alpha$ scaling as $\Delta\nu/\nu_0 \sim n^7\omega^2_{\mathrm{gw}}h(t)$. This suggests that RRLs could serve as probes for ultra-high-frequency GWs, particularly given that Rydberg atoms in the interstellar medium can reach quantum numbers above $n=100$. As an example of possibly detectable high frequency GW source, We investigate GWs emitted during the inspiral of planetary-mass primordial black hole binaries, where GW-induced broadening in RRLs could exceed natural broadening effects. Additionally, we examine the influence of the recently detected stochastic gravitational-wave background on hydrogen spectral lines.
Abstract: 2503.13315
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Title:Sombrero Galaxy as an Accelerator of Ultrahigh Energy Cosmic Ray Nuclei
View PDF HTML (experimental)Abstract:Motivated by a recent proposal that points to the Sombrero galaxy as a source of the highest energy cosmic rays, we investigate the feasibility of accelerating light and heavy nuclei in the supermassive black hole located at the center of this dormant galaxy. We show that cosmic ray nuclei concentrated in the immediate vicinity of the supermassive black hole could be efficiently accelerated up to the maximum observed energies without suffering catastrophic spallations. Armed with our findings we stand against the conventional wisdom and conjecture that accelerators of the highest energy cosmic rays must anti-correlate with the (electromagnetic) source power.
Abstract: 2503.13632
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Title:Dark Energy Survey Year 3 Results: Cosmological Constraints from Cluster Abundances, Weak Lensing, and Galaxy Clustering
View PDF HTML (experimental)Abstract:Galaxy clusters provide a unique probe of the late-time cosmic structure and serve as a powerful independent test of the $\Lambda$CDM model. This work presents the first set of cosmological constraints derived with ~16,000 optically selected redMaPPer clusters across nearly 5,000 $\rm{deg}^2$ using DES Year 3 data sets. Our analysis leverages a consistent modeling framework for galaxy cluster cosmology and DES-Y3 joint analyses of galaxy clustering and weak lensing (3x2pt), ensuring direct comparability with the DES-Y3 3x2pt analysis. We obtain constraints of $S_8 = 0.864 \pm 0.035$ and $\Omega_{\rm{m}} = 0.265^{+0.019}_{-0.031}$ from the cluster-based data vector. We find that cluster constraints and 3x2pt constraints are consistent under the $\Lambda$CDM model with a Posterior Predictive Distribution (PPD) value of $0.53$. The consistency between clusters and 3x2pt provides a stringent test of $\Lambda$CDM across different mass and spatial scales. Jointly analyzing clusters with 3x2pt further improves cosmological constraints, yielding $S_8 = 0.811^{+0.022}_{-0.020}$ and $\Omega_{\rm{m}} = 0.294^{+0.022}_{-0.033}$, a $24\%$ improvement in the $\Omega_{\rm{m}}-S_8$ figure-of-merit over 3x2pt alone. Moreover, we find no significant deviation from the Planck CMB constraints with a probability to exceed (PTE) value of $0.6$, significantly reducing previous $S_8$ tension claims. Finally, combining DES 3x2pt, DES clusters, and Planck CMB places an upper limit on the sum of neutrino masses of $\sum m_\nu < 0.26$ eV at 95% confidence under the $\Lambda$CDM model. These results establish optically selected clusters as a key cosmological probe and pave the way for cluster-based analyses in upcoming Stage-IV surveys such as LSST, Euclid, and Roman.
Abstract: 2503.14744
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Title:Constraints on Neutrino Physics from DESI DR2 BAO and DR1 Full Shape
View PDF HTML (experimental)Abstract:The Dark Energy Spectroscopic Instrument (DESI) Collaboration has obtained robust measurements of baryon acoustic oscillations (BAO) in the redshift range, $0.1 < z < 4.2$, based on the Lyman-$\alpha$ forest and galaxies from Data Release 2 (DR2). We combine these measurements with external cosmic microwave background (CMB) data from Planck and ACT to place our tightest constraints yet on the sum of neutrino masses. Assuming the cosmological $\Lambda$CDM model and three degenerate neutrino states, we find $\sum m_\nu<0.0642$ eV (95%). When accounting for neutrino oscillation constraints, we find a preference for the normal mass ordering and an upper bound of $m_l < 0.023$ eV (95%) on the lightest neutrino mass. However, we determine using frequentist and Bayesian methods that our constraints are in moderate tension with the lower limits derived from neutrino oscillations. Correcting for the physical boundary at zero mass, we report a 95% Feldman-Cousins upper bound of $\sum m_\nu<0.053$ 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. 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 $w_0w_a$CDM model, we find $\sum m_\nu<0.163$ eV (95%), resolving the neutrino tension. [Abridged]
Abstract: 2503.13904
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Title:Over-Luminous Type Ia Supernovae and Standard Candle Cosmology
View PDF HTML (experimental)Abstract:Type Ia supernovae (SNe Ia) serve as crucial cosmological distance indicators due to their empirical consistency in peak luminosity and characteristic light-curve decline rates. These properties facilitate them to be standardized candles for the determination of the Hubble constant ($H_0$) within late-time universe cosmology. Nevertheless, a statistically significant difference persists between $H_0$ values derived from early and late-time measurements, a phenomenon known as the Hubble tension. Furthermore, recent observations have identified a subset of over-luminous SNe Ia, characterized by peak luminosities exceeding the nominal range and faster decline rates. These discoveries raise questions regarding the reliability of SNe Ia as standard candles in measuring cosmological distances. In this article, we present the Bayesian analysis of eight over-luminous SNe Ia and show that they yield a lower $H_0$ estimates, exhibiting closer concordance with $H_0$ estimates derived from early-universe data. This investigation potentially represent a step toward addressing the Hubble tension.
Abstract: 2503.15052
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Title:Discrete treatment of inverse Compton scattering: implications on parameter estimation in gamma-ray astronomy
View PDF HTML (experimental)Abstract:In gamma-ray astronomy and cosmic-ray physics, the continuous approximation of inverse Compton scattering (ICS) is widely adopted to model the evolution of electron energy. However, when the initial electron energy approaches $\sim100$ TeV, the discrete nature of ICS becomes prominent, and the energy of evolved electrons should be considered as a broad distribution rather than a deterministic value. By simulating the evolution paths of individual electrons under ICS, we capture this discrete nature and demonstrate that when the electron injection spectrum exhibits a high-energy cutoff, the correct discrete treatment yields a higher cutoff energy in the evolved spectrum compared to the continuous approximation. Applying the discrete ICS treatment to interpret the gamma-ray spectrum of the Geminga pulsar halo measured by HAWC, we find that the inferred cutoff energy of the injection spectrum is correspondingly lower than that derived using the continuous approximation at a $95\%$ confidence level. This suggests that the systematic bias introduced by the approximation has exceeded the measurement precision. We also expect the application of the discrete ICS correction in the PeV regime using the ultra-high-energy gamma-ray source 1LHAASO J1954+2836u as a case study, pointing out that adopting the continuous approximation may considerably overestimate the electron acceleration capability of the source.