Search

Various particle accelerators operate in the space plasmas, filling the Galaxy with high-energy particles (primary cosmic rays). Reaching the Earth's atmosphere, these particles originate extensive air showers (EASs) consisting of millions of elementary particles (secondary cosmic rays), covering several km2 on the ground. During thunderstorms, strong electric fields modulate the energy spectra of EAS secondary particles, changing the shower size (number of EAS electrons) and altering the primary particle's estimated energy and frequency of the surface array triggers. Impulse amplifications of particle fluxes (the so-called thunderstorm ground enhancements, TGEs) manifest themselves as large peaks in the time series of count rates of particle detectors located on the Earth's surface. Free electrons are abundant at any altitude in the atmosphere, from small to large EASs. These electrons serve as seeds for electron accelerators, which operate in the thunderous atmosphere and send particle avalanches in the direction of Earth's surface and into space (terrestrial gamma flashes, TGFs). EAS cores randomly hitting arrays of particle detectors also generate short bursts of relativistic particles. For years, particle detectors, electric field sensors, and lightning locators have gathered information about the complex interactions of secondary particle fluxes, electric fields, and lightning flashes. This information is crucial for establishing a field of high-energy physics in the atmosphere. Correlated measurements of particle fluxes modulated by strong atmospheric electric fields, registration of broadband radio and optical emission from atmospheric discharges, and registration of electric fields and various meteorological parameters lead to a better understanding of the complex processes of particle-field interactions in the terrestrial atmosphere. The cooperation of cosmic rays and atmospheric physics has led to the development of models of the origin of particle bursts recorded on the Earth's surface, vertical and horizontal profiles of electric fields, initiation of lightning flashes, etc. Interdisciplinary atmospheric science primarily requires monitoring particle fluxes around the clock by synchronized networks of identical sensors that record and store multidimensional data in databases with open, fast, and reliable access. The advances in multidimensional measurements over the past decade significantly intensified the development of new integrated models of atmospheric electricity and electron acceleration, giving more insight into understanding the modulation effects posed on EAS particles in the strong atmospheric electric fields. [ABSTRACT FROM AUTHOR]

An unprecedented thunderstorm ground enhancement (TGE) event was recorded on May 23, 2023, at Aragats Mountain, the highest peak in Armenia. This event showcased a maximum flux intensity surpassing 3 million particles per minute per square meter for energies above 0.4 MeV. Distinctly, the fluence of the event was measured at approximately ≈700 particles/cm2. The comprehensive instrumentation at the Aragats research station, including a suite of spectrometers and detectors, enabled precise cross-correlation of measurements. The electron flux at energies exceeding 10 MeV was observed at roughly ≈55,000 particles per minute per square meter. Additional measurements, including cloud base heights and corona discharge detections, validated the intensity of the electric field, reaching approximately 2.1 kV/cm at elevations 50–100 m above ground level. Our observations confirm that TGE is a universal and significant atmospheric event, contributing a substantial flux of high-energy electrons to the global electrical circuit. Integrating such TGE phenomena into Earth's numerical models is imperative, considering their impact on aviation and aerospace operation safety. [ABSTRACT FROM AUTHOR]

To catalyze transformative advancements in High-energy Physics in the Atmosphere (HEPA), a comprehensive understanding of particle fluxes, electric fields, and lightning occurrences across atmospheric layers is imperative. This paper elucidates the instrumentation and capabilities of the Aragats Space-Environmental Center (ASEC), which encompasses measurement tools for various cosmic ray species, near-surface electric fields, and lightning events integrated across high-mountain research station at slopes of Mt. Aragats and the highest mountains of Eastern Europe and Germany. Through these measurements, we aim to elucidate models of particle acceleration mechanisms and the charge distribution within the lower atmosphere. We introduce an Advanced Data Extraction Infrastructure (ADEI) integrated with sophisticated statistical analysis tools to facilitate rapid access to this wealth of data. Despite the significance of these atmospheric processes, the intricate interplay between thundercloud electrification, lightning activity, wideband radio emissions, and particle fluxes remains poorly understood. A particularly compelling avenue of inquiry lies in exploring the relationship between high-energy atmospheric phenomena, intracloud electric fields, and lightning initiation. Furthermore, investigations into accelerated structures within geospace plasmas hold promise for shedding light on particle acceleration processes, potentially extending to higher energies within analogous structures in cosmic plasmas. This paper also examines practical methodologies for extracting meaningful physical insights from temporal datasets, such as correlating surges in particle flux intensity with variations in near-surface electric field strength and precipitation patterns. Additionally, we explore the utility of wideband field and interferometer antenna signals in this context, offering valuable avenues for further research and analysis. Through these endeavors, we aim to deepen our understanding of high-energy atmospheric processes and their broader implications for terrestrial and cosmic phenomena. [ABSTRACT FROM AUTHOR]

Low-mass early-type galaxies, including dwarf spheroidals (dSph) and brighter dwarf ellipticals (dE), dominate the galaxy population in groups and clusters. Recently, an additional early-type population of more extended ultradiffuse galaxies (UDGs) has been identified, sparking a discussion on the potential morphological and evolutionary connections between the three classifications. Here, we present the first measurements of spatially resolved stellar kinematics from deep integrated-light spectra of KDG 64 (UGC 5442), a large dSph galaxy in the M 81 group. From these data, we infer stellar population properties and dark matter halo parameters using Jeans dynamical modelling. We find an old, metal-poor stellar population with no young stars and a dark matter mass fraction of ∼90 per cent within the half-light radius. These properties and the position of KDG 64 on the Fundamental Plane indicate that it is a local analogue of smaller UDGs in the Coma and Virgo clusters and is probably a transitional dSph-UDG object. Its evolutionary path cannot be uniquely established from the existing data, but we argue that supernovae feedback and tidal heating played key roles in shaping KDG 64. [ABSTRACT FROM AUTHOR]

Rare giant low surface brightness galaxies (gLSBGs) act as a stress test for the current galaxy formation paradigm. To answer the question 'How rare are they?', we estimate their volume density in the local Universe. A visual inspection of 120 deg2 covered by deep Subaru Hyper Suprime-Cam data was performed independently by four team members. We detected 42 giant disky systems (30 of them isolated) at z ≤ 0.1 with either g -band 27.7 mag arcsec−2 isophotal radius or four disc scale lengths 4 h ≥ 50 kpc, 37 of which (including 25 isolated) had low central surface brightness (μ0, g ≥ 22.7 mag arcsec−2). This corresponds to volume densities of 4.70 × 10−5 Mpc−3 for all galaxies with giant extended discs and 4.04 × 10−5 Mpc−3 for gLSBGs, which converts to ∼12 700 such galaxies in the entire sky out to z < 0.1. These estimates agree well with the result of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological hydrodynamical simulation. Giant disky galaxies represent the large-sized end of the volume density distribution of normal-sized spirals, suggesting the non-exceptional nature of giant discs. We observe a high active galactic nucleus fraction among the newly found gLSBGs. [ABSTRACT FROM AUTHOR]

High-energy physics in the atmosphere (HEPA) has undergone an intense reformation in the last decade. Correlated measurements of particle fluxes modulated by strong atmospheric electric fields, simultaneous measurements of the disturbances of the near-surface electric fields and lightning location, and registration of various meteorological parameters on the Earth have led to a better understanding of the complex processes in the terrestrial atmosphere. The cooperation of cosmic rays and atmospheric physics has led to the development of models for the origin of particle bursts recorded on the Earth's surface, estimation of vertical and horizontal profiles of electric fields in the lower atmosphere, recovery of electron and gamma ray energy spectra, the muon deceleration effect, etc. The main goal of this review is to demonstrate how the measurements performed at the Aragats cosmic ray observatory led to new results in atmospheric physics. We monitored particle fluxes around the clock using synchronized networks of advanced sensors that recorded and stored multidimensional data in databases with open, fast, and reliable access. Visualization and statistical analysis of particle data from hundreds of measurement channels disclosed the structure and strength of the atmospheric electric fields and explained observed particle bursts. Consequent solving of direct and inverse problems of cosmic rays revealed the modulation effects that the atmospheric electric field has on cosmic ray fluxes. [ABSTRACT FROM AUTHOR]

We present and discuss transient luminous events (TLEs) in the lower atmosphere, observed during large disturbances of the near-surface electric fields (NSEF) and coinciding with large enhancements of the particle fluxes (thunderstorm ground enhancements—TGEs). Despite large distances from the strongest electric field region, the maximum energy of TGE particles on 22 and 25 May 2018 reaches ≈40 MeV. Thus, the accelerating electric field reaches ≈2.0 keV/cm far from the zone of the strong lightning activity on the periphery of the storm. Light glows appearing simultaneously in the skies may be due to the local charge rearrangement generating a small illuminating discharge without initiating the lightning flash. This type of charge rearrangement does not lower the potential difference in the cloud, allowing the electron accelerator to operate and send particle fluxes in the direction of the earth's surface. [ABSTRACT FROM AUTHOR]

Galaxy clusters are the largest gravitationally bound structures in the Universe and therefore are a powerful tool for studying mass assembly at different epochs. At z > 2, they provide the unique opportunity to place solid constraints not only on the growth of the dark matter halo, but also on the mechanisms of galaxy quenching and morphological transformation when the Universe was younger than 3.3 Gyr. However, the currently available sample of confirmed z > 2 clusters remains very limited. We present the spectroscopic confirmation of the galaxy cluster CARLA J0950+2743 at z = 2.363 ± 0.005 and a new serendipitously discovered cluster, CARLA-Ser J0950+2743 at z = 2.243 ± 0.008, in the same region. We confirm eight star-forming galaxies in the first and five in the second cluster by detecting [OII], [OIII], and Hα emission lines. The analysis of an archival X-ray Chandra dataset that covers the cluster position revealed a counterpart with a total luminosity of L0.5−5keV = 2.9 ± 0.6 × 1045 erg s−1. Because the depth of the X-ray observations is limited, we cannot distinguish the 1D profile of the source from a point spread function model, but our statistical analysis of the 2D profile favors an extended component that might be associated with a thermal contribution from the intracluster medium. If the extended X-ray emission is due to the hot intracluster medium, the total combined dark matter mass for the two clusters would be M200 ≈ 3.0−0.23(stat)+0.20−0.85(sys)+1.13 × 1014 M⊙, assuming a ∼30% contribution from the active galactic nucleus. Our two clusters are therefore interesting targets for studies of the structure growth in the cosmological context. However, future investigation will require deeper high-resolution X-ray and spectroscopic observations to rule out the hypotheses that the emission is entirely due to the active galactic nucleus or that it originates from other contaminating radio galaxies and structures. [ABSTRACT FROM AUTHOR]

On July 11, 2023, we observed a remarkable 500% increase in positron flux, coinciding with a significant Thunderstorm Ground Enhancement (TGE). The enhanced flux of electrons and gamma rays was attributed to relativistic runaway electron avalanches (RREAs) generated within the dipole formed between the main negatively charged layer in the middle of the thundercloud and the Lower Positively Charged Region (LPCR) at the bottom of the thundercloud. Concurrently, a substantial enhancement in the 511 keV gamma-ray flux resulting from electron-positron annihilation was recorded. This surge is intricately linked to the LPCR within the thundercloud. The emergence of the LPCR induces a polarity change in the atmospheric electric field (AEF) below the LPCR (fourth dipole), leading to the deceleration of electrons and the acceleration of positrons. Particle flux measurements were conducted using scintillation and NaI(TL) spectrometers. To mitigate the contamination of natural gamma radiation and refine the 511 keV flux measurements, the ORTEC spectrometer was shielded with a 4 cm thick lead filter. CORSIKA simulations corroborate the observed positron flux enhancement. Highlighting the synergy between high-energy physics in the atmosphere and astroparticle physics, we introduce a new scenario to elucidate the enigmatic large flux of galactic positrons measured by the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station (ISS). • We discover the fourth dipole in the lowest part of the atmospheric electric field (AEF). • The fourth dipole between the lower positively charged region and the ground decelerates electrons. • In the fourth dipole, positron flux bust during thunderstorms was 500% on July 11, 2005. • If AEF decelerates electrons, bremsstrahlung and pair production are much more intense. [ABSTRACT FROM AUTHOR]

The temporal variations of cosmic-ray intensity, measured by ground-based detectors at various latitudes, longitudes, and altitudes, are related to the geophysical and solar phenomena. The latter are interplanetary coronal mass ejections and fast solar wind from coronal holes, which cause interplanetary magnetic field (IMF) abrupt variations near Earth. Interacting with the magnetosphere, they cause worldwide sudden decreases (Forbush decreases, FDs) of intensity followed by gradual recovery. The amplitude of the flux depletion depends on the type and energy of the registered particle, which in turn depends on geographical coordinates and the detector's energy threshold and selective power. SEVAN particle detector network with nodes in Europe and Armenia selects three types of particles that demonstrate coherent depletion and recovery and correspond to different energy galactic protons interacting with disturbed magnetospheric plasmas. On November 3–4, 2021, an interplanetary coronal mass injection (ICME) hit the magnetosphere, sparking a strong G3-class geomagnetic storm and auroras as far south as California and New Mexico. All detectors of the SEVAN network have registered an (FD) of ≈5% depletion in a 1-min time series of count rates. Approaching the maximum solar activity cycle, large variations of the particle flux intensity were registered on February 27, March 23, 2023, and March 24, 2024. In this work, we present measurements of these FDs performed on mountain altitudes on Aragats (Armenia), Lomnicky Stit (Slovakia), Mileshovka (Czechia), and at sea level DESY (Hamburg, Germany). We compared FD measurements made by SEVAN detectors and neutron monitors located on Aragats and Lomnicky Stit and made a correlation analysis of FD registration at different locations. • Low energy CR, neutrons, and high energy muons measured by SEVAN detector are sensitive to solar modulation. • SEVAN and NM detectors demonstrate coherent depletion and recovery of cosmic ray fluxes. • SEVAN detectors at mountain altitudes registered a pre-FD increase in fluxes of high-energy muons. • FD coincides with large values of the interplanetary magnetic field B, and small values of geomagnetic field Bx. • SEVAN measurements confirm that FD depends highly on the disturbed IMF rather than its Bz component. [ABSTRACT FROM AUTHOR]

The authors would like to apologize for any inconvenience caused by our conclusion on the frequency of lightning flashes of different types terminated by Thunderstorm Ground Enhancements (TGEs) and that TGEs associated with inverted IC flashes and hybrid flashes caused relatively small particle flux drops (Chilingarian et al., 2020). We recently analyzed different types of lightning flashes that terminate TGEs using a significantly enlarged data sample (163 TGE events instead of 49) observed from 2012 to 2021 (Soghomonyan et al., 2021). Our analysis of this three times larger dataset has led to results that do not support some of our previous conclusions based on smaller statistics. Therefore, we present a new analysis of the expanded database and compare our previous and current findings on the relationship between particle fluxes and lightning discharges. • We present a statistical analysis of 163 thunderstorm ground enhancements terminated by lightning flashes. • Weak and strong TGEs terminated by inverted and normal polarity IC lightning flashes are proportionally equal. • If NSEF change was negative, 17.3% of terminated flashes were -IC, and 20% were composed of -IC followed by -CG. • If NSEF change was negative, 11.3% of terminating lightning flashes were +IC, and 49.3% were -CGs. [ABSTRACT FROM AUTHOR]

We compare simulations of muon traversal in the atmosphere and observation of the muon flux made on the Earth's surface to reveal the relation of the muon flux changes to the charge structure of the lower part of the thundercloud. The results show that the changes in the muon flux during large thunderstorm ground enhancements (TGEs) reveal the charge configurations of the cloud, namely a large negative electric field in the lower part of the cloud and an inverted dipole. Cosmic ray muons do not originate particle avalanches in the thunderclouds, like electrons. However, in the thundercloud, the positive and negative muons are decelerated or accelerated according to the sign of the intracloud electric field. Due to the charge asymmetry of the muon flux (excess of positive muons over negative), the total number of muons and muon charge ratio also changes. Plain Language Summary: The charged structures of the thundercloud, which initiated electron acceleration and lightning flashes, are still not well known. In the submitted letter, we examine the cosmic ray muon flux disturbances correlated with the charged structures of the thundercloud. At Aragats research station, we 24/7 monitor almost all species of secondary cosmic rays, near‐surface electric field, and register atmospheric discharges. The disturbances of the muon flux were used for the tomography of the atmospheric electric field evolving during thunderstorms. Our goal is to relate the disturbances of the atmospheric electric field to changing fluxes of the elementary particles, which propagate through the cloud. Our findings will help to reveal the unusual charge structures in the cloud by monitoring of the muon flux with the simple and reliable particle detectors, also described in the letter. Key Points: Muon flux changes during TGE reveal the charge structure of the thundercloudThe muon stopping effect is confirmed by simulationMuon charge ratio is the most sensitive parameter for the identification of the inverse dipole [ABSTRACT FROM AUTHOR]

Giant low surface brightness galaxies (gLSBGs) with dynamically cold stellar discs reaching the radius of 130 kpc challenge currently considered galaxy formation mechanisms. We analyse new deep long-slit optical spectroscopic observations, archival optical images, and published Hi and optical spectroscopic data for a sample of seven gLSBGs, for which we performed mass modelling and estimated the parameters of dark matter haloes assuming the Burkert dark matter density profile. Our sample is not homogeneous by morphology, parameters of stellar populations, and total mass, however, six of seven galaxies sit on the high-mass extension of the baryonic Tully–Fisher relation. In UGC 1382, we detected a global counterrotation of the stellar high surface brightness (HSB) disc with respect to the extended LSB disc. In UGC 1922 with signatures of a possible merger, the gas counterrotation is seen in the inner disc. Six galaxies host active galactic nuclei, three of which have the estimated black hole masses substantially below those expected for their (pseudo-)bulge properties suggesting poor merger histories. Overall, the morphology, internal dynamics, and low star formation efficiency in the outer discs indicate that the three formation scenarios shape gLSBGs: (i) a two-stage formation when an HSB galaxy is formed first and then grows an LSB disc by accreting gas from an external supply; (ii) an unusual shallow and extended dark matter halo; (iii) a major merger with fine-tuned orbital parameters and morphologies of the merging galaxies. [ABSTRACT FROM AUTHOR]

We describe a new phenomenon in atmospheric physics—222Rn progeny circulation during thunderstorms. The enhancement of the natural gamma radiation during thunderstorms was measured with precise gamma ray spectrometers. Results of measurements performed at Aragats mountain in Armenia during summer 2020 demonstrate the Rn progeny lifted to the atmosphere by a near‐surface electric field are returned backward to the ground by rain precipitation. Thus, thunderstorms not only return negative charge to the Earth by lightning flashes but also maintain Rn progeny circulation in the atmosphere; it this way, significantly enlarging natural gamma radiation above the Earth surface and Radon concentration in the atmosphere. Plain Language Summary: Radon gas and its daughter products account for more than half of the total human radiation dose from natural and man‐made radionuclides in the environment. Radioactive radiation contributes to the processes that lead to lung cancer. According to the WHO, radon is the second leading cause of lung cancer after tobacco smoking. In the letter, we describe a new phenomenon in the terrestrial atmosphere‐ the circulation of Radon and its progenies during thunderstorms. Measurements performed at Aragats mountain in Armenia during summer 2020 demonstrate the identity of the Rn progeny lifted to the atmosphere by a near‐surface electric field, and progenies returned to the ground with rain droplets. Thus, thunderstorms not only return negative charge to the Earth but also maintain Radon progeny circulation in the atmosphere during thunderstorms; it this way, significantly enlarging natural gamma radiation. Key Points: We describe a new phenomenon in atmospheric physics—Rn‐222 progeny circulation during thunderstormsThe Rn progeny lifted to the atmosphere by a near‐surface electric field are returned back to the ground by rainThe enhancement of the natural gamma radiation during thunderstorms was measured with precise gamma ray spectrometers [ABSTRACT FROM AUTHOR]

Pixel-space full spectrum fitting exploiting nonlinear χ2 minimization became a de facto standard way of deriving internal kinematics from absorption line spectra of galaxies and star clusters. However, reliable estimation of uncertainties for kinematic parameters remains a challenge and is usually addressed by running computationally expensive Monte-Carlo simulations. Here we derive simple formulae for the radial velocity and velocity dispersion uncertainties based solely on the shape of a template spectrum used in the fitting procedure and signal-to-noise information. Comparison with Monte-Carlo simulations provides agreement within a few per cent for different templates, signal-to-noise ratios and input velocity dispersions between 0.5 and 10 times the instrumental spectral resolution. For moderate template mismatch our technique returns uncertainties consistent within 20%–30% with those reported by Monte-Carlo simulations. We provide IDL and python implementations of our approach. The main applications are: (i) exposure time calculators; (ii) design of observational programs and estimates on expected uncertainties for spectral surveys of galaxies and star clusters; (iii) a cheap and accurate substitute for Monte-Carlo simulations when running them for large samples of thousands of spectra is unfeasible. [ABSTRACT FROM AUTHOR]

We have obtained a contiguous set of long-slit spectra of a shock wave in the Cygnus Loop to investigate its structure, which is far from the morphology predicted by 1D models. Proper motions from Hubble Space Telescope images combined with the known distance to the Cygnus Loop provide an accurate shock speed. Earlier analyses of shock spectra estimated the shock speed, postshock density, temperature, and elemental abundances. In this paper we determine several more shock parameters: a more accurate shock speed, ram pressure, density, compression ratio, dust destruction efficiency, magnetic field strength, and vorticity in the cooling region. From the derived shock properties we estimate the emissivities of synchrotron emission in the radio and pion decay emission in the gamma-rays. Both are consistent with the observations if we assume simple adiabatic compression of ambient cosmic-rays as in the van der Laan mechanism. We also find that, although the morphology is far from that predicted by 1D models and the line ratios vary dramatically from point to point, the average spectrum is matched reasonably well by 1D shock models with the shock speed derived from the measured proper motion. A subsequent paper will analyze the development of turbulence in the cooling zone behind the shock. [ABSTRACT FROM AUTHOR]

Purpose: To study the adaptation of bacteria to the natural γ-background of mountains and anthropogenic emissions from nuclear power plants; to establish the main factors of variability and speciation of bacteria. Method: Analysis of materials on the radiation background and its impact on living organisms in the landscape of Armenia, calculation of the absorbed dose by microbes due to rock radiation. Results: The review shows the death, reproduction, radioresistance and speciation of bacteria in changing conditions of low variable natural and anthropogenic γ-background. Conclusion: We assume that γ-rays from rocks activate cellular epigenetic mechanisms that regulate genome expression, signaling and, ultimately, variability of bacteria. Some of them have already been studied, others require research. [ABSTRACT FROM AUTHOR]

The study presented the relationship between sudden Natural Gamma Radiation (NGR) increases related to enhanced atmospheric electric fields. We pinpoint Thunderstorm Ground Enhancements (TGEs) as the primary source of abrupt and significant NGR spikes. These TGEs, which are transient, several-minute-long increases in elementary particle fluxes, originate from natural electron accelerators within thunderclouds. The more prolonged, yet less pronounced, increases in NGR, persisting for several hours, are attributed to the gamma radiation from radon progeny and enhanced positron fluxes. This radon, emanating from terrestrial materials, is carried aloft by the Near-Surface Electric Field (NSEF). To measure NGR at Aragats Mountain, we use an ORTEC detector and custom-built large NaI (Tl) spectrometers, employing lead filters to discriminate between cosmic ray fluxes and radon progeny radiation. Our analysis differentiates between radiation enhancements during positive and negative NSEF episodes. The resultant data provide a comprehensive measurement of the intensities of principal isotopes and positron flux during thunderstorms compared to fair weather conditions. • We measure NGR at Mt. Aragats (3200 m height) during thunderstorms. • NGR was enhanced many times for minutes and ≈20% for hours. • Positive NSEF is 1.5 more effective than negative in enhancing NGR. • Atmospheric positron flux boosts twice during positive near-surface electric fields. • The negative aerosol share on Earth is larger than that of positive aerosols. Natural gamma radiation is a crucial aspect of our environment that has significance in various fields, such as radiation protection and geological exploration. Understanding and monitoring natural gamma radiation levels for human safety and scientific purposes is essential. In this context, we discuss two new sources of natural gamma radiation: thunderstorm ground enhancements and enhanced radon progeny radiation in stormy weather. Both are associated with strong atmospheric electric fields. We measured enhanced natural gamma radiation in the energy range 0.3–3 MeV at positive and negative NSEF. We found that the positive NSEF is 1.5 times more effective than the negative one. Additionally, we demonstrated that positron flux is enhanced by 2.5 times more at positive NSEF compared with negative NSEF. [ABSTRACT FROM AUTHOR]

The energy spectra of Thunderstorm ground enhancement (TGE) electrons and gamma rays are the key evidence for proving the origin of enhanced particle fluxes from thunderclouds. Till now, the electron energy spectrum was measured only by the Aragats large scintillation spectrometer ASNT. We changed the electronics board of the SEVAN detector installed at the Umwelt-Forschungs-Station (UFS, Schneefernerhaus, 2650 m asl) to allow these vital measurements near the top of the Zugspitze. The new electronics of the SEVAN detector, supplied with logarithmic ADC, for the energy release measurements up to 50 MeV (the thickness of the spectrometric scintillator is 25 cm). Thus, by measuring energy releases well above 3 MeV, we unambiguously separate Radon progeny gamma radiation from the electrons and gamma-ray relativistic runaway avalanches. Using the different energy release histograms allows for separating charged and neutral particles, enabling the disentangling of electron and gamma-ray energy spectra. On May 23, 2023, the first TGE was registered on Zugspitze by the SEVAN detector. The gamma-ray flux enhancement was 44%, corresponding to the observed count rate peak enhancement of 44σ. The gamma-ray energy spectrum was recovered, maximum energy is 60 MeV. On the same day, a large TGE was observed on Aragats. The TGE maximum flux overpasses the fair-weather flux by 207%, equivalent to a 1-minute peak significance of 400σ. Maximum energy of electrons is 50 MeV, gamma rays – 45 MeV. In this context, we will explore and explain the new capabilities of the SEVAN detector installed on Zugspitze and the rearranged similar detector on Aragats. We also present and compare electron and gamma-ray energy spectra from Aragats TGE and gamma-ray energy spectrum from Zugspitze. [ABSTRACT FROM AUTHOR]

The dominant physical processes responsible for the formation and longevity of giant gaseous and stellar discs in galaxies remain controversial. Although they are rare (less than 10 confirmed as of now), giant low-surface brightness (gLSB) discy galaxies provide interesting insights given their extreme nature. We describe observations of UGC 1378 including deep spectroscopy with the Russian 6-m telescope and multiband imaging with Binospec at the MMT. Galaxy UGC 1378 has both high surface brightness and an extended low surface brightness discs. Our stellar velocity dispersion data for the high surface brightness, Milky Way sized, disc appears inconsistent with a recent major merger, a widely discussed formation scenario for the very extended low surface brightness disc. We estimate the star formation rates (SFRs) from archival Wide-Field Infrared Survey Explorer data. The SFR surface density in the LSB disc is low relative to its gas density, consistent with recent gas accretion. We argue that the unusually large size of UGC 1378's disc may be the product of a rich gas reservoir (e.g. a cosmic filament) and an isolated environment that has preserved the giant disc. [ABSTRACT FROM AUTHOR]

Abstract We present the observational data on registration of atmospheric discharges simultaneously with the detection of elementary particles obtained during thunderstorms at an altitude of 3200 m above sea level on Mt. Aragats in Armenia. Throughout the 2016 summer and 2018 spring campaigns on Aragats, we monitored lightning occurrences and signals from NaI spectrometers, plastic scintillators and Neutron Monitor proportional counters, and analyzed the shape of registered pulses. Particle detector signals were synchronized with lightning occurrences at a few nanoseconds level. Analysis of shapes of the simultaneously detected pulses of the fast wideband electric field produced by a lightning flash and pulses from particle detectors discloses that all additional detector pulses registered during lightning flash were the electromagnetic interference signals and not particles originated directly from the lightning bolt. Thus, we observe no evidence of the direct production of electrons, neutrons or gamma rays during a lightning flash. We conclude that the entire particle fluxes detected on Aragats research station (more than 250 TGEs) can be explained by the generation of MeV electromagnetic cascades in the strong atmospheric electric fields. [ABSTRACT FROM AUTHOR]

The formation scenario for giant low surface brightness (gLSB) galaxies with discs as large as 100 kpc still remains unclear. These stellar systems are rare and very hard to observe, therefore a detailed insight on every additional object helps to understand their nature. Here we present a detailed observational study of the gLSB UGC 1922 performed using deep optical imaging and spectroscopic observations combined with archival ultraviolet data. We derived spatially resolved properties of stellar and ionized gas kinematics and characteristics of stellar populations and interstellar medium. We reveal the presence of a kinematically decoupled central component, which counter rotates with respect to the main disc of UGC 1922. The radial metallicity gradient of the ionized gas is in agreement with that found for moderate-size LSB galaxies. At the same time, a slowly rotating and dynamically hot central region of the galaxy hosts a large number of old metal-rich stars, which creates an appearance of a giant elliptical galaxy, that grew an enormous star forming disc. We reproduce most of the observed features of UGC 1922 in N -body/hydrodynamical simulations of an in-plane merger of giant Sa and Sd galaxies. We also discuss alternative formation scenarios of this unusual system. [ABSTRACT FROM AUTHOR]

The origin of ultracompact dwarfs (UCDs), a class of compact stellar systems discovered two decades ago, still remains a matter of debate. Recent discoveries of central supermassive black holes in UCDs likely inherited from their massive progenitor galaxies provide support for the tidal stripping hypothesis. At the same time, on statistical grounds, some massive UCDs might be representatives of the high luminosity tail of the globular cluster luminosity function. Here we present a detection of a 3.3+1.4-1.2 x 106 M... black hole (1σ uncertainty) in the centre of the UCD3 galaxy in the Fornax cluster, which corresponds to 4 per cent of its stellar mass. We performed isotropic Jeans dynamical modelling of UCD3 using internal kinematics derived from adaptive optics-assisted observations with the SINFONI spectrograph and seeing limited data collected with the FLAMES spectrograph at the ESO VLT. We rule out the zero black hole mass at the 3σ confidence level when adopting a mass-to-light ratio inferred from stellar populations. This is the fourth supermassive black hole found in a UCD and the first one in the Fornax cluster. Similarly to other known UCDs that harbour black holes, UCD3 hosts metal rich stars enhanced in α-elements that support the tidal stripping of a massive progenitor as its likely formation scenario. We estimate that up to 80 per cent of luminous UCDs in galaxy clusters host central black holes. This fraction should be lower for UCDs in groups, because their progenitors are more likely to be dwarf galaxies, which do not usually host black holes massive enough to be detected. [ABSTRACT FROM AUTHOR]

The Space Environment Viewing and Analysis Network (SEVAN) aims to improve the fundamental research on particle acceleration in the vicinity of the sun, on space weather effects and on high-energy physics in the atmosphere and lightning initiation. This new type of a particle detector setup simultaneously measures fluxes of most species of secondary cosmic rays, thus being a powerful integrated device for exploration of solar modulation effects and electron acceleration in the thunderstorm atmosphere. The SEVAN modules are operating at the Aragats Space Environmental Center (ASEC) in Armenia, in Croatia, Bulgaria, Slovakia, the Czech Republic (from 2017) and in India. In this paper, we present the most interesting results of the SEVAN network operation during the last decade. We present this review on the occasion of the 10th anniversary of the International Heliophysical Year in 2007. [ABSTRACT FROM AUTHOR]

Acceleration and multiplication of the cosmic ray electrons by strong electric fields in the thundercloud are well-established phenomena comprising the core of the atmospheric high-energy physics. The majority of experimental data on particle acceleration in the thunderclouds comes from space-born experiments detecting Terrestrial Gamma flashes (TGFs) and from networks of particle detectors located on the earth’s surface observing Thunderstorm Ground Enhancements (TGEs). Models for explaining both TGF and TGE are based on the concept of a Runaway Breakdown (RB) introduced by A. Gurevich. Prove of these models requires registration of the electromagnetic avalanches developing in the thundercloud and reaching the earth’s surface. Unfortunately due to high location of cloud and fast attenuation of electrons in the atmosphere the registration of such an avalanches are very rare. On Aragats mountain in Armenia, where the cloud location is very low we observe several TGE events with sizable electron contribution. We present direct measurements of such an avalanches lasting less than a microsecond; hundreds of such avalanches comprise a TGE lasting few minutes. We recovered as well the differential energy spectra of electron and gamma ray content of avalanches. The abrupt termination of the particle flux by nearby lightning indicates that RB process precedes (initiates) the lightning flash. [ABSTRACT FROM AUTHOR]

Abstract: The Aragats Space-Environmental Center provides monitoring of different species of secondary cosmic rays at two altitudes and with different energy thresholds. One-minute data is available on-line from http://crdlx5.yerphi.am/DVIN/index2.php. We present description of the main monitors along with data acquisition electronics. Also we demonstrate the sensitivity of the different species of secondary cosmic ray flux to geophysical conditions, taking as examples the extremely violent events of October–November 2003. We introduce correlation analysis of the different components of registered time-series as a new tool for the classification of the geoeffective (events on earth affected by solar activity) events and for the forecasting of the severity of the upcoming geomagnetic storm. [Copyright &y& Elsevier]

For lightning research, we monitor particle fluxes from thunderclouds, the so-called thunderstorm ground enhancements (TGEs) initiated by runaway electrons, and extensive air showers (EASs) originating from high-energy protons or fully stripped nuclei that enter the Earth's atmosphere. We also monitor the near-surface electric field and atmospheric discharges using a network of electric field mills. The Aragats “electron accelerator” produced several TGEs and lightning events in the spring of 2015. Using 1-s time series, we investigated the relationship between lightning and particle fluxes. Lightning flashes often terminated the particle flux; in particular, during some TGEs, lightning events would terminate the particle flux thrice after successive recovery. It was postulated that a lightning terminates a particle flux mostly in the beginning of a TGE or in its decay phase; however, we observed two events (19 October 2013 and 20 April 2015) when the huge particle flux was terminated just at the peak of its development. We discuss the possibility of a huge EAS facilitating lightning leader to find its path to the ground. [ABSTRACT FROM AUTHOR]

After observation of hundreds of Thunderstorm Ground Enhancements (TGEs) we measure energy spectra of particles originated in clouds and directed towards Earth. We use these “beams” for calibration of cosmic ray detectors located beneath the clouds at an altitude of 3200 m at Mount Aragats in Armenia. The calibrations of particle detectors with fluxes of TGE gamma rays are in good agreement with simulation results and allow estimation of the energy thresholds and efficiencies of numerous particle detectors used for studying galactic and solar cosmic rays. [ABSTRACT FROM AUTHOR]

Compact elliptical galaxies form a rare class of stellar system (~30 presently known) characterized by high stellar densities and small sizes and often harboring metal-rich stars. They were thought to form through tidal stripping of massive progenitors, until two isolated objects were discovered where massive galaxies performing the stripping could not be identified. By mining astronomical survey data, we have now found 195 compact elliptical galaxies in all types of environment. They all share similar dynamical and stellar population properties. Dynamical analysis for nonisolated galaxies demonstrates the feasibility of their ejection from host clusters and groups by three-body encounters, which is in agreement with numerical simulations. Hence, isolated compact elliptical and isolated quiescent dwarf galaxies are tidally stripped systems that ran away from their hosts. [ABSTRACT FROM AUTHOR]

We describe the new spectroscopic data reduction pipeline for the multi-object MMT/Magellan Infrared Spectrograph. The pipeline is implemented in IDL as a stand-alone package and is publicly available in both stable and development versions. We describe novel algorithms for sky subtraction and correction for telluric absorption. We demonstrate that our sky subtraction technique reaches the Poisson limit set by the photon statistics. Our telluric correction uses a hybrid approach by first computing a correction function from an observed stellar spectrum, and then differentially correcting it using a grid of atmosphere transmission models for the target airmass value. The pipeline provides a sufficient level of performance for real time reduction and thus enables data quality control during observations. We reduce an example dataset to demonstrate the high data reduction quality. [ABSTRACT FROM AUTHOR]

• Most powerful natural particle accelerators that operate in the electrified atmosphere send millions and millions of particles in direction to the earth's surface. The same are doing protons and fully-stripped nuclei accelerated in the most violent explosions in our galaxy and beyond when entering the terrestrial atmosphere and unleashing gigantic particle cascades. • Lightning flashes, in their development phase also generate strong electric fields capable to accelerate electrons. Particle detectors observe a rich variety of short and extended particle bursts that should be scrutinized for the determination of their sources and acceleration mechanisms. Only a multisensory approach joining particle and atmospheric physics instrumentation will allow revealing the physics of particle bursts phenomena. In this paper, we present an approach based on observations made by the largest cosmic ray experiments to explain enigmatic particle bursts usually connected to complicated atmospheric processes. • Multiyear observations made on Aragats cosmic ray observatory give a vast amount of data on particle bursts that can be explained by invoking the extensive air shower development in the atmosphere. Particle bursts detected on the earth's surface during thunderstorms by various particle detectors originated from the relativistic runaway electron avalanches (RREAs) initiated by free electrons accelerated in the strong atmospheric electric fields. Two oppositely directed dipoles in the thundercloud accelerate electrons in the direction of the earth's surface, and to the open space. The particle bursts observed by orbiting gamma ray observatories are called terrestrial gamma ray flashes (TGFs, with energies of several MeV, only sometimes reaching tens of MeV); ones registered by particle detectors located on the ground – are called thunderstorm ground enhancements (TGEs, with energies, usually reaching 40-50 MeV). Balloons and aircraft in the troposphere register gamma ray glows (with energies of several MeV). Recently, high-energy atmospheric physics includes also, so-called, downward TGFs (DTGFs), intense particle bursts with a duration of a few milliseconds. Well-known extensive air showers (EASs) originate from the interactions of galactic protons and fully-stripped nuclei with the atmosphere atoms. EAS particles have very dense cores around the shower axes. However, high-energy particles in the EAS cores comprise a very thin disc of (a few tens of ns), and a particle detector traversed by an EAS core will not register a particle burst, but only one very large pulse. Only neutron monitor, by collecting delayed thermal neutrons from EAS core particle interactions with soil, can register particle bursts. We discuss the relation between short particle bursts available from the largest particle arrays with EAS phenomena. We demonstrate that the neutron monitors can extend the EAS "lifetime" up to a few milliseconds, a time comparable with DTGFs duration. The possibility to use the network of neutron monitors for high-energy cosmic ray research is also deliberated. Plain Language Summary: Short and extended particle bursts are registered in space, the troposphere, and the earth's surface. Coordinated monitoring of the particle fluxes, near-surface electric fields, and lightning flashes makes it possible to formulate a hypothesis on the origin of intense bursts and their relation to extensive air showers and atmospheric discharges. Analysis of the observational data and possible origination scenarios of particle bursts allows us to conclude that the bursts can be explained by the electron acceleration in the thunderous atmosphere and by gigantic showers developed in the terrestrial atmosphere by high-energy protons and fully-stripped nuclei accelerated in Galaxy. [ABSTRACT FROM AUTHOR]

Abstract: In the beginning of last century C.T.R. Wilson proposed that strong electric field of the thunderclouds might accelerate electrons to very high energies. However, this and many other electromagnetic processes in our atmosphere are poorly understood till now; the key questions about the thundercloud electrification and lightning initiation remain unanswered. During recent decades several observations of gamma ray, electron and neutron fluxes correlated with thunderstorms were reported. Nonetheless, the origin of these fluxes is under debate till now. The direct registration of the particle showers initiated by the runaway electrons (the most popular theory) was missing. We present the experimental evidence of the microsecond duration electron bursts originated from runaway electrons accelerated in thunderclouds. The electron acceleration downward becomes possible after creation of the Lower Positive Charged Region below the main negative charged layer in the middle of the thundercloud. Our analysis is based on the vast thunderstorm data from the Aragats Mountain in Armenia, 3200m above sea level. Varieties of particle detectors located at Aragats Space Environmental Center are registering neutral and charged particle fluxes correlated with thunderstorms, so-called Thunderstorm Ground Enhancements. Simultaneously the electric mills and lightning detectors are monitoring the near-surface electric field and lightning flashes. In the paper we present the model of TGE initiation. We demonstrate the necessity of the Lower positive charge region development for the lower dipole operation and TGE initiation. Our observations establish direct relationship of the negative electric field strength and rain rate with TGE. [Copyright &y& Elsevier]

We describe a robust technique based on the ULySS IDL code for measuring velocity dispersions of galaxies observed with the MMT's fiber-fed spectrograph, Hectospec. This procedure is applicable to all Hectospec spectra having a signal-to-noise ratio ≳5 and weak emission lines. We estimate the internal error in the Hectospec velocity dispersion measurements by comparing duplicate measurements of 171 galaxies. For a sample of 984 galaxies with a median z = 0:10, we compare velocity dispersions measured by Hectospec through a 1.5" diameter optical fiber with those measured by the Sloan Digital Sky Survey (SDSS) and Baryon Oscillation Spectral Survey (BOSS) through 3" and 2" diameter optical fibers, respectively. The systematic differences between the Hectospec and the SDSS/BOSS measurements are <7% for velocity dispersions between 100 and 300 km s-1; the differences are no larger than the differences among the three BOSS velocity dispersion reductions. We analyze the scatter about the fundamental plane and find no significant redshift-dependent systematics in our velocity dispersion measurements to z ~ 0:6. This analysis also confirms our estimation of the measurement errors. In 1 hr in good conditions, we demonstrate that we achieve 30 km s-1 velocity dispersion errors for galaxies with an SDSS r fiber magnitude of 21. [ABSTRACT FROM AUTHOR]

Abstract: Starting from 2008 experimental facilities of the Aragats Space Environmental Center (ASEC) routinely measure time series of secondary cosmic ray fluxes. At these years of the minimum of solar activity we analyze the new high-energy phenomena in the terrestrial atmosphere. Namely, Thunderstorm Ground Enhancements (TGEs) and Extensive Cloud Showers (ECSs). Several new particle detectors were designed and fabricated having lower energy threshold to detect particle fluxes from the thunderclouds; some of them have possibility to distinguish charged and neutral fluxes. During 2008–2012years ASEC detectors located at Aragats, Nor Amberd and Yerevan were detected ∼300 TGE enhancements. Amplitude of majority of them is less than 5%; however, 13 TGEs have amplitude exceeding 20%. The maximal value of observed enhancement was 271% (September 19, 2009). The paper summarizes five-years study of the TGEs on Aragats. The statistical analysis revealing the month and day-of-time distributions of TGE events, as well as the amplitude and event duration diagrams are presented. [Copyright &y& Elsevier]

Abstract: The high altitude (∼3200m above sea level) of Aragats Space Environmental Center (ASEC) and low elevation of the thunderclouds provides a good opportunity to detect Thunderstorm Ground Enhancements (TGEs), particles of which rapidly attenuate in the atmosphere. In 2012, we have estimated the energy spectra of several TGEs and revealed significant electron fluxes extended till 30–40MeV. Measured in the one and the same event gamma ray and electron fluxes allow to estimate the height of the thundercloud above the detector. Proceeding from the energy spectra and the height of the cloud we estimate the electron spectra on the exit from the electric field of the thundercloud, the number of excess electrons in the cloud and avalanche multiplication rate. [Copyright &y& Elsevier]

Abstract: Strong electric fields inside thunderclouds give rise to enhanced fluxes of high-energy electrons and, consequently, gamma rays and neutrons. During thunderstorms at Mount Aragats, hundreds of Thunderstorm Ground Enhancements (TGEs) comprising millions of energetic electrons and gamma rays, as well as neutrons, were detected at Aragats Space Environmental Center (ASEC) on 3200m altitude. Observed large TGE events allow for the first time to measure the energy spectra of electrons and gamma rays well above the cosmic ray background. The energy spectra of the electrons have an exponential shape and extend up to 30–40MeV. Recovered energy spectra of the gamma rays are also exponential in energy range 5–10MeV, then turns to power law and extends up to 100MeV. [Copyright &y& Elsevier]

ABSTRACT The bimodal galaxy distribution in the optical colour-magnitude diagram (CMD) comprises a narrow 'red sequence' populated mostly by early-type galaxies and a broad 'blue cloud' dominated by star-forming systems. Although the optical CMD allows one to select red sequence objects, neither can it be used for galaxy classification without additional observational data such as spectra or high-resolution images, nor to identify blue galaxies at unknown redshifts. We show that adding the near ultraviolet (NUV) colour [ Galaxy Evolution Explorer (GALEX) NUV λeff= 227 nm] to the optical ( g − r versus M r) CMD reveals a tight relation in the 3D colour-colour-magnitude space smoothly continuing from the 'blue cloud' to the 'red sequence'. We found that 98 per cent of 225 000 low-redshift ( Z < 0.27) galaxies follow a smooth surface with a standard deviation of 0.03-0.07 mag making it the tightest known galaxy photometric relation, given the ∼0.9 mag range of k-corrected g − r colours. Similar relations exist in other NUV-optical colours. There is a strong correlation between morphological types and integrated colours of galaxies, while the connection with g − r is ambiguous. Rare galaxy classes such as E+A or tidally stripped systems become outliers that occupy distinct regions in the 3D parameter space. Using stellar population models for galaxies with different star formation histories, we show that (a) the () distribution at a given luminosity is formed by objects having constant and exponentially declining star formation rates with different characteristic time-scales with the red sequence part consistent also with simple stellar population; (b) colour evolution for exponentially declining models goes along the relation suggesting a weak evolution of its shape up to a redshift of 0.9; (c) galaxies with truncated star formation histories have very short transition phase offset from the relation thus explaining the rareness of E+A galaxies. This relation can be used as a powerful galaxy classification tool when morphology remains unresolved. Its mathematical consequence is the possibility of precise and simple redshift estimates from only three broad-band photometric points. We show that this simple approach being applied to Sloan Digital Sky Survey and GALEX data works better than most existing photometric redshift techniques applied to multicolour data sets. Therefore, the relation can be used as an efficient search technique for galaxies at intermediate redshifts (0.3 < Z < 0.8) using optical imaging surveys. [ABSTRACT FROM AUTHOR]

BSTRACT [ABSTRACT FROM AUTHOR]

Abstract: Particle detectors of worldwide networks are continuously measuring various secondary particle fluxes incident on Earth surface. At the Aragats Space Environmental Center (ASEC), the data of 12 cosmic ray particle detectors with a total of ∼280 measuring channels (count rates of electrons, muons and neutrons channels) are sent each minute via wireless bridges to a MySQL database. These time series are used for the different tasks of off-line physical analysis and for online forewarning services. Usually long time series contain several types of errors (gaps due to failures of high or low voltage power supply, spurious spikes due to radio interferences, abrupt changes of mean values of several channels or/and slowly trends in mean values due to aging of electronics components, etc.). To avoid erroneous physical inference and false alarms of alerting systems we introduce offline and online filters to “purify” multiple time-series. In the presented paper we classify possible mistakes in time series and introduce median filtering algorithms for online and off-line “purification” of multiple time-series. [Copyright &y& Elsevier]

The origin of ultracompact dwarf (UCD) galaxies, compact extragalactic stellar systems, is still a puzzle for present galaxy formation models. We present the comprehensive analysis of high-resolution multi-object spectroscopic data for a sample of 24 Fornax cluster UCDs obtained with VLT with Fibre Large Array Multi Element Spectrograph (FLAMES). It comprises previously published data for 19 objects which we re-analysed, including 13 with available Hubble Space Telescope ( HST) photometric data. Using Virtual Observatory technologies we found archival HST images for two more UCDs and then determined their structural properties. For all objects we derived internal velocity dispersions, stellar population parameters and stellar mass-to-light ratios by fitting individual simple stellar population (SSP) synthetic spectra convolved with a Gaussian against the observed spectra using the NB full spectral fitting technique. For 14 objects we estimated dynamical masses suggesting no dark matter (DM) in 12 of them and no more than 40 per cent DM mass fraction in the remaining two, in contrast to findings for several UCDs in the Virgo cluster. Some Fornax UCDs even have too high values of estimated using the Kroupa stellar initial mass function (IMF) resulting in negative formally computed DM mass fractions. The objects with too high ratios compared to the dynamical ones have relatively short dynamical relaxation time-scales, close to the Hubble time or below. We therefore suggest that their lower dynamical ratios are caused by low-mass star depletion due to dynamical evolution. Overall, the observed UCD characteristics suggest at least two formation channels: tidal threshing of nucleated dwarf galaxies for massive UCDs (), and a classical scenario of red globular cluster formation for lower-mass UCDs (). [ABSTRACT FROM AUTHOR]

Abstract: After the major modernization of the data acquisition electronics of the particle detectors operated at Aragats Space Environmental Center (ASEC) calculations of the barometric coefficients of all the monitors were performed in the beginning of the 24th solar activity cycle. The barometric coefficients of particle detectors located at altitudes of 1000m, 2000m and 3200m a.s.l. measuring various secondary cosmic ray fluxes were compared with theoretical expectations and monitors operated on different longitudes and latitudes. The barometric coefficients were also calculated for the several neutron monitors of recently established Eurasian database (NMDB) and SEVAN particle detector networks. The latitude and altitude dependencies of the barometric coefficients were investigated, as well as the dependence of coefficients on energy of the primary particles. [Copyright &y& Elsevier]

We have investigated the stellar population properties in the central regions of a sample of lenticular galaxies with bars and single-exponential outer stellar disks using the data from the SAURON integral-field spectrograph retrieved from the open Isaac Newton Group Archive. We have detected chemically decoupled compact stellar nuclei with a metallicity twice that of the stellar population in the bulges in seven of the eight galaxies. A starburst is currently going on at the center of the eighth galaxy and we have failed to determine the stellar population properties from its spectrum. The mean stellar ages in the chemically decoupled nuclei found range from 1 to 11 Gyr. The scenarios for the origin of both decoupled nuclei and lenticular galaxies as a whole are discussed. [ABSTRACT FROM AUTHOR]

To compare photometric properties of galaxies at different redshifts, the fluxes need to be corrected for the changes of effective rest-frame wavelengths of filter bandpasses, called -corrections. Usual approaches to compute them are based on the template fitting of observed spectral energy distributions (SED) and, thus, require multicolour photometry. Here, we demonstrate that, in cases of widely used optical and near-infrared (NIR) filters, -corrections can be precisely approximated as two-dimensional low-order polynomials of only two parameters: redshift and one observed colour. With this minimalist approach, we present the polynomial fitting functions for -corrections in Sloan Digital Sky Survey (SDSS) , United Kingdom Infrared Telescope (UKIRT) Wide Field Camera , Johnson–Cousins and Two Micron All Sky Survey bands for galaxies at redshifts based on empirically computed values obtained by fitting combined optical–NIR SEDs of a set of 10 galaxies constructed from SDSS Data Release 7 (DR7) and UKIRT Infrared Deep Sky Survey DR5 photometry using the Virtual Observatory. For luminous red galaxies we provide -corrections as functions of their redshifts only. In two filters, and , we validate our solutions by computing -corrections directly from SDSS DR7 spectra. We also present a -corrections calculator, a web-based service for computing -corrections online. [ABSTRACT FROM AUTHOR]

We report the discovery of the second compact elliptical (cE) galaxy SDSS in the nearby NGC 5846 group by the Virtual Observatory (VO) workflow. This object ( mag, ) becomes the fifth cE where the spatially resolved kinematics and stellar populations can be obtained. We used archival HST WFPC2 images to demonstrate that its light profile has a two-component structure, and integrated photometry from GALEX, SDSS, UKIDSS and Spitzer to build the multiwavelength spectral energy distribution to constrain the star formation history (SFH). We observed this galaxy with the PMAS IFU spectrograph at the Calar-Alto 3.5-m telescope and obtained two-dimensional maps of its kinematics and stellar population properties using the full-spectral fitting technique. Its structural, dynamical and stellar population properties suggest that it had a massive progenitor heavily tidally stripped by NGC 5846. [ABSTRACT FROM AUTHOR]

Abstract: A study of daily variations of secondary Cosmic Rays (CR) is performed using data on charged and neutral CR fluxes. Particle detectors of Aragats Space-Environmental Center (ASEC), Space Environmental Viewing and Analysis Network (SEVAN) and neutron monitors of the Neutron Monitor Database (NMDB) are used. ASEC detectors continuously register various species of secondary CR with different threshold energies and incident angles. NMDB joins data of 12 Eurasian neutron monitors. Data at the beginning of the 24th solar activity cycle are used to avoid biases due to solar transient events and to establish a benchmark for the monitoring of solar activity in the new started solar cycle. After eliminating changes associated with atmospheric pressure variations, solar diurnal variations are clearly seen in muon and neutron fluxes. Neutrons daily variations magnitudes, corresponding to the lowest energy primary protons, are comparable with the magnitudes of variations of charged secondary CR. Diurnal variations of neutron flux are higher for the high latitudes comparing with middle latitudes. For low energy muons, the variations are bigger comparing higher energy muons. [Copyright &y& Elsevier]

Abstract: To improve the physical understanding of the Forbush decreases (FD) and to explore the Space Weather drivers, we need to measure as much geospace parameter as possible, including the changing fluxes of secondary cosmic rays. At the Aragats Space Environmental Center (ASEC) are routinely measured the neutral and charged fluxes of secondary cosmic rays. Each of species has different most probable energy of primary “parent” proton/nuclei. Therefore, the energy range of the Galactic Cosmic Rays (GCR) affected by Interplanetary Coronal Mass Ejection (ICME) can be effectively estimated using data of the ASEC monitors. We presented relations of the magnitude of FD observed in different secondary particle fluxes to the most probable energy of the primary protons. We investigate the correlations between the magnitude of FD with the size, speed, density and magnetic field of the ICME. We demonstrate that the attenuation of the GCR flux incident on the Earth’s atmosphere due to passing of the ICME is dependent on the speed and size of the ICME and the magnetic field strength. [Copyright &y& Elsevier]

Compact elliptical galaxies are characterized by small sizes and high stellar densities. They are thought to form through tidal stripping of massive progenitors. However, only a handful of them were known, preventing us from understanding the role played by this mechanism in galaxy evolution. We present a population of 21 compact elliptical galaxies gathered with the Virtual Observatory. Follow-up spectroscopy and data mining, using high-resolution images and large databases, show that all the galaxies exhibit old metal-rich stellar populations different from those of dwarf elliptical galaxies of similar masses but similar to those of more massive early-type galaxies, supporting the tidal stripping scenario. Their internal properties are reproduced by numerical simulations, which result in compact, dynamically hot remnants resembling the galaxies in our sample. [ABSTRACT FROM AUTHOR]

Abstract: Cosmic Ray research on Mt. Aragats began in 1934 with the measurements of East–West anisotropy by the group from Leningrad Physics-Technical Institute and Norair Kocharian from Yerevan State University. Stimulated by the results of their experiments in 1942 Artem and Abraham Alikhanyan brothers organized a scientific expedition to Aragats. Since that time physicists were studying Cosmic Ray fluxes on Mt. Aragats with various particle detectors: mass spectrometers, calorimeters, transition radiation detectors, and huge particle detector arrays detecting protons and nuclei accelerated in most violent explosions in Galaxy. Latest activities at Mt. Aragats include Space Weather research with networks of particle detectors located in Armenia and abroad, and detectors of Space Education center in Yerevan. [Copyright &y& Elsevier]

Abstract: Primary cosmic rays interact with the Earth’s atmosphere producing atmospheric showers, thus giving rise to the fluxes of secondary particles. Particle detectors of the Aragats Space Environmental Center (ASEC) and Space Environmental Viewing and Analysis Network (SEVAN) continuously measure neutral and charged fluxes of elementary particles, incident on the Earth’s surface. Using CORSIKA code, we have calculated response of ASEC detectors to galactic and solar cosmic rays. The main result of this paper is the estimation of the most probable energy of primary proton generating different secondary fluxes detected on the Earth’s surface by a variety of instruments. Results of the paper are applicable to recover the solar proton flux from the surface observations of the ground level enhancements (GLE). In addition, the determination of the most probable energies of the primary proton will help to study energy dependence of solar transient events (Forbush decreases, geomagnetic storms). [Copyright &y& Elsevier]