Papers for Friday, Nov 17 2023

The shapes of galaxies, in particular their outer regions, are important guideposts to their formation and evolution. Here we report on the discovery of strongly box-shaped morphologies of the, otherwise well-studied, elliptical and lenticular galaxies NGC 720 and NGC 2768 from deep imaging. The boxiness is strongly manifested in the shape parameter $A_4/a$ of $-0.04$ in both objects, and also significant center shifts of the isophotes of $\sim$ 2--4 kpc are seen. One reason for such asymmetries commonly stated in the literature is a merger origin, although the number of such cases is still sparse and the exact properties of the individual boxy objects is highly diverse. Indeed, for NGC 2768, we identify a progenitor candidate (dubbed Pelops) in the residual images, which appears to be a dwarf satellite that is currently merging with NGC 2768. At its absolute magnitude of M$_r$ of $-$12.2 mag, the corresponding Sersic radius of 2.4 kpc is more extended than those of typical dwarf galaxies from the literature. However, systematically larger radii are known to occur in systems that are in tidal disruption. This finding is bolstered by the presence of a tentative tidal stream feature on archival GALEX data. Finally, further structures in the fascinating host galaxy comprise rich dust lanes and a vestigial X-shaped bulge component.

The main purpose of this work is to investigate the properties of the non-thermal emission in the interacting clusters pairs Abell 0399-Abell 0401 and Abell 21-PSZ2 G114.9, found in an interacting state. In both cases their connection along a filament is supported by SZ effect detected by the Planck satellite and, in the special case of Abell 0399-Abell 0401, the presence of a radio bridge has been already confirmed by LOFAR observations at 140MHz. Here, we analyse new high sensitivity wideband (250-500MHz) uGMRT data of these two systems and describe an injection procedure to place limits on the spectrum of Abell 0399-Abell 0401 and on the radio emission between Abell 21-PSZ2 G114.9. For the A399-A401 pair, we are able to constrain the steep spectral index of the bridge emission to be alpha>2.2 with a 95% confidence level between 140MHz and 400MHz. For the A21-PSZ2 G114.9 pair, we are able to place an upper limit on the flux density of the bridge emission with two different methods, finding at the central frequency of 383MHz a conservative value of fu_1<260mJy at 95% confidence level, and a lower value of fu_2<125mJy at 80% confidence level, based on visual inspection and a morphological criterion. Our work provides a constraint on the spectrum in the bridge A399-A401 which disfavours shock-acceleration as the main mechanism for the radio emission.

There has been a discussion for many years on whether the disc in the Milky Way extends down to low metallicity. We aim to address the question by employing a large sample of giant stars with radial velocities and homogeneous metallicities based on the Gaia DR3 XP spectra. We study the 3D velocity distribution of stars in various metallicity ranges, including the very-metal poor regime (VMP, [M/H] $<-2.0$). We find that a clear disc population starts to emerge only around [M/H] $\sim -1.3$, and is not visible for [M/H] $<-1.6$. Using Gaussian Mixture Modeling (GMM), we show that there are two halo populations in the VMP regime: one stationary and one with a net prograde rotation of $\sim80\,\mathrm{km/s}$. In this low-metallicity range, we are able to place constraints on the contribution of a rotation-supported disc sub-population to a maximum of $\sim 3$\%. We compare our results to previous claims of discy VMP stars in both observations and simulations and find that having a prograde halo component could explain most of these.

We study, analytically and numerically, the structure and evolution of relativistic jetted blast waves that propagate in uniform media, such as those that generate afterglows of gamma-ray bursts. Similar to previous studies, we find that the evolution can be divided into two parts: (i) a pre-spreading phase, in which the jet core angle is roughly constant, $\theta_{c,0}$, and the shock Lorentz factor along the axis, $\Gamma_a$, evolves as a part of the Blandford-Mckee solution, and (ii) a spreading phase, in which $\Gamma_a$ drops exponentially with the radius and the core angle, $\theta_c$, grows rapidly. Nevertheless, the jet remains collimated during the relativistic phase, where $\theta_c(\Gamma_a\beta_a=1)\simeq 0.4\theta_{c,0}^{1/3}$. The transition between the phases takes place when $\Gamma_a\simeq 0.2\theta_{c,0}^{-1}$. We find that the "wings" of jets with initial "narrow" structure ($\frac{d \log\,E_{iso}}{d\log\,\theta}<-3$ outside of the core, where $E_{iso}$ is isotropic equivalent energy), start evolving during the pre-spreading phase. By the spreading phase these jets evolve to a self-similar profile, which is independent of the initial structure, where in the wings $\Gamma(\theta)\propto\theta^{-1.5}$ and $E_{iso}(\theta)\propto \theta^{-2.6}$. Jets with initial "wide" structure roughly keep their initial profile during their entire evolution. We provide analytic description of the jet lateral profile evolution for a range of initial structures, as well as the evolution of $\Gamma_a$ and $\theta_c$. For off-axis GRBs, we present a relation between the initial jet structure and the light curve rising phase. Applying our model to GW170817, we find that initially the jet had $\theta_{c,0}=0.4-4.5~\deg$ and wings which are consistent with $E_{iso} \propto \theta^{-3}-\theta^{-4}$.

A convective dynamo operating during the crystallization of white dwarfs is one of the promising channels to produce their observed strong magnetic fields. Although the magnitude of the fields generated by crystallization dynamos is uncertain, their timing may serve as an orthogonal test of this channel's contribution. The carbon-oxygen cores of $M\approx 0.5-1.0\,{\rm M}_\odot$ white dwarfs begin to crystallize at an age $t_{\rm cryst}\propto M^{-5/3}$, but the magnetic field is initially trapped in the convection zone - deep inside the CO core. Only once a mass of $m_{\rm cryst}$ has crystallized, the convection zone approaches the white dwarf's helium layer, such that the magnetic diffusion time through the envelope shortens sufficiently for the field to break out to the surface, where it can be observed. This breakout time is longer than $t_{\rm cryst}$ by a few Gyr, scaling as $t_{\rm break}\propto t_{\rm cryst}f^{-1/2}$, where $f\equiv 1-m_{\rm cryst}/M$ depends on the white dwarf's initial C/O profile before crystallization. The first appearance of strong magnetic fields $B\gtrsim 1\textrm{ MG}$ in volume-limited samples approximately coincides with our numerically computed $t_{\rm break}(M)$ - potentially signalling crystallization dynamos as a dominant magnetization channel. However, some observed magnetic white dwarfs are slightly younger, challenging this scenario. The dependence of the breakout process on the white dwarf's C/O profile implies that magnetism may probe the CO phase diagram, as well as uncertainties during the core helium burning phase in the white dwarf's progenitor, such as the $^{12}{\rm C}(\alpha,\gamma)^{16}{\rm O}$ nuclear reaction.

The mass distribution in massive elliptical galaxies encodes their evolutionary history, thus providing an avenue to constrain the baryonic astrophysics in their evolution. The power-law assumption for the radial mass profile in ellipticals has been sufficient to describe several observables to the noise level, including strong lensing and stellar dynamics. In this paper, we quantitatively constrained any deviation, or the lack thereof, from the power-law mass profile in massive ellipticals through joint lensing-dynamics analysis of a large statistical sample with 77 galaxy-galaxy lens systems. We performed an improved and uniform lens modelling of these systems from archival Hubble Space Telescope imaging using the automated lens modelling pipeline dolphin. We combined the lens model posteriors with the stellar dynamics to constrain the deviation from the power law after accounting for the line-of-sight lensing effects, a first for analyses on galaxy-galaxy lenses. We find that the Sloan Lens ACS Survey (SLACS) lens galaxies with a mean redshift of 0.2 are consistent with the power-law profile within 1.1$\sigma$ (2.8$\sigma$) and the Strong Lensing Legacy Survey (SL2S) lens galaxies with a mean redshift of 0.6 are consistent within 0.8$\sigma$ (2.1$\sigma$), for a spatially constant (Osipkov-Merritt) stellar anisotropy profile. We adopted the spatially constant anisotropy profile as our baseline choice based on previous dynamical observables of local ellipticals. However, spatially resolved stellar kinematics of lens galaxies are necessary to differentiate between the two anisotropy models. Future studies will use our lens models to constrain the mass distribution individually in the dark matter and baryonic components.

Disk-fed accretion onto neutron stars can power a wide range of astrophysical sources ranging from X-ray binaries, to accretion powered millisecond pulsars, ultra-luminous X-ray sources, and gamma-ray bursts. A crucial parameter controlling the gas-magnetosphere interaction is the strength of the stellar dipole. In addition, coherent X-ray pulsations in many neutron star systems indicate that the star's dipole moment is oblique relative to its rotation axis. Therefore, it is critical to systematically explore the 2D parameter space of the star's magnetic field strength and obliquity, which is what this work does, for the first time, in the framework of 3D general-relativistic magnetohydrodynamics. If the accretion disk carries its own vertical magnetic field, this introduces an additional factor: the relative polarity of the disk and stellar magnetic fields. We find that depending on the strength of the stellar dipole and the star-disk relative polarity, the neutron star's jet power can either increase or decrease with increasing obliquity. For weak dipole strength (equivalently, high accretion rate), the parallel polarity results in a positive correlation between jet power and obliquity, whereas the anti-parallel orientation displays the opposite trend. For stronger dipoles, the relative polarity effect disappears, and jet power always decreases with increasing obliquity. The influence of the relative polarity gradually disappears as obliquity increases. Highly oblique pulsars tend to have an increased magnetospheric radius, a lower mass accretion rate, and enter the propeller regime at lower magnetic moments than aligned stars.

When a galaxy falls into a cluster, its outermost parts are the most affected by the environment. In this paper, we are interested in studying the influence of a dense environment on different galaxy's components to better understand how this affects the evolution of galaxies. We use, as laboratory for this study, the Hydra cluster which is close to virialization; yet it still shows evidence of substructures. We present a multi-wavelength bulge-disc decomposition performed simultaneously in 12 bands from S-PLUS data for 52 galaxies brighter than m$_{r}$= 16. We model the galaxies with a Sersic profile for the bulge and an exponential profile for the disc. We find that the smaller, more compact, and bulge-dominated galaxies tend to exhibit a redder colour at a fixed stellar mass. This suggests that the same mechanisms (ram-pressure stripping and tidal stripping) that are causing the compaction in these galaxies are also causing them to stop forming stars. The bulge size is unrelated to the galaxy's stellar mass, while the disc size increases with greater stellar mass, indicating the dominant role of the disc in the overall galaxy mass-size relation found. Furthermore, our analysis of the environment unveils that quenched galaxies are prevalent in regions likely associated with substructures. However, these areas also harbour a minority of star-forming galaxies, primarily resulting from galaxy interactions. Lastly, we find that ~37 percent of the galaxies exhibit bulges that are bluer than their discs, indicative of an outside-in quenching process in this type of dense environments.

We report on contemporaneous optical observations at ~10 ms timescales from the fast radio burst (FRB) 20180916B of two repeat bursts (FRB 20201023, FRB 20220908) taken with the 'Alopeke camera on the Gemini North telescope. These repeats have radio fluences of 2.8 and 3.5 Jy ms, respectively, approximately in the lower 50th percentile for fluence from this repeating burst. The 'Alopeke data reveal no significant optical detections at the FRB position and we place 3-sigma upper limits to the optical fluences of <8.3e-3 and <7.7e-3 Jy ms after correcting for line-of-sight extinction. Together, these yield the most sensitive limits to the optical-to-radio fluence ratio of an FRB on these timescales with eta < 3e-3 by roughly an order of magnitude. These measurements rule out progenitor models where FRB 20180916B has a similar fluence ratio to optical pulsars similar to the Crab pulsar or optical emission is produced as inverse Compton radiation in a pulsar magnetosphere or young supernova remnant. Our ongoing program with 'Alopeke on Gemini-N will continue to monitor repeating FRBs, including FRB 20180916B, to search for optical counterparts on ms timescales.

Magnetars are slowly rotating neutron stars that possess the strongest magnetic fields ($10^{14}-10^{15} \mathrm{G}$) known in the cosmos. They display a range of transient high-energy electromagnetic activity. The brightest and most energetic of these events are the gamma-ray bursts (GRBs) known as magnetar giant flares (MGFs), with isotropic energy $E\approx10^{44}-10^{46} \mathrm{erg}$. There are only seven detections identified as MGFs to date: three unambiguous events occurred in our Galaxy and the Magellanic Clouds, and the other four MGF candidates are associated with nearby star-forming galaxies. As all seven identified MGFs are bright at Earth, additional weaker events remain unidentified in archival data. We conducted a search of the Fermi Gamma-ray Burst Monitor (GBM) database for candidate extragalactic MGFs and, when possible, collected localization data from the Interplanetary Network (IPN) satellites. Our search yielded one convincing event, GRB 180128A. IPN localizes this burst with NGC 253, commonly known as the Sculptor Galaxy. This event is the second MGF in modern astronomy to be associated with this galaxy and the first time two bursts are associated with a single galaxy outside our own. Here, we detail the archival search criteria that uncovered this event and its spectral and temporal properties, which are consistent with expectations for a MGF. We also discuss the theoretical implications and finer burst structures resolved from various binning methods. Our analysis provides observational evidence for an eighth identified MGF.

Supermassive black holes can experience super-Eddington peak mass fallback rates following the tidal disruption of a star. The theoretical expectation is that part of the infalling material is expelled by means of an accretion disk wind, whose observational signature includes blueshifted absorption lines of highly ionized species in X-ray spectra. To date, however, only one such ultra-fast outflow (UFO) has been reported in the tidal disruption event (TDE) ASASSN-14li. Here we report on the discovery of transient absorption-like signatures in X-ray spectra of the TDE AT2020ksf/Gaia20cjk (at a redshift of $z$=0.092), following an X-ray brightening $\sim 230$ days after UV/optical peak. We find that while no statistically significant absorption features are present initially, they appear on a timescale of several days, and remain detected up to 770 days after peak. Simple thermal continuum models, combined with a power-law or neutral absorber, do not describe these features well. Adding a partial covering, low velocity ionized absorber improves the fit at early times, but fails at late times. A high velocity (v$_w$ $\sim$ 42000 km s$^{-1}$, or -0.15c), ionized absorber (ultra-fast outflow) provides a good fit to all data. The few day timescale of variability is consistent with expectations for a clumpy wind. We discuss several scenarios that could explain the X-ray delay, as well as the potential for larger scale wind feedback. The serendipitous nature of the discovery could suggest a high incidence of UFOs in TDEs, alleviating some of the tension with theoretical expectations.

In this work we study the early-time behavior and the background evolution of ultra-light vector dark matter. We present a model for vector dark matter in an anisotropic Bianchi type I universe. Vector fields source anisotropies in the early universe characterized by a shear tensor which rapidly decays once the fields start oscillating, making them viable dark matter candidates. We present the set of equations needed to evolve scalar cosmological perturbations in the linear regime, both in Synchronous gauge and Newtonian gauge. We show that the shear tensor has to be taken into account in the calculation of adiabatic initial conditions.

High-velocity clouds (HVCs) are multi-phase gas structures whose velocities (|v_LSR|>100 km/s) are too high to be explained by Galactic disk rotation. While large HVCs are well characterized, compact and small HVCs (with HI angular sizes of a few degrees) are poorly understood. Possible origins for such small clouds include Milky Way halo gas or fragments of the Magellanic System, but neither their origin nor their connection to the Milky Way halo has been confirmed. We use new Hubble Space Telescope/Cosmic Origins Spectrograph UV spectra and Green Bank Telescope HI spectra to measure the metallicities of five small HVCs in the southern Galactic sky projected near the Magellanic System. We build a set of distance-dependent Cloudy photoionization models for each cloud and calculate their ionization-corrected metallicities. All five small HVCs have oxygen metallicities <0.17 Z_sun, indicating they do not originate in the disk of the Milky Way. Two of the five have metallicities of 0.16-0.17 Z_sun, similar to the Magellanic Stream, suggesting these clouds are fragments of the Magellanic System. The remaining three clouds have much lower metallicities of 0.02-0.04 Z_sun. While the origin of these low-metallicity clouds is unclear, they could be gaseous mini-halos or gas stripped from dwarf galaxies by ram pressure or tidal interactions. These results suggest that small HVCs do not all reside in the inner Milky Way halo or the Magellanic System, but instead can trace more distant structures.

We present a comparison of the presence and properties of dust in two distinct phases of the Milky Way's interstellar medium: the warm neutral medium (WNM) and the warm ionized medium (WIM). Using distant pulsars at high Galactic latitudes and vertical distance ($|b| > 40\deg$, $D \sin|b| > 2 \mathrm{\,\, kpc}$) as probes, we measure their dispersion measures and the neutral hydrogen component of the warm neutral medium ($\text{WNM}_\text{HI}$) using HI column density. Together with dust intensity along these same sightlines, we separate the respective dust contributions of each ISM phase in order to determine whether the ionized component contributes to the dust signal. We measure the temperature ($T$), spectral index ($\beta$), and dust opacity ($\tau/N_{H}$) in both phases. We find $T~{\text{(WNM}_\text{HI})}=20^{+3}_{-2}$~K, $\beta~{\text{(WNM}_\text{HI})} = 1.5\pm{0.4}$, and $\tau_{\text{353}}/N_{H}~{\text{(WNM}_\text{HI})}=(1.0\pm0.1)\times 10^{-26}$~cm$^2$. Assuming that the temperature and spectral index are the same in both the WNM$_\text{HI}$ and WIM, and given our simple model that widely separated lines-of-sight can be fit together, we find evidence that there is a dust signal associated with the ionized gas and $\tau_{\text{353}}/N_{H}~\text{(WIM)}=(0.3\pm0.3)\times 10^{-26}$, which is about three times smaller than $\tau_{\text{353}}/N_{H}~{\text{(WNM}_\text{HI})}$. We are 80% confident that $\tau_{\text{353}}/N_{H}~\text{(WIM)}$ is at least two times smaller than $\tau_{\text{353}}/N_{H}~{\text{(WNM}_\text{HI})}$.

Kilonovae are a class of astronomical transients observed as counterparts to mergers of compact binary systems, such as a binary neutron star (BNS) or black hole-neutron star (BHNS) inspirals. They serve as probes for heavy-element nucleosynthesis in astrophysical environments, while together with gravitational wave emission constraining the distance to the merger itself, they can place constraints on the Hubble constant. Obtaining the physical parameters (e.g. ejecta mass, velocity, composition) of a kilonova from observations is a complex inverse problem, usually tackled by sampling-based inference methods such as Markov-chain Monte Carlo (MCMC) or nested sampling techniques. These methods often rely on computing approximate likelihoods, since a full simulation of compact object mergers involve expensive computations such as integrals, the calculation of likelihood of the observed data given parameters can become intractable, rendering the likelihood-based inference approaches inapplicable. We propose here to use Simulation-based Inference (SBI) techniques to infer the physical parameters of BNS kilonovae from their spectra, using simulations produced with KilonovaNet. Our model uses Amortized Neural Posterior Estimation (ANPE) together with an embedding neural network to accurately predict posterior distributions from simulated spectra. We further test our model with real observations from AT2017gfo, the only kilonova with multi-messenger data, and show that our estimates agree with previous likelihood-based approaches.

In this paper, we provide a first physical interpretation for the Event Horizon Telescope (EHT)'s 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic magnetohydrodynamics (GRMHD) simulations, including aligned, tilted, and stellar wind-fed simulations; radiative transfer is performed assuming both thermal and non-thermal electron distribution functions. We test the models against 11 constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2 $\mu$m, and in the X-ray. All models fail at least one constraint. Light curve variability provides a particularly severe constraint, failing nearly all strongly magnetized (MAD) models and a large fraction of weakly magnetized (SANE) models. A number of models fail only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination $i \le$ 30$^\circ$. They have accretion rate $(5.2$-$9.5)\times10^{-9}M_\odot$yr$^{-1}$, bolometric luminosity $(6.8$--$9.2)\times10^{35}$ erg s$^{-1}$, and outflow power $(1.3$--$4.8)\times10^{38}$ erg s$^{-1}$. We also find that: all models with $i \ge$ 70$^\circ$ fail at least two constraints, as do all models with equal ion and electron temperature; exploratory, non-thermal model sets tend to have higher 2.2 $\mu$m flux density; the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung overproduction. Finally we discuss physical and numerical limitations of the models, highlighting the possible importance of kinetic effects and duration of the simulations.

We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium towards the Galactic Center. Mitigation of the rapid intra-day variability that characterizes Sgr A* has been carried out through the addition of a "variability noise budget" in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions, and a small cluster that contains diverse non-ring morphologies. Based on our extensive analysis of the effects of sparse $(u,v)$-coverage, source variability and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of $\sim$ 50 $\mu$as, consistent with the expected "shadow" of a $4\times10^6 M_\odot$ black hole in the Galactic Center located at a distance of 8 kpc.

Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A* to show that the observed image size is within $\sim$ 10$\%$ of the Kerr predictions. We use these bounds to constrain metrics that are parametrically different from Kerr as well as the charges of several known spacetimes. To consider alternatives to the presence of an event horizon we explore the possibility that Sgr A* is a compact object with a surface that either absorbs and thermally re-emits incident radiation or partially reflects it. Using the observed image size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the bounds found for stellar mass black holes and the M87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.

I examine the applicability of ecological concepts in discussing issues related to space environmentalism. Terms such as "ecosystem"", "carrying capacity"", and "tipping point" are either ambiguous or well defined but not applicable to orbital space and its contents; using such terms uncritically may cause more confusion than enlightenment. On the other hand, it may well be fruitful to adopt the approach of the Planetary Boundaries Framework, defining trackable metrics that capture the damage to the space environment. I argue that the key metric is simply the number of Anthropogenic Space Objects (ASOs), rather than for example their reflectivity, which is currently doubling every 1.7 years; we are heading towards degree scale separation. Overcrowding of the sky is a problem astronomers and satellite operators have in common.

The Carbon-Enhanced Metal-Poor (CEMP) stars with no enhancement of neutron-capture elements, the so-called CEMP-no stars are believed to be the direct descendants of first-generation stars and provide a unique opportunity to probe the early Galactic nucleosynthesis. We present a detailed chemical and kinematic analysis for two extremely metal-poor stars HE1243$-$2408 and HE0038$-$0345 using high-resolution (R${\sim}$86,000) HERMES spectra. For the object HE1243$-$2408, we could make a detailed comparison with the available literature values; however, only limited information is available for the other object HE0038$-$0345. Our estimated metallicity for these two objects are $-$3.05 and $-$2.92 respectively. With estimated [C/Fe] (1.03 and 1.05) and [Ba/Fe] ($-$0.18 and $-$0.11) respectively, the objects are found to be bonafide CEMP-no stars. From the observed abundances of C, Na, Mg, and Ba (i.e., A(C), A(Na), A(Mg), A(Ba)), the objects are found to belong to Group II CEMP-no stars. A detailed abundance profile analysis indicates that the objects are accreted from dSph satellite galaxies that support hierarchical Galaxy assembly. Further, our analysis shows that the progenitors of the stars are likely Pop II Core-Collapse Supernovae. The object HE0038$-$0345 is found to be a high-energy, prograde, outer-halo object, and HE1243$-$2408 is found to be a high-energy, retrograde, inner-halo object. Our detailed chemodynamical analysis shows that HE1243$-$2408 is related to I'itoi structure, where as HE0038$-$0345 is likely related to Sgr or GSE events. The mass of the progenitor galaxies of the program stars inferred from their dynamics is at par with their likely origin in massive dSph galaxies.

We present a detailed analysis of a new, iterative density reconstruction algorithm. This algorithm uses a decreasing smoothing scale to better reconstruct the density field in Lagrangian space. We implement this algorithm to run on the Quijote simulations, and extend it to (a) include a smoothing kernel that smoothly goes from anisotropic to isotropic, and (b) a variant that does not correct for redshift space distortions. We compare the performance of this algorithm with the standard reconstruction method. Our examinations of the methods include cross-correlation of the reconstructed density field with the linear density field, reconstructed two-point functions, and BAO parameter fitting. We also examine the impact of various parameters, such as smoothing scale, anisotropic smoothing, tracer type/bias, and the inclusion of second order perturbation theory. We find that the two reconstruction algorithms are comparable in most of the areas we examine. In particular, both algorithms give consistent fittings of BAO parameters. The fits are robust over a range of smoothing scales. We find the iterative algorithm is significantly better at removing redshift space distortions. The new algorithm will be a promising method to be employed in the ongoing and future large-scale structure surveys.

We numerically study the diffusion and scattering of cosmic rays (CRs) together with their acceleration processes in the framework of the modern understanding of magnetohydrodynamic (MHD) turbulence. Based on the properties of compressible MHD turbulence obtained from observations and numerical experiments, we investigate the interaction of CRs with plasma modes. We find that (1) the gyroradius of particles exponentially increases with the acceleration timescale; (2) the momentum diffusion presents the power-law relationship with the gyroradius in the strong turbulence regime, and shows a plateau in the weak turbulence regime implying a stochastic acceleration process; (3) the spatial diffusion is dominated by the parallel diffusion in the sub-Alfv\'enic regime, while it is dominated by the perpendicular diffusion in the super-Alfv\'enic one; (4) as for the interaction of CRs with plasma modes, the particle acceleration is dominated by the fast mode in the high $\beta$ case, while in the low $\beta$ case, it is dominated by the fast and slow modes; (5) in the presence of acceleration, magnetosonic modes still play a critical role in diffusion and scattering processes of CRs, which is in good agreement with the earlier theoretical predictions.

The fast rotating solar analogs show a decrease of the dynamo period with an increase of the rotation rate for the moderate stellar rotation periods in the range between 10 and 25 days. Simultaneously, observations indicate two branches: the "in-active" branch stars shows short dynamo cycles and the active branch stars show the relatively long magnetic cycles. We suggest that this phenomenon can be produced by effect of the doubling frequency of the dynamo waves, which is due to excitation of the second harmonic. It is generated because of the nonlinear $B^{2}$ effects in the large-scale dynamo.

Our study aims to investigate the outer disc structure of the Milky Way galaxy using the red clump (RC) stars. We analysed the distribution of the largest sample of RC stars to date, homogeneously covering the entire Galactic plane in the range of $40^\circ \le \ell \le 340^\circ$ and $-10^\circ \le b \le +10^\circ$. This sample allows us to model the RC star distribution in the Galactic disc to better constrain the properties of the flare and warp of the Galaxy. Our results show that the scale length of the old stellar disc weakly depends on azimuth, with an average value of $1.95 \pm0.26$ kpc. On the other hand, a significant disc flaring is detected, where the scale height of the disc increases from 0.38 kpc in the solar neighbourhood to $\sim 2.2$ kpc at R $\approx 15$ kpc. The flare exhibits a slight asymmetry, with $\sim 1$ kpc more scale height below the Galactic plane as compared to the Northern flare. We also confirm the warping of the outer disc, which can be modelled with $Z_w = (0.0057 \pm 0.0050)~ [R-(7358 \pm 368) (pc)]^{1.40 \pm 0.09} \sin(\phi - (-2^\circ.03 \pm 0^\circ .18))$. Our analysis reveals a noticeable north-south asymmetry in the warp, with a greater amplitude observed in the southern direction compared to the northern. Comparing our findings with younger tracers from the literature, we observe an age dependency of both the flare and warp. An increase in flare strength with age suggests the secular evolution of the disc as the preferred mechanism for forming the flare. The increase of the maximum warp amplitude with age indicates that the warp dynamics could be the possible cause of the variation in the warp properties with age.

Dust is a ubiquitous component in our Galaxy. It accounts for only $1\%$ mass of the ISM but still is an essential part of the Galaxy. It affects our view of the Galaxy by obscuring the starlight at shorter wavelengths and re-emitting in longer wavelengths. Studying the dust distribution in the Galaxy at longer wavelengths may cause discrepancies due to distance ambiguity caused by unknown Galactic potential. However, another aspect of dust, i.e., the polarisation of the background starlight, when combined with distance information, will help to give direct observational evidence of the number of dust clouds encountered in the line of sight. We observed 15 open clusters distributed at increasing distances in three lines of sight using two Indian national facilities. The measured polarisation results used to scrutinize the dust distribution and orientation of the local plane of sky magnetic fields towards selected directions. The analysis of the stars observed towards the distant cluster King 8 cluster shows two foreground layers at a distance of $\sim 500$ pc and $\sim$ 3500 pc. Similar analysis towards different clusters also results in multiple dust layers.

The study of the differential rotation in the chromosphere of the Sun is of significant importance as it provides valuable insights into the rotational behaviour of the solar atmosphere at higher altitudes and the coupling mechanism between the various layers of the solar atmosphere. In this work, we employed the image correlation technique, explicitly focusing on plages, intending to estimate the chromospheric differential rotation. For this purpose, we have utilized Ca II K spectroheliograms (1907-2007) from the Kodaikanal Solar Observatory (KoSO), recently calibrated with a better technique to ensure accuracy. Our analysis indicates that plages in the chromosphere exhibit faster rotation and a smaller latitudinal gradient when compared to the rotation rate obtained through sunspot tracking. Furthermore, we investigate the temporal analysis of the chromospheric differential rotation parameters across various solar cycles.

We present the first detailed analysis of the ultra-steep spectrum radio halo in the merging galaxy cluster Abell 521, based on upgraded Giant Metrewave Radio telescope (uGMRT) observations. The combination of radio observations (300-850 MHz) and archival X-ray data provide a new window into the complex physics occurring in this system. When compared to all previous analyses, our sensitive radio images detected the centrally located radio halo emission to a greater extent of $\sim$ 1.3 Mpc. A faint extension of the southeastern radio relic has been discovered. We detected another relic, recently discovered by MeerKAT, and coincident with a possible shock front in the X-rays, at the northwest position of the center. We find that the integrated spectrum of the radio halo is well-fitted with a spectral index of $-1.86 \pm 0.12$. A spatially resolved spectral index map revealed the spectral index fluctuations, as well as an outward radial steepening of the average spectral index. The radio and X-ray surface brightness are well correlated for the entire and different sub-parts of the halo, with sub-linear correlation slopes (0.50$-$0.65). We also found a mild anti-correlation between the spectral index and X-ray surface brightness. Newly detected extensions of the SE relic and the counter relic are consistent with the merger in the plane of the sky.

Semi-detached binaries are in the stage of mass transfer and play a crucial role in studying mass transfer physics between interacting binaries. Large-scale time-domain surveys provide massive light curves of binary systems, while Gaia offers high-precision astrometric data. In this paper, we develop, validate, and apply a pipeline that combines the MCMC method with a forward model and DBSCAN clustering to search for semi-detached binary and estimate its inclination, relative radius, mass ratio, and temperature ratio using light curve. We train our model on the mock light curves from PHOEBE, which provides broad coverage of light curve simulations for semi-detached binaries. Applying our pipeline to TESS sectors 1-26, we have identified 77 semi-detached binary candidates. Utilizing the distance from Gaia, we determine their masses and radii with median fractional uncertainties of ~26% and ~7%, respectively. With the added 77 candidates, the catalog of semi-detached binaries with orbital parameters has been expanded by approximately 20%. The comparison and statistical results show that our semi-detached binary candidates align well with the compiled samples and the PARSEC model in Teff-L and M-R relations. Combined with the literature samples, comparative analysis with stability criteria for conserved mass transfer indicates that ~97.4% of samples are undergoing nuclear-timescale mass transfer, and two samples (GO Cyg and TIC 454222105) are located within the limits of stability criteria for dynamical- and thermal-timescale mass transfer, which are currently undergoing thermal-timescale mass transfer. Additionally, one system (IR Lyn) is very close to the upper limit of delayed dynamical-timescale mass transfer.

Stars like company. They are mostly formed in clusters and their lives are often altered by the presence of one or more companions. Interaction processes between components may lead to complex outcomes like Algols, blue stragglers, chemically altered stars, type Ia supernovae, as well as progenitors of gravitational wave sources, to cite a few. Observational astronomy has entered the era of big data, and thanks to large surveys like spatial missions Kepler, TESS, Gaia, and ground-based spectroscopic surveys like RAVE, Gaia-ESO, APOGEE, LAMOST, GALAH (to name a few) the field is going through a true revolution, as illustrated by the recent detection of stellar black holes and neutron stars as companions of massive but also low-mass stars. In this review, I will present why it is important to care about stellar multiples, what are the main large surveys in which many binaries are harvested, and finally present some features related to the largest catalogue of astrometric, spectroscopic and eclipsing binaries provided by the Non-Single Star catalogue of Gaia, which is, to date, the largest homogeneous catalogue of stellar binaries.

Our knowledge about neutron star (NS) masses is renewed once again due to the recognition of the heaviest NS PSR J$ 0952-0607 $. By taking advantage of both mass observations of super massive neutron stars and the tidal deformability derived from event GW170817, a joint constraint on tidal deformability is obtained. A wide-ranging correlation between NS pressure and tidal deformability within the density range from saturation density $\rho_0$ to $5.6\rho_0$ is discovered, which directly yields a constrained NS EoS. The newly constrained EoS has a small uncertainty and a softer behavior at high densities without the inclusion of extra degrees of freedom, which shows its potential to be used as an indicator for the component of NS core.

We use a large set of halo mass function (HMF) models in order to investigate their ability to represent the observational Cluster Mass Function (CMF), derived from the $\mathtt{GalWCat19}$ cluster catalogue, within the $\Lambda$CDM cosmology. We apply the $\chi^2$ minimization procedure to constrain the free parameters of the models, namely $\Omega_m$ and $\sigma_8$. We find that all HMF models fit well the observational CMF, while the Bocquet et. al. model provides the best fit, with the lowest $\chi^2$ value. Utilizing the {\em Index of Inconsistency} (IOI) measure, we further test the possible inconsistency of the models with respect to a variety of {\em Planck 2018} $\Lambda$CDM cosmologies, resulting from the combination of different probes (CMB - BAO or CMB - DES). We find that the HMF models that fitted well the observed CMF provide consistent cosmological parameters with those of the {\em Planck} CMB analysis, except for the Press $\&$ Schechter, Yahagi et. al., and Despali et. al. models which return large IOI values. The inverse $\chi_{\rm min}^2$-weighted average values of $\Omega_m$ and $\sigma_8$, over all 23 theoretical HMF models are: ${\bar \Omega_{m,0}}=0.313\pm 0.022$ and ${\bar \sigma_8}=0.798\pm0.040$, which are clearly consistent with the results of {\em Planck}-CMB, providing $S_8=\sigma_8\left(\Omega_m/0.3\right)^{1/2}= 0.815\pm 0.05$. Within the $\Lambda$CDM paradigm and independently of the selected HMF model in the analysis, we find that the current CMF shows no $\sigma_8$-tension with the corresponding {\em Planck}-CMB results.

The detection of a high velocity (~ 0.3c) inflow of highly ionized matter during a long XMM-Newton observation of the luminous Seyfert galaxy PG 1211+143 in 2014 offered the first direct observational evidence of a short-lived accretion event, where matter approaching at a high inclination to the black hole spin plane may result in warping and tearing of the inner accretion disc, with subsequent inter-ring collisions producing shocks, loss of rotational support and rapid mass infall. In turn, such accretion events provide an explanation for the ultrafast outflows (UFOs) now recognised as a common property of many luminous Seyfert galaxies. While the ultra-fast inflow in PG 1211+143 was detected in only one of 7 spacecraft orbits, a weaker (lower column density) inflow, at a much lower redshift of ~ 0.123, is revealed in the soft x-ray spectrum by summing RGS data over the full 5-weeks XMM-Newton campaign. Modelling of the simultaneous, stacked pn data finds evidence for a similar low redshift absorption component in a previously unexplained feature on the low energy wing of the Fe K emission line complex near 6 keV. We briefly consider Doppler and strong gravity explanations for the observed redshift, with the former indicating a distant inflow feeding off-plane accretion, where an infall velocity of v ~ 0.038c and (free-fall) radius at 1400 R$_{g}$ lies beyond the tearing radius for PG 1211+143, but still within the sphere of influence of the SMBH. An intriguing alternative, recently given added credence, might be as the gravitational redshift of absorption in matter orbiting the SMBH at a radius of ~ 27 R_g. In the latter case the narrow RGS absorption line spectrum constrains the thickness of the orbiting ring due to the strong velocity shear so close to the hole.

Exclusion zones in the cross-correlations between critical points (peak-void, peak-wall, filament-wall, filament-void) of the density field define quasi-standard rulers that can be used to constrain dark matter and dark energy cosmological parameters. The average size of the exclusion zone is found to scale linearly with the typical distance between extrema. The latter changes as a function of the matter content of the universe in a predictable manner, but its comoving size remains essentially constant in the linear regime of structure growth on large scales, unless the incorrect cosmology is assumed in the redshift-distance relation. This can be used to constrain the dark energy parameters when considering a survey that scans a range of redshifts. The precision of the parameter estimation is assessed using a set of cosmological simulations, and is found to be a 4$\sigma$ detection of a change in matter content of 5%, or about 3.8$\sigma$ detection of 50% shift in the dark energy parameter using a full sky survey up to redshift 0.5.

Collisional (de-)excitation of H$_{2}$ by helium plays an important role in the thermal balance and chemistry of various astrophysical environments, making accurate rate coefficients essential for the interpretation of observations of the interstellar medium. Our goal is to utilize a state-of-the-art potential energy surface (PES) to provide comprehensive state-to-state rate coefficients for He-induced transitions among rovibrational levels of H$_{2}$. We perform quantum scattering calculations for the H$_{2}$-He system and provide state-to-state rate coefficients for 1 089 transitions between rovibrational levels of H$_{2}$ with internal energies up to 15 000 cm$^{-1}$ for temperatures ranging from 20 to 8 000 K. Our results show good agreement with previous calculations for pure rotational transitions between low-lying rotational levels, but we find significant discrepancies for rovibrational processes involving highly-excited rotational and vibrational states. We attribute these differences to two key factors: the broader range of intramolecular distances covered by ab initio points, and the superior accuracy of the PES, resulting from the utilization of the state-of-the-art quantum chemistry methods, compared to the previous lower-level calculations. Radiative transfer calculations performed with the new collisional data indicate that the population of rotational levels in excited vibrational states experiences significant modifications, highlighting the critical need for this updated dataset in models of high-temperature astrophysical environments.

The meridional circulation of the solar magnetic fields in Solar Cycles 21-24 was considered. Data from both ground-based and space observatories were used. Three types of time-latitude distributions of photospheric magnetic fields and their meridional circulations were identified depending on the magnetic field intensity. (i) low-strength magnetic fields. They were distributed evenly across latitude and weakly depended on the magnetic fields of active regions and their cycle variation; (ii) medium-strength magnetic fields. For these fields a wave-like, pole-to-pole, antiphase meridional circulation with a period of approximately 22 years was revealed. The velocities of meridional flows were slower at the minima of solar activity, when they were at high latitudes in the opposite hemispheres, and maximal at the solar maxima, when the positive- and negative-polarity waves crossed the equator. The meridional circulation of these fields reflects the solar global magnetic field dynamics and determines the solar polar field reversal; (iii) high-strength (active region) magnetic fields. They were distributed symmetrically in the Northern and Southern hemispheres. Magnetic fields of both leading and following sunspot polarity migrated from high to low latitudes. The meridional-flow velocities of high-strength magnetic fields were higher at the rising and maxima phases than at the minima. Some of the high-latitude active region magnetic fields were captured by the second type meridional circulation flows and transported along with them to the appropriate pole. But the magnetic fields of active regions are not the main ones in the solar polar field reversal. The results indicate that high-strength magnetic fields were not the main source of weak ones.

Finding the emergence of the first generation of metals in the early Universe, and identifying their origin, are some of the most important goals of modern astrophysics. We present deep JWST/NIRSpec spectroscopy of GS-z12, a galaxy at z=12.5, in which we report the detection of C III]${\lambda}{\lambda}$1907,1909 nebular emission. This is the most distant detection of a metal transition and the most distant redshift determination via emission lines. In addition, we report tentative detections of [O II]${\lambda}{\lambda}$3726,3729 and [Ne III]${\lambda}$3869, and possibly O III]${\lambda}{\lambda}$1661,1666. By using the accurate redshift from C III], we can model the Ly${\alpha}$ drop to reliably measure an absorbing column density of hydrogen of $N_{HI} \approx 10^{22}$ cm$^{-2}$ - too high for an IGM origin and implying abundant ISM in GS-z12 or CGM around it. We infer a lower limit for the neutral gas mass of about $10^7$ MSun which, compared with a stellar mass of $\approx4 \times 10^7$ MSun inferred from the continuum fitting, implies a gas fraction higher than about 0.1-0.5. We derive a solar or even super-solar carbon-to-oxygen ratio, tentatively [C/O]>0.15. This is higher than the C/O measured in galaxies discovered by JWST at z=6-9, and higher than the C/O arising from Type-II supernovae enrichment, while AGB stars cannot contribute to carbon enrichment at these early epochs and low metallicities. Such a high C/O in a galaxy observed 350 Myr after the Big Bang may be explained by the yields of extremely metal poor stars, and may even be the heritage of the first generation of supernovae from Population III progenitors.

Based on the atomic-hydrogen (HI) observations using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we present a detailed study of the gas-rich massive S0 galaxy NGC 1023 in a nearby galaxy group. The presence of an HI extended warped disk in NGC 1023 indicates that this S0 galaxy originated from a spiral galaxy. The data also suggest that NGC 1023 is interacting with four dwarf galaxies. In particular, one of the largest dwarf galaxies has fallen into the gas disk of NGC 1023, forming a rare bright-dark galaxy pair with a large gas clump. This clump shows the signature of a galaxy but has no optical counterpart, implying that it is a newly formed starless galaxy. Our results firstly suggest that a massive S0 galaxy in a galaxy group can form via the morphological transformation from a spiral under the joint action of multiple tidal interactions.

We look for signatures of the Hu-Sawicki f(R) modified gravity theory, proposed to explain the observed accelerated expansion of the universe; in observations of the galaxy distribution, the cosmic microwave background (CMB), and gravitational lensing of the CMB. We study constraints obtained by using observations of only the CMB primary anisotropies, before adding the galaxy power spectrum and its cross-correlation with CMB lensing. We show that cross-correlation of the galaxy distribution with lensing measurements is crucial to breaking parameter degeneracies, placing tighter constraints on the model. In particular, we set a strong upper limit on $\log{\lvert f_{R_0}\lvert }<-4.61$ at 95% confidence level. This means that while the model may explain the accelerated expansion, its impact on large-scale structure closely resembles General Relativity. Studies of this kind with future data sets will probe smaller potential deviations from General Relativity.

Solar system Centaurs originate in transneptunian space from where planet orbit crossing events inject their orbits inside the giant planets' domain. Here, we examine this injection process in the three-body problem by studying the orbital evolution of transneptunian asteroids located at Neptune's collision singularity as a function of the Tisserand invariant, T. Two injection modes are found, one for T>0.1, or equivalently prograde inclinations far from the planet, where unstable motion dominates injection, and another for T<= 0.1, or equivalently polar and retrograde inclinations far from the planet, where stable motion dominates injection. The injection modes are independent of the initial semi-major axis and the dynamical time at the collision singularity. The simulations uncovered a region in the polar corridor where the dynamical time exceeds the solar system's age suggesting the possibility of long-lived primordial polar transneptunian reservoirs that supply Centaurs to the giant planets' domain.

We have observed the Didymos-Dimorphos binary system with the MUSE integral field unit spectrograph mounted at the Very Large Telescope (VLT) pre and post-DART impact, and captured the ensuing ejecta cone, debris cloud, and tails at sub-arcsecond resolutions. We targeted the Didymos system over 11 nights from 26 September to 25 October 2022, and utilized both narrow and wide-field observations with and without adaptive optics, respectively. We took advantage of the spectral-spatial coupled measurements and produced both white-light images and spectral maps of the dust reflectance. We identified and characterized numerous dust features, such as the ejecta cone, spirals, wings, clumps, and tails. We found that the base of the Sunward edge of the wings, from 03 to 19 October, consistent with maximum grain sizes on the order of 0.05-0.2 mm, and that the earliest detected clumps have the highest velocities on the order of 10 m/s. We also see that three clumps in narrow-field mode (8x8'') exhibit redder colors and slower speeds, around 0.09 m/s, than the surrounding ejecta, likely indicating that the clump is comprised of larger, slower grains. We measured the properties of the primary tail, and resolved and measured the properties of the secondary tail earlier than any other published study, with first retrieval on 03 October. Both tails exhibit similarities in curvature and relative flux, however, the secondary tail appears thinner, which may be caused by lower energy ejecta and possibly a low energy formation mechanism such as secondary impacts.

A Crescent shaped prominence Structure (CS), over the solar west limb is studied using EIS/HINODE and AIA/SDO. First, the time varying positions of the top and below borders of the CS, along with its central axis are derived. Time evolutions of the Doppler shifts, and Line width of Fe~{\scriptsize \rm XII} 195.119 line are studied over the CS borders. Transverse kink oscillations are observed both in the Solar-Y direction and in the Doppler shifts over the observers' LOS. One explanation could be the oscillatory direction of the main kink wave build an angle with the observers LOS. This angle is calculated to be equal to 27 degrees for the CS top border. The main kink amplitude velocity and periods are obtained to be 5.3 $\rm km/s$, and 33.4 minutes, respectively. The anti-correlation observed between the brightness and thickness of the CS (with -178.1$^\circ$) suggests the presence of sausage modes with periods of 20.8 minutes. Based on the AIA imaging, it is suggested that the occurred jets and their afterward dimming are responsible to trigger the sausage mode. The average electron densities of the CS over the time of the study is obtained to be log($\rm n_e$)=9.3$\rm [cm^{-3}]$. The Alfv\'en velocity, magnetic field, and energy flux of the observed fast kink mode over the CS are estimated to be 16.7 $\rm km/s$, 2.79 $\rm G$, 41.93 $\rm W/m^2$. Considering the magnetic flux conservation inside the CS, expanding the CS cross section, causes the magnetic field to decay with the rate of $\rm 4.95 \times 10^{-4} \, G/sec$.

The abundances of the slow neutron-capture (s-) process elements observed in barium stars can be explained by considering mass transfer in a binary system from an asymptotic giant branch (AGB) star onto a smaller mass and less evolved binary companion star. Based on the abundances of neutron-capture elements the barium stars are broadly divided into two categories, "strong" and "mild" barium stars. However, an understanding of the role of the characteristic properties of the companion AGBs on the formation of the different types of barium stars is still lacking. This work focuses on investigating the role of the mass of the companion AGB stars in this context. In a recent high-resolution spectroscopic study, we studied in detail the chemical composition of a few barium stars that we have identified. In order to understand the nature and the mass of the companion stars, we first estimated the mass of these objects and then used a parametric model-based analysis to derive the masses of the primary companion stars. The calculation is extended to 205 barium stars taken from literature. An analysis of the mass distribution revealed that both the strong and the mild barium stars occupy the same range of masses. However, their companion AGB stars' mass distributions peak at two different values 2.5 M$_{\odot}$ and 3.7 M$_{\odot}$, for the strong and the mild barium stars respectively. This provides clear evidence that the formation of mild and strong Ba stars is greatly influenced by the initial masses of the companion AGB stars. It remains, however, to be seen the possible impact of other factors such as orbital period and metallicity on the formation scenarios of barium stars.

In this work, we study the evolution of Betti curves obtained by persistent-homological analysis of pointclouds formed by halos in different cosmological $N$-body simulations. We show that they can be approximated with a scaled log-normal distribution function with reasonable precision. Our analysis shows that the shapes and maximums of Betti curves exhibit dependence on the mass range of the selected subpopulation of halos, but at the same time, the resolution of a simulation does not play any significant role, provided that the mass distribution of simulated halos is complete down to a given mass scale. Besides, we study how Betti curves change with the evolution of the Universe, i.e., their dependence on redshift. Sampling subpopulations of halos within certain mass ranges up to redshift $z=2.5$ yields a surprisingly small difference between corresponding Betti curves. We propose that this may be an indicator of the existence of a new specific topological invariant in the structure of the Universe.

In the past two decades, it has been convincingly argued that magnetospheric radio emissions, of cyclotron maser origin, can occur for exoplanetary systems, similarly as solar planets, with the same periodicity as the planetary orbit. These emissions are primarily expected at low frequencies (usually below 100 MHz, c.f. Farrell et al., 1999; Zarka, 2007). The radio detection of exoplanets will considerably expand the field of comparative magnetospheric physics and star-planet plasma interactions (Hess & Zarka, 2011). We have developed a prediction code for exoplanetary radio emissions, PALANTIR: "Prediction Algorithm for star-pLANeT Interactions in Radio". This code has been developed for the construction of an up-to-date and evolutive target catalog, based on observed exoplanet physical parameters, radio emission theory, and magnetospheric physics embedded in scaling laws. It is based on, and extends, previous work by Grie{\ss}meier et al. (2007b). Using PALANTIR, we prepared an updated list of targets of interest for radio emissions. Additionally, we compare our results with previous studies conducted with similar models (Grie{\ss}meier, 2017). For the next steps, we aim at improving this code by adding new models and updating those already used.

The low-mass metal-poor stars in the Galaxy that preserve in their atmosphere, the chemical imprints of the gas clouds from which they were formed can be used as probes to get insight into the origin and evolution of elements in the early galaxy, early star formation and nucleosynthesis. Among the metal-poor stars, a large fraction, the so-called carbon-enhanced metal-poor (CEMP) stars exhibits high abundance of carbon. These stars exhibit diverse abundance patterns, particularly for heavy elements, based on which they are classified into different groups. The diversity of abundance patterns points at different formation scenarios. Hence, accurate classification of CEMP stars and knowledge of their distribution is essential to understand the role and contribution of each group. While CEMP-s and CEMP-r/s stars can be used to get insight into binary interactions at very low metallicity, CEMP-no stars can be used to probe the properties of the first stars and early nucleosynthesis. To exploit the full potential of CEMP stars for Galactic archaeology a homogeneous analysis of each class is extremely important. Our efforts towards, and contributions to providing an improved classification scheme for accurate classification of CEMP-s and CEMP-r/s stars and in characterizing the companion asymptotic giant branch (AGB) stars of CH, CEMP-no, CEMP-s and CEMP-r/s binary systems are discussed. Some recent results obtained based on low- and high-resolution spectroscopic analysis of a large number of potential CH and CEMP star candidates are highlighted.

The Next Generation Very Large Array (ngVLA) is a planned radio interferometer providing unprecedented sensitivity at wavelengths between 21 cm and 3 mm. Its 263 antenna element array will be spatially distributed across North America to enable both superb low surface brightness recovery and sub-milliarcsecond angular resolution imaging. The project was developed by the international astronomy community under the lead of the National Radio Astronomy Observatory (NRAO), and is anticipated to be built between 2027 and 2037. Two workshops have been held in 2022 and 2023 with the goal to discuss and consolidate the scientific interests in the ngVLA within the German astronomical community. This community paper constitutes a collection of 41 science ideas which the German community aims to pursue with the ngVLA in the 2030s. This is not a complete list and the ideas are not developed at the level of a "Science Book", such that the present document is mainly to be considered a "living document", to provide a basis for further discussion within the community. As such, additional contributions are welcome, and will be considered for inclusion in future revisions.

The warm-hot plasma in cosmic web filaments is thought to comprise a large fraction of the gas in the local Universe. So far, the search for this gas has focused on mapping its emission, or detecting its absorption signatures against bright, point-like sources. Future, non-dispersive, high spectral resolution X-ray detectors will, for the first time, enable absorption studies against extended objects. Here, we use the Hydrangea cosmological hydrodynamical simulations to predict the expected properties of intergalactic gas in and around massive galaxy clusters, and investigate the prospects of detecting it in absorption against the bright cores of nearby, massive, relaxed galaxy clusters. We probe a total of $138$ projections from the simulation volumes, finding $16$ directions with a total column density $N_{O VII} > 10^{14.5}$ cm$^{-2}$. The strongest absorbers are typically shifted by $\pm 1000$ km/s with respect to the rest frame of the cluster they are nearest to. Realistic mock observations with future micro-calorimeters, such as the Athena X-ray Integral Field Unit or the proposed Line Emission Mapper (LEM) X-ray probe, show that the detection of cosmic web filaments in O VII and O VIII absorption against galaxy cluster cores will be feasible. An O VII detection with a $5\sigma$ significance can be achieved in $10-250$ ks with Athena for most of the galaxy clusters considered. The O VIII detection becomes feasible only with a spectral resolution of around $1$ eV, comparable to that envisioned for LEM.

In nonminimally coupled theories where a scalar field is coupled to the Ricci scalar, neutron stars (NSs) can have scalar charges through an interaction with matter mediated by gravity. On the other hand, the same theories do not give rise to hairy black hole (BH) solutions. The observations of gravitational waves (GWs) emitted from an inspiralling NS-BH binary system allows a possibility of constraining the NS scalar change. Moreover, the nonminimally coupled scalar-tensor theories generate a breathing scalar mode besides two tensor polarizations. Using the GW200115 data of the coalescence of a BH-NS binary, we place observational constraints on the NS scalar charge as well as the nonminimal coupling strength for a subclass of massless Horndeski theories with a luminal GW propagation. Unlike past related works, we exploit a waveform for a mixture of tensor and scalar polarizations. Taking the breathing mode into account, the scalar charge is more tightly constrained in comparison to the analysis of the tensor GWs alone. In nonminimally coupled theories including Brans-Dicke gravity and spontaneous scalarization scenarios with/without a kinetic screening, we put new bounds on model parameters of each theory.

Interplanetary magnetic flux ropes (MFRs) are commonly observed structures in the solar wind, categorized as magnetic clouds (MCs) and small-scale MFRs (SMFRs) depending on whether they are associated with coronal mass ejections. We apply machine learning to systematically compare SMFRs, MCs, and ambient solar wind plasma properties. We construct a dataset of 3-minute averaged sequential data points of the solar wind's instantaneous bulk fluid plasma properties using about twenty years of measurements from \emph{Wind}. We label samples by the presence and type of MFRs containing them using a catalog based on Grad-Shafranov (GS) automated detection for SMFRs and NASA's catalog for MCs (with samples in neither labeled non-MFRs). We apply the random forest machine learning algorithm to find which categories can be more easily distinguished and by what features. MCs were distinguished from non-MFRs with an AUC of 94% and SMFRs with an AUC of 89% and had distinctive plasma properties. In contrast, while SMFRs were distinguished from non-MFRs with an AUC of 86%, this appears to rely solely on the $\langle B \rangle$ > 5 nT threshold applied by the GS catalog. The results indicate that SMFRs have virtually the same plasma properties as the ambient solar wind, unlike the distinct plasma regimes of MCs. We interpret our findings as additional evidence that most SMFRs at 1 au are generated within the solar wind, and furthermore, suggesting that they should be considered a salient feature of the solar wind's magnetic structure rather than transient events.

A wealth of astrophysical and cosmological observational evidence shows that the matter content of the universe is made of about 85$\%$ of non-baryonic dark matter. Huge experimental efforts have been deployed to look for the direct detection of dark matter via their scattering on target nucleons, their production in colliders, and their indirect detection via their annihilation products. Inelastic scattering of high-energy cosmic rays off dark matter particles populating the Milky Way halo would produce secondary gamma rays in the final state from the decay of the neutral pions produced in such interactions, providing a new avenue to probe dark matter properties. We compute here the sensitivity for H.E.S.S.-like observatory, a current-generation ground-based Cherenkov telescopes, to the expected gamma-ray flux from collisions of Galactic cosmic rays and dark matter in the center of the Milky Way. We also derive sensitivity prospects for the upcoming Cherenkov Telescope Array (CTA) and Southern Wide-field Gamma-ray Observatory (SWGO). The expected sensitivity allows us to probe a poorly-constrained range of dark matter masses so far, ranging from keV to sub-GeV, and provide complementary constraints on the dark matter-proton scattering cross section traditionally probed by deep underground direct dark matter experiments.

The diffuse supernova neutrino background (DSNB) is the constant flux of neutrinos and antineutrinos emitted by all past core collapses in the observable Universe. We study the potential to extract information on the neutrino lifetime from the upcoming observation of the DSNB flux. The DSNB flux has a unique sensitivity to neutrino nonradiative decay for $\tau / m \in \left[ 10^9, 10^{11}\right]$~s/eV. To this end, we integrate, for the first time, astrophysical uncertainties, the contribution from failed supernovae, and a three-neutrino description of neutrino nonradiative decay. We present our predictions for future detection at the running Super-Kamiokande + Gd and the upcoming Hyper-Kamiokande, JUNO, and DUNE experiments. Finally, our results show the importance of identifying the neutrino mass ordering to restrict the possible decay scenarios for the impact of nonradiative neutrino decay on the DSNB.

Upper limits and confidence intervals are a convenient way to present experimental results. With modern experiments producing more and more data, it is often necessary to reduce the volume of the results. A common approach is to take a maximum over a set of upper limits, which yields an upper limit valid for the entire set. This, however, can be very inefficient. In this paper we introduce functional upper limits and confidence intervals that allow to summarize results much more efficiently. An application to upper limits in all-sky continuous gravitational wave searches is worked out, with a method of deriving upper limits using linear programming.

GW200129 is claimed to be the first-ever observation of the spin-disk orbital precession detected with gravitational waves (GWs) from an individual binary system. However, this claim warrants a cautious evaluation because the GW event coincided with a broadband noise disturbance in LIGO Livingston caused by the 45 MHz electro-optic modulator system. In this paper, we present a state-of-the-art neural network that is able to model and mitigate the broadband noise from the LIGO Livingston interferometer. We also demonstrate that our neural network mitigates the noise better than the algorithm used by the LIGO-Virgo-KAGRA collaboration. Finally, we re-analyse GW200129 with the improved data quality and show that the evidence for precession is still observed.

In this paper, I investigate a neutral current (NC) antineutrinos scattering with neutron star (NS) matter constituents at zero temperature. The modeling of the standard matters in NS is constructed in the framework of both extended relativistic mean-field (E-RMF) and nonrelativistic Korea-IBS-Daegu-SKKU energy density functional (KIDS-EDF) models. In the E-RMF model, I use a new parameter of G3(M), which was constrained by the recent PREX II experiment measurement of neutron distribution of $^{208}\rm{Pb}$, while the KIDS-EDF models are constrained by terrestrial experiments, gravitational-wave signals, and astrophysical observations. Using both optimal and well-constrained matter models, I then calculate the antineutrino differential cross-section (ADCS) and antineutrino mean free path (AMFP) of the antineutrinos-NS matter constituents interaction using a linear response theory. One found that the AMFP for the KIDS0 and KIDSA models are smaller in comparison to the SLy4 model and the E-RMF model with the G3(M) parameter. The AMFP result of the SLy4 model is found almost similar prediction to that of the E-RMF model with the G3(M) parameter. Contributions of each nucleon to total AMFP are also presented for the G3(M) model.

A novel approach is presented for discovering PDEs that govern the motion of satellites in space. The method is based on SINDy, a data-driven technique capable of identifying the underlying dynamics of complex physical systems from time series data. SINDy is utilized to uncover PDEs that describe the laws of physics in space, which are non-deterministic and influenced by various factors such as drag or the reference area (related to the attitude of the satellite). In contrast to prior works, the physically interpretable coordinate system is maintained, and no dimensionality reduction technique is applied to the data. By training the model with multiple representative trajectories of LEO - encompassing various inclinations, eccentricities, and altitudes - and testing it with unseen orbital motion patterns, a mean error of around 140 km for the positions and 0.12 km/s for the velocities is achieved. The method offers the advantage of delivering interpretable, accurate, and complex models of orbital motion that can be employed for propagation or as inputs to predictive models for other variables of interest, such as atmospheric drag or the probability of collision in an encounter with a spacecraft or space objects. In conclusion, the work demonstrates the promising potential of using SINDy to discover the equations governing the behaviour of satellites in space. The technique has been successfully applied to uncover PDEs describing the motion of satellites in LEO with high accuracy. The method possesses several advantages over traditional models, including the ability to provide physically interpretable, accurate, and complex models of orbital motion derived from high-entropy datasets. These models can be utilised for propagation or as inputs to predictive models for other variables of interest.