Papers for Wednesday, Apr 20 2022

Using numerical simulations, we have studied the escape of globular clusters (GCs) from the satellite dwarf spheroidal galaxies (dSphs) of the Milky Way (MW). We start by following the orbits of a large sample of GCs around dSphs in the presence of the MW potential field. We then obtain the fraction of GCs leaving their host dSphs within a Hubble Time. We model dSphs by a Hernquist density profile with masses between $10^7\,\mathrm{M}_{\odot}$ and $7\times 10^9\,\mathrm{M}_{\odot}$. All dSphs lie on the Galactic disc plane, but they have different orbital eccentricities and apogalactic distances. We compute the escape fraction of GCs from 13 of the most massive dSphs of the MW, using their realistic orbits around the MW (as determined by Gaia). The escape fraction of GCs from 13 dSphs is in the range $12\%$ to $93\%$. The average escape time of GCs from these dSphs was less than 8 $\,\mathrm{Gyrs}$, indicating that the escape process of GCs from dSphs was over. We then adopt a set of observationally-constrained density profiles for specific case of the Fornax dSph. According to our results, the escape fraction of GCs shows a negative correlation with both the mass and the apogalactic distance of the dSphs, as well as a positive correlation with the orbital eccentricity of dSphs. In particular, we find that the escape fraction of GCs from the Fornax dSph is between $13\%$ and $38\%$. Finally, we observe that when GCs leave their host dSphs, their final orbit around the MW does not differ much from their host dSphs.

We study the newly released light curve from the fireball of the first interstellar meteor CNEOS 2014-01-08. The measured velocity and three observed flares down to an altitude of $18.7 \mathrm{\; km}$ imply ambient ram pressure in the range of $113-194$ MPa when the meteor disintegrated. The required yield strength is $\gtrsim 20$ times higher than stony meteorites and $\gtrsim 2$ times larger than iron meteorites. The implied slowdown in the atmosphere suggests an initial speed of about $66.5 \; {\rm km~s^{-1}}$, strengthening the case for an interstellar origin of this meteor and making it an outlier relative to the velocity dispersion of local stars.

We aim to quantify the relation between the dust-to-gas (DTG) mass ratio and gas-phase metallicity of $z=$2.1-2.5 luminous galaxies and contrast this high-redshift relation against analogous constraints at $z=$0. We present a sample of 10 star-forming main-sequence galaxies in the redshift range $2.1<z<2.5$ with rest-optical emission-line information available from the MOSDEF survey and with ALMA 1.2 millimeter and CO J$=$3--2 follow-up observations. The galaxies have stellar masses ranging from $10^{10.3}$ to $10^{10.6}\,\rm{M}_\odot$ and cover a range in star-formation rate from 35 to 145 $\rm{M}_\odot\,\rm{yr}^{-1}$. We calculate the gas-phase oxygen abundance of these galaxies from rest-optical nebular emission lines (8.4 < $12 + \log{(\rm{O/H})} < 8.8$, corresponding to 0.5-1.25 Z$_\odot$). We estimate the dust and H2 masses (using a metallicity dependent CO-to-H2 conversion factor) of the galaxies from the 1.2 mm and CO J$=$3-2 observations, respectively, from which we estimate a DTG. We find that the galaxies in this sample follow the earlier observed trends between CO line luminosity and dust-continuum luminosity from $z=0$ to $z=3$, extending such trends to fainter galaxies at $2.1<z<2.5$ than observed to date. We find no second-order metallicity dependence in the CO - dust-continuum luminosity relation for the galaxies presented in this work. The DTG of main-sequence galaxies at $2.1<z<2.5$ are consistent with an increase in DTG with gas-phase metallicity. Galaxies at $z=$2.1-2.5 are furthermore consistent with the DTG-metallicity relation found at $z=$0, providing relevant constraints for galaxy formation models. These results furthermore imply that the metallicity of galaxies should be taken into account when estimating cold-gas masses from dust-continuum emission, especially relevant when studying metal-poor low-mass or high-redshift galaxies. [abridged]

We initiate the exploration of the cosmology of dark fifth forces: new forces acting solely on Dark Matter. We focus on long range interactions which lead to an effective violation of the Equivalence Principle on cosmological scales. At the microscopic level, the dark fifth force can be realized by a light scalar with mass smaller than the Hubble constant today ($\lesssim 10^{-33}\,\text{eV}$) coupled to Dark Matter. We study the behavior of the background cosmology and linear perturbations in such a Universe. At the background level, the new force modifies the evolution of the Dark Matter energy density and thus the Hubble flow. At linear order, it modifies the growth of matter perturbations and generates relative density and velocity perturbations between Dark Matter and baryons that grow over time. We derive constraints from current CMB and BAO data, bounding the strength of the dark fifth force to be less than a percent of gravity. These are the strongest constraints to date. We present potential implications of this scenario for the Hubble tension and discuss how our results are modified if the light scalar mediator accounts for the observed density of the Dark Energy. Finally, we comment on the interplay between our constraints and searches for violations of the Equivalence Principle in the visible sector.

Most current models of low mass red giant stars do not reproduce the observed position of the red giant branch luminosity bump, a diagnostic of the maximum extent of the convective envelope during the first dredge up. Global asteroseismic parameters, the large frequency separation and frequency of maximum oscillation power, measured for large samples of red giants, show that modeling convective overshoot below the convective envelope helps match the modeled luminosity bump positions to observations. However, these global parameters cannot be used to probe envelope overshoot in a star-by-star manner. Red giant mixed modes, which behave like acoustic modes at the surface and like gravity modes in the core, contain important information about the interior structure of the star, especially near the convective boundary. Therefore, these modes may be used to probe interior processes, such as overshoot. Using a grid of red giant models with varying mass, metallicity, surface gravity, overshoot treatment, and amount of envelope overshoot, we find that changing the overshoot amplitude (and prescription) of overshoot below the convection zone in red giant stellar models results in significant differences in the evolution of the models' dipole mixed-mode oscillation frequencies, the average mixed mode period spacing, $\langle \Delta P \rangle$, and gravity mode phase offset term, $\epsilon_g$.

Stripped-envelope core-collapse supernovae can be divided into two broad classes: the common Type Ib/c supernovae (SNe Ib/c), powered by the radioactive decay of $^{56}$Ni, and the rare superluminous supernovae (SLSNe), most likely powered by the spin-down of a magnetar central engine. Up to now, the intermediate regime between these two populations has remained mostly unexplored. Here, we present a comprehensive study of 40 \textit{luminous supernovae} (LSNe), SNe with peak magnitudes of $M_r = -19$ to $-20$ mag, bound by SLSNe on the bright end and by SNe Ib/c on the dim end. Spectroscopically, LSNe appear to form a continuum between Type Ic SNe and SLSNe. Given their intermediate nature, we model the light curves of all LSNe using a combined magnetar plus radioactive decay model and find that they are indeed intermediate, not only in terms of their peak luminosity and spectra, but also in their rise times, power sources, and physical parameters. We sub-classify LSNe into distinct groups that are either as fast-evolving as SNe Ib/c or as slow-evolving as SLSNe, and appear to be either radioactively or magnetar powered, respectively. Our findings indicate that LSNe are powered by either an over-abundant production of $^{56}$Ni or by weak magnetar engines, and may serve as the missing link between the two populations.

Observations show an almost ubiquitous presence of extra mixing in low-mass upper giant branch stars. The most commonly invoked explanation for this is the thermohaline instability. One dimensional stellar evolution models include prescriptions for thermohaline mixing, but our ability to make direct comparisons between models and observations has thus far been limited. Here, we propose a new framework to facilitate direct comparison: Using carbon to nitrogen measurements from the SDSS-IV APOGEE survey as a probe of mixing and a fluid parameter known as the reduced density ratio from one dimensional stellar evolution programs, we compare the observed amount of extra mixing on the upper giant branch to predicted trends from three-dimensional fluid dynamics simulations. By applying this method, we are able to place empirical constraints on the efficiency of mixing across a range of masses and metallicities. We find that the observed amount of extra mixing is strongly correlated with the reduced density ratio and that trends between reduced density ratio and fundamental stellar parameters are robust across choices for modeling prescription. We show that stars with available mixing data tend to have relatively low density ratios, which should inform the regimes selected for future simulation efforts. Finally, we show that there is increased mixing at low values of the reduced density ratio, which is consistent with current hydrodynamical models of the thermohaline instability. The introduction of this framework sets a new standard for theoretical modeling efforts, as validation for not only the amount of extra mixing, but trends between the degree of extra mixing and fundamental stellar parameters is now possible.

While unobscured and radio-quiet active galactic nuclei are regularly being found at redshifts $z > 6$, their obscured and radio-loud counterparts remain elusive. We build upon our successful pilot study, presenting a new sample of low-frequency-selected candidate high-redshift radio galaxies (HzRGs) over a sky area twenty times larger. We have refined our selection technique, in which we select sources with curved radio spectra between 72-231 MHz from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. In combination with the requirements that our GLEAM-selected HzRG candidates have compact radio morphologies and be undetected in near-infrared $K_{\rm s}$-band imaging from the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, we find 51 new candidate HzRGs over a sky area of approximately 1200 deg$^2$. Our sample also includes two sources from the pilot study: the second-most distant radio galaxy currently known, at $z=5.55$, with another source potentially at $z \sim 8$. We present our refined selection technique and analyse the properties of the sample. We model the broadband radio spectra between 74 MHz and 9 GHz by supplementing the GLEAM data with both publicly available data and new observations from the Australia Telescope Compact Array at 5.5 and 9 GHz. In addition, deep $K_{\rm s}$-band imaging from the High-Acuity Widefield $K$-band Imager (HAWK-I) on the Very Large Telescope and from the Southern Herschel Astrophysical Terahertz Large Area Survey Regions $K_{\rm s}$-band Survey (SHARKS) is presented for five sources. We discuss the prospects of finding very distant radio galaxies in our sample, potentially within the epoch of reionisation at $z \gtrsim 6.5$.

A-stars are the progenitors of about half of the white dwarfs (WDs) that currently exist. The connection between the multiplicity of A-stars and that of WDs is not known and both multiplicities are still poorly explored. We are in the process of obtaining tight constraints on a sample of 108 southern A-type stars that are part of the nearby VAST sample \citep{DeRosa14} by conducting near-infrared interferometric follow-up observations to the (twenty) stars among them which have large $Gaia$-$Hipparcos$ accelerations. In this paper, we combine spectroscopy, adaptive optics imaging, NIR interferometry and $Gaia$-$Hipparcos$ astrometry in order to disentangle the stars in the complicated HIP 87813 = HJ2814A system. We show that (i) a previously discovered faint star that is separated by 2" from the A star is actually a background source; (ii) the $Gaia$-$Hipparcos$ acceleration is caused by a newly discovered $0.74 M_{\odot}$ star that was missed in previous AO images and we solve for its $P \approx 60 \text{ yrs}$ astrometric orbit; (iii) by combining previously obtained spectra we show that the A star has a very close $0.85 M_{\odot}$ companion on a 13.4-day period orbit. The radial velocity curve combined with NIR interferometry constrains its orbit allowing Kozai-Lidov oscillations in the hierarchical triple to be ruled out. The system HJ2814 is one of only about fifteen known 5+ systems with an A star primary, and will result in a system of between two to five bound WDs within around a Hubble time.

Type III radio bursts are the result of plasma emission from mildly relativistic electron beams propagating from the low solar corona into the heliosphere where they can eventually be detected in situ if they align with the location of a heliospheric spacecraft. Here we observe a type III radio burst from 0.1-16 MHz using the Parker Solar Probe (PSP) FIELDS Radio Frequency Spectrometer (RFS), and from 10-80 MHz using the Low Frequency Array (LOFAR). This event was not associated with any detectable flare activity but was part of an ongoing noise storm that occurred during PSP encounter 2. A deprojection of the LOFAR radio sources into 3D space shows that the type III radio burst sources were located on open magnetic field from 1.6-3 $R_\odot$ and originated from a specific active region near the East limb. Combining PSP/RFS observations with WIND/WAVES and Solar Terrestrial Relations Observatory (STEREO)/WAVES, we reconstruct the type III radio source trajectory in the heliosphere interior to PSP's position, assuming ecliptic confinement. An energetic electron enhancement is subsequently detected in situ at the STEREO-A spacecraft at compatible times although the onset and duration suggests the individual burst contributes a subset of the enhancement. This work shows relatively small-scale flux emergence in the corona can cause the injection of electron beams from the low corona into the heliosphere, without needing a strong solar flare. The complementary nature of combined ground and space-based radio observations, especially in the era of PSP, is also clearly highlighted by this study.

Born-again planetary nebulae (PNe) are extremely rare cases in the evolution of solar-like stars. It is commonly accepted that their central stars (CSPN) experienced a very late thermal pulse (VLTP), ejecting H-deficient material inside the evolved H-rich PN. Given the short duration of this event and the fast subsequent evolution of the CSPN, details of the mass ejection are unknown. We present the first morpho-kinematic model of the H-deficient material surrounding a born-again PN, namely A30. New San Pedro M\'{a}rtir observations with the Manchester Echelle Spectrograph were recently obtained to map its inner regions of A30 which are interpreted by means of the software SHAPE in conjunction with HST WFC3 images. The SHAPE morpho-kinematic model that best reproduces the observations is composed by a disrupted disk tilted 37$^\circ$ with respect to the line of sight and a pair of orthogonal opposite bipolar ejections. We confirm previous suggestions that the structures closer to the CSPN present the highest expansion velocities, that is, the disrupted disk expands faster than the farther bipolar features. We propose that the current physical structure and abundance discrepancy of the H-deficient clumps around the CSPN of A30 can be explained by a common envelope (CE) phase following the VLTP event. Our proposed scenario is also compared with other known born-again PNe (A58, A78, HuBi1 and the Sakurai's Object).

Context: The size of the constituent particles (monomers) of dust aggregates is one of the most uncertain parameters directly affecting collisional growth of aggregates in planet-forming disks. Despite its importance, the monomer size has not yet been meaningfully constrained by disk observations. Aims: We attempt to derive the monomer size from optical and near-infrared (IR) polarimetric observations of planet-forming disks. Methods: We perform a comprehensive parameter survey on the degree of linear polarization of light scattered by dust aggregates, using an exact numerical method called the $T$-matrix method. We investigate the effect of the monomer size, aggregate size, porosity, and composition on the degree of polarization. The obtained results are then compared with observed polarization fractions of several planet-forming disks at optical and near-IR wavelengths. Results: It is shown that the degree of polarization of aggregates depends sensitively on the monomer size unless the monomer size parameter is smaller than one or two. Comparing the simulation results with the disk observations, we find that the monomer radius is no greater than $0.4~\mu$m. The inferred monomer size is therefore similar to subunit sizes of the solar system dust aggregates and the maximum size of interstellar grains. Conclusions: Optical and near-IR quantitative polarimetry will provide observational grounds on the initial conditions for dust coagulation and thereby planetesimal formation in planet-forming disks.

Galaxies hosting Active Galactic Nuclei (AGN) with bent radio jets are used as tracers of dense environments, such as galaxy groups and clusters. The assumption behind using these jets is that they are bent under ram pressure from a dense, gaseous medium through which the host galaxy moves. However, there are many AGN in groups and clusters with jets that are not bent, which leads us to ask: why are some AGN jets affected so much by their environment while others are seemingly not? We present the results of an environmental study on a sample of 185 AGN with bent jets and 191 AGN with unbent jets in which we characterize their environments by searching for neighboring galaxies using a Friends-of-Friends algorithm. We find that AGN with bent jets are indeed more likely to reside in groups and clusters, while unbent AGN are more likely to exist in singles or pairs. When considering only AGN in groups of 3 or more galaxies, we find that bent AGN are more likely to exist in halos with more galaxies than unbent AGN. We also find that unbent AGN are more likely than bent AGN to be the brightest group galaxy. Additionally, groups hosting AGN with bent jets have a higher density of galaxies than groups hosting unbent AGN. Curiously, there is a population of AGN with bent jets that are in seemingly less dense regions of space, indicating they may be embedded in a cosmic web filament. Overall, our results indicate that bent doubles are more likely to exist in in larger, denser, and less relaxed environments than unbent doubles, potentially linking a galaxy's radio morphology to its environment.

The most common form of magnetar activity is short X-ray bursts, with durations from milliseconds to seconds, and luminosities ranging from $10^{36}$ to $10^{43}\ {\rm erg}\,{\rm s}^{-1}$. Recently, an X-ray burst from the galactic magnetar SGR 1935+2154 was detected to be coincident with two fast radio burst (FRB) like events from the same source, providing evidence that FRBs may be linked to magnetar bursts. Using fully 3D force-free electrodynamics simulations, we show that such magnetar bursts may be produced by Alfv\'{e}n waves launched from localized magnetar quakes: a wave packet propagates to the outer magnetosphere, becomes nonlinear, and escapes the magnetosphere, forming an ultra-relativistic ejecta. The ejecta pushes open the magnetospheric field lines, creating current sheets behind it. Magnetic reconnection can happen at these current sheets, leading to plasma energization and X-ray emission. The angular size of the ejecta can be compact, $\lesssim 0.5$ sr if the quake launching region is small, $\lesssim 5\times 10^{-3}$ sr at the stellar surface. We discuss implications for the FRBs and the coincident X-ray burst from SGR 1935+2154.

Growing evidence from multiwavelength observations of extragalactic supernovae (SNe) has established the presence of dense circumstellar material in Type II SNe. Interaction between the SN ejecta and the circumstellar material should lead to the acceleration of cosmic rays and associated high-energy emission. Observation of high-energy neutrinos along with the MeV neutrinos from SNe will provide unprecedented opportunities to understand unanswered questions in cosmic-ray and neutrino physics. We show that current and future neutrino detectors can identify high-energy neutrinos from an extragalactic SN in the neighborhood of the Milky Way. We present the prospects for detecting high-energy neutrino minibursts from SNe in known local galaxies, and demonstrate how the future high-energy neutrino network will extend the edge for identification of SN neutrinos.

In this chapter, we focus on the long-term evolution of the atmosphere of Venus, and how it has been affected by interior/exterior cycles. The formation and evolution of Venus's atmosphere, leading to the present-day surface conditions, remain hotly debated and involve questions that tie into many disciplines. Here, we explore the mechanisms that shaped the evolution of the atmosphere, starting with the volatile sources and sinks. Going from the deep interior to the top of the atmosphere, we describe fundamental processes such as volcanic outgassing, surface-atmosphere interactions, and atmosphere escape. Furthermore, we address more complex aspects of the history of Venus, including the role of meteoritic impacts, how magnetic field generation is tied into long-term evolution, and the implications of feedback cycles for atmospheric evolution. Finally, we highlight three plausible end-member evolutionary pathways that Venus might have followed, from the accretion to its present-day state, based on current modeling and observations. In a first scenario, the planet was desiccated early-on, during the magma ocean phase, by atmospheric escape. In a second scenario, Venus could have harbored surface liquid water for long periods of time, until its temperate climate was destabilized and it entered a runaway greenhouse phase. In a third scenario, Venus's inefficient outgassing could have kept water inside the planet, where hydrogen was trapped in the core and the mantle was oxidized. We discuss existing evidence and future observations/missions needed to refine our understanding of the planet's history and of the complex feedback cycles between the interior, surface, and atmosphere that operate in the past, present or future of Venus.

Many modeling of the Sagittarius (Sgr) stream have been attempted, but they still have difficulties to reproduce its full 6D space-phase properties. Using N-body simulation with a Milky Way mass of 5.2$\times10^{11}$ M$_{\odot}$ and a Sgr mass of 9.3$\times10^{8}$ M$_{\odot}$, we have been able to reproduce well all 3D spatial features of Sgr stream, including its core, leading and trailing arms, and their associated bifurcations. Moreover, all reported 3D kinematics properties of the Sgr stream have been qualitatively reproduced without the need for a massive LMC, although the latter can not be ruled out from this work. Moreover, we also find that our model fails in reproducing the exact behaviors of the stream arms in the energy-angular momentum plane. It let us to suggest that significant further progress can be only achievable after introducing a major component in the Sgr progenitor, which is the gas that dominates all Irregular dwarf galaxies in the Sgr mass range.

Cosmic rays (CRs) are an important energy source in the circum-galactic medium (CGM) that impact the multi-phase gas structure and dynamics. We perform two-dimensional CR-magnetohydrodynamic simulations to investigate the role of CRs in accelerating multi-phase gas formed via thermal instability. We compare outflows driven by CRs to those driven by a hot wind with equivalent momentum. We find that CRs driven outflow produces lower density contrast between cold and hot gas due to non-thermal pressure support, and yields a more filamentary cloud morphology. While entrainment in a hot wind can lead to cold gas increasing due to efficient cooling, CRs tend to suppress cold gas growth. The mechanism of this suppression depends on magnetic field strength, with CRs either reducing cooling or shredding the clouds by differential acceleration. Despite the suppression of cold gas growth, CRs are able to launch the cold clouds to observed velocities without rapid destruction. The dynamical interaction between CRs ad multi-phase gas is also sensitive to the magnetic field strength. In relatively strong fields, the CRs are more important for direct momentum input to cold gas. In relatively weak fields, the CRs impact gas primarily by heating, which modifies gas pressure.

Neutron stars are the densest objects known in our visible universe. Properties of matter inside a neutron star are encoded in its equation of state, which has wide-ranging uncertainty from a theoretical perspective. With the current understanding of quantum chromodynamics, it is hard to determine the interactions of neutron star matter at such high densities. Also performing many body calculations is computationally intractable. Besides the constitution of the neutron star core is highly speculative -- it is not ruled out that it contains exotic matter like strange baryons, meson condensates, quark matter, etc. Although the matter inside the neutron star is extremely dense, but the temperature of this object is very cold in most of its life span. We cannot produce such dense but rather cold material in our laboratory. Since probing the physics of neutron star matter is inaccessible by our earth based experiments, we look for astrophysical observations of neutron stars. This thesis deals with the theoretical and computational techniques required to translate neutron star observables from astrophysical observations to its equation of state.

The spiral structure of a spiral galaxy can be seen through different observational tracers such as the dust in the interstellar medium, the free electrons in ionized regions, the molecular gas, or the atomic hydrogen in H{\alpha} regions. In this work, we use an N-body simulation with Magnetohydrodynamics (MHD) to investigate the spiral pattern and the star formation activity in the gas component of a disk galaxy. Some of the questions that we tackle include: how are galaxies observed through the different properties of the gas? Does the spiral structure of the galaxy change when we trace it with the different properties of the gas? Do the spiral arms in the simulation change its shape and width depending on what property we are "looking" through? Can we somehow model the shape of the arms to measure their width consistently? Does this model apply to all the properties? To answer these questions, we developed a method for the identification and extraction of the spiral structure in a disk galaxy. Using the results of this procedure, we further investigate the features of the spiral pattern through the different properties of the gas, with special attention to the star formation activity and how it behaves along and across the spiral structure.

The compact mm-wavelength signaL in the central cavity of the PDS70 disc, revealed by deep ALMA observations, is aligned with unresolved Halpha emission, and is thought to stem from a circum-planetary disc (CPD) around PDS70c. We revisit the available ALMA data on PDS70c with alternative imaging strategies, and with special attention to uncertainties and to the impact of the so-called "JvM correction", which is thought to improve the dynamic range of restored images. We also propose a procedure for the alignment and joint imaging of multi-epoch visibility data. We find that the JvM correction exaggerates the peak signal-to-noise of the data, by up to a factor of 10. In the case of PDS70, we recover the detection of PDS70c from the July 2019 data, but only at 8sigma. However, its non-detection in Dec. 2017 suggests that PDS70c is variable by at least 42%+-13% over a 1.75yr time-span, so similar to models of the Halpha variability. We also pick up fine structure in the inner disc, such that its peak is offset by ~0.04'' from the disc centre. The inner disc is variable too, which we tentatively ascribe to Keplerian rotation as well as intrinsic morphological changes.

Surface modification on Jupiter's volcanically active moon, Io, has to date been attributed almost exclusively to lava emplacement and volcanic plume deposits. Here we demonstrate that wind-blown transport of sediment may also be altering the Ionian surface. Specifically, shallow subsurface interactions between lava and Io's widespread sulfur dioxide (SO$_2$) frost can produce localized sublimation vapor flows with sufficient gas densities to enable particle saltation. We calculate anticipated outgassing velocities from lava-SO$_2$ frost interactions, and compare these to the saltation thresholds predicted when accounting for the tenuous nature of the sublimated vapor. We find that saltation may occur if frost temperatures surpass 155 K. Finally we make the first measurements of the dimensions of linear features in images from the Galileo probe, previously termed "ridges", which demonstrate certain similarities to dunes on other planetary bodies. Io joins a growing list of bodies with tenuous and transient atmospheres where aeolian sediment transport may be an important control on the landscape.

The simplistic but ubiquitous Mixing Length Theory (MLT) formalism is used to model convective energy transport within 1D stellar evolution calculations. The formalism relies on the free parameter $\alpha_{\rm MLT}$, which must be independently calibrated within each stellar evolution program and for any given set of physical assumptions. We present a solar calibration of $\alpha_{\text{MLT}}$ appropriate for use with the AESOPUS opacities, which have recently been made available for use with the MESA stellar evolution software. We report a calibrated value of $\alpha_{\rm MLT}=1.931$ and demonstrate the impact of using an appropriately calibrated value in simulations of a $3 M_{\odot}$ asymptotic giant branch star.

We present an analysis of survey observations of the trailing L5 Jupiter Trojan swarm using the wide-field Hyper Suprime-Cam CCD camera on the 8.2 m Subaru Telescope. We detected 189 L5 Trojans from our survey that covered about 15 deg^2 of sky with a detection limit of m_r = 24.1 mag, and selected an unbiased sample consisting of 87 objects with absolute magnitude 14 < H_r < 17 corresponding to diameter 2 km < D < 10 km for analysis of size distribution. We fit their differential magnitude distribution to a single-slope power-law with an index \alpha = 0.37 +- 0.01, which corresponds to a cumulative size distribution with an index of b = 1.85 +- 0.05. Combining our results with data for known asteroids, we obtained the size distribution of L5 Jupiter Trojans over the entire size range for 9 < H_V < 17, and found that the size distributions of the L4 and L5 swarms agree well with each other for a wide range of sizes. This is consistent with the scenario that asteroids in the two swarms originated from the same primordial population. Based on the above results, the ratio of the total number of asteroids with D > 2 km in the two swarms is estimated to be N_L4/N_L5=1.40 +- 0.15, and the total number of L_5 Jupiter Trojans with D > 1 km is estimated to be 1.1 x 10^5 by extrapolating the obtained distribution.

The water snowline in circumstellar disks is a crucial component in planet formation, but direct observational constraints on its location remain sparse due to the difficulty of observing water in both young embedded and mature protoplanetary disks. Chemical imaging provides an alternative route to locate the snowline, and HCO$^+$ isotopologues have been shown to be good tracers in protostellar envelopes and Herbig disks. Here we present $\sim$0.5$^{\prime\prime}$ resolution ($\sim$35 au radius) Atacama Large Millimeter/submillimeter Array (ALMA) observations of HCO$^+$ $J=4-3$ and H$^{13}$CO$^+$ $J=3-2$ toward the young (Class 0/I) disk L1527 IRS. Using a source-specific physical model with the midplane snowline at 3.4 au and a small chemical network, we are able to reproduce the HCO$^+$ and H$^{13}$CO$^+$ emission, but for HCO$^+$ only when the cosmic ray ionization rate is lowered to $10^{-18}$ s$^{-1}$. Even though the observations are not sensitive to the expected HCO$^+$ abundance drop across the snowline, the reduction in HCO$^+$ above the snow surface and the global temperature structure allow us to constrain a snowline location between 1.8 and 4.1 au. Deep observations are required to eliminate the envelope contribution to the emission and to derive more stringent constraints on the snowline location. Locating the snowline in young disks directly with observations of H$_2$O isotopologues may therefore still be an alternative option. With a direct snowline measurement, HCO$^+$ will be able to provide constraints on the ionization rate.

We consider a simple system consisting of matter, radiation and vacuum components to model the impact of thermal inflation on the evolution of primordial perturbations. The vacuum energy magnifies the modes entering the horizon before its domination, making them potentially observable, and the resulting transfer function reflects the phase changes and energy contents. To determine the transfer function, we follow the curvature perturbation from well outside the horizon during radiation domination to well outside the horizon during vacuum domination and evaluate it on a constant radiation density hypersurface, as is appropriate for the case of thermal inflation. The shape of the transfer function is determined by the ratio of vacuum energy to radiation at matter-radiation equality, which we denote by $\upsilon$, and has two characteristic scales, $k_{\rm a}$ and $k_{\rm b}$, corresponding to the horizon sizes at matter radiation equality and the beginning of the inflation, respectively. If $\upsilon \ll 1$, the universe experiences radiation, matter and vacuum domination eras and the transfer function is flat for $k \ll k_{\rm b}$, oscillates with amplitude $1/5$ for $ k_{\rm b} \ll k \ll k_{\rm a}$ and oscillates with amplitude $1$ for $k \gg k_{\rm a}$. For $\upsilon \gg 1$, the matter domination era disappears, and the transfer function reduces to being flat for $k \ll k_{\rm b}$ and oscillating with amplitude $1$ for $k \gg k_{\rm b}$.

Gamma-ray bursts (GRBs), observed to redshift $z=9.4$, are potential probes of the largely unexplored $z\sim 2.7-9.4$ part of the early Universe. Thus, finding relevant relations among GRB physical properties is crucial. We find that the Platinum GRB data compilation, with 50 long GRBs (with relatively flat plateaus and no flares) in the redshift range $0.553 \leq z \leq 5.0$, and the LGRB95 data compilation, with 95 long GRBs in $0.297 \leq z \leq 9.4$, as well as the 145 GRB combination of the two, strongly favor the three-dimensional (3D) fundamental plane (Dainotti) correlation relation (between the peak prompt lumininosity, the luminosity at the end of the plateau emission, and its rest frame duration) over the two-dimensional one (between the luminosity at the end of the plateau emission and its duration). The 3D Dainotti correlations in the three data sets are standardizable. We find that while LGRB95 data have $\sim50$\% larger intrinsic scatter parameter values than the better-quality Platinum data, they provide somewhat tighter constraints on cosmological-model and GRB-correlation parameters, perhaps solely due to the larger number of data points, 95 versus 50. This suggests that when compiling GRB data for the purpose of constraining cosmological parameters, given the quality of current GRB data, intrinsic scatter parameter reduction must be balanced against reduced sample size.

A wide-field zenith-looking telescope operating in a mode similar to Time-Delay-Integration (TDI) or drift scan imaging can perform an infrared sky survey without active pointing control but it requires a high-speed, low-noise infrared detector. Operating from a hosted payload platform on the International Space Station (ISS), the Emu space telescope employs the paradigm-changing properties of the Leonardo SAPHIRA electron avalanche photodiode array to provide powerful new observations of cool stars at the critical water absorption wavelength (1.4 {\mu}m) largely inaccessible to ground-based telescopes due to the Earth's own atmosphere. Cool stars, especially those of spectral-type M, are important probes across contemporary astrophysics, from the formation history of the Galaxy to the formation of rocky exoplanets. Main sequence M-dwarf stars are the most abundant stars in the Galaxy and evolved M-giant stars are some of the most distant stars that can be individually observed. The Emu sky survey will deliver critical stellar properties of these cool stars by inferring oxygen abundances via measurement of the water absorption band strength at 1.4 {\mu}m. Here we present the TDI-like imaging capability of Emu mission, its science objectives, instrument details and simulation results.

Hub-filament systems (HFSs) are potential sites of protocluster and massive star formation, and play a key role in mass accumulation. We report JCMT POL-2 850 $\mu$m polarization observations toward the massive HFS SDC13. We detect an organized magnetic field near the hub center with a cloud-scale "U-shape" morphology following the western edge of the hub. Together with larger-scale APEX 13CO and PLANCK polarization data, we find that SDC13 is located at the convergent point of three giant molecular clouds (GMCs) along a large-scale, partially spiral-like magnetic field. The smaller "U-shape" magnetic field is perpendicular to the large-scale magnetic field and the converging GMCs. We explain this as the result of a cloud-cloud collision. Within SDC13, we find that local gravity and velocity gradients point toward filament ridges and hub center. This suggests that gas can locally be pulled onto filaments and overall converges to the hub center. A virial analysis of the central hub shows that gravity dominates magnetic and kinematic energy. Combining large- and small-scale analyses, we propose that SDC13 is initially formed from a collision of clouds moving along the large-scale magnetic field. In the post-shock regions, after the initial turbulent energy has dissipated, gravity takes over and starts to drive the gas accretion along the filaments toward the hub center.

The evolution of galaxies is influenced by many physical processes which may vary depending on their environment. We combine Hubble Space Telescope (HST) and Multi-Unit Spectroscopic Explorer (MUSE) data of galaxies at 0.25<z<1.5 to probe the impact of environment on the size-mass relation, the Main Sequence (MS) and the Tully-Fisher relation (TFR). We perform a morpho-kinematic modelling of 593 [Oii] emitters in various environments in the COSMOS area from the MUSE-gAlaxy Groups In Cosmos (MAGIC) survey. The HST F814W images are modelled with a bulge-disk decomposition to estimate their bulge-disk ratio, effective radius and disk inclination. We use the [Oii]{\lambda}{\lambda}3727, 3729 doublet to extract the ionised gas kinematic maps from the MUSE cubes, and we model them for a sample of 146 [Oii] emitters, with bulge and disk components constrained from morphology and a dark matter halo. We find an offset of 0.03 dex on the size-mass relation zero point between the field and the large structure subsamples, with a richness threshold of N=10 to separate between small and large structures, and of 0.06 dex with N=20. Similarly, we find a 0.1 dex difference on the MS with N=10 and 0.15 dex with N=20. These results suggest that galaxies in massive structures are smaller by 14% and have star formation rates reduced by a factor of 1.3-1.5 with respect to field galaxies at z=0.7. Finally, we do not find any impact of the environment on the TFR, except when using N=20 with an offset of 0.04 dex. We discard the effect of quenching for the largest structures that would lead to an offset in the opposite direction. We find that, at z=0.7, if quenching impacts the mass budget of galaxies in structures, these galaxies would have been affected quite recently, for roughly 0.7-1.5 Gyr. This result holds when including the gas mass, but vanishes once we include the asymmetric drift correction.

Pair-instability supernovae are theorized supernovae that have not yet been observationally confirmed. They are predicted to exist in low-metallicity environments. Because overall metallicity becomes lower at higher redshifts, deep near-infrared transient surveys probing high-redshift supernovae are suitable to discover pair-instability supernovae. The Euclid satellite, which is planned to be launched in 2023, has a near-infrared wide-field instrument that is suitable for a high-redshift supernova survey. Although no dedicated supernova survey is currently planned during the Euclid's 6 year primary mission, the Euclid Deep Survey is planned to make regular observations of three Euclid Deep Fields (40 deg2 in total) spanning six years. While the observations of the Euclid Deep Fields are not frequent, we show that the predicted long duration of pair-instability supernovae would allow us to search for high-redshift pair-instability supernovae with the Euclid Deep Survey. Based on the current observational plan of the Euclid mission, we conduct survey simulations in order to estimate the expected numbers of pair-instability supernova discoveries. We find that up to several hundred pair-instability supernovae at z < ~ 3.5 can be discovered by the Euclid Deep Survey. We also show that pair-instability supernova candidates can be efficiently identified by their duration and color that can be determined with the current Euclid Deep Survey plan. We conclude that the Euclid mission can lead to the first confident discovery of pair-instability supernovae if their event rates are as high as those predicted by recent theoretical studies. We also update the expected numbers of superluminous supernova discoveries in the Euclid Deep Survey based on the latest observational plan.

We present the results from an Atacama Large Millimeter/Submillimeter Array (ALMA) 1.3 mm continuum and $^{12}$CO ($J=2-1$) line survey spread over 10 square degrees in the Serpens star-forming region of 320 young stellar objects, 302 of which are likely members of Serpens (16 Class I, 35 Flat spectrum, 235 Class II, and 16 Class III). From the continuum data, we derive disk dust masses and show that they systematically decline from Class I to Flat spectrum to Class II sources. Grouped by stellar evolutionary state, the disk mass distributions are similar to other young ($<3$ Myr) regions, indicating that the large scale environment of a star-forming region does not strongly affect its overall disk dust mass properties. These comparisons between populations reinforce previous conclusions that disks in the Ophiuchus star-forming region have anomalously low masses at all evolutionary stages. Additionally, we find a single deeply embedded protostar that has not been documented elsewhere in the literature and, from the CO line data, 15 protostellar outflows which we catalog here.

Despite forecasts of upcoming detections, it remains unclear how feasible the full spectrum of applications of strongly-lensed gravitational-wave observations are. One application may be in the multi-messenger domain: localisation of strongly lensed black hole mergers inside their associated lens systems in gravitational-wave (GW) and electromagnetic (EM) bands. This is intriguing because combining the observations of electromagnetically detected lens systems (via optical or infrared imaging) with their associated strongly-lensed gravitational waves could yield a wide array of valuable, otherwise inaccessible information. One might, for instance, independently verify strong lensing candidates, localise black holes to sub-arcsecond precision, study the binary-galaxy connection, and more accurately test gravitational-wave polarisation and propagation. Thus, here we perform a comprehensive simulation of the projected capabilities of LIGO-Virgo-Kagra, combined with Euclid, to find strongly lensed gravitational-wave events and then pinpoint the location of the black-hole merger. We find that for 20-50% of the detected events, the lens is detectable with Euclid-like imaging. For a 1-5 deg^2 sky localisation, with Euclid-like images of host candidates, we expect to identify the EM-counterpart for 34.6-21.9% of lensed GWs when four events are detected. For three and two events, this drops to 29.8-14.9% and 16.4-6.6% respectively. A dedicated follow-up of detected lensed events with space-based instruments in the EM and continued upgrades in the current and planned GW detectors, as well as lensed sub-threshold search pipelines are likely crucial to the success of this program.

We describe the optimum telescope focal ratio for a two-element, three surface, telecentric image-transfer microlens-to-fiber coupled integral field unit within the constraints imposed by micro-optics fabrication and optical aberrations. We create a generalized analytical description of the micro-optics optical parameters from first principals. We find that the optical performance, including all aberrations, of a design constrained by an analytic model considering only spherical aberration and diffraction matches within +/-4% of a design optimized by ray-tracing software such as Zemax. The analytical model does not require any compromise on the available clear aperture; about 90% mechanical aperture of a hexagonal microlens is available for light collection. The optimum telescope f-ratio for a 200{\mu}m core fiber fed at f/3.5 is between f/7 and f/12. We find the optimum telescope focal ratio changes as a function of fiber core diameter and fiber input beam speed. A telescope focal ratio of f/8 would support the largest range of fiber diameters (100 to 500{\mu}m) and fiber injection speeds (between f/3 and f/5). The optimization of telescope and lenslet-coupled fibers is relevant for the design of high-efficiency dedicated survey telescopes, and for retro-fitting existing facilities via introducing focal macro-optics to match the instrument input requirements.

In astrophysics, the search for sources of the highest-energy cosmic rays continues. For further progress, not only ever better observatories but also ever more realistic numerical simulations are needed. We compare different approaches for numerical test simulations of UHECRs in the IGMF and show that all methods provide correct statistical propagation characteristics of the particles in means of their diffusive behaviour. Through convergence tests, we show that the necessary requirements for the methods differ and ultimately reveal significant differences in the required simulation time.

Black hole accretion discs can produce powerful outflowing plasma (disc winds), seen as blue-shifted absorption lines in stellar and supermassive systems. These winds in Quasars have an essential role in controlling galaxy formation across cosmic time, but there is no consensus on how these are physically launched. A single unique observation of a stellar-mass black hole GRO J1655-40 showed the high wind density estimated from an absorption line from the metastable level of Fe xxii and ruled out X-ray heating (thermal-radiative wind) for the low observed luminosity. This left magnetic driving as the only viable mechanism, motivating unified models of magnetic winds in both binaries and Quasars. Here we reanalyse these data using a photoionisation code that includes the contribution of radiative cascades and collisions in populating the metastable level. The effect of radiative cascades reduces the inferred wind density by orders of magnitude. The derived column is also optically thick, so the source is intrinsically more luminous than observed. We show that a thermal-radiative wind model calculated from a radiation hydrodynamic simulation matches well with the data. We revisit the previous magnetic wind solution and show that this is also optically thick. Hence, it requires a larger source luminosity, and it struggles to reproduce the overall ion population at the required density (both new and old). These results remove the requirement for a magnetic wind in these data and remove the basis of the self-similar unified magnetic wind models extrapolated to Quasar outflows.

In this work we examine the classification accuracy and robustness of a state-of-the-art semi-supervised learning (SSL) algorithm applied to the morphological classification of radio galaxies. We test if SSL with fewer labels can achieve test accuracies comparable to the supervised state-of-the-art and whether this holds when incorporating previously unseen data. We find that for the radio galaxy classification problem considered, SSL provides additional regularisation and outperforms the baseline test accuracy. However, in contrast to model performance metrics reported on computer science benchmarking data-sets, we find that improvement is limited to a narrow range of label volumes, with performance falling off rapidly at low label volumes. Additionally, we show that SSL does not improve model calibration, regardless of whether classification is improved. Moreover, we find that when different underlying catalogues drawn from the same radio survey are used to provide the labelled and unlabelled data-sets required for SSL, a significant drop in classification performance is observered, highlighting the difficulty of applying SSL techniques under dataset shift. We show that a class-imbalanced unlabelled data pool negatively affects performance through prior probability shift, which we suggest may explain this performance drop, and that using the Frechet Distance between labelled and unlabelled data-sets as a measure of data-set shift can provide a prediction of model performance, but that for typical radio galaxy data-sets with labelled sample volumes of O(1000), the sample variance associated with this technique is high and the technique is in general not sufficiently robust to replace a train-test cycle.

In 2020 the European Space Agency selected Ariel as the next mission to join the space fleet of observatories to study planets outside our Solar System. Ariel will be devoted to the characterisation of a thousand planetary atmospheres, for understanding what exoplanets are made of, how they formed and how they evolve. To achieve the last two goals all planets need to be studied within the context of their own host stars, which in turn have to be analysed with the same technique, in a uniform way. We present the spectro-photometric method we have developed to infer the atmospheric parameters of the known host stars in the Tier 1 of the Ariel Reference Sample. Our method is based on an iterative approach, which combines spectral analysis, the determination of the surface gravity from {\em Gaia} data, and the determination of stellar masses from isochrone fitting. We validated our approach with the analysis of a control sample, composed by members of three open clusters with well-known ages and metallicities. We measured effective temperature, Teff, surface gravity, logg, and the metallicity, [Fe/H], of 187 F-G-K stars within the Ariel Reference Sample. We presented the general properties of the sample, including their kinematics which allows us to separate them between thin and thick disc populations. A homogeneous determination of the parameters of the host stars is fundamental in the study of the stars themselves and their planetary systems. Our analysis systematically improves agreement with theoretical models and decreases uncertainties in the mass estimate (from 0.21+/-0.30 to 0.10+/-0.02 M_sun), providing useful data for the Ariel consortium and the astronomical community at large.

Recent ALMA observations on disk substructures suggest the presence of embedded protoplanets in a large number disks. The primordial configurations of these planetary systems can be deduced from the morphology of the disk substructure and serve as initial conditions for numerical investigation of their future evolution. Starting from the initial configurations of 12 multi-planetary systems deduced from ALMA disks, we carried out two-stage N-body simulation to investigate the evolution of the planetary systems at the disk stage as well as the long term orbital stability after the disk dispersal. At the disk stage, our simulation includes both the orbital migration and pebble/gas accretion effects. We found a variety of planetary systems are produced and can be categorised into distant giant planets, Jupiter-like planets, Neptune-like planets and distant small planets. We found the disk stage evolution as well as the final configurations are sensitive to both the initial mass assignments and viscosity. After the disk stage, we implement only mutual gravity between star and planets and introduce stochastic perturbative forces. All systems are integrated for up to 10 Gyr to test their orbital stability. Most planetary systems are found to be stable for at least 10 Gyr with perturbative force in a reasonable range. Our result implies that a strong perturbation source such as stellar flybys is required to drive the planetary system unstable. We discuss the implications of our results on both the disk and planet observation, which may be confirmed by the next generation telescopes such as JWST and ngVLA.

We present a joint spectral analysis of ROSAT PSPC, Swift XRT, and NuSTAR FPMA/B data of the nova-like (NL) cataclysmic variables (CVs), BZ Cam and V592 Cas in the 0.1-78.0 keV band. Plasma models of collisional equilibrium fail to model the 6.0-7.0 iron line complex and continuum with $\chi^2_\nu$ larger than 2.0. Our results show nonequilibrium ionization (NEI) conditions in the X-ray plasma with temperatures of 8.2-9.4 keV and 10.0-12.9 keV for BZ Cam and V592 Cas, respectively. The centroids of He-like and H-like iron ionization lines are not at their equilibrium values as expected from NEI conditions. We find power law spectral components that reveal the existence of scattering and Comptonization with a photon index of 1.50-1.87. We detect a P Cygni profile in the H-like iron line of BZ Cam translating to outflows of 4500-8700 km s$^{-1}$ consistent with the fast winds in the optical and UV. This is the first time such a fast collimated outflow is detected in the X-rays from an accreting CV. An Iron K$\alpha$ line around 6.2-6.5 keV is found revealing the existence of reflection effects in both sources. We study the broadband noise and find that the optically thick disk truncates in BZ Cam and V592 Cas consistent with transition to an advective hot flow structure. V592 Cas also exhibits a quasi-periodic oscillation at 1.4$^{+2.6}_{-0.3}$ mHz. In general, we find that the two NLs portray spectral and noise characteristics as expected from advective hot accretion flows at low radiative efficiency.

Small scale processes are thought to be important for the dynamics of the solar atmosphere. While numerical resolution fundamentally limits their inclusion in MHD simulations, real observations at the same nominal resolution should still contain imprints of sub-resolution effects. This means that the synthetic observables from a simulation of given resolution might not be directly comparable to real observables at the same resolution. It is thus of interest to investigate how inferences based on synthetic spectra from simulations with different numerical resolutions compare, and whether these differences persist after the spectra have been spatially degraded to a common resolution. We aim to compare synthetic spectra obtained from realistic 3D radiative magnetohydrodynamic (rMHD) simulations run at three different numerical resolutions from the same initial atmosphere, using very simple methods for inferring line-of-sight velocities and magnetic fields. Additionally we examine how the differing spatial resolution impacts the results retrieved from the STiC inversion code. We find that while the simple inferences for all three simulations reveal the same large-scale tendencies, the higher resolutions yield more fine-grained structures and more extreme line-of-sight velocities/magnetic fields in concentrated spots even after spatial smearing. We also see indications that the imprints of sub-resolution effects on the degraded spectra result in systematic errors in the inversions, and that these errors increase with the amount of sub-resolution effects included. Fortunately, however, we find that including successively more sub-resolution yields smaller additional effects; i.e. there is a clear trend of diminishing importance for progressively finer sub-resolution effects.

We consider fallback accretion after an ultra-stripped supernova (USSN) that accompanies formation of a binary neutron star (BNS) or a neutron star-black hole binary (NS-BH). The fallback matter initially accretes directly to the nascent NS, while it starts to accrete to the circumbinary disk, typically $0.1\mbox{-}1\, \mathrm{day}$ after the onset of the USSN explosion. The circumbinary disk mass further accretes, forming mini disks around each compact object, with a super-Eddington rate up to a few years. We show that such a system constitutes a binary ultraluminous X-ray source (ULX), and a fraction of the X rays can emerge through the USSN ejecta. We encourage follow-up observations of USSNe within $\lesssim 100\,\rm Mpc$ and $\sim 100\mbox{-}1,000\,\mathrm{day}$ after the explosion using Chandra, XMM Newton and NuSTAR, which could detect the X-ray counterpart with time variations representing the properties of the nascent compact binary, e.g., the orbital motion of the binary, the spin of the NS, and/or the quasiperiodic oscillation of the mini disks.

Radio continuum observations offer a new window on compact objects in globular clusters compared to typical X-ray or optical studies. As part of the MAVERIC survey, we have used the Australia Telescope Compact Array to carry out a deep (median central noise level of approximately 4 microJy per beam) radio continuum survey of 26 southern globular clusters at central frequencies of 5.5 and 9.0 GHz. This paper presents a catalogue of 1285 radio continuum sources in the fields of these 26 clusters. Considering the surface density of background sources, we find significant evidence for a population of radio sources in seven of the 26 clusters, and also identify at least 11 previously known compact objects (6 pulsars and 5 X-ray binaries). While the overall density of radio continuum sources with 7.25-GHz flux densities greater than about 20 microJy in typical globular clusters is relatively low, the survey has already led to the discovery of several exciting compact binaries, including a candidate ultracompact black hole X-ray binary in 47 Tuc. Many of the unclassified radio sources near the centres of the clusters are likely to be true cluster sources, and multi-wavelength follow-up will be necessary to classify these objects and better understand the demographics of accreting compact binaries in globular clusters.

The MAVERIC survey is the first deep radio continuum imaging survey of Milky Way globular clusters, with a central goal of finding and classifying accreting compact binaries, including stellar-mass black holes. Here we present radio source catalogs for 25 clusters with ultra-deep Karl G. Jansky Very Large Array observations. The median observing time was 10 hr per cluster, resulting in typical rms sensitivities of 2.3 and 2.1 uJy per beam at central frequencies of 5.0 and 7.2 GHz, respectively. We detect nearly 1300 sources in our survey at 5 sigma, and while many of these are likely to be background sources, we also find strong evidence for an excess of radio sources in some clusters. The radio spectral index distribution of sources in the cluster cores differs from the background, and shows a bimodal distribution. We tentatively classify the steep-spectrum sources (those much brighter at 5.0 GHz) as millisecond pulsars and the flat-spectrum sources as compact or other kinds of binaries. These provisional classifications will be solidified with the future addition of X-ray and optical data. The outer regions of our images represent a deep, relatively wide field (~ 0.4/sq. deg) and high resolution C band background survey, and we present source counts calculated for this area. We also release radio continuum images for these 25 clusters to the community.

We re-examine possible dependencies on redshift of the spectral parameters of blazars observed at very-high energies (VHEs) with Imaging Atmospheric Cherenkov telescopes (IACTs). This is relevant to assess potential effects with the source distance of the photon to axion-like particle (ALP) mixing, that would deeply affect the propagation of VHE photons across the Universe. We focus our spectral analysis on 38 BL Lac objects (32 high-peaked and 6 intermediate-peaked) up to redshift $z\simeq 0.5$, and a small sample of 5 Flat Spectrum Radio Quasars up to $z=1$ treated independently to increase the redshift baseline. The 78 independent spectra of these sources are first of all carefully corrected for the gamma-gamma interaction with photons of the Extragalactic Background Light, that are responsible for the major redshift-dependent opacity effect. Then, the corrected spectra are fitted with simple power-laws to infer the intrinsic spectral indices $\Gamma_{\rm em}$ at VHE, to test the assumption that such spectral properties are set by the local rather than the global cosmological environment. We find some systematic anti-correlations with redshift of $\Gamma_{\rm em}$ that might indicate, although with low-significance, a spectral anomaly potentially requiring a revision of the photon propagation process. More conclusive tests with higher statistical significance will require the observational improvements offered by the forthcoming new generation of Cherenkov arrays (CTA, ASTRI, LHAASO).

High-density cores (HDCs) of galaxy superclusters that embed rich clusters and groups of galaxies are the earliest large objects to form in the cosmic web, and the largest objects that may collapse in the present or future. We study the dynamical state and possible evolution of the HDCs in the BOSS Great Wall (BGW) superclusters at redshift $z \approx 0.5$ in order to understand the growth and evolution of structures in the Universe. We derived the density contrast values for the spherical collapse model in a wide range of redshifts and used these values to study the dynamical state and possible evolution of the HDCs of the BGW superclusters. The masses of the HDCs were calculated using stellar masses of galaxies in them. We found the masses and radii of the turnaround and future collapse regions in the HDCs and compared them with those of local superclusters. We determined eight HDCs in the BGW superclusters. The masses of their turnaround regions are in the range of $M_{\mathrm{T}} \approx 0.4 - 3.3\times~10^{15}h^{-1}M_\odot,$ and radii are in the range of $R_{\mathrm{T}} \approx 3.5 - 7 h^{-1}$Mpc. The radii of their future collapse regions are in the range of $R_{\mathrm{FC}} \approx 4 - 8h^{-1}$Mpc. Distances between individual cores in superclusters are much larger: of the order of $25 - 35h^{-1}$Mpc. The richness and sizes of the HDCs are comparable with those of the HDCs of the richest superclusters in the local Universe. The BGW superclusters will probably evolve to several poorer superclusters with masses similar to those of the local superclusters. This may weaken the tension with the $\Lambda$CDM model, which does not predict a large number of very rich and large superclusters in our local cosmic neighbourhood, and explains why there are no superclusters as elongated as those in the BGW in the local Universe.

Blazars, a subset of powerful active galactic nuclei, feature relativistic jets that shine in a broadband electromagnetic radiation, e. g. from radio to TeV emission. Here I present the results of the studies that explore gamma-ray and optical variability properties of a sample of gamma-ray bright sources Several methods of time-series analyses are performed on the decade-long optical and Fermi/LAT observations. The main results are as follows: The sources are found highly variable in both the bands, and the gamma-ray power spectral density is found to be consistent with flicker noise suggesting long-memory processes at work. While comparing two emission, not only the overall optical and the $\gamma$-ray emission are highly correlated but also both the observation distributions exhibit heavy tailed log-normal distribution and linear RMS-flux relation. In addition, in some of the sources indications of quasi-periodic oscillation were revealed with similar characteristic timescales in both the bands. We discuss the results in light of current blazar models with relativistic shocks propagating down the jet viewed close to the line of sight.

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). In this paper, we present the dust and gas mass-loss rates by the pulsating Asymptotic Giant Branch (AGB) stars and red supergiants (RSGs) across the stellar disc of M33.

It is shown that the Earth System (ES) can, due to the impact of human activities, behave in a chaotic fashion. Our arguments are based on the assumption that the ES can be described by a Landau-Ginzburg model, which on its own allows for predicting that the ES evolves, through regular trajectories in the phase space, towards a Hothouse Earth scenario for a finite amount of human-driven impact. Furthermore, we find that the equilibrium point for temperature fluctuations can exhibit bifurcations and a chaotic pattern if the human impact follows a logistic map.

There are only five radio-loud quasars currently known within 1 Gyr from the Big Bang ($z>6$) and the properties of their host galaxies have not been explored in detail. We present a NOrthern Extended Millimeter Array (NOEMA) survey of [CII] (158 $\mu$m) and underlying continuum emission of four $z>6$ radio-loud quasars, revealing their diverse properties. J0309+2717 ($z=6.10$) has a bright [CII] line and underlying continuum, implying a starburst with a star-formation rate SFR=$340-1200$ $M_\odot$ yr$^{-1}$. J1429+5447 ($z=6.18$) has a SFR=$520-870$ $M_{\odot}$yr$^{-1}$ and its [CII] profile is consistent with two Gaussians, which could be interpreted as a galaxy merger. J1427+3312 ($z=6.12$) has a moderate SFR=$30-90$ $M_\odot$ yr$^{-1}$. Notably, this is a broad absorption line quasar and we searched for the presence of high-velocity outflows in the host galaxy. Although the NOEMA data reveal a tentative broad component of the [CII] line as wide as $\sim$1400~km~s$^{-1}$, the sensitivity of our current data is not sufficient to confirm it. Finally, P172+18 ($z=6.82$) is undetected in both [CII] and continuum, implying a SFR$<22-40$ $M_{\odot}$yr$^{-1}$. The broad range of SFRs is similar to what is observed in radio-quiet quasars at similar redshifts. If radio jets do not significantly contribute to both [CII] and IR luminosities, this suggest no feedback from the jet on the star formation in the host galaxy.

Quadratic gravity constitutes a prototypical example of a perturbatively renormalizable quantum theory of the gravitational interactions. In this work, we construct the associated phase space of static, spherically symmetric, and asymptotically flat spacetimes. It is found that the Schwarzschild geometry is embedded in a rich solution space comprising horizonless, naked singularities and wormhole solutions. Characteristically, the deformed solutions follow the Schwarzschild solution up outside of the photon sphere while they differ substantially close to the center of gravity. We then carry out an analytic analysis of observable signatures accessible to the Event Horizon Telescope, comprising the size of the black hole shadow as well as the radiation emitted by infalling matter. On this basis, we argue that it is the brightness within the shadow region which constrains the phase space of solutions. Our work constitutes the first step towards bounding the phase space of black hole type solutions with a clear quantum gravity interpretation based on observational data.

Buoyancy-restored modes inside neutron stars depend sensitively on both the microphysical (e.g., composition and entropy gradients) and macrophysical (e.g., stellar mass and radius) properties of the star. Asteroseismology efforts for $g$-modes are therefore particularly promising avenues for recovering information concerning the nuclear equation of state. In this work it is shown that the overall low-temperature $g$-space consists of multiple groups corresponding to different classes of equation of state (e.g., hadronic vs. hybrid). This is in contrast to the case of pressure-driven modes, for example, which tend to follow a universal relation regardless of microphysical considerations. Using a wide library of currently-viable equations of state, perturbations of static, stratified stars are calculated in general relativity to demonstrate in particular how $g$-space groupings can be classified according to the mean mass density, temperature, central speed of sound, and tidal deformability. Considering present and future observations regarding gravitational waves, accretion outbursts, quasi-periodic oscillations, and precursor flashes from gamma-ray bursts, it is shown how one might determine which group the $g$-modes belong to.

Among third-generation ground-based gravitational-wave detectors proposed for the next decade, Einstein Telescope provides a unique kind of null stream $\unicode{x2014}$ the signal-free linear combination of data $\unicode{x2014}$ that enables otherwise inaccessible tests of the noise models. We project and showcase challenges in modeling the noise in the 2030-s and how it will affect the performance of third-generation detectors. We find that the null stream of Einstein Telescope is capable of entirely eliminating transient detector glitches that are known to limit current gravitational-wave searches. The techniques we discuss are computationally efficient and do not require a-priori knowledge about glitch models. Furthermore, we show how the null stream can be used to provide an unbiased estimation of the noise power spectrum necessary for online and offline data analyses even with multiple loud signals in band. We overview other approaches to utilizing the null stream. Finally, we comment on the limitations and future challenges of null stream analyses for Einstein Telescope and arbitrary detector networks.

High-energy neutrinos from astrophysical transients serve as a probe of neutrino physics beyond the Standard Model. In particular, nonstandard interaction of neutrinos with the cosmic neutrino background or dark matter (DM) may have imprints on not only their spectra but also the arrival and time-delay distributions. Assuming that the interaction occurs at most once during the neutrino propagation, we provide analytic formulas for light curves of the neutrino echoes induced by BSM. The formulas can be used for constraining neutrino-neutrino coupling and neutrino-DM coupling.

The deep interrelation between elementary particle physics and cosmology manifests itself when one considers the contribution of quantum fluctuations of vacuum fields to the dark energy and the effective cosmological constant. The contribution of zero-point energy exceeds by many orders of magnitude the observational cosmological upper bound on the energy density of the universe. Therefore it seems natural to expect that vacuum fluctuations of the fundamental fields would influence the cosmological evolution in any way. Our aim in this review article is to describe a recent investigation of the influence of the Yang-Mills vacuum polarisation and of the chromomagnetic condensation on the evolution of Friedmann cosmology, on inflation and on primordial gravitational waves. We derive the quantum energy-momentum tensor and the corresponding quantum equation of state for gauge field theory using the effective Lagrangian approach. The energy-momentum tensor has a term proportional to the space-time metric and provides a finite non-diverging contribution to the effective cosmological constant. This allows to investigate the influence of the gauge field theory vacuum polarisation on the evolution of Friedmann cosmology, inflation and primordial gravitational waves. The Type I-IV solutions of the Friedmann equations induced by the gauge field theory vacuum polarisation provide an alternative inflationary mechanism and a possibility for late-time acceleration. The Type II solution of the Friedmann equations generates the initial exponential expansion of the universe of finite duration and the Type IV solution demonstrates late-time acceleration. The solutions fulfil the necessary conditions for the amplification of primordial gravitational waves.

Recent experimental and ab initio theory investigations of the 208Pb neutron skin thickness are sufficiently precise to inform the neutron star equation of state. In particular, the strong correlation between the 208Pb neutron skin thickness and the pressure of neutron matter at normal nuclear densities leads to modified predictions for the radii, tidal deformabilities, and moments of inertia of typical 1.4 solar-mass neutron stars. In the present work, we study the relative impact of these recent analyses of the 208Pb neutron skin thickness on bulk properties of neutron stars within a Bayesian statistical analysis. Two models for the equation of state prior are employed in order to study the role of the highly uncertain high-density equation of state. From our combined Bayesian analysis of nuclear theory, nuclear experiment, and observational constraints on the dense matter equation of state, we find at the 90% credibility level $R_{1.4}=12.36^{+0.38}_{-0.73}$ km for the radius of a 1.4 solar-mass neutron star, $R_{2.0}=11.96^{+0.94}_{-0.71}$ km for the radius of a 2.0 solar-mass neutron star, $\Lambda_{1.4}=440^{+103}_{-144}$ for the tidal deformability of a 1.4 solar-mass neutron star, and $I_{1.338}=1.425^{+0.074}_{-0.146}\, \times 10^{45}\,\rm{g\,cm}^{2}$ for the moment of inertia of PSR J0737-3039A whose mass is 1.338 solar masses.

New neutrino interactions beyond the Standard Model (BSM) have been of much interest in not only particle physics but also cosmology and astroparticle physics. We numerically investigate the time delay distribution of astrophysical neutrinos that interact with the cosmic neutrino background. Using the Monte Carlo method, we develop a framework that enables us to simulate the time-dependent energy spectra of high-energy neutrinos that experience even multiple scatterings en route and to handle the sharp increase in the cross section at the resonance energy. As an example, we focus on the case of secret neutrino interactions with a scalar mediator. While we find the excellent agreement between analytical and simulation results for small optical depths, our simulations enable us to study even optically-thick cases that are not described by the simplest analytic estimates. Our simulations are used to understand effects of cosmological redshifts, neutrino spectra and flavors. The developments will be useful for probing BSM neutrino interactions with not only current neutrino detectors such as IceCube and Super-Kamiokande but also future neutrino detectors such as IceCube-Gen2 and Hyper-Kamiokande.

We examine the constraining power of current gravitational-wave data on scalar-tensor-Gauss-Bonnet theories that allow for the spontaneous scalarization of black holes. In the fiducial model that we consider, a slowly rotating black hole must scalarize if its size is comparable to the new length scale $\lambda$ that the theory introduces, although rapidly rotating black holes of any mass are effectively indistinguishable from their counterparts in general relativity. With this in mind, we use the gravitational-wave event GW190814$\,\unicode{x2014}\,$whose primary black hole has a spin that is bounded to be small, and whose signal shows no evidence of a scalarized primary$\,\unicode{x2014}\,$to rule out a narrow region of the parameter space. In particular, we find that values of ${\lambda \in [56, 96]~M_\odot}$ are strongly disfavored with a Bayes factor of $0.1$ or less. We also include a second event, GW151226, in our analysis to illustrate what information can be extracted when the spins of both components are poorly measured.

Stein variational gradient descent (SVGD) is a general-purpose optimization-based sampling algorithm that has recently exploded in popularity, but is limited by two issues: it is known to produce biased samples, and it can be slow to converge on complicated distributions. A recently proposed stochastic variant of SVGD (sSVGD) addresses the first issue, producing unbiased samples by incorporating a special noise into the SVGD dynamics such that asymptotic convergence is guaranteed. Meanwhile, Stein variational Newton (SVN), a Newton-like extension of SVGD, dramatically accelerates the convergence of SVGD by incorporating Hessian information into the dynamics, but also produces biased samples. In this paper we derive, and provide a practical implementation of, a stochastic variant of SVN (sSVN) which is both asymptotically correct and converges rapidly. We demonstrate the effectiveness of our algorithm on a difficult class of test problems -- the Hybrid Rosenbrock density -- and show that sSVN converges using three orders of magnitude fewer gradient evaluations of the log likelihood than its stochastic SVGD counterpart. Our results show that sSVN is a promising approach to accelerating high-precision Bayesian inference tasks with modest-dimension, $d\sim\mathcal{O}(10)$.