Papers for Thursday, Sep 16 2021

We present a multiwavelength study of the double radio relic cluster A1240 at z=0.195. Our Subaru-based weak lensing analysis detects three mass clumps forming a ~4 Mpc filamentary structure elongated in the north-south orientation. The northern ($M_{200}=2.61_{-0.60}^{+0.51}\times10^{14} M_{\odot}$) and middle ($M_{200}=1.09_{-0.43}^{+0.34}\times10^{14} M_{\odot}$) mass clumps separated by ~1.3 Mpc are associated with A1240 and co-located with the X-ray peaks and cluster galaxy overdensities revealed by Chandra and MMT/Hectospec observations, respectively. The southern mass clump ($M_{200}=1.78_{-0.55}^{+0.44}\times10^{14} M_{\odot}$), ~1.5 Mpc to the south of the middle clump, coincides with the galaxy overdensity in A1237, the A1240 companion cluster at z=0.194. Considering the positions, orientations, and polarization fractions of the double radio relics measured by the LOFAR study, we suggest that A1240 is a post-merger binary system in the returning phase with the time-since-collision ~1.7 Gyr. With the SDSS DR16 data analysis, we also find that A1240 is embedded in the much larger-scale (~80 Mpc) filamentary structure whose orientation is in remarkable agreement with the hypothesized merger axis of A1240.

We conducted systematic observations of the H I Br$\alpha$ (4.05 $\mu$m) and Br$\beta$ (2.63 $\mu$m) lines in 52 nearby ($z<0.3$) ultraluminous infrared galaxies (ULIRGs) with AKARI. Among 33 ULIRGs wherein the lines are detected, three galaxies show anomalous Br$\beta$/Br$\alpha$ line ratios ($\sim1.0$), which are significantly higher than those for case B (0.565). Our observations also show that ULIRGs have a tendency to exhibit higher Br$\beta$/Br$\alpha$ line ratios than those observed in Galactic H II regions. The high Br$\beta$/Br$\alpha$ line ratios cannot be explained by a combination of dust extinction and case B since dust extinction reduces the ratio. We explore possible causes for the high Br$\beta$/Br$\alpha$ line ratios and show that the observed ratios can be explained by a combination of an optically thick Br$\alpha$ line and an optically thin Br$\beta$ line. We simulated the H II regions in ULIRGs with the Cloudy code, and our results show that the high Br$\beta$/Br$\alpha$ line ratios can be explained by high-density conditions, wherein the Br$\alpha$ line becomes optically thick. To achieve a column density large enough to make the Br$\alpha$ line optically thick within a single H II region, the gas density must be as high as $n\sim10^8$ $\mathrm{cm}^{-3}$. We therefore propose an ensemble of H II regions, in each of which the Br$\alpha$ line is optically thick, to explain the high Br$\beta$/Br$\alpha$ line ratio.

Dual quasars are precursors of binary supermassive black holes, which are important objects for gravitational wave study, galaxy evolution, and cosmology. I report four double quasars, one of which is newly discovered, with separations of 1$-$2 arcsec selected from the DECam Legacy Survey. The Gemini optical spectra confirm that both sources are quasars at the same redshifts. J0118$-$0104 and J0932+0722 are classified as dual quasars, whereas J0037+2058 could be either a dual quasar or a lensed quasar. I estimate the physical properties such as black hole masses and Eddington ratios for the four double quasars. The newly discovered system supplements the incomplete sample of dual quasars at $\sim$10 kpc at $z>0.5$. The results demonstrate that new high-quality imaging surveys with existing spectroscopic data could reveal additional small-scale double quasars. Combined with the dual quasars from the literature, I find a power-law index of 1.45$\pm$0.48 for the distribution of dual quasars as a function of separation between 5$-$20 kpc, steeper than that expected from dynamical friction, though it is likely due to the incomplete sample at $<$15 kpc. I also discuss the implications for future searches with new imaging surveys such as the Dark Energy Survey and the Legacy Survey of Space and Time.

The circumgalactic medium (CGM) encodes signatures of the galaxy-formation process, including the interaction of galactic outflows driven by stellar and supermassive black hole (SMBH) feedback with the gaseous halo. Moving beyond spherically symmetric radial profiles, we study the \textit{angular} dependence of CGM properties around $z=0$ massive galaxies in the IllustrisTNG simulations. We characterize the angular signal of density, temperature, and metallicity of the CGM as a function of galaxy stellar mass, halo mass, distance, and SMBH mass, via stacking. TNG predicts that the CGM is anisotropic in its thermodynamical properties and chemical content over a large mass range, $M_*\sim10^{10-11.5}M_\odot$. Along the minor axis directions, gas density is diluted, whereas temperature and metallicity are enhanced. These feedback-induced anisotropies in the CGM have a magnitude of $0.1-0.3$ dex, extend out to the halo virial radius, and peak at Milky Way-like masses, $M_*\sim10^{10.8}M_\odot$. In TNG, this mass scale corresponds to the onset of efficient SMBH feedback and the production of strong outflows. By comparing the anisotropic signals predicted by TNG versus other simulations -- Illustris and EAGLE -- we find that each simulation produces distinct signatures and mass dependencies, implying that this phenomenon is sensitive to the underlying physical models. Finally, we explore X-ray emission as an observable of this CGM anistropy, finding that future X-ray observations, including the eROSITA all-sky survey, will be able to detect and characterize this signal, particularly in terms of an angular modulation of the X-ray hardness.

Metal-poor massive stars dominate the light we observe from star-forming dwarf galaxies and may have produced the bulk of energetic photons that reionized the universe at high redshift. Yet, the rarity of observations of individual O stars below the $20\%$ solar metallicity ($Z_\odot$) of the Small Magellanic Cloud (SMC) hampers our ability to model the ionizing fluxes of metal-poor stellar populations. We present new Hubble Space Telescope far-ultraviolet (FUV) spectra of three O-dwarf stars in the galaxies Leo P ($3\%\,Z_\odot$), Sextans A ($6\%\,Z_\odot$), and WLM ($14\%\,Z_\odot$). We quantify equivalent widths of photospheric metal lines and strengths of wind-sensitive features, confirming that both correlate with metallicity. We infer the stars' fundamental properties by modeling their FUV through near-infrared spectral energy distributions and identify stars in the SMC with similar properties to each of our targets. Comparing to the FUV spectra of the SMC analogs suggests that (1) the star in WLM has an SMC-like metallicity, and (2) the most metal-poor star in Leo P is driving a much weaker stellar wind than its SMC counterparts. We measure projected rotation speeds and find that the two most metal-poor stars have high $v \,\mathrm{sin}(i)\,\geq\,290\,\mathrm{km}\,\mathrm{s}^{-1}$, and estimate just a $3-6\%$ probability of finding two fast rotators if the metal-poor stars are drawn from the same $v \,\mathrm{sin}(i)$ distribution observed for O dwarfs in the SMC. These observations suggest that models should include the impact of rotation and weak winds on ionizing flux to accurately interpret observations of metal-poor galaxies in both the near and distant universe.

We contrast the latest observations of the cosmic metal density in neutral gas ($\rho_{\rm met,neu}$) with three cosmological galaxy evolution simulations: L-GALAXIES 2020, TNG100, and EAGLE. We find that the fraction of total metals that are in neutral gas is $<40$ per cent at $3\lesssim{} z \lesssim{} 5$ in these simulations, whereas observations of damped Lyman-$\alpha$ (DLA) systems suggest $\gtrsim{}85$ per cent. In all three simulations, hot, low-density gas is also a major contributor to the cosmic metal budget, even at high redshift. By considering the evolution in cosmic SFR density ($\rho_{\rm SFR}$), neutral gas density ($\rho_{\rm HI}$), and mean gas-phase metallicity ($[\langle{}{\rm M/H}\rangle{}]_{\rm neu}$), we determine two possible ways in which the $\rho_{\rm met,neu}$ observed in DLAs at high redshift can be matched by simulations: (a) $\rho_{\rm SFR}$ at $z\gtrsim{}3$ is greater than inferred from current FUV observations, or (b) current high-redshift DLA metallicity samples have a higher mean host mass than the overall galaxy population. If the first is correct, TNG100 would match the ensemble data best, however there would be an outstanding tension between the currently observed $\rho_{\rm SFR}$ and $\rho_{\rm met,neu}$. If the second is correct, L-GALAXIES 2020 would match the ensemble data best, but would require an increase in neutral gas mass inside subhaloes above $z\sim{}2.5$. If neither is correct, EAGLE would match the ensemble data best, although at the expense of over-estimating $[\langle{}$M/H$\rangle{}]_{\rm neu}$. Modulo details related to numerical resolution and HI mass modelling in simulations, these incompatibilities highlight current tensions between key observed cosmic properties at high redshift.

We use the Sherwood-Relics suite of hybrid hydrodynamical and radiative transfer simulations to model the effect of inhomogeneous reionisation on the 1D power spectrum of the Lyman-$\alpha$ forest transmitted flux at redshifts $4.2\leq z \leq 5$. Relative to models that assume a homogeneous UV background, reionisation suppresses the power spectrum at small scales, $k \sim 0.1\rm\,km^{-1}\,s$, by $\sim 10$ per cent because of spatial variations in the thermal broadening kernel and the divergent peculiar velocity field associated with over-pressurised intergalactic gas. On larger scales, $k<0.03\rm\,km^{-1}\,s$, the power spectrum is instead enhanced by $10$-$50$ per cent by large scale spatial variations in the neutral hydrogen fraction. The effect of inhomogeneous reionisation must therefore be accounted for in analyses of forthcoming high precision measurements. We provide a correction for the Lyman-$\alpha$ forest power spectrum at $4.1\leq z \leq 5.4$ in a form that can be easily applied within other parameter inference frameworks. We perform a Bayesian analysis of mock data to assess the extent of systematic biases that may arise in measurements of the intergalactic medium if ignoring this correction. At the scales probed by current high resolution Lyman-$\alpha$ forest data at $z>4$, $0.006 \rm \,km^{-1}\,s\leq k \leq 0.2 \rm\, km^{-1}\,s$, we find inhomogeneous reionisation does not introduce any significant bias in thermal parameter recovery for the current measurement uncertainties of $\sim 10$ per cent. However, for $5$ per cent uncertainties, $\sim 1\sigma$ shifts between the estimated and true parameters occur.

Giant star-forming regions (clumps) are widespread features of galaxies at $z \approx 1-4$. Theory predicts that they can play a crucial role in galaxy evolution if they survive to stellar feedback for > 50 Myr. Numerical simulations show that clumps' survival depends on the stellar feedback recipes that are adopted. Up to date, observational constraints on both clumps' outflows strength and gas removal timescale are still uncertain. In this context, we study a line-emitting galaxy at redshift $z \simeq 3.4$ lensed by the foreground galaxy cluster Abell 2895. Four compact clumps with sizes $\lesssim$ 280 pc and representative of the low-mass end of clumps' mass distribution (stellar masses $\lesssim 2\times10^8\ {\rm M}_\odot$) dominate the galaxy morphology. The clumps are likely forming stars in a starbursting mode and have a young stellar population ($\sim$ 10 Myr). The properties of the Lyman-$\alpha$ (Ly$\alpha$) emission and nebular far-ultraviolet absorption lines indicate the presence of ejected material with global outflowing velocities of $\sim$ 200-300 km/s. Assuming that the detected outflows are the consequence of star formation feedback, we infer an average mass loading factor ($\eta$) for the clumps of $\sim$ 1.8 - 2.4 consistent with results obtained from hydro-dynamical simulations of clumpy galaxies that assume relatively strong stellar feedback. Assuming no gas inflows (semi-closed box model), the estimates of $\eta$ suggest that the timescale over which the outflows expel the molecular gas reservoir ($\simeq 7\times 10^8\ \text{M}_\odot$) of the four detected low-mass clumps is $\lesssim$ 50 Myr.

Under the right conditions brown dwarfs that gain enough mass late in their lives to cross the hydrogen burning limit will not turn into low-mass stars, but rather remain essentially brown dwarf-like. While these objects, called either beige dwarfs or over-massive brown dwarfs, may exist in principle, it remains unclear exactly how they would form astrophysically. We show that accretion from AGB winds, aided by the wind Roche lobe overflow mechanism, is likely to produce a substantial population of observable overmassive brown dwarfs, though other mechanisms are still plausible. Specifically we predict that sun-like stars born with a massive brown dwarf companion on an orbit with a semi-major axis of order 10 AU will likely produce overmassive brown dwarfs, which may be found today as companions to the donor star's remnant white dwarf. The identification and characterization of such an object would produce unique constraints on binary evolution because there is a solid upper limit on the brown dwarf's initial mass.

We present an analysis of historical multi-wavelength emission of the Changing Look (CL) Active Galactic Nucleus (AGN) in NGC 2992, covering epochs ranging from 1978 to 2021, as well as new X-ray and optical spectra. The galaxy presents multiple Seyfert type transitions from type 2 to intermediate-type, losing and regaining its H$\alpha$ BEL recurrently. In X-rays, the source shows intrinsic variability with the absorption corrected luminosity varying by a factor of $\sim$ 40. We rule out tidal disruption events or variable obscuration as causes of the type transitions and show that the presence and the flux of the broad H$\alpha$ emission line are directly correlated with the 2-10 keV X-ray luminosity (L$_{2-10}$): the component disappears at L$_{2-10} \leq 2.6\times10^{42}$\ergcms, this value translates into an Eddington ratio ($\lambda_{\rm Edd}$) of $\sim$ 1\%. The $\lambda_{\rm Edd}$ in which the BEL transitions occur is the same as the critical value at which there should be a state transition between a radiatively inefficient accretion flow (RIAF) and a thin accretion disk, such similarity suggests that the AGN is operating at the threshold mass accretion rate between the two accretion modes. We find a correlation between the narrow Fe K$\alpha$ flux and $\lambda_{\rm Edd}$, and an anti-correlation between full-width at half maximum of H$\alpha$ BEL and $\lambda_{\rm Edd}$, in agreement with theoretical predictions. Two possible scenarios for type transitions are compatible with our results: either the dimming of the AGN continuum, which reduces the supply of ionising photons available to excite the gas in the Broad Line Region (BLR), or the fading of the BLR structure itself occurs as the low accretion rate is not able to sustain the required cloud flow rate in a disk-wind BLR model.

We use hydrodynamical simulations of star-forming gas with stellar feedback and sink particles (proxies for young stellar objects, i.e., YSOs) to produce and analyze synthetic 1.1mm continuum observations at different distances (150 - 1000pc) and ages (0.49 - 1.27 Myr). We characterize how the inferred core properties, including mass, size, and clustering with respect to diffuse natal gas structure, change with distance, cloud evolution, and the presence of YSOs. We find that atmospheric filtering and core segmentation treatments have distance-dependent impacts on the resulting core properties for d < 300pc and 500pc, respectively, which dominate over evolutionary differences. Concentrating on synthetic observations at further distances (650-1000pc), we find a growing separation between the inferred sizes and masses of cores with and without YSOs in the simulations, which is not seen in recent observations of the Mon R2 cloud at 860pc. We find that the synthetic cores cluster in smaller groups, and their mass densities are correlated with gas column density over a much narrower range, than the Mon R2 observations. Such differences limit applicability of the evolutionary predictions we report here and motivate future efforts to adapt our synthetic observation and analysis framework to next generation simulations such as STARFORGE. These predictions and systematic characterizations will help guide analysis of cores for the upcoming TolTEC Clouds to Cores Legacy Survey on the Large Millimeter Telescope Alfonso Serrano (LMT).

We present a high-contrast imaging search for Pa$\beta$ line emission from protoplanets in the PDS~70 system with Keck/OSIRIS integral field spectroscopy. We applied the high-resolution spectral differential imaging technique to the OSIRIS $J$-band data but did not detect the Pa$\beta$ line at the level predicted using the parameters of \cite{Hashimoto2020}. This lack of Pa$\beta$ emission suggests the MUSE-based study may have overestimated the line width of H$\alpha$. We compared our Pa$\beta$ detection limits with the previous H$\alpha$ flux and H$\beta$ limits and estimated $A_{\rm V}$ to be $\sim0.9$ and 2.0 for PDS~70~b and c respectively. In particular, PDS~70~b's $A_{\rm V}$ is much smaller than implied by high-contrast near-infrared studies, which suggests the infrared-continuum photosphere and the hydrogen-emitting regions exist at different heights above the forming planet.

Protoplanetary disks are dust- and gas-rich structures surrounding protostars. Depending on the distance from the protostar, this dust is thermally processed to different degrees and accreted to form bodies of varying chemical compositions. The primordial accretion processes occurring in the early protoplanetary disk such as chondrule formation and metal segregation are not well understood. One way to constrain them is to study the morphology and composition of forsteritic grains from the matrix of carbonaceous chondrites. Here, we present high-resolution ptychographic X-ray nanotomography and multimodal chemical micro-tomography (X-ray diffraction and X-ray fluorescence) to reveal the early history of forsteritic grains extracted from the matrix of the Murchison CM2.5 chondrite. The 3D electron density maps revealed, at unprecedented resolution (64~nm), spherical inclusions containing Fe-Ni, very little silica-rich glass and void caps (i.e., volumes where the electron density is consistent with conditions close to vacuum) trapped in forsterite. The presence of the voids along with the overall composition, petrological textures, and shrinkage calculations is consistent with the grains experiencing one or more heating events with peak temperatures close to the melting point of forsterite ($\sim$2100~K) and subsequently cooled and contracted, in agreement with chondrule-forming conditions.

Many young and intermediate age massive stellar clusters host bimodal distributions in the rotation rates of their stellar populations, with a dominant peak of rapidly rotating stars and a secondary peak of slow rotators. The origin of this bimodal rotational distribution is currently debated and two main theories have been put forward in the literature. The first is that all/most stars are born as rapid rotators and that interacting binaries brake a fraction of the stars, resulting in two populations. The second is that the rotational distribution is a reflection of the early evolution of pre-main sequence stars, in particular, whether they are able to retain or lose their protoplanetary discs during the first few Myr. Here, we test the binary channel by exploiting multi-epoch VLT/MUSE observations of NGC 1850, a 100Myr massive cluster in the LMC, to search for differences in the binary fractions of the slow and fast rotating populations. If binarity is the cause of the rotational bimodality, we would expect that the slowly rotating population should have a much larger binary fraction than the rapid rotators. However, in our data we detect similar fractions of binary stars in the slow and rapidly rotating populations (5.9+/-1.1% and 4.5+/-0.6%, respectively).Hence, we conclude that binarity is not a dominant mechanism in the formation of the observed bimodal rotational distributions.

Coronal Mass Ejections (CMEs) drive space weather activity at Earth and throughout the solar system. Current CME-related space weather predictions rely on information reconstructed from coronagraphs, sometimes from only a single viewpoint, to drive a simple interplanetary propagation model, which only gives the arrival time or limited additional information. We present the coupling of three established models into OSPREI (Open Solar Physics Rapid Ensemble Information), a new tool that describes Sun-to-Earth CME behavior, including the location, orientation, size, shape, speed, arrival time, and internal thermal and magnetic properties, on the timescale needed for forecasts. First, ForeCAT describes the trajectory that a CME takes through the solar corona. Second, ANTEATR simulates the propagation, including expansion and deformation, of a CME in interplanetary space and determines the evolution of internal properties via conservation laws. Finally, FIDO produces in situ profiles for a CME's interaction with a synthetic spacecraft. OSPREI includes ensemble modeling by varying each input parameter to probe any uncertainty in their values, yielding probabilities for all outputs. Standardized visualizations are automatically generated, providing easily-accessible, essential information for space weather forecasting. We show OSPREI results for a CME observed in the corona on 2021 April 22 and at Earth on 2021 April 25. We approach this CME as a forecasting proof-of-concept, using information analogous to what would be available in real time rather than fine-tuning input parameters to achieve a best fit for a detailed scientific study. The OSPREI prediction shows good agreement with the arrival time and in situ properties.

We present optical imaging and spectroscopy of SN\,2018lfe, which we classify as a Type I superluminous supernova (SLSN-I) at a redshift of $z = 0.3501$ with a peak absolute magnitude of $M_r\approx -22.1$ mag, one of the brightest SLSNe discovered. SN\,2018lfe was identified for follow-up using our FLEET machine learning pipeline. Both the light curve and the spectra of SN\,2018lfe are consistent with the broad population of SLSNe. We fit the light curve with a magnetar central engine model and find an ejecta mass of $M_{\rm ej}\approx 3.8$ M$_\odot$, a magnetar spin period of $P\approx 2.9$ ms and a magnetic field strength of $B_{\perp}\approx 2.8\times 10^{14}$ G. The magnetic field strength is near the top of the distribution for SLSNe, while the spin period and ejecta mass are near the median values of the distribution for SLSNe. From late-time imaging and spectroscopy we find that the host galaxy of SN\,2018lfe has an absolute magnitude of $M_r\approx -17.85$, ($L_B \approx 0.029$ $L^*$), and an inferred metallicity of $Z\approx 0.3$ Z$_\odot$, and star formation rate of $\approx 0.8$ M$_\odot$ yr$^{-1}$.

Gravitationally bound companions to stars enable determinations of their masses, and offer clues to their formation, evolution and dynamical histories. So motivated, we have carried out a speckle imaging survey of eight of the nearest and brightest Wolf-Rayet (WR) stars to directly measure the frequency of their resolvable companions, and to search for much fainter companions than hitherto possible. We found one new, close companion to each of WR 113, WR 115 and WR 120 in the separation range 0.2" - 1.2". Our results provide more evidence that similar-brightness, close companions to WR stars are common. More remarkably, they also demonstrate that the predicted, but much fainter and thus elusive companions to WR stars are now within reach of modern speckle cameras on 8m class telescopes by finding the first example. The new companion to WR 113 is just 1.16" distant from it, and is 8 magnitudes fainter than the WR star. The empirical probability of a chance line-of-sight of the faint companion at the position of WR 113 is < 0.5%, though we cannot yet prove or disprove if the two stars are gravitationally bound. If these three new detections are physical companions we suggest, based on their narrowband magnitudes, colors, reddenings and GAIA distances that the companions to WR113, WR 115 and WR 120 are an F-type dwarf, an early B-type dwarf, and a WNE-type WR star, respectively.

We use the $k$-nearest neighbor probability distribution function ($k$NN-PDF, Banerjee & Abel 2021) to assess convergence in a scale-free $N$-body simulation. Compared to our previous two-point analysis, the $k$NN-PDF allows us to quantify our results in the language of halos and numbers of particles, while also incorporating non-Gaussian information. We find good convergence for 32 particles and greater at densities typical of halos, while 16 particles and fewer appears unconverged. Halving the softening length extends convergence to higher densities, but not to fewer particles. Our analysis is less sensitive to voids, but we analyze a limited range of underdensities and find evidence for convergence at 16 particles and greater even in sparse voids.

Young Supernova remnants (SNRs) with smaller angular sizes are likely missing from existing radio SNR catalogues, caused by observational constraints and selection effects. In order to find new compact radio SNR candidates, we searched the high angular resolution (25") THOR radio survey of the first quadrant of the galaxy. We selected sources with non-thermal radio spectra. HI absorption spectra and channel maps were used to identify which sources are galactic and to estimate their distances. Two new compact SNRs were found: G31.299$-$0.493 and G18.760$-$0.072, of which the latter was a previously suggested SNR candidate. The distances to these SNRs are 5.0 $\pm$ 0.3 kpc and 4.7 $\pm$ 0.2 kpc, respectively. Based on the SN rate in the galaxy or on the statistics of known SNRs, we estimate that there are 15$-$20 not yet detected compact SNRs in the galaxy and that the THOR survey area should contain three or four. Our detection of two SNRs (half the expected number) is consistent with the THOR sensitivity limit compared with the distribution of integrated flux densities of SNRs.

Stars produce explosive flares, which are believed to be powered by the release of energy stored in coronal magnetic field configurations. It has been shown that solar flares exhibit energy distributions typical of self-organized critical systems. This study applies a novel flare detection technique to data obtained by NASA's TESS mission and identifies $\sim10^6$ flaring events on $\sim10^5$ stars across spectral types. Our results suggest that magnetic reconnection events that maintain the topology of the magnetic field in a self-organized critical state are ubiquitous among stellar coronae.

We study the influence of relativity on the chaotic properties and dynamical outcomes of an unstable triple system; the Pythagorean three-body problem. To this end, we extend the Brutus N-body code to include Post-Newtonian pairwise terms up to 2.5 order, and the first order Taylor expansion to the Einstein-Infeld-Hoffmann equations of motion. The degree to which our system is relativistic depends on the scaling of the total mass (the unit size was 1 parsec). Using the Brutus method of convergence, we test for time-reversibility in the conservative regime, and demonstrate that we are able to obtain definitive solutions to the relativistic three-body problem. It is also confirmed that the minimal required numerical accuracy for a successful time-reversibility test correlates with the amplification factor of an initial perturbation. When we take into account dissipative effects through gravitational wave emission, we find that the duration of the resonance, and the amount of exponential growth of small perturbations depend on the mass scaling. For a unit mass <= 10 MSun, the system behavior is indistinguishable from the Newtonian case, and the resonance always ends in a binary and one escaping body. For a mass scaling up to 1e7 MSun, relativity gradually becomes more prominent, but the majority of the systems still dissolve. The first mergers start to appear for a mass of ~1e5 MSun, and between 1e7 MSun and 1e9 MSun all systems end prematurely in a merger. These mergers are preceded by a gravitational wave driven in-spiral. For a mass scaling >= 1e9 MSun, all systems result in a gravitational wave merger upon the first close encounter. Relativistic three-body encounters thus provide an efficient pathway for resolving the final parsec problem. The onset of mergers at the characteristic mass scale of 1e7 MSun potentially leaves an imprint in the mass function of supermassive black holes.

We conducted a project of reinvestigating the 2017--2019 microlensing data collected by the high-cadence surveys with the aim of finding planets that were missed due to the deviations of planetary signals from the typical form of short-term anomalies. The project led us to find three planets including KMT-2017-BLG-2509Lb, OGLE-2017-BLG-1099Lb, and OGLE-2019-BLG-0299Lb. The lensing light curves of the events have a common characteristic that the planetary signals were produced by the crossings of faint source stars over the resonant caustics formed by giant planets located near the Einstein rings of host stars. For all planetary events, the lensing solutions are uniquely determined without any degeneracy. It is estimated that the host masses are in the range of $0.45\lesssim M/M_\odot \lesssim 0.59$, which corresponds to early M to late K dwarfs, and thus the host stars are less massive than the sun. On the other hand, the planets, with masses in the range of $2.1\lesssim M/M_{\rm J}\lesssim 6.2$, are heavier than the heaviest planet of the solar system, that is, Jupiter. The planets in all systems lie beyond the snow lines of the hosts, and thus the discovered planetary systems, together with many other microlensing planetary systems, support that massive gas-giant planets are commonplace around low-mass stars. We discuss the role of late-time high-resolution imaging in clarifying resonant-image lenses with very faint sources.

We present correction terms that allow delete-one Jackknife and Bootstrap methods to be used to recover unbiased estimates of the data covariance matrix of the two-point correlation function $\xi\left(\mathbf{r}\right)$. We demonstrate the accuracy and precision of this new method using a large set of 1000 QUIJOTE simulations that each cover a comoving volume of $1\rm{\left[h^{-1}Gpc\right]^3}$. The corrected resampling techniques accurately recover the correct amplitude and structure of the data covariance matrix as represented by its principal components. Our corrections for the internal resampling methods are shown to be robust against the intrinsic clustering of the cosmological tracers both in real- and redshift space using two snapshots at $z=0$ and $z=1$ that mimic two samples with significantly different clustering. We also analyse two different slicing of the simulation volume into $n_{\rm sv}=64$ or $125$ sub-samples and show that the main impact of different $n_{\rm sv}$ is on the structure of the covariance matrix due to the limited number of independent internal realisations that can be made given a fixed $n_{\rm sv}$.

The Experimental complex NEVOD includes several different setups for studying various components of extensive air showers (EAS) in the energy range from 10^10 to 10^18 eV. The NEVOD-EAS array for detection of the EAS electron-photon component began its data taking in 2018. It is a distributed system of scintillation detectors installed over an area of about 10^4 m^2. A distinctive feature of this array is its cluster organization with different-altitude layout of the detecting elements. The main goal of the NEVOD-EAS array is to obtain an estimation of the primary particle energy for events measured by various detectors of the Experimental complex NEVOD. This paper describes the design, operation principles and data processing of the NEVOD-EAS array. The criteria for the event selection and the accuracy of the EAS parameters reconstruction obtained on the simulated events are discussed. The results of the preliminary analysis of experimental data obtained during a half-year operation are presented.

Canopus, the brightest and closest yellow supergiant to our Solar System, offers a unique laboratory for understanding the physics of evolved massive stars. The accurate and precise PIONIER data allowed us to simultaneously measure the angular diameter and the limb darkening (LD) profile using different analytical laws. We found that the power-law LD, being also in agreement with predictions from stellar atmosphere models, reproduces the interferometric data well. For this model we measured an angular diameter of $7.184 \pm 0.0017 \pm 0.029$ mas and an LD coefficient of $0.1438 \pm 0.0015$, which are respectively $\gtrsim 5$ and $\sim15-25$ more precise than in our previous A\&A paper on Canopus from 2008. From a dedicated analysis of the interferometric data, we also provide new constraints on the putative presence of weak surface inhomogeneities. Additionally, we analyzed the SED in a innovative way by simultaneously fitting the reddening-related parameters and the stellar effective temperature and gravity. We find that a model based on two effective temperatures is much better at reproducing the whole SED, from which we derived several parameters, including a new bolometric flux estimate. The Canopus angular diameter and LD measured in this work with PIONIER are the most precise to date, with a direct impact on several related fundamental parameters. Moreover, thanks to our joint analysis, we were able to determine a set of fundamental parameters that simultaneously reproduces both high-precision interferometric data and a good quality SED and, at the same time, agrees with stellar evolution models.

Schulz (2017) galactic scaling rules, which include baryonic Tully-Fisher relation, have been surveyed in this work within the context of a modified dynamical model. These scaling relations are derived by employing the virial theorem and applying equilibrium and stability conditions. The scaling rules are also obtained by dimensional analysis of an integral relation between surface density and circular velocity of disk galaxies. To check the validity of the scaling relations based on observational data, we have defined, based on the properties of the model, the proper equilibrium size $R_{eq}$ and equilibrium velocity $V_{eq}$ of systems. By employing these measures of length and velocity, SPARC data ( Lelli et al. 2016a ) is used to analyze the results. The viability of the scaling relations is tested and it is shown that, compared to some other measures of length and velocity, $R_{eq}$ and $V_{eq}$ provide the closest fits to the theoretical predictions. We have compared our results with prior works and have concluded that the set of baryonic Tully-Fisher relation plus mass-size relation ( or mass-velocity ) provides an appropriate description of the general characteristics of the systems. Lastly, it is shown that these scaling relations predict a certain evolution of galactic properties with redshift. This behavior provides a chance to examine the cosmic evolution of the present modified dynamical model in future works.

With the aim of pushing the limiting magnitude of interferometric instruments, the need for wide-band detection channels and for a coordinated operation of different instruments has considerably grown in the field of long-baseline interferometry. For this reason, the Center for High Angular Resolution Astronomy (CHARA), an array of six telescopes, requires a new configuration of longitudinal dispersion compensators to keep the fringe contrast above 95 per cent simultaneously in all spectral bands, while preserving the transmission above 85 per cent. In this paper, we propose a new method for defining the longitudinal dispersion compensators (LDC) suited for multiband observations. A literal approximation of the contrast loss resulting from the dispersion residues enables us to define a general criterion for fringe contrast maximization on several bands simultaneously. The optimization of this criterion leads to a simple solution with only two LDC stages per arm and existing differential delay lines, to the glass choice and a simple linear formula for thickness control of all these media. A refined criterion can also take into account glass transmission. After presenting this criterion, we give the optimal solution (medium, configuration) and its expected performance for the planned observing modes on CHARA.

Observations in the UV-regime are very important for exoplanet research, because many diagnostically important lines for studying stellar activity are in this regime. Studying stellar activity is not only important because of its negative effects on the determination planetary parameters, but also because the XUV-radiation from the host stars affects the photochemistry and the erosion of planetary atmospheres . Unfortunately, the XUV-region is only accessible from space. However, since the XUV-radiation is correlated with the CaII,HK-lines, we can use these lines to study the XUV radiation indirectly. The CaIIHK lines for relatively bright stars can be observed with PLATOspec, a new high-resolution echelle spectrograph in development for the ESO 1.5m telescope at La Silla. One advantage compared to instruments on larger telescopes will be that large programs can be carried out. There will be two modes for obtaining precise RV-measurements. In the future, the CUBES instrument on the VLT will be able to study the same lines to probe the XUV-radiation in much fainter targets.

We report the result of the first search for multipoint in situ and imaging observations of interplanetary coronal mass ejections (ICMEs) starting with the first Solar Orbiter data in April 2020 to April 2021. A data exploration analysis is performed including visualizations of the magnetic field and plasma observations made by the five spacecraft Solar Orbiter, BepiColombo, Parker Solar Probe, Wind and STEREO-A, in connection with coronagraph and heliospheric imaging observations from STEREO-Ahead/SECCHI and SOHO/LASCO. We identify ICME events that could be unambiguously followed with the STEREO-A heliospheric imagers during their interplanetary propagation to their impact at the aforementioned spacecraft, and look for events where the same ICME is seen in situ by widely separated spacecraft. We highlight two events: (1) a small streamer blowout CME on 2020 June 23 observed with a triple lineup by Parker Solar Probe, BepiColombo and Wind, guided by imaging with STEREO-A, and (2) the first fast CME of solar cycle 25 ($ \approx 1600$ km s$^{-1}$) on 2020 Nov 29 observed in situ by Parker Solar Probe and STEREO-A. These results are useful for modeling the magnetic structure of ICMEs, the interplanetary evolution and global shape of their flux ropes and shocks, and for studying the propagation of solar energetic particles. The combined data from these missions is already turning out to be a treasure trove for space weather research and is expected to become even more valuable with an increasing number of ICME events expected during the rise and maximum of solar cycle 25.

The study of infall motion helps us to understand the initial stages of star formation. In this paper, we use the IRAM 30-m telescope to make mapping observations of 24 infall sources confirmed in previous work. The lines we use to track gas infall motions are HCO+ (1-0) and H13CO+ (1-0). All 24 sources show HCO+ emissions, while 18 sources show H13CO+ emissions. The HCO+ integrated intensity maps of 17 sources show clear clumpy structures; for the H13CO+ line, 15 sources show clumpy structures. We estimated the column density of HCO+ and H13CO+ using the RADEX radiation transfer code, and the obtained [HCO+]/[H2] and [H13CO+]/[HCO+] of these sources are about 10^-11 ~ 10^-7 and 10^-3~1, respectively. Based on the asymmetry of the line profile of the HCO+, we distinguish these sources: 19 sources show blue asymmetric profiles, and the other sources show red profiles or symmetric peak profiles. For eight sources that have double-peaked blue line profiles and signal-to-noise ratios greater than 10, the RATRAN model is used to fit their HCO^+ (1-0) lines, and to estimate their infall parameters. The mean Vin of these sources are 0.3 ~ 1.3 km/s, and the Min are about 10^-3 ~ 10^-4 Msun/yr , which are consistent with the results of intermediate or massive star formation in previous studies. The Vin estimated from the Myers model are 0.1 ~ 1.6 km/s, and the Min are within 10^-3 ~ 10^-5 Msun/yr. In addition, some identified infall sources show other star-forming activities, such as outflows and maser emissions. Especially for those sources with a double-peaked blue asymmetric profile, most of them have both infall and outflow evidence.

We explore the potential of an artificial neural network (ANN) based method intelligence to probe the propagation of cosmic $\gamma$-ray photons in the extragalactic Universe. The journey of $\gamma$-rays emitted from a distant source like blazar to the observer at the Earth is impeded by the absorption through the interaction with the extragalactic background light (EBL), leading to an electron-positron pair production. This process dominates for gamma ray photons with energy above 10 GeV propagating over the cosmological distances. The effect of $\gamma$-ray attenuation is characterized by a physical quantity called \emph{optical depth}, which strongly depends on the $\gamma$-ray photon energy, redshift of the source, and density of the EBL photons. We estimate the optical depth values for $\gamma$-ray energies above 10 GeV emitted from the sources at redshifts in the range 0.01 to 1 using three different and most promising EBL models. These optical depth estimates are randomly divided into two data sets for training and testing of the ANN using energy, redshift as inputs and optical depth as output. The optimization of ANN-performance for each EBL model employs standard back-propagation (BP) and radial-basis function (RBF) algorithms. The performance of the ANN model using the RBF is found to be superior to the BP method. In particular, the RBF-ANN with 40 neurons in the hidden layer corresponding to the EBL model proposed by Finke et al. (2010) shows the best performance for the propagation of $\gamma$-rays in the Universe.

The growth model of black hole is still a controversial topic. In the stationary metric, all in-falling matter must be accumulated outside the event horizon of the black hole, as clocked by a distant external observer. In the time-dependent metric, all in-falling matter can fall into the event horizon of the final black hole within very short time. We test these two growth models by joining LIGO and Insight-HXMT observations. We find the stationary model is inconsistent with LIGO and Insight-HXMT observations.

The TESS space telescope is collecting continuous, high-precision optical photometry of stars throughout the sky, including thousands of RR Lyrae stars. In this paper, we present results for an initial sample of 118 nearby RR Lyrae stars observed in TESS Sectors 1 and 2. We use differential-image photometry to generate light curves and analyse their mode content and modulation properties. We combine accurate light curve parameters from TESS with parallax and color information from the Gaia mission to create a comprehensive classification scheme. We build a clean sample, preserving RR Lyrae stars with unusual light curve shapes, while separating other types of pulsating stars. We find that a large fraction of RR Lyrae stars exhibit various low-amplitude modes, but the distribution of those modes is markedly different from those of the bulge stars. This suggests that differences in physical parameters have an observable effect on the excitation of extra modes, potentially offering a way to uncover the origins of these signals. However, mode identification is hindered by uncertainties when identifying the true pulsation frequencies of the extra modes. We compare mode amplitude ratios in classical double-mode stars to stars with extra modes at low amplitudes and find that they separate into two distinct groups. Finally, we find a high percentage of modulated stars among the fundamental-mode pulsators, but also find that at least 28% of them do not exhibit modulation, confirming that a significant fraction of stars lack the Blazhko effect.

A BRDF for the VisorSat model of Starlink satellites is described. The parameter coefficients were determined by least squares fitting to more than 10,000 magnitudes recorded by the MMT-9 robotic observatory. The BRDF is defined in a satellite-centered coordinate system (SCCS) which corresponds to the physical shape of the spacecraft and to the direction of the Sun. The three parameters of the model in the SCCS are the elevations of the Sun and of MMT-9 along with the azimuth of MMT-9 relative to that of the Sun. The mean VisorSat magnitude at a standardized distance of 1,000 km is 6.84 and the RMS of the distribution around that mean is 1.05. After the magnitudes are adjusted with the BRDF, the RMS reduces to 0.51. The set of MMT-9 observations transformed to the SCCS is available from the author.

AT2019wey is a new galactic X-ray binary that was first discovered as an optical transient by the Australia Telescope Large Area Survey (ATLAS) on December 7, 2019. AT2019wey consists of a black hole candidate as well as a low-mass companion star ($M_{\text {star }} \lesssim 0.8 M_{\odot}$) and is likely to have a short orbital period ($P_{\text {orb }} \lesssim 8$ h). Although AT2019wey began activation in the X-ray band during almost the entire outburst on March 8, 2020, it did not enter the soft state during the entire outburst. In this study, we present a detailed spectral analysis of AT2019wey in the low/hard state during its X-ray outburst on the basis of Nuclear Spectroscopic Telescope Array \emph observations. We obtain tight constraints on several of its important physical parameters by applying the State-of-art \texttt{relxill} relativistic reflection model family. In particular, we determine that the measured inner radius of the accretion disk is most likely to have extended to the innermost stable circular orbit (ISCO) radius, i.e., $R_{\text{in}}=1.38^{+0.23}_{-0.16}~R_{\text{ISCO}}$. Hence, assuming $R_{\text{in}}$=$R_{\text{ISCO}}$, we find the spin of AT2019wey to be $a_{*}\sim$ $0.97$, which is close to the extreme and an inner disk inclination angle of ~$i\sim$ $22 ^{\circ}$. Additionally, according to our adopted models, AT2019wey tends to have a relatively high iron abundance of $A_{\mathrm{Fe}}\sim$ 5 $A_{\mathrm{Fe}, \odot}$ and a high disk ionization state of $\log \xi\sim$ 3.4.

We measure the cross-correlation between galaxy groups constructed from DESI Legacy Imaging Survey DR8 and Planck CMB lensing, over overlapping sky area of 16876 $\rm deg^2$. The detections are significant and consistent with the expected signal of the large scale structure of the universe, over group samples of various redshift, mass and richness $N_{\rm g}$ and over various scale cuts. The overall S/N is 39 for a conservative sample with $N_{\rm g}\geq 5$, and increases to $48$ for the sample with $N_{\rm g}\geq 2$. Adopting the Planck 2018 cosmology, we constrain the density bias of groups with $N_{\rm g}\geq 5$ as $b_{\rm g}=1.31\pm 0.10$, $2.22\pm 0.10$, $3.52\pm 0.20$ at $0.1<z\leq 0.33$, $0.33<z\leq 0.67$, $0.67<z\leq1$ respectively. The value-added group catalog allows us to detect the dependence of bias on group mass with high significance. It also allows us to compare the measured bias with the theoretically predicted one using the estimated group mass. We find excellent agreement for the two high redshift bins. However, it is lower than the theory by $\sim 3\sigma$ for the lowest redshift bin. Another interesting finding is the significant impact of the thermal Sunyaev Zel'dovich (tSZ). It contaminates the galaxy group-CMB lensing cross-correlation at $\sim 30\%$ level, and must be deprojected first in CMB lensing reconstruction.

This work characterises the sky localization and early warning performance of networks of third generation gravitational wave detectors, consisting of different combinations of detectors with either the Einstein Telescope or Cosmic Explorer configuration in sites in North America, Europe and Australia. Using a Fisher matrix method which includes the effect of earth rotation, we estimate the sky localization uncertainty for $1.4\text{M}\odot$-$1.4\text{M}\odot$ binary neutron star mergers at distances $40\text{Mpc}$, $200\text{Mpc}$, $400\text{Mpc}$, $800\text{Mpc}$, $1600\text{Mpc}$, and an assumed astrophysical population up to redshift of 2 to characterize its performance for binary neutron star observations. We find that, for binary neutron star mergers at $200\text{Mpc}$ and a network consisting of the Einstein Telescope, Cosmic Explorer and an extra Einstein Telescope-like detector in Australia(2ET1CE), the upper limit of the size of the 90% credible region for the best localized 90% signals is $0.51\text{deg}^2$. For the simulated astrophysical distribution, this upper limit is $183.58\text{deg}^2$. If the Einstein Telescope-like detector in Australia is replaced with a Cosmic Explorer-like detector(1ET2CE), for $200\text{Mpc}$ case, the upper limit is $0.36\text{deg}^2$, while for astrophysical distribution, it is $113.55\text{deg}^2$. We note that the 1ET2CE network can detect 7.2% more of the simulated astrophysical population than the 2ET1CE network. In terms of early warning performance, we find that a network of 2ET1CE and 1ET2CE networks can both provide early warnings of the order of 1 hour prior to merger with sky localization uncertainties of 30 square degrees or less. Our study concludes that the 1ET2CE network is a good compromise between binary neutron stars detection rate, sky localization and early warning capabilities.

In this article, theory-based analytical methodologies of astrophysics employed in the modern era are suitably operated alongside a test research-grade telescope to image and determine the orbit of a near-earth asteroid from original observations, measurements, and calculations. Subsequently, its intrinsic orbital path has been calculated including the chance it would likely impact Earth in the time ahead. More so specifically, this case-study incorporates the most effective, feasible, and novel Gauss's Method in order to maneuver the orbital plane components of a planetesimal, further elaborating and extending our probes on a selected near-earth asteroid (namely the 12538-1998 OH) through the observational data acquired over a six week period. Utilizing the CCD (Charge Coupled Device) snapshots captured, we simulate and calculate the orbit of our asteroid as outlined in quite detailed explanations. The uncertainties and deviations from the expected values are derived to reach a judgement whether our empirical findings are truly reliable and representative measurements by partaking a statistical analysis based systematic approach. Concluding the study by narrating what could have caused such discrepancy of findings in the first place, if any, measures are put forward that could be undertaken to improve the test-case for future investigations. Following the calculation of orbital elements and their uncertainties using Monte Carlo analysis, simulations were executed with various sample celestial bodies to derive a plausible prediction regarding the fate of Asteroid 1998 OH. Finally, the astrometric and photometric data, after their precise verification, were officially submitted to the Minor Planet Center: an organization hosted by the Center for Astrophysics, Harvard and Smithsonian and funded by NASA, for keeping track of the asteroid's potential trajectories.

The radio astronomy group in the Indian Institute of Astrophysics (IIA) has been carrying out routine observations of radio emission from the solar corona at low frequencies (${\approx}$40-440MHz) at the Gauribidanur observatory, about 100km north of Bangalore. Since IIA has been performing regular observations of the solar photosphere and chromosphere using different optical telescopes in its Kodaikanal Solar Observatory (KSO) also, the possibilities of obtaining two-dimensional radio images of the solar chromosphere using low-cost instrumentation to supplement the optical observations are being explored. As a part of the exercise, recently the group had developed prototype instrumentation for interferometric observations of radio emission from the solar chromosphere at high frequencies (${\approx}$11.2GHz) using two commercial dish TV antennas. The hardware set-up and initial observations are presented.

Context. Insight into the conditions that drive the physics and chemistry in interstellar clouds is gained from determining the abundance and charge state of their components. Aims. We propose an evaluation of the C60:C60+ ratio in diffuse and translucent interstellar clouds that exploits electronic absorption bands so as not to rely on ambiguous IR emission measurements. Methods. The ratio is determined by analyzing archival spectra and literature data. Information on the cation population is obtained from published characteristics of the main diffuse interstellar bands attributed to C60+ and absorption cross sections already reported for the vibronic bands of the cation. The population of neutral molecules is described in terms of upper limit because the relevant vibronic bands of C60 are not brought out by observations. We revise the oscillator strengths reported for C60 and measure the spectrum of the molecule isolated in Ne ice to complete them. Results. We scale down the oscillator strengths for absorption bands of C60 and find an upper limit of approximately 1.3 for the C60:C60+ ratio. Conclusions. We conclude that the fraction of neutral molecules in the buckminsterfullerene population of diffuse and translucent interstellar clouds may be notable despite the non-detection of the expected vibronic bands. More certainty will require improved laboratory data and observations.

Gravitational wave (GW) detection in space probes GW spectrum that is inaccessible from the Earth. In addition to LISA project led by European Space Agency, and the DECIGO detector proposed by the Japan Aerospace Exploration Agency, two Chinese space-based GW observatories -- TianQin and Taiji -- are planned to be launched in the 2030s. TianQin has a unique concept in its design with a geocentric orbit. Taiji's design is similar to LISA, but is more ambitious with longer arm distance. Both facilities are complementary to LISA, considering that TianQin is sensitive to higher frequencies and Taiji probes similar frequencies but with higher sensitivity. In this Perspective we explain the concepts for both facilities and introduce the development milestones of TianQin and Taiji projects in testing extraordinary technologies to pave the way for future space-based GW detections. Considering that LISA, TianQin and Taiji have similar scientific goals, all are scheduled to be launched around the 2030s and will operate concurrently, we discuss possible collaborations among them to improve GW source localization and characterization.

The analysis of Fermi Large Area Telescope (LAT) gamma-ray data in a given Region Of Interest (RoI) usually consists of performing a binned log-likelihood fit in order to determine the sky model that, after convolution with the instrument response, best accounts for the distribution of observed counts. While tools are available to perform such a fit, it is not easy to check the goodness-of-fit. The difficulty of the assessment of the data/model agreement is twofold. First of all, the observed and predicted counts are binned in three dimensions (two spatial dimensions and one energy dimension) and comparing two 3D maps is not straightforward. Secondly, gamma-ray source spectra generally decrease with energy as the inverse of the energy square. As a consequence the number of counts above several GeV generally falls into the Poisson regime, which precludes performing a simple $\chi^2$ test. We propose a method that overcomes these two obstacles by producing and comparing spatially integrated count spectra for data and model at each pixel of the analysed RoI. The comparison is performed following a log-likelihood approach that extends the $\chi^2$ test to histograms with low statistics. This method can take into account likelihood weights that are used to account for systematic uncertainties. We optimize the new method so that it provides a fast and reliable tool to assess the goodness-of-fit of Fermi-LAT data and we use it to check the latest gamma-ray source catalog on 10~years of data.

We characterize the local (2-kpc sized) environments of Type Ia, II, and Ib/c supernovae (SNe) that have recently occurred in nearby ($d\lesssim50$ Mpc) galaxies. Using ultraviolet (UV, from GALEX) and infrared (IR, from WISE) maps of 359 galaxies and a sample of 472 SNe, we measure the star formation rate surface density ($\Sigma_{\rm SFR}$) and stellar mass surface density ($\Sigma_\star$) in a 2-kpc beam centered on each SN site. We show that core-collapse SNe are preferentially located along the resolved galactic star-forming main sequence, whereas Type Ia SNe are extended to lower values of $\Sigma_{\rm SFR}$ at fixed $\Sigma_\star$, indicative of locations inside quiescent galaxies or quiescent regions of galaxies. We also test how well the radial distribution of each SN type matches the radial distributions of UV and IR light in each host galaxy. We find that, to first order, the distributions of all types of SNe mirror that of both near-IR light (3.4 and 4.5 microns, tracing the stellar mass distribution) and mid-IR light (12 and 22 microns, tracing emission from hot, small grains), and also resemble our best-estimate $\Sigma_{\rm SFR}$. All types of SNe appear more radially concentrated than the UV emission of their host galaxies. In more detail, the distributions of Type II SNe show small statistical differences from that of near-IR light. We attribute this overall structural uniformity to the fact that within any individual galaxy, $\Sigma_{\rm SFR}$ and $\Sigma_\star$ track one another well, with variations in $\Sigma_{\rm SFR}/\Sigma_\star$ most visible when comparing between galaxies.

The VIIRS Day Night Band sensor on the Suomi NPP satellite provides almost a decade of observations of night light. The daily frequency of sampling, without the temporal averaging of annual composites, requires the distinction between apparent changes of imaged night light related to the imaging process and actual changes in the underlying sources of the light being imaged. This study characterizes night light variability over a range of spatial and temporal scales to provide a context for interpretation of changes on both subannual and interannual time scales. This analysis uses a combination of temporal moments, spatial correlation and Empirical Orthogonal Function (EOF) analysis. A key result is the pervasive heteroskedasticity of VIIRS monthly mean night light. Specifically, the monotonic decrease of temporal variability with increasing mean brightness. Anthropogenic night light is remarkably stable on subannual time scales. Overall variance partition derived from the eigenvalues of the spatiotemporal covariance matrix are 88%, 2% and 2% for spatial, seasonal and interannual variance in the most diverse geographic region on Earth (Eurasia). Heteroskedasticity is present in all areas for all months, suggesting that much, if not most, of observed month-to-month variability may result from luminance of otherwise stable sources subjected to multiple aspects of the imaging process varying in time. Given the skewed distribution of all night light arising from radial peripheral dimming of bright sources, even aggregate metrics using thresholds must be interpreted in light of the fact that much larger numbers of more variable low luminance pixels may statistically overwhelm smaller numbers of stable higher luminance pixels and cause apparent changes related to the imaging process to be interpreted as actual changes in the light sources.

Detectors using liquid xenon as target are widely deployed in rare event searches. Conclusions on the interacting particle rely on a precise reconstruction of the deposited energy which requires calibrations of the energy scale of the detector by means of radioactive sources. However, a microscopic calibration, i.e. the translation from the number of excitation quanta into deposited energy, also necessitates good knowledge of the energy required to produce single scintillation photons or ionisation electrons in liquid xenon. The sum of these excitation quanta is directly proportional to the deposited energy in the target. The proportionality constant is the mean excitation energy and is commonly known as $W$-value. Here we present a measurement of the $W$-value with electronic recoil interactions in a small dual-phase xenon time projection chamber with a hybrid (photomultiplier tube and silicon photomultipliers) photosensor configuration. Our result is based on calibrations at $\mathcal{O}(1-10 \, \mathrm{keV})$ with internal $^{37}$Ar and $^{83\text{m}}$Kr sources and single electron events. We obtain a value of $W=11.5 \, ^{+0.2}_{-0.3} \, \mathrm{(syst.)} \, \mathrm{eV}$, with negligible statistical uncertainty, which is lower than previously measured at these energies. If further confirmed, our result will be relevant for modelling the absolute response of liquid xenon detectors to particle interactions.

We propose a singlet majoron model that defines an inverse seesaw mechanism in the $\nu$ sector. The majoron $\phi$ has a mass $m_\phi\approx 0.5$ eV and a coupling to the $\tau$ lepton similar to the one to neutrinos. In the early universe it is initially in thermal equilibrium, then it decouples at $T\approx 500$ GeV and contributes with just $\Delta N_{\rm eff}=0.026$ during BBN. At $T=26$ keV (final stages of BBN) a primordial magnetic field induces resonant $\gamma \leftrightarrow \phi$ oscillations that transfer $6\%$ of the photon energy into majorons, implying $\Delta N_{\rm eff}=0.55$ and a $4\%$ increase in the baryon to photon ratio. At $T\approx m_\phi$ the majoron enters in thermal contact with the heaviest neutrino and it finally decays into $\nu \bar \nu$ pairs near recombination, setting $\Delta N_{\rm eff}=0.85$. This boost in the expansion rate at later times solves the Hubble tension, while the neutrino--majoron interactions suppress the $\nu$ free streaming and make the model consistent with large scale structure observations. Its lifetime and the fact that it decays into neutrinos instead of photons lets this axion-like majoron avoid the strong bounds that affect other axion-like particles of similar mass and coupling to photons.

We constructed a gamma-ray detector by combining two types of scintillator array detectors with an MPPC array and evaluated the spectral performance by reading out the signals from the MPPC with a low-power integrated circuit (ASIC) manufactured by IDEAS in Norway. One of the two types of scintillators is a GAGG(Ce) (Ce-doped $ \rm{Gd_3Al_2Ga_3O_{12}}$) scintillator, and the other is an LFS scintillator. The scintillator array is 2.5 cm $\times$ 2.5 cm in size and is coated with $ \rm{BaSO_4}$-based white paint for GAGG(Ce) and an enhanced specular reflector (ESR) for LFS except for the side optically coupled to the MPPC. The spectra derived from the array are affected by the MPPC photon saturations and light leakage from the adjacent pixels, and we carefully corrected for both effects in our data analysis. The energy resolution of 662 keV at 20 $^\circ$C is 6.10$\pm$0.04\% for the GAGG(Ce) scintillator array and 8.57$\pm$0.15\% for the LFS scintillator array, this is equivalent to the typical energy resolution found in the references. The energy resolution depends on the temperature: the energy resolution improves as the temperature decreases. We found that the contribution of thermal noise from the MPPCs to the energy resolution is negligible within the range of --20 to 40 $^\circ$C, and the energy resolution is mainly determined by the light yield of the crystals.

In these notes I try to introduce the reader to the topic of axions: their theoretical motivation and expected phenomenology, their role in astrophysics and as dark matter candidate, and the experimental techniques to detect them. Special emphasis is made in this last point, for which a relatively updated review of worldwide efforts and future prospects is made. The material is intended as an introduction to the topic, and it was prepared as lecture notes for Les Houches summer school 2021. Abundant references are included to direct the reader to deeper insight on the different aspects of axion physics.

We investigate the structure formation in the effective field theory of the holographic dark energy. The equation of motion for the energy contrast $\delta_m$ of the cold dark matter is the same as the one in the general relativity up to the leading order in the small scale limit $k\gg aH$, provided the equation of state is Quintessence-like. Our effective field theory breaks down while the equation of state becomes phantom-like. We propose a solution to this problem by eliminating the scalar graviton.

If there is a scalar boson field interacting dominantly with a quark or a lepton in the thermal background, its coherent oscillation can be generated through the thermal effect and becomes a good dark matter candidate in a wide range of the coupling and masses. We describe the general features of this mechanism and analyze how it works in various situations considering asymptotic limits where analytic solutions can be obtained.

We investigate an efficient mechanism for generating magnetic fields in turbulent, collisionless plasmas. By using fully kinetic, particle-in-cell simulations of an initially non-magnetized plasma, we inspect the genesis of magnetization, in a nonlinear regime. The complex motion is initiated via a Taylor-Green vortex, and the plasma locally develops strong electron temperature anisotropy, due to the strain tensor of the turbulent flow. Subsequently, in a domino effect, the anisotropy triggers a Weibel instability, localized in space. In such active wave-particle interaction regions, the magnetic field seed grows exponentially and spreads to larger scales due to the interaction with the underlying stirring motion. Such a self-feeding process might explain magneto-genesis in a variety of astrophysical plasmas, wherever turbulence is present.