Abstracts of Interest
Selected by:
Ryan Burley
Abstract: 2208.01630
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Title:JWST reveals a population of ultra-red, flattened disk galaxies at 2<z<6 previously missed by HST
Download PDFAbstract: With just a month of data, JWST is already transforming our view of the Universe, revealing and resolving starlight in unprecedented populations of galaxies. Although ``HST-dark" galaxies have previously been detected at long wavelengths, these observations generally suffer from a lack of spatial resolution which limits our ability to characterize their sizes and morphologies. Here we report on a first view of starlight from a subset of the HST-dark population that are bright with JWST/NIRCam (4.4$\mu$m<24.5mag) and very faint or even invisible with HST ($<$1.6$\mu$m). In this Letter we focus on a dramatic and unanticipated population of physically extended galaxies ($\gtrsim$0.17''). These 12 galaxies have photometric redshifts $2<z<6$, high stellar masses $M_{\star}\gtrsim 10^{10}~M_{\odot}$, and significant dust-attenuated star formation. Surprisingly, the galaxies have elongated projected axis ratios at 4.4$\mu$m, suggesting that the population is disk-dominated or prolate. Most of the galaxies appear red at all radii, suggesting significant dust attenuation throughout. We refer to these red, disky, HST-dark galaxies as Ultra-red Flattened Objects (UFOs). With $r_e$(F444W)$\sim1-2$~kpc, the galaxies are similar in size to compact massive galaxies at $z\sim2$ and the cores of massive galaxies and S0s at $z\sim0$. The stellar masses, sizes, and morphologies of the sample suggest that some could be progenitors of lenticular or fast-rotating galaxies in the local Universe. The existence of this population suggests that our previous censuses of the universe may have missed massive, dusty edge-on disks, in addition to dust-obscured starbursts.
Abstract: 2208.01226
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Title:Neutrinos from near and far: Results from the IceCube Neutrino Observatory
Download PDFAbstract: Instrumenting a gigaton of ice at the geographic South Pole, the IceCube Neutrino Observatory has been at the forefront of groundbreaking scientific discoveries over the past decade. These include the observation of a flux of TeV-PeV astrophysical neutrinos, detection of the first astrophysical neutrino on the Glashow resonance and evidence of the blazar TXS 0506+056 as the first known astronomical source of high-energy neutrinos. Several questions, however, remain, pertaining to the precise origins of astrophysical neutrinos, their production mechanisms at the source and in Earth's atmosphere and in the context of physics beyond the Standard Model. This proceeding highlights some of our latest results, from new constraints on neutrino interactions and oscillations to the latest measurements of the astrophysical neutrino flux and searches for their origins to future prospects with IceCube-Gen2.
Abstract: 2208.01189
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Title:Investigation of the broadband emission of the gamma-ray binary HESS J0632+057 using an intrabinary shock model
Download PDFAbstract: We investigated a wealth of X-ray and gamma-ray spectral energy distribution (SED) and multi-band light curve (LC) data of the gamma-ray binary HESS J0632+057 using a phenomenological intrabinary shock (IBS) model. Our baseline model assumes that the IBS is formed by colliding winds from a putative pulsar and its Be companion, and particles accelerated in the IBS emit broadband radiation via synchrotron (SY) and inverse-Compton upscattering (ICS) processes. Adopting the latest orbital solution and system geometry (Tokayer et al. 2021), we reproduced the global X-ray and TeV LC features, two broad bumps at $\phi \sim 0.3$ and $\sim0.7$, with the SY and ICS model components. We found these TeV LC peaks originate from ICS emission caused by the enhanced seed photon density near periastron and superior conjunction or Doppler-beamed emission of bulk-accelerated particles in the IBS at inferior conjunction. While our IBS model successfully explained most of the observed SED and LC data, we found that phase-resolved SED data in the TeV band require an additional component associated with ICS emission from pre-shock particles (produced by the pulsar wind). This finding indicates a possibility of delineating the IBS emission components and determining the bulk Lorentz factors of the pulsar wind at certain orbital phases.
Abstract: 2208.01075
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Title:Constraints on the very high energy gamma-ray emission from short GRBs with HAWC
Download PDFAbstract: Many gamma-ray bursts (GRBs) have been observed from radio wavelengths, and a few at very-high energies (VHEs, > 100GeV). The HAWC gamma-ray observatory is well suited to study transient phenomena at VHEs due to its large field of view and duty cycle. These features allow for searches of VHE emission and can probe different model assumptions of duration and spectra. In this paper, we use data collected by HAWC between December 2014 and May 2020 to search for emission in the energy range from 80 to 800 GeV coming from a sample 47 short GRBs that triggered the Fermi, Swift and Konus satellites during this period. This analysis is optimized to search for delayed and extended VHE emission within the first 20 s of each burst. We find no evidence of VHE emission, either simultaneous or delayed, with respect to the prompt emission. Upper limits (90% confidence level) derived on the GRB fluence are used to constrain the synchrotron self-Compton forward-shock model. Constraints for the interstellar density as low as $10^{-2}$ cm$^{-3}$ are obtained when assuming z=0.3 for bursts with the highest keV-fluences such as GRB 170206A and GRB 181222841. Such a low density makes observing VHE emission mainly from the fast cooling regime challenging.
Abstract: 2208.01207
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Title:Bremsstrahlung from the Cosmic Neutrino Background
Download PDFAbstract: In this paper we discuss a detection method for the Cosmic Neutrino Background using bremsstrahlung from a neutrino scattering process which has no kinematic threshold, does not rely on a resonance and would in principle allow to measure the velocity distribution of the relic neutrinos. As a concrete example we calculate the rate for solar neutrinos scattering from a relic neutrino emitting a photon. We also provide the energy and angular distributions of the emitted photons.
Abstract: 2208.00838
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Title:Implications of multiwavelength spectrum on cosmic-ray acceleration in blazar TXS 0506+056
Download PDFAbstract: The MAGIC collaboration has recently analyzed data from a long-term multiwavelength campaign of the $\gamma$-ray blazar TXS 0506+056. In December 2018, it was flaring in the very-high-energy (VHE; $E>100$ GeV) $\gamma$-ray band, but no simultaneous neutrino event was detected. We explore prospects for detecting $\gamma$-rays and neutrinos of hadronic origin, produced both inside and outside the jet of TXS 0506+056, while coherently modeling the observed spectral energy distribution (SED) and neutrino flux upper limits. We constrain the neutrino flux through the restriction from observed X-ray flux on the secondary radiation due to hadronic cascade. We propagate the escaping ultra-high-energy cosmic rays (UHECRs; $E\gtrsim0.1$ EeV) in a random, turbulent extragalactic magnetic field (EGMF). The leptonic emission from the jet dominates the GeV range, whereas the cascade emission from CR interactions in the jet contributes substantially to the X-ray and VHE range. The line-of-sight cosmogenic $\gamma$ rays from UHECRs produce a hardening in the VHE range of the SED. Neutrino signal from the jet showed little or no variability during the MAGIC campaign. Therefore, we infer that the correlation between VHE $\gamma$-rays and neutrino flare is minimal. The luminosity in CRs limits the cosmogenic $\gamma$-ray flux, which, in turn, bounds the RMS value of the EGMF to $\gtrsim 10^{-5}$ nG. The cosmogenic neutrino flux is lower than the IceCube-Gen2 detection potential for 10 yrs of observation. VHE $\gamma$-ray variability should arise from an increased activity inside the jet. Upcoming $\gamma$-ray imaging telescopes, such as the CTA, will be able to constrain the cosmogenic $\gamma$-ray component in the SED of TXS 0506+056. Detecting a steady flux at multi-TeV energies will validate blazars as unambiguous sources of UHECRs.
Abstract: 2208.00159
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Title:The scientific payload of the Ultraviolet Transient Astronomy Satellite (ULTRASAT)
Download PDFAbstract: The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is a space-borne near UV telescope with an unprecedented large field of view (200 sq. deg.). The mission, led by the Weizmann Institute of Science and the Israel Space Agency in collaboration with DESY (Helmholtz association, Germany) and NASA (USA), is fully funded and expected to be launched to a geostationary transfer orbit in Q2/3 of 2025. With a grasp 300 times larger than GALEX, the most sensitive UV satellite to date, ULTRASAT will revolutionize our understanding of the hot transient universe, as well as of flaring galactic sources. We describe the mission payload, the optical design and the choice of materials allowing us to achieve a point spread function of ~10arcsec across the FoV, and the detector assembly. We detail the mitigation techniques implemented to suppress out-of-band flux and reduce stray light, detector properties including measured quantum efficiency of scout (prototype) detectors, and expected performance (limiting magnitude) for various objects.
Abstract: 2208.00107
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Title:CRPropa 3.2 -- an advanced framework for high-energy particle propagation in extragalactic and galactic spaces
Download PDFAbstract: The landscape of high- and ultra-high-energy astrophysics has changed in the last decade, largely due to the inflow of data collected by large-scale cosmic-ray, gamma-ray, and neutrino observatories. At the dawn of the multimessenger era, the interpretation of these observations within a consistent framework is important to elucidate the open questions in this field. CRPropa 3.2 is a Monte Carlo code for simulating the propagation of high-energy particles in the Universe. This version represents a major leap forward, significantly expanding the simulation framework and opening up the possibility for many more astrophysical applications. This includes, among others: efficient simulation of high-energy particles in diffusion-dominated domains, self-consistent and fast modelling of electromagnetic cascades with an extended set of channels for photon production, and studies of cosmic-ray diffusion tensors based on updated coherent and turbulent magnetic-field models. Furthermore, several technical updates and improvements are introduced with the new version, such as: enhanced interpolation, targeted emission of sources, and a new propagation algorithm (Boris push). The detailed description of all novel features is accompanied by a discussion and a selected number of example applications.
Abstract: 2208.00092
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Title:An Ocean Expedition by the Galileo Project to Retrieve Fragments of the First Large Interstellar Meteor CNEOS 2014-01-08
Download PDFAbstract: The earliest confirmed interstellar object, `Oumuamua, was discovered in the Solar System by Pan-STARRS in 2017, allowing for a calibration of the abundance of interstellar objects of its size $\sim 100\;$ m. This was followed by the discovery of Borisov, which allowed for a similar calibration of its size $\sim 0.4 - 1 \mathrm{\; km}$. One would expect a much higher abundance of significantly smaller interstellar objects, with some of them colliding with Earth frequently enough to be noticeable. Based on the CNEOS catalog of bolide events, we identified in 2019 the meteor detected at 2014-01-08 17:05:34 UTC as originating from an unbound hyperbolic orbit with 99.999\% confidence. In 2022, the U.S. Department of Defense has since verified that "the velocity estimate reported to NASA is sufficiently accurate to indicate an interstellar trajectory," making the object the first detected interstellar object and the first detected interstellar meteor. Here, we discuss the dynamical and compositional properties of CNEOS 2014-01-08, and describe our plan for an expedition to retrieve meteoritic fragments from the ocean floor.
Abstract: 2208.00892
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Title:Crewed Missions to Mars: Modeling the Impact of Astrophysical Charged Particles on Astronauts and Assessing Health Effects
Download PDFAbstract: The impact of exposure to astrophysical ionizing radiation on astronaut health is one of the main concerns in planning crewed missions to Mars. Astronauts will be exposed to energetic charged particles from Galactic and Solar origin for a prolonged period with little protection from a thin spacecraft shield in transit and from the rarefied Martian atmosphere when on the surface. Adverse impacts on astronaut health include, for example, Acute Radiation Syndrome, damage to the nervous system, and increased cancer risk. Using a combination of radiation measurements and numerical modeling with the GEANT4 package, we calculate the distribution of radiation dose in various organs of the human body for various expected scenarios simulated with a model human phantom. We rely on medical studies to assess the impact of enhanced levels of radiation dose on various physiological systems and on the overall health of astronauts. We suggest mitigation strategies such as improved ways of shielding and dietary supplements, and make recommendations for the safety of astronauts in future crewed missions to Mars.
Abstract: 2207.14141
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Title:Possible discovery of Calvera's supernova remnant
Download PDFAbstract: We report the discovery of a ring of low surface brightness radio emission around the Calvera pulsar, a high Galactic latitude, isolated neutron star, in the LOFAR Two-metre Sky Survey (LoTSS). It is centered at $\alpha=14\mathrm{h}11\mathrm{m}12.6\mathrm{s}$, $\delta=+79^\mathrm{o}23'15"$, has inner and outer radii of $14.2'$ and $28.4'$, and an integrated flux density at 144 MHz of $1.08\pm0.15$ Jy. The ring center is offset by $4.9'$ from the location of the Calvera pulsar. H$\alpha$ observations with the Isaac Newton Telescope show no coincident optical emission, but do show a small ($\sim20"$) optical structure internal to the ring. We consider three possible interpretations for the ring: that it is an H~II region, a supernova remnant (SNR), or an Odd Radio Circle (ORC). The positional coincidence of the ring, the pulsar, and an X-ray-emitting non-equilibrium ionisation plasma previously detected, lead us to prefer the SNR interpretation. If the source is indeed a SNR and its association with the Calvera pulsar is confirmed, then Calvera's SNR, or G118.4+37.0, will be one of few SNRs in the Galactic halo.
Abstract: 2207.13838
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Title:Cosmic Ray Interstellar Propagation Tool using Itô Calculus (criptic): software for simultaneous calculation of cosmic ray transport and observational signatures
Download PDFAbstract: We present criptic, the Cosmic Ray Interstellar Propagation Tool using Itô Calculus, a new open-source software package to simulate the propagation of cosmic rays through the interstellar medium and to calculate the resulting observable non-thermal emission. Criptic solves the Fokker-Planck equation describing transport of cosmic rays on scales larger than that on which their pitch angles become approximately isotropic, and couples this to a rich and accurate treatment of the microphysical processes by which cosmic rays in the energy range $\sim$MeV to $\sim$PeV lose energy and produce emission. Criptic is deliberately agnostic as to both the cosmic ray transport model and the state of the background plasma through which cosmic rays travel. It can solve problems where cosmic rays stream, diffuse, or perform arbitrary combinations of both, and the coefficients describing these transport processes can be arbitrary functions of the background plasma state, the properties of the cosmic rays themselves, and local integrals of the cosmic ray field itself (e.g., the local cosmic ray pressure or pressure gradient). The code is parallelised using a hybrid OpenMP-MPI paradigm, allowing rapid calculations exploiting multiple cores and nodes on modern supercomputers. Here we describe the numerical methods used in the code, our treatment of the microphysical processes, and the set of code tests and validations we have performed.
Abstract: 2207.13896
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Title:Escape of cosmic rays from perpendicular shocks in the circumstellar magnetic field
Download PDFAbstract: We investigate the escape process of cosmic rays (CRs) from perpendicular shock regions of a spherical shock propagating to a circumstellar medium with the Parker-spiral magnetic field. The diffusive shock acceleration in perpendicular shocks of supernova remnants (SNRs) is expected to accelerate CRs up to PeV without upstream magnetic field amplification. Red supergiants (RSGs) and Wolf-Rayet (WR) stars are considered as progenitors in this work. We perform test particle simulations to investigate the escape process and escape-limited maximum energy without magnetic field amplification in the upstream region, where the magnetic field strength and rotation period expected from observations of RSGs and WR stars are used. We show that particles escape to the far upstream region while moving along the equator or poles and the maximum energy is about $10-100~{\rm TeV}$ when SNRs propagate to free wind regions of RSGs and WR stars. In most cases, the escape-limited maximum energy is given by the potential difference between the equator and pole. If progenitors are oblique rotators and SNRs are in the early phase just after the supernova explosion, the escape-limited maximum energy is limited by the half wavelength of the wavy current sheet. In addition, for RSGs, we show that the luminosity of CRs accelerated in the wind region is sufficient to supply the observed CR flux above $10~{\rm TeV}$ if a strong magnetic field strength is sustained in most RSGs. In terms of the CR luminosity, SNRs propagating to the free wind of WR stars can contribute to PeV CRs. As long as no magnetic field amplification works around SNR shocks, the maximum energy is decided by the magnetic field strength in the wind region, which depends on the rotation period, stellar wind, and surface magnetic field of RSGs and WR stars. Therefore, we need to observe these quantities to understand the origin of CRs.
Abstract: 2207.13704
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Title:The Eclipse Megamovie Project (2017)
Download PDFAbstract: The total solar eclipse of August 21, 2017, crossed the whole width of North America, the first occasion for this during the modern age of consumer electronics. Accordingly, it became a great opportunity to engage the public and to enlist volunteer observers with relatively high-level equipment; our program ("Eclipse Megamovie") took advantage of this as a means of creating a first-ever public database of such eclipse photography. This resulted in a large outreach program, involving many hundreds of individuals, supported almost entirely on a volunteer basis and with the institutional help of Google, the Astronomical Society of the Pacific, and the University of California, Berkeley. The project home page is \url{this http URL}, which contains the movie itself. We hope that our comments here will help with planning for similar activities in the total eclipse of April 8, 2024.
Abstract: 2207.13533
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Title:Features of the gamma-ray pulsar halo HESS J1831$-$098
Download PDFAbstract: Gamma-ray pulsar halos are ideal indicators of cosmic-ray propagation in localized regions of the Galaxy and electron injection from pulsar wind nebulae. HESS~J1831$-$098 is a candidate pulsar halo observed by both H.E.S.S. and HAWC experiments. We adopt the flux map of the H.E.S.S. Galactic plane survey and the spectrum measurements of H.E.S.S. and \textit{Fermi}-LAT to study HESS~J1831$-$098. We find that HESS~J1831$-$098 meets all the criteria for a pulsar halo. The diffusion coefficient inside the halo and the conversion efficiency from the pulsar spin-down energy to the electron energy are both similar to the Geminga halo, a canonical pulsar halo. The injection spectrum can be well described by an exponentially-cutoff power law. However, the needed power-law term is very hard with $p\lesssim1$ if the diffusion coefficient is spatially and temporally independent. Considering the possible origins of the slow-diffusion environment, we adopt the two-zone diffusion model and the time-delayed slow-diffusion model. Both the models can interpret the H.E.S.S. and \textit{Fermi}-LAT results with a milder $p$. A modified injection time profile may have a similar effect.
Abstract: 2208.02247
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Title:$γ$ rays run on time
Download PDFAbstract: Significant absorption of radiation is usually accompanied by refraction. This is not the case for $\gamma$ rays travelling cosmic distances. We show that the real and imaginary parts of the refraction index are indeed commensurable, as they are related by dispersion relations, but when turning to physical observables, the (finite) optical depth is way larger than the (infinitesimal) time delay of the gamma rays relative to gravitational radiation. The numerically large factor solving the apparent contradiction is $E_\gamma/H_0$ arising from basic wave properties (Bouguer-Beer-Lambert law) and the standard cosmological model, respectively.
Abstract: 2208.01911
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Title:Cosmic Ray Measurements with IceCube and IceTop
Download PDFAbstract: IceCube is a cubic-kilometer Cherenkov detector in the deep ice at the geographic South Pole. The dominant event yield in the deep ice detector consists of penetrating atmospheric muons with energies above approximately 300 GeV, produced in cosmic ray air showers. In addition, the surface array, IceTop, measures the electromagnetic component and GeV muons of air showers. Hence, IceCube and IceTop yield unique opportunities to study cosmic rays with unprecedented statistics in great detail. We will present recent results of comic ray measurements from IceCube and IceTop. In this overview, we will highlight measurements of the energy spectrum of cosmic rays from 250 TeV up to the EeV range and their mass composition above 3 PeV. We will also report recent results from measurements of the muon content in air showers and discuss their consistency with predictions from current hadronic interaction models.
Abstract: 2208.00597
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Title:On irregularities in the cosmic ray spectrum of $10^{16}-10^{18}$ eV range
Download PDFAbstract: Small, medium and large arrays for the study of cosmic rays of ultra-high energies existing are aimed at obtaining information about our Galaxy and metagalactic space. Concretely search and study of astronomical objects, that forms flux of relativistic particles that fill outer space. The drift and interaction of such particles with magnetic field and shock waves taking place in interstellar space causes the same interest. The shape of the energy spectrum of cosmic rays in the energy range $10^{15}-10^{18}$ eV, where "knee" and "second knee" is observed, can be formed as a superposition of the partial spectra of various chemical elements. Verification of galactic models, using recent experimental spectral data, makes it possible to study the nature of the galactic and metagalactic components of cosmic rays. The paper presents the result of the energy spectrum of cosmic rays in the range $10^{16}-10^{18}$ eV measurements obtained at the Small Cherenkov array -- a part of the Yakutsk array.
Abstract: 2208.01722
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Title:The meaning of the Sky of Salamanca
Download PDFAbstract: After presenting the main characteristics of the Sky of Salamanca, we analyse whether what is represented in it is motivated by astrological or astronomical considerations. We will see that the astrological explanation based on the system of planetary houses described in Claudius Ptolemy's Tetrabiblos does not correspond to the planetary configuration we see in the salmantine vault. Finally, we will conclude that the astronomical interpretation of the Sky of Salamanca is justified by the representation of the Universe known in the 15th century according to the Almagest, by the placement of the stars in the constellations according to that work and by the dating of the painted planetary configuration, which circumstantial evidence places in August 1475.
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