Papers for Friday, Aug 13 2021

We present a novel analytic framework to model the steady-state structure of multiphase galactic winds comprised of a hot, volume-filling component and a cold, clumpy component. We first derive general expressions for the structure of the hot phase for arbitrary mass, momentum, and energy sources terms. Next, informed by recent simulations, we parameterize the cloud-wind mass transfer rates, which are set by the competition between turbulent mixing and radiative cooling. This enables us to cast the cloud-wind interaction as a source term for the hot phase and thereby simultaneously solve for the evolution of both phases fully accounting for their bidirectional influence. With this model, we explore the nature of galactic winds over a broad range of conditions. We find that: (i) with realistic parameter choices, we naturally produce a hot, low-density wind that transports energy while entraining a significant flux of cold clouds, (ii) mixing dominates the cold cloud acceleration and decelerates the hot wind, (iii) during mixing thermalization of relative kinetic energy provides significant heating, (iv) systems with low hot-phase mass loading factors and/or star formation rates can sustain higher initial cold phase mass loading factors, but the clouds are quickly shredded, and (v) systems with large hot-phase mass loading factors and/or star formation rates cannot sustain large initial cold-phase mass loading factors, but the clouds tend to grow with radius. Our results highlight the necessity of accounting for the multiphase structure of galactic winds, both physically and observationally, and have important implications for feedback in galactic systems.

Recent observations and simulations have challenged the long-held paradigm that mergers are the dominant mechanism driving the growth of both galaxies and supermassive black holes (SMBH), in favour of non-merger (secular) processes. In this pilot study of merger-free SMBH and galaxy growth, we use Keck Cosmic Web Imager spectral observations to examine four low-redshift ($0.043 < z < 0.073$) disk-dominated `bulgeless' galaxies hosting luminous AGN, assumed to be merger-free. We detect blueshifted broadened [OIII] emission from outflows in all four sources, which the \oiii/\hbeta~ratios reveal are ionised by the AGN. We calculate outflow rates in the range $0.12-0.7~\rm{M}_{\odot}~\rm{yr}^{-1}$, with velocities of $675-1710~\rm{km}~\rm{s}^{-1}$, large radial extents of $0.6-2.4~\rm{kpc}$, and SMBH accretion rates of $0.02-0.07~\rm{M}_{\odot}~\rm{yr}^{-1}$. We find that the outflow rates, kinematics, and energy injection rates are typical of the wider population of low-redshift AGN, and have velocities exceeding the galaxy escape velocity by a factor of $\sim30$, suggesting that these outflows will have a substantial impact through AGN feedback. Therefore, if both merger-driven and non-merger-driven SMBH growth lead to co-evolution, this suggests that co-evolution is regulated by feedback in both scenarios. Simulations find that bars and spiral arms can drive inflows to galactic centres at rates an order of magnitude larger than the combined SMBH accretion and outflow rates of our four targets. This work therefore provides further evidence that non-merger processes are sufficient to fuel SMBH growth and AGN outflows in disk galaxies.

We perform joint modeling of the composite rest-frame far-UV (FUV) and optical spectra of redshift 1.85<z<3.49 star-forming galaxies to deduce key properties of the massive stars, ionized ISM, and neutral ISM, with the aim of investigating the principal factors affecting the production and escape of Ly-alpha (Lya) photons. Our sample consists of 136 galaxies with deep Keck/LRIS and MOSFIRE spectra covering, respectively, Ly-beta through CIII] 1907, 1909; and [OII], [NeIII], H-beta, [OIII], H-alpha, [NII], and [SII]. Spectral and photoionization modeling indicate that the galaxies are uniformly consistent with stellar population synthesis models that include the effects of stellar binarity. Over the dynamic range of our sample, there is little variation in stellar and nebular abundance with Lya equivalent width, W(Lya), and only a marginal anti-correlation between age and W(Lya). The inferred range of ionizing spectral shapes is insufficient to solely account for the variation in W(Lya). Rather, the covering fraction of optically-thick HI appears to be the principal factor modulating the escape of Lya, with most of the Lya photons in down-the-barrel observations of galaxies escaping through low-column-density or ionized channels in the ISM. Our analysis shows that a high star-formation-rate surface density, Sigma_SFR, particularly when coupled with a low galaxy potential (i.e., low stellar mass), can aid in reducing the covering fraction and ease the escape of Lya photons. We conclude with a discussion of the implications of our results for the escape of ionizing radiation at high redshift.

Dynamical studies of dense structures within molecular clouds often conclude that the most massive clumps contain too little kinetic energy for virial equilibrium, unless they are magnetized to an unexpected degree. This raises questions about how such a state might arise, and how it might persist long enough to represent the population of massive clumps. In an effort to re-examine the origins of this conclusion, we use ammonia line data from the Green Bank Ammonia Survey and Planck-calibrated dust emission data from Herschel to estimate the masses and kinetic and gravitational energies for dense clumps in the Gould Belt clouds. We show that several types of systematic error can enhance the appearance of low kinetic-to-gravitational energy ratios: insufficient removal of foreground and background material; ignoring the kinetic energy associated with velocity differences across a resolved cloud; and over-correcting for stratification when evaluating the gravitational energy. Using an analysis designed to avoid these errors, we find that the most massive Gould Belt clumps harbor virial motions, rather than sub-virial ones. As a byproduct, we present a catalog of masses, energies, and virial energy ratios for 85 Gould Belt clumps.

We constrain the average episodic quasar lifetime (as in steady-state accretion) using two statistics of quasars that are recently turned off (i.e., dimmed by a large factor): 1) the fraction of turned-off quasars in a statistical sample photometrically observed over an extended period (e.g., $\Delta t=20$ yrs); 2) the fraction of massive galaxies that show 'orphan' broad MgII emission, argued to be short-lived echoes of recently turned-off quasars. The two statistics constrain the average episodic quasar lifetime to be hundreds to thousands of years. Much longer (or shorter) episodic lifetimes are strongly disfavored by these observations. This average episodic lifetime is broadly consistent with the infall timescale (viscous time) in the standard accretion disk model for quasars, suggesting that quasar episodes are governed by accretion disk physics rather than by the gas supply on much larger scales. Compared with the cumulative quasar lifetime of $\sim 10^6-10^8\,$yrs constrained from quasar clustering and massive black hole demographics, our results suggest that there are $\sim 10^3-10^5$ episodes of quasar accretion during the assembly history of the supermassive black hole. Such short episodes should be clustered over intervals of $\sim 10^4\,$yrs to account for the sizes of ionized narrow-line regions in quasars. Our statistical argument also dictates that there will always be a small fraction of extreme variability quasars caught in 'state transitions' over multi-year observing windows, despite the much longer episodic lifetime. These transitions could occur in a rather abrupt fashion during non-steady accretion.

We present a study of emission lines of small hydrocarbons C$_2$H and $c$-C$_3$H$_2$, and COMs precursors H$_2$CO and CH$_3$OH in order to better understand the possible chemical link between the molecular abundances and UV radiation field in photodissociation regions (PDRs). We study two PDRs around extended and compact HII regions with $G \leq 50$~Habings in the S235 star-forming complex. We find the highest abundances of both hydrocarbons on the edges of molecular clumps, while $c$-C$_3$H$_2$ is also abundant in the low-density expanding PDR around compact HII region S235\,A. We see the highest methanol column density towards the positions with the UV~field $G\approx 20-30$~Habings and explain them by reactive desorption from the dust grains. The $N_{\rm C_2H}/N_{\rm CH_3OH}$ ratio is lower by a factor of few or the order of magnitude in comparison with the Horsehead and Orion Bar PDRs. The ratio is similar to the value observed in hot corinos in the Perseus cloud. We conclude that ion-molecular and grain surface chemical routes rule the molecular abundances in the PDRs, and the PDRs inherit molecular abundances from the previous dark stage of molecular cloud evolution in spite of massive stars already emitting in optics.

Accretion disks around supermassive black holes in active galactic nuclei produce continuum radiation at ultraviolet and optical wavelengths. Physical processes in the accretion flow lead to stochastic variability of this emission on a wide range of timescales. We measure the optical continuum variability observed in 67 active galactic nuclei and the characteristic timescale at which the variability power spectrum flattens. We find a correlation between this timescale and the black hole mass, extending over the entire mass range of supermassive black holes. This timescale is consistent with the expected thermal timescale at the ultraviolet-emitting radius in standard accretion disk theory. Accreting white dwarfs lie close to this correlation, suggesting a common process for all accretion disks.

When a flux-limited quasar sample is observed at later times, there will be more dimmed quasars than brightened ones, due to a selection bias induced at the time of sample selection. Quasars are continuously varying and there are more fainter quasars than brighter ones. At the time of selection, even symmetrical variability will result in more quasars with their instantaneous fluxes scattered above the flux limit than those scattered below, leading to an asymmetry in flux changes over time. The same bias would lead to an asymmetry in the ensemble structure function (SF) of the sample such that the SF based on pairs with increasing fluxes will be slightly smaller than that based on pairs with decreasing fluxes. We use simulated time-symmetric quasar light curves based on the damped random walk prescription to illustrate the effects of this bias. The level of this bias depends on the sample, the threshold of magnitude changes, and the coverage of light curves, but the general behaviors are consistent. In particular, the simulations matched to recent observational studies with decade-long light curves produce an asymmetry in the SF measurements at the few percent level, similar to the observed values. These results provide a cautionary note on the reported time asymmetry in some recent quasar variability studies.

Here, I overview one of the available techniques for the analysis of broad-band spectropolarimetric data, the Stokes QU-fitting. Since broad-band receivers have been installed at most radio facilities, the collection of radio data, both the total intensity and the linear polarization, is revealing interesting features in their spectra. The polarized light, and therefore its properties, i.e. the fractional polarization and the polarized angle, are now finally well sampled in wide wavelength ranges. The new complex behaviors revealed by the data can be studied using the Stokes QU-fitting, which consists of modeling the Stokes parameters Q and U using wavelength-dependent analytical models, available in the literature. This technique provides a very good diagnostic of the nature and structure of the magnetized plasma, with the possibility to identify complex structures, internal or external, of the source of study. A summary of the available and most used models describing the polarization behavior, is presented. Moreover, some of the most significant observational works which use this technique are also summarized.

Radio magnetars are exotic sources noted for their diverse spectro-temporal phenomenology and pulse profile variations over weeks to months. Unusual for radio magnetars, the Galactic Center (GC) magnetar $\rm PSR~J1745-2900$ has been continually active since its discovery in 2013. We monitored the GC magnetar at $\rm 4-8~GHz$ for 6 hours in August$-$September 2019 using the Robert C. Byrd Green Bank Telescope. During our observations, the GC magnetar emitted a flat fluence spectrum over $\rm 5-8~GHz$ to within $2\sigma$ uncertainty. From our data, we estimate a $\rm 6.4~GHz$ period-averaged flux density, $\overline{S}_{6.4} \approx (240 \pm 5)~\mu$Jy. Tracking the temporal evolution of $\overline{S}_{6.4}$, we infer a gradual weakening of GC magnetar activity during $2016-2019$ relative to that between $2013-2015.5$. Typical single pulses detected in our study reveal marginally resolved sub-pulses with opposing spectral indices, a feature characteristic of radio magnetars but unseen in rotation-powered pulsars. However, unlike in fast radio bursts, these sub-pulses exhibit no perceptible radio frequency drifts. Throughout our observing span, $\rm \simeq 5~ms$ scattered pulses significantly jitter within two stable emission components of widths, $\rm 220~ms$ and $\rm 140~ms$, respectively, in the average pulse profile.

Magakian et al. (2019) called attention to the current bright state of LkHa 225 South, which over the past two decades has changed from $>20^m$ to $<13^m$. We present recent optical photometric monitoring that shows colorless, non-sinusoidal, periodic brightness variations. The oscillations occur every 43 days, and have amplitude $\sim$0.7 mag with some variation among cycles. We also present new flux-calibrated optical and near-infrared spectroscopy, which we model in terms of a keplerian disk. Additional high dispersion spectra demonstrate the similarity of the absorption line pattern to some categories of ``mixed temperature" accretion outburst objects. At blue wavelengths, LkHa 225 South has a pure absorption spectrum and is a good spectral match to the FU Ori stars V1515 Cyg and V1057 Cyg. At red optical and infrared wavelengths, however, the spectrum is more similar to Gaia 19ajj, showing emission in TiO, CO, and metals. Sr II lines indicate a low surface gravity atmosphere. There are also signatures of a strong wind/outflow. LkHa 225 South was moderately bright in early 1950's as well as in late 1980's, with evidence for deep fades during intervening epochs. The body of evidence suggests that LkHa225 South is another case of a source with episodically enhanced accretion that causes brightening by orders of magnitude, and development of a hot absorption spectrum and warm wind. It is similar to Gaia 19ajj, but also reminiscent in its long brightening time and brightness oscillation near peak, to the embedded sources L1634 IRS7 and ESO Ha 99.

In this study we present constraints on the deceleration (q) and jerk (j) parameters using the late time integrated Sachs-Wolfe effect, type Ia supernovae, and H(z) data . We first directly measure the deceleration and jerk parameters using the cosmic chronometers data with the Taylor series expression of H(z).However, due to the unusual variations in the deceleration parameter with slight changes in other parameters like snap (s) and lerk (l), we found that direct measurements using the series expression of the H(z) is not a suitable method for non-Lambda-CDM models and so we will need to derive the deceleration parameter after constraining density parameters and dark energy equation of state parameters. Then we present derived values of the deceleration parameter from Lambda CDM, WCDM and CPL models. We also discuss the transition redshift (zt) in relation with the deceleration parameter.

Habitability has been generally defined as the capability of an environment to support life. Ecologists have been using Habitat Suitability Models (HSMs) for more than four decades to study the habitability of Earth from local to global scales. Astrobiologists have been proposing different habitability models for some time, with little integration and consistency among them, being different in function to those used by ecologists. Habitability models are not only used to determine if environments are habitable or not, but they also are used to characterize what key factors are responsible for the gradual transition from low to high habitability states. Here we review and compare some of the different models used by ecologists and astrobiologists and suggest how they could be integrated into new habitability standards. Such standards will help to improve the comparison and characterization of potentially habitable environments, prioritize target selections, and study correlations between habitability and biosignatures. Habitability models are the foundation of planetary habitability science and the synergy between ecologists and astrobiologists is necessary to expand our understanding of the habitability of Earth, the Solar System, and extrasolar planets.

The black-hole X-ray transient MAXI J1820+070 (=ASSASN-18ey) discovered in March 2018 was one of the optically brightest ever seen, which has resulted in very detailed optical outburst light-curves being obtained. We combine them here with X-ray and radio light-curves to show the major geometric changes the source undergoes. We present a detailed temporal analysis which reveals the presence of remarkably high amplitude (>0.5 mag) modulations, which evolve from the superhump (16.87 h) period towards the presumed orbital (16.45 h) period. These modulations appear ~87d after the outburst began, and follow the Swift/BAT hard X-ray light-curve, which peaks 4 days before the radio flare and jet ejection, when the source undergoes a rapid hard to soft state transition. The optical modulation then moves closer to the orbital period, with a light curve peak that drifts slowly in orbital phase from ~0.8 to ~0.3 during the soft state. We propose that the unprecedentedly large amplitude modulation requires a warp in the disc in order to provide a large enough radiating area, and for the warp to be irradiation-driven. Its sudden turn-on implies a change in the inner disc geometry which raises the hard X-ray emitting component to a height where it can illuminate the warped outer disc regions.

We perform a flexion based weak gravitational analysis of the first two Hubble Frontier Field clusters: Abell 2744 and MACS 0416. A parametric method for using projected flexion signals as a probe of cluster member mass is described in detail. The normalization and slope of a $L-\theta_E$ (as a proxy for $L-\sigma$) scaling relation in each cluster is determined using measured flexion signals. A parallel field analysis is undertaken concurrently to provide a baseline measure of method effectiveness. We find an agreement in the Faber-Jackson slope $\ell$ associated with galaxy age and morphology for both clusters, as well as theoretical distinction in the cluster normalization mass.

We present the third and final data release of the K2 Galactic Archaeology Program (K2 GAP) for Campaigns C1-C8 and C10-C18. We provide asteroseismic radius and mass coefficients, $\kappa_R$ and $\kappa_M$, for $\sim 19,000$ red giant stars, which translate directly to radius and mass given a temperature. As such, K2 GAP DR3 represents the largest asteroseismic sample in the literature to date. K2 GAP DR3 stellar parameters are calibrated to be on an absolute parallactic scale based on Gaia DR2, with red giant branch and red clump evolutionary state classifications provided via a machine-learning approach. Combining these stellar parameters with GALAH DR3 spectroscopy, we determine asteroseismic ages with precisions of $\sim 20-30\%$ and compare age-abundance relations to Galactic chemical evolution models among both low- and high-$\alpha$ populations for $\alpha$, light, iron-peak, and neutron-capture elements. We confirm recent indications in the literature of both increased Ba production at late Galactic times, as well as significant contribution to r-process enrichment from prompt sources associated with, e.g., core-collapse supernovae. With an eye toward other Galactic archaeology applications, we characterize K2 GAP DR3 uncertainties and completeness using injection tests, suggesting K2 GAP DR3 is largely unbiased in mass/age and with uncertainties of $2.9\%\,(\rm{stat.})\,\pm0.1\%\,(\rm{syst.})$ & $6.7\%\,(\rm{stat.})\,\pm0.3\%\,(\rm{syst.})$ in $\kappa_R$ & $\kappa_M$ for red giant branch stars and $4.7\%\,(\rm{stat.})\,\pm0.3\%\,(\rm{syst.})$ & $11\%\,(\rm{stat.})\,\pm0.9\%\,(\rm{syst.})$ for red clump stars. We also identify percent-level asteroseismic systematics, which are likely related to the time baseline of the underlying data, and which therefore should be considered in TESS asteroseismic analysis.

VERITAS is one of the world's most sensitive detectors of astrophysical very high energy (VHE; E > 100 GeV) gamma rays. This observatory has operated for ~14 years, and nearly 7,000 hours of its observations have been targeted on active galactic nuclei (AGN). Approximately 300 AGN were observed with VERITAS, and 40 are detected. These studies are generally accompanied by contemporaneous, broadband observations, which enable detailed probes of the underlying jet-powered processes. Recent scientific results from VERITAS AGN observations are presented.

The gamma-ray blazar TXS 0506+056 was found with an enhanced gamma-ray emission state in spatial and temporal coincidence with the IceCube high energy neutrino event IC170922A. This is the most significant association by far between a high-energy neutrino event and a blazar in a flaring state. Studying the time evolution and spectral behavior of the blazar emission may help in identifying the sources of the diffuse neutrino flux observed by IceCube and the origin of energetic cosmic rays. TXS 0506+056 was detected by the VERITAS gamma-ray observatory with a significance of 5.8 standard deviations above 110 GeV in a 35 hour data set collected between September 23, 2017 and February 6, 2018. Here we will present results from recent VERITAS observations and an associated multiwavelength campaign, collected between October 10, 2018 to March 1, 2021. A relatively quiet very high energy gamma-ray emission state was observed during this time period, and flux upper limits are used to constrain the potential variability of this blazar.

Observations of powerful radio waves from neutron star magnetospheres raise the question of how strong waves interact with particles in a strong background magnetic field $B_{bg}$. This problem is examined by solving the particle motion in the wave. Remarkably, waves with amplitudes $E_0>B_{bg}$ pump particle energy via repeating resonance events, quickly reaching the radiation reaction limit. As a result, the wave is scattered with a huge cross section. This fact has great implications for models of fast radio bursts and magnetars. Particles accelerated in the wave emit gamma-rays, which can trigger an $e^\pm$ avalanche and, instead of silent escape, the wave will produce X-ray fireworks.

The stellar mass-to-light ratio gradient in SDSS $r-$band $\nabla (M_*/L_r)$ of a galaxy depends on its mass assembly history, which is imprinted in its morphology and gradients of age, metallicity, and stellar initial mass function (IMF). Taking a MaNGA sample of 2051 galaxies with stellar masses ranging from $10^9$ to $10^{12}M_\odot$ released in SDSS DR15, we focus on face-on galaxies, without merger and bar signatures, and investigate the dependence of the 2D $\nabla (M_*/L_r)$ on other galaxy properties, including $M_*/L_r$-colour relationships by assuming a fixed Salpeter IMF as the mass normalization reference. The median gradient is $\nabla M_*/L_r\sim -0.1$ (i.e., the $M_*/L_r$ is larger at the centre) for massive galaxies, becomes flat around $M_*\sim 10^{10} M_{\odot}$ and change sign to $\nabla M_*/L_r\sim 0.1$ at the lowest masses. The $M_*/L_r$ inside a half light radius increases with increasing galaxy stellar mass; in each mass bin, early-type galaxies have the highest value, while pure-disk late-type galaxies have the smallest. Correlation analyses suggest that the mass-weighted stellar age is the dominant parameter influencing the $M_*/L_r$ profile, since a luminosity-weighted age is easily affected by star formation when the specific star formation rate (sSFR) inside the half light radius is higher than $10^{-3} {\rm Gyr}^{-1}$. With increased sSFR gradient, one can obtain a steeper negative $\nabla (M_*/L_r)$. The scatter in the slopes of $M_*/L$-colour relations increases with increasing sSFR, for example, the slope for post-starburst galaxies can be flattened to $0.45$ from the global value $0.87$ in the $M_*/L$ vs. $g-r$ diagram. Hence converting galaxy colours to $M_*/L$ should be done carefully, especially for those galaxies with young luminosity-weighted stellar ages, which can have quite different star formation histories.

We analyse \'Echelle spectra of $\theta^1$ Ori F obtained by us on six nights unevenly distributed along six years; we identify several hundred spectral lines and measure, for the first time, the star's heliocentric radial velocity. We also collect and discuss previously published photometry of $\theta^1$ OriF . We find that $\theta^1$ Ori F is a Chemically Peculiar (CP) star with overabundant silicon and phosphorus, and possibly other elements as well. From the singly ionised Fe, Cr and Ti lines we estimate its spectral type to be between B7 and B8. The radial velocity of $\theta^1$ Ori F is possibly marginally variable, with an average of $24 \pm 4.2$ kms, (standard deviation), in good agreement with the mean radial velocity of the Orion Nebula Cluster members, and about 5 kms smaller than the average of the other Trapezium components. We cast doubt on the coeval nature of this star relative to the other Trapezium components, and present arguments that almost certainly exclude its membership to the Orion Trapezium. $\theta^1$ Ori F turns out to be enigmatic in several respects, and is probably an important link for understanding the evolutionary stage at which the CP phenomenon sets on.

The IceCube Neutrino Observatory at the South Pole detects Cherenkov light emitted by charged secondary particles created by primary neutrino interactions. Double pulse waveforms can arise from charged current interactions of astrophysical tau neutrinos with nucleons in the ice and the subsequent decay of tau leptons. The previous 8-year tau double pulse analysis found three tau neutrino candidate events. Among them, the most promising one observed in 2014 is located very near the dust layer in the middle of the detector. A posterior analysis on this event will be presented in this paper, using a new ice model treatment with continuously varying nuisance parameters to do the targeted Monte Carlo re-simulation for tau and other background neutrino ensembles. The impact of different ice models on the expected signal and background statistics will also be discussed.

We present a general method for computing the gravitational radiation arising from the motion of bubble walls or thin fluid shells in cosmological phase transitions. We discuss the application of this method to different wall kinematics. In particular, we derive general expressions for the bubble collision mechanism and the so-called bulk flow model, and we also consider deformations from the spherical bubble shape. We calculate the gravitational wave spectrum for a specific model of deformations on a definite size scale.

We explore the joint implications of ultrahigh energy cosmic ray (UHECR) source environments -- constrained by the spectrum and composition of UHECRs -- and the observed high energy astrophysical neutrino spectrum. Acceleration mechanisms producing power-law CR spectra $\propto E^{-2}$ are compatible with UHECR data, if CRs at high rigidities are in the quasi-ballistic diffusion regime as they escape their source environment. Both gas- and photon-dominated source environments are able to account for UHECR observations, however photon-dominated sources do so with a higher degree of accuracy. However, gas-dominated sources are in tension with current neutrino constraints. Accurate measurement of the neutrino flux at $\sim 10$ PeV will provide crucial information on the viability of gas-dominated sources, as well as whether diffusive shock acceleration is consistent with UHECR observations. We also show that UHECR sources are able to give a good fit to the high energy portion of the astrophysical neutrino spectrum, above $\sim$ PeV. This common origin of UHECRs and high energy astrophysical neutrinos is natural if air shower data is interpreted with the \textsc{Sibyll2.3c} hadronic interaction model, which gives the best-fit to UHECRs and astrophysical neutrinos in the same part of parameter space, but not for EPOS-LHC.

Cosmic neutrinos are unique probes of the high energy universe. IceCube has discovered a diffuse astrophysical neutrino flux since 2013, but their origin remains elusive. The potential sources could include, for example, active galactic nuclei, gamma-ray bursts and star burst galaxies. To resolve those scenarios, higher statistics and better angular resolution of astrophysical neutrinos are needed. An optical module with larger photon collection area and more precise timing resolution in a next generation neutrino telescope could help. Silicon photon multipliers (SiPMs), with high quantum efficiency and fast responding time, combining with traditional PMTs, could boost photon detection efficiency and pointing capability. We will present a study on exploring the benefits of combining multiple PMTs and SiPMs in an optical module.

We present performance studies of a segmented optical module for the IceCube-Gen2 detector. Based on the experience gained in sensor development for the IceCube Upgrade, the new sensor will consist of up to eighteen 4 inch PMTs housed in a transparent pressure vessel, providing homogeneous angular coverage. The use of custom molded optical `gel pads' around the PMTs enhances the photon capture rate via total internal reflection at the gel-air interface. This contribution presents simulation studies of various sensor, PMT, and gel pad geometries aimed at optimizing the sensitivity of the optical module in the face of confined space and harsh environmental conditions at the South Pole.

Star formation can be triggered by compression from shock waves. In this study, we investigated the interaction of hydrodynamic shocks with Bonnor-Ebert spheres using 3D hydrodynamical simulations with self-gravity. Our simulations indicated that the cloud evolution primarily depends on two parameters: the shock speed and initial cloud radius. The stronger shock can compress the cloud more efficiently, and when the central region becomes gravitationally unstable, a shock triggers the cloud contraction. However, if it is excessively strong, it shreds the cloud more violently and the cloud is destroyed. From simple theoretical considerations, we derived the condition of triggered gravitational collapse, which agreed with the simulation results. Introducing sink particles, we followed the further evolution after star formation. Since stronger shocks tend to shred the cloud material more efficiently, the stronger the shock is, the smaller the final (asymptotic) masses of the stars formed (i.e., sink particles) become. In addition, the shock accelerates the cloud, promoting mixing of shock-accelerated interstellar medium gas. As a result, the separation between the sink particles and the shocked cloud center and their relative speed increase over time. We also investigated the effect of cloud turbulence on shock-cloud interaction. We observed that the cloud turbulence prevents rapid cloud contraction; thus, the turbulent cloud is destroyed more rapidly than the thermally-supported cloud. Therefore, the masses of stars formed become smaller. Our simulations can provide a general guide to the evolutionary process of dense cores and Bok globules impacted by shocks.

IceAct is a proposed surface array of compact (50 cm diameter) and cost-effective Imaging Air Cherenkov Telescopes installed at the site of the IceCube Neutrino Observatory at the geographic South Pole. Since January 2019, two IceAct telescope demonstrators, featuring 61 silicon pho- tomultiplier (SiPM) pixels have been taking data in the center of the IceTop surface array during the austral winter. We present the first analysis of hybrid cosmic ray events detected by the IceAct imaging air-Cherenkov telescopes in coincidence with the IceCube Neutrino Observatory, includ- ing the IceTop surface array and the IceCube in-ice array. By featuring an energy threshold of about 10 TeV and a wide field-of-view, the IceAct telescopes show promising capabilities of im- proving current cosmic ray composition studies: measuring the Cherenkov light emissions in the atmosphere adds new information about the shower development not accessible with the current detectors, enabling significantly better primary particle type discrimination on a statistical basis. The hybrid measurement also allows for detailed feasibility studies of detector cross-calibration and of cosmic ray veto capabilities for neutrino analyses. We present the performance of the telescopes, the results from the analysis of two years of data, and an outlook of a hybrid simulation for a future telescope array.

Modern multiwavelength observations of star-forming regions that reveal highly-structured molecular clouds require adequate extraction methods that would provide both detection of the structures and their accurate measurements. Omnipresence of filamentary structures and their physical connection to prestellar cores demand methods that are able to disentangle and extract both sources and filaments. It is fundamentally important to test all extraction methods to compare their detection and measurement qualities and fully understand their capabilities, before their scientific applications. A recent publication described getsf, the new method for source and filament extraction that employs separation of the structural components, a successor to getsources, getfilaments, and getimages (collectively referred to as getold). This paper describes a detailed benchmarking of both getsf and getold using two multicomponent, multiwavelength benchmarks resembling the Herschel observations of the nearby star-forming regions. Each benchmark consists of simulated images at six Herschel wavelengths and one additional surface density image with a 13 arcsec resolution. The structural components of the benchmarks include a background cloud, a dense filament, hundreds of starless and protostellar cores, and instrumental noise. Five variants of benchmark images of different complexity are used to perform the source and filament extractions with getsf and getold. A formalism for evaluating source detection and measurement qualities is presented, allowing quantitative comparisons of extraction methods in terms of their completeness, reliability, and goodness, as well as the detection and measurement accuracies and the overall quality. A detailed analysis shows that getsf has better qualities than getold and that the best choice for source detection is the high-resolution surface density.

Eruptive activity in the solar corona can often lead to the propagation of shock waves. In the radio domain the primary signature of such shocks are type II radio bursts, observed in dynamic spectra as bands of emission slowly drifting towards lower frequencies over time. These radio bursts can sometimes have inhomogeneous and fragmented fine structure, but the cause of this fine structure is currently unclear. Here we observe a type II radio burst on 2019-March-20th using the New Extension in Nan\c{c}ay Upgrading LOFAR (NenuFAR), a radio interferometer observing between 10-85 MHz. We show that the distribution of size-scales of density perturbations associated with the type II fine structure follows a power law with a spectral index in the range of $\alpha=-1.7$ to -2.0, which closely matches the value of $-5/3$ expected of fully developed turbulence. We determine this turbulence to be upstream of the shock, in background coronal plasma at a heliocentric distance of $\sim$2 R$_{\odot}$. The observed inertial size-scales of the turbulent density inhomogeneities range from $\sim$62 Mm to $\sim$209 km. This shows that type II fine structure and fragmentation can be due to shock propagation through an inhomogeneous and turbulent coronal plasma, and we discuss the implications of this on electron acceleration in the coronal shock.

The short-term X-ray variability of tidal disruption events (TDEs) and its similarities with active galactic nuclei (AGN) are poorly understood. In this work, we show the diversity of TDE's short-term X-ray variability, and take Swift J1644+57 as an example to study the evolution of various properties related to the short-term X-ray variability, such as the X-ray flux distribution, power spectral density (PSD), rms variability, time lag and coherence spectra. We find that the flux distribution of Swift J1644+57 has a lognormal form in the normal state, but deviates from it significantly in the dipping state, thereby implying different physical mechanisms in the two states. We also find that during the first two XMM-Newton observations in the dipping state, Swift J1644+57 exhibited different variability patterns, which are characterized by steeper PSDs and larger rms than the normal state. A significant soft X-ray lag is detected in these two observations, which is ~50 s between 0.3-1 keV and 2-10 keV with a high coherence. Using the 2-10 keV rms of 0.10-0.50, the black hole mass of Swift J1644+57 is estimated to be $(0.6-7.9)\times10^{6}M_{\odot}$, but the variation of rms as the TDE evolves introduces a large uncertainty. Finally, we discuss the value of conducting similar studies on other TDEs, especially in the coming era of time-domain astronomy when a lot more TDEs will be discovered in X-rays promptly. This also heralds a significant increase in the demand for deep follow-up observations of X-ray selected TDEs with X-ray telescopes of large effective areas and long orbital periods.

We present the ALMA view of 11 main-sequence DSFGs, (sub-)millimeter selected in the GOODS-S field, and spectroscopically confirmed to be at the peak of Cosmic SFH (z = 2-3). Our study combines the analysis of galaxy SED with ALMA continuum and CO spectral emission, by using ALMA Science Archive products at the highest spatial resolution currently available for our sample (< 1 arcsec). We include galaxy multi-band images and photometry (in the optical, radio and X-rays) to investigate the interlink between dusty, gaseous and stellar components and the eventual presence of AGN. We use multi-band sizes and morphologies to gain an insight on the processes that lead galaxy evolution, e.g. gas condensation, star formation, AGN feedback. The 11 DSFGs are very compact in the (sub-)millimeter (median r(ALMA) = 1.15 kpc), while the optical emission extends tolarger radii (median r(H)/r(ALMA) = 2.05). CO lines reveal the presence of a rotating disc of molecular gas, but we can not exclude either the presence of interactions and/or molecular outflows. Images at higher (spectral and spatial) resolution are needed to disentangle from the possible scenarios. Most of the galaxies are caught in the compaction phase, when gas cools and falls into galaxy centre, fuelling the dusty burst of star formation and the growing nucleus. We expect these DSFGs to be the high-zstar-forming counterparts of massive quiescent galaxies. Some features of CO emission in three galaxies are suggestive of forthcoming/ongoing AGN feedback, that is thought to trigger the morphological transition from star-forming disks to ETGs.

We present VOLKS2, the second release of "VLBI Observation for transient Localization Keen Searcher". The pipeline aims at transient search in regular VLBI observations as well as detection of single pulses from known sources in dedicated VLBI observations. The underlying method takes the idea of geodetic VLBI data processing, including fringe fitting to maximize the signal power and geodetic VLBI solving for localization. By filtering the candidate signals with multiple windows within a baseline and by cross matching with multiple baselines, RFIs are eliminated effectively. Unlike the station auto spectrum based method, RFI flagging is not required in the VOLKS2 pipeline. EVN observation (EL060) is carried out, so as to verify the pipeline's detection efficiency and localization accuracy in the whole FoV. The pipeline is parallelized with MPI and further accelerated with GPU, so as to exploit the hardware resources of modern GPU clusters. We can prove that, with proper optimization, VOLKS2 could achieve comparable performance as auto spectrum based pipelines. All the code and documents are publicly available, in the hope that our pipeline is useful for radio transient studies.

Ground-based $\gamma$-ray observatories, such as the VERITAS array of imaging atmospheric Cherenkov telescopes, provide insight into very-high-energy (VHE, $\mathrm{E}>100\,\mathrm{GeV}$) astrophysical transient events. Examples include the evaporation of primordial black holes, gamma-ray bursts and flaring blazars. Identifying such events with a serendipitous location and time of occurrence is difficult. Thus, employing a robust search method becomes crucial. An implementation of a transient detection method based on deep-learning techniques for VERITAS will be presented. This data-driven approach significantly reduces the dependency on the characterization of the instrument response and the modelling of the expected transient signal. The response of the instrument is affected by various factors, such as the elevation of the source and the night sky background. The study of these effects allows enhancing the deep learning method with additional parameters to infer their influences on the data. This improves the performance and stability for a wide range of observational conditions. We illustrate our method for an historic flare of the blazar BL Lac that was detected by VERITAS in October 2016. We find a promising performance for the detection of such a flare in timescales of minutes that compares well with the VERITAS standard analysis.

We analysed 68 candidate planetary systems first identified during Campaigns 5 and 6 (C5 and C6) of the NASA \textit{K2} mission. We set out to validate these systems by using a suite of follow-up observations, including adaptive optics, speckle imaging, and reconnaissance spectroscopy. The overlap between C5 with C16 and C18, and C6 with C17, yields lightcurves with long baselines that allow us to measure the transit ephemeris very precisely, revisit single transit candidates identified in earlier campaigns, and search for additional transiting planets with longer periods not detectable in previous works. Using \texttt{vespa}, we compute false positive probabilities of less than 1\% for 37 candidates orbiting 29 unique host stars and hence statistically validate them as planets. These planets have a typical size of $2.2R_{\oplus}$ and orbital periods between 1.99 and 52.71 days. We highlight interesting systems including a sub-Neptune with the longest period detected by \textit{K2}, sub-Saturns around F stars, several multi-planetary systems in a variety of architectures. These results show that a wealth of planetary systems still remains in the \textit{K2} data, some of which can be validated using minimal follow-up observations and taking advantage of analyses presented in previous catalogs.

The IceCube Neutrino Observatory will be upgraded with more than 700 additional optical sensor modules and new calibration devices. Improved calibration will enhance IceCube's physics capabilities both at low and high neutrino energies. An important ingredient for good angular resolution of the observatory is precise calibration of the positions of optical sensors. Ten acoustic modules, which are capable of receiving and transmitting acoustic signals, will be attached to the strings. These signals can additionally be detected by compact acoustic sensors inside some of the optical sensor modules. With this system we aim for calibration of the detectors' geometry with a precision better than 10 cm by means of trilateration of the propagation times of acoustic signals. This new method will allow for an improved and complementary geometry calibration with respect to previously used methods based on optical flashers and drill logging data. The longer attenuation length of sound compared to light makes the acoustic module a promising candidate for IceCube-Gen2, which may have optical sensors on strings with twice the current spacing. We present an overview of the technical design and tests of the system as well as analytical methods for determining the propagation times of the acoustic signals.

Primordial black holes (PBHs), hypothesized to be the result of density fluctuations during the early universe, are candidates for dark matter. When microlensing background stars, they cause a transient apparent enhancement of the flux. Measuring these signals with optical telescopes is a powerful method to constrain the PBH abundance in the range of $10^{-10}\,M_{\odot}$ to $10^{1}\,M_{\odot}$. Especially for galactic stars, the finiteness of the sources needs to be taken into account. For low PBH masses (in this work $\lesssim 10^{-8}\,M_{\odot}$) the average duration of the detectable event decreases with the mass $\langle t_e\rangle \propto M_{\mathrm{PBH}}$. For $M_{\mathrm{PBH}}\approx 10^{-11}\,M_{\odot}$ we find $\langle t_e\rangle \lesssim\,1 \mathrm{s}$. For this reason, fast sampling detectors may be required as they could enable the detection of low mass PBHs. Current limits are set with sampling speeds of 2 minutes to 24 hours in the optical regime. Ground-based Imaging Atmospheric Cherenkov telescopes (IACTs) are optimized to detect the $\sim$ns long optical Cherenkov signals induced by atmospheric air showers. As shown recently, the very-large mirror area of these instruments provides very high signal to noise ratio for fast optical transients ($\ll 1\,$s) such as asteroid occultations. We investigate whether optical observations by IACTs can contribute to extending microlensing limits to the unconstrained mass range $M_{\mathrm{PBH}}<10^{-10}M_\odot$. We discuss the limiting factors to perform these searches for each telescope type. We calculate the rate of expected detectable microlensing events in the relevant mass range for the current and next-generation IACTs considering realistic source parameters.

We study the effect of supergravity corrections due to a linear and a bilinear term in the K\"ahler potential, in the context of a supersymmetric hybrid inflation model. By appropriate choice of the parameters associated to these terms, we are able to satisfy the main cosmological constraints for the spectral index $n_s$ and the tensor-to-scalar ratio $r$. In addition, this model predicts primordial black hole abundance enough to account for the whole dark matter of the Universe and gravitational wave spectra within the reach of future detection experiments. The predictions of the model can be made compatible to the NANOGrav reported signal, at the cost of significantly lower primordial black hole abundance.

Understanding the origins of small-scale flats of CCDs and their wavelength-dependent variations plays an important role in high-precision photometric, astrometric, and shape measurements of astronomical objects. Based on the unique flat data of 47 narrow-band filters provided by JPAS-{\it Pathfinder}, we analyze the variations of small-scale flats as a function of wavelength. We find moderate variations (from about $1.0\%$ at 390 nm to $0.3\%$ at 890 nm) of small-scale flats among different filters, increasing towards shorter wavelengths. Small-scale flats of two filters close in central wavelengths are strongly correlated. We then use a simple physical model to reproduce the observed variations to a precision of about $\pm 0.14\%$, by considering the variations of charge collection efficiencies, effective areas and thicknesses between CCD pixels. We find that the wavelength-dependent variations of small-scale flats of the JPAS-{\it Pathfinder} camera originate from inhomogeneities of the quantum efficiency (particularly charge collection efficiency) as well as the effective area and thickness of CCD pixels. The former dominates the variations in short wavelengths while the latter two dominate at longer wavelengths. The effects on proper flat-fielding as well as on photometric/flux calibrations for photometric/slit-less spectroscopic surveys are discussed, particularly in blue filters/wavelengths. We also find that different model parameters are sensitive to flats of different wavelengths, depending on the relations between the electron absorption depth, the photon absorption length and the CCD thickness. In order to model the wavelength-dependent variations of small-scale flats, a small number (around ten) of small-scale flats with well-selected wavelengths are sufficient to reconstruct small-scale flats in other wavelengths.

Separately, neither electromagnetic (EM) observations nor gravitational wave (GW) observations can distinguish between the $f(T)$ model and the $\Lambda$CDM model effectively. To break this degeneration, we simulate the GW measurement based on the coming observation facilities, explicitly the Einstein Telescope. We make cross-validations between the simulated GW data and factual EM data, including the Pantheon, H(z), BAO and CMBR data, and the results show that they are consistent with each other. Anyway, the EM data itself have the $H_0$ tension problem which plays critical role in the distinguishable problem as we will see. Our results show that the GW$+$BAO$+$CMBR data could distinguish the $f(T)$ theory from the $\Lambda$CDM model in $2\sigma$ regime.

Energetic particles may have been important for the origin of life on Earth by driving the formation of prebiotic molecules. We calculate the intensity of energetic particles, in the form of stellar and Galactic cosmic rays, that reach Earth at the time when life is thought to have begun ($\sim$3.8Gyr ago), using a combined 1.5D stellar wind model and 1D cosmic ray model. We formulate the evolution of a stellar cosmic ray spectrum with stellar age, based on the Hillas criterion. We find that stellar cosmic ray fluxes are larger than Galactic cosmic ray fluxes up to $\sim$4 GeV cosmic ray energies $\sim$3.8Gyr ago. However, the effect of stellar cosmic rays may not be continuous. We apply our model to HR 2562b, a young warm Jupiter-like planet orbiting at 20au from its host star where the effect of Galactic cosmic rays may be observable in its atmosphere. Even at 20au, stellar cosmic rays dominate over Galactic cosmic rays.

Next-generation cosmological surveys will observe larger cosmic volumes than ever before, enabling us to access information on the primordial Universe, as well as on relativistic effects. In a companion paper, we applied a Fisher analysis to forecast the expected precision on $f_{\rm NL}$ and the detectability of the lensing magnification and Doppler contributions to the power spectrum. Here we assess the bias on the best-fit values of $f_{\rm NL}$ and other parameters, from neglecting these light-cone effects. We consider forthcoming 21cm intensity mapping surveys (SKAO) and optical galaxy surveys (DESI and Euclid), both individually and combined together. We conclude that lensing magnification at higher redshifts must be included in the modelling of spectroscopic surveys. If lensing is neglected in the analysis, this produces a bias of more than 1$\sigma$ - not only on $f_{\rm NL}$, but also on the standard cosmological parameters.

Context. The populations of small bodies of the Solar System (asteroids, comets, Kuiper-Belt objects) are used to constrain the origin and evolution of the Solar System. Both their orbital distribution and composition distribution are required to track the dynamical pathway from their regions of formation to their current locations. Aims. We aim at increasing the sample of Solar System objects that have multi-filter photometry and compositional taxonomy. Methods. We search for moving objects in the archive of the Sloan Digital Sky Survey. We attempt at maximizing the number of detections by using loose constraints on the extraction. We then apply a suite of filters to remove false-positive detections (stars or galaxies) and mark out spurious photometry and astrometry. Results. We release a catalog of 1 542 522 entries, consisting of 1 036 322 observations of 379 714 known and unique SSOs together with 506 200 observations of moving sources not linked with any known SSOs. The catalog completeness is estimated to be about 95% and the purity to be above 95% for known SSOs.

In this work we study the formation of the first two black hole-neutron star (BHNS) mergers detected in gravitational waves (GW200115 and GW200105) from massive stars in wide isolated binary systems - the isolated binary evolution channel. We use 560 BHNS binary population synthesis model realizations from Broekgaarden et al. (2021a) and show that the system properties (chirp mass, component masses and mass ratios) of both GW200115 and GW200105 match predictions from the isolated binary evolution channel. We also show that most model realizations can account for the local BHNS merger rate densities inferred by LIGO-Virgo. However, to simultaneously also match the inferred local merger rate densities for BHBH and NSNS systems we find we need models with moderate kick velocities ($\sigma\lesssim 10^2\,\rm{km}\,\rm{s}^{-1}$) or high common-envelope efficiencies ($\alpha_{\rm{CE}}\gtrsim 2$) within our model explorations. We conclude that the first two observed BHNS mergers can be explained from the isolated binary evolution channel for reasonable model realizations.

Compared to the diversity seen in exoplanets, Venus is a veritable astrophysical twin of the Earth, however its global cloud layer truncates features in transmission spectroscopy, masking its non-Earth-like nature. Observational indicators that can distinguish an exo-Venus from an exo-Earth must therefore survive above the cloud layer. The above-cloud atmosphere is dominated by photochemistry, which depends on the spectrum of the host star and therefore changes between stellar systems. We explore the systematic changes in photochemistry above the clouds of Venus-like exoplanets orbiting K-Dwarf or M-Dwarf host stars, using a recently validated model of the full Venus atmosphere (0-115 km) and stellar spectra from the MUSCLES Treasury survey. SO2, OCS and H2S are key gas species in Venus-like planets that are not present in Earth-like planets, and could therefore act as observational discriminants if their atmospheric abundances are high enough to be detected. We find that SO2, OCS and H2S all survive above the cloud layer when irradiated by the coolest K-Dwarf and all seven M-Dwarfs, whereas these species are heavily photochemically depleted above the clouds of Venus. The production of sulfuric acid molecules that form the cloud layer decreases for decreasing stellar effective temperature. Less steady-state photochemical oxygen and ozone forms with decreasing stellar effective temperature, and the effect of chlorine-catalysed reaction cycles diminish in favour of HOx and SOx catalysed cycles. We conclude that trace sulfur gases will be prime observational indicators of Venus-like exoplanets around M-Dwarf host stars, potentially capable of distinguishing an exo-Venus from an exo-Earth.

Previous researches on high-energy photon events from gamma-ray bursts~(GRBs) suggest a light speed variation $v(E)=c(1-E/E_{\mathrm{LV}})$ with $E_{\mathrm{LV}}=3.6\times10^{17}~\mathrm{ GeV}$, together with a pre-burst scenario that hight-energy photons come out about 10 seconds earlier than low-energy photons at the GRB source. However, in the Lorentz invariance violating scenario with an energy dependent light speed considered here, high-energy photons travel slower than low-energy photons due to the light speed variation, so that they are usually detected after low-energy photons in observed GRB data. Here we find four high-energy photon events which were observed earlier than low-energy photons from Fermi Gamma-ray Space Telescope~(FGST), and analysis on these photon events supports the pre-burst scenario of high energy photons from GRBs and the energy dependence of light speed listed above.

We explore how dense filament widths, when measured using different molecular species, may change as a consequence of gas accretion toward the filament. As a gas parcel falls into the filament, it will experience different density, temperature, and extinction values. The rate at which this environment changes will affect differently the abundance of different molecules. So, a molecule that forms quickly will better reflect the local physical conditions a gas parcel experiences than a slower-forming molecule. Since these differences depend on how the respective timescales compare, the different molecular distributions should reflect how rapidly the environment changes, i.e., the accretion rate toward the filament. We find that the filament widths measured from time-dependent abundances for C2H, CO, CN, CS, and C3H2, are sensitive the most to this effect, being those molecules the ones presenting also the wider filament widths. On the contrary, molecules such as N2H+, NH3, H2CO, HNC or CH3OH are not so sensitive to accretion and present the narrowest filament widths. We propose that ratios of filament widths for different tracers could be a useful tool to estimate the accretion rate onto the filament.

Kepler high cadence data are used to measure the orbital periods and to determine the orbital waveforms of five dwarf novae. A significant improvement of the period of V1504 Cyg is achieved, while for the other systems periods are derived which are compatible with previous determinations. The orbital waveforms of the short period systems V1504 Cyg, V344 Lyr and V516 Lyr are very nearly sinusoidal, while the longer period dwarf nova V447 Lyr appears almost to be a twin of U Gem. The unusual system KIC 9202990 exhibits distinct variations of its waveform as a function of brightness during its outburst cycle.

We investigate two topics regarding solar mass FGK-type stars, the lithium rotation connection (LRC) and the existence of the "lithium desert". We determine the minimum critical rotation velocity ($v \sin i$) related with the LRC separating slow from rapid stellar rotators, as being 5 km s$^{-1}$. This value also split different stellar properties. For the first time we explore the behaviour of the LRC for some stellar associations with ages between 45 Myr and 120 Myr. This allows us to study the LRC age dependence at the beginning of the general spin down stage for low mass stars, which starts at $\sim$ 30-40 Myr. We find that each stellar group presents a characteristic minimum lithium (Li) depletion connected to a specific large rotation velocity and that this minimum changes with age. For instance, this minimum changes from $\sim$ 50 km s$^{-1}$ to less than 20 km s$^{-1}$ in 200 Myr. Regarding the lithium desert, it was described as a limited region in the A(Li)-$T_{\rm eff}$ map containing no stars. Using $T_{\rm eff}$ from {\em Gaia} DR2 we detect 30 stars inside and/or near the same box defined originally as the Li desert. Due to their intrinsic $T_{\rm eff}$ errors some of these stars may be inside or outside the box, implying a large probability that the box contains several stars. Considering this last fact the "lithium desert" appears to be more a statistical distribution fluctuation than a real problem.

The Pierre Auger Observatory is the largest extensive air shower detector. Based on a hybrid system, this experiment measures the longitudinal shower development and the particles at the ground. This detection system allows the extraction of the p-air cross-section at energies much higher than the ones accessible by current colliders. It is also possible to test hadronic interaction models using correlations between different air shower observables, like the depth of shower maximum and the muon number at the ground and their fluctuations. Thanks to the low energy extension of the Pierre Auger Observatory, the muon deficit in air shower simulations can be addressed over almost three decades at the highest energies.

We analyze the galaxy pairs in a volume limited sample ($M_r \leq -21$) from the SDSS to study the effects of galaxy interactions on the star formation rate and colour of galaxies in different environments. We study the star formation rate and colour of the paired galaxies as a function of projected separation and compare the results with their control samples matched in stellar mass, redshift and local density. We find that the major interactions significantly enhance the star formation rate in paired galaxies and turn them bluer with decreasing pair separation within $30$ kpc. The impact of tidal interactions on star formation rate and colour are more significant in the heavier members of the major pairs. The star formation enhancement in major pairs is significantly higher at the low-density environments, where the influence can extend up to $\sim 100$ kpc. Contrarily, the major pairs at high-density environments show suppression in their star formation. Depending on the embedding environments, the major interactions in the intrinsically brighter galaxy pairs can thus enhance or quench star formation. We find that the minor pairs at both low-density and high-density environments are significantly less star-forming and redder than their control galaxies. It indicates that the minor interactions in intrinsically brighter galaxy pairs always suppress the star formation irrespective of their environment. The lighter members in these minor pairs show a greater susceptibility to suppressed star formation. Our results imply that both the major and minor interactions can contribute to the observed bimodality. We conclude that the galaxy evolution is determined by a complex interplay between the galaxy properties, galaxy interactions, and environment.

We examine an intriguing possibility that a single field is responsible for both inflation and dark matter, focussing on the minimal set--up where inflation is driven by a scalar coupling to curvature. We study in detail the reheating process in this framework, which amounts mainly to particle production in a quartic potential, and distinguish thermal and non--thermal dark matter options. In the non--thermal case, the reheating is impeded by backreaction and rescattering, making this possibility unrealistic. On the other hand, thermalized dark matter is viable, yet the unitarity bound forces the inflaton mass into a narrow window close to half the Higgs mass.

The currently released datasets of the observational surveys reveal the redshift dependence of the physical features of cosmic voids. We study the void induced hyperbolicity, that is the deviation of the photon beams propagating the voids, taking into account the redshift dependence of the void size indicated by the observational surveys. The cumulative image distortion parameter is obtained for the case of a sequence of variable size voids and given underdensity parameters. The derived formulae applied along with those of redshift distortion ones, enable one to trace the number and the physical parameters of the line-of-sight voids from the analysis of the distortion in the galactic surveys.}

New optical sensors called the "D-Egg" have been developed for cost-effective instrumentation for the IceCube Upgrade. With two 8-inch high quantum efficient photomultiplier tubes (PMTs), they offer increased effective photocathode area while retaining as much of the successful IceCube Digital Optical Module design as possible. Mass production of D-Eggs has started in 2020. By the end of 2021, there will be 310 D-Eggs produced with 288 deployed in the IceCube Upgrade. The D-Egg readout system uses advanced technologies in electronics and computing power. Each of the two PMT signals is digitised using ultra-low-power 14-bit ADCs with a sampling frequency of 240 megaSPS, enabling seamless and lossless event recording from single-photon signals to signals exceeding 200 PE within 10 nanosecond, as well as flexible event triggering. In this paper, we report the single photon detection performance as well as the multiple photon recording capability of D-Eggs from the mass production line which have been evaluated with the built-in data acquisition system.

We develop topological criteria for the existence of electroweak magnetic monopoles and Z-strings and extend the Kibble mechanism to study their formation during the electroweak phase transition. The distribution of magnetic monopoles produces magnetic fields that have a spectrum $B_\lambda \propto \lambda^{-2}$ where $\lambda$ is a smearing length scale. Even as the magnetic monopoles annihilate due to the confining Z-strings, the magnetic field evolves with the turbulent plasma and may be relevant for cosmological observations.

Axions are hypothetical particles that may explain the observed dark matter (DM) density and the non-observation of a neutron electric dipole moment. An increasing number of axion laboratory searches are underway worldwide, but these efforts are made difficult by the fact that the axion mass is largely unconstrained. If the axion is generated after inflation there is a unique mass that gives rise to the observed DM abundance; due to nonlinearities and topological defects known as strings, computing this mass accurately has been a challenge for four decades. Recent works, making use of large static lattice simulations, have led to largely disparate predictions for the axion mass, spanning the range from 25 microelectronvolts to over 500 microelectronvolts. In this work we show that adaptive mesh refinement (AMR) simulations are better suited for axion cosmology than the previously-used static lattice simulations because only the string cores require high spatial resolution. Using dedicated AMR simulations we obtain an over three order of magnitude leap in dynamic range and provide evidence that axion strings radiate their energy with a scale-invariant spectrum, to within $\sim$5% precision, leading to a mass prediction in the range (40,180) microelectronvolts.

Thermal axion production in the early universe goes through several mass thresholds, and the resulting rate may change dramatically across them. Focusing on the KSVZ and DFSZ frameworks for the invisible QCD axion, we perform a systematic analysis of thermal production across thresholds and provide smooth results for the rate. The QCD phase transition is an obstacle for both classes of models. For the hadronic KSVZ axion, we also deal with production at temperatures around the mass of the heavy-colored fermion charged under the Peccei-Quinn symmetry. Within the DFSZ framework, standard model fermions are charged under this symmetry, and additional thresholds are the heavy Higgs bosons masses and the electroweak phase transition. We investigate the cosmological implications with a specific focus on axion dark radiation quantified by an effective number of neutrino species and explore the discovery reach of future CMB-S4 surveys.

Appearance of cosmic strings in the early Universe is a common manifestation of new physics typically linked to some high energy scale. In this paper, we discuss a different situation, where a model underlying cosmic string formation is approximately scale free. String tension is naturally related to the square of the temperature of the hot primordial plasma in such a setting, and hence decreases with (cosmic) time. With gravitational backreaction neglected, the dynamics of these melting strings in an expanding Universe is equivalent to the dynamics of constant tension strings in a Minkowski spacetime. We provide an estimate for the emission of gravitational waves from string loops. Contrary to the standard case, the resulting spectrum is markedly non-flat and has a characteristic falloff at frequencies below the peak one. The peak frequency is defined by the underlying model and lies in the range accessible by the future detectors for very weak couplings involved.

Long standing themes in inflation include the issue of large field vs. small field inflation as well as the question what fraction of phase space leads to sufficient inflation, and furthermore is compatible with the experimental data. In the present paper these issues are discussed in the context of modular inflation, a specialization of the framework of automorphic nonlinear $\sigma$-models associated to homogeneous spaces $G/K$ in which the continuous shift symmetry group $G$ is weakly broken to discrete subgroups $\Gamma$. The target spaces of these theories inherit a curved structure from the group $G$, which in the case of modular invariant inflation leads to a hyperbolic field space geometry. It is shown that in this class of models the symmetry structure leads to both large and small field inflationary trajectories within a single modular inflation model. The present paper analyzes the concrete model of $j$-inflation, a hyperbolic model with nontrivial inflaton interactions. It describes in some detail the structure of the initial conditions, including a systematic analysis of several phenomenological functions on the target space, leading to constraints on the curvature scalar of the field space by upcoming experiments, as well as a discussion of the scaling behavior of the spectral index, the finite volume fraction of the field space leading to sufficient inflation, the attractor behavior of $j$-inflation, and a comparison of inflaton trajectories vs. target space geodesics. The tensor-ratio analysis shows that $j$-inflation is an interesting target for upcoming ground and satellite experiments.

Space plasma simulations have seen an increase in the use of magnetohydrodynamic (MHD) with embedded Particle-in-Cell (PIC) models. This combined MHD-EPIC algorithm simulates some regions of interest using the kinetic PIC method while employing the MHD description in the rest of the domain. The MHD models are highly efficient and their fluid descriptions are valid for most part of the computational domain, thus making large-scale global simulations feasible. However, in practical applications, the regions where the kinetic effects are critical can be changing, appearing, disappearing and moving in the computational domain. If a static PIC region is used, this requires a much larger PIC domain than actually needed, which can increase the computational cost dramatically. To address the problem, we have developed a new method that is able to dynamically change the region of the computational domain where a PIC model is applied. We have implemented this new MHD with Adaptively Embedded PIC (MHD-AEPIC) algorithm using the BATS-R-US Hall MHD and the Adaptive Mesh Particle Simulator (AMPS) as the semi-implicit PIC models. We describe the algorithm and present a test case of two merging flux ropes to demonstrate its accuracy. The implementation uses dynamic allocation/deallocation of memory and load balancing for efficient parallel execution. We evaluate the performance of MHD-AEPIC compared to MHD-EPIC and the scaling properties of the model to large number of computational cores.

In this contribution we review the dynamics of hyperons with nucleons and nuclear matter, paying a special attention to hypernuclei. We also discuss the presence of hyperons in the inner core of neutron stars and the consequences for the structure of these compact stars.

Electromagnetic metamaterials at microwave frequencies are well established in industry and research. Recent work has shown how a specific kind of metallic metamaterial can contribute towards improving the performance of the feedhorn antennas used in radio astronomy and satellite telecommunications. In this article, we justify this argument, finding an innovative type of meta-ring of remarkable manufacturability with a potential to improve the state of the art in these fields. A pioneering meta-horn antenna formed of meta-rings is then fabricated and characterized in the laboratory, showing an excellent feature on an octave bandwidth, especially in terms of cross-polarization, a key figure of merit in both radio astronomy and telecommunications; and also side-lobe level, return-loss and gain.

Brain organoids recapitulate a number of brain properties, including neuronal diversity. However, do they recapitulate brain shape? Using a hydrodynamic description for cell nuclei as particles interacting via an attractive field generated by the surrounding active cell cytoskeleton, we quantify shape development in brain organoids. Regions of cell nuclei overdensity in the linear regime drive the initial seeding for cortex-core structures, which emerge in the non-linear regime with elongated cell nuclei and thus, cell shape, in the cortex. We then use an extended version of the buckling without bending morphogenesis model to predict foliations/folds of the cortex in the presence of a nonlinearity due to elongated cells actively regulating strain. In addition to laying new groundwork for the design of more familiar and less familiar brain shapes, our work provides an intriguing quantitative connection with large-scale structure formation in the universe.