Papers for Thursday, Jan 13 2022

We analyse the equations enabling us to follow the variations of the phase density and the gravitational potential of a star cluster. We also study the formulas necessary to calculate the encounter function. We treat the clusters as isolated, spherical, almost steady systems of many gravitating particles of constant mass. The cluster model that we use corresponds probably quite well to globular clusters. In the case of open clusters the similarity is worse and in some cases, even completely absent (very sparse clusters can not be handled as isolated).

We have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. In this paper we use X-shooter data, providing spectral coverage from $\sim 3000-25000$ Ang, of a sample of 40 red and blue luminous quasars at $1.45<z<1.65$ to explore the connections between the radio, emission-line, and accretion-disc properties. We fit various dust-extinction curves to the data and find that dust reddening can fully explain the observed colours for the majority of the red quasars in our sample, with moderate extinctions ranging from Av$\sim 0.06-0.7$ mags. We confront our spectra with a simple thin accretion-disc model and find this can describe the continua of both the blue and red quasars, once corrected for dust extinction; we also find no significant differences in the accretion properties. We detect ionized outflows in a number of red and blue quasars, but do not find any significant evidence that they are more prevalent in the red quasar population. Overall our findings imply that the radio emission is more closely connected to circumnuclear/ISM opacity rather than accretion disc or outflow differences.

The role of different stellar feedback mechanisms in giant molecular clouds is not well understood. This is especially true for regions with many interacting clouds as would be found in a galactic spiral arm. In this paper, building on previous work by Bending et al., we extract a $500\times500\times100$ pc section of a spiral arm from a galaxy simulation. We use smoothed particle hydrodynamics (SPH) to re-simulate the region at higher resolution (1 M$_\odot$ per particle). We present a method for momentum-driven stellar winds from main sequence massive stars, and include this with photoionization, self-gravity, a galactic potential, and ISM heating/cooling. We also include cluster-sink particles with accretion radii of 0.78 pc to track star/cluster formation. The feedback methods are as robust as previous models on individual cloud scales (e.g. Dale et al.). We find that photoionization dominates the disruption of the spiral arm section, with stellar winds only producing small cavities (at most $\sim$ 30 pc). Stellar winds do not affect the resulting cloud statistics or the integrated star formation rate/efficiency, unlike ionization, which produces more stars, and more clouds of higher density and higher velocity dispersion compared to the control run without feedback. Winds do affect the sink properties, distributing star formation over more low-mass sinks ($\sim 10^2$ M$_\odot$) and producing fewer high-mass sinks ($\sim 10^3$ M$_\odot$). Overall, stellar winds play at best a secondary role compared to photoionization, and on many measures, they have a negligible impact.

Tachyonic preheating is realized when the inflaton repeatedly returns to a convex region of the potential during the post-inflationary oscillating phase. This will induce a strong tachyonic instability and lead to a rapid fragmentation of the coherent field that can complete within a fraction of an $e$-fold. In this paper, we study the linear regime of this process in a model-independent way. To this purpose, we construct simplified models that provide an analytic Floquet theoretic description of mode growth. This approach captures the essential features of well-motivated tachyonic preheating scenarios, including scenarios in which the inflaton is part of a larger scalar multiplet. We show that tachyonic preheating is efficient if the field excursions are sub-Planckian, can produce gravitational waves in the frequency range of current and future gravitational wave interferometers, and can be consistent with any experimentally allowed tensor-to-scalar ratio.

We report the discovery of TOI-2180 b, a 2.8 $M_{\rm J}$ giant planet orbiting a slightly evolved G5 host star. This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified the 24 hr single-transit event shortly after the data were released, allowing a Doppler monitoring campaign with the Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined the orbital period of TOI-2180 b to be 260.8$\pm$0.6 days, revealed an orbital eccentricity of 0.368$\pm$0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period. We predict that TESS will likely detect another transit of TOI-2180 b in Sector 48 of its extended mission. We use giant planet structure models to retrieve the bulk heavy-element content of TOI-2180 b. When considered alongside other giant planets with orbital periods over 100 days, we find tentative evidence that the correlation between planet mass and metal enrichment relative to stellar is dependent on orbital properties. Single-transit discoveries like TOI-2180 b highlight the exciting potential of the TESS mission to find planets with long orbital periods and low irradiation fluxes despite the selection biases associated with the transit method.

The disk components of galaxies generally show an exponential profile extending over several scale lengths, both in mass and star-formation rate, but the physical origin is not well understood. We explore a physical model in which the galactic gas disk is viewed as a "modified accretion disk" in which coplanar gas inflow, driven by viscous stresses in the disk, provides the fuel for star formation, which progressively removes gas as it flows inwards. We show that magnetic stresses from magneto-rotational instability are the most plausible source of the required viscosity, and construct a simple physical model to explore this. A key feature is to link the magnetic field strength to the local star-formation surface density, $B_{\rm tot} \propto \Sigma_{\rm SFR}^\alpha$. This provides a feed-back loop between star-formation and the flow of gas. We find that the model naturally produces stable steady-state exponential disks, as long as $\alpha \sim$ 0.15, the value indicated from spatially-resolved observations of nearby galaxies. The disk scale-length $h_{\rm R}$ is set by the rate at which the disk is fed, by the normalization of the $B_{\rm tot}-\Sigma_{\rm SFR}$ relation and by the circular velocity of the halo. The angular momentum distribution of the gas and stars within the disk is a consequence of the transfer of angular momentum that is inherent to the operation of an accretion disk, rather than the initial angular momentum of the inflowing material. We suggest that magnetic stresses likely play a major role in establishing the stable exponential form of galactic disks.

Ionised gas kinematics provide crucial evidence of the impact that active galactic nuclei (AGN) have in regulating star formation in their host galaxies. Although the presence of outflows in AGN host galaxies has been firmly established, the calculation of outflow properties such as mass outflow rates and kinetic energy remains challenging. We present the [OIII]5007 ionised gas outflow properties of 22 z$<$0.1 X-ray AGN, derived from the BAT AGN Spectroscopic Survey using MUSE/VLT. With an average spatial resolution of 1" (0.1-1.2 kpc), the observations resolve the ionised gas clouds down to sub-kiloparsec scales. Resolved maps show that the [OIII] velocity dispersion is, on average, higher in regions ionised by the AGN, compared to star formation. We calculate the instantaneous outflow rates in individual MUSE spaxels by constructing resolved mass outflow rate maps, incorporating variable outflow density and velocity. We compare the instantaneous values with time-averaged outflow rates by placing mock fibres and slits on the MUSE field-of-view, a method often used in the literature. The instantaneous outflow rates (0.2-275 $M_{\odot}$ yr$^{-1}$) tend to be 2 orders of magnitude higher than the time-averaged outflow rates (0.001-40 $M_{\odot}$ yr$^{-1}$). The outflow rates correlate with the AGN bolometric luminosity ($L_{\rm bol}\sim$ 10$^{42.71}$-10$^{45.62}$ erg/s) but we find no correlations with black hole mass (10$^{6.1}$-10$^{8.9}$ M$_{\odot}$), Eddington ratio (0.002-1.1) and radio luminosity (10$^{21}$-10$^{26}$ W/Hz). We find the median coupling between the kinetic energy and $L_{\rm bol}$ to be 1%, consistent with the theoretical predictions for an AGN-driven outflow.

Simulations indicate that the inflow of gas of star-forming galaxies is almost co-planar and co-rotating with the gas disk, and that the outflow of gas driven by stellar winds and/or supernova explosions is preferentially perpendicular to the disk. This indicates that the galactic gas disk can be treated as a {\it modified} accretion disk. In this work, we focus on the metal enhancement in galactic disks in this scenario of gas accretion. Assuming that the star formation rate surface density ($\Sigma_{\rm SFR}$) is of exponential form, we obtain the analytic solution of gas-phase metallicity with only three free parameters: the scalelength of $\Sigma_{\rm SFR}$, the metallicity of the inflowing gas and the mass-loading factor of the wind. According to this simple model, the negative gradient of gas-phase metallicity is a natural consequence of the radial inflow of cold gas which is continuously enriched by in-situ star formation as it moves towards the disk center. We fit the model to the observed metallicity profiles for six nearby galaxies chosen to have well-measured metallicity profiles extending to very large radii. Our model can well characterize the overall features of the observed metallicity profiles. The observed profiles usually show a floor at the outer regions of the disk, corresponding to the metallicity of inflow gas. Furthermore, we find the scalelength of $\Sigma_{\rm SFR}$ inferred from these fits agree well with independent estimates from the H$\alpha$ profiles, supporting the basic model.

Hot Jupiters receive intense irradiation from their stellar hosts. The resulting extreme environments in their atmospheres allow us to study the conditions that drive planetary atmospheric dynamics, e.g., global-scale winds. General circulation models predict day-to-nightside winds and equatorial jets with speeds on the order of a few km $\mathrm{s^{-1}}$. To test these models, we apply high-resolution transmission spectroscopy using the PEPSI spectrograph on the Large Binocular Telescope to study the atmosphere of KELT-9 b, an ultra-hot Jupiter and currently the hottest known planet. We measure $\sim$10 km $\mathrm{s^{-1}}$ day-to-nightside winds traced by Fe II features in the planet's atmosphere. This is at odds with previous literature (including data taken with PEPSI), which report no significant day-to-nightside winds on KELT-9 b. We identify the cause of this discrepancy as due to an inaccurate ephemeris for KELT-9 b in previous literature. We update the ephemeris, which shifts the mid-transit time by up to 10 minutes for previous datasets, resulting in consistent detections of blueshifts in all the datasets analyzed here. Furthermore, a comparison with archival HARPS-N datasets suggests temporal wind variability $\sim$5-8 km $\mathrm{s^{-1}}$ over timescales between weeks to years. Temporal variability of atmospheric dynamics on hot Jupiters is a phenomenon anticipated by certain general circulation models that has not been observed over these timescales until now. However, such large variability as we measure on KELT-9 b challenges general circulation models, which predict much lower amplitudes of wind variability over timescales between days to weeks.

Ranging from a few pc to hundreds of kpc in size, radio jets have, during their evolution, an impact on their gaseous environment on a large range of scales. While their effect on larger scales is well established, it is now becoming clear that they can also strongly affect the interstellar medium (ISM) inside the host galaxy. Particularly important is the initial phase ($<10^6$ yr) of the evolution of the radio jet, when they expand into the inner few kpc of the host galaxy. Here we report on results obtained for a representative group of young radio galaxies using the cold molecular gas as a tracer of jet-ISM interactions. The sensitivity and high spatial resolution of ALMA and NOEMA are ideal to study the details of this process. In many objects we find massive molecular outflows driven by the plasma jet, even in low-power radio sources. However, the observed outflows are limited to the circumnuclear regions and only a small fraction of the ISM is leaving the galaxy. Beyond this region, the impact of the jet seems to change. Fast outflows are replaced by a milder expansion driven by the expanding cocoon created by the jet-ISM interaction, resulting in dispersing and heating the ISM. These findings are in line with predictions from simulations of jets interacting with a clumpy medium and suggest a more complex view of the impact of AGN than presently implemented in cosmological simulations.

We report the discovery of 74 new pulsating DA white dwarf stars, or ZZ Cetis, from the data obtained by the Transiting Exoplanet Survey Satellite (TESS) mission, from Sectors 1 to 39, corresponding to the first 3 cycles. This includes objects from the Southern Hemisphere (Sectors 1-13 and 27-39) and the Northern Hemisphere (Sectors 14-26), observed with 120 s- and 20 s-cadence. Our sample likely includes 13 low-mass and one extremely low-mass white dwarf candidate, considering the mass determinations from fitting Gaia magnitudes and parallax. In addition, we present follow-up time series photometry from ground-based telescopes for 11 objects, which allowed us to detect a larger number of periods. For each object, we analysed the period spectra and performed an asteroseismological analysis, and we estimate the structure parameters of the sample, i.e., stellar mass, effective temperature and hydrogen envelope mass. We estimate a mean asteroseismological mass of <Msis>_~ 0.635 +/-0.015 Msun, excluding the candidate low or extremely-low mass objects. This value is in agreement with the mean mass using estimates from Gaia data, which is <Mphot> ~ 0.631 +/- 0.040 Msun, and with the mean mass of previously known ZZ Cetis of <M*>= 0.644 +/-0.034 Msun. Our sample of 74 new bright ZZ~Cetis increases the number of known ZZ~Cetis by $\sim$20 per cent.

We measure the star cluster mass function for the Local Group galaxy M33. We use the catalog of stellar clusters selected from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER) survey. We analyze 711 clusters in M33 with $\rm 7.0 < log(Age/yr) < 8.5$, and log($M/M_{\odot}$) $>$ 3.0 as determined from color-magnitude diagram fits to individual stars. The M33 cluster mass function is best described by a Schechter function with power law slope $\alpha = -2.06^{+0.14}_{-0.13}$, and truncation mass log($M_c/M_{\odot}$) $= 4.24^{+0.16}_{-0.13}$. The data show strong evidence for a high-mass truncation, thus strongly favoring a Schechter function fit over a pure power law. M33's truncation mass is consistent with the previously identified linear trend between $M_c$, and star formation rate surface density, \SigSFR. We also explore the effect that individual cluster mass uncertainties have on derived mass function parameters, and find evidence to suggest that large cluster mass uncertainties have the potential to bias the truncation mass of fitted mass functions on the one sigma level.

We present a detailed analysis of five bright spectroscopic binary systems (HD 18665, HD 27131, HD 171852, HD 215550, HD 217427) that have orbital periods of P < 500 days. We determined the complete set of orbital parameters using the toolkit RadVel by analyzing the observed radial velocity curves. To study the properties of the five systems, we also analyzed the intermediate resolution spectra (R = 20,000) observed with the TIGRE telescope and determined the stellar parameters of the primary stars using the toolkit iSpec. With Gaia Early Data Release 3 parallaxes, a correction for interstellar extinction using the 3D dust map, and bolometric corrections, we placed the stars in the Hertzsprung-Russell diagram and compared the positions with stellar evolution tracks calculated with the Eggleton code to determine the masses and ages of the primary stars. They have all evolved to the giant phase. Finally, we were able to determine the masses of the secondary stars and to estimate the orbital inclinations i of the binary systems.

Because of its complex clumpy wind, prominent cyclotron resonant scattering features, intrinsic variability and convenient physical parameters (close distance, high inclination, small orbital separation) which facilitate the observation and analysis of the system, Vela X-1 is one of the key systems to understand accretion processes in high-mass X-ray binaries on all scales. We revisit Vela X-1 with two new observations taken with NuSTAR at orbital phases ~0.68-0.78 and ~0.36-0.52 which show a plethora of variability and allow us to study the accretion geometry and stellar wind properties of the system. We follow the evolution of spectral parameters down to the pulse period time-scale using a partially covered powerlaw continuum with a Fermi-Dirac cut-off to model the continuum and local absorption. We could confirm anti-correlations between the photon index and the luminosity and, for low fluxes, between the folding energy and the luminosity, implying a change of properties in the Comptonising plasma. We could not confirm a previously seen correlation between the cyclotron line energy and the luminosity of the source in the overall observation, but we observed a drop in the cyclotron line energy following a strong flare. We see strong variability in absorption between the two observations and within one observation (for the ~0.36-0.52 orbital phases) that can be explained by the presence of a large-scale structure, such as accretion- and photoionisation wakes in the system and our variable line of sight through this structure.

We present HST optical images, Keck-OSIRIS NIR IFS data cubes and Keck-NIRC2 NIR images of nova V5668 Sgr from 2016 to 2019. The observations indicate enhanced emission at the polar caps and equatorial torus for low ionization lines, and enhanced high ionization emission lines only at the polar caps. The radial velocities are compatible with a homogeneous expansion velocity of v=590 km s$^{-1}$ and a system inclination angle of 24$^o$. These values were used to estimate an expansion parallax distance of 1200 $\pm$ 400 pc. The NIRC2 data indicate the presence of dust in 2016 and 2017, but no dust emission could be detected in 2019. The observational data were used for assembling 3D photoionization models of the ejecta. The model results indicate that the central source has a temperature of $1.88\times10^{5}$ K and a luminosity of $1.6\times10^{35}$ erg s$^{-1}$ in August of 2017 (2.4 years post eruption), and that the shell has a mass of $6.3\times10^{-5}$ M$_{\odot}$. The models also suggest an anisotropy of the ionizing flux, possibly by the contribution from a luminous accretion disc.

We extend the analysis of Pace et al., JCAP, 2019, 060, by considering the virialization process in the extended spherical collapse model for clustering dark-energy models, i.e., accounting for dark-energy fluctuations. Differently from the standard approach, here virialization is naturally achieved by properly modelling deviations from sphericity due to shear and rotation induced by tidal interactions. We investigate the time evolution of the virial overdensity $\Delta_\mathrm{vir}$ in seven clustering dynamical dark energy models and compare the results to the $\Lambda$CDM model and to the corresponding smooth dark-energy models. Taking into account all the appropriate corrections, we deduce the abundance of convergence peaks for Rubin Observatory-LSST and Euclid-like weak-lensing surveys, of Sunyaev-Zel'dovich peaks for a Simon Observatory-like CMB survey, and of X-ray peaks for an eROSITA-like survey. Despite the tiny differences in $\Delta_\mathrm{vir}$ between clustering and smooth dark-energy models, owing to the large volumes covered by these surveys, five out of seven clustering dark-energy models can be statistically distinguished from $\Lambda$CDM. The contribution of dark-energy fluctuation cannot be neglected, especially for the Chevallier-Polarski-Limber and Albrecht-Skordis models, provided the instrumental configurations provide high signal-to-noise ratio. These results are almost independent of the tidal virialization model.

We report observations of the recently discovered super-Neptune TOI-674 b (5.25 Earth radii, 23.6 Earth mass) with the Hubble Space Telescope's Wide Field Camera 3 instrument. TOI-674 b is deep into the Neptune desert, an observed paucity of Neptune-size exoplanets at short orbital periods. Planets in the desert are thought to have complex evolutionary histories due to photoevaporative mass loss or orbital migration, making identifying the constituents of their atmospheres critical to understanding their origins. We obtained near-infrared transmission spectroscopy of the planet's atmosphere with the G141 grism, which we detrended and fit. After extracting the transmission spectrum from the data, we used the petitRADTRANS atmospheric spectral synthesis code to perform retrievals on the planet's atmosphere to identify which absorbers are present. These results show evidence for increased absorption at 1.4 $\mu$m due to water vapor at $2.1\sigma$ (Bayes factor = 3.2). With these results, TOI-674 b joins the exclusive club of exoplanets with featured transmission spectra. TOI-674 b is a strong candidate for further study to refine the water abundance, which is poorly constrained by our data. We also incorporated new TESS short-cadence optical photometry, as well as Spitzer/IRAC data, and re-fit the transit parameters for the planet. We find the planet to have the following transit parameters: $R_p/R_* = 0.1135\pm0.0006$, $T_0 = 2458544.523792\pm0.000452$ BJD, and $P = 1.977198\pm0.00007$ d. These measurements refine the planet radius estimate and improve the orbital ephemerides for future transit spectroscopy observations of this highly intriguing warm Neptune.

Cluster spiral galaxies suffer catastrophic losses of the cool, neutral gas component of their interstellar medium due to ram pressure stripping, contributing to the observed quenching of star formation in the disk compared to galaxies in lower density environments. However, the short term effects of ram pressure on the star formation rate and AGN activity of galaxies undergoing stripping remain unclear. Numerical studies have recently demonstrated cosmic rays can dramatically influence galaxy evolution for isolated galaxies, yet their influence on ram pressure stripping remains poorly constrained. We perform the first cosmic-ray magneto-hydrodynamic simulations of an $L_{*}$ galaxy undergoing ram pressure stripping, including radiative cooling, self-gravity of the gas, star formation, and stellar feedback. We find the microscopic transport of cosmic rays plays a key role in modulating the star formation enhancement experienced by spirals at the outskirts of clusters compared to isolated spirals. Moreover, we find that galaxies undergoing ram pressure stripping exhibit enhanced gas accretion onto their centers, which may explain the prevalence of AGN in these objects. In agreement with observations, we find cosmic rays significantly boost the global radio emission of cluster spirals. Although the gas removal rate is relatively insensitive to cosmic ray physics, we find that cosmic rays significantly modify the phase distribution of the remaining gas disk. These results suggest observations of galaxies undergoing ram pressure stripping may place novel constraints on cosmic-ray calorimetry and transport.

To settle the question of the nature of the interstellar object 1I/'Oumuamua requires in-situ observations via a spacecraft, as the object is already out of range of existing telescopes. Most previous proposals for reaching 1I/'Oumuamua using near-term technologies are based on the Solar Oberth Manoeuvre (SOM), as trajectories without the SOM are generally significantly inferior in terms of lower mission duration and higher total velocity requirement. While the SOM allows huge velocity gains, it is also technically challenging and thereby increases programmatic and mission-related risks. In this paper, we identify an alternative route to the interstellar object 1I/'Oumuamua, based on a launch in 2028, which does not require a SOM but has a similar performance as missions with a SOM. It instead employs a Jupiter Oberth Manoeuvre (JOM) with a total time of flight of around 26 years or so. The efficacy of this trajectory is a result of it significantly reducing the $\Delta$V to Jupiter by exploiting the VEEGA sequence. The total $\Delta$V of the trajectory is 15.8 $kms^{-1}$ and the corresponding payload mass is 115 kg for a SLS Block 1B or 241 kg for a Block 2. A further advantage of the JOM is that the arrival speed relative to 1I/'Oumuamua is approximately 18 $kms^{-1}$, much lower than the equivalent for the SOM of around 30 $kms^{-1}$.

[Abridged] The interstellar medium is observed to be organised in filamentary structures, as well as neutral (HI) and ionized (HII) bubbles. The expanding nature of these bubbles makes them shape their surroundings and possibly play a role in the formation and evolution of interstellar filaments. We present APEX $^{13}$CO and C$^{18}$O(2-1) observations of the NGC 6334 molecular cloud. We investigate the gas velocity structure along and across the 50 pc-long cloud and towards 75 identified velocity-coherent-filaments (VCFs). We measure a wealth of velocity gradients along the VCFs. We derive the column density and velocity power spectra of the VCFs. These power spectra are well represented with power laws showing similar slopes for both quantities (with a mean of about -2), albeit some differ by up to a factor of two. The position velocity diagrams perpendicular to three VCFs show the V-shaped velocity pattern, corresponding to a bent structure in velocity space with the filament at the tip of the V surrounded by an extended structure connected to it with a velocity gradient. This velocity structure is qualitatively similar to that resulting from numerical simulations of filament formation from large-scale compression from propagating shock fronts. In addition, the radial profiles perpendicular to these VCFs hint to small-scale internal impacts from neighbouring HII bubbles. The observed opposite curvature in velocity space towards the VCFs points to various origins of large-scale external compressions from propagating HI bubbles. This suggests the plausible importance of multiple HI compressions, separated in space and time, in the formation and evolution of molecular clouds and their star formation history. These latter atomic compressions due to past and distant star formation events are complemented by the impact of HII bubbles from present time and local star formation activity.

We present results from ALMA 1.2mm continuum observations of a sample of 27 star-forming galaxies at z=2.1-2.5 from the MOSFIRE Deep Evolution Field (MOSDEF) survey. These galaxies have gas-phase metallicity and star-formation rate measurements from Hb, [OIII], Ha, and [NII]. Using stacks of Spitzer, Herschel, and ALMA photometry (rest-frame ~ 8-400$\mu$m), we examine the IR SED of high-redshift subsolar metallicity (~0.5 $Z_{\odot}$) LIRGs. We find that the data agree well with an average SED template of higher luminosity local low-metallicity dwarf galaxies (reduced $\chi^2$ of 1.8). When compared with the commonly used templates for solar-metallicity local galaxies or high-redshift LIRGs and ULIRGs, even in the most favorable case (with reduced $\chi^2$ of 2.8), the templates are rejected at >98% confidence level. The broader and hotter IR SED of both the local dwarfs and high-redshift subsolar metallicity galaxies may result from different grain properties, a clumpy dust geometry, or a harder/more intense ionizing radiation field that heats the dust to higher temperatures. The obscured SFR indicated by the FIR emission of the subsolar metallicity galaxies is only ~ 60% of the total SFR, which is considerably lower than that of the local LIRGs with ~ 96-97% obscured fractions. Due to the evolving IR SED shape, the local LIRG templates fit to mid-IR data can overestimate the Rayleigh-Jeans tail measurements at z~2 by a factor of 2-20, and these templates underestimate IR luminosities if fit to the observed ALMA fluxes by >0.4dex. At a given stellar mass or metallicity, dust masses at z~2.3 are an order of magnitude higher than those at z~0. Given the predicted molecular gas mass fractions, the observed z~2.3 dust-to-stellar mass ratios suggest lower dust-to-molecular gas masses than in local galaxies at the same metallicity.

One of the major priorities of international radio astronomy is to study the early universe through the detection of the 21 cm HI line from the epoch of reionisation (EoR). Due to the weak nature of the 21 cm signal, an important part in the detection of the EoR is removing contaminating foregrounds from our observations as they are multiple orders of magnitude brighter. In order to achieve this, sky maps spanning a wide range of frequencies and angular scales are required for calibration and foreground subtraction. Complementing the existing low-frequency sky maps, we have constructed a Southern Sky map through spherical harmonic transit interferometry utilising the engineering development array 2 (EDA2), a square kilometre array (SKA) low-frequency array prototype system. We use the m-mode formalism to create an all-sky map at 159MHz with an angular resolution of 3 degrees, with data from the (EDA2) providing information over +60 degrees to -90 degrees in declination. We also introduce a new method for visualising and quantifying how the baseline distribution of an interferometer maps to the spherical harmonics, and discuss how prior information can be used to constrain spherical harmonic components that the interferometer is not sensitive to.

Context. Collecting a large variety of exoplanetary atmosphere measurements is crucial to improve our understanding of exoplanets. In this context, it is likely that the field would benefit from broad species surveys, particularly using transit spectroscopy, which is the most successful technique of exoplanetary atmosphere characterization so far. Aims: Our goal is to develop a model-unbiased technique using transit spectroscopy to analyze every qualified atomic spectral line in exoplanetary transit data, and search for relative absorption, that is, a decrease in the flux of the line when the planet is transiting. Methods: We analyzed archive data from HDS at Subaru, HIRES at Keck, UVES at VLT, and HARPS at LaSilla to test our spectral survey methodology. It first filtered individual lines by relative noise levels. It also corrected for spectral offsets and telluric contamination. Our methodology performed an analysis along time and wavelength. The latter employed a bootstrap corroboration. Results: We highlight the possible detections of Mn I and V II in HD 209459b data taken by HDS at Subaru ($5.9\sigma$ at 5916.4 $\angstrom$, $5.1\sigma$ at 6021.8 $\angstrom$). The previous detection of Ca I in the same planet is classified as inconclusive by our algorithm, but we support the previous detection of Sc II ($3.5\sigma$ at 6604.6 $\angstrom$). We also highlight the possible detection of Ca I, Sc II, and Ti II in HD 189733 data taken by UVES at VLT ($4.4\sigma$ at $6572.8 \angstrom$, $6.8\sigma$ at $6604.6 \angstrom$, and $3.5\sigma$ at $5910.1 \angstrom$), in addition to the possible detection of Al I in WASP-74b data taken by UVES at VLT ($5.6 \sigma$ at $6696.0 \angstrom$).

Substantial silicate vapor is expected to be in chemical equilibrium at temperature conditions typical of the silicate-atmosphere interface of sub-Neptune planets, which can exceed 5000 K. Previous models of the atmospheric structure and evolution of these exoplanets, which have been used to constrain their atmospheric mass fractions, have neglected this compositional coupling. In this work, we show that silicate vapor in a hydrogen-dominated atmosphere acts as a condensable species, decreasing in abundance with altitude. The resultant mean molecular weight gradient inhibits convection at temperatures above $\sim 4000$ K, inducing a near-surface radiative layer. This radiative layer decreases the planet's total radius compared to a planet with the same base temperature and a convective, pure H/He atmosphere. Therefore, we expect silicate vapor to have major effects on the inferred envelope mass fraction and thermal evolution of sub-Neptune planets. We demonstrate that differences in radii, and hence in inferred atmospheric masses, are largest for planets which have larger masses, equilibrium temperatures, and atmospheric mass fractions. The effects are largest for younger planets, but differences can persist on gigayear time-scales for some sub-Neptunes. For a $10 M_\oplus$ planet with $T_\mathrm{eq}=1000$ K and an age of $\sim 300$ Myr, an observed radius consistent with an atmospheric mass fraction of 10% when accounting for silicate vapor would be misinterpreted as indicating an atmospheric mass fraction of 2% if a H/He-only atmosphere were assumed. The presence of silicate vapor in the atmosphere is also expected to have important implications for the accretion and loss of primordial hydrogen atmospheres.

OGLE-2016-BLG-1093 is a planetary microlensing event that is part of the statistical $Spitzer$ microlens parallax sample. The precise measurement of the microlens parallax effect for this event, combined with the measurement of finite source effects, leads to a direct measurement of the lens masses and system distance: $M_{\rm host} = 0.38$--$0.57\, M_{\odot}$, $m_p = 0.59$--$0.87\, M_{\rm Jup}$, and the system is located at the Galactic bulge ($D_L \sim 8.1$ kpc). Because this was a high-magnification event, we are also able to empirically show that the "cheap-space parallax" concept Gould & Yee (2012) produces well-constrained (and consistent) results for $|\pi_{\rm E}|$. This demonstrates that this concept can be extended to many two-body lenses. Finally, we briefly explore systematics in the $Spitzer$ light curve in this event and show that their potential impact is strongly mitigated by the color-constraint.

AstroSat spectra of the black hole system GRS 1915+105 during the heartbeat state (with a varying oscillation period from 150 to 100 secs) were analysed using a truncated relativistic disc model along with a Comptonization component. Spectra were fitted for segments of length ~ 24 secs. The oscillation can be described as coordinated variations of the accretion rate, Comptonised flux, and the inner disc radius, with the latter ranging from 1.235-5 gravitational radii. Comparison with results from the $\chi$ and Intermediate states shows that while the accretion rate and the high energy photon index were similar, the inner disc radius and the fraction of Comptonised photons were larger for these states than for the heartbeat one. The coronal efficiency $\eta \equiv L_{ac}/\dot M c^2$, where $L_{ac}$ is the radiative luminosity generated in the corona is found to be approximately $\propto \dot M^{-2/3}$ for all the observations. The efficiency decreases with inner radii for the heartbeat state but has similar values for the $\chi$ and Intermediate states where the inner radii is larger. The implications of these results are discussed.

The usual generalized uncertainty principle will lead to a divergent mass limit of white dwarf, which disagrees with the Chandrasekhar limit and the observations. In order to remove the divergence, we introduce a maximum momentum and a negative parameter for the generalized uncertainty principle as two independent solutions to restore the limit. Particularly, the expression of parameter is given to explain why the parameter should be negative for the white dwarf. In addition, we also discuss the internal relation between the maximum momentum and the negative parameter.

We used archival very long baseline interferometry (VLBI) data of active galactic nuclei (AGN) observed from 1.4 GHz to 86 GHz to measure the angular size of VLBI radio cores in 9525 AGNs. We analysed their sky distributions, frequency dependencies and created the distribution map of large-scale scattering properties of the interstellar medium in our Galaxy for the first time ever. Significant angular broadening of the measured AGN core sizes is detected for the sources seen through the Galactic plane, and this effect is especially strong at low frequencies (e.g. at 2 GHz). The scattering screens containing electron density fluctuations of hot plasma are mainly concentrated in the Galactic plane and manifest clumpy distribution. The region of the strongest scattering is the Galactic centre, where the Galactic bar and the compact radio source Sagittarius A* are located. We have also found the enhancement of scattering strength in regions of the Cygnus constellation, supernova remnants Taurus A, Vela, W78 and Cassiopeia A, and the Orion Nebula. Using multi-frequency observational data of AGN core sizes, we separated the contribution of the intrinsic and scattered sizes to the measured angular diameter for 1546 sources. For the sources observed through the Galactic plane, the contribution of the scattered size component is systematically larger than for those seen outside the Galactic plane. The derived power-law scattering indices are found to be in a good agreement with theoretical predictions for the diffractive dominated scattering of radio emission in a hot turbulent plasma.

Modeling of frequency-dependent effects, contributed by the turbulence in the free electron density of interstellar plasma, is required to enable the detection of the expected imprints from the stochastic gravitational-wave (GW) background in pulsar timing data. In this work, we present an investigation of temporal variations of interstellar medium for a set of millisecond pulsars (MSPs) with the upgraded GMRT aided by large fractional bandwidth at lower observing frequencies. Contrary to the conventional narrow-band analysis using a frequency invariant template profile, we applied PulsePortraiture based wide-band timing analysis while correcting for the significant evolution of the pulsar profile with frequency. Implementation of PulsePortraiture based wide-band timing method for the GMRT discovered MSPs to probe the DM variations resulted in a DM precision of $10^{-4}\,pc~cm^{-3}$. In general, we achieve better DM and timing precision from wide-band timing compared to the narrow-band timing with matching temporal variations of DMs. This wide-band timing study of newly discovered MSPs over a frequency range of 300 to 1460 MHz, highlights the effectiveness of profile-modeling at low frequencies and probes the potential of using them in pulsar timing array.

Measuring distances of cosmological sources such as galaxies, stars and quasars plays an increasingly critical role in modern cosmology. Obtaining the optical spectrum and consequently calculating the redshift as a distance indicator could instantly classify these objects. As long as spectroscopic observations are not available for many galaxies and the process of measuring the redshift is time-consuming and infeasible for large samples, machine learning (ML) approaches could be applied to determine the redshifts of galaxies from different features including their photometric colors. In this paper, by using the flux magnitudes from the Sloan Digital Sky Survey (SDSS) catalog, we develop two ML regression algorithms (Decision Tree and Random Forest) for estimating the redshifts taking color indices as input features. We find that the Random Forest algorithm produces the optimum result for the redshift prediction, and it will be further improved when the dataset is limited to a subset with z $\le$ 2 giving the normalised standard deviation $\overline{\Delta Z}_{\text {norm}}=0.005$ and the standard deviation $\sigma_{\Delta z}=0.12$. This work shows a great potential of using the ML approach to determine the photometric redshifts of distant sources.

Pluto, Titan, and Triton make up a unique class of solar system bodies, with icy surfaces and chemically reducing atmospheres rich in organic photochemistry and haze formation. Hazes play important roles in these atmospheres, with physical and chemical processes highly dependent on particle sizes, but the haze size distribution in reducing atmospheres is currently poorly understood. Here we report observational evidence that Pluto's haze particles are bimodally distributed, which successfully reproduces the full phase scattering observations from New Horizons. Combined with previous simulations of Titan's haze, this result suggests that haze particles in reducing atmospheres undergo rapid shape change near pressure levels ~0.5Pa and favors a photochemical rather than a dynamical origin for the formation of Titan's detached haze. It also demonstrates that both oxidizing and reducing atmospheres can produce multi-modal hazes, and encourages reanalysis of observations of hazes on Titan and Triton.

The recent discovery of periodic pulsations from several members of the ultraluminous X-ray source (ULX) family in nearby galaxies as well as in our own galaxy unveiled the nature of the accreting compact object. Neutron stars rather than black holes are currently believed to power a substantial number of ULXs whether or not pulsations are observed. The detection of cyclotron absorption lines in the X-ray spectrum of a ULX provides an alternative way to identify the compact object as a neutron star. Among the non-pulsating ULXs, the presence of a cyclotron resonance scattering feature (CRSF) in the spectrum of M51 ULX-8 has been reported. In the present work, the magnetic field strength on the surface of the neutron star in M51 ULX-8 is inferred from the energy of the observed CRSF to estimate the beaming fraction in X-ray emission and more importantly the observable range for the elusive neutron-star spin period to be hopefully discovered by the forthcoming space missions in the near future.

The D4000 spectral break index is one of the most important features in the visible spectrum, as it is a proxy for stellar ages and is also used in galaxy classification. However, its direct measurement has always been reserved to spectroscopic observations. In this work, we present a general method to directly measure the D4000 spectral break index with narrow-band photometry: this method has been validated using realistic simulations, and then evaluated with PAUS NBs, cross-matched with VIPERS spectra ($i_{\rm AB} < 22.5$, $0.562 < z < 0.967$). For comparison, we also determine the D4000 in this sample with the SED-fitting code CIGALE (for both PAUS NBs and broad-band data from CFHTLS). The direct D4000 measurement has significantly lower SNR than the CIGALE D4000, however, we find that for $i_{\rm AB}<21$ (two magnitudes above PAUS completeness limit) all direct D4000 measurements have $SNR>3$. Moreover, CIGALE underestimates the error by $>$50\%, while the direct D4000 has proper error estimation within $<$10\%. We study the D4000-stellar mass relationship for red and blue galaxies, as well as the D4000-SFR dependence: all methods show agreements with VIPERS within $1\sigma$, and the D4000-mass relation is especially well reproduced for blue galaxies. We also evaluate how a D4000 cut classifies galaxies into red/blue compared to machine learning: the CIGALE D4000 with PAUS NBs has the best results while providing realistic cut values. We conclude that the direct measurement of D4000 with narrow-band photometry is a promising tool that allows individual measurements for objects measured with $SNR > 3$, or averages by stacking, with results compatible with spectroscopy.

Precise measurements of exoplanets radii are of key importance for our understanding of the origin and nature of these objects. Measurement of the planet radii using the transit method have reached a precision that the effects of stellar surface features have to be taken into account. While the effects from spots have already been studied in detail, our knowledge of the effects caused by faculae is still limited. This is particularly the case for M-stars. Faculae can pose a problem if they are inhomogeneously distributed on the stellar surface. Using the eclipse mapping method, we study the distribution of the faculae on the surface of GJ1214 using the CaIIH&K lines as tracers. In order to assess the homogeneity of the distribution in a quantitative way, we introduce the inhomogeneity factor IHF. IHF is 0% if the distribution is homogeneous, positive, if the plage regions are preferentially located along the path of the planet, and negative, if they are preferentially located outside the path of the planet. For GJ1214, we derive a rather small value of IHF=7.7-7.7+12.0%. We discuss the relevance of this result in the context of the PLATO and ARIEL missions.

Radio-loud active galaxies have two accretion modes [radiatively inefficient (RI) and radiatively efficient (RE)], with distinct optical and infrared signatures, and two jet dynamical behaviours, which in arcsec- to arcmin-resolution radio surveys manifest primarily as centre- or edge-brightened structures [Fanaroff-Riley (FR) class I and II]. The nature of the relationship between accretion mode and radio morphology (FR class) has been the subject of long debate. We present a comprehensive investigation of this relationship for a sample of 286 well-resolved radio galaxies in the LOFAR Two-metre Sky Survey Deep Fields (LoTSS-Deep) first data release, for which robust morphological and accretion mode classifications have been made. We find that two-thirds of luminous FRII radio galaxies are RI, and identify no significant differences in the visual appearance or source dynamic range (peak/mean surface brightness) of the RI and RE FRIIs, demonstrating that both RI and RE systems can produce FRII structures. We also find a significant population of low-luminosity FRIIs (predominantly RI), supporting our earlier conclusion that FRII radio structures can be produced at all radio luminosities. We demonstrate that in the luminosity range where both morphologies are present, the probability of producing FRI or FRII radio morphology is directly linked to stellar mass, while across all morphologies and luminosities, RE accretion occurs in systems with high specific star formation rate, presumably because this traces fuel availability. In summary, the relationship between accretion mode and radio morphology is very indirect, with host-galaxy environment controlling these two key parameters in different ways.

We investigate the relationship between different transients such as blinkers detected in images taken at 304~{\AA}, extreme ultraviolet coronal bright points (ECBPs) at 193~{\AA}, X-ray coronal bright points (XCBPs) at 94~{\AA} on AIA, and magnetic features observed by HMI during ten years of solar cycle 24. An automatic identification method is applied to detect transients, and the YAFTA algorithm is used to extract the magnetic features. Using ten years of data, we detect in total 7,483,827 blinkers, 2,082,162 ECBPs, and 1,188,839 XCBPs, respectively, with their birthrate of about $1.1\times10^{-18}$ ${\rm m}^{-2}{\rm s}^{-1}$, $3.8\times10^{-19}$ ${\rm m}^{-2}{\rm s}^{-1}$, and $1.5\times10^{-19}$ ${\rm m}^{-2}{\rm s}^{-1}$. We find that about 80\% of blinkers are observed at the boundaries of supergranules, and 57\% (34\%) are associated with ECBPs (XCBPs). We further find that about 61{--}80\% of transients are associated with the isolated magnetic poles in the quiet Sun and that \textbf{the normalized maximum intensities of the transients are correlated with photospheric magnetic flux of poles} via a power law. These results conspicuously show that these transients have a magnetic origin and their synchronized behavior provides further clues towards the understanding of the coupling among the different layers of the solar atmosphere. Our study further reveals that the appearance of these transients is strongly anti-correlated with the sunspots cycle. This finding can be relevant for a better understanding of solar dynamo and magnetic structures at different scales during the solar cycle.

We present an XMM-Newton catalogue of BL Lac X-ray, optical, and UV properties based on cross-correlation with the 1151 BL Lacs listed in the fifth edition of the Roma-BZCAT. We searched for the X-ray counterparts to these objects in the field of view of all pointed observations in the XMM-Newton archive over nearly 20 years of mission. The cross-correlation yields a total of 310 XMM-Newton fields which correspond to 103 different BL Lacs. We homogeneously analysed data from the three EPIC cameras (X-ray) and OM(optical/UV) using the XMM-Newton SAS software, and produced images, light curves, and spectral products for BL Lacs detected in any of the three EPIC cameras. We tested two different phenomenological models, log parabola and power law, with different variations of the absorbing column density and extracted their parameters. We derived time-variability information from the light curves following well-established statistical methods and quantified variability through statistical indicators. OM magnitudes and fluxes were computed wherever possible. We see that the log parabola model is preferred over the power law model for sources showing higher fluxes, which might indicate that curvature is intrinsic to BL Lacs and is only seen when the flux is high. We present the results of our analysis as a catalogue of X-ray spectral properties of the sample in the 0.2-10 keV energy band as well as in the optical/UV band. We complete the catalogue with multi-wavelength information at radio and gamma-ray energies.

The quasar 3C 273 has been observed with infrared spectroastrometry (SA) on broad Pa$\alpha$ line and optical reverberation mapping (RM) on broad H$\beta$ line. SA delivers information about the angular size and structure of the Pa$\alpha$ broad-line region (BLR), while RM delivers information about the physical size and structure of the H$\beta$ BLR. Based on the fact that the two BLRs share the mass of the supermassive black hole (SMBH) and viewing inclination, a combination of SA and velocity-resolved RM (SARM) thereby allows us to simultaneously determine the SMBH mass and geometric distance through dynamically modeling the two BLRs. We construct a suite of dynamical models with different geometric configurations and apply a Bayesian approach to obtain the parameter inferences. Overall the obtained masses and distances are insensitive to specific BLR configurations but more or less depend on parameterizations of the vertical distributions. The most probable model, chosen in light of the Bayes factor, yields an angular-size distance of $\log\,(D_{\rm A}/{\rm Mpc}) = 2.83_{-0.28}^{+0.32}$ and SMBH mass of $\log\,(M_\bullet/M_\odot)=9.06_{-0.27}^{+0.21}$, which agrees with the relationships between SMBH masses and bulge properties. The BLRs have an inclination of $5_{-1}^{+1}$ degrees, consistent with that of the large-scale jet in 3C 273. Our approach reinforces the capability of SARM analysis to measure SMBH mass and distance of AGNs even though SA and RM observations are undertaken with different emission lines and/or in different periods.

We present results of a 2014-2018 campaign of radial velocity measurements of $\delta$ Ceti. Combining our determination of pulsation period with historical data we conclude that the most likely explanation of observed changes is the presence of a secondary component with a minimum mass of $1.10 \pm 0.05 M_{\odot}$ on an orbit with a period of $169 \pm 6$ years. Consequently, we revised the intrinsic, evolutionary period change rate to not larger than $0.018 \pm 0.004$ s/century, which is significantly lower than previous estimations and is consistent with evolutionary models of Neilson & Ignace (2015). We did not find any significant multiperiodic frequencies in radial velocity periodograms such as those reported by Aerts et al. (2006) in photometric data from MOST satellite. Using interferometric angular size of $\delta$ Ceti from JMMC Stellar Diameters Catalogue we determined several physical parameters of the star with bolometric flux method. They turned out to be consistent with most previous deteminations, confirming lower mass and slower evolution of $\delta$ Ceti than obtained using different methods by Aerts et al. (2006) and Neilson & Ignace (2015).

The Simons Observatory (SO) will detect and map the temperature and polarization of the millimeter-wavelength sky from Cerro Toco, Chile across a range of angular scales, providing rich data sets for cosmological and astrophysical analysis. The SO focal planes will be tiled with compact hexagonal packages, called Universal Focal-plane Modules (UFMs), in which the transition-edge sensor (TES) detectors are coupled to 100 mK microwave-multiplexing electronics. Three different types of dichroic TES detector arrays with bands centered at 30/40, 90/150, and 220/280 GHz will be implemented across the 49 planned UFMs. The 90/150GHz and 220/280 GHz arrays each contain 1,764 TESes, which are read out with two 910x multiplexer circuits. The modules contain a series of densely routed silicon chips, which are packaged together in a controlled electromagnetic environment with robust heat-sinking to 100 mK. Following an overview of the module design, we report on early results from the first 220/280GHz UFM, including detector yield, as well as readout and detector noise levels.

X-ray observations of star-planet systems are important to grow our understanding of exoplanets; these observation allow for studies of photoevaporation of the exoplanetary atmosphere, and in some cases even estimations of the size of the outer planetary atmosphere. The German-Russian eROSITA instrument onboard the SRG (Spectrum Roentgen Gamma) mission is performing the first all-sky X-ray survey since the 1990s, and provides X-ray fluxes and spectra of exoplanet host stars over a much larger volume than was accessible before. Using new eROSITA data as well as archival data from XMM-Newton, Chandra and ROSAT we estimate mass loss rates of exoplanets under an energy-limited escape scenario, and identify several exoplanets with strong X-ray irradiation and expected mass-loss that are amenable to follow-up observations at other wavelengths. We model sample spectra using a toy model of an exoplanetary atmosphere to predict what exoplanet transit observations with future X-ray missions such as Athena will look like, and estimate the observable X-ray transmission spectrum for a typical Hot Jupiter-type exoplanet.

We present a reanalysis (using the Minnaert limb-darkening approximation) of visible/near-infrared (0.3 - 2.5 micron) observations of Uranus and Neptune made by several instruments. We find a common model of the vertical aerosol distribution that is consistent with the observed reflectivity spectra of both planets, consisting of: 1) a deep aerosol layer with a base pressure >7 bar, assumed to be composed of a mixture of H2S ice and photochemical haze; 2) a layer of photochemical haze, trapped in a layer of high static stability at the methane condensation level at 1-2 bar; and 3) an extended layer of photochemical haze, likely of the same composition as the 1-2-bar layer, extending from this level up through to the stratosphere, where the photochemical haze particles are thought to be produced. For Neptune, we find that we also need to add a thin layer of micron-sized methane ice particles at ~0.2 bar to explain the enhanced reflection at longer methane-absorbing wavelengths. We suggest that methane condensing onto the haze particles at the base of the 1-2-bar aerosol layer forms ice/haze particles that grow very quickly to large size and immediately 'snow out' (as predicted by Carlson et al. 1988), re-evaporating at deeper levels to release their core haze particles to act as condensation nuclei for H2S ice formation. In addition, we find that the spectral characteristics of 'dark spots', such as the Voyager-2/ISS Great Dark Spot and the HST/WFC3 NDS-2018, are well modelled by a darkening or clearing of the deep aerosol layer only.

Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These "ultra-hot Jupiters" have atmospheres made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planet atmospheric properties. We analyse the photometric observations of WASP-189 acquired with the instrument CHEOPS to derive constraints on the system architecture and the planetary atmosphere. We implement a light curve model suited for asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also model the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity and CHEOPS systematics. From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189 b, $R_p=1.600^{+0.017}_{-0.016}\,R_J$, with a precision of 1%, and the true orbital obliquity of the planetary system $\Psi_p=89.6\pm1.2\deg$ (polar orbit).We detect no significant hotspot offset from the phase curve and obtain an eclipse depth $\delta_\text{ecl}=96.5^{+4.5}_{-5.0}\,\text{ppm}$, from which we derive an upper limit on the geometric albedo: $A_g<0.48$. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope.

We consider the recently proposed possibility that dark energy (DE) and baryons may scatter through a pure momentum exchange process, leaving the background evolution unaffected. Earlier work has shown that, even for barn-scale cross-sections, the imprints of this scattering process on linear cosmological observables is too tiny to be observed. We therefore turn our attention to non-linear scales, and for the first time investigate the signatures of DE-baryon scattering on the non-linear formation of cosmic structures, by running a suite of large N-body simulations. The observables we extract include the non-linear matter power spectrum, halo mass function, and density and baryon fraction profiles of halos. We find that in the non-linear regime the signatures of DE-baryon scattering are significantly larger than their linear counterparts, due to the important role of angular momentum in collapsing structures, and potentially observable. The most promising observables in this sense are the baryon density and baryon fraction profiles of halos, which can potentially be constrained by a combination of kinetic Sunyaev-Zeldovich (SZ), thermal SZ, and weak lensing measurements. Overall, our results indicate that future prospects for cosmological and astrophysical direct detection of non-gravitational signatures of dark energy are extremely bright.

Possible existence of antimatter in our Galaxy, in particular of antistars is discussed and the mechanism of their creation is described.

In light of its ubiquitous presence in the interstellar gas, the chemistry and reactivity of the HCO+ ion requires special attention. The availability of up-to-date collisional data between this ion and the most abundant perturbing species in the interstellar medium is a critical resource in order to derive reliable values of its molecular abundance from astronomical observations. This work intends to provide improved scattering parameters for the HCO+ and He collisional system. We have tested the accuracy of explicitly correlated coupled-cluster methods for mapping the short- and long-range multi-dimensional potential energy surface of atom-ion systems. A validation of the methodology employed for the calculation of the potential well has been obtained from the comparison with experimentally derived bound-state spectroscopic parameters. Finally, by solving the close-coupling scattering equations, we have derived the pressure broadening and shift coefficients for the first six rotational transitions of HCO+ as well as inelastic state-to-state transition rates up to j = 5 in the 5-100 K temperature interval.

I review the status of ultrahigh-energy cosmic ray (UHECR) physics.After introducing the main experimental results and summarizing possible intepretations, I discuss observational and theoretical constraints on the sources of UHECRs. I comment also briefly on the role of magnetic fields. Combining these constraints, I argue that luminuous and numerous AGN types as FR-I and Seyfert galaxies, or alternatively hypernovae, are the most promising UHECR sources. Finally, I sketch few of the models presented at the conference before concluding.

The Hubble tension resides in a statistically significant discrepancy between early time and late time determinations of the Hubble constant. We discuss the Hubble tension within the Ellipsoidal Universe cosmological model. We suggest that allowing small anisotropies in the large-scale spatial geometry could alleviate the tension. We, also, show that the discrepancy in the measurements of the Hubble constant is reduced to a statistically acceptable level if we assume sizeable cosmological anisotropies during the Dark Age. In addition, we argue that the Ellipsoidal Universe cosmological model should resolve the $S_8$ tension.

We summarize a series of numerical experiments of collisional dynamics in dense stellar systems such as globular clusters (GCs) and in weakly collisional plasmas using a novel simulation technique, the so-called Multi-particle collision (MPC) method, alternative to Fokker-Planck and Monte Carlo approaches. MPC is related to particle-mesh approaches for the computation of self consistent long-range fields, ensuring that simulation time scales with $N\log N$ in the number of particles, as opposed to $N^2$ for direct $N$-body. The collisional relaxation effects are modelled by computing particle interactions based on a collision operator approach that ensures rigorous conservation of energy and momenta and depends only on particles velocities and cell-based integrated quantities.

Jets from active galactic nuclei (AGN) are known to recurrently enrich their surrounding medium with mildly-relativistic particles and magnetic fields. Here, we present a detailed multi-frequency analysis of the nearby (z=0.01646) galaxy group NGC 507. In particular, we present new high-sensitivity and high spatial resolution radio images in the frequency range 144-675 MHz obtained using LOFAR and uGMRT observations. These reveal the presence of previously undetected diffuse radio emission with complex, filamentary morphology, likely related to a previous outburst of the central galaxy. Based on spectral ageing considerations, we derived that the plasma was first injected by the AGN 240-380 Myr ago and is now cooling. Our analysis of deep archival XMM-Newton data confirms that the system is dynamically disturbed, as previously suggested. We detect two discontinuities in the X-ray surface brightness distribution (in East and South direction) tracing a spiral pattern, which we interpret as cold fronts produced by sloshing motions. The remarkable spatial coincidence observed between the newly-detected arc-like radio filament and the southern concave X-ray discontinuity strongly suggests that the remnant plasma has been displaced by the sloshing motions on large scales. Overall, NGC 507 represents one of the clearest examples known to date in which a direct interaction between old AGN remnant plasma and the external medium is observed in a galaxy group. Our results are consistent with simulations, which suggest that filamentary emission can be created by the cluster/group weather disrupting AGN lobes and spreading their relativistic content into the surrounding medium.

Strong gravitational lensing of gravitational waves (GWs) has been forecasted to become detectable in the upcoming observing runs. However, definitively distinguishing pairs of lensed sources from random associations is a challenging problem. We investigate the degree to which unlensed events mimic lensed ones because of the overlap of parameters due to a combination of random coincidence and errors in parameter estimation. We construct a mock catalog of lensed and unlensed events. We find that the false alarm probability (FAP) based on coincidental overlaps of the chirp mass, sky location, and coalescence phase are approximately $11\%$, $1\%$, and $10\%$ per pair, respectively. Combining all three, the overall FAP per pair is $\sim10^{-4}$. As the number of events, $N$, in the GW catalogs increases, the number of random pairs of events increases as $\sim N^2$. Meanwhile, the number of lensed events will increase linearly with $N$, implying that for sufficiently high $N$, the false alarms will always dominate over the true lensing events. This issue can be compensated for by placing higher thresholds on the lensing candidates (e.g., selecting a higher signal-to-noise ratio (SNR) threshold), which will lead to better parameter estimation and, thus, lower FAP per pair -- at the cost of dramatically decreasing the size of the lensing sample (by $\sim 1/\mbox{SNR}^3$). We show that with our simple overlap criteria for current detectors at design sensitivity, the false alarms will dominate for realistic lensing rates ($\lesssim10^{-3}$) even when selecting the highest SNR pairs. These results highlight the necessity to design alternative identification criteria beyond simple waveform and sky location overlap. Future GW detectors Cosmic Explorer and Einstein Telescope may provide sufficient improvement in parameter estimation, allowing for the conclusive detection of strong lensing of GWs.

The large scale galaxy and matter distribution is often described by means of the cosmic web made up of voids, sheets, filaments and knots. Many different recipes exist for identifying this cosmic web. Here we focus on a sub-class of cosmic web identifiers, based on the analysis of the Hessian matrix, and proposed a method, called COsmic Web Skeleton (COWS), of separating a set of filaments cells into an ensemble of individual discreet filaments. Specifically, a thinning algorithm is applied to velocity shear tensor based cosmic web (V-web) to identify the spine of the filaments. This results in a set of filaments with well defined end-point and length. It is confirmed that these sit at local density ridges and align with the appropriate direction defined by the underlying velocity field. The radial density profile of these curved cylindrical filaments, as well as the distribution of their lengths is also examined. The robustness of all results is checked against resolution and the V-web threshold. The code for the COWS method has been made publicly available.

Advances in our understanding of the origin, evolution and structure of the universe have long been driven by cosmological perturbation theory, model building and effective field theory. In this review, we introduce numerical relativity as a powerful new complementary tool for fundamental cosmology. To illustrate its power, we discuss applications of numerical relativity to studying the robustness of slow contraction and inflation in homogenizing, isotropizing and flattening the universe beginning from generic unsmooth initial conditions. In particular, we describe how recent numerical relativity studies of slow contraction have revealed a novel, non-linear smoothing mechanism based on ultralocality that challenges the conventional view on what is required to explain the large-scale homogeneity and isotropy of the observable universe.

The logarithmic superfluid theory of physical vacuum predicts that gravity is an induced phenomenon, which has a multiple-scale structure. At astronomical scales, as the distance from a gravitating center increases, gravitational potential and corresponding spacetime metric are dominated by a Newtonian (Schwarzschild) term, followed by a logarithmic term, finally by linear and quadratic (de Sitter) terms. Correspondingly, rotation curves are predicted to be Keplerian in the inner regions of galaxies, mostly flat in the outer regions, and non-flat in the utmost outer regions. We compare theory's predictions with the furthest rotation curves data points available for a number of galaxies: using a two-parameter fit, we perform a preliminary estimate which disregards the combined effect of gas and stellar disc, but is relatively simple and uses minimal assumptions for galactic luminous matter. The data strongly points out at the existence of a crossover transition from flat to non-flat regimes at galactic outskirts.

We are fitting dynamics of electrically neutral hot-spot orbiting around Sgr A* source in Galactic center, represented by various modifications of the standard Kerr black hole (BH), to the three flares observed by the GRAVITY instrument on May 27, July 22, July 28, 2018. We consider stationary, axisymmetric and asymptotically flat spacetimes describing charged BHs in general relativity (GR) combined with non-linear electrodynamics, or reflecting influence of dark matter (DM), or in so called parameterized dirty Kerr spacetimes. We distinguish the spacetimes having different orbital frequencies from the standard Kerr BH, and test various BH spacetimes using the hot-spot data. We show that the orbital frequencies and positions of the hot-spots orbiting the considered BHs, fit the observed positions and periods of the flare orbits and give relevant constrains on the parameters of the considered BH spacetimes and the gravity or other theories behind such modified spacetimes.

We discuss some main aspects of theories of gravity containing non-local terms in view of cosmological applications. In particular, we consider various extensions of General Relativity based on geometrical invariants as $f(R, \Box^{-1} R)$, $f({\cal G}, \Box^{-1} {\cal G})$ and $f(T, \Box^{-1} T)$ gravity where $R$ is the Ricci curvature scalar, $\cal G$ is the Gauss-Bonnet topological invariant, $T$ the torsion scalar and the operator $\Box^{-1}$ gives rise to non-locality. After selecting their functional form by using Noether Symmetries, we find out exact solutions in a cosmological background. It is possible to reduce the dynamics of selected models and to find analytic solutions for the equations of motion. As a general feature of the approach, it is possible to address the accelerated expansion of the Hubble flow at various epochs, in particular the dark energy issues, by taking into account non-locality corrections to the gravitational Lagrangian. On the other hand, it is possible to search for gravitational non-local effects also at astrophysical scales. In this perspective, we search for symmetries of $f(R, \Box^{-1} R)$ gravity also in a spherically symmetric background and constrain the free parameters, Specifically, by taking into account the S2 star orbiting around the Galactic Centre SgrA$^*$, it is possible to study how non-locality affects stellar orbits around such a massive self-gravitating object.

We investigate both the null energy condition (NEC) violating scenario and the $c_T$-diminishing scenario for generating enhanced power spectrum of primordial gravitational waves (GWs) during inflation, where $c_T$ is the propagating speed of primordial GWs. Both of these two scenarios can be realized stably with theories beyond Horndeski, hence can be uniformly implemented within the framework of the effective field theory. We calculate the power spectrum of primordial GWs by assuming that the inflationary Universe undergoes three phases, where the violation of NEC or the diminishment of $c_T$ occurs in the intermediate phase. A template of the spectrum is given for the NEC-violating scenario. We also discuss the underlying relation and discrepancy between these two scenarios with a disformal transformation.

In this work we will document the design and the performances of a SiPM-based photodetector with a surface area of 100 cm$^2$ conceived to operate as a replacement for PMTs. The signals from 94 SiPMs are summed up to produce an aggregated output that exhibits in liquid nitrogen a dark count rate (DCR) lower than 100 cps over the entire surface, a signal to noise ratio better than 13, and a timing resolution better than 5.5 ns. The module feeds about 360 mW at 5 V with a dynamic range in excess of 500 photo-electrons on a 100 $\Omega$ differential line. The unit is compatible with operations at room temperature, with a DCR increased by about 6 orders of magnitude.