Papers for Monday, Jan 24 2022

We present precise abundance determinations of two near-pristine damped Ly$\alpha$ systems (DLAs) to assess the nature of the [O/Fe] ratio at [Fe/H] < -3 (i.e. <1/1000 of the solar metallicity). Prior observations indicate that the [O/Fe] ratio is consistent with a constant value, [O/Fe] ~ +0.4, when -3 < [Fe/H] < -2, but this ratio may increase when [Fe/H] < -3. In this paper, we test this picture by reporting new, high-precision [O/Fe] abundances in two of the most metal-poor DLAs currently known. We derive values of [O/Fe] = +0.50 +/- 0.10 and [O/Fe] = +0.62 +/- 0.05 for these two z ~ 3 near-pristine gas clouds. These results strengthen the idea that the [O/Fe] abundances of the most metal-poor DLAs are elevated compared to DLAs with [Fe/H] > -3. We compare the observed abundance pattern of the latter system to the nucleosynthetic yields of Population III supernovae (SNe), and find that the enrichment can be described by a (19-25) M$_{\odot}$ Population III SN that underwent a (0.9-2.4)$\times 10^{51}$ erg explosion. These high-precision measurements showcase the behaviour of [O/Fe] in the most metal-poor environments. Future high-precision measurements in new systems will contribute to a firm detection of the relationship between [O/Fe] and [Fe/H]. These data will reveal whether we are witnessing a chemical signature of enrichment from Population III stars and allow us to rule out contamination from Population II stars.

Black hole driven outflows have been observed in some dwarf galaxies with active galactic nuclei (1), and likely play a role in heating and expelling gas (thereby suppressing star formation), as they do in larger galaxies (2). The extent to which black hole outflows can trigger star formation in dwarf galaxies is unclear, because work in this area has hitherto focused on massive galaxies and the observational evidence is scarce (3,4,5). Henize 2-10 is a dwarf starburst galaxy previously reported to have a central massive black hole (6,7,8,9), though that interpretation has been disputed since some aspects of the observational evidence are also consistent with a supernova remnant (10,11). At a distance of ~9 Mpc, it presents an opportunity to resolve the central region and determine if there is evidence for a black hole outflow impacting star formation. Here we report optical observations of Henize 2-10 with a linear resolution of a few parsecs. We find a ~150 pc long ionized filament connecting the region of the black hole with a site of recent star formation. Spectroscopy reveals a sinusoid-like position-velocity structure that is well described by a simple precessing bipolar outflow. We conclude that this black hole outflow triggered the star formation.

A tidal disruption event (TDE) occurs when a star is destroyed by the strong tidal shear of a massive black hole (MBH). The accumulation of TDE observations over the last years has revealed that poststarburst galaxies are significantly overrepresented in the sample of TDE hosts. Here we address the poststarburst preference by investigating the decline of TDE rates in a Milky-Way like nuclear stellar cluster featuring either a monochromatic (1 M$\odot$) or a complete, evolved stellar mass function. In the former case, the decline of TDE rates with time is very mild, and generally up to a factor of a few in 10 Gyr. Conversely, if a complete mass function is considered, a strong TDE burst over the first 0.1-1 Gyr is followed by a considerable rate drop, by at least an order of magnitude over 10 Gyr. The decline starts after a mass segregation timescale, and it is more pronounced assuming a more top-heavy initial mass function and/or an initially denser nucleus. Our results thus suggest that the poststarburst preference can be accounted for in realistic systems featuring a complete stellar mass function, even in moderately dense galactic nuclei. Overall, our findings support the idea that starbursting galactic nuclei are characterized by a top-heavy initial mass function; we speculate that accounting for this can reconcile the discrepancy between observed and theoretically predicted TDE rates even in quiescent galaxies.

We study the long-term orbital evolution of stars around a merging massive or supermassive black-hole (BH) binary, taking into account the general relativistic effect induced by the BH spin. When the BH spin is significant compared to and misaligned with the binary orbital angular momentum, the orbital axis ($\hat{\mathbf{l}}$) of the circumbinary star can undergo significant evolution during the binary orbital decay driven by gravitational radiation. Including the spin effect of the primary (more massive) BH, we find that starting from nearly coplanar orbital orientations, the orbital axes $\hat{\mathbf{l}}$ of circumbinary stars preferentially evolve towards the spin direction after the merger of the BH binary, regardless of the initial BH spin orientation. Such alignment phenomenon, i.e., small final misalignment angle between $\hat{\mathbf{l}}$ and the spin axis of the remanent BH $\hat{\mathbf{S}}$, can be understood analytically using the principle of adiabatic invariance. For the BH binaries with extremely mass ratio ($m_2/m_1\lesssim0.01$), $\hat{\mathbf{l}}$ may experience more complicated evolution as adiabatic invariance breaks down, but the trend of alignment still works reasonably well when the initial binary spin-orbit angle is relatively small. Our result suggests that the correlation between the orientations of stellar orbits and the spin axis of the central BH could provide a potential signature of the merger history of the massive BH.

The ShapeFit compression method has been shown to be a powerful tool to gain cosmological information from galaxy power spectra in an effective, model-independent way. Here we present its performance on the blind PT challenge mock products presented in [1]. Choosing a set-up similar to that of other participants to the blind challenge we obtained $\Delta \ln\left(10^{10} A_s\right) = -0.018 \pm 0.014$, $\Delta \Omega_\mathrm{m} = 0.0039 \pm 0.0021$ and $\Delta h =-0.0009 \pm 0.0034$, remaining below $2\sigma$ deviations for a volume of $566 \left[ h^{-1}\mathrm{Gpc}\right]^3$. This corresponds to a volume 10 times larger than the volume probed by future galaxy surveys. We also present an analysis of these mocks oriented towards an actual data analysis using the full redshift evolution, using all three redshift bins $z_1 = 0.38$, $z_2=0.51$, and $z_3 = 0.61$, and exploring different set-ups to quantify the impact of choices or assumptions on noise, bias, scale range, etc. We find consistency across reasonable changes in set-up and across redshifts and that, as expected, mapping the redshift evolution of clustering helps constraining cosmological parameters within a given model.

Galactic bars are prominent dynamical structures within disk galaxies whose size, formation time, strength, and pattern speed influence the dynamical evolution of their hosts galaxies. Yet, their formation and evolution in a cosmological context is not well understood, as cosmological simulation studies have been limited by the classic trade off between simulation volume and resolution. Here we analyze barred disk galaxies in the cosmological magneto-hydrodynamical simulation TNG50 and quantitatively compare the distributions of bar size and pattern speed to those from MaNGA observations at $z=0$. TNG50 galaxies are selected to match the stellar mass and size distributions of observed galaxies, to account for observational selection effects. We find that the high-resolution of TNG50 yields bars with a wide range of pattern speeds (including those with $\geq 40~\mathrm{km}\,\mathrm{s}^{-1}$\,$\mathrm{kpc}^{-1}$) and a mean value of $\sim36~\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{kpc}$ consistent with observations within $6\,\mathrm{km}\,\mathrm{s}^{-1}$\,$\mathrm{kpc}^{-1}$, in contrast with previous lower-resolution cosmological simulations that produced bars that were too slow. We find, however, that bars in TNG50 are on average $\sim 35\%$ shorter than observed, although this discrepancy may partly reflect remaining inconsistencies in the simulation-data comparison. This leads to higher values of $\mathcal{R} = R_\mathrm{corot}/R_\mathrm{bar}$ in TNG50, but points to simulated bars being `too short' rather than `too slow'. After repeating the analysis on the lower-resolution run of the same simulation (with the same physical model), we qualitatively reproduce the results obtained in previous studies: this implies that, along with physical model variations, numerical resolution effects may explain the previously found `slowness' of simulated bars.

We present results revealing microwave pulsations produced in a model of a flaring twisted solar coronal loop, without any external oscillatory driver. Two types of oscillations are identified: slowly-decaying oscillations with a period of about 70-75s and amplitude of about 5-10% seen in loops both with and without energetic electrons, and oscillations with period of about 40s and amplitude of a few tens of percent observed only in loops with energetic electrons for about 100s after onset of fast energy release. We interpret the longer-period oscillations as the result of a standing kink mode modulating the average magnetic field strength in the loop, whilst the short-period intermittent oscillations associated with energetic electrons are likely to be produced by fast variations of the electric field which produces energetic electrons in this scenario. The slowly-decaying oscillations can explain the quasi-periodic pulsations often observed in the flaring corona.

Detection of water vapor in the atmosphere of temperate rocky exoplanets would be a major milestone on the path towards characterization of exoplanet habitability. Past modeling work has shown that cloud formation may prevent the detection of water vapor on Earth-like planets with surface oceans using the James Webb Space Telescope (JWST). Here we analyze the potential for atmospheric detection of H2O on a different class of targets: arid planets. Using transit spectrum simulations, we show that atmospheric H2O may be easier to be detected on arid planets with cold-trapped ice deposits on the surface, because such planets will not possess thick H2O cloud decks that limit the transit depth of spectral features. However, additional factors such as band overlap with CO2 and other gases, extinction by mineral dust, overlap of stellar and planetary H2O lines, and the ultimate noise floor obtainable by JWST still pose important challenges. For this reason, combination of space- and ground-based spectroscopic observations will be essential for reliable detection of H2O on rocky exoplanets in the future.

The role of relativistic jets in unbinding the stellar envelope during a supernova (SN) associated with a gamma-ray burst (GRB) is unclear. To study that, we explore observational signatures of stellar explosions that are driven by jets. We focus on the final velocity distribution of the outflow in such explosions and compare its observational imprints to SN/GRB data. We find that jet driven explosions produce an outflow with a flat distribution of energy per logarithmic scale of proper velocity. The flat distribution seems to be universal as it is independent of the jet and the progenitor properties that we explored. The velocity range of the flat distribution for typical GRB parameters is $\gamma\beta \approx 0.03-3$, where $\gamma$ is the outflow Lorentz factor and $\beta$ is its dimensionless velocity. A flat distribution is seen also for collimated choked jets where the highest outflow velocity decreases with the depth at which the jet is choked. Comparison to observations of SN/GRBs rules out jets as the sole explosion source in these events. Instead, in SN/GRB the collapsing star must deposit its energy into two channels - a quasi-spherical (or wide angle) channel and a narrowly collimated one. The former carries most of the energy and is responsible for the SN sub-relativistic ejecta while the latter carries 0.01-0.1 of the total outflow energy and is the source of the GRB. Intriguingly, the same two channels, with a similar energy ratio, were seen in the binary neutron star merger GW170817, suggesting that similar engines are at work in both phenomena.

We assess whether gravity darkening, induced by a tidal interaction during a stellar fly-by, might be sufficient to explain the Great Dimming of Betelgeuse. Adopting several simple approximations, we calculate the tidal deformation and associated gravity darkening in a close tidal encounter, as well as the reduction in the radiation flux as seen by a distant observer. We show that, in principle, the duration and degree of the resulting stellar dimming can be used to estimate the minimum pericenter separation and mass of a fly-by object, which, even if it remains undetected otherwise, might be a black hole, neutron star, or white dwarf. Our estimates show that, while such fly-by events may occur in other astrophysical scenarios, where our analysis should be applicable, they likely are not large enough to explain the Great Dimming of Betelgeuse by themselves.

Cosmic rays (CRs) at sub-TeV energies play a fundamental role in the chemical and dynamical evolution of molecular clouds, as they control the ionisation, dissociation, and excitation of H$_{2}$. Their characterisation is important both for the interpretation of observations and for the development of theoretical models. The methods used so far for estimating the CR ionisation rate ($\zeta$) in molecular clouds have several limitations due to uncertainties in the adopted chemical networks. We refine and extend the method proposed by Bialy (2020) to estimate $\zeta$ by observing rovibrational transitions of H$_{2}$ at near-infrared wavelengths, which are mainly excited by secondary CR electrons. Combining models of interstellar CR propagation and attenuation with the calculation of the expected secondary electron spectrum and updated H$_{2}$ excitation cross sections by electron collisions, we derive the intensity of the four H$_{2}$ rovibrational transitions observable in dense, cold gas: (1-0)O(2), (1-0)Q(2), (1-0)S(0), and (1-0)O(4). The proposed method allows the estimation of $\zeta$ for a given observed line intensity and H$_{2}$ column density. We are also able to deduce the shape of the low-energy CR proton spectrum impinging upon the molecular cloud. We present a look-up plot and a web-based application that can be used to constrain the low-energy spectral slope of the interstellar CR proton spectrum. We comment on the capability of the James Webb Space Telescope to detect these near-infrared H$_{2}$ lines, making it possible to derive for the first time spatial variation of $\zeta$ in dense gas. Besides the implications for the interpretation of the chemical-dynamic evolution of a molecular cloud, it will be possible to test competing models of CR propagation and attenuation in the interstellar medium, as well as compare CR spectra in different Galactic regions.

In astronomical surveys, such as the Zwicky Transient Facility (ZTF), supernovae (SNe) are relatively uncommon objects compared to other classes of variable events. Along with this scarcity, the processing of multi-band light-curves is a challenging task due to the highly irregular cadence, long time gaps, missing-values, low number of observations, etc. These issues are particularly detrimental for the analysis of transient events with SN-like light-curves. In this work, we offer three main contributions. First, based on temporal modulation and attention mechanisms, we propose a Deep Attention model called TimeModAttn to classify multi-band light-curves of different SN types, avoiding photometric or hand-crafted feature computations, missing-values assumptions, and explicit imputation and interpolation methods. Second, we propose a model for the synthetic generation of SN multi-band light-curves based on the Supernova Parametric Model (SPM). This allows us to increase the number of samples and the diversity of the cadence. The TimeModAttn model is first pre-trained using synthetic light-curves in a semi-supervised learning scheme. Then, a fine-tuning process is performed for domain adaptation. The proposed TimeModAttn model outperformed a Random Forest classifier, increasing the balanced-$F_1$score from $\approx.525$ to $\approx.596$. The TimeModAttn model also outperformed other Deep Learning models, based on Recurrent Neural Networks (RNNs), in two scenarios: late-classification and early-classification. Finally, we conduct interpretability experiments. High attention scores are obtained for observations earlier than and close to the SN brightness peaks, which are supported by an early and highly expressive learned temporal modulation.

Saturn's C ring contains multiple structures that appear to be density waves driven by time-variable anomalies in the planet's gravitational field. Semi-empirical extensions of density wave theory enable the observed wave properties to be translated into information about how the pattern speeds and amplitudes of these gravitational anomalies have changed over time. Combining these theoretical tools with wavelet-based analyses of data obtained by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft reveals a suite of structures in Saturn's gravity field with azimuthal wavenumber 3, rotation rates between 804 degrees/day and 842 degrees/day and local gravitational potential amplitudes between 30 and 150 cm^2/s^2. Some of these anomalies are transient, appearing and disappearing over the course of a few Earth years, while others persist for decades. Most of these persistent patterns appear to have roughly constant pattern speeds, but there is at least one structure in the planet's gravitational field whose rotation rate steadily increased between 1970 and 2010. This gravitational field structure appears to induce two different asymmetries in the planet's gravity field, one with azimuthal wavenumber 3 that rotates at roughly 810 degrees/day and another with azimuthal wavenumber 1 rotating three times faster. The atmospheric processes responsible for generating the latter pattern may involve solar tides.

Short gamma-ray bursts are believed to be produced by both binary neutron star (BNS) and neutron star-black hole (NSBH) mergers. We use current estimates for the BNS and NSBH merger rates to calculate the fraction of observable short gamma-ray bursts produced through each channel. This allows us to constrain merger rates of BNS to $\mathcal{R}_{\rm{BNS}}=384^{+431}_{-213}{\rm{Gpc}^{-3} \rm{yr}^{-1}}$ ($90\%$ credible interval), a $16\%$ decrease in the rate uncertainties from the second LIGO--Virgo Gravitational-Wave Transient Catalog, GWTC-2. Assuming a top-hat emission profile with a large Lorentz factor, we constrain the average opening angle of gamma-ray burst jets produced in BNS mergers to $\approx 15^\circ$. We also measure the fraction of BNS and NSBH mergers that produce an observable short gamma-ray burst to be $0.02^{+0.02}_{-0.01}$ and $0.01 \pm 0.01$, respectively and find that $\gtrsim 40\%$ of BNS mergers launch jets (90\% confidence). We forecast constraints for future gravitational-wave detections given different modelling assumptions, including the possibility that BNS and NSBH jets are different. With $24$ BNS and $55$ NSBH observations, expected within six months of the LIGO-Virgo-KAGRA network operating at design sensitivity, it will be possible to constrain the fraction of BNS and NSBH mergers that launch jets with $10\%$ precision. Within a year of observations, we can determine whether the jets launched in NSBH mergers have a different structure than those launched in BNS mergers and rule out whether $\gtrsim 80\%$ of binary neutron star mergers launch jets. We discuss the implications of future constraints on understanding the physics of short gamma-ray bursts and binary evolution.

Neutrinos in compact-object environments, such as core-collapse supernovae, can experience various kinds of collective effects in flavor space, engendered by neutrino-neutrino interactions. These include "bipolar" collective oscillations, which are exhibited by neutrino ensembles where different flavors dominate at different energies. Considering the importance of neutrinos in the dynamics and nucleosynthesis in these environments, it is desirable to ascertain whether an Earth-based detection could contain signatures of bipolar oscillations that occurred within a supernova envelope. To that end, we continue examining a cost-function formulation of statistical data assimilation (SDA) to infer solutions to a small-scale model of neutrino flavor transformation. SDA is an inference paradigm designed to optimize a model with sparse data. Our model consists of two mono-energetic neutrino beams with different energies emanating from a source and coherently interacting with each other and with a matter background, with time-varying interaction strengths. We attempt to infer flavor transformation histories of these beams using simulated measurements of the flavor content at locations in vacuum (that is, far from the source), which could in principle correspond to earth-based detectors. Within the scope of this small-scale model, we found that: (i) based on such measurements, the SDA procedure is able to infer \textit{whether} bipolar oscillations had occurred within the protoneutron star envelope, and (ii) if the measurements are able to sample the full amplitude of the neutrino oscillations in vacuum, then the amplitude of the prior bipolar oscillations is also well predicted. This result intimates that the inference paradigm can well complement numerical integration codes, via its ability to infer flavor evolution at physically inaccessible locations.

Inference is crucial in modern astronomical research, where hidden astrophysical features and patterns are often estimated from indirect and noisy measurements. Inferring the posterior of hidden features, conditioned on the observed measurements, is essential for understanding the uncertainty of results and downstream scientific interpretations. Traditional approaches for posterior estimation include sampling-based methods and variational inference. However, sampling-based methods are typically slow for high-dimensional inverse problems, while variational inference often lacks estimation accuracy. In this paper, we propose alpha-DPI, a deep learning framework that first learns an approximate posterior using alpha-divergence variational inference paired with a generative neural network, and then produces more accurate posterior samples through importance re-weighting of the network samples. It inherits strengths from both sampling and variational inference methods: it is fast, accurate, and scalable to high-dimensional problems. We apply our approach to two high-impact astronomical inference problems using real data: exoplanet astrometry and black hole feature extraction.

Idealized protoplanetary disk and giant planet formation models have been interpreted to suggest that a giant planet's atmospheric abundances can be used to infer its formation location in its parent protoplanetary disk. It has recently been reported that the hot Jupiter WASP-77 A b has sub-solar atmospheric carbon and oxygen abundances with a solar C/O abundance ratio. Assuming solar carbon and oxygen abundances for its host star WASP-77 A, WASP-77 A b's atmospheric carbon and oxygen abundances possibly indicate that it accreted its envelope interior to its parent protoplanetary disk's H2O ice line from carbon-depleted gas with little subsequent planetesimal accretion or core erosion. We comprehensively model WASP-77 A and use our results to better characterize WASP-77 A b. We show that the photospheric abundances of carbon and oxygen in WASP-77 A are super-solar with a sub-solar C/O abundance ratio, implying that WASP-77 A b's atmosphere has significantly sub-stellar carbon and oxygen abundances with a super-stellar C/O ratio. Our result possibly indicates that WASP-77 A b's envelope was accreted by the planet beyond its parent protoplanetary disk's H2O ice line. While numerous theoretical complications to these idealized models have now been identified, the possibility of non-solar protoplanetary disk abundance ratios confound even the most sophisticated protoplanetary disk and giant planet formation models. We therefore argue that giant planet atmospheric abundance ratios can only be meaningfully interpreted relative to the possibly non-solar mean compositions of their parent protoplanetary disks as recorded in the photospheric abundances of their solar-type dwarf host stars.

Following the discovery of the first exoplanet candidate transiting a white dwarf (WD), a "white dwarf opportunity" for characterizing the atmospheres of terrestrial exoplanets around WDs is emerging. Large planet-to-star size ratios and hence large transit depths make transiting WD exoplanets favorable targets for transmission spectroscopy - conclusive detection of spectral features on an Earth-like planet transiting a close-by WD can be achieved within a medium James Webb Space Telescope (JWST) program. Despite the apparently promising opportunity, however, the post-main sequence (MS) evolutionary history of a first-generation WD exoplanet has never been incorporated in atmospheric modeling. Furthermore, second-generation planets formed in WD debris disks have never been studied from a photochemical perspective. We demonstrate that transmission spectroscopy can identify a second-generation rocky WD exoplanet with a thick ($\sim1$ bar) H$_2$-dominated atmosphere. In addition, we can infer outgassing activities of a WD exoplanet based on its transmission spectra and test photochemical runaway by studying CH$_4$ buildup.

We compile a sample of 92 active galactic nuclei (AGNs) at z<0.75 with $gri$ photometric light curves from the archival data of the Zwicky Transient Facility and measure the accretion disk sizes via continuum reverberation mapping. We employ Monte Carlo simulation tests to assess the influences of data sampling and broad emission lines and select out the sample with adequately high sampling cadences (3 days apart in average) and minimum contaminations of broad emission lines. The inter-band time delays of individual AGNs are calculated using the interpolated cross-correlation function and then these delays are fitted with a generalized accretion disk model, in which inter-band time delays are a power function of wavelength, black hole mass, and luminosity. A Markov-chain Monte Carlo method is adopted to determine the best parameter values. Overall the inter-band time delays can be fitted with the $\tau \ \propto \lambda^{4/3}$ relation as predicted from a steady-state, optically thick, geometrically thin accretion disk, however, the yielded disk size is systematically larger than expected, although the ratio of the measured to theoretical disk sizes depend on using the emissivity -- or responsivity -- weighted disk radius. These results are broadly consistent with previous studies, all together raising a puzzle about the "standard" accretion disk model.

We built the first-ever statistically significant sample of ~80,000 background quasar-foreground cluster pairs to study the cool, metal-rich gas in the outskirts (>R500) of z~0.5 clusters with a median mass of ~10^14.2 M_sun. The sample was obtained by cross-matching the SDSS cluster catalog of Wen & Han (2015) and SDSS quasar catalog of Lyke et al. (2020). The median impact parameter (rho_cl) of the clusters from the quasar sightlines is 2.4 Mpc (median rho_cl/R500 = 3.6). A strong MgII, along with marginal FeII, absorption is detected in the mean and median stacked spectra of the quasars with MgII rest-frame equivalent widths (REWs) of 0.034\pm0.003A (11-sig) and 0.010\pm0.002A (5-sig), respectively. The MgII REW shows a declining trend with increasing rho_cl and rho_cl/R500, but does not show any significant trend with mass (M500) or redshift (zcl) within the small M500 and zcl ranges probed here. The MgII absorption signal and the trends persist even if we exclude the quasar-cluster pairs where the background quasars may be probing the circum-galactic medium (CGM) of clusters' member galaxies. The MgII (and FeII) absorption reported here is the first detection of its kind. It indicates the presence of a cool, metal-rich gas reservoir surrounding galaxy clusters out to several R500. We suggest that the metal-rich gas in the cluster outskirts arise from stripped materials and that gas stripping becomes important out to large clustocentric distances (> 3R500).

The IllustrisTNG simulations reproduce well the observed scaling relation between specific angular momentum (sAM) $j_{\rm s}$ and mass $M_{\rm s}$ of galaxies, i.e., the $j_{\rm s}$-$M_{\rm s}$ relation. This relation develops in disk galaxies at redshift $z\lesssim 1$ via forming disk structures whose sAM are nearly conserved from their parent dark matter halos. We provide a simple model that describes well the connection between halos and galaxies, giving ${\rm log} j_{\rm s} = 0.54\ {\rm log} M_{\rm s} - 2.53 + b$, where $b$ quantifies how well sAM is retained. This model suggests that the power-law index 0.54 of the $j_{\rm s}$-$M_{\rm s}$ relation is determined by (i) the change of the halo angular momentum-mass relation $j \propto M^{\alpha}$, whose index $\alpha$ grows from 0.68 to 0.80 under the effect of baryonic processes, and (ii) the mass dependence of the luminous-dark mass ratio. This model is different from the traditional expectation using a constant luminous-dark mass ratio and $\alpha=2/3$. We further suggest that a significant loss of sAM, which manifests as a decrease in $b$, leads to the parallel offset of elliptical galaxies (relative to disk galaxies) in the $j_{\rm s}$-$M_{\rm s}$ relation.

During the last 20 years, TeV astronomy turned from a fledgling field, with only a handful of sources into a fully-developed astronomy discipline, broadening our knowledge on a variety of types of TeV gamma-ray sources. This progress has been mainly achieved due to currently operating instruments: Imaging Atmospheric Cherenkov Telescopes, Surface Array and Water Cherenkov detectors. Moreover, we are at the brink of a next generation of instruments, with a considerable leap of performance parameters. This review summarises the current status of the TeV astronomy instrumentation, mainly focusing on the comparison of the different types of instruments and analysis challenges, as well as provides an outlook into the future installations. The capabilities and limitations of different techniques of observations of TeV gamma rays are discussed, as well as synergies to other bands and messengers.

Recent work has shown that NIR Hubble Space Telescope (HST) photometry allows us to disentangle multiple populations (MPs) among M dwarfs of globular clusters (GCs) and investigate this phenomenon in very low-mass (VLM) stars. Here, we present the color-magnitude diagrams (CMDs) of nine GCs and the open cluster NGC 6791 in the F110W and F160W bands of HST, showing that the main sequences (MSs) below the knee are either broadened or split thus providing evidence of MPs among VLM stars. In contrast, the MS of NGC 6791 is consistent with a single population. The color distribution of M-dwarfs dramatically changes between different GCs and the color width correlates with the cluster mass. We conclude that the MP ubiquity, variety, and dependence on GC mass are properties common to VLM and more-massive stars. We combined UV, optical, and NIR observations of NGC 2808 and NGC 6121 (M 4) to identify MPs along with a wide range of stellar masses (~ 0.2 - 0.8M ), from the MS turn off to the VLM regime, and measured, for the first time, their mass functions (MFs). We find that the fraction of MPs does not depend on the stellar mass and that their MFs have similar slopes. These findings indicate that the properties of MPs do not depend on stellar mass. In a scenario where the second generations formed in higher-density environments than the first generations, the possibility that the MPs formed with the same initial MF would suggest that it does not depend on the environment.

Based on the field theory of density fluctuation under Newtonian gravity, we obtain analytically the nonlinear equation of 3-pt correlation function $\zeta$ of galaxies in a homogeneous, isotropic, static universe. The density fluctuations have been kept up to second order. By the Fry-Peebles ansatz and the Groth-Peebles ansatz, the equation of $\zeta$ becomes closed and differs from the Gaussian approximate equation. Using the boundary condition inferred from the data of SDSS, we obtain the solution $\zeta(r, u, \theta)$ at fixed $u=2$, which exhibits a shallow $U$-shape along the angle $\theta$ and, nevertheless, decreases monotonously along the radial $r$. We show its difference with the Gaussian solution. As a direct criterion of non-Gaussianity, the reduced $Q(r, u, \theta)$ deviates from the Gaussianity plane $Q=1$, exhibits a deeper $U$-shape along $\theta$ and varies weakly along $r$, agreeing with the observed data.

We present a grid of stellar models at super-solar metallicity (Z = 0.020) extending the previous grids of Geneva models at solar and sub-solar metallicities. A metallicity of Z = 0.020 was chosen to match that of the inner Galactic disk. A modest increase of 43% (=0.02/0.014) in metallicity compared to solar models means that the models evolve similarly to solar models but with slightly larger mass loss. Mass loss limits the final total masses of the super-solar models to 35 M$_\odot$ even for stars with initial masses much larger than 100 M$_\odot$. Mass loss is strong enough in stars above 20 M$_\odot$ for rotating stars (25 M$_\odot$ for non-rotating stars) to remove the entire hydrogen-rich envelope. Our models thus predict SNII below 20 M$_\odot$ for rotating stars (25 M$_\odot$ for non-rotating stars) and SNIb (possibly SNIc) above that. We computed both isochrones and synthetic clusters to compare our super-solar models to the Westerlund 1 (Wd1) massive young cluster. A synthetic cluster combining rotating and non-rotating models with an age spread between log10 (age/yr) = 6.7 and 7.0 is able to reproduce qualitatively the observed populations of WR, RSG and YSG stars in Wd1, in particular their simultaneous presence at log10(L/L$_\odot$) = 5-5.5. The quantitative agreement is imperfect and we discuss the likely causes: synthetic cluster parameters, binary interactions, mass loss and their related uncertainties. In particular, mass loss in the cool part of the HRD plays a key role.

Coalescing supermassive black hole binaries (BHBs) are expected to be the loudest sources of gravitational waves (GWs) in the Universe. Detection rates for ground or space-based detectors based on cosmological simulations and semi-analytic models are highly uncertain. A major difficulty stems from the necessity to model the BHB from the scale of the merger to that of inspiral. Of particular relevance to the GW merger timescale is the binary eccentricity. Here we present a self-consistent numerical study of the eccentricity of BHBs formed in massive gas-free mergers from the early stages of the merger to the hardening phase, followed by a semi-analytical model down to coalescence. We find that the early eccentricity of the unbound black hole pair is largely determined by the initial orbit. It systematically decreases during the dynamical friction phase. The eccentricity at binary formation is affected by stochasticity and noise owing to encounters with stars, but preserves a strong correlation with the initial orbital eccentricity. Binding of the black holes is a phase characterised by strong perturbations, and we present a quantitative definition of the time of binary formation. During hardening the eccentricity increases in minor mergers, unless the binary is approximately circular, but remains largely unchanged in major mergers, in agreement with predictions from semi-analytical models based on isotropic scattering experiments. Coalescence times due to hardening and GW emission in gas-poor non-rotating ellipticals are <~0.5 Gyr for the large initial eccentricities (0.5 < e < 0.9) typical of galaxy mergers in cosmological simulations.

This is a review article for The Review of Particle Physics 2022 (aka the Particle Data Book). It forms a compact review of knowledge of the cosmological parameters near the end of 2021. Topics included are Parametrizing the Universe; Extensions to the standard model; Probes; Bringing observations together; Outlook for the future.

Be stars are found to rotate close to their critical rotation and therefore they are considered as an important laboratory of study for stellar rotation. In this context, we obtain the projected rotational velocity of a sample of classical Be Southern stars in the BeSOS database via Fourier Transform in an automated way for several absorption lines at different epochs. A Gaussian profile is fitted to eight observed photospheric HeI lines in order to select automatically the spectral signal given by areas under the curve of 95.45%, 98.75% and 99.83% from the profile to obtain $v \sin i$ via Fourier Transform technique. The values obtained are in global agreement with the literature. Analysing only one line is not enough to set the $v \sin i$ value, depending on the line the value in most cases are underestimated with respect to $\lambda$4471. When gravity darkening effects are including, apparent values increases by $\sim10$%. The resolution of the instrument PUCHEROS used for BeSOS spectra ($R \sim 17\,000$) constrain a theoretical lower bound possible at $v \sin i \sim 100$ km s$^{-1}$. The procedure has limitations using a linear limb-darkening function with $\varepsilon = 0.6$ for classical Be stars rotating close to the break-up velocity without gravity-darkening corrections, which can't be negligible. Previous works measure $v \ sin i$ values using just one spectral line and here we demonstrate that with more lines the results can varies. This could be due to the photospheric distribution of atomic transitions on classical Be stars.

Recent computations of the interior composition of ultra-massive white dwarfs (WD) have suggested that some white dwarfs could be composed of neon (Ne)-dominated cores. This result is at variance with our previous understanding of the chemical structure of massive white dwarfs, where oxygen is the predominant element. In addition, it is not clear whether some hybrid carbon (C) oxygen (O)-Ne white dwarfs might form when convective boundary mixing is accounted for during the propagation of the C-flame, in the C-burning stage. Both Ne-dominated and hybrid CO-Ne core would have measurable consequences for asteroseismological studies based on evolutionary models. In this work we explore in detail to which extent differences in the adopted micro- and macro-physics can explain the different final white dwarf compositions that have been found by different authors. Additionally, we explored the impact of such differences in the cooling times, crystallization and pulsational properties of pulsating WDs. We explore the impact of the intensity of convective boundary mixing during the C-flash, extreme mass-loss rates, and the size of the adopted nuclear networks on the final composition, age, crystallization and pulsational properties of white dwarfs. Based on the insight coming from 3D hydro-dynamical simulations, we expect that the very slow propagation of the carbon flame will be altered by turbulent entrainment affecting the inward propagation of the flame. Also, we find that Ne-dominated chemical profiles of massive WDs recently reported appear in their modeling due to the overlooking of a key nuclear reaction. We find that the inaccuracies in the chemical composition of ultra-massive white dwarfs recently reported lead to differences of 10% in the cooling times and degree of crystallization and about 8% in the period spacing of the models once they reach the ZZ Ceti instability strip.

M105 is an early-type galaxy in the nearby Leo I group, the closest galaxy group to contain all galaxy types and therefore an excellent environment to explore the low-mass end of intra-group light (IGL) assembly. We present a new extended kinematic survey of planetary nebulae (PNe) in M105 and the surrounding 30'x30' in the Leo I group with the Planetary Nebula Spectrograph. We use PNe as kinematic tracers of the diffuse stellar light in the halo and IGL and employ Gaussian mixture models to separate contributions from the companion galaxy NGC 3384 and associate PNe with halo and IGL components around M105. We present a catalogue of 314 PNe and firmly associate 93 with NGC 3384 and 169 with M105. The PNe in M105 are further associated with its halo and the surrounding exponential envelope. We construct smooth velocity and velocity dispersion fields and calculate projected rotation, velocity dispersion, and $\lambda_R$ profiles for each component. Halo PNe exhibit declining velocity dispersion and rotation profiles, while the velocity dispersion and rotation of the exponential envelope increase notably at large radii. We identify three regimes with distinct kinematics that are linked to distinct stellar population properties: (i) the rotating core (within $1~R_\mathrm{eff}$) formed in situ and dominated by metal-rich ([M/H]~0) stars likely formed in situ, (ii) the halo from 1 to $7.5~R_\mathrm{eff}$ consisting of intermediate-metallicity stars ([M/H]>-1), either formed in situ or brought in through major mergers, and (iii) the exponential envelope reaching beyond our farthest data point at 16 $R_\mathrm{eff}$, predominately composed of metal-poor ([M/H]<-1) stars. The high velocity dispersion and moderate rotation of the latter are consistent with that measured for dwarf satellite galaxies in the Leo I group, indicating that the exponential envelope traces the transition to the IGL.

The carbon footprint of astronomical research is an increasingly topical issue with first estimates of research institute and national community footprints having recently been published. As these assessments have typically excluded the contribution of astronomical research infrastructures, we complement these studies by providing an estimate of the contribution of astronomical space missions and ground-based observatories using greenhouse gas emission factors that relate cost and payload mass to carbon footprint. We find that currently worldwide active astronomical research infrastructures have a carbon footprint of $20.3\pm3.3$ Mt CO$_2$e and an annual emission of $1169\pm249$ kt CO$_2$e / yr, corresponding to a footprint of $36.6\pm14.0$ t CO$_2$e / yr per astronomer. Compared to contributions from other aspects of astronomy research activity, our results suggest that research infrastructures make the single largest contribution to the carbon footprint of an astronomer. We discuss the limitations and uncertainties of our method, and explore measures that can bring greenhouse gas emissions from astronomical research infrastructures towards a sustainable level.

The advancement in the field of data science especially in machine learning along with vast databases of variable star projects like the Optical Gravitational Lensing Experiment (OGLE) encourages researchers to analyse as well as classify light curves of different variable stars automatically with efficiency. In the present work, we have demonstrated the relative performances of principal component analysis (PCA) and independent component analysis (ICA) applying to huge databases of OGLE variable star light curves after obtaining 1000 magnitudes between phase 0 to 1 with step length 0.001 for each light curves in identifying resonances for fundamental mode (FU) and first overtone (FO) Cepheids and in the classification of variable stars for Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC) as well as Milky Way (MW). We have seen that the performance of ICA is better for finding resonances for Cepheid variables as well as for accurately classifying large data sets of light curves than PCA. Using K-means clustering algorithm (CA) with respect to independent components (ICs), we have plotted period-luminosity diagrams and colour-magnitude diagrams separately for LMC, SMC and MW and found that ICA along with K-means CA is a very robust tool for classification as well as future prediction on the nature of light curves of variable stars.

Understanding the relationship between the cosmic web and the gas content of galaxies is a key step towards understanding galaxy evolution. However, the impact of the cosmic web on the growth of galaxies and dark matter halos is not yet properly understood. We report a detection of the effect of the cosmic web on the galaxy stellar mass - gas phase metallicity relation of low redshift star-forming galaxies, using SDSS data. The proximity of a galaxy to a node, independently of stellar mass and overdensity, influences its gas-phase metallicity, with galaxies closer to nodes displaying higher chemical enrichment than those further away. We find a similar but significantly weaker effect with respect to filaments. We supplement our observational analysis with a study of the cosmological hydrodynamical simulation IllustrisTNG (TNG300), finding qualitative agreement with our results. Using IllustrisTNG, our results can be explained by both halo assembly bias and gas supply combining in nodes in a way that significantly modulates the metallicity of the gas, contributing to the scatter of this fundamental relation in galaxy evolution.

Ultra-hot Jupiters (UHJs) are gas giants with very high equilibrium temperatures. In recent years, multiple chemical species, including various atoms and ions, have been discovered in their atmospheres. Most of these observations have been performed with transmission spectroscopy, although UHJs are also ideal targets for emission spectroscopy due to their strong thermal radiation. We present high-resolution thermal emission spectroscopy of the transiting UHJ KELT-20b/MASCARA-2b. The observation was performed with the CARMENES spectrograph at orbital phases before and after the secondary eclipse. We detected atomic Fe using the cross-correlation technique. The detected Fe lines are in emission, which unambiguously indicates a temperature inversion on the dayside hemisphere. We furthermore retrieved the temperature structure with the detected Fe lines. The result shows that the atmosphere has a strong temperature inversion with a temperature of $4900\pm{700}$ K and a pressure of $10^{-4.8_{-1.1}^{+1.0}}$ bar at the upper layer of the inversion. A joint retrieval of the CARMENES data and the TESS secondary eclipse data returns a temperature of $2550_{-250}^{+150}$ K and a pressure of $10^{-1.5_{-0.6}^{+0.7}}$ bar at the lower layer of the temperature inversion. The detection of such a strong temperature inversion is consistent with theoretical simulations that predict an inversion layer on the dayside of UHJs. The joint retrieval of the CARMENES and TESS data demonstrates the power of combing high-resolution emission spectroscopy with secondary eclipse photometry in characterizing atmospheric temperature structures.

Young massive stars play an important role in the evolution of the interstellar medium (ISM) and the self-regulation of star formation in giant molecular clouds (GMCs) by injecting energy, momentum, and radiation (stellar feedback) into surrounding environments, disrupting the parental clouds, and regulating further star formation. Information of the stellar feedback inheres in the emission we observe, however inferring the physical properties from photometric and spectroscopic measurements is difficult, because stellar feedback is a highly complex and non-linear process, so that the observational data are highly degenerate. On this account, we introduce a novel method that couples a conditional invertible neural network (cINN) with the WARPFIELD-emission predictor (WARPFIELD-EMP) to estimate the physical properties of star-forming regions from spectral observations. We present a cINN that predicts the posterior distribution of seven physical parameters (cloud mass, star formation efficiency, cloud density, cloud age which means age of the first generation stars, age of the youngest cluster, the number of clusters, and the evolutionary phase of the cloud) from the luminosity of 12 optical emission lines, and test our network with synthetic models that are not used during training. Our network is a powerful and time-efficient tool that can accurately predict each parameter, although degeneracy sometimes remains in the posterior estimates of the number of clusters. We validate the posteriors estimated by the network and confirm that they are consistent with the input observations. We also evaluate the influence of observational uncertainties on the network performance.

Super-Eddington accretion is one scenario that may explain the rapid assembly of $\sim 10^9\rm\, M_\odot$ supermassive black holes (BHs) within the first billion year of the Universe. This critical regime is associated with radiatively inefficient accretion and accompanied by powerful outflows in the form of winds and jets. By means of hydrodynamical simulations of BH evolution in an isolated galaxy and its host halo with 12 pc resolution, we investigate how super-Eddington feedback affects the mass growth of the BH. It is shown that super-Eddington feedback efficiently prevents BH growth within a few Myr. The super-Eddington accretion events remain relatively mild with typical rates of about 2-3 times the Eddington limit, because of the efficient regulation by jets in that regime. We find that these jets are powerful enough to eject gas from the centre of the host galaxy all the way up to galactic scales at a few kpc, but do not significantly impact gas inflows at those large scales. By varying the jet feedback efficiency, we find that weaker super-Eddington jets allow for more significant BH growth through more frequent episodes of super-Eddington accretion. We conclude that effective super-Eddington growth is possible, as we find that simulations with weak jet feedback efficiencies provide a slightly larger BH mass evolution over long periods of time ($\sim 80\,\rm Myr$) than that for a BH accreting at the Eddington limit.

NGC 7789 is a $\sim$1.6 Gyr old, populous open cluster located at $\sim$2000 pc. We characterize the blue straggler stars (BSS) of this cluster using the Ultraviolet (UV) data from the UVIT/AstroSat. We present spectral energy distributions (SED) of 15 BSS candidates constructed using multi-wavelength data ranging from UV to IR wavelengths. In 8 BSS candidates, a single temperature SED is found to be satisfactory. We discover hot companions in 5 BSS candidates. The hot companions with Teff $\sim$11750-15500 K, R $\sim$0.069-0.242 R$_{\odot}$, and L $\sim$0.25-1.55 L$_{\odot}$, are most likely extremely low mass (ELM) white dwarfs (WDs) with masses smaller than $\sim$0.18 M$_{\odot}$, and thereby confirmed post mass transfer systems. We discuss the implication of this finding in the context of BSS formation mechanisms. Two additional BSS show excess in one or more UV filters, and may have a hot companion, however, we are unable to characterize them. We suggest that at least 5 of the 15 BSS candidates (33%) studied in this cluster have formed via the mass transfer mechanism.

In September 2021 the magnetar SGR J1935+2154 entered a stage of burst/flaring activity in the hard X-ray band. On September 10, 2021 we observed SGR J1935+2154 with the fiber-fed fast optical photon counter IFI+Iqueye, mounted at the 1.22 m Galileo telescope in Asiago. During one of the IFI+Iqueye observing windows a hard X-ray burst was detected with the Fermi Gamma-ray Burst Monitor. We performed a search for any significant increase in the count rate on the 1-s, 10-ms and 1-ms binned IFI+Iqueye light curves around the time of the Fermi burst. No significant peak was detected with a significance above 3$\sigma$ in an interval of $\pm$90 s around the burst. Correcting for interstellar extinction ($A_V \simeq 5.8$ mag), the IFI+Iqueye upper limits to any possible optical burst from SGR J1935+2154 are $V=10.1$ mag, $V=7.2$ mag and $V=5.8$ mag for the 1-s, 10-ms and 1-ms binned light curves, respectively. The corresponding extinction corrected upper limits to the fluence (specific fluence) are $3.1 \times 10^{-10}$ erg cm$^{-2}$ (0.35 Jy s), $4.2 \times 10^{-11}$ erg cm$^{-2}$ (4.8 Jy $\cdot$ 10 ms), and $1.6 \times 10^{-11}$ erg cm$^{-2}$ (17.9 Jy ms), orders of magnitude deeper than any previous simultaneous optical limit on a magnetar burst. The IFI+Iqueye measurement can also place a more stringent constraint to the spectral index of the optical to hard X-ray fluence of SGR J1935+2154, implying a spectrum steeper than $\nu^{0.64}$. Fast optical timing observations of bursts associated with radio emission have then the potential to yield a detection.

We investigate the sensitivity of the Laser Interferometer Space Antenna (LISA) to the anisotropies of the Stochastic Gravitational Wave Background (SGWB). We first discuss the main astrophysical and cosmological sources of SGWB which are characterized by anisotropies in the GW energy density, and we build a Signal-to-Noise estimator to quantify the sensitivity of LISA to different multipoles. We then perform a Fisher matrix analysis of the prospects of detectability of anisotropic features with LISA for individual multipoles, focusing on a SGWB with a power-law frequency profile. We compute the noise angular spectrum taking into account the specific scan strategy of the LISA detector. We analyze the case of the kinematic dipole and quadrupole generated by Doppler boosting an isotropic SGWB. We find that $\beta\, \Omega_{\rm GW}\sim 2\times 10^{-11}$ is required to observe a dipolar signal with LISA. The detector response to the quadrupole has a factor $\sim 10^3 \,\beta$ relative to that of the dipole. The characterization of the anisotropies, both from a theoretical perspective and from a map-making point of view, allows us to extract information that can be used to understand the origin of the SGWB, and to discriminate among distinct superimposed SGWB sources.

The spotted detached eclipsing binary (DEB) offers insights into starspots on the binary. Three spotted DEBs, KIC 8097825, KIC 6859813, and KIC 5527172, which were observed by the Kepler photometry and LAMOST spectroscopy, are studied in this work. The physical parameters of binaries are determined by binary modeling. The sizes, lifetimes, and single/double-dip ratio (SDR) of starspots are derived by starspot analysis. KIC 8097825 has large starspots. KIC 6859813 has a spot rotation period shorter than its orbital period but the system should be synchronized inferred from timescale estimation. The difference may be the result of the surface differential rotation. The KIC 5527172 has a long spot lifetime and an M dwarf component with an inflation radius. The primaries of these binaries and the secondary of KIC 8097825 have spots. Adding spotted DEBs of literature, we compare the starspots on binaries with those on the single stars. The spot sizes of starspots on 65% binaries are smaller than the median of those on single stars. The lifetimes of starspots on binaries are consistent with those on single stars when the rotation periods are larger than 3 days. SDRs for half of the binaries are consistent with those of single star systems, while another half are smaller. The relative lifetime positively correlates with the RMS and SDR but negatively correlates with the rotation period. These relations are similar to those of spots on the single star systems. Binaries with luminosity ratios close to the unit tend to have more double dips.

The upcoming deployment of JWST will dramatically advance our ability to characterize exoplanet atmospheres, both in terms of precision and sensitivity to smaller and cooler planets. Disequilibrium chemical processes dominate these cooler atmospheres, requiring accurate photochemical modeling of such environments. The host star's UV spectrum is a critical input to these models, but most exoplanet hosts lack UV observations. For cases in which the host UV spectrum is unavailable, a reconstructed or proxy spectrum will need to be used in its place. In this study, we use the MUSCLES catalog and UV line scaling relations to understand how well reconstructed host star spectra reproduce photochemically modeled atmospheres using real UV observations. We focus on two cases; a modern Earth-like atmosphere and an Archean Earth-like atmosphere that forms copious hydrocarbon hazes. We find that modern Earth-like environments are well-reproduced with UV reconstructions, whereas hazy (Archean Earth) atmospheres suffer from changes at the observable level. Specifically, both the stellar UV emission lines and the UV continuum significantly influence the chemical state and haze production in our modeled Archean atmospheres, resulting in observable differences in their transmission spectra. Our modeling results indicate that UV observations of individual exoplanet host stars are needed to accurately characterize and predict the transmission spectra of hazy terrestrial atmospheres. In the absence of UV data, reconstructed spectra that account for both UV emission lines and continuum are the next best option, albeit at the cost of modeling accuracy.

The TRAPPIST-1 system is an iconic planetary system in various aspects (e.g., habitability, resonant relation, and multiplicity) and hence has attracted considerable attention. The mass distribution of the TRAPPIST-1 planets is characterized by two features: the two inner planets are large, and the masses of the four planets in the outer orbit increase with orbital distance. The origin of these features cannot be explained by previous formation models. We investigate whether the mass distribution of the TRAPPIST-1 system can be reproduced by a planet formation model using N-body simulations. We used a gas disk evolution model around a low-mass star constructed by considering disk winds and followed the growth and orbital migration from planetary embryos with the isolation mass, which increases with orbital distance. As a result, we find that from the initial phase, planets in inner orbits undergo rapid orbital migration, and the coalescence growth near the inner disk edge is enhanced. This allows the inner planets to grow larger. Meanwhile, compared with the inner planets, planets in outer orbits migrate more slowly and do not frequently collide with neighboring planets. Therefore, the trend of increasing mass toward the outer orbit, called reversed mass ranking, is maintained. The final mass distribution approximately agrees with the two features of the mass distribution in the TRAPPIST-1 system. We discover that the mass distribution in the TRAPPIST-1 system can be reproduced when embryos experience rapid migration and become trapped near the disk inner edge, and then more massive embryos undergo slower migration. This migration transition can be achieved naturally in a disk evolution model with disk winds.

We numerically and analytically explore the background cosmological dynamics of multifield dark energy with highly non-geodesic or "spinning" field-space trajectories. These extensions of standard single-field quintessence possess appealing theoretical features and observable differences from the cosmological standard model. At the level of the cosmological background, we perform a phase-space analysis and identify approximate attractors with late-time acceleration for a wide range of initial conditions. Focusing on two classes of field-space geometry, we derive bounds on parameter space by demanding viable late-time acceleration and the absence of gradient instabilities, as well as from the de Sitter swampland conjecture.

The late-time effect of primordial non-Gaussianity offers a window into the physics of inflation and the very early Universe. In this work we study the consequences of a particular class of primordial non-Gaussianity that is fully characterized by initial density fluctuations drawn from a non-Gaussian probability density function, rather than by construction of a particular form for the primordial bispectrum. We numerically generate multiple realisations of cosmological structure and use the late-time matter power spectrum, bispectrum and trispectrum to determine the effect of these modified initial conditions. We show that the initial non-Gaussianity has only a small imprint on the first three polyspectra, when compared to a standard Gaussian cosmology. Furthermore, some of our models present an interesting scale-dependent deviation from the Gaussian case in the bispectrum and trispectrum, although the signal is at most at the percent level. The majority of our models are consistent with CMB constraints on the trispectrum, while the others are only marginally excluded. Finally, we discuss further possible extensions of our study.

We investigate tomography of 21-cm brightness temperature fluctuations during the Dark Ages as a probe for constraining primordial non-Gaussianity. We expand the 21- cm brightness temperature up to cubic order in perturbation theory and improve previous models of the signal by including the effect of the free electron fraction. Using modified standard perturbation theory methods that include baryonic pressure effects we derive an improved secondary bispectrum and for the first time derive the secondary trispectrum of 21-cm brightness temperature fluctuations. We then forecast the amount of information available from the Dark Ages to constrain primordial non-Gaussianity, including the imprints of massive particle exchange during inflation and we determine how much signal is lost due to secondary non-Gaussianity. We find that although secondary non-Gaussianity swamps the primordial signal, primordial non-Gaussianity can still be extracted with signal-to-noise ratios that surpass current and future CMB experiments by several orders of magnitude, depending on the experimental setup. Furthermore, we conclude that for the bi- and trispectra of massive particle exchange marginalizing over other primordial shapes affects signal-to-noise ratios more severely than secondary shapes. Baryonic pressure effects turn out to have a negligible impact on our forecasts, even at scales close to the Jeans scale. The results of this work reinforce the prospects of 21-cm brightness temperature fluctuations from the Dark Ages as the ultimate probe for primordial non-Gaussianity.

We calculate the Bayesian evidences for a class of Ekpyrotic universe models, and compare with a model of single field inflation with a Higgs-type potential. Combining parsimony and observational constraints, this gives us a systematic way to evaluate the degree to which Ekpyrotic models are constrained by CMB data from Planck. We integrate the equations of motion numerically to define a likelihood using Planck 2018 data and sample this likelihood to obtain Bayesian evidences. Priors are justified and used to put Ekpyrotic models and inflation on equal footing. We find reasonable preference for one of the considered Ekpyrotic models over the others, but that even this one is disfavored compared with Higgs inflation.

The holographic principle suggests that the Hilbert space of quantum gravity is locally finite-dimensional. Motivated by this point-of-view, and its application to the observable universe, we introduce a set of numerical and conceptual tools to describe scalar fields with finite-dimensional Hilbert spaces, and to study their behaviour in expanding cosmological backgrounds. These tools include accurate approximations to compute the vacuum energy of a field mode $\bm{k}$ as a function of the dimension $d_{\bm{k}}$ of the mode Hilbert space, as well as a parametric model for how that dimension varies with $|\bm{k}|$. We show that the maximum entropy of our construction momentarily scales like the boundary area of the observable Universe for some values of the parameters of that model. And we find that the maximum entropy generally follows a sub-volume scaling as long as $d_{\bm{k}}$ decreases with $|\bm{k}|$. We also demonstrate - in our fiducial construction - that the vacuum energy density of the finite-dimensional field becomes dynamical in some regions of parameter space, decaying between two constant epochs. These results rely on a number of non-trivial modelling choices, but our general framework may serve as a starting point for future investigations of the impact of finite-dimensionality of Hilbert space on cosmological physics.

High-level Chinese cartographic developments predate European innovations by several centuries. Whereas European cartographic progress -- and in particular the search for a practical solution to the perennial "longitude problem" at sea -- was driven by persistent economic motivations, Chinese mapmaking efforts responded predominantly to administrative, cadastral and topographic needs. Nevertheless, contemporary Chinese scholars and navigators, to some extent aided by experienced Arab navigators and astronomers, developed independent means of longitude determination both on land and at sea, using a combination of astronomical observations and timekeeping devices that continued to operate adequately on pitching and rolling ships. Despite confusing and speculative accounts in the current literature and sometimes overt nationalistic rhetoric, Chinese technical capabilities applied to longitude determination at sea, while different in design from European advances owing to cultural and societal circumstances, were at least on a par with those of their European counterparts.

We discuss the statistical distribution of the gravitational (Newtonian) force exerted on a test particle in a infinite random and homogeneous gas of non-correlated particles. The exact solution is known as the Holtsmark distribution at the limit of infinite system corresponding to the number of particle N within the volume and the volume going to infinity. The statistical behaviour of the gravitational force for scale comparable to the inter-distance particle can be analyzed through the combination of the n-th nearest neighbor particle contribution to the total gravitational force, which can be derived from the joint probability density of location for a set of N particles. We investigate two independent approaches to derive the joint probability density of location for a set of N neighbors using integral forms and order statistics to give a general expression of such probability distribution with generalised dimension of space. We found that the non-finite dispersion of the Holtsmark distribution is due to the single contribution of the first nearest neighbor in the total gravitational force.

A main issue in cosmology and astrophysics is whether the dark sector phenomenology originates from particle physics, then requiring the detection of new fundamental components, or it can be addressed by modifying General Relativity. Extended Theories of Gravity are possible candidates aimed in framing dark energy and dark matter in a comprehensive geometric view. Considering the concept of perfect scalars, we show that the field equations of such theories naturally contain perfect fluid terms. Specific examples are developed for the Friedman-Lema\^itre-Roberson-Walker metric.

This work analyses the hydrostatic equilibrium configurations of strange stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. Those stars are supposed to be made of strange quark matter, whose distribution is governed by the MIT equation of state. The non-minimal GMC theory is described by the following gravitational action: $f(R,L)=R/2+L+\sigma RL$, where $R$ represents the curvature scalar, $L$ is the matter Lagrangian density, and $\sigma$ is the coupling parameter. When considering this theory, the strange stars become larger and more massive. In particular, when $\sigma=20$, the theory can achieve the 2.6 solar mass, suitable for describing the pulsars PSR J2215+5135 and PSR J1614-2230, and the mass of the secondary object in the GW190814 event. The 2.6 $M_\odot$ is a value hardly achievable in General Relativity. The non-minimal GMC theory can also give feasible results to describe the macroscopical features of strange star candidates.

Pulsars are spinning neutron stars which emit an electromagnetic beam. We expect pulsars to slowly decrease their rotational frequency. However, sudden increases of the rotational frequency have been observed from different pulsars. These events are called "glitches" and they are followed by a relaxation phase with timescales from days to months. Gravitational wave (GW) emission may follow these peculiar events. We give an overview of the setup for an analysis of GW data from the Advanced LIGO and Virgo third observing run (O3) arXiv:2112.10990 searching for transient GW signals lasting hours to months after glitches in known pulsars. The search method consists of placing a template grid in frequency-spindown space with fixed grid spacings. Then, for each point we compute the transient F-statistic which is maximized over a set of transient parameters like the duration and start time of the potential signals. A threshold on the detection statistic is then set, and we search for peaks over the parameter space for each candidate.

We investigate the physical measurability of the infrared instability of a de Sitter phase in the formalism recently proposed by Kitamoto et al.. We find that the logarithmic decay of the effective cosmological constant is only measurable if an additional clock field is introduced.