Papers for Monday, Jul 31 2023

Frymire & Ardila (2023) reported an anomalous flux variation in the Transiting Exoplanet Survey Satellite (TESS) Sector 43 light curve of the white dwarf HZ 4. We show that this flux variation was caused by the main-belt asteroid 4382 Stravinsky traversing the nearby TESS pixels, and it is therefore not a cause for concern regarding the continued use of HZ 4 as a photometric standard star.

Photomultiplier tubes (PMTs) are a central component of neutrino telescopes such as IceCube and KM3NeT, and an accurate understanding and measurement of their properties is indispensable for improvements of these experiments. In this contribution we focus on a detailed investigation of the photocathode and the dynode system and their influence on the performance of the PMT. Three methods are used for the investigation. Ellipsometry measurements of the photocathode analyze its optical properties in terms of absorption probability and refractive index. Scans of the photocathode in single photon illumination probe performance differences along the photocathode surface. Systematic deviations in the resulting amplifications are compared to electric field and electron tracing simulations through the dynode system to understand the measured values. The goal is an extensive understanding of efficiency, amplification, and timing as functions of wavelength and impact point as well as angle.

We study the formation of Pop III stars by performing radiation hydrodynamics simulations for three different initial clouds extracted from cosmological hydrodynamics simulations. Starting from the cloud collapse stage, we follow the growth of protostars by accretion for $\sim 10^5$ yr until the radiative feedback from the protostars suppresses the accretion and the stellar properties are nearly fixed. We find that the Pop III stars form in massive and wide binaries/small-multiple stellar systems, with masses $>30\,M_\odot$ and separations $>2000$ au. We also find that the properties of the final stellar system correlate with those of the initial clouds: the total mass increases with the cloud-scale accretion rate, and the angular momentum of the binary orbit matches that of the initial cloud. While the total mass of the system in our simulations is consistent with our previous single-star formation simulations, individual masses are lower due to mass sharing, suggesting potential modification in the extent of feedback from Pop III stars in the subsequent evolution of the Universe. We also identify such systems as mini-binaries embedded in a wider outer multiple-star system, which could evolve into progenitors for observed gravitational wave events.

We present 3D full star simulations, reaching up to 90% of the total stellar radius, for three $7M_\odot$ stars of different ages (ZAMS, midMS and TAMS). A comparison with several theoretical prescriptions shows the generation spectra for all three ages are dominated by convective plumes. Two distinct overshooting layers are observed, with most plumes stopped within the layer situated directly above the convective boundary (CB); overshooting to the second, deeper layer becomes increasingly more infrequent with stellar age. Internal gravity wave (IGW) propagation is significantly impacted in the midMS and TAMS models as a result of some IGWs getting trapped within their Brunt-V\"{a}is\"{a}l\"{a} frequency spikes. A fundamental change in the wave structure across radius is also observed, driven by the effect of density stratification on IGW propagation causing waves to become evanescent within the radiative zone, with older stars being affected more strongly. We find that the steepness of the frequency spectrum at the surface increases from ZAMS to the older models, with older stars also showing more modes in their spectra.

The mechanisms that generate "seed" magnetic fields in our Universe and that amplify them throughout cosmic time remain poorly understood. By means of fully-kinetic particle-in-cell simulations of turbulent, initially unmagnetized plasmas, we study the genesis of magnetic fields via the Weibel instability and follow their dynamo growth up to near-equipartition levels. In the kinematic stage of the dynamo, we find that the rms magnetic field strength grows exponentially with rate $\gamma_B \simeq 0.4\,u_{\rm rms}/L$, where $L/2 \pi$ is the driving scale and $u_{\rm rms}$ is the rms turbulent velocity. In the saturated stage, the magnetic field energy reaches about half of the turbulent kinetic energy. Here, magnetic field growth is balanced by dissipation via reconnection, as revealed by the appearance of plasmoid chains. At saturation, the integral-scale wavenumber of the magnetic spectrum approaches $k_{\rm int}\simeq 12\pi/L$. Our results show that turbulence -- induced by, e.g., the gravitational build-up of galaxies and galaxy clusters -- can magnetize collisionless plasmas with large-scale near-equipartition fields.

Motivated by spectroscopic confirmation of three overdense regions in the COSMOS field at $z\sim3.35$, we analyze the uniquely deep multi-wavelength photometry and extensive spectroscopy available in the field to identify any further related structure. We construct a three dimensional density map using the Voronoi tesselation Monte Carlo method and find additional regions of significant overdensity. Here we present and examine a set of six overdense structures at $3.20<z<3.45$ in the COSMOS field, the most well characterized of which, PCl~J0959+0235, has 80 spectroscopically confirmed members and an estimated mass of $1.35\times 10^{15}$~M$_\odot$, and is modeled to virialize at $z\sim1.5-2.0$. These structures contain ten overdense peaks with $>5\sigma$ overdensity separated by up to 70 cMpc, suggestive of a proto-supercluster similar to the Hyperion system at $z\sim2.45$. Upcoming photometric surveys with JWST such as COSMOS-Web, and further spectroscopic follow-up will enable more extensive analysis of the evolutionary effects that such an environment may have on its component galaxies at these early times.

With the imaging and characterization of the horizon-scale images of M87* and Sgr A* by the Event Horizon Telescope (EHT), it has become possible to resolve the near-horizon region of astrophysical black holes. As a result, there has been considerable interest in the implications of the measurement of the shadow size, i.e., the asymptotic photon ring. We explore the general implications of such a measurement, identifying what is and, more importantly, is not constrained by such measurements, with applications to EHT and future instruments. We consider a general spherically symmetric metric, which effectively applies for a polar observer (appropriate for M87*) in the slow rotation limit. We propose a nonperturbative, nonparametric spacetime-domain characterization of shadow size and related measurements that makes explicit the nature and power (or lack thereof) of shadow-size-based constraints, and facilitates comparisons among observations and targets.

The cooling envelope model for tidal disruption events (TDE) postulates that while the stellar debris streams rapidly dissipate their bulk kinetic energy (``circularize"), this does not necessarily imply rapid feeding of the supermassive black hole (SMBH). The bound material instead forms a large pressure-supported envelope which powers optical/UV emission as it undergoes gradual Kelvin-Helmholtz contraction. We present results interpreting a sample of 12 optical TDE observed with the Zwicky Transient Facility within the cooling envelope model in order to constrain the SMBH mass $M_{\rm BH}$, stellar mass $M_{\star}$, and orbital penetration factor $\beta$. The distributions of inferred properties from our sample broadly follow the theoretical expectations of loss-cone analysis assuming a standard stellar initial mass function. However, we find a deficit of events with $M_{\rm BH} \lesssim 5\times 10^{5}M_{\odot}$ and $M_{\star} \lesssim 0.5M_{\odot}$, which could result in part from the reduced detectability of TDEs with these properties. Our model fits also illustrate the predicted long delay between the optical light curve peak and when the SMBH accretion rate reaches its maximum. The latter occurs only once the envelope contracts to the circularization radius on a timescale of months to years, consistent with delayed-rising X-ray and non-thermal radio flares seen in a growing number of TDE.

A stochastic gravitational wave background is a prediction of a number of astrophysical and cosmological phenomena including early Universe Cosmology. Recently, the NANOGrav Collaboration reported conclusive evidence for a stochastic gravitational-wave background. We analyze the NANOGrav signal assuming it is of primordial origin including the reheating phase. We use the latest measurements from NANOGrav to constrain the Universe's reheating equation of state $w_{re}$ the reheating temperature, $T_{re}$, the tensor to scalar ratio $r$, and the tensor tilt $n_t$. Assuming the constant equation of state $w_{re}$ responsible for reheating phase, we find preference for instant reheating, $w_{re} = 0.36^{+0.15}_{-0.28}$, and a very blue tilt $n_t = 1.94^{+0.43}_{-0.88}$. We find a degeneracy between the tensor to scalar ratio $r$ and $T_{re}$ and suggest ways to break this degeneracy. In all cases where the reheating temperature is constrained, it is constrained to be very low with $T_{re}\leq 10^5 GeV$. We further find that a scale-invariant spectrum as suggested by inflation implies a stiff equation of state $w_{re}=19/3$. If extrapolated, the blue-tilted primordial spectrum that agrees with the NANOGrav signal at corresponding frequencies is incompatible with the LIGO bound. This incompatibility is another challenge for connecting NANOGrav with the primordial spectrum. We discuss a number of ways to circumvent this issue. We split the spectrum into a sum of astrophysical and primordial spectra and constrain the astrophysical and primordial components using NANOGrav data and the LIGO bound. In another attempt, we use the same data and constrain the running of the spectrum. Any of these or a combination of such methods can be used to reconcile the NANOGrav data and the LIGO bound with the primordial power spectrum.

We performed the first photometric study of the CSS J003106.8+313347 W Ursae Majoris (W UMa)-type system based on ground-based observations. We extracted times of minima from our observations and proposed a linear ephemeris based on the increasing incline of the orbital period using a Markov chain Monte Carlo (MCMC) approach. The PHOEBE Python code and the MCMC approach were used for the light curve analysis. This system did not need starspots for the light curve analysis. Mass ratio, fillout factor, and inclination were obtained as 0.699, 0.322, and 60.6deg respectively. We also estimated the absolute parameters of the system using the Gaia DR3 parallax method. Therefore, the masses, radii, and luminosities have been determined to be M1=1.675, M2=1.171, R1=1.292, R2=1.097, L1=1.348, and L2=1.221. The orbital angular momentum (J0) of the CSS J003106.8+313347 illustrates that this system is located in a region of contact binaries. The positions of the primary and secondary components on the Hertzsprung-Russell (HR) diagram are depicted.

Currently available star cluster catalogues from HST imaging of nearby galaxies heavily rely on visual inspection and classification of candidate clusters. The time-consuming nature of this process has limited the production of reliable catalogues and thus also post-observation analysis. To address this problem, deep transfer learning has recently been used to create neural network models which accurately classify star cluster morphologies at production scale for nearby spiral galaxies (D < 20 Mpc). Here, we use HST UV-optical imaging of over 20,000 sources in 23 galaxies from the Physics at High Angular Resolution in Nearby GalaxieS (PHANGS) survey to train and evaluate two new sets of models: i) distance-dependent models, based on cluster candidates binned by galaxy distance (9-12 Mpc, 14-18 Mpc, 18-24 Mpc), and ii) distance-independent models, based on the combined sample of candidates from all galaxies. We find that the overall accuracy of both sets of models is comparable to previous automated star cluster classification studies (~60-80 per cent) and show improvement by a factor of two in classifying asymmetric and multi-peaked clusters from PHANGS-HST. Somewhat surprisingly, while we observe a weak negative correlation between model accuracy and galactic distance, we find that training separate models for the three distance bins does not significantly improve classification accuracy. We also evaluate model accuracy as a function of cluster properties such as brightness, colour, and SED-fit age. Based on the success of these experiments, our models will provide classifications for the full set of PHANGS-HST candidate clusters (N ~ 200,000) for public release.

NASA is engaged in planning for a Habitable Worlds Observatory (HabWorlds), a coronagraphic space mission to detect rocky planets in habitable zones and establish their habitability. Surface liquid water is central to the definition of planetary habitability. Photometric and polarimetric phase curves of starlight reflected by an exoplanet can reveal ocean glint, rainbows and other phenomena caused by scattering by clouds or atmospheric gas. Direct imaging missions are optimised for planets near quadrature, but HabWorlds' coronagraph may obscure the phase angles where such optical features are strongest. The range of accessible phase angles for a given exoplanet will depend on the planet's orbital inclination and/or the coronagraph's inner working angle (IWA). We use a recently-created catalog relevant to HabWorlds of 164 stars to estimate the number of exo-Earths that could be searched for ocean glint, rainbows, and polarization effects due to Rayleigh scattering. We find that the polarimetric Rayleigh scattering peak is accessible in most of the exo-Earth planetary systems. The rainbow due to water clouds at phase angles of ${\sim}20-60^\circ$ would be accessible with HabWorlds for a planet with an Earth equivalent instellation in ${\sim}{46}$ systems, while the ocean glint signature at phase angles of ${\sim}130-170^\circ$ would be accessible in ${\sim}{16}$ systems, assuming an IWA${=}62$ mas ($3\lambda/D$). Improving the IWA${=}41$ mas ($2\lambda/D$) increases accessibility to rainbows and glints by factors of approximately 2 and 3, respectively. By observing these scattering features, HabWorlds could detect a surface ocean and water cycle, key indicators of habitability.

Accretion of magnetized gas on compact astrophysical objects such as black holes has been successfully modeled using general relativistic magnetohydrodynamic (GRMHD) simulations. These simulations have largely been performed in the Kerr metric, which describes the spacetime of a vacuum and stationary spinning black hole (BH) in general relativity (GR). The simulations have revealed important clues on the physics of accretion and jets near the BH event horizon, and have been used to interpret recent Event Horizon Telescope images of the supermassive BHs, M87$^*$ and Sgr A$^*$. GRMHD simulations require the spacetime metric in horizon-penetrating coordinates such that all metric coefficients are regular at the event horizon. The Kerr metric and its electrically charged spinning analog, the Kerr-Newman metric, are currently the only metrics available in such coordinates. We report here horizon-penetrating forms of a large class of stationary, axisymmetric, spinning metrics. These can be used to carry out GRMHD simulations of accretion on spinning, nonvacuum BHs and non-BHs within GR, as well as accretion on spinning objects described by non-GR metric theories of gravity.

Monitoring turbulence parameters is crucial in high-angular resolution astronomy for various purposes, such as optimising adaptive optics systems or fringe trackers. The former are present at most modern observatories and will remain significant in the future. This makes them a valuable complementary tool for the estimation of turbulence parameters. The feasibility of estimating turbulence parameters from low-resolution sensors remains untested. We perform seeing estimates for both simulated and on-sky telemetry data sourced from the new adaptive optics module installed on the four Auxiliary Telescopes of the Very Large Telescope Interferometer. The seeing estimates are obtained from a modified and optimised algorithm that employs a chi-squared modal fitting approach to the theoretical von K\'arm\'an model variances. The algorithm is built to retrieve turbulence parameters while simultaneously estimating and accounting for the remaining and measurement error. A Monte Carlo method is proposed for the estimation of the statistical uncertainty of the algorithm. The algorithm is shown to be able to achieve per cent accuracy in the estimation of the seeing with a temporal horizon of 20s on simulated data. A 0.76" +/- 1.2%$|_\mathrm{stat}$ +/- 1.2%$|_\mathrm{sys}$ median seeing was estimated from on-sky data collected from 2018 and 2020. The spatial distribution of the Auxiliary Telescopes across the Paranal Observatory was found to not play a role in the value of the seeing.

We present the results of our ALMA $\lesssim$0.5 kpc-resolution dense molecular line (HCN and HCO$^{+}$ J=2-1, J=3-2, and J=4-3) observations of 12 nearby (ultra)luminous infrared galaxies ([U]LIRGs). After matching beam sizes of all molecular line data to the same values in all (U)LIRGs, we derive molecular line flux ratios, by extracting spectra in the central 0.5, 1, 2 kpc circular regions, and 0.5-1 and 1-2 kpc annular regions. Based on non-LTE model calculations, we quantitatively confirm that the innermost ($\lesssim$0.5 kpc) molecular gas is very dense ($\gtrsim$10$^{5}$ cm$^{-3}$) and warm ($\gtrsim$300 K) in ULIRGs, and that in one LIRG is also modestly dense (10$^{4-5}$ cm$^{-3}$) and warm ($\sim$100 K). We then investigate the spatial variation of the HCN-to-HCO$^{+}$ flux ratios and high-J to low-J flux ratios of HCN and HCO$^{+}$. A subtle sign of decreasing trend of these ratios from the innermost ($\lesssim$0.5 kpc) to outer nuclear (0.5-2 kpc) region is discernible in a significant fraction of the observed ULIRGs. For two AGN-hosting ULIRGs which display the trend most clearly, we find based on a Bayesian approach that the HCN-to-HCO$^{+}$ abundance ratio and gas kinetic temperature systematically increase from the outer nuclear to the innermost region. We suggest that this trend comes from potential AGN effects, because no such spatial variation is found in a starburst-dominated LIRG.

The publication of the \emph{Gaia} catalogue and improvements in methods to determine memberships and fundamental parameters of open clusters has led to major advances in recent years. However, important parameters such as the masses of these objects, although being studied mostly in some isolated cases, have not been addressed in large homogeneous samples based on \emph{Gaia} data, taking into account details such as binary fractions. Consequently, relevant aspects such as the existence of mass segregation were not adequately studied. Within this context, in this work, we introduce a new method to determine individual stellar masses, including an estimation for the ones in binary systems. This method allows us to study the mass of open clusters, as well as the mass functions of the binary star populations. We validate the method and its efficiency and characterize uncertainties using a grid of synthetic clusters with predetermined parameters. We highlight the application of the method to the Pleiades cluster, showing that the results obtained agree with the current consensus in the literature as well as recent \emph{Gaia} data. We then applied the procedure to a sample of 773 open clusters with fundamental parameters determined using \emph{Gaia Early Data Release 3 (eDR3)} data, obtaining their masses. Subsequently, we investigated the relation between the masses and other fundamental parameters of the clusters. Among the results, we found no significant evidence that clusters in our sample lose and segregate mass with age.

The IceCube Neutrino Observatory is a cubic-kilometer Cherenkov detector at the South Pole, designed to study neutrinos of astrophysical origin. We present an analysis of the Medium Energy Starting Events (MESE) sample, a veto-based event selection that selects neutrinos and efficiently rejects a background of cosmic ray-induced muons This is an extension of the High Energy Starting Event (HESE) analysis, which established the existence of high-energy neutrinos of astrophysical origin. The HESE sample is consistent with a single power law spectrum with best-fit index $2.87^{+0.20}_{-0.19}$, which is softer than complementary IceCube measurements of the astrophysical neutrino spectrum. While HESE is sensitive to neutrinos above 60 TeV, MESE improves the sensitivity to lower energies, down to 1 TeV. In this analysis we use an improved understanding of atmospheric backgrounds in the astrophysical neutrino sample via more accurate modeling of the detector self-veto. A previous measurement with a 2-year MESE dataset had indicated the presence of a possible 30 TeV excess. With 10 years of data, we have a larger sample size to investigate this excess. We will use this event selection to measure the cosmic neutrino energy spectrum over a wide energy range. The flavor ratio of astrophysical neutrinos will also be discussed.

The study of our Sun holds significant importance in Space Weather research, encompassing a diverse range of phenomena characterized by distinct temporal and spatial scales. To address these complexities, we developed CAFE-AMR, an implementation of an Adaptive Mesh Refinement (AMR) strategy coupled with a Magnetohydrodynamics (MHD) equation solver, aiming to tackle Solar Physics-related problems. CAFE-AMR employs standard fluid dynamics methods, including Finite Volume discretization, HLL and Roe class flux formulas, linear order reconstructors, second-order Runge-Kutta, and Corner Transport Upwind time stepping. In this paper, we present the core structure of CAFE-AMR, discuss and evaluate mesh refinement criteria strategies, and conduct various tests, including simulations of idealized Solar Wind models, relevant for Space Weather applications.

We present rest-frame ultraviolet (UV) images of six luminous quasars at $z \sim 4.8$ obtained with the Hubble Space Telescope (HST). These quasars exhibit a wide range of star formation rates (SFRs) and lie in a wide range of environments. We carefully model and subtract the point-like quasar emission and investigate the morphology of the underlying host galaxies at kpc scales. The residual images allowed identification of potential companion sources, which enabled us to explore the role of galaxy merger scenarios in the co-evolution of the quasars and their hosts. We also search for the mechanism driving extreme SFRs in three of the quasars. We find that the rate of detection of potential companions to the host galaxies does not follow trends between high- and low-SFR sources; i.e., the HST imaging suggests that both high- and low-SFR sources are found in both dense and sparse galactic environments. The suggested role of major mergers driving extreme SFRs cannot be supported by the multiwavelength data in hand. Three of four companion sources, previously revealed by sub-millimeter observations, are not detected in the HST images of three of our quasars. An adapted high-resolution imaging strategy focused on high-SFR sources and extended to a larger quasar sample is required to determine the role of mergers in the processes of star formation and supermassive black hole growth at high redshift.

The astrophysical origins of the binary black hole systems seen with gravitational waves are still not well understood. However, features in the distribution of black-hole masses, spins, redshifts, and eccentricities, provide clues into how these systems form. Much has been learned by investigating these distributions one parameter at a time, however, we can extract additional information by studying the covariance between pairs of parameters. Previous work has shown preliminary support for an anti-correlation between mass ratio $q \equiv m_2/m_1$ and effective inspiral spin $\chi_\mathrm{eff}$ in the binary black hole population. In this study, we test for the existence of this anti-correlation using updated data from the third gravitational wave transient catalogue (GWTC-3), and improving our copula-based framework to employ a more robust model for black-hole spins. We find evidence for an anti-correlation in $(q, \chi_\mathrm{eff})$ with 99.8\% credibility. This may imply high common-envelope efficiencies, stages of super-Eddington accretion, or a tendency for binary black hole systems to undergo mass-ratio reversal during isolated evolution. Covariance in $(q, \chi_\mathrm{eff})$ may also be used to investigate the physics of tidal spin-up as well as the properties of binary-black-hole-forming active galactic nuclei.

The reconstruction of neutrino events in the IceCube experiment is crucial for many scientific analyses, including searches for cosmic neutrino sources. The Kaggle competition "IceCube -- Neutrinos in Deep ice" was a public machine learning challenge designed to encourage the development of innovative solutions to improve the accuracy and efficiency of neutrino event reconstruction. Participants worked with a dataset of simulated neutrino events and were tasked with creating a suitable model to predict the direction vector of incoming neutrinos. From January to April 2023, hundreds of teams competed for a total of $50k prize money, which was awarded to the best performing few out of the many thousand submissions. In this contribution I will present some insights into the organization of this large outreach project, and summarize some of the main findings, results and takeaways.

We propose an observational test to distinguish between the two primary classes of Fast Radio Burst (FRB) radiation models. For an extended FRB source, the strength of spectral amplitude modulation caused by scintillation, which we refer to as the scintillation index, across the measured frequency band is much smaller than the 100% variations expected for a point source. FRB sources easily satisfy the point-source size requirement for scintillation from the Milky Way ISM plasma but may be large enough for certain classes of proposed FRB mechanisms to quench scintillation from plasma in the host galaxy. An FRB source of size smaller than the diffractive scale for scattering in the ISM of the host galaxy, which is about 10$^9$ cm at 1 GHz, would be considered point-like for the purpose of scintillation. The lateral size of the source for a magnetospheric origin of FRBs is expected to be $\lesssim 10^7$ cm, while it is $\gtrsim 10^9$ cm for far-away models, i.e., models in which the emission is generated far from the central engine. Therefore, scintillation in the host galaxy is well-suited for distinguishing between these two types of FRB models. Scatter-broadening of an FRB pulse by plasma in the host galaxy by $\delta t_s$ causes stochastic flux variation with frequency on a scale of $\sim (2\pi\delta t_s)^{-1}$. Determining the scintillation index for an FRB with scatter broadening identified to be from the host galaxy would provide a strong constraint on the FRB radiation mechanism. Since the scintillation bandwidth scales with frequency as $\sim \nu^{4.4}$, it may be observationally easier to determine the flux variation amplitude at a few GHz.

IceCube DeepCore, the existing low-energy extension of the IceCube Neutrino Observatory, was designed to lower the neutrino detection energy threshold to the GeV range. A new extension, called the IceCube Upgrade, will consist of seven additional strings installed within the DeepCore fiducial volume. The new modules will have spacings of about 20 m horizontally and 3 m vertically, compared to about 40-70 m horizontally and 7 m vertically in DeepCore. It will be deployed in the polar season of 2025/26. This additional hardware features new types of optical modules with multi-PMT configurations, as well as calibration devices. This upgrade will more than triple the number of PMT channels with respect to current IceCube, and will significantly enhance its capabilities in the GeV energy range. However, the increased channel count also poses new computational challenges for the event simulation, selection, and reconstruction. In this contribution we present updated oscillation sensitivities based on the latest advancements in simulation, event selection, and reconstruction techniques.

The IceCube Neutrino Observatory deployed 5160 digital optical modules (DOMs) in a cubic kilometer of deep, glacial ice below the geographic South Pole, recording the Cherenkov light of passing charged particles. While the optical properties of the undisturbed ice are nowadays well understood, the properties of the refrozen drill holes still pose a challenge. From camera observations, we expect a central, strongly scattering column shadowing a part of the DOMs' sensitive area. In MC simulation, this effect is commonly modeled as a modification to the DOMs' angular acceptance curve, reducing the forward sensitivity of the DOMs. The associated uncertainty is a dominant detector systematic for neutrino oscillation studies as well as high-energy cascade reconstructions. Over the years, several measurements and fits of the drill holes' optical properties and of the angular acceptance curve have been proposed, some of which are in tension. Here, we present a principle component analysis, which allows us to interpolate between all suggested scenarios, and thus provide a complete systematic variation within a unified framework at analysis level.

Recent discoveries of a significant population of bright galaxies at cosmic dawn $\left(z \gtrsim 10\right)$ have enabled critical tests of cosmological galaxy formation models. In particular, the bright end of the galaxy UV luminosity function (UVLF) appears higher than predicted by many models. Using approximately 25,000 galaxy snapshots at $8 \leq z \leq 12$ in a suite of FIRE-2 cosmological "zoom-in'' simulations from the Feedback in Realistic Environments (FIRE) project, we show that the observed abundance of UV-bright galaxies at cosmic dawn is reproduced in these simulations with a multi-channel implementation of standard stellar feedback processes, without any fine-tuning. Notably, we find no need to invoke previously suggested modifications such as a non-standard cosmology, a top-heavy stellar initial mass function, or a strongly enhanced star formation efficiency. We contrast the UVLFs predicted by bursty star formation in these original simulations to those derived from star formation histories (SFHs) smoothed over prescribed timescales (e.g., 100 Myr). The comparison demonstrates that the strongly time-variable SFHs predicted by the FIRE simulations play a key role in correctly reproducing the observed, bright-end UVLFs at cosmic dawn: the bursty SFHs induce order-or-magnitude changes in the abundance of UV-bright ($M_\mathrm{UV} \lesssim -20$) galaxies at $z \gtrsim 10$. The predicted bright-end UVLFs are consistent with both the spectroscopically confirmed population and the photometrically selected candidates. We also find good agreement between the predicted and observationally inferred integrated UV luminosity densities, which evolve more weakly with redshift in FIRE than suggested by some other models.

Recent JWST observations of the z=10.6 galaxy GN-z11 have revealed a very high gas-phase nitrogen abundance (higher than four times the solar value), a very small half-light radius(~ 60 pc), and a large stellar mass (M_s ~ 10^9 M_sun) for its size. We consider that this object is a forming galactic nucleus or ultra-compact dwarf galaxy rather than a proto globular cluster, and thereby investigate the chemical abundance pattern using one-zone chemical evolution models.The principal results of the models are as follows. The observed log (N/O) > -0.24, log (C/O)>-0.78, and 12+log (O/H) ~ 7.8 can be self-consistently reproduced by the models both with very short star formation timescales (< 10^7 yr) and with top-heavy stellar initial mass functions (IMFs). The adopted assumption of no chemical enrichment by massive (m>25 M_sun) core collapse supernovae (CCSNe) is also important for the reproduction of high gas-phase log (N/O), because such CCSNe can decrease high log (N/O) of gas polluted by OB and Wolf-Rayet stars. GN-z11 can have a significant fraction (>0.5) of nitrogen-rich ([N/Fe]>0.5) stars, which implies a possible link between nitrogen-rich stellar populations of the inner Galaxy and giant elliptical galaxies and high-z objects with high gas-phase log (N/O) like GN-z11.

We search for quasi-stellar objects (QSOs) in a wide area of the south ecliptic pole (SEP) field, which has been and will continue to be intensively explored through various space missions. For this purpose, we obtain deep broadband optical images of the SEP field covering an area of $\sim$$14.5\times14.5$ deg$^2$ with the Korea Microlensing Telescope Network. The 5$\sigma$ detection limits for point sources in the $BVRI$ bands are estimated to be $\sim$22.59, 22.60, 22.98, and 21.85 mag, respectively. Utilizing data from Wide-field Infrared Survey Explorer, unobscured QSO candidates are selected among the optically point-like sources using the mid-infrared (MIR) and optical-MIR colors. To further refine our selection and eliminate any contamination not adequately removed by the color-based selection, we perform the spectral energy distribution fitting with archival photometric data ranging from optical to MIR. As a result, we identify a total of 2,383 unobscured QSO candidates in the SEP field. We also apply a similar method to the north ecliptic pole field using the Pan-STARRS data and obtain a similar result of identifying 2,427 candidates. The differential number count per area of our QSO candidates is in good agreement with those measured from spectroscopically confirmed ones in other fields. Finally, we compare the results with the literature and discuss how this work will be implicated in future studies, especially with the upcoming space missions.

Protoclusters are the progenitors of massive galaxy clusters. Understanding the properties of these structures is important for building a complete picture of cluster formation and for understanding the impact of environment on galaxy evolution. Future cosmic microwave background (CMB) surveys may provide insight into the properties of protoclusters via observations of the thermal Sunyaev Zel'dovich (SZ) effect and gravitational lensing. Using realistic hydrodynamical simulations of protoclusters from the Three Hundred Project, we forecast the ability of CMB Stage 4-like (CMB-S4) experiments to detect and characterize protoclusters with observations of these two signals. For protoclusters that are the progenitors of clusters at $z = 0$ with $M_{200c} \gtrsim 10^{15}\,M_{\odot}$ we find that the S4-Ultra deep survey has a roughly 20% chance of detecting the main halos in these structures with ${\rm SNR} > 5$ at $z \sim 2$ and a 10% chance of detecting them at $z \sim 2.5$, where these probabilities include the impacts of noise, CMB foregrounds, and the different possible evolutionary histories of the structures. On the other hand, if protoclusters can be identified using alternative means, such as via galaxy surveys like LSST and Euclid, CMB-S4 will be able to obtain high signal-to-noise measurements of their stacked lensing and SZ signals, providing a way to measure their average mass and gas content. With a sample of 2700 protoclusters at $z = 3$, the CMB-S4 wide survey can measure the stacked SZ signal with a signal-to-noise of 7.2, and the stacked lensing signal with a signal-to-noise of 5.7. Future CMB surveys thus offer exciting prospects for understanding the properties of protoclusters.

Astrophysical neutrinos detected by the IceCube observatory can be of Galactic or extragalactic origin. The collective contribution of all the detected neutrinos allows us to measure the total diffuse neutrino Galactic and extragalactic signal. In this work, we describe a simulation package that makes use of this diffuse Galactic contribution information to simulate a population of Galactic sources distributed in a manner similar to our own galaxy. This is then compared with the sensitivities reported by different IceCube data samples to estimate the number of sources that IceCube can detect. We provide the results of the simulation that allows us to make statements about the nature of the sources contributing to the IceCube diffuse signal.

Searches for neutrinos from gravitational wave events have been performed utilizing the wide energy range of the IceCube Neutrino Observatory. We discuss results from these searches during the third observing run (O3) of the advanced LIGO and Virgo detectors, including a low-latency follow-up of public candidate alert events in O3, an archival search on high-energy track data, and a low-energy search employing IceCube-DeepCore. The dataset of high-energy tracks is mainly sensitive to muon neutrinos, while the low energy dataset is sensitive to neutrinos of all flavors. In all of these searches, we present upper limits on the neutrino flux and isotropic equivalent energy emitted in neutrinos. We also discuss future plans for additional searches, including extending the low-latency follow-up to the next observing run of the LIGO-Virgo-KAGRA detectors (O4) and analysis of gravitational wave (GW) events using a high-energy cascade dataset, which are produced by electron neutrino charged-current interactions and neutral-current interactions from neutrinos of all flavors.

Thanks to ``dust-to-planet'' simulations (DTPSs), which treat the collisional evolution directly from dust to giant-planet cores in a protoplanetary disk, we showed that giant-planet cores are formed in $\lesssim 10\,$au in several $10^5$ years, because porous pebbles grow into planetesimals via collisions prior to drift in 10 au (Kobayashi & Tanaka 2021, Paper I).However, such porous pebbles are unlikely to reproduce the polarized millimeter wavelength light observed from protoplanetary disks. We thus investigate gas-giant core formation with non-porous pebbles via DTPSs. Even non-porous bodies can grow into planetesimals and massive cores to be gas giants are also formed in several $10^5$ years. The rapid core formation is mainly via the accretion of planetesimals produced by collisional coagulation of pebbles drifting from the outer disk. The formation mechanism is similar to the case with porous pebbles, while core formation occurs in a wider region (5 - 10 au) than that with porous pebbles.

We probe the spectropolarimetric properties of the black-hole binary source 4U 1630$-$47 in the steep power law state. We detect a significant polarization fraction of $\sim$7 % at a polarization angle of $\sim$21 $^\circ$. The $2-12$ keV NICER spectrum can be fitted with a combination of a thermal and a Comptonization component, the latter characterized by a spectral index, $\Gamma \sim$2.1, along with a reflection feature at $\sim$7.0 keV. In the $2-8$ keV band, the degree of polarization of 4U 1630$-$47 in the steep power law state is 4.4 $\sigma$ different from the value previously measured in the high soft state. In the steep power law state, the polarization fraction increases as a function of energy but exhibits an overall drop in each energy band compared to that of the high soft state. We propose that the decrease in the polarization fraction in the steep power law state could be attributed to the presence of a corona. The observed polarization properties in both states can be explained by the self-irradiation of the disk around a Kerr black hole, likely influenced by the frame-dragging effect.

Active Galactic Nuclei (AGN) are powerful astronomical objects with very high luminosities. Theoretical arguments suggest that these objects are capable of accelerating particles to energies of 10$^{20}$ eV. In environments with matter or photon targets, cosmic-ray interactions transpire leading to the production of pionic gamma rays and neutrinos. Since the AGN environment is rich in gas, dust and photons, they are promising candidate sources of high-energy astrophysical neutrinos. While the neutrinos manage to escape, the gamma rays may further interact and cascade down to hard X-rays in environments with sufficiently large photon or gas targets. We have used 12 years of IceCube data to perform a stacked search and a point source search for high-energy neutrino emission from hard X-ray AGN sampled from $\textit{Swift}$-BAT Spectroscopic Survey (BASS) and present the results of these two analyses.

The longstanding search for the cosmological model that best describes the Universe has been made more intriguing since the recent discovery of the Hubble constant, $H_{0}$, tension observed between the value of $H_{0}$ from the Cosmic Microwave Background and from type Ia supernovae (SNe Ia). Hence, the commonly trusted flat $\Lambda$CDM model is under investigation. In this scenario, cosmography is a very powerful technique to investigate the evolution of the Universe without any cosmological assumption, thus revealing tensions between observational data and predictions from cosmological models in a completely model-independent way. We here employ a robust cosmographic technique based on an orthogonal logarithmic polynomial expansion of the luminosity distance to fit quasars (QSOs) alone and QSOs combined with Gamma-Ray Bursts (GRBs), SNe Ia, and Baryon Acoustic Oscillations. To apply QSOs and GRBs as probes we use, respectively, the Risaliti-Lusso relation between ultraviolet and X-ray luminosities and the ``Dainotti GRB 3D relation" among the rest-frame end time of the X-ray plateau emission, its corresponding luminosity, and the peak prompt luminosity. We also correct QSOs and GRBs for selection biases and redshift evolution and we employ both the traditional Gaussian likelihood and the newly discovered best-fit likelihoods for each probe investigated. This comprehensive analysis reveals a strong tension ($> 4 \, \sigma$) between our data sets and the flat $\Lambda$CDM model proving the power of both the cosmographic approach and high-redshift sources, such as QSOs and GRBs, which can probe the Universe at early epochs.

Despite being one of the longest known classes of astrophysical transients, novae continue to present modern surprises. The Fermi-LAT discovered that many if not all novae are GeV gamma ray sources, even though theoretical models had not even considered them as a possible source class. More recently, MAGIC and H.E.S.S. detected TeV gamma rays from a nova. Moreover, there is strong evidence that the gamma rays are produced hadronically, and that the long-studied optical emission by novae is also shock-powered. If this is true, novae should emit a neutrino signal correlated with their gamma-ray and optical signals. We present the first search for neutrinos from novae. Because the neutrino energy spectrum is expected to match the gamma-ray spectrum, we use an IceCube DeepCore event selection focused on GeV-TeV neutrinos. We present results from two searches, one for neutrinos correlated with gamma-ray emission and one for neutrinos correlated with optical emission. The event selection presented here is promising for additional astrophysical transients including gamma-ray bursts and gravitational wave sources.

Neutron stars with very strong magnetic fields are known as magnetars. There are multiple theories that predict magnetars may be able to emit high-energy (HE) neutrinos through hadronic processes by accelerating cosmic rays to high energies. A subclass of magnetars known as soft gamma-ray repeaters (SGRs) can produce giant flares that can result in the production of HE neutrinos. Some magnetars also exhibit bursting activity during which they may emit HE neutrinos. Here we describe our time-integrated search for neutrino emission from magnetars listed in the McGill Online Magnetar Catalog and three newly discovered magnetars SGR 1830-0645, Swift J1555.5-5402, and NGC 253. SGR 1830-0645 and Swift J1555.2-5402 were discovered in 2020 and 2021 respectively by SWIFT after emitting short bursts. A very bright short gamma-ray burst that is believed to be a magnetar giant flare has been localized to NGC 253. We use 14 years of well-reconstructed muon-neutrino candidate events collected by the IceCube Neutrino Observatory to look for significant clustering in the direction of magnetars.

We propose a new method for measuring the spatial density distribution of the stellar halo of the Milky Way. Our method is based on a pairwise statistic of the distribution of stars on the sky, the angular two-point correlation function (ATPCF). The ATPCF utilizes two dimensional data of stars only and is therefore immune to the large uncertainties in the determination of distances to stars. We test our method using mock stellar data coming from various models including the single power-law (SPL) and the broken power-law (BPL) density profiles. We also test the influence of axisymmetric flattening factors using both constant and varying values. We find that the ATPCF is a powerful tool for recovering the spatial distributions of the stellar halos in our models. We apply our method to observational data from the type ab RR Lyrae catalog in the Catalina Survey Data Release 1. In the 3-parameter BPL model, we find that $s_{1}=2.46_{-0.20}^{+0.18}, s_{2}=3.99_{-1.33}^{+0.75}$ and $r_{0}=31.11_{-5.88}^{+7.61}$, which are in good agreement with previous results. We also find that introducing an extra parameter, the radially varying flattening factor, greatly improves our ability to model accurately the observed data distribution. This implies perhaps that the stellar halo of the Milky Way should be regarded as oblate.

We search for additional neutrino emission from the direction of IceCube's highest energy public alert events. We take the arrival direction of 122 events with a high probability of being of astrophysical origin and look for steady and transient emission. We investigate 11 years of reprocessed and recalibrated archival IceCube data. For the steady scenario, we investigate if the potential emission is dominated by a single strong source or by many weaker sources. In contrast, for the transient emission we only search for single sources. In both cases, we find no significant additional neutrino component. Not having observed any significant excess, we constrain the maximal neutrino flux coming from all 122 origin directions (including the high-energy events) to $\Phi_{90\%,~100~\rm{TeV}} = 1.2 \times 10^{-15}$~(TeV cm$^2$ s)$^{-1}$ at 100~TeV, assuming an $E^{-2}$ emission, with 90\% confidence. The most significant transient emission of all 122 investigated regions of interest is the neutrino flare associated with the blazar TXS~0506+056. With the recalibrated data, the flare properties of this work agree with previous results. We fit a Gaussian time profile centered at $\mu_T = 57001 ^{+38}_{-26}$~MJD and with a width of $\sigma_T = 64 ^{+35}_{-10}$~days. The best fit spectral index is $\gamma = 2.3 \pm 0.4$ and we fit a single flavor fluence of $J_{100~\rm{TeV}} = 1.2 ^{+1.1} _{-0.8} \times 10^{-8} $~(TeV~cm$^2$)$^{-1}$. The global p-value for transient emission is $p_{\rm{global}} = 0.156$ and, therefore, compatible with background.

Black Holes (BH) traversing a dark matter cloud made out of a self-interacting scalar soliton are slowed down by two complementary effects. At low subsonic speeds, the BH accretes dark matter and this is the only source of dragging along its motion, if we neglect the backreaction of the cloud self-gravity. The situation changes at larger supersonic speeds where a bow shock in front of the BH is created. This leads to the emergence of an additional friction term, associated with the gravitational and scalar pressure interactions and with the wake behind the moving BH. This is a long distance effect that can be captured by the hydrodynamical regime of the scalar flow far away from the BH. This dynamical friction term has the same form as the celebrated Chandrasekhar collisionless result, albeit with a well-defined Coulomb logarithm. Indeed the infra-red cut-off is naturally provided by the size of the scalar cloud, which is set by the scalar mass and coupling, whilst the ultra-violet behaviour corresponds to the distance from the BH where the velocity field is significantly perturbed by the BH. As a result, supersonic BH are slowed down by both the accretion drag and the dynamical friction. This effect will be potentially detectable by future gravitational wave experiments as it influences the phase of the gravitational wave signal from inspiralling binaries.

The IceCube Neutrino Observatory at the geographic South Pole is, with its surface and in-ice detectors, used for both neutrino and cosmic-ray physics. The surface array, named IceTop, consists of ice-Cherenkov tanks grouped in 81 pairs spanning a 1 km$^2$ area. An enhancement of the surface array, composed of elevated scintillation panels and radio antennas, was designed over the last years in order to increase the scientific capabilities of IceTop. The surface radio antennas, in particular, will be able to reconstruct $X_\mathrm{max}$, an observable widely used to determine the mass composition of cosmic rays. A complete prototype station of this enhanced array was deployed in the Austral summer of 2019/20 at the South Pole. This station comprises three antennas and eight scintillation panels, arranged in a three-arms star shape. The nominal frequency band of the radio antennas is 70 to 350 MHz. In this work, we use a state-of-the-art reconstruction method in which observed events are compared directly to CoREAS simulations to obtain an estimation of the air-shower variables, in particular, energy and $X_\mathrm{max}$. We will show the results in this unique frequency band using the three prototype antennas.

The study of the chemistry of the stellar populations in Globular Clusters (GCs) is a fundamental task to unveil their formation in the high-redshift universe and to reconstruct the build up of our Galaxy. Recently, using metallicity estimates from BP/RP low-resolution Gaia DR3 spectra, Piatti 2023 presented the surprising detection of two distinct stellar populations in the stellar stream of the GC NGC 5904, otherwise considered a mono-metallic system. The presence of these two populations, with [Fe/H]~-1.4 and [Fe/H]~-2.0 dex, was taken as the evidence of a merger origin of the cluster. In this Letter, using the same data set complemented by the new robust metallicity estimates by Andrae et al. 2023b, we carry out a detailed analysis of the metallicity distribution of stars belonging both to the cluster and to its stellar stream, explicitly focusing on the subtle effects of data systematics. We demonstrate that the population at [Fe/H]~-2.0 dex is a data artefact due to error systematics, affecting especially low-magnitude stars. The new higher quality metallicity sample corroborates this finding, and it indicates the presence of only a population of stars with metallicity of [Fe/H]~-1.3 dex, in agreement with previous literature studies. We, therefore, conclude that both NGC 5904 and its stellar stream are mono-metallic systems, and emphasize the need of carefully examining systematic effects in large and complex data bases.

This study presents the first optical spectropolarimetric study of large C-complex asteroids. A total of 64 C-complex asteroids of different subclasses are analyzed using archival polarimetric and reflectance data to refine the link between polarimetric parameters and surface properties of the asteroids. We find a consistent difference in the polarization spectra between asteroids containing phyllosilicates and those without, which correlates with the overall morphology of the reflectance spectrum. They exhibit broad similarities in polarization-phase curves; nonetheless, we observe a gradual enhancement of the negative polarization branch in the ascending order of F-B-T-Ch types, along with an increase in reflectance curvature around 500 nm. Our observations suggest at least for large C-complex asteroids a common mechanism underlies the diversity in optical properties. The observed trends would be explained by the surface composition of the asteroids, particularly optical heterogeneity caused by carbon's varying levels of optical influence, primarily regulated by aqueous alteration of the surfaces.

The study of quasi periodic oscillations (QPOs) plays a vital role in understanding the nature and geometry of the Comptonizing medium around black-hole X-ray binaries. The spectral-state dependence of various types of QPOs (namely A, B, & C) suggests that they could have different origins. The simultaneous presence of different types of QPOs would therefore imply the simultaneous occurrence of different mechanisms. In this work we study the radiative properties of two non-harmonically related QPOs in the black-hole binary GRO J1655--40 detected at the peak of the ultraluminous state during the 2005 outburst of the source. The two QPOs have been previously identified as types B & C, respectively. We jointly fit the phase-lag and rms spectra of the QPOs and the time-averaged spectrum of the source with the time-dependent Comptonization model vkompth to infer the geometry of the media producing the QPOs. The time-averaged spectrum required a hot disk of 2.3 keV and a steep power law with index 2.7, revealing that the source was in an ultraluminous state. The corona that drives the variability of the type-B QPO is smaller in size and has a lower feedback fraction than the one that drives the variability of the type-C QPO. This suggests the simultaneous presence of a horizontally extended corona covering the accretion disk and a vertically elongated jet-like corona that are responsible for the type-B & C QPOs, respectively.

The IceCube Neutrino Observatory has the invaluable capability of continuously monitoring the whole sky. This has affirmed the role of IceCube as a sentinel, providing real-time alerts to the astrophysical community on the detection of high-energy neutrinos and neutrino flares from a variety of astrophysical sources. As a response to the IceCube alerts, different observatories can join forces in the multi-messenger observation of transient events and the characterisation of their astrophysical sources. The 2017 breakthrough identification of blazar TXS 0506+056 as the source of high-energy neutrinos and UHE gamma rays was proof of this strategy. The Gamma-ray Follow-Up (GFU) is the IceCube program for identifying high-energy muon neutrino single events, as well as outstanding neutrino flares from relevant sources and the whole wide universe. While the identification of single high-energy neutrinos is shared on public alert distribution networks, partner Imaging Air Cherenkov Telescopes are sent low-latency alerts following the detection of neutrino flares, for which they have dedicated follow-up programs. I will present an overview of the GFU platform together with new results from the analysis of recorded neutrino flares, after a dozen years of GFU operation and hundreds of alerts being sent.

We use the new QUIJOTE-MFI wide survey (11, 13, 17 and 19 GHz) to produce spectral energy distributions (SEDs), on an angular scale of 1 deg, of the supernova remnants (SNRs) CTB 80, Cygnus Loop, HB 21, CTA 1, Tycho and HB 9. We provide new measurements of the polarized synchrotron radiation in the microwave range. For each SNR, the intensity and polarization SEDs are obtained and modelled by combining QUIJOTE-MFI maps with ancillary data. In intensity, we confirm the curved power law spectra of CTB 80 and HB 21 with a break frequency $\nu_{\rm b}$ at 2.0$^{+1.2}_{-0.5}$ GHz and 5.0$^{+1.2}_{-1.0}$ GHz respectively; and spectral indices respectively below and above the spectral break of $-0.34\pm0.04$ and $-0.86\pm0.5$ for CTB 80, and $-0.24\pm0.07$ and $-0.60\pm0.05$ for HB 21. In addition, we provide upper limits on the Anomalous Microwave Emission (AME), suggesting that the AME contribution is negligible towards these remnants. From a simultaneous intensity and polarization fit, we recover synchrotron spectral indices as flat as $-0.24$, and the whole sample has a mean and scatter of $-0.44\pm0.12$. The polarization fractions have a mean and scatter of $6.1\pm1.9$\%. When combining our results with the measurements from other QUIJOTE studies of SNRs, we find that radio spectral indices are flatter for mature SNRs, and particularly flatter for CTB 80 ($-0.24^{+0.07}_{-0.06}$) and HB 21 ($-0.34^{+0.04}_{-0.03}$). In addition, the evolution of the spectral indices against the SNRs age is modelled with a power-law function, providing an exponent $-0.07\pm0.03$ and amplitude $-0.49\pm0.02$ (normalised at 10 kyr), which are conservative with respect to previous studies of our Galaxy and the Large Magellanic Cloud.

Solar and stellar magnetic patches (i.e., magnetic fluxes that reach the surface from the interior) are believed to be the primary sources of a star's atmospheric conditions. Hence, detecting and identifying these features (also known as magnetic elements) are among the essential topics in the community. Here, we apply the complex network approach to recognize the solar magnetic patches. For this purpose, we use the line-of-sight magnetograms provided by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory. We construct the magnetic network following a specific visibility graph condition between pairs of pixels with opposite polarities and search for possible links between these regions. The complex network approach also provides the ability to rank the patches based on their connectivity (i.e., degree of nodes) and importance (i.e., PageRank). The use of the developed algorithm in the identification of magnetic patches is examined by tracking the features in consecutive frames, as well as making a comparison with the other approaches to identification. We find that this method could conveniently identify features regardless of their sizes. For small-scale (one or two pixels) features, we estimate the average of 8% false-positive and 1% false-negative errors.

The collected data of IceCube, a cubic kilometre neutrino detector array in the Antarctic ice, reveal a diffuse flux of astrophysical neutrinos. The extragalactic sources of the majority of these neutrinos however have yet to be discovered. Tidal Disruption Events (TDEs), disruption outbursts from black holes that accrete at an enhanced rate, are candidates for being the sources of extragalactic, high-energy neutrinos. Stein et al. (2021) and Reusch et al. (2022) have reported the coincidence of two likely TDEs from supermassive black holes and public IceCube neutrino events (alerts). Further work by van Velzen et al. (2021) identified a third event in coincidence with a high-energy neutrino alert and a $3.7 \sigma$ correlation between a broader set of similar TDE-like flares and IceCube alerts. We conducted a stacking analysis with a 29-flare subset of the TDE-like flares tested by van Velzen et al. This work was done with neutrinos with energies above $\mathcal{O}(100)$ GeV. The resulting p-value of 0.45 is consistent with background. In this contribution, I will discuss the results of the stacking analysis, as well as the impact of using different reconstruction algorithms on the three correlated realtime alerts.

The thermal instability of accretion disks is widely used to explain the activity of cataclysmic variables, but its development in protoplanetary disks has been studied in less detail. We present a semi-analytical stationary model for calculating the midplane temperature of a gas and dust disk around a young star. The model takes into account gas and dust opacities, as well as the evaporation of dust at temperatures above 1000 K. Using this model, we calculate the midplane temperature distributions of the disk under various assumptions about the source of opacity and the presence of dust. We show that when all considered processes are taken into account, the heat balance equation in the region r<1 au has multiple temperature solutions. Thus, the conditions for thermal instability are met in this region. To illustrate the possible influence of instability on the accretion state in a protoplanetary disk, we consider a viscous disk model with alpha parameterization of turbulent viscosity. We show that in such a model the disk evolution is non-stationary, with alternating phases of accumulation of matter in the inner disk and its rapid accretion onto the star, leading to an episodic accretion pattern. These results indicate that this instability needs to be taken into account in evolutionary models of protoplanetary disks.

Recently, the pulsar timing array (PTA) collaborations have reported the evidence for a stochastic gravitational wave background (SGWB) at nano-Hertz band. The spectrum of inflationary gravitational wave (IGW) is unknown, which might exhibit different power law at different frequency-bands, thus if the PTA signal is primordial, it will be significant to explore the underlying implications of current PTA and CMB data on IGW. In this paper, we perform a joint Markov Chain Monte Carlo analysis for a broken power-law spectrum of IGW with the NANOGrav 15-year and BICEP/Keck 2018 data. It is found that though the bestfit spectral tilt of IGW at PTA band is $n^\text{PTA}_\text{T} =2.42^{+0.32}_{-0.91}$, at CMB band the bestfit is $n^\text{CMB}_\text{T} =0.55^{+0.37}_{-0.10}$ while a detectable amplitude of $r$ with $n^\text{CMB}_\text{T} \simeq 0$ is still compatible. The implication of our results for inflation is also discussed.

Faint galaxies are theorised to have played a major role in reionising the Universe. Their properties as well as the Lyman-{\alpha} emitter fraction, could provide useful insight into this epoch. We use four galaxy clusters from the Lensed Lyman-alpha MUSE Arcs Sample (LLAMAS) which also have deep HST photometry to select a population of intrinsically faint Lyman Break Galaxies (LBGs) and Lyman-alpha Emitters (LAEs). We study the interrelation of these two populations, their properties, and the fraction of LBGs that display Lyman-alpha emission. The use of lensing clusters allows us to access an intrinsically faint population, the largest sample collected for this purpose: 263 LAEs and 972 LBGs between redshifts of 2.9 and 6.7, Lyman-alpha luminosities between 39.5 < log(L)(erg/s) < 42 and absolute UV magnitudes between -22 < M1500 < -12. We find a redshift evolution of the Lyman-alpha emitter fraction in line with past results, with diminished values above z = 6, taken to signify an increasingly neutral intervening IGM. Inspecting this redshift evolution with different limits on Lyman-alpha equivalent width (EW) and M1500 we find that the Lyman-alpha emitter fraction for the UV-brighter half of our sample is higher than the fraction for the UV-fainter half, a difference which increases at higher redshift. This is a surprising result and can be interpreted as a population of low Lyman-alpha EW, UV-bright galaxies situated in reionised bubbles. This result is especially interesting in the context of similar, UV-bright, low Lyman-alpha EW objects recently detected around the epoch of reionisation. We extend to intrinsically fainter objects the previously observed trends of LAEs among LBGs as galaxies with high star-formation rates and low dust content, as well as the strongest LAEs having in general fainter UV magnitudes and steeper UV slopes.

The experiment of exo-ecosystem and the exploration of extraterrestrial habitability aims to explore the adaptation of terrestrial life in space conditions for the manned space program and the future interstellar migration, which shows great scientific significance and public interests. By our knowledge the early life on Earth, archaea and extremophile have the ability to adapt to extreme environmental conditions and can potentially habitat in extraterrestrial environments. Here we proposed a design and framework for the experiment on exo-ecosystem and extraterrestrial habitability. The conceptual approach involves building an ecosystem based on archaea and extremophiles in a simulated extraterrestrial environment, with a focus on assessing the exobiological potential and adaptability of terrestrial life forms in such conditions through controlled experiments. Specifically, we introduce the Chinese Exo-Ecosystem Space Experiment (CHEESE), which investigates the survivability and potential for sustained growth, reproduction, and ecological interactions of methanogens under simulated Mars and Moon environments using the China Space Station (CSS) as a platform. We highlight that the space station provides unique yet relatively comprehensive conditions for simulating extraterrestrial environments. In conclusion, space experiments involving exo-ecosystems could pave the way for long-term human habitation in space, ensuring our ability to sustain colonies and settlements beyond Earth while minimizing our ecological impact on celestial bodies.

Recent upper bounds from the Hydrogen Epoch of Reionization Array (HERA) on the cosmological 21-cm power spectrum at redshifts $z \approx 8, 10$, have been used to constrain $L_{\rm X<2 \, keV}/{\rm SFR}$, the soft-band X-ray luminosity measured per unit star formation rate (SFR), strongly disfavoring values lower than $\approx 10^{39.5} \, {\rm erg} \;{\rm s}^{-1} \;{\rm M}_{\odot}^{-1} \;{\rm yr}$ . In this work, we first reproduce the bounds on $L_{\rm X<2 \, keV}/{\rm SFR}$ and other parameters using a pipeline that combines machine learning emulators for the power spectra and the intergalactic medium characteristics, together with a standard Markov chain Monte Carlo parameter fit. We then use this approach when including molecular cooling galaxies that host PopIII stars in the cosmic dawn 21-cm signal, and show that lower values of $L_{\rm X<2 \, keV}/{\rm SFR}$ are hence no longer strongly disfavored. The revised HERA bound does not require high-redshift X-ray sources to be significantly more luminous than high-mass X-ray binaries observed at low redshift.

India has been actively involved in the follow-up observations of optical afterglows of gamma-ray bursts (GRBs) for more than two decades, using the country's meter-class facilities such as the 1.04 m Sampurnanand Telescope, 1.3 m Devasthal Fast Optical Telescope, 2.01 m Himalayan Chandra Telescope along with many others in the country, utilizing the longitudinal advantage of the place. However, since 2016, Indian astronomers have embarked on a new era of exploration by utilizing the country's largest optical telescope, the 3.6 m Devasthal Optical Telescope (DOT) at the Devasthal Observatory of ARIES Nainital. This unique telescope has opened up exciting opportunities for transient study. Starting from the installation itself, the DOT has been actively performing the target of opportunity (ToO) observations, leading to many interesting discoveries. Notable achievements include the contributions towards the discovery of long GRB 211211A arising from a binary merger, the discovery of the most delayed optical flare from GRB 210204A along with the very faint optical afterglow (fainter than 25 mag in g-band) of GRB 200412B. We also successfully observed the optical counterpart of the very-high-energy (VHE) detected burst GRB 201015A using DOT. Additionally, DOT has been used for follow-up observations of dark and orphan afterglows, along with the observations of host galaxies associated with peculiar GRBs. More recently, DOT's near-IR follow-up capabilities helped us to detect the first near-IR counterpart (GRB 230409B) using an Indian telescope. In this work, we summarise the recent discoveries and observations of GRBs using the 3.6 m DOT, highlighting the significant contributions in revealing the mysteries of these cosmic transients.

Neutron star high mass X-ray binaries with superorbital modulations in luminosity host warped inner accretion disks that occult the neutron star during precession. In SMC X-1, the instability in the warped disk geometry causes superorbital period "excursions:" times of instability when the superorbital period decreases from its typical value of 55 days to $\sim$40 days. Disk instability makes SMC X-1 an ideal system in which to investigate the effects of variable disk geometry on the inner accretion flow. Using the high resolution spectral and timing capabilities of the Neutron Star Interior Composition Explorer (NICER) we examined the high state of four different superorbital cycles of SMC X-1 to search forchanges in spectral shape and connections to the unstable disk geometry. We performed pulse phase-averaged and phase-resolved spectroscopy to closely compare the changes in spectral shape and any cycle-to-cycle variations. While some parameters including the photon index and absorbing column density show slight variations with superorbital phase, these changes are most evident during the intermediate state of the supeorbital cycle. Few spectral changes are observed within the high state of the superorbital cycle, possibly indicating the disk instability does not significantly change SMC X-1's accretion process.

Supermassive black holes (SMBHs) power active galactic nuclei (AGN). The vicinity of the SMBH has long been proposed as the potential site of particle acceleration and neutrino production. Recently, IceCube reported evidence of neutrino emission from the Seyfert II galaxy NGC 1068. The absence of a matching flux of TeV gamma rays suggests that neutrinos are produced where gamma rays can efficiently get attenuated, for example, in the hot coronal environment near the SMBH at the core of the AGN. Here, we select the intrinsically brightest (in X-ray) Seyfert galaxies in the Southern Sky from the BAT AGN Spectroscopic Survey (BASS) and search for associated neutrinos using starting track events in IceCube. In addition to the standard power law flux assumption, we leverage a dedicated disc-corona model of neutrino production in such an environment to improve the discovery potential of the search. In this contribution, we report on the expected performance of our searches for neutrinos from these Seyfert galaxies.

This paper presents a comprehensive analysis of the Galactic SNR Kes 17 (G304.6+0.1) with focus on its radio synchrotron emission, environs, and the factors contributing to the observed gamma rays. The firstly-obtained integrated radio continuum spectrum from 88 to 8800 MHz yields an index alpha = -0.488 +/- 0.023 (S_nu $\propto$ nu^alpha), indicative of a linear particle acceleration process at the shock front. Accounting for the SNR radio shell size, the distribution of atomic hydrogen (n_H ~ 10 cm^-3), and assuming the SNR is in the Sedov-Taylor stage of its evolution, we estimate Kes 17 to be roughly 11 kyr. From 12CO and 13CO (J=1-0) emission-line data as a proxy for molecular hydrogen we provided the first evidence that the eastern shell of Kes 17 is engulfing a molecular enhancement, with 4.2 x 10^4 M_sun and n ~ 300 cm^-3. Towards the western boundary of Kes 17 there are not CO signatures above 3 sigma, despite previously reported infrared observations have revealed shocked molecular gas at that location. This suggests the existence of a CO-dark interacting molecular gas, a phenomenon also recorded in other Galactic SNRs (e.g. CTB 37A and RX J1713.7-3946). Additionally, by analysing ~14.5 yr of data from Fermi-LAT, we determined a power-law photon index in the 0.3-300 GeV range of Gamma = 2.39 +/- 0.04^+0.063_-0.114 (+/-stat +/-syst) in agreement with prior studies. The energy flux turns out to be (2.98 +/- 0.14) x 10^-11 erg cm-2 s-1 implying a luminosity (2.22 +/- 0.45) x 10^35 erg s-1 at ~8 kpc. Finally, we successfully modelled the multiwavelength SED by incorporating the improved radio synchrotron spectrum and the new gamma-ray measurements. Our analysis indicates that the observed GeV flux most likely originates from the interaction of Kes 17 with western ''dark'' CO zone with a proton density n_p ~ 400 cm-3.

Under the assumption that jets explode all core collapse supernovae (CCSNe) I classify 13 CCSN remnants (CCSNRs) into five groups according to their morphology as shaped by jets, and attribute the classes to the specific angular momentum of the pre-collapse core. Point-symmetry (1 CCSNR): According to the jittering jets explosion mechanism (JJEM) when the pre-collapse core rotates very slowly the newly born neutron star (NS) launches tens of jet-pairs in all directions. The last several jet-pairs might leave an imprint of several pairs of ears, i.e., a point-symmetric morphology. One pair of ears (7 CCSNRs): More rapidly rotating cores might force the last pair of jets to be long-lived and shape one pair of jet-inflated ears that dominate the morphology. S-shaped (1 CCSNR): The accretion disk might precess, leading to an S-shaped morphology. Barrel-shaped (3 CCSNRs): Even more rapidly rotating pre-collapse cores might result in a final energetic pair of jets that clear the region along the axis of the pre-collapse core rotation and form a barrel-shaped morphology. Elongated (1 CCSNR): Very rapidly rotating pre-collapse core force all jets to be along the same axis such that the jets are inefficient in expelling mass from the equatorial plane and the long-lasting accretion process turns the NS into a black hole (BH). The two new results of this study are the classification of CCSNRs into five classes based on jet-shaped morphological features, and the attribution of the morphological classes mainly to the pre-collapse core rotation in the frame of the JJEM.

Ultra-high energy cosmic rays (UHECRs) beyond the Greisen-Zatsepin-Kuzmin (GZK) cut-off provide us with a unique opportunity to understand the universe at extreme energies. Secondary GZK photons and GZK neutrinos associated with the same interaction are indeed interconnected and render access to multi-messenger analysis of UHECRs. The GZK photon flux is heavily attenuated due to the interaction with Cosmic Microwave Background (CMB) and the Extra-galactic Radio Background (ERB). The present estimate of the ERB comprising of several model uncertainties together with the ARCADE2 radio excess results in large propagation uncertainties in the GZK photon flux. On the other hand, the weakly interacting GZK neutrino flux is unaffected by these propagation effects. In this work, we make an updated estimate of the GZK photon and GZK neutrino fluxes considering a wide variation of both the production and propagation properties of the UHECR like, the spectral index, the cut-off energy of the primary spectrum, the distribution of sources and the uncertainties in the ERB estimation. We explore the detection prospects of the GZK fluxes with various present and upcoming UHECR and UHE neutrino detectors such as Auger, TA, GRAND, ANITA, ARA, IceCube and IceCube-Gen2. The predicted fluxes are found to be beyond the reach of the current detectors. In future, proposed IceCube-Gen2, AUGER upgrade and GRAND experiments will have the sensitivity to the predicted GZK photon and GZK neutrino fluxes. Such detection can put constraints on the UHECR source properties and the propagation effects due to the ERB. We also propose an indirect lower limit on the GZK photon flux using the neutrino-photon connection for any future detection of GZK neutrinos by the IceCube-Gen2 detector. We find this limit to be consistent with our GZK flux predictions.

Fullerenes, including C60, C70, and C60+, are widespread in space through their characteristic infrared vibrational features (C60+ also reveals its presence in the interstellar medium through its electronic transitions) and offer great insights into the carbon chemistry and stellar evolution. The potential existence of fullerene-related species in space has long been speculated and recently put forward by a set of laboratory experiments of C60+, C60H+, C60O+, C60OH+, C70H+, and [C60-Metal]+ complexes. The advent of the James Webb Space Telescope (JWST) provides a unique opportunity to search for these fullerene-related species in space. To facilitate JWST search, analysis, and interpretation, an accurate knowledge of their vibrational properties is essential. Here, we compile a VibFullerene database and conduct a systematic theoretical study on those species. We derive a set of range-specific scaling factors for vibrational frequencies, to account for the deficiency of density functional theory calculations in predicting the accurate frequencies. Scaling factors with low root-mean-square and median errors for the frequencies are obtained, and their performance is evaluated, from which the best-performing methods are recommended for calculating the infrared spectra of fullerene derivatives which balance the accuracy and computational cost. Finally, the recommended vibrational frequencies and intensities of fullerene derivatives are presented for future JWST detection.

Previous studies of cometary impacts in the outer Solar System used the spatial distribution of ecliptic comets (ECs) from dynamical models that assumed ECs began on low-inclination orbits (<5 deg) in the Kuiper belt. In reality, the source population of ECs - the trans-Neptunian scattered disk - has orbital inclinations reaching up to ~30 deg. In Nesvorny et al. (2017), we developed a new dynamical model of ECs by following comets as they evolved from the scattered disk to the inner Solar System. The model was absolutely calibrated from the population of Centaurs and active ECs. Here we use our EC model to determine the steady-state impact flux of cometary/Centaur impactors on Jupiter, Saturn, Uranus, and their moons. Relative to previous work (Zahnle et al. 2003), we find slightly higher impact probabilities on the outer moons and lower impact probabilities on the inner moons. The impact probabilities are smaller when comet disruption is accounted for. The results provide a modern framework for the interpretation of the cratering record in the outer Solar System.

We present a novel analytical approach to study the cross-correlations between the Integrated Sachs Wolfe--Rees Sciama (ISWRS) effects and large-scale structure tracers in the presence of massive neutrinos. Our method has been validated against large N-body simulations with a massive neutrino particle component, namely the DEMNUni suite. We investigate the impact of different neutrino masses on the cross-correlations between ISWRS and both Cosmic Microwave Background (CMB) lensing and galaxies. We show that the position of the sign inversion due to nonlinear effects is strongly related to the neutrino mass. While such nonlinear cross-correlation signals may not be able alone to constrain the neutrino mass, our approach paves the way for future studies to detect the amplitude of these cross-spectra on small scales, and to explore the combined impact of dark energy and neutrino mass from future galaxy surveys and CMB experiments.

Based on the results of a previous analysis of the Markovian master equation for the irreversible evolution of an open system embedded in de Sitter space, we include in the cosmological Friedmann equations a contribution from the presence of a physical bath at temperature $T_{\rm dS} = h / 2 \pi$, where $h$ is the Hubble parameter. We show that this provides a mechanism for the irreversible relaxation of the cosmological constant and a graceful exit to inflation, without need for subsequent reheating. Thermal particle production during inflation gives adiabatic, Gaussian, and approximately scale-invariant cosmological perturbations. We thus obtain the main features of inflation without any inflaton potential.

We study the morphology of the 511 keV signal that could be produced by exciting dark matter (XDM) in the Milky Way. In this model, collisions between dark matter particles excite the dark matter to a state that can then decay back to the ground state, releasing an electron-positron pair. These electrons and positrons would then annihilate, producing 511 keV photons that could explain the 511 keV signal seen by INTEGRAL at the Galactic Center. We compare the resulting flux with the most recent INTEGRAL data, performing the first full statistical analysis of the exciting dark matter model. We focus on exciting dark matter in the mass and cross section ranges 100 GeV $\lesssim m_{\chi} \lesssim$ 3 TeV and $10^{-19}$ cm$^3$ s$^{-1} \lesssim \langle \sigma v \rangle \lesssim 10^{-16}$ cm$^3$ s$^{-1}$. We show that exciting dark matter can provide a significantly better fit than the simpler case of annihilating dark matter, with $\Delta\chi^2 > 16$ for all but one of the density profiles we consider.

When hypothetical neutrino secret interactions ($\nu$SI) are large, they form a fluid in a supernova (SN) core, flow out with sonic speed, and stream away as a fireball. For the first time, we solve all steps, systematically using relativistic hydrodynamics, although a simplified source model. The impact on SN physics and the neutrino signal is remarkably small. Even for complete thermalization within the fireball, the observable spectrum barely changes. Small energy-transfer modifications may affect the neutrino-driven explosion mechanism, but on present evidence are not ruled in or out. One potentially large effect beyond our study is quick deleptonization if $\nu$SI violate lepton number.

Using direct numerical simulations, we show that a chiral magnetic anomaly can be produced just from initial spatially inhomogeneous fluctuations of the chemical potential, provided there is a small mean magnetic flux through the domain. The produced chiral asymmetry in the number densities of left- and right-handed fermions causes a chiral magnetic effect, the excitation of a chiral dynamo instability, the production of magnetically driven turbulence, and the generation of a large-scale magnetic field via the magnetic $\alpha$ effect from fluctuations of current helicity.

Neutrino-neutrino scattering could have a large secret component that would turn neutrinos within a supernova (SN) core into a self-coupled fluid. Neutrino transport within the SN core, emission from its surface, expansion into space, and the flux spectrum and time structure at Earth might all be affected. We examine these questions from first principles. First, diffusive transport differs only by a modified spectral average of the interaction rate. We next study the fluid energy transfer between a hot and a cold blackbody surface in plane-parallel and spherical geometry. The key element is the decoupling process within the radiating bodies, which themselves are taken to be isothermal. For a zero-temperature cold plate, mimicking radiation into free space by the hot plate, the energy flux is 3--4\% smaller than the usual Stefan-Boltzmann Law. The fluid energy density just outside the hot plate is numerically 0.70 of the standard case, the outflow velocity is the speed of sound $v_s=c/\sqrt{3}$, conspiring to a nearly unchanged energy flux. Our results provide the crucial boundary condition for the expansion of the self-interacting fluid into space, assuming an isothermal neutrino sphere. We also derive a dynamical solution, assuming the emission suddenly begins at some instant. A neutrino front expands in space with luminal speed, whereas the outflow velocity at the radiating surface asymptotically approaches $v_s$ from above. Asymptotically, one thus recovers the steady-state emission found in the two-plate model. A sudden end to neutrino emission leads to a fireball with constant thickness equal to the duration of neutrino emission.

We study anisotropic (patchy) screening induced by the resonant conversion of cosmic microwave background (CMB) photons into dark-sector massive vector bosons (dark photons) as they cross non-linear large scale structure (LSS). Resonant conversion takes place through the kinetic mixing of the photon with the dark photon, one of the simplest low energy extensions to the Standard Model. In the early Universe, resonant conversion can occur when the photon plasma mass, obtained as the photon propagates through the ionized interstellar and intergalactic media, matches the dark photon mass. After the epoch of reionization, resonant conversion occurs mainly in the ionized gas that occupies virialized dark matter halos, for a range of dark photon masses between $10^{-13} {\rm \; eV} \lesssim m_{{\rm A^{\prime}}} \lesssim 10^{-11} {\rm \; eV}$. This leads to new CMB anisotropies that are correlated with LSS, which we refer to as patchy dark screening, in analogy with anisotropies from Thomson screening. Its unique frequency dependence allows it to be distinguished from the blackbody CMB. In this paper, we use a halo model approach to predict the imprint of dark screening on the CMB temperature and polarization anisotropies, as well as their correlation with LSS. We then examine the two- and three-point correlation functions of the dark-screened CMB, as well as correlation functions between CMB and LSS observables, to project the sensitivity of future measurements to the kinetic mixing parameter and dark photon mass. We demonstrate that an analysis with existing CMB data can improve upon current constraints on the kinetic mixing parameter by two orders of magnitude with the two-point correlation functions, while data from upcoming CMB experiments and LSS surveys can further improve the reach by up to two orders of magnitude with two- and three-point correlation functions.

Gravitational wave astronomy pipelines rely on template waveform models for searches and parameter estimation purposes. For coalescing binary neutron stars (BNS), such models need to accurately reproduce numerical relativity (NR) up to merger, in order to provide robust estimate of the stars' equation of state - dependent parameters. In this work we present an improved version of the Effective One Body (EOB) model $\tt TEOBResumS$ for gravitational waves from BNS systems. Building upon recent post-Newtonian calculations, we include subleading order tidal terms in the waveform multipoles and EOB metric potentials, as well as add up to 5.5PN terms in the gyro-gravitomagnetic functions entering the spin-orbit sector of the model. In order to further improve the EOB-NR agreement in the last few orbital cycles before merger, we introduce next-to-quasicircular corrections in the waveform -- informed by a large number of BNS NR simulations -- and introduce a new NR-informed parameter entering the tidal sector of our conservative dynamics. The performance of our model is then validated against 14 new eccentricity reduced simulations of unequal mass, spinning binaries with varying equation of state. A time-domain phasing analysis and mismatch computations demonstrate that the new model overall improves over the previous version of $\tt TEOBResumS$. Finally, we present a closed-form frequency domain representation of the (tidal) amplitude and phase of the new model. This representation accounts for mass-ratio, aligned spin and (resummed) spin-quadrupole effects in the tidal phase and -- within the calibration region -- it is faithful to the original model.

This work studies the cosmology of $\chi^{3/2}$-MOND gravity by Bernal et. al. (2011). This theory is a modification to Einstein's General Relativity (GR) that uses a dimensionless curvature scalar $\chi$ by rescaling the Ricci scalar $R$ by some characteristic length scale $L_M$, as well as a set of modified field equations that follows from a $3/2$-power Lagrangian. The characteristic length scale is assumed to be built from the universal constants of the theory and the parameters of the system in question. In the weak field limit, this theory recovers Milgrom's (1983) Modified Newtonian Dynamics (MOND). MOND is a proposal that corrects Newtonian gravitational laws below an acceleration threshold $a_0\approx1.2\times{10}^{-10}m/s^2$ to explain the anomalous flattening of galactic rotation curves without imposing any dark matter components. In the cosmological case, this work asserts that the characteristic length scale is of the order $c^2/a_0$. This specific value is motivated in two ways: (1) it is shown that this scale defines a convergence of GR and MOND at some critical mass (with this as the corresponding length); (2) this length scale is shown to be an extremal value of $L_M$ independent of the mass parameter. The established length scale is then used in the case of cosmology; the FLRW metric is plugged in into the modified field equations and the two modified Friedmann equations are derived incorporating the MOND effects by a manifest appearance of the constant $a_0$.

We perform three-dimensional simulations of homogeneous and inhomogeneous cosmologies via the coupling of a numerical relativity code for spacetime evolution and smoothed particle hydrodynamics (SPH) code. Evolution of a flat dust and radiation dominated Friedmann-Lema\^itre-Roberston-Walker (FLRW) spacetime shows an agreement of exact solutions with residuals on the order $10^{-6}$ and $10^{-3}$ respectively, even at low grid resolutions. We demonstrate evolution of linear perturbations of density, velocity and metric quantities to the FLRW with residuals of only $10^{-2}$ compared to exact solutions. Finally, we demonstrate the evolution of non-linear perturbations of the metric past shell-crossing, such that dark matter halo formation is possible. We show that numerical relativistic smoothed particle hydrodynamics is a viable method for understanding non-linear effects in cosmology.

The central speed of sound (SS) measures the stiffness of the Equation of State (EOS) of superdense neutron star (NS) matter. Its variations with density and radial coordinate in NSs in conventional analyses often suffer from uncertainties of the specific nuclear EOSs used. Using the central SS and NS mass/radius scaling obtained from solving perturbatively the scaled Tolman-Oppenheimer-Volkoff (TOV) equations, we study the variations of SS, trace anomaly and several closely related properties of NSs in an EOS-model independent manner. We find that the SS increases with the reduced central pressure $\widehat{P}_{\rm{c}}\equiv P_{\rm{c}}/\varepsilon_{\rm{c}}$ (scaled by the central energy density $\varepsilon_{\rm{c}}$), and the conformal bound for SS is violated for NSs with masses higher than about 1.9M$_{\odot}$. The ratio $P/\varepsilon$ is upper bounded as $P/\varepsilon\lesssim0.374$ around the centers of stable NSs. We demonstrate that it is an intrinsic property of strong-field gravity and is more relevant than the perturbative QCD bound on it. While a sharp phase transition at high densities characterized by a sudden vanishing of SS in cores of massive NSs are basically excluded, the probability for a continuous crossover signaled by a peaked radial profile of SS is found to be enhanced as $\widehat{P}_{\rm{c}}$ decreases, implying it likely happens near the centers of massive NSs. Moreover, a new and more stringent causality boundary as $R_{\max}/\rm{km}\gtrsim 4.73M_{\rm{NS}}^{\max}/M_{\odot}+1.14$ for NS M-R curve is found to be excellently consistent with observational data on NS masses and radii. Furthermore, new constraints on the ultimate energy density and pressure allowed in NSs before collapsing into black holes are obtained and compared with earlier predictions in the literature.

The emergence of oxygenic photosynthesis was a major event in Earth's evolutionary history and was facilitated by chlorophylls (a major category of photopigments). The accurate modelling of photopigments is important to understand the characteristics of putative extraterrestrial life and its spectral signatures (detectable by future telescopes). In this paper, we perform a detailed assessment of various time-dependent density-functional theory (TD-DFT) methods for predicting the absorption spectra of chlorophyll a, with particular emphasis on modern low-cost approximations. We also investigate a potential extraterrestrial photopigment called phot0 and demonstrate that the electronegativity of the metal ion may exert a direct influence on the locations of the absorption peaks, with higher electronegativity inducing blue-shifting and vice-versa. Based on these calculations, we established that global-hybrid approximations with a moderate percentage of exact exchange -- such as M06 and PW6B95 -- are the most appropriate compromise between cost and accuracy for the computational characterization of photopigments of astrobiological interest. We conclude with a brief assessment of the implications and avenues for future research.

The detection of ultra high energy gamma-rays provides an opportunity to explore the existence of ALPs at the multi-hundred TeV and PeV energy scales. We discover that we can employ analytic methods to investigate the propagation of photon-ALP beams in scenarios where the energy of photons $\omega \geq 100$ TeV. Our analytical calculations uncover the presence of two distinct modes of photon propagation resulting from the interplay between ALP-photon mixing and attenuation effects. Next, we analyze observable quantities such as the degree of polarization and survival probability in these two modes. We determine the conditions under which a significant polarization effect can be observed and identify the corresponding survival probability. Finally, we extend our analytic methods to cover the energy range of $10^{-3}$ to $10^4$ GeV and analyze the influence of ALPs on the experimental signals.