Epochs Of Activity Research Articles

A new census of dust and polycyclic aromatic hydrocarbons at z = 0.7–2 with JWST MIRI

Aims. This paper utilises the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) to extend the observational studies of dust and polycyclic aromatic hydrocarbon (PAH) emission to a new mass and star formation rate (SFR) parameter space beyond our local Universe. The combination of fully sampled spectral energy distributions (SEDs) with multiple mid-infrared (mid-IR) bands and the unprecedented sensitivity of MIRI allows us to investigate dust obscuration and PAH behaviour from z = 0.7 up to z = 2 in typical main-sequence galaxies. Our focus is on constraining the evolution of PAH strength and the dust-obscured luminosity fraction before and during cosmic noon, the epoch of peak star formation activity in the Universe. Methods. In this study, we utilise MIRI multi-band imaging data from the SMILES survey (5 to 25 μm), complemented with NIRCam photometry from the JADES survey (1 to 5 μm), available HST photometry (0.4 to 0.9 μm), and spectroscopic redshifts from the FRESCO and JADES surveys in GOODS-S for 443 star-forming (without dominant active galactic nucleus (AGN)) galaxies at z = 0.7 − 2.0. This redshift range was chosen to ensure that the MIRI data cover mid-IR dust emission. Our methodology involved employing ultraviolet (UV) to IR energy balance SED fitting to robustly constrain the fraction of dust mass in PAHs and dust-obscured luminosity. Additionally, we inferred dust sizes from MIRI 15 μm imaging data, enhancing our understanding of the physical characteristics of dust within these galaxies. Results. We find a strong correlation between the fraction of dust in PAHs (PAH fraction, qPAH) with stellar mass. Moreover, the sub-sample with robust qPAH measurements (N = 216) shows a similar behaviour between qPAH and gas-phase metallicity to that at z ∼ 0, suggesting a universal relation: qPAH is constant (∼3.4%) above a metallicity of Z ∼ 0.5 Z⊙ and decreases to < 1% at metallicities ≲0.3 Z⊙. This indicates that metallicity is a good indicator of the interstellar medium properties that affect the balance between the formation and destruction of PAHs. The lack of a redshift evolution from z ∼ 0 − 2 also implies that above Z ∼ 0.5 Z⊙ the PAH emission effectively traces obscured luminosity and the previous locally calibrated PAH-SFR calibrations remain applicable in this metallicity regime. We observe a strong correlation between the obscured UV luminosity fraction (ratio of obscured to total luminosity) and stellar mass. Above the stellar mass of M* > 5 × 109 M⊙, on average, more than half of the emitted luminosity is obscured, while there exists a non-negligible population of lower-mass galaxies with > 50% obscured fractions. At a fixed mass, the obscured fraction correlates with SFR surface density. This is a result of higher dust covering fractions in galaxies with more compact star-forming regions. Similarly, galaxies with high IRX (IR to UV luminosity) at a given mass or UV continuum slope (β) tend to have higher ΣSFR and shallower attenuation curves, owing to their higher effective dust optical depths and more compact star-forming regions.

A Spatial Reconstruction Method of Ionospheric foF2 Based on High Accuracy Surface Modeling Theory

The ionospheric F2 critical frequency (foF2) is one of the most crucial application parameters in high-frequency communication, detection, and electronic warfare. To improve the accuracy of spatial reconstruction of the ionospheric foF2, we propose a high-accuracy surface (HAS) modeling method. This method converts difficult-to-solve differential equations into more manageable algebraic equations using direct difference approximation, significantly reducing algorithm complexity and computational load while exhibiting excellent convergence properties. We used seven stations in Brisbane, Canberra, Darwin, Hobart, Learmonth, Perth, and Townsville, with one station as a validation station and six as training stations (e.g., Brisbane as a validation station and the other stations—Canberra, Darwin, Hobart, Learmonth, Perth, and Townsville—as training stations). The training stations and the HAS method were used to train and reconstruct the validation stations at different solar activity periods, seasons, and local times. The predicted values of the validation stations were compared with the measured values, and the proposed method was analyzed and validated. The reconstruction results show the following. (1) The relative root mean square errors (RRMSEs) of HAS method prediction in different solar activity epochs were 13.67%, 7.74%, and 9.19%, respectively, which are 13.57%, 7.41%, and 6.41% higher than the prediction accuracy of the Kriging method, respectively. (2) In the four seasons, the RRMSEs of the HAS method prediction are 9.27%, 13.1%, 8.81%, and 8.09%, respectively, which are 10.83%, 11.73%, 4.25%, and 12.00% higher than the prediction accuracy of the Kriging method. (c) During the daytime and nighttime, the RRMSEs of HAS method prediction were 9.23% and 11.17%, which were 5.92% and 11.99% higher than the prediction accuracy of the Kriging method, respectively. (d) Under the validation dataset, the average predictive RRMSE of the HAS method was 10.29%, and the average predictive RRMSE of the IRI prediction model was 12.35%, with a 2.06% improvement in the predictive accuracy of the HAS method. In general, the prediction effect of the HAS method was better than that of the Kriging method, thus verifying the effectiveness and reliability of the proposed method. In summary, the proposed reconstruction method is of great significance for improving usable frequency prediction and enhancing communication performance.

A pilot study to detect the effects of a green-lipped mussel (Perna canaliculus) nutraceutical on working farm dogs with musculoskeletal abnormalities using accelerometry

ABSTRACT Aims To obtain preliminary data on changes in gait from the use of a green-lipped mussel (Perna canaliculus) extract product in working farm dogs with musculoskeletal abnormalities using accelerometry. Methods: New Zealand working farm dogs (n = 32) with signs of musculoskeletal abnormalities were enrolled in a double-blinded, placebo-controlled cross-over study. Each dog was allocated to one of six groups to receive three trial substances (180 mg full fat green-lipped mussel extract (GLME180); 220 mg full fat green-lipped mussel extract (GLME220); placebo) in one of the six possible different orders. Each trial substance was administered orally once a day for an 8-week period, with a 4-week washout in between each. Dogs wore a collar-mounted triaxial accelerometer for the study duration. Diet and activity were not controlled. Accelerations were recorded continuously and analysed (n = 27) in 10-second activity epochs partitioned into daytime and night-time periods. Analysis of activity during the daytime period was limited to epochs when dogs were gaiting faster than a walk. The median and IQR of activity were determined for the daytime and night-time. Additionally, the 75th and 90th percentiles of daytime activity for each 24-hour period were determined. Mixed effects linear regression models were constructed to determine if each trial substance altered the response variables. Results During the daytime, the 90th percentile was higher when dogs were given GLME220 compared with the placebo (β coefficient 2.6; 95% CI = 0.25–4.94; p = 0.03). Dogs that started the trial with the GLME products had a higher 90th percentile activity compared with dogs that began with the placebo (β coefficient 26.26; 95% CI = 0.45–52.06; p = 0.046). The 75th percentile for activity was not affected by the GLME product. The daytime IQR was larger when dogs were given the GLME180 product compared with the placebo (β coefficient 1.25; 95% CI = 0.12–2.37; p = 0.03). Night-time median activity and the IQR was greater in dogs that started the trial with the GLME products than in dogs that began with the placebo. The night-time IQR for activity was greater for GLME180 than for the placebo. Conclusions Administration of a low dose of the GLME-containing product increased peak activity in working farm dogs with signs of musculoskeletal abnormalities and may improve their performance. Clinical relevance Even mildly affected working farm dogs might benefit from support of their musculoskeletal abnormalities, and this particular GLME-based product shows promise as an adjunct to other management strategies.

The Algorithm of the Two Neutron Monitors for the Analysis of the Rigidity Spectrum Variations of Galactic Cosmic Ray Intensity Flux in Solar Cycle 24

The method of the two neutron monitors was used to analyze the parameters of the rigidity spectrum variations (RSV) of galactic cosmic ray intensity (GCR) flux in solar cycle 24 based on the data from the global network of neutron monitors. This method is an alternative to the least squares method when there are few monitors working stably in a given period, and their use in the least squares method is impossible. Analyses of the changes in exponent γ in the RSV of GCR flux from 2009 to 2019 were studied. The soft RSV (γ = 1.2–1.3) of the GCR flux around the maximum epoch and the hard RSV (γ = 0.6–0.9) around the minimum epoch of solar activity (SA) is the general feature of GCR modulation in the GeV energy scale (5, 50), to which neutron monitors were found to correspond. Therefore, various values of the RSV γ in the considered period show that during the decrease and increase period of SA, the essential changes in the large-scale structure of the heliospheric magnetic field (HMF) fluctuations/turbulence take place. The exponent γ of the RSV of the GCR flux can be considered a significant parameter to investigate the long-period changes in the GCR flux.

A machine learning artefact detection method for single-channel infant event-related potential studies

Objective. Automated detection of artefact in stimulus-evoked electroencephalographic (EEG) data recorded in neonates will improve the reproducibility and speed of analysis in clinical research compared with manual identification of artefact. Some studies use very short, single-channel epochs of EEG data with little recorded EEG per infant—for example because the clinical vulnerability of the infants limits access for recording. Current artefact-detection methods that perform well on adult data and resting-state and multi-channel data in infants are not suitable for this application. The aim of this study was to create and test an automated method of detecting artefact in single-channel 1500 ms epochs of infant EEG. Approach. A total of 410 epochs of EEG were used, collected from 160 infants of 28–43 weeks postmenstrual age. This dataset—which was balanced to include epochs of background activity and responses to visual, auditory, tactile and noxious stimuli—was presented to seven independent raters, who independently labelled the epochs according to whether or not they were able to visually identify artefacts. The data was split into a training set (340 epochs) and an independent test set (70 epochs). A random forest model was trained to identify epochs as either artefact or not artefact. Main results. This model performs well, achieving a balanced accuracy of 0.81, which is as good as manual review of data. Accuracy was not significantly related to the infant age or type of stimulus. Significance. This method provides an objective tool for automated artefact rejection for short epoch, single-channel EEG in neonates and could increase the utility of EEG in neonates in both the clinical and research setting.

The Effect of Caffeine on Movement-Related Cortical Potential Morphology and Detection.

Movement-related cortical potential (MRCP) is observed in EEG recordings prior to a voluntary movement. It has been used for e.g., quantifying motor learning and for brain-computer interfacing (BCIs). The MRCP amplitude is affected by various factors, but the effect of caffeine is underexplored. The aim of this study was to investigate if a cup of coffee with 85 mg caffeine modulated the MRCP amplitude and the classification of MRCPs versus idle activity, which estimates BCI performance. Twenty-six healthy participants performed 2 × 100 ankle dorsiflexion separated by a 10-min break before a cup of coffee was consumed, followed by another 100 movements. EEG was recorded during the movements and divided into epochs, which were averaged to extract three average MRCPs that were compared. Also, idle activity epochs were extracted. Features were extracted from the epochs and classified using random forest analysis. The MRCP amplitude did not change after consuming caffeine. There was a slight increase of two percentage points in the classification accuracy after consuming caffeine. In conclusion, a cup of coffee with 85 mg caffeine does not affect the MRCP amplitude, and improves MRCP-based BCI performance slightly. The findings suggest that drinking coffee is only a minor confounder in MRCP-related studies.

Medium-Sized Solar Cycles in Different Epochs of Solar Activity

Medium-Sized Solar Cycles in Different Epochs of Solar Activity

The Gas Accretion Rate of Galaxies over z ≈ 0–1.3

We present here estimates of the average rates of accretion of neutral gas onto main-sequence galaxies and the conversion of atomic gas to molecular gas in these galaxies at two key epochs in galaxy evolution: (i) z ≈ 1.3–1.0, toward the end of the epoch of peak star formation activity in the Universe, and (ii) z ≈ 1–0, when the star formation activity declines by an order of magnitude. We determine the net gas accretion rate R Acc and the molecular gas formation rate R Mol by combining the relations between the stellar mass and the atomic gas mass, the molecular gas mass, and the star formation rate (SFR) at three epochs, z = 1.3, z = 1.0, and z = 0, with the assumption that galaxies evolve continuously on the star-forming main sequence. We find that, for all galaxies, R Acc is far lower than the average SFR R SFR at z ≈ 1.3–1.0; however, R Mol is similar to R SFR during this interval. Conversely, both R Mol and R Acc are significantly lower than R SFR over the later interval, z ≈ 1–0. We find that massive main-sequence galaxies had already acquired most of their present-day baryonic mass by z ≈ 1.3. At z ≈ 1.3–1.0, the rapid conversion of the existing atomic gas to molecular gas was sufficient to maintain a high average SFR, despite the low net gas accretion rate. However, at later times, the combination of the lower net gas accretion rate and the lower molecular gas formation rate leads to a decline in the fuel available for star formation and results in the observed decrease in the SFR density of the Universe over the last 8 Gyr.

Recurring Activity Discovered on Quasi-Hilda 2009 DQ118

We have discovered two epochs of activity on quasi-Hilda 2009 DQ118. Small bodies that display comet-like activity, such as active asteroids and active quasi-Hildas, are important for understanding the distribution of water and other volatiles throughout the solar system. Through our NASA Partner Citizen Science project, Active Asteroids, volunteers classified archival images of 2009 DQ118 as displaying comet-like activity. By performing an in-depth archival image search, we found over 20 images from UT 2016 March 8–9 with clear signs of a comet-like tail. We then carried out follow-up observations of 2009 DQ118 using the 3.5 m Astrophysical Research Consortium Telescope at Apache Point Observatory, Sunspot, New Mexico, USA and the 6.5 m Magellan Baade Telescope at Las Campanas Observatory, Chile. These images revealed a second epoch of activity associated with the UT 2023 April 22 perihelion passage of 2009 DQ118. We performed photometric analysis of the tail and find that it had a similar apparent length and surface brightness during both epochs. We also explored the orbital history and future of 2009 DQ118 through dynamical simulations. These simulations show that 2009 DQ118 is currently a quasi-Hilda and that it frequently experiences close encounters with Jupiter. We find that 2009 DQ118 is currently on the boundary between asteroidal and cometary orbits. Additionally, it has likely been a Jupiter family comet or Centaur for much of the past 10 kyr and will be in these same regions for the majority of the next 10 kyr. Since both detected epochs of activity occurred near perihelion, the observed activity is consistent with sublimation of volatile ices. 2009 DQ118 is currently observable until ∼mid-October 2023. Further observations would help to characterize the observed activity.

VICTORIA project: The LOFAR HBA Virgo Cluster Survey

Context. The Virgo cluster is the nearest (d = 16.5 Mpc) massive (M ≥ 1014 M⊙) galaxy cluster and is therefore a prime target for studying astrophysical processes in dense large-scale environments. In the radio band, we can probe the nonthermal components of the interstellar medium, the intracluster medium (ICM), and of active galactic nuclei (AGN). This allows an investigation of the impact of the environment on the evolution of galaxies and the contribution of AGN to ICM heating. With the ViCTORIA (VIrgo Cluster multi-Telescope Observations in Radio of Interacting galaxies and AGN) project, we are carrying out multiple wide-field surveys of the Virgo cluster at different frequencies. Aims. We aim to investigate the impact of the environment on the evolution of galaxies and the contribution of AGN to ICM heating – from the inner cluster regions out to beyond the virial radius. Methods. We performed a survey of the cluster at 120–168 MHz using the LOw-Frequency ARray (LOFAR). We imaged a 132 deg2 region of the cluster, reaching an order-of-magnitude greater sensitivity than existing wide-field radio surveys of this field at three times higher spatial resolution compared to other low-frequency observations. We developed a tailored data processing strategy to subtract the bright central radio galaxy M 87 from the data. This allowed us to correct for systematic effects due to ionospheric variation as a function of time and direction. Results. In the final mosaic, which has a resolution of 9″ × 5″, we reach a median noise level of 140 μJy beam−1 inside the virial radius and 280 μJy beam−1 for the full area. We detect 112 Virgo member galaxies and 114 background galaxies. In at least 18 cases, the radio morphology of the cluster member galaxies shows clear signs of ram-pressure stripping. This includes three previously unreported candidates. In addition, we reveal previously undiscovered tails of 150 kpc in length from a previous epoch of AGN activity for NGC 4472 (M 49). While no cluster-scale diffuse radio sources are discovered, we find the presence of an extended radio signature of the W′ group. This feature is coincident with an X-ray filament detected with SRG/eROSITA in the outskirts of the cluster. We speculate that this emission is synchrotron radiation, which could be related to shocks or turbulence from accretion processes. Conclusions. The data published in this paper serve as a valuable resource for future studies. In the follow-up work of the ViCTORIA project, we will use these data for an analysis of environmental effects on the radio properties of star-forming galaxies in Virgo.

The Taverna San Felice Dike (NE of Roccamonfina Volcano): Unraveling Magmatic Intrusion Processes and Volcano‐Tectonics in the Tyrrhenian Margin of the Southern Apennines

AbstractThe Roccamonfina volcano is located within the Garigliano Graben (southern Apennines, Italy) and has been active throughout the Middle‐Late Pleistocene. Along its polyphase volcanic history (630–55 ka), including several caldera‐forming eruptions (385–230 ka), several effusive/mildly explosive monogenetic events occurred along the volcano slopes, within the summit caldera, and along the graben‐bounding carbonate reliefs. In this paper, we present a multidisciplinary study of a mafic magmatic feeder dike intruded within the Meso‐Tertiary carbonates and overlying Lower Pleistocene breccias of Mt Cesima, northeast of the Roccamonfina volcano. We performed a stratigraphic and structural survey of the area and petrographic analyses on several samples of the dike. Results indicate that a ∼1 km long fissure fed an eruption that also emplaced a Strombolian pyroclastic sequence. Petrological data show that an open‐system mafic recharge fueled the tephritic magma that fed the eruption, whereas no evidence of significant pre/syn‐eruptive assimilation of carbonate has been identified. Stratigraphic and petrological data do not allow to firmly constrain the timing of the eruption, which could belong both to the pre‐Brown Leucitic Tuff (>354 ka) and to the post‐White Trachytic Tuffs (<230 ka) epochs of activity of the Roccamonfina volcano. Structural data show that the dike is broadly oriented E‐W and changes direction toward NE‐SW in correspondence with a pre‐existing fault damage zone. We suggest that magma was intruded during an N‐S trending extensional event in the Middle Pleistocene, whose prolonged activity resulted in regional uplift and exhumation of regional significance.

Investigating real-time physical activity behavior using ecological momentary assessment: Effects of mental fatigue and benefit-cost valuations

BackgroundCurrent research investigating the relationship between mental fatigue and physical activity behaviors relies on laboratory-based, experimental studies which lack ecological validity. ObjectiveThis study used ecological momentary assessment (EMA) to assess feelings of mental fatigue and subjective evaluations (benefits and costs) as predictors of moderate-to-vigorous intensity physical activity in the everyday lives of young adults. MethodsOne hundred participants (n = 22 males, n = 78 females, Mage = 20.60 years, 70% meeting or exceeding physical activity guidelines) responded to digital survey prompts up to four times a day and wore an accelerometer for seven consecutive days. Moderate-to-vigorous intensity physical activity in the 180-min time window following each survey prompt was recorded. Data from the 28 survey-moderate-to-vigorous intensity physical activity epochs were analyzed using multilevel mixed-effects linear modelling. ResultsHigher levels of mental fatigue than one’s average level were associated with engaging in fewer moderate-to-vigorous intensity physical activity minutes (p = .004) and lower benefit vs. cost scores (p = .001). Higher benefit vs. cost scores than one’s average level were associated with engaging in more minutes of moderate-to-vigorous intensity physical activity (p < .001). ConclusionsResults are the first to demonstrate outside the lab, that mental fatigue experienced in everyday life may amplify the perceived costs of moderate-to-vigorous intensity physical activity, with both factors playing a potential role in moderate-to-vigorous intensity physical activity decision-making. Future research may apply insights gained from this study in design and testing of real-time interventions promoting moderate-to-vigorous intensity physical activity.

Comet-like Activity Discovered on Quasi-Hilda Asteroid 2009 DQ118

We report evidence of comet-like activity on asteroid 2009 DQ118, a quasi-Hilda object near the 3:2 interior mean-motion resonance with Jupiter. This discovery was made by volunteers as part of the Active Asteroids Citizen Science project, a NASA Partner hosted on the Zooniverse platform. Follow-up archival searches yielded over 20 images of 2009 DQ118 exhibiting a comet-like tail on UT 2016 March 8 and 9 acquired with the Dark Energy Camera on the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory, Chile. These images were taken when 2009 DQ118 was near its 2016 perihelion passage. 2009 DQ118 will next reach perihelion on UT 2023 April 22; hence, the next several months are an excellent time to observe 2009 DQ118 to search for a second epoch of activity for this object.

Gamma-ray flares and broad-band spectral study of PKS 0402-362

ABSTRACTWe study the long-term behaviour of the bright gamma-ray blazar PKS 0402-362. We collected approximately 13 yr of Fermi-LAT data between August 2008 to January 2021 and identified three bright γ-ray activity epochs. The second was found to be the brightest epoch ever seen in this source. We observed most of the γ-ray flare peaks to be asymmetric in profile suggesting a slow cooling time of particles or the varying Doppler factor as the main cause of these flares. The γ-ray spectrum is fitted with PL and LP spectral models, and in both cases, the spectral index is very steep. The γ-ray spectrum does not extend beyond 10 GeV energy suggesting the emission is produced within the BLR. The absence of time lags between optical-IR and γ-ray suggest one zone emission model. Using the above information, we have modelled the broad-band SED with a simple one-zone emission model using the publicly available code ‘GAMERA’. The particle distribution index is found to be the same as expected in diffusive shock acceleration suggesting it as the main mechanism of particle acceleration to very high energy up to 4–6 GeV. Throughout the various flux phases, we noticed that the optical emission is dominated by the thermal disc, suggesting it to be a good source to examine the disc-jet coupling. We postulate that the observed broad-band flares could be linked with perturbation produced in the disc, which propagates to the jet and interacts with the standing shock. However, a more detailed examination is required.

Time Dependence of 50–250 MeV Galactic Cosmic-Ray Protons between Solar Cycles 24 and 25, Measured by the High-energy Particle Detector on board the CSES-01 Satellite

Time-dependent energy spectra of galactic cosmic rays (GCRs) carry crucial information regarding their origin and propagation throughout the interstellar environment. When observed at the Earth, after traversing the interplanetary medium, such spectra are heavily affected by the solar wind and the embedded solar magnetic field permeating the inner sectors of the heliosphere. The activity of the Sun changes significantly over an 11 yr solar cycle—and so does the effect on cosmic particles; this translates into a phenomenon called solar modulation. Moreover, GCR spectra during different epochs of solar activity provide invaluable information for a complete understanding of the plethora of mechanisms taking place in various layers of the Sun’s atmosphere and how they evolve over time. The High-Energy Particle Detector (HEPD-01) has been continuously collecting data since 2018 August, during the quiet phase between solar cycles 24 and 25; the activity of the Sun is slowly but steadily rising and is expected to peak around 2025/2026. In this paper, we present the first spectra for ∼50–250 MeV galactic protons measured by the HEPD-01 instrument—placed on board the CSES-01 satellite—from 2018 August to 2022 March over a one-Carrington-rotation time basis. Such data are compared to the ones from other spaceborne experiments, present (e.g., EPHIN, Parker Solar Probe) and past (PAMELA), and to a state-of-the-art three-dimensional model describing the GCRs propagation through the heliosphere.

Observation of the Solar Eclipse on June 10, 2021 on the Water Vapor Radiometer of the Institute of Applied Astronomy, Russian Academy of Sciences

The results of observations of the solar eclipse on June 10, 2021, which were carried out at the Svetloeobservatory (60.53° N, 29.78° E, Leningrad Province) for the first time using the water vapor radiometerand radio telescopes RT-13 and RT-32 together are presented. The eclipse curves obtained at the radiometeroperating frequencies of 20.7 and 31.4 GHz were compared with the change in the area of the open part of theSun and show good agreement (match to an accuracy of 2% during the cloudless period). Assuming a uniformdistribution of radio brightness across the solar disk, the brightness temperature was estimated to be 9060 ± 380and 8050 ± 300 K at these frequencies, respectively. It was concluded that even in the epoch of a deep minimumof solar activity, the brightness of the solar disk in the microwave range remains unchanged (independentof the cycle number)

Helium Abundance Decrease in ICMEs in 23–24 Solar Cycles

Based on the OMNI database, the influence of the solar activity decrease in solar cycles (SCs) 23–24 on the behavior of the relative helium ions abundance Nα/Np inside interplanetary coronal mass ejections (ICMEs) is investigated. The dependences of the helium abundance on the plasma and interplanetary magnetic field parameters in the epoch of high solar activity (SCs 21–22) and the epoch of low activity (SCs 23–24) are compared. It is shown that Nα/Np significantly decreased in SCs 23–24 compared to SCs 21–22. The general trends of the dependences have not changed with the change of epoch, but the helium abundance dependences on some parameters (for example, the magnitude of the interplanetary magnetic field) have become weaker in the epoch of low activity than they were in the epoch of high activity. In addition, the dependence of the helium abundance on the distance from spacecraft to the ICME axis was revealed; the clearest dependence is observed in magnetic clouds. The Nα/Np maximum is measured at the minimum distance, which confirms the hypothesis of the existence of a helium-enriched electric current inside an ICME.

Metal content of the circumgalactic medium around star-forming galaxies at z ∼ 2.6 as revealed by the VIMOS Ultra-Deep Survey

Context. The circumgalactic medium (CGM) is the location where the interplay between large-scale outflows and accretion onto galaxies occurs. Metals in different ionization states flowing between the circumgalactic and intergalactic mediums are affected by large galactic outflows and low-ionization state inflowing gas. Observational studies on their spatial distribution and their relation with galaxy properties may provide important constraints on models of galaxy formation and evolution. Aims. The main goal of this paper is to provide new insights into the spatial distribution of the circumgalactic of star-forming galaxies at 1.5 &lt; z &lt; 4.5 (⟨z⟩∼2.6) in the peak epoch of cosmic star formation activity in the Universe. We also look for possible correlations between the strength of the low- and high-ionization absorption features (LIS and HIS) and stellar mass, star formation rate, effective radius, and azimuthal angle ϕ that defines the location of the absorbing gas relative to the galaxy disc plane. Methods. The CGM has been primarily detected via the absorption features that it produces on the continuum spectrum of bright background sources. We selected a sample of 238 close pairs from the VIMOS Ultra Deep Survey to examine the spatial distribution of the gas located around star-forming galaxies and generate composite spectra by co-adding spectra of background galaxies that provide different sight-lines across the CGM of star-forming galaxies. Results. We detect LIS (C II and Si II) and HIS (Si IV, C IV) up to separations ⟨b⟩ = 172 kpc and 146 kpc. Beyond this separation, we do not detect any significant signal of CGM absorption in the background composite spectra. Our Lyα, LIS, and HIS rest-frame equivalent width (W0) radial profiles are at the upper envelope of the W0 measurements at lower redshifts, suggesting a potential redshift evolution for the CGM gas content producing these absorptions. We find a correlation between C II and C IV with star formation rate and stellar mass, as well as trends with galaxy size estimated by the effective radius and azimuthal angle. Galaxies with high star formation rate (log[SFR/(M⊙ yr−1)] &gt; 1.5) and stellar mass (log[M⋆/M⊙] &gt; 10.2) show stronger C IV absorptions compared with those low SFR (log[SFR/(M⊙ yr−1)] &lt; 0.9) and low stellar mass (log[M⋆/M⊙] &lt; 9.26). The latter population instead shows stronger C II absorption than their more massive or more star-forming counterparts. We compute the C II/C IVW0 line ratio that confirms the C II and C IV correlations with impact parameter, stellar mass, and star formation rate. We do not find any correlation with ϕ in agreement with other high-redshift studies and in contradiction to what is observed at low redshift where large-scale outflows along the minor axis forming bipolar outflows are detected. Conclusions. We find that the stronger C IV line absorptions in the outer regions of these star-forming galaxies could be explained by stronger outflows in galaxies with higher star formation rates and stellar masses that are capable of projecting the ionized gas up to large distances and/or by stronger UV ionizing radiation in these galaxies that is able to ionize the gas even at large distances. On the other hand, low-mass galaxies show stronger C II absorptions, suggesting larger reservoirs of cold gas that could be explained by a softer radiation field unable to ionize high-ionization state lines or by the galactic fountain scenario where metal-rich gas ejected from previous star formation episodes falls back to the galaxy. These large reservoirs of cold neutral gas around low-mass galaxies could be funnelled into the galaxies and eventually provide the necessary fuel to sustain star formation activity.

The Giant Metrewave Radio Telescope Cold-Hi AT z ≈ 1 Survey

We describe the design, data analysis, and basic results of the Giant Metrewave Radio Telescope Cold-Hi AT z ≈ 1 (GMRT-CATz1) survey, a 510 hr upgraded GMRT Hi 21 cm emission survey of galaxies at z = 0.74−1.45 in the DEEP2 survey fields. The GMRT-CAT z1 survey is aimed at characterizing Hi in galaxies during and just after the epoch of peak star formation activity in the universe, a key epoch in galaxy evolution. We obtained high-quality Hi 21 cm spectra for 11,419 blue star-forming galaxies at z = 0.74−1.45, in seven pointings on the DEEP2 subfields. We detect the stacked Hi 21 cm emission signal of the 11,419 star-forming galaxies, which have an average stellar mass of M * ≈ 1010 M ⊙, at 7.1σ statistical significance, obtaining an average Hi mass of 〈M H i 〉 = (13.7 ± 1.9) × 109 M ⊙. This is significantly higher than the average Hi mass of 〈M H i 〉 = (3.96 ± 0.17) × 109 M ⊙ in star-forming galaxies at z ≈ 0 with an identical stellar-mass distribution. We stack the rest-frame 1.4 GHz continuum emission of our 11,419 galaxies to infer an average star formation rate (SFR) of 8.07 ± 0.82 M ⊙ yr−1. Combining our average Hi mass and average SFR estimates yields an Hi depletion timescale of 1.70 ± 0.29 Gyr, for star-forming galaxies at z ≈ 1, ≈3 times lower than that of local galaxies. We thus find that, although main-sequence galaxies at z ≈ 1 have a high Hi mass, their short Hi depletion timescale is likely to cause quenching of their star formation activity in the absence of rapid gas accretion from the circumgalactic medium.

Dynamics of Large-Scale Solar-Wind Streams Obtained by the Double Superposed Epoch Analysis: 5. Influence of the Solar Activity Decrease

In solar cycles 23–24, solar activity noticeably decreased and, as a result, solar wind parameters decreased. Based on the measurements of the OMNI base for the period 1976–2019, the time profiles of the main solar wind parameters and magnetospheric indices for the main interplanetary drivers of magnetospheric disturbances (solar wind types CIR. Sheath, ejecta and MC) are studied using the double superposed epoch method. The main task of the research is to compare time profiles for the epoch of high solar activity at 21–22 SC and the epoch of low activity at 23–24 SC. The following results were obtained. (1) The analysis did not show a statistically significant change in driver durations during the epoch of minimum. (2) The time profiles of all parameters for all types of SW in the epoch of low activity have the same shape as in the epoch of high activity, but locate at lower values of the parameters. (3) In CIR events, the longitude angle of the solar wind flow has a characteristic S shape; but in the epoch of low activity, it varies in a larger range than in the previous epoch.