Abstracts of Interest
Selected by:
Caleb Lotstra
Abstract: 2406.19758
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Title:Forecast of cosmological constraints with superluminous supernovae from the Chinese Space Station Telescope
View PDF HTML (experimental)Abstract:Superluminous supernovae (SLSNe) are a class of intense celestial events that can be standardized for measuring cosmological parameters, bridging the gap between type Ia supernovae and the cosmic microwave background. In this work, we discuss the cosmological applications of SLSNe from the Chinese Space Station Telescope (CSST). Our estimation suggests that SLSNe rate is biased tracing the cosmic star formation rate, exhibiting a factor of $(1+z)^{1.2}$. We futher predict that CSST is poised to observe $\sim 360$ SLSNe in the 10 square degrees ultra-deep field survey within a span of 2.5 years. A stringent constraint on cosmological parameters can be derived from their peak-color relationship. CSST is anticipated to uncover a substantial number of SLSNe, contributing to a deeper understanding of their central engines and shedding light on the nature of dark energy at high redshifts.
Abstract: 2406.15390
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Title:Cosmological test of an ultraviolet origin of Dark Energy
View PDF HTML (experimental)Abstract:The accelerated expansion of the Universe is impressively well described by a cosmological constant. However, the observed value of the cosmological constant is much smaller than expected based on quantum field theories. Recent efforts to achieve consistency in these theories have proposed a relationship between Dark Energy and the most compact objects, such as black holes (BH). However, experimental tests are very challenging to devise and perform. In this article, we present a testable model with no cosmological constant, in which the accelerated expansion can be driven by black holes. The model couples the expansion of the Universe (the Friedmann equation) with the mass-function of cosmological haloes (using the Press-Schechter formalism). Through the observed link between halo-masses and BH-masses one thus gets a coupling between the expansion rate of the Universe and the BHs. We compare the predictions of this simple BH model with SN1a data and find a poor agreement with observations. Our method is sufficiently general that it allows us to also test a fundamentally different model, also without a cosmological constant, where the accelerated expansion is driven by a new force proportional to the internal velocity dispersion of galaxies. Surprisingly enough this model cannot be excluded using the SN1a data.
Abstract: 2406.17041
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Title:A New Gravitational Wave Probe to the Nature of Dark Energy from the Aging of the Universe: Can Future Detectors Achieve it?
View PDF HTML (experimental)Abstract:One of the most dominant energy budget of the Universe is Dark Energy, which remains enigmatic since the claim of its existence from the observation of late-time cosmic acceleration. We propose a new way of inferring this by measuring the aging of the Universe using only gravitational wave (GW) signals from coalescing binary compact objects of any masses. We show that the aging of the Universe will lead to a change in the observed chirp mass of the GW sources inferred from different stages of its coalesces by monitoring a coherent source from two far-apart GW frequencies for a few years. We show that coordinated GW detectors which can reach a relative uncertainty on chirp mass measurement of about $10^{-9}$, can measure a tiny departure of about $2\%$ from the dark energy equation of state parameter $w_0=-1$ and its variation with cosmic time by using stellar origin binary black holes up to redshift $z=5$ in 10 years of observation time without using any external calibrator. If the next generation of GW detectors can achieve this precision, then it can open a new window to discover the fundamental nature of dark energy.
Abstract: 2406.17847
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Title:Size matters: are we witnessing super-Eddington accretion in high-redshift black holes from JWST?
View PDF HTML (experimental)Abstract:Observations by the James Webb Space Telescope of the Universe at $z\gtrsim 4$ have shown that massive black holes (MBHs) appear extremely overmassive compared to the local correlation for active galactic nuclei. In some cases, these objects might even reach half the stellar mass inferred for the galaxy. Understanding how such objects formed and grew to this masses has then become a big challenge for theoretical models, with different ideas ranging from heavy seed to super-Eddington accretion phases. Here, we take a different approach, and try to infer how accurate these MBH mass estimates are and whether we really need to revise our physical models. By considering how the emerging spectrum (both the continuum and the broad lines) of an accreting MBH changes close to and above the Eddington limit, we infer a much larger uncertainty in the MBH mass estimates relative to that of local counterparts, up to an order of magnitude, and a potential preference for lower masses and higher accretion rates, which i) move them closer to the local correlations, and ii) might indicate that we are witnessing for the first time a widespread phase of very rapid accretion.
Abstract: 2406.18160
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Title:TeV $γ$-ray emission near globular cluster Terzan 5 as a probe of cosmic ray transport
View PDF HTML (experimental)Abstract:Cosmic rays travelling through interstellar space have their propagation directions repeatedly scattered by fluctuating interstellar magnetic fields. The nature of this scattering is a major unsolved problem in astrophysics, one that has resisted solution largely due to a lack of direct observational constraints on the scattering rate. Here we show that very high-energy $\gamma$-ray emission from the globular cluster Terzan 5, which has unexpectedly been found to be displaced from the cluster, presents a direct probe of this process. We show that this displacement is naturally explained by cosmic rays accelerated in the bow shock around the cluster propagating a finite distance before scattering processes re-orient enough of them towards Earth to produce a detectable $\gamma$-ray signal. The angular distance between the cluster and the signal places tight constraints on the scattering rate, which we show are consistent with a model whereby scattering is primarily due to excitation of magnetic waves by the cosmic rays themselves. The analysis method we develop here will make it possible to use sources with similarly displaced non-thermal X-ray and TeV $\gamma$-ray signals as direct probes of cosmic ray scattering across a range of Galactic environments.
Abstract: 2406.19279
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Title:Probing self-interacting ultra-high-energy neutrinos with cosmic 21-cm signal
View PDF HTML (experimental)Abstract:In this study, we investigate the constraints on secret self-interactions of neutrinos by examining the impact of radiative scattering of ultra-high-energy (UHE) neutrinos. These neutrinos are produced from the decay of superheavy dark matter and interact with the cosmic neutrino background (C$\nu$B). We explore how these interactions influence the 21-cm hydrogen signal during the cosmic dark ages and cosmic dawn, periods relatively free from astrophysical uncertainties, providing a clearer signal for studying non-standard neutrino interactions. By analyzing the global brightness temperature measurements, we constrain the scattering cross-section of UHE self-interacting neutrinos, determining the coupling constant $g$ to be within $\sim 10^{-4}$ to $\sim 10^{-3}$ for neutrino energies in the PeV to EeV range. Interestingly, these constraints are more competitive than those from existing astrophysical and collider experiments. As future 21-cm experiments focus on measuring brightness temperature across a wide range of redshifts from the cosmic dark ages to reionization, using the epoch of 21-cm to probe neutrino properties could provide crucial insights into dark matter and neutrino physics.
Abstract: 2406.18697
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Title:Cosmic Reionization in the JWST Era: Back to AGNs?
View PDF HTML (experimental)Abstract:Deep surveys with the James Webb Space Telescope (JWST) have revealed an emergent population of moderate-luminosity, broad-line active galactic nuclei (AGNs) at 4< z< 14 powered by accretion onto early massive black holes. The high number densities reported, together with the large Lyman-continuum (LyC) production efficiency and leakiness into the intergalactic medium (IGM) that are typical of UV-selected AGNs, lead us to reassess a scenario where AGNs are the sole drivers of the cosmic hydrogen/helium reionization process. Our approach is based on the assumptions, grounded in recent observations, that: (a) the fraction of broad-line AGNs among galaxies is around 10-15%; (b) the mean escape fraction of hydrogen LyC radiation is high, >80%, in AGN hosts and is negligible otherwise; and (c) internal absorption at 4 ryd or a steep ionizing EUV spectrum delay full reionization of HeII until z~2.8-3.0, in agreement with observations of the HeII Lyman-alpha forest. In our fiducial models: 1) hydrogen reionization is 99% completed by redshift z~5.3-5.5, and reaches its midpoint at z~6.5-6.7; (2) the integrated Thomson scattering optical depth to reionization is ~0.05, consistent with constraints from cosmic microwave background (CMB) anisotropy data; and (3) the abundant AGN population detected by JWST does not violate constraints on the unresolved X-ray background.
Abstract: 2406.19284
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Title:Interacting ultralight dark matter and dark energy and fits to cosmological data in a field theory approach
View PDF HTML (experimental)Abstract:The description of dark matter as a pressure-less fluid and of dark energy as a cosmological constant, both minimally coupled to gravity, constitutes the basis of the concordance $\Lambda\text{CDM}$ model. However, the concordance model is based on using equations of motion directly for the fluids with constraints placed on their sources, and lacks an underlying Lagrangian. In this work, we propose a Lagrangian model of two spin zero fields describing dark energy and dark matter with an interaction term between the two along with self-interactions. We study the background evolution of the fields as well as their linear perturbations, suggesting an alternative to $\Lambda$CDM with dark matter and dark energy being fundamental dynamical fields. The parameters of the model are extracted using a Bayesian inference tool based on multiple cosmological data sets which include those of Planck (with lensing), BAO, Pantheon, SH0ES, and WiggleZ. Using these data, we set constraints on the dark matter mass and the interaction strengths. Furthermore, we find that the model is able to alleviate the Hubble tension for some data sets while also resolving the $S_8$ tension.
Abstract: 2406.19287
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Title:Isotropy of cosmic rays beyond $10^{20}$ eV favors their heavy mass composition
View PDF HTML (experimental)Abstract:We report an estimation of the injected mass composition of ultra-high energy cosmic rays (UHECRs) at energies higher than 10 EeV. The composition is inferred from an energy-dependent sky distribution of UHECR events observed by the Telescope Array surface detector by comparing it to the Large Scale Structure of the local Universe. In the case of negligible extra-galactic magnetic fields the results are consistent with a relatively heavy injected composition at E ~ 10 EeV that becomes lighter up to E ~ 100 EeV, while the composition at E > 100 EeV is very heavy. The latter is true even in the presence of highest experimentally allowed extra-galactic magnetic fields, while the composition at lower energies can be light if a strong EGMF is present. The effect of the uncertainty in the galactic magnetic field on these results is subdominant.
Abstract: 2406.19440
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Title:Ultrahigh-energy neutrino searches using next-generation gravitational wave detectors at radio neutrino detectors: GRAND, IceCube-Gen2 Radio, and RNO-G
View PDF HTML (experimental)Abstract:Binary neutron star (BNS) mergers can be sources of ultrahigh-energy (UHE) cosmic rays and potential emitters of UHE neutrinos. The upcoming and current radio neutrino detectors like the Giant Radio Array for Neutrino Detection (GRAND), IceCube-Gen2 Radio, and the Radio Neutrino Observatory in Greenland (RNO-G) are projected to reach the required sensitivities to search for these neutrinos. In particular, in conjunction with the next-generation of gravitational wave (GW) detectors like Cosmic Explorer (CE) and Einstein Telescope (ET), GW-triggered stacking searches can be performed with the UHE neutrino detectors. In this work, we explore the prospects of such searches by implementing in our analysis an upper distance limit based on the sky-localization capabilities of the GW detectors from which meaningful triggers can be collected. We find that if each GW burst is associated with a total isotropic-equivalent energy of $\sim 10^{50} - 10^{51}$ erg emitted in UHE neutrinos, along with a corresponding beaming fraction of $1$\%, GRAND and IceCube-Gen2 Radio have a large probability ($\sim 99$\%) to detect a coincident neutrino event using the joint combination of CE+ET in a timescale of less than 15 years of operation for our fiducial choice of parameters. In case of nondetections, the parameter spaces can be constrained at $3\sigma$ level in similar timescales of operation. We also highlight and discuss the prospects of such joint radio neutrino detector network, their importance, and their role in facilitating synergic GW and neutrino observations in the next era of multimessenger astrophysics.
Abstract: 2406.19443
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Title:Dynamics around supermassive black holes: Extreme mass-ratio inspirals as gravitational-wave sources
View PDF HTML (experimental)Abstract:Supermassive black holes and their surrounding dense stellar environments nourish a variety of astrophysical phenomena. We focus on the distribution of stellar-mass black holes around the supermassive black hole and the consequent formation of extreme mass-ratio inspirals (EMRIs). We derive a steady-state distribution, considering the effects of two-body scatterings and gravitational wave emission, and calculate the EMRI formation rate, eccentricity distribution and EMRI-to-plunge ratio. Our model predicts: (I) A stronger segregation than previously estimated at the outskirts of the sphere of influence (at $\sim0.01\rm pc$ to $2\rm pc$ for a Milky-way like galaxy). (II) An increased EMRI-to-plunge ratio, favoring EMRIs at galaxies where stellar-mass black holes are scarce. (III) A detection of about $2\times10^3$ resolvable EMRIs, with a signal-to-noise ratio above $20$, along a $4$ year LISA mission time. (IV) A confusion noise, induced by a cosmological population of unresolved EMRIs, reducing LISA sensitivity in the $1-10\ \rm mHz$ frequency range by up to a factor of $\approx3.5$, relative to the instrumental noise.
Abstract: 2406.19458
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Title:Dark Matter Coupled to Radiation: Limits from the Milky Way Satellites
View PDFAbstract:Interactions between dark matter (DM) and relativistic particles at early times suppress structure formation on small scales. In particular, the scattering process transfers heat and momentum from radiation to DM, ultimately reducing the abundance of low-mass DM halos and the dwarf galaxies they host. Herein, we derive limits on DM--photon and DM--neutrino scattering cross section using the Milky Way (MW) satellite galaxy population. We consider temperature-independent interactions parameterized by DM mass ($m_\chi$) and DM--radiation interaction cross section ($\sigma_{\chi\text{--}i}$, where $i$ represents the target species). By requiring that the linear matter power spectra are strictly less suppressed than in the case of a thermal-relic warm DM, we derive the following $95\%$ upper limits at $m_\chi=1$ MeV: $\sigma_{\chi\text{--}\gamma}<1.50\times10^{-38}\text{cm}^2$ and $\sigma_{\chi\text{--}\nu}<2.41\times10^{-38}\text{cm}^2$. Our bounds on $\sigma_{\chi\text{--}i}$ depend linearly on $m_\chi$ for $m_\chi \gtrsim 1~\mathrm{MeV}$ and improve upon previous limits by an order of magnitude. The mass dependence of our limit approaches $m_\chi^3$ at lower masses due to the effects of DM sound speed; at $m_{\chi}=100~\mathrm{keV}$, we arrive at an upper limit over three orders of magnitude more stringent than achieved in previous explorations. Upcoming dwarf galaxy surveys will further improve the sensitivity of similar analyses, complementing laboratory and indirect detection searches for DM--radiation interactions.
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