arXiv subjects

S. Della Torre

Publications and source records attributed to S. Della Torre.

At least 37 records · Page 2Linked to original sources

arXiv2023

LiteBIRD Science Goals and Forecasts: A full-sky measurement of gravitational lensing of the CMB

We explore the capability of measuring lensing signals in $LiteBIRD$ full-sky polarization maps. With a $30$ arcmin beam width and an impressively low polarization noise of $2.16\,μ$K-arcmin, $LiteBIRD$ will be able to measure the full-sky polarization of the cosmic microwave background (CMB) very precisely. This unique sensitivity also enables the reconstruction of a nearly full-sky lensing map using only polarization data, even considering its limited capability to capture small-scale CMB anisotropies. In this paper, we investigate the ability to construct a full-sky lensing measurement in the presence of Galactic foregrounds, finding that several possible biases from Galactic foregrounds should be negligible after component separation by harmonic-space internal linear combination. We find that the signal-to-noise ratio of the lensing is approximately $40$ using only polarization data measured over $90\%$ of the sky. This achievement is comparable to $Planck$'s recent lensing measurement with both temperature and polarization and represents a four-fold improvement over $Planck$'s polarization-only lensing measurement. The $LiteBIRD$ lensing map will complement the $Planck$ lensing map and provide several opportunities for cross-correlation science, especially in the northern hemisphere.

astro-ph.CO↗

arXiv2023

LiteBIRD Science Goals and Forecasts: Improving Sensitivity to Inflationary Gravitational Waves with Multitracer Delensing

We estimate the efficiency of mitigating the lensing $B$-mode polarization, the so-called delensing, for the $LiteBIRD$ experiment with multiple external data sets of lensing-mass tracers. The current best bound on the tensor-to-scalar ratio, $r$, is limited by lensing rather than Galactic foregrounds. Delensing will be a critical step to improve sensitivity to $r$ as measurements of $r$ become more and more limited by lensing. In this paper, we extend the analysis of the recent $LiteBIRD$ forecast paper to include multiple mass tracers, i.e., the CMB lensing maps from $LiteBIRD$ and CMB-S4-like experiment, cosmic infrared background, and galaxy number density from $Euclid$- and LSST-like survey. We find that multi-tracer delensing will further improve the constraint on $r$ by about $20\%$. In $LiteBIRD$, the residual Galactic foregrounds also significantly contribute to uncertainties of the $B$-modes, and delensing becomes more important if the residual foregrounds are further reduced by an improved component separation method.

astro-ph.CO↗

arXiv2023

Tensor-to-scalar ratio forecasts for extended LiteBIRD frequency configurations

LiteBIRD is a planned JAXA-led CMB B-mode satellite experiment aiming for launch in the late 2020s, with a primary goal of detecting the imprint of primordial inflationary gravitational waves. Its current baseline focal-plane configuration includes 15 frequency bands between 40 and 402 GHz, fulfilling the mission requirements to detect the amplitude of gravitational waves with the total uncertainty on the tensor-to-scalar ratio, $δr$, down to $δr<0.001$. A key aspect of this performance is accurate astrophysical component separation, and the ability to remove polarized thermal dust emission is particularly important. In this paper we note that the CMB frequency spectrum falls off nearly exponentially above 300 GHz relative to the thermal dust SED, and a relatively minor high frequency extension can therefore result in even lower uncertainties and better model reconstructions. Specifically, we compare the baseline design with five extended configurations, while varying the underlying dust modeling, in each of which the HFT (High-Frequency Telescope) frequency range is shifted logarithmically towards higher frequencies, with an upper cutoff ranging between 400 and 600 GHz. In each case, we measure the tensor-to-scalar ratio $r$ uncertainty and bias using both parametric and minimum-variance component-separation algorithms. When the thermal dust sky model includes a spatially varying spectral index and temperature, we find that the statistical uncertainty on $r$ after foreground cleaning may be reduced by as much as 30--50 % by extending the upper limit of the frequency range from 400 to 600 GHz, with most of the improvement already gained at 500 GHz. We also note that a broader frequency range leads to better ability to discriminate between models through higher $χ^2$ sensitivity. (abridged)

astro-ph.CO↗

arXiv2023

Probing Cosmic Inflation with the LiteBIRD Cosmic Microwave Background Polarization Survey

LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background (CMB) polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2$μ$K-arcmin, with a typical angular resolution of 0.5$^\circ$ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions and synergies with other projects.

astro-ph.IM↗

arXiv2022

Spectra of Cosmic Ray Sodium and Aluminum and Unexpected Aluminum Excess

Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, $\bar{p}$, $e^{\pm}$, and nuclei (H-Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectra of CR sodium and aluminum up to $\sim$2 TV. Given their low solar system abundances, a significant fraction of each element is produced in fragmentations of heavier species, predominantly Ne, Mg, and Si. In this paper, we use precise measurements of the sodium and aluminum spectra by AMS-02 together with ACE-CRIS and Voyager 1 data to test their origin. We show that the sodium spectrum agrees well with the predictions made with the GalProp-HelMod framework, while aluminum spectrum shows a significant excess in the rigidity range from 2-7 GV. In this context, we discuss the origin of other low-energy excesses in Li, F, and Fe found earlier. The observed excesses in Li, F, and Al appear to be consistent with the local Wolf-Rayet (WR) stars hypothesis, invoked to reproduce anomalous $^{22}$Ne/$^{20}$Ne, $^{12}$C/$^{16}$O, and $^{58}$Fe/$^{56}$Fe ratios in CRs, while excess in Fe is likely connected with a past SN activity in the solar neighborhood. We also provide updated local interstellar spectra (LIS) of sodium and aluminum in the rigidity range from few MV to $\sim$2 TV. Our calculations employ the self-consistent GalProp-HelMod framework that has proved to be a reliable tool in deriving the LIS of CR $\bar{p}$, $e^{-}$, and nuclei $Z\le28$.

astro-ph.HE↗

arXiv2022

Polarization angle requirements for CMB B-mode experiments. Application to the LiteBIRD satellite

A methodology to provide the polarization angle requirements for different sets of detectors, at a given frequency of a CMB polarization experiment, is presented. The uncertainties in the polarization angle of each detector set are related to a given bias on the tensor-to-scalar ratio $r$ parameter. The approach is grounded in using a linear combination of the detector sets to obtain the CMB polarization signal. In addition, assuming that the uncertainties on the polarization angle are in the small angle limit (lower than a few degrees), it is possible to derive analytic expressions to establish the requirements. The methodology also accounts for possible correlations among detectors, that may originate from the optics, wafers, etc. The approach is applied to the LiteBIRD space mission. We show that, for the most restrictive case (i.e., full correlation of the polarization angle systematics among detector sets), the requirements on the polarization angle uncertainties are of around 1 arcmin at the most sensitive frequency bands (i.e., $\approx 150$ GHz) and of few tens of arcmin at the lowest (i.e., $\approx 40$ GHz) and highest (i.e., $\approx 400$ GHz) observational bands. Conversely, for the least restrictive case (i.e., no correlation of the polarization angle systematics among detector sets), the requirements are $\approx 5$ times less restrictive than for the previous scenario. At the global and the telescope levels, polarization angle knowledge of a few arcmins is sufficient for correlated global systematic errors and can be relaxed by a factor of two for fully uncorrelated errors in detector polarization angle. The reported uncertainty levels are needed in order to have the bias on $r$ due to systematics below the limit established by the LiteBIRD collaboration.

astro-ph.CO↗

arXiv2021

A Hint of a Low-Energy Excess in Cosmic-Ray Fluorine

Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, $\bar{p}$, $e^{\pm}$, and nuclei (H--O, Ne, Mg, Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectrum of CR fluorine up to $\sim$2 TV. Given its very low solar system abundance, fluorine in CRs is thought to be mostly secondary, produced in fragmentations of heavier species, predominantly Ne, Mg, and Si. Similar to the best-measured secondary-to-primary boron to carbon nuclei ratio that is widely used to study the origin and propagation of CR species, the precise fluorine data would allow the origin of Si-group nuclei to be studied independently. Meanwhile, the secondary origin of CR fluorine has never been tested in a wide energy range due to the lack of accurate CR data. In this paper, we use the first ever precise measurements of the fluorine spectrum by AMS-02 together with ACE-CRIS and Voyager 1 data to actually test this paradigm. Our detailed modeling shows an excess below 10 GV in the fluorine spectrum that may hint at a primary fluorine component. We also provide an updated local interstellar spectrum (LIS) of fluorine in the rigidity range from few MV to $\sim$2 TV. Our calculations employ the self-consistent GalProp-HelMod framework that has proved to be a reliable tool in deriving the LIS of CR $\bar{p}$, $e^{-}$, and nuclei $Z\le28$.

astro-ph.HE↗

arXiv2021

Inference of the Local Interstellar Spectra of Cosmic Ray Nuclei Z<=28 with the GalProp-HelMod Framework

Composition and spectra of Galactic cosmic rays (CRs) are vital for studies of high-energy processes in a variety of environments and on different scales, for interpretation of gamma-ray and microwave observations, disentangling possible signatures of new phenomena, and for understanding of our local Galactic neighborhood. Since its launch, AMS-02 has delivered outstanding quality measurements of the spectra of antiprotons, electrons, positrons, and nuclei: H-O, Ne, Mg, Si. These measurements resulted in a number of breakthroughs, however, spectra of heavier nuclei and especially low-abundance nuclei are not expected until later in the mission. Meanwhile, a comparison of published AMS-02 results with earlier data from HEAO-3-C2 indicate that HEAO-3-C2 data may be affected by undocumented systematic errors. Utilizing such data to compensate for the lack of AMS-02 measurements could result in significant errors. In this paper we show that a fraction of HEAO-3-C2 data match available AMS-02 measurements quite well and can be used together with Voyager 1 and ACE-CRIS data to make predictions for the local interstellar spectra (LIS) of nuclei that are not yet released by AMS-02. We are also updating our already published LIS to provide a complete set from H-Ni in the energy range from 1 MeV/nucleon to ~100-500 TeV/nucleon thus covering 8-9 orders of magnitude in energy. Our calculations employ the GalProp-HelMod framework that is proved to be a reliable tool in deriving the LIS of CR antiprotons, electrons, and nuclei H-O.

astro-ph.HE↗

arXiv2021

A discovery of a low-energy excess in cosmic-ray iron: an evidence of the past supernova activity in the Local Bubble

Since its launch, the Alpha Magnetic Spectrometer - 02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, $\bar{p}$, $e^{\pm}$, and nuclei, $_1$H-$_8$O, $_{10}$Ne, $_{12}$Mg, $_{14}$Si, which resulted in a number of breakthroughs. One of the latest long awaited surprises is the spectrum of $_{26}$Fe just published by AMS-02. Because of the large fragmentation cross section and large ionization energy losses, most of CR iron at low energies is local, and may harbor some features associated with relatively recent supernova (SN) activity in the solar neighborhood. Our analysis of new iron spectrum together with Voyager 1 and ACE-CRIS data reveals an unexpected bump in the iron spectrum and in the Fe/He, Fe/O, and Fe/Si ratios at 1-2 GV, while a similar feature in the spectra of He, O, Si, and in their ratios is absent, hinting at a local source of low-energy CRs. The found excess fits well with recent discoveries of radioactive $^{60}$Fe deposits in terrestrial and lunar samples, and in CRs. We provide an updated local interstellar spectrum (LIS) of iron in the energy range from 1 MeV nucleon$^{-1}$ to $\sim$10 TeV nucleon$^{-1}$. Our calculations employ the GalProp-HelMod framework that is proved to be a reliable tool in deriving the LIS of CR $\bar{p}$, $e^{-}$, and nuclei $Z\le28$.

astro-ph.HE↗

arXiv2019

Deciphering the local Interstellar spectra of secondary nuclei with GALPROP/HelMod framework and a hint for primary lithium in cosmic rays

Local interstellar spectra (LIS) of secondary cosmic ray (CR) nuclei, lithium, beryllium, boron, and partially secondary nitrogen, are derived in the rigidity range from 10 MV to ~200 TV using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. The lithium spectrum appears somewhat flatter at high energies compared to other secondary species that may imply a primary lithium component. Two propagation packages, GALPROP and HelMod, are combined to provide a single framework that is run to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. An iterative maximum-likelihood method is developed that uses GALPROP-predicted LIS as input to HelMod, which provides the modulated spectra for specific time periods of the selected experiments for the model-data comparison. The proposed LIS accommodate the low-energy interstellar spectra measured by Voyager 1, HEAO-3, and ACE/CRIS as well as the high-energy observations by PAMELA, AMS-02, and earlier experiments that are made deep in the heliosphere. The interstellar and heliospheric propagation parameters derived in this study are consistent with our earlier results for propagation of CR protons, helium, carbon, oxygen, antiprotons, and electrons.

astro-ph.HE↗

arXiv2018

Deciphering the local Interstellar spectra of primary cosmic ray species with HelMod

Local interstellar spectra (LIS) of primary cosmic ray (CR) nuclei, such as helium, oxygen, and mostly primary carbon are derived for the rigidity range from 10 MV to ~200 TV using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HelMod, are combined into a single framework that is used to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. The developed iterative maximum-likelihood method uses GALPROP-predicted LIS as input to HelMod, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The interstellar and heliospheric propagation parameters derived in this study are consistent with our prior analyses using the same methodology for propagation of CR protons, helium, antiprotons, and electrons. The resulting LIS accommodate a variety of measurements made in the local interstellar space (Voyager 1) and deep inside the heliosphere at low (ACE/CRIS, HEAO-3) and high energies (PAMELA, AMS-02).

astro-ph.HE↗

arXiv2018

HelMod in the works: from direct observations to the local interstellar spectrum of cosmic-ray electrons

The local interstellar spectrum (LIS) of cosmic-ray (CR) electrons for the energy range 1 MeV to 1 TeV is derived using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HelMod, are combined to provide a single framework that is run to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. An iterative maximum-likelihood method is developed that uses GALPROP-predicted LIS as input to HelMod, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The optimized HelMod parameters are then used to adjust GALPROP parameters to predict a refined LIS with the procedure repeated subject to a convergence criterion. The parameter optimization uses an extensive data set of proton spectra from 1997-2015. The proposed CR electron LIS accommodates both the low-energy interstellar spectra measured by Voyager 1 as well as the high-energy observations by PAMELA and AMS-02 that are made deep in the heliosphere; it also accounts for Ulysses counting rate features measured out of the ecliptic plane. The interstellar and heliospheric propagation parameters derived in this study agree well with our earlier results for CR protons, helium nuclei, and anti-protons propagation and LIS obtained in the same framework.

astro-ph.HE↗

arXiv2017

Solution of heliospheric propagation: unveiling the local interstellar spectra of cosmic ray species

Local interstellar spectra (LIS) for protons, helium and antiprotons are built using the most recent experimental results combined with the state-of-the-art models for propagation in the Galaxy and heliosphere. Two propagation packages, GALPROP and HelMod, are combined to provide a single framework that is run to reproduce direct measurements of cosmic ray (CR) species at different modulation levels and at both polarities of the solar magnetic field. To do so in a self-consistent way, an iterative procedure was developed, where the GALPROP LIS output is fed into HelMod that provides modulated spectra for specific time periods of selected experiments to compare with the data; the HelMod parameters optimization is performed at this stage and looped back to adjust the LIS using the new GALPROP run. The parameters were tuned with the maximum likelihood procedure using an extensive data set of proton spectra from 1997-2015. The proposed LIS accommodate both the low energy interstellar CR spectra measured by Voyager 1 and the high energy observations by BESS, Pamela, AMS-01, and AMS-02 made from the balloons and near-Earth payloads; it also accounts for Ulysses counting rate features measured out of the ecliptic plane. The found solution is in a good agreement with proton, helium, and antiproton data by AMS-02, BESS, and PAMELA in the whole energy range.

astro-ph.HE↗

arXiv2017

Propagation of Cosmic Rays in Heliosphere: the HelMod Model

The heliospheric modulation model \helmod{} is a two dimensional treatment dealing with the helio-colatitude and radial distance from Sun and is employed to solve the transport-equation for the GCR propagation through the heliosphere down to Earth. This work presents the current version 3 of the \helmod{} model and reviews how main processes involved in GCR propagation were implemented.~The treatment includes the so-called particle drift effects --~e.g., those resulting, for instance, from the extension of the neutral current sheet inside the heliosphere and from the curvature and gradient of the IMF --, which affect the transport of particles entering the solar cavity as a function of their charge sign.~The \helmod{} model is capable to provide modulated spectra which well agree within the experimental errors with those measured by AMS-01, BESS, PAMELA and AMS-02 during the solar cycles 23 and 24.~Furthermore, the counting rate measured by Ulysses at +/- 80degree of solar latitude and 1 to 5\,AU was also found in agreement with that expected by \helmod{} code version 3.

astro-ph.SR↗

arXiv2016

From Observations near the Earth to the Local Interstellar Spectra

Propagation of cosmic rays (CRs) from their sources to the observer is described mainly as plain diffusion at high energies, while at lower energies there are other physical processes involved, both in the interstellar space and in the heliosphere. The latter was a subject of considerable uncertainty until recently. New data obtained by several CR missions can be used to and the local interstellar spectra (LIS) of CR species that would significantly reduce the uncertainties associated with the heliospheric propagation. In this paper we present the LIS of CR protons and helium outside the heliospheric boundary. The proposed LIS are tuned to accommodate both, the low energy CR spectra measured by Voyager 1, and the high energy observations publicly released by BESS, Pamela, AMS-01 and AMS-02. The proton and helium LIS are derived by combining CR propagation in the Galaxy, as described by GALPROP, with the heliospheric modulation computed using the HelMod Monte Carlo Tool. The proposed LIS are tuned to reproduce the modulated spectra for both, high and low, levels of solar activity.

astro-ph.HE↗

arXiv2016

Results on Solar Physics from AMS-02

AMS-02 is a wide acceptance high-energy physics experiment installed on the International Space Station in May 2011 and operating continuously since then. Using the largest number of detected particles in space of any space-borne experiment, it performs precision measurements of galactic cosmic rays fluxes. Detailed time variation studies of Protons, Heliums, Electron and Positron fluxes were presented. The low-rigidity range exhibits a decreasing general trend strongly related to the increase of solar activity, as well local decreases associated with strong solar events.

astro-ph.HE↗

arXiv2016

HelMod: A Comprehensive Treatment of the Cosmic Ray Transport Through the Heliosphere

HelMod is a code evaluating the transport of Galactic cosmic rays through the inner heliosphere down to Earth. It is based on a 2-D Monte Carlo approach and includes a general description of the symmetric and antisymmetric parts of the diffusion tensor, thus, properly treating the particle drift effects. The model has been tuned in order to fit the data observed outside the ecliptic plane at several distances from the Earth and the spectra observed near the Earth for both, high and low solar activity levels. A stand-alone python module, fully compatible with GalProp, was developed for a comprehensive calculation of solar modulation effects, resulting in a newly suggested set of local interstellar spectra.

astro-ph.HE↗

arXiv2015

Cosmic Rays Propagation with HelMod: Difference between forward-in-time and backward-in-time approaches

The cosmic rays modulation inside the heliosphere is well described by a transport equation introduced by Parker in 1965. To solve this equation several approaches were followed in the past. Recently the Monte Carlo approach becomes widely used in force of his advantages with respect to other numerical methods. In the Monte Carlo approach, the transport equation is associated to a fully equivalent set of Stochastic Differential Equations. This set is used to describe the stochastic path of a quasi-particle from a source, e.g., the interstellar medium, to a specific target, e.g., a detector at Earth. In this work, we present both the Forward-in-Time and Backward-in-Time Monte Carlo solutions. We present an implementation of both algorithms in the framework of HelMod Code showing that the difference between the two approach is below 5\% that can be quoted as the systematic uncertain of the Method itself.

physics.space-ph↗