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ICRANet Newsletter



ICRANet Newsletter
Dicembre 2021 - Gennaio 2022





1. Deep Learning in Searching the Spectroscopic Redshift of Quasars

The new work co-authored by ICRANet scientists is published by MNRAS on January 19, 2022


Fig. 1. The chosen architecture of 1-dimensional of FNet to learn higher-order features hidden in the input flux. It slides the flux via convolutional layers of kernel size = 500, 200 and 15, respectively to search for the "global" and "local" patterns in the flux of quasars. The fully connected layers output the redshift. Left: The structure of a residual block, the input x goes through two convolutional layers as H(x) then add itself as H(x)+x, batch normalization is applied after each convolutional layer, and the activation function ReLU acts on the first batch normalization layer. Right: The entire structure: The flux goes through 24 residual blocks, the first 21 blocks have channel size 32, followed by three blocks of channel size 64, 32 and 16 respectively. The output of blocks then is flattened and passes three fully convolutional layers and eventually outputs the redshift. The rectified linear unit (ReLU) is applied after each fully connected layer.

Quasi-stellar radio sources (Quasars) are high-luminosity active galactic nuclei (AGN). There is a broad consensus that quasars are powered by a gaseous accretion disk around a supermassive black hole (SMBH) of ~106 - 109 solar mass. Because of their high luminosity, quasars have been observed up to redshifts z~8 when the universe formed its first structures, i.e., in the reionization epoch. It makes quasars a powerful tool to study the cosmic history and structure formation in the early universe and, specifically, probe the physics governing the SMBHs and their surrounding accretion disk, as the rapid growth of SMBHs occurs at redshifts z = 5-10. Regarding their existence in a wide range of redshifts, quasars, as the cosmology’s standard candle, can also be utilized to put more constraints on the cosmological parameters.
On the one hand, the massive volume of data of astrophysical surveys makes the procedure for visual inspection of each spectrum to classify and determine the redshift highly time-consuming. For example, the Sloan Digital Sky Survey IV (SDSS-IV) quasar catalog from Data Release 16 (DR16) of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), includes a "superset" of objects labelled as quasars containing 1440615 spectra.
On the other hand, the adapted automatic methods, that operate based on comparing each spectrum with a dataset of spectra, usually perform worse than visual inspection methods in classification tasks. Thus, implementing automated strategies with human–expert precision is of great importance.


Fig. 2. The accuracy of prediction vs. Δ𝜈. The red solid line and black dashed line represent the accuracy of the FNet and QuasarNE, respectively, for DR16Q sample. The blue solid line and grey dashed line represent the accuracy of the FNet and QuasarNET, respectively, for DR16Q sample when DR12Q is excluded. The green dashed lines shows the accuracy of FNet for 5,190 visually inspected sources in DR16Q when QuasarNET fails to estimate.

Over the last few years, machine learning (ML) and deep learning (DL) algorithms have become increasingly popular in astronomy and astrophysics. They are using various recognition patterns and are able to identify the spectral features of astrophysical objects such as emission/absorption lines, spectral breaks, and flux correlations, and perform the classification and redshift determination as accurate as the visual inspection.
With the goal to estimate the redshift of quasars in Sloan Digital Sky Survey IV (SDSS-IV) catalog from DR16 quasar-only (DR16Q) of eBOSS on a broad range of signal-to-noise ratios, the group of researchers which includes ICRANet scientists has developed a new tool, the FNet. FNet is a 1–dimensional convolutional neural network (CNN) with a residual neural network (ResNet) structure. This network has 24 convolutional layers and the ResNet structure with different kernel sizes of 500, 200, and 15, which makes it to discover the "local" and "global" patterns, as well as correlations of fluxes in a different wavelength, in the whole sample of spectra by a self-learning procedure; see Fig. 1. It reaches the accuracy of 97.0 % for the velocity difference for redshift, | Δ𝜈 |< 6000 km/s and 98.0% for | Δ𝜈 | <12000 km/s. Here Δ𝜈 = c (Z-Z_VI)/(1+ZVI) is the velocity difference from redshift, c is the speed of light, Z_VI is the redshift from the visually inspected quasar sample, and Z is the predicted redshift.
While QuasarNET, which is a standard CNN adopted in the SDSS routine and is constructed by 4 convolutional layers (no ResNet structure), with kernel sizes of 10, to measure the redshift via identifying seven emission lines (local patterns), fails in estimating redshift of ∼ 1.3% of visually inspected quasars in DR16Q catalog, and it gives 97.8% for | Δ𝜈 |< 6000 km/s and 97.9 % for | Δ𝜈 |< 12000 km/s; see Fig 2. FNet is applicable for a wider range of SDSS spectra, especially for those missing the clear emission lines, which is necessary for other standard methods to work. These properties of FNet, together with the fast predictive power of machine learning, allow it to be a more accurate alternative for the pipeline redshift estimator and can make it practical in the upcoming catalogs to reduce the number of spectra to inspect visually.
The paper by F. Rastegar Nia, M. T. Mirtorabi, R. Moradi, A. Vafaei. Sadr, Y. Wang «Deep learning in searching the spectroscopic redshift of quasars» is published in Monthly Notices of the Royal Astronomical Society on 19 January 2022.
Link: https://doi.org/10.1093/mnras/stac076



2. Quarto Simposio Internazionale LeCosPA, online, 29 Novembre - 3 Dicembre 2021

Il quarto simposio internazionale "LeCosPA, Unity of Physics - From Plasma Wakefields to Black Holes" si è tenuto presso la National University di Taiwan e online dal 29 Novembre al 3 Dicembre 2021. Durante il meeting, si è discusso di svariati argomenti di grande importanza, dalla Luce Estrema, la Fisica ad alto campo, accelerazione al Plasma Wakefields, Universo Primitivo e Ultimo Universo, Astrofisica delle Particelle, Buchi Neri, Onde Gravitazionali, Teorie della Gravità Modificata, il Paradosso dell'Informazione e Buchi Neri Acustici.
Il 2 Dicembre 2021, il Prof. Ruffini, Direttore dell'ICRANet, ha presentato un talk intitolato "What is the role of the rotational energy extraction from Black Holes". Di seguito l'abstract:
We have demonstrated that the inner engine of GRBs and AGN produces high-energy emission by synchrotron radiation of electrons/protons that are accelerated in the rotating BH vicinity. The angular momentum of the Kerr BH and the surrounding magnetic field determine the energetics and characteristic radiation frequency, and their relative direction determines whether the motion of the electrons around the magnetic field lines follows a right-handed or a left-handed helix, and likewise the angular momentum inherited by the radiation.
Di seguito il link alla presentazione del Prof. Ruffini su YouTube:
https://www.youtube.com/watch?v=NaUJ7NqW3LQ


Fig. 3: il Prof. Ruffini durante il suo talk nel quarto Simposio Internazionale LeCosPA, Unity of Physics, 2 Dicembre 2021.



3. Eclissi Antartica e transiti meridiani, 4 Dicembre 2021

Il meeting "Eclissi Antartica e transiti meridiani. Esperimenti della meccanica celeste e astrofisica" si è tenuto virtualmente il 4 Dicembre 2021. L'evento è stato organizzato da un collaboratore dell'ICRANet, il Prof. Costantino Sigismondi, anche grazie al supporto di numerosi scienziati provenienti da tutto il mondo e al supporto dell'ICRANet stesso. Oltre al meeting virtuale, è stato organizzato un podcast per fornire a studenti e ricercatori uno spazio per il dibattito.
L'eclissi totale del Sole fornisce l'occasione di riconsiderare il diametro solare e le sue misure per il confronto con le effemeridi e con diametro standard. Il meeting è iniziato alle ore 10 di sabato 4 Dicembre con i saluti iniziali Prof. Sigismondi. Si è poi proseguito con importanti contributi su vari temi, come ad esempio "The consultation of ephemerides", "Eclipse and timing: the measurement uncertainty and its role for the eclipse", "Meridian transits and timing", "The first results from the obelisk - meridian of Saint Peter on the transit and the solar diameter", "The entry of the Sun in Scorpio and in Sagittarius 2021 at Saint Peter, with the Sun and the stars (preliminary results and calibration of the instrument)" e "The eclipse in Antarctica and the double eclipse of the year 810 in the letter by Dungal to Charlemagne".

Fig. 4: Il Sole in proiezione al meridiano di San Pietro il 24 Novembre 2021 Fig. 5: Incisione del Cesariano (1521) di Vitruvio, De Architectura, Libro IX capitolo VII con la frase della leggenda su Gerberto e il tesoro di Augusto Fig. 6: Il Sole al meridiano di san Pietro poco prima dell'eclissi meridiana il 26 Novembre 2021

Questa parte teorica è stata in seguito integrata con il materiale del podcast preparato dal Prof. Sigismondi. Il programma dell'evento e del podcast si trova al seguente link:
http://www.icranet.org/index.php?option=com_content&task=view&id=1399
Per la registrazione del meeting si prega di visitare il canale YouTube dell'ICRANet: https://www.youtube.com/watch?v=fLfBehXC-H4&t=696s



4. Meeting Amati Fest, 6-7 Dicembre 2021

In occasione della celebrazione del 50esimo anniversario del volume "Introducing the Black Hole" del Prof. Remo Ruffini e del Prof. John A. Wheeler, l'ICRANet ha organizzato un meeting online per discutere i risultati più recenti circa la comprensione dei Raggi Gamma e il loro "motore interno". In questa sede, ci si è focalizzati con particolare attenzione sulla relazione di Amati.


Fig. 7: L'afterglow del GRB 140114C osservato da banda radio e VHE.

Il meeting si è svolto presso la sede centrale dell'ICRANet a Pescara (Italia) e online dal 6 al 7 Dicembre 2021, oltre ad essere trasmesso in tutto il mondo in streaming sul canale YouTube dell'ICRANet. Il meeting si è aperto con i saluti del Prof. Remo Ruffini, Direttore dell'ICRANet, e del Prof. Lorenzo Amati. Durante l'evento, diversi scienziati hanno presentato i loro risultati più recenti, tra cui il Prof. Marco Tavani (Presidente dell'INAF), il Prof. Narek Sahakyan (Direttore della sede ICRANet in Armenia), il Prof. Michael Kramer (Direttore - Max-Planck-Institut für Radioastronomie), il Prof. Jorge Armando Rueda Hernandez (ICRANet, Università di Ferrara), il Prof. Carlo Luciano Bianco (ICRA, ICRANet), il Prof. Gregory Vereshchagin (ICRANet), il Prof. She Sheng Xue (ICRANet), il Prof. Carlos Raul Arguelles (ICRANet, CONICET, Universidad Nacional de La Plata), il Prof. Soroush Shakeri (ICRANet, Isfahan University of Technology), il Prof. Piero Rosati (University of Ferrara), il Prof. Razmik Mirzoyan (Max-Planck-Institute for Physics), il Prof. Cristiano Guidorzi (University of Ferrara), il Prof. Massimo Della Valle (ICRANet, INAF Osservatorio astronomico di Capodimonte), il Dr Luca Izzo (Osservatorio astronomico di Capodimonte), il Prof. Yifu Cai (University of Sciences and Technology of China), il Prof. Yefei Yuan (University of Sciences and Technology of China), Prof. Mimoza Hafizi (University of Tirana), il Prof. Claus Lämmerzahl (ZARM University of Bremen), il Prof. Stefano Scopel (CQUeST, Sogang University), il Prof. Simonetta Filippi (ICRA, University Campus Bio-medico of Rome), il Prof. Christian Cherubini (ICRA, University Campus Bio-medico of Rome), Prof. Stefano Ansoldi (University of Udine), il Prof. Aldo Treves (University of Insubria), il Prof. Francesco Haardt (University of Insubria), la Dr Ana Penacchioni (CONICET, Universidad Nacional de La Plata), la Dr Laura Marcela Becerra Bayona (ICRANet, Universidad Católica de Chile), Prof. Wang Yu (ICRANet), il Prof. Liang Li (ICRANet), il Prof. Rahim Moradi (ICRANet), il Dr Yerlan Aimuratov (ICRANet, Fesenkov Astrophysical Institute), il Dr Yunlong Zheng (ICRANet, University of Sciences and Technology of China), Eduar Antonio Becerra Vergara (ICRANet), la Dr Fatemeh Rastegar Nia (ICRANet, Alzahra University) e la Dr Sareh Eslamzadeh Askestani (University of Mazandaran).
Dopo questi interventi, c'è stato un lungo dibattito sulla scienza dei dati e sui risultati presentati dagli scienziati partecipanti al meeting, i quali hanno senz'altro colto l'opportunità di avere interessanti scambi su questioni di grande importanza. Il meeting si è concluso martedì 7 Dicembre con i saluti del Prof. Remo Ruffini e del Prof. Lorenzo Amati.

Fig. 8: il Prof. Lorenzo Amati ed il Prof. Remo Ruffini durante il meeting Amati Fest. Fig. 9: Da sinistra a destra: il Prof. Luca Izzo, il Prof. Jorge Rueda, il Prof. Lorenzo Amati, il Prof. Remo Ruffini, il Prof. Rahim Moradi, il Prof. Liang Li ed il Prof Wang Yu, presso la sede ICRANet di Pescara durante il meeting Amati Fest.



5. Visite scientifiche presso il centro ICRANet di Pescara

  • Prof. Lorenzo Amati
    INAF - Osservatorio di Astrofisica e Scienza dello Spazio
    6-7 Dicembre 2021

  • Prof. Jorge Armando Rueda Hernandez
    ICRA, ICRANet e Università di Ferrara
    6-7 Dicembre 2021

  • Prof. Luca Izzo
    Osservatorio di Capodimonte - Italia
    6-7 Dicembre 2021

Prof. Lorenzo Amati Prof. Jorge Armando Rueda Hernandez Prof. Luca Izzo

Durante la loro visita, questi scienziati hanno avuto l'opportunità di discutere le loro ricerche scientifiche e di avere interessanti scambi con gli altri ricercatori dell'ICRANet e da diverse parti del mondo. Il 6 e il 7 Dicembre 2021, questi scienziati hanno anche partecipato al meeting Amati Fest presso la sede centrale dell'ICRANet a Pescara (Italia).



6. Pubblicazioni recenti

J. A. Rueda and R. Ruffini, The quantum emission of an alive black hole, published in International Journal of Modern Physics D VOL. 30, NO. 14.
A long march of 50 years of successive theoretical progress and new physics discovered using observations of gamma-ray bursts has finally led to the formulation of an efficient mechanism able to extract the rotational energy of a Kerr black hole to power these most energetic astrophysical sources and active galactic nuclei. We here present the salient features of this long-sought mechanism, based on gravito-electrodynamics, and which represents an authentic shift of paradigm of black holes as forever "alive" astrophysical objects.
This essay is awarded third prize in the 2021 Essay Competition of the Gravity Research Foundation.
DOI: https://doi.org/10.1142/S0218271821410030


F. Rastegar Nia, M. T. Mirtorabi, R. Moradi, A. Vafaei Sadr, Y. Wang, Deep learning in searching the spectroscopic redshift of quasars, published in Monthly Notices of the Royal Astronomical Society on January 19, 2022.
Studying the cosmological sources at their cosmological rest-frames is crucial to track the cosmic history and properties of compact objects. In view of the increasing data volume of existing and upcoming telescopes/detectors, we here construct a 1–dimensional convolutional neural network (CNN) with a residual neural network (ResNet) structure to estimate the redshift of quasars in Sloan Digital Sky Survey IV (SDSS-IV) catalog from DR16 quasar-only (DR16Q) of eBOSS on a broad range of signal-to-noise ratios, named FNet. Owing to its 24 convolutional layers and the ResNet structure with different kernel sizes of 500, 200 and 15, FNet is able to discover the ‘local’ and ‘global’ patterns in the whole sample of spectra by a self-learning procedure. It reaches the accuracy of 97.0 per cent for the velocity difference for redshift, |Δν|<6000 km s−1 and 98.0 per cent for |Δν|<12000 km s−1. While QuasarNET, which is a standard CNN adopted in the SDSS routine and is constructed by 4 convolutional layers (no ResNet structure), with kernel sizes of 10, to measure the redshift via identifying seven emission lines (local patterns), fails in estimating redshift of ∼1.3 per cent of visually inspected quasars in DR16Q catalog, and it gives 97.8 per cent for |Δν|<6000 km s−1 and 97.9 per cent for |Δν|<12000 km s−1. Hence, FNet provides similar accuracy to QuasarNET, but it is applicable for a wider range of SDSS spectra, especially for those missing the clear emission lines exploited by QuasarNET. These properties of FNet, together with the fast predictive power of machine learning, allow FNet to be a more accurate alternative for the pipeline redshift estimator and can make it practical in the upcoming catalogs to reduce the number of spectra to visually inspect.
LINK: https://doi.org/10.1093/mnras/stac076


Davood Rafiei Karkevandi, Soroush Shakeri, Violetta Sagun, and Oleksii Ivanytskyi, Bosonic dark matter in neutron stars and its effect on gravitational wave signal, published in Phys. Rev. D 105, 023001 on January 3, 2022.
We study an impact of self-interacting bosonic dark matter (DM) on various observable properties of neutron stars (NSs). The analysis is performed for asymmetric DM with masses from few MeV to GeV, the self-coupling constant of order and various DM fractions. Allowing a mixture between DM and baryonic matter, the formation of a dense DM core or an extended dark halo has been explored. We find that both distribution regimes crucially depend on the mass and fraction of DM for sub-GeV boson masses in the strong coupling regime. From the combined analysis of the mass-radius relation and the tidal deformability of compact stars including bosonic DM, we set a stringent constraint on DM fraction. We conclude that observations of 2 M⊙ NSs together with Λ 1.4 ≤ 580 constraint, set by LIGO/Virgo Collaboration, favor sub-GeV DM particles with low fractions below ∼5%.
LINK: https://doi.org/10.1103/PhysRevD.105.023001


Sareh Eslamzadeh, Javad T. Firouzjaee, Kourosh Nozari, Radiation from Einstein-Gauss-Bonnet de Sitter black hole via tunneling process, accepted for publication on EPJC on January 4, 2022.
In this paper, we probe in novel 4D Einstein-Gauss-Bonnet (EGB) black hole and its thermodynamics. We illustrate the three asymptotically 4D EGB spacetime as an asymptotically flat, de Sitter, and Anti-de Sitter. Also, we apply the tunneling of the massless particles from the event horizon of 4D EGB gravity and we investigate the correlation between the emission modes and temperature of the event horizon. In asymptotically flat spacetime, the existence of the coupling constant alone constructs the regular spacetime, the radiation deviates from the pure thermal, and the temperature of the black hole horizon would be finite in the final stage of the black hole evaporation. If we consider the 4D ds-EGB structure, then we will have three horizons in the specific mass range of the black hole. By carefully examining the temperature of the black hole and cosmological horizons with the tunneling of the massless particles from these horizons. As a result, the evolution of these temperatures is in direction of the remaining rest mass with the probably same temperature for black hole and cosmological horizon. In addition, the exciting result is that temperature behaviors exactly match with the temperature behaviors of a regular black hole in Lovelock gravity in a higher dimension. This confirms the bypassing of EGB in four dimensions of spacetime from the Lovelock gravity in higher dimensions.
LINK: https://doi.org/10.1140/epjc/s10052-022-09992-6


Yunis, Rafael; Argüelles, Carlos R.; Scóccola, Claudia G.; López Nacir, Diana; Giordano, Gastón, Self-Interacting Dark Matter in Cosmology: accurate numerical implementation and observational constraints, accepted for publication on JCAP (24 January 2022).
This paper presents a systematic and accurate treatment of the evolution of cosmological perturbations in self-interacting dark matter models, for particles which decoupled from the primordial plasma while relativistic. We provide a numerical implementation of the Boltzmann hierarchies developed in a previous paper [JCAP, 09 (2020) 041] in a publicly available Boltzmann code and show how it can be applied to realistic DM candidates such as sterile neutrinos either under resonant or non-resonant production mechanisms, and for different field mediators. At difference with traditional fluid approximations - also known as a c_eff − c_vis parametrizations- our approach follows the evolution of phase-space perturbations under elastic DM interactions for a wide range of interaction models, including the effects of late kinetic decoupling. Finally, we analyze the imprints left by different self interacting models on linear structure formation, which can be constrained using Lyman-α forest and satellite counts. We find new lower bounds on the particle mass that are less restrictive than previous constraints.
ArXiv: https://arxiv.org/abs/2108.02657


MAGIC collaboration, Search for Very High-energy Emission from the Millisecond Pulsar PSR J0218+4232, published in ApJ, Volume 922, Number 2 on December 3, 2021.
PSR J0218+4232 is one of the most energetic millisecond pulsars known and has long been considered as one of the best candidates for very high-energy (VHE; >100 GeV) γ-ray emission. Using 11.5 yr of Fermi Large Area Telescope (LAT) data between 100 MeV and 870 GeV, and ~90 hr of Major Atmospheric Gamma Imaging Cherenkov (MAGIC) observations in the 20 GeV to 20 TeV range, we searched for the highest energy γ-ray emission from PSR J0218+4232. Based on the analysis of the LAT data, we find evidence for pulsed emission above 25 GeV, but see no evidence for emission above 100 GeV (VHE) with MAGIC. We present the results of searches for γ-ray emission, along with theoretical modeling, to interpret the lack of VHE emission. We conclude that, based on the experimental observations and theoretical modeling, it will remain extremely challenging to detect VHE emission from PSR J0218+4232 with the current generation of Imaging Atmospheric Cherenkov Telescopes, and maybe even with future ones, such as the Cherenkov Telescope Array.
LINK: https://doi.org/10.3847/1538-4357/ac20d7


MAGIC collaboration, Observation of the Gamma-Ray Binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS Telescopes, published in ApJ, Volume 923, Number 2 on December 24, 2021.
The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the Hα emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 ± 4.4 days is reported, consistent with the period of 317.3 ± 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical Hα parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems.
LINK: https://doi.org/10.3847/1538-4357/ac29b7
 
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