Papers for Wednesday, Feb 24 2021

We derive the stellar-to-halo mass relation (SHMR), namely $f_\star\propto M_\star/M_{\rm h}$ versus $M_\star$ and $M_{\rm h}$, for early-type galaxies from their near-IR luminosities (for $M_\star$) and the position-velocity distributions of their globular cluster systems (for $M_{\rm h}$). Our individual estimates of $M_{\rm h}$ are based on fitting a dynamical model with a distribution function expressed in terms of action-angle variables and imposing a prior on $M_{\rm h}$ from the concentration-mass relation in the standard $\Lambda$CDM cosmology. We find that the SHMR for early-type galaxies declines with mass beyond a peak at $M_\star\sim 5\times 10^{10}M_\odot$ and $M_{\rm h}\sim 10^{12}M_\odot$ (near the mass of the Milky Way). This result is consistent with the standard SHMR derived by abundance matching for the general population of galaxies, and with previous, less robust derivations of the SHMR for early types. However, it contrasts sharply with the monotonically rising SHMR for late types derived from extended HI rotation curves and the same $\Lambda$CDM prior on $M_{\rm h}$ as we adopt for early types. The SHMR for massive galaxies varies more or less continuously, from rising to falling, with decreasing disc fraction and decreasing Hubble type. We also show that the different SHMRs for late and early types are consistent with the similar scaling relations between their stellar velocities and masses (Tully-Fisher and Faber-Jackson relations). Differences in the relations between the stellar and halo virial velocities account for the similarity of the scaling relations. We argue that all these empirical findings are natural consequences of a picture in which galactic discs are built mainly by smooth and gradual inflow, regulated by feedback from young stars, while galactic spheroids are built by a cooperation between merging, black-hole fuelling, and feedback from AGNs.

We probe the formation scenarios and the active galactic nuclei (AGN) occupation fraction of ultra-diffuse galaxies (UDGs) in the nearby Coma cluster by utilizing XMM-Newton observations of 779 out of 854 UDG candidates identified by Subaru survey. Their origin is probed by measuring the dark matter halo mass of the stacked sample of UDGs and the population of low-mass X-ray binaries residing in globular clusters. Our measurements suggest that the average UDG population does not have a substantial amount of hot gas or a large number of globular clusters. This supports the formation scenario, in which UDGs are puffed-up dwarf galaxies, agreeing with that obtained for 404 Coma cluster UDGs using Chandra. We also determine AGN occupation fraction of UDGs by cross-correlating the position of UDGs with the detected point sources in Coma. We detect three X-ray sources with detection significance $\sigma \geq 5$ that could be off-centre AGN within 5 arcsec from the centre of the UDG 317, UDG 432, and UDG 535. We identify an optical counterpart for the X-ray source associated with the UDG 317, suggesting that this source is more likely an off-centre AGN. Based on the current data, however, we cannot conclusively constrain whether the detected AGN is residing in the Coma cluster or not.

We present multi-band Hubble Space Telescope imaging that spans rest-frame near-ultraviolet through near-infrared wavelengths (0.3-1.1 $\mu$m) for 12 compact starburst galaxies at z=0.4-0.8. These massive galaxies (M_stellar ~ 10^11 M_Sun) are driving very fast outflows ($v_{max}$=1000-3000 km/s), and their light profiles are dominated by an extremely compact starburst component (half-light radius ~ 100 pc). Our goal is to constrain the physical mechanisms responsible for launching these fast outflows by measuring the physical conditions within the central kiloparsec. Based on our stellar population analysis, the central component typically contributes $\approx$25% of the total stellar mass and the central escape velocities $v_{esc,central}\approx900$ km/s are a factor of two smaller than the observed outflow velocities. This requires physical mechanisms that can accelerate gas to speeds significantly beyond the central escape velocities, and it makes clear that these fast outflows are capable of traveling into the circumgalactic medium, and potentially beyond. We find central stellar densities comparable to theoretical estimates of the Eddington limit, and we estimate $\Sigma_1$ surface densities within the central kpc comparable to those of compact massive galaxies at $0.5<z<3.0$. Relative to "red nuggets" and "blue nuggets" at $z\sim2$, we find significantly smaller $r_e$ values at a given stellar mass, which we attribute to the dominance of a young stellar component in our sample and the better physical resolution for rest-frame optical observations at $z\sim0.6$ versus $z\sim2$. We compare to theoretical scenarios involving major mergers and violent disc instability, and we speculate that our galaxies are progenitors of power-law ellipticals in the local universe with prominent stellar cusps.

Radio observations of tidal disruption events (TDEs) - when a star is tidally disrupted by a supermassive black hole (SMBH) - provide a unique laboratory for studying outflows in the vicinity of SMBHs and their connection to accretion onto the SMBH. Radio emission has been detected in only a handful of TDEs so far. Here, we report the detection of delayed radio flares from an optically-discovered TDE. Our prompt radio observations of the TDE ASASSN-15oi showed no radio emission until the detection of a flare six months later, followed by a second and brighter flare, years later. We find that the standard scenario, in which an outflow is launched briefly after the stellar disruption, is unable to explain the combined temporal and spectral properties of the delayed flare. We suggest that the flare is due to the delayed ejection of an outflow, perhaps following a transition in accretion states. Our discovery motivates observations of TDEs at various timescales and highlights a need for new models.

Nova eruptions, thermonuclear explosions on the surfaces of white dwarfs (WDs), are now recognized to be among the most common shock-powered transients. We present the early discovery and rapid ultraviolet (UV), optical, and infrared (IR) temporal development of AT 2019qyl, a recent nova in NGC 300. The light curve shows a rapid rise lasting $\lesssim 1$ day, reaching a peak absolute magnitude of $M_V = -9.2$ mag, and a very fast decline, fading by 2 mag over 3.5 days. A steep drop-off in the light curves after 71 days and the rapid decline timescale suggest a low-mass ejection from a massive WD with $M_{\mathrm{WD}} \gtrsim 1.2 M_{\odot}$. We present an unprecedented view of the early spectroscopic evolution of such an event. Three spectra prior to the peak reveal a complex, multi-component outflow giving rise to internal collisions and shocks in the ejecta of an He/N-class nova. We identify a coincident IR-variable counterpart in the extensive pre-eruption coverage of the transient location, and infer the presence of a symbiotic progenitor system with an O-rich asymptotic-giant-branch donor star, as well as evidence for an earlier UV-bright outburst in 2014. We suggest that AT 2019qyl is analogous to the subset of Galactic recurrent novae with red-giant companions such as RS Oph and other embedded nova systems like V407 Cyg. Our observations provide new evidence that internal outflow collisions likely play an important role in generating the shock-powered emission from such systems.

The TESS exoplanet-hunting mission detected the rising and decaying optical afterglow of GRB 191016A, a long Gamma-Ray Burst (GRB) detected by Swift-BAT but without prompt XRT or UVOT follow-up due to proximity to the moon. The afterglow has a late peak at least 1000 seconds after the BAT trigger, with a brightest-detected TESS datapoint at 2589.7 s post-trigger. The burst was not detected by Fermi-LAT, but was detected by Fermi-GBM without triggering, possibly due to the gradual nature of rising light curve. Using ground-based photometry, we estimate a photometric redshift of $z_\mathrm{phot} = 3.29\pm{0.40}$. Combined with the high-energy emission and optical peak time derived from TESS, estimates of the bulk Lorentz factor $\Gamma_\mathrm{BL}$ range from $90-133$. The burst is relatively bright, with a peak optical magnitude in ground-based follow-up of $R=15.1$ mag. Using published distributions of GRB afterglows and considering the TESS sensitivity and sampling, we estimate that TESS is likely to detect $\sim1$ GRB afterglow per year above its magnitude limit.

X-ray emission generated through solar-wind charge exchange (SWCX) is known to contaminate X-ray observation data, the amount of which is often significant or even dominant, particularly in the soft X-ray band, when the main target is comparatively weak diffuse sources, depending on the space weather during the observation. In particular, SWCX events caused by interplanetary coronal mass ejections (ICMEs) tend to be spectrally rich and to provide critical information about the metal abundance in the ICME plasma. We analyzed the SN1006 background data observed with Suzaku on 2005 September 11 shortly after an X6-class solar flare, signatures of which were separately detected together with an associated ICME. We found that the data include emission lines from a variety of highly ionized ions generated through SWCX. The relative abundances of the detected ions were found to be consistent with those in past ICME-driven SWCX events. Thus, we conclude that this event was ICME-driven. In addition, we detected a sulfur XVI line for the first time as one from the SWCX emission, the fact of which suggests that it is the most spectrally-rich SWCX event ever observed. We suggest that observations of ICME-driven SWCX events can provide a unique probe to study the population of highly-ionized ions in the plasma, which is difficult to measure in currently-available in-situ observations.

We present a multi-wavelength analysis of the galaxy cluster A1668, performed by means of new EVLA and Chandra observations and archival H$\alpha$ data. The radio images exhibit a small central source ($\sim$14 kpc at 1.4 GHz) with L$_{\text{1.4 GHz}}$ $\sim$6 $\cdot$ 10$^{23}$ W Hz$^{-1}$. The mean spectral index between 1.4 GHz and 5 GHz is $\sim$ -1, consistent with the usual indices found in BCGs. The cooling region extends for 40 kpc, with bolometric X-ray luminosity L$_{\text{cool}} = 1.9\pm 0.1 \cdot$ 10$^{43}$ erg s$^{-1}$. We detect an offset of $\sim$ 6 kpc between the cluster BCG and the X-ray peak, and another offset of $\sim$ 7.6 kpc between the H$\alpha$ and the X-ray peaks. We discuss possible causes for these offsets, which suggest that the coolest gas is not condensing directly from the lowest-entropy gas. In particular, we argue that the cool ICM was drawn out from the core by sloshing, whereas the H$\alpha$ filaments were pushed aside from the expanding radio galaxy lobes. We detect two putative X-ray cavities, spatially associated to the west radio lobe (cavity A) and to the east radio lobe (cavity B). The cavity power and age of the system are P$_{\text{cav}} \sim$ 9 $\times$10$^{42}$ erg s$^{-1}$ and t$_{\text{age}} \sim$5.2 Myr, respectively. Evaluating the position of A1668 in the cooling luminosity-cavity power parameter space, we find that the AGN energy injection is currently consistent within the scatter of the relationship, suggesting that offset cooling is likely not breaking the AGN feedback cycle.

We report results from a FUSE survey of interstellar molecular hydrogen (H2) in the Galactic disk toward 139 O-type and early B-type stars at Galactic latitudes $|b| < 10^{\circ}$, with updated photometric and parallax distances. The H2 absorption is measured using the far-ultraviolet Lyman and Werner bands, including strong R(0), R(1), and P(1) lines from rotational levels $J = 0$ and $J = 1$ and excited states up to $J = 5$ (sometimes $J = 6$ and 7). For each sight line, we report column densities $N_{H2}$, $N_{HI}$, $N(J)$, $N_H = N_{HI} + 2N_{H2}$, and molecular fraction, $f_{H2} = 2N_{H2}/N_H$. Our survey extends the 1977 Copernicus H2 survey up to $N_H \sim 5\times10^{21}$ cm$^{-2}$. The lowest rotational states have mean excitation temperatures and rms dispersions, $T_{01} = 88\pm 20$ K and $T_{02} = 77\pm18$ K, suggesting that J = 0,1,2 are coupled to the gas kinetic temperature. Populations of higher-J states exhibit mean excitation temperatures, $T_{24} = 237\pm91$ K and $T_{35} = 304\pm108$ K, produced primarily by UV radiative pumping. Correlations of $f_{H2}$ with E(B-V) and N_H show a transition to $f_{H2} \geq 0.1$ at $N_ H \geq 10^{21}$ cm$^{-2}$ and $E(B-V) > 0.2$, interpreted with an analytic model of H2 formation-dissociation equilibrium and attenuation of the far-UV radiation field by self-shielding and dust opacity. Results of this disk survey are compared to previous FUSE studies of H2 in translucent clouds, at high Galactic latitudes, and in the Magellanic Clouds. Using updated distances to the target stars, we find average sight-line values $\langle f_{H2} \rangle \geq 0.20$ and $\langle N_H/E(B-V) \rangle = (6.07\pm1.01)\times10^{21}$ cm$^{-2}$ mag$^{-1}$.

Masses of classical Cepheids of 3 to 11 M$\odot$ are predicted by theory but those measured, clump between 3.6 and 5 M$\odot$. As a result, their mass-luminosity relation is poorly constrained, impeding our understanding of basic stellar physics and the Leavitt Law. All Cepheid masses come from the analysis of 11 binary systems, including only 5 double-lined and well-suited for accurate dynamical mass determination. We present a project to analyze a new, numerous group of Cepheids in double-lined binary (SB2) systems to provide mass determinations in a wide mass interval and study their evolution. We analyze a sample of 41 candidate binary LMC Cepheids spread along the P-L relation, that are likely accompanied by luminous red giants, and present indirect and direct indicators of their binarity. In a spectroscopic study of a subsample of 18 brightest candidates, for 16 we detected lines of two components in the spectra, already quadrupling the number of Cepheids in SB2 systems. Observations of the whole sample may thus lead to quadrupling all the Cepheid mass estimates available now. For the majority of our candidates, erratic intrinsic period changes dominate over the light travel-time effect due to binarity. However, the latter may explain the periodic phase modulation for 4 Cepheids. Our project paves the way for future accurate dynamical mass determinations of Cepheids in the LMC, Milky Way, and other galaxies, which will potentially increase the number of known Cepheid masses even 10-fold, hugely improving our knowledge about these important stars.

The Zwicky Transient Facility (ZTF) has been observing the entire northern sky since the start of 2018 down to a magnitude of 20.5 ($5 \sigma$ for 30s exposure) in $g$, $r$, and $i$ filters. Over the course of two years, ZTF has obtained light curves of more than a billion sources, each with 50-1000 epochs per light curve in $g$ and $r$, and fewer in $i$. To be able to use the information contained in the light curves of variable sources for new scientific discoveries, an efficient and flexible framework is needed to classify them. In this paper, we introduce the methods and infrastructure which will be used to classify all ZTF light curves. Our approach aims to be flexible and modular and allows the use of a dynamical classification scheme and labels, continuously evolving training sets, and the use of different machine learning classifier types and architectures. With this setup, we are able to continuously update and improve the classification of ZTF light curves as new data becomes available, training samples are updated, and new classes need to be incorporated.

We report new branching fraction measurements for 199 UV and optical transitions of Hf II. These transitions range in wavelength (wavenumber) from 2068- 6584 A (48322-15183 cm-1) and originate in 17 odd-parity upper levels ranging in energy from 38578-53227 cm-1. The branching fractions are combined with radiative lifetimes reported in an earlier study to produce a set of transition probabilities and log(gf) values with accuracy ranging from 5-25%. Comparison is made to transition probabilities from the literature where such data exist. We use these new transition probabilities to derive improved Hf abundances in two metal-poor stars. HD 196944 is enhanced in s-process elements, and we derive log epsilon (Hf) = -0.72 +/- 0.03 (sigma = 0.09) from 12 Hf II lines. HD 222925 is enhanced in r-process elements, and we derive log epsilon (Hf) = 0.32 +/- 0.03 (sigma = 0.11) from 20 Hf II lines. These measurements greatly expand the number of potentially useful Hf II lines for analysis in UV and optical spectra.

Using a suite of numerical calculations, we consider the long-term evolution of circumbinary debris from the Pluto-Charon giant impact. Initially, these solids have large eccentricity and pericenters near Charon's orbit. On time scales of 100-1000 yr, dynamical interactions with Pluto and Charon lead to the ejection of most solids from the system. As the dynamics moves particles away from the barycenter, collisional damping reduces the orbital eccentricity of many particles. These solids populate a circumbinary disk in the Pluto-Charon orbital plane; a large fraction of this material lies within a `satellite zone' that encompasses the orbits of Styx, Nix, Kerberos, and Hydra. Compared to the narrow rings generated from the debris of a collision between a trans-Neptunian object (TNO) and Charon, disks produced after the giant impact are much more extended and may be a less promising option for producing small circumbinary satellites.

Large-scale coherent magnetic fields in the intergalactic medium are presumed to play a key role in the formation and evolution of the cosmic web, and in large scale feedback mechanisms. However, they are theorized to be extremely weak, in the nano-Gauss regime. To search for a statistical signature of these weak magnetic fields we perform a cross-correlation between the Faraday rotation measures of 1742 radio galaxies at $z > 0.5$ and large-scale structure at $0.1 < z< 0.5$, as traced by 18 million optical and infrared foreground galaxies. No significant correlation signal was detected within the uncertainty limits. We are able to determine model-dependent $3 \sigma$ upper limits on the parallel component of the mean magnetic field strength of filaments in the intergalactic medium of $\sim 30 \ \mathrm{nG}$ for coherence scales between $1$ and $2.5 \ \mathrm{Mpc}$, corresponding to a mean upper bound RM enhancement of $\sim 3.8 \ \mathrm{rad/m^{2}}$ due to filaments along all probed sight-lines. These upper bounds are consistent with upper bounds found previously using other techniques. Our method can be used to further constrain intergalactic magnetic fields with upcoming future radio polarization surveys.

The evolution of galaxies depends on their environments. In this work, active galactic nucleus (AGN) activity in different environments has been studied. The fractions of radio and optical AGN in four different environments have been compared using samples of void, isolated, group member, and the brightest group galaxies (BGGs). Galaxies in voids show significantly lower stellar ages, concentrations, colours and surface mass densities, and they experience more one-on-one interactions compared to the isolated galaxies and galaxies in groups. In order to study pure environmental effects, the biases caused by the stellar mass and galaxy type quantified by 4000$\AA$ break strength have been removed. While the results confirm no dependence of the optical AGN activity on environment in blue galaxies and with lower significance in green galaxies, a higher fraction of optical AGN has been observed for the massive red galaxies in voids compared to the galaxies in dense environments. This may be related to the higher amount of one-on-one interaction observed in the void galaxies, or it may reflect more fundamental differences in the host galaxies or environments of the voids. The radio-mode AGN activity increases in dense environment for red galaxies. No changes in the radio-loud AGN fraction have been observed for the blue and green galaxies. This shows that the effect of environment on AGN activity is not significant in the presence of cold gas in galaxies. We also discuss whether the efficiency of gas accretion depends on the properties of the host galaxy.

Palomar 5 is one of the sparsest star clusters in the Galactic halo and is best-known for its spectacular tidal tails, spanning over 20 degrees across the sky. With N-body simulations we show that both distinguishing features can result from a stellar-mass black hole population, comprising ~20 of the present-day cluster mass. In this scenario, Palomar 5 formed with a `normal' black hole mass fraction of a few per cent, but stars were lost at a higher rate than black holes, such that the black hole fraction gradually increased. This inflated the cluster, enhancing tidal stripping and tail formation. A gigayear from now, the cluster will dissolve as a 100% black hole cluster. Initially denser clusters end up with lower black hole fractions, smaller sizes, and no observable tails at present day. Black hole-dominated, extended star clusters are therefore the likely progenitors of the recently discovered thin stellar streams in the Galactic halo.

Two dwarf galaxies: WOC2017-07 and PGC 704814 located in the vicinity of the nearby luminous spiral galaxy NGC 253 were observed with the Advanced Camera for Surveys on the Hubble Space Telescope. Their distances of 3.62$\pm$0.18 Mpc and 3.66$\pm$0.18 Mpc were derived using the tip of the red giant branch method. These distances are consistent with the dwarf galaxies being members of the NGC 253 group. Based on the radial velocities and projected separations of seven assumed dwarf companions, we estimated the total mass of NGC 253 to be $(8.1\pm2.6) 10^{11} M_{\odot}$, giving a total-mass-to-$K$-luminosity ratio $M_{\rm orb}/L_K = (8.5\pm2.7) M_{\odot}/L_{\odot}$. A notable property of NGC 253 is its declined rotation curve. NGC 253 joins four other luminous spiral galaxies in the Local Volume with declined rotation curves (NGC 2683, NGC 2903, NGC 3521 and NGC 5055) that together have the low average total-mass-to-luminosity ratio, $M_{\rm orb}/L_K = (5.5\pm1.1) M_{\odot}/L_{\odot}$. This value is only $\sim$1/5 of the corresponding ratio for the Milky Way and M 31.

The interest in the problem of small asteroids observed shortly before a deep close approach or an impact with the Earth has grown a lot in recent years. Since the observational dataset of such objects is very limited, they deserve dedicated orbit determination and hazard assessment methods. The currently available systems are based on the systematic ranging, a technique providing a 2-dimensional manifold of orbits compatible with the observations, the so-called Manifold Of Variations. In this paper we first review the Manifold Of Variations method, to then show how this set of virtual asteroids can be used to predict the impact location of short-term impactors, and compare the results with those of already existent methods.

We present a 5A-100um Spectral Energy Distribution (SED) of the ultracool dwarf star TRAPPIST-1, obtained as part of the Mega-MUSCLES Treasury Survey. The SED combines ultraviolet and blue-optical spectroscopy obtained with the Hubble Space Telescope, X-ray spectroscopy obtained with XMM-Newton, and models of the stellar photosphere, chromosphere, transition region and corona. A new Differential Emission Measure model of the unobserved extreme-ultraviolet spectrum is provided, improving on the Lyman alpha to EUV relations often used to estimate the 100-911A flux from low-mass stars. We describe the observations and models used, as well as the recipe for combining them into an SED. We also provide a semi-empirical, noise-free model of the stellar ultraviolet spectrum based on our observations for use in atmospheric modelling of the TRAPPIST-1 planets.

We present the analysis of the microlensing event OGLE-2018-BLG-1428, which has a short-duration ($\sim 1$ day) caustic-crossing anomaly. The event was caused by a planetary lens system with planet/host mass ratio $q=1.7\times10^{-3}$. Thanks to the detection of the caustic-crossing anomaly, the finite source effect was well measured, but the microlens parallax was not constrained due to the relatively short timescale ($t_{\rm E}=24$ days). From a Bayesian analysis, we find that the host star is a dwarf star $M_{\rm host}=0.43^{+0.33}_{-0.22} \ M_{\odot}$ at a distance $D_{\rm L}=6.22^{+1.03}_{-1.51}\ {\rm kpc}$ and the planet is a Jovian-mass planet $M_{\rm p}=0.77^{+0.77}_{-0.53} \ M_{\rm J}$ with a projected separation $a_{\perp}=3.30^{+0.59}_{-0.83}\ {\rm au}$. The planet orbits beyond the snow line of the host star. Considering the relative lens-source proper motion of $\mu_{\rm rel} = 5.58 \pm 0.38\ \rm mas\ yr^{-1}$, the lens can be resolved by adaptive optics with a 30m telescope in the future.

We report new dust polarization results of a nearly edge-on disk in the HH 212 protostellar system, obtained with ALMA at ~ 0.035" (14 au) resolution in continuum at lambda ~ 878 um. Dust polarization is detected within ~ 44 au of the central source, where a rotationally supported disk has formed. The polarized emission forms V-shaped structures opening to the east and probably west arising from the disk surfaces and arm structures further away in the east and west that could be due to potential spiral arms excited in the outer disk. The polarization orientations are mainly parallel to the minor axis of the disk, with some in the western part tilting slightly away from the minor axis to form a concave shape with respect to the center. This tilt of polarization orientations is expected from dust self-scattering, e.g., by 50-75 um grains in a young disk. The polarized intensity and polarization degree both peak near the central source with a small dip at the central source and decrease towards the edges. These decreases of polarized intensity and polarization degree are expected from dichroic extinction by grains aligned by poloidal fields, but may also be consistent with dust self-scattering if the grain size decreases toward the edges. It is possible that both mechanisms are needed to produce the observed dust polarization, suggesting the presence of both grain growth and poloidal fields in the disk.

Direct exoplanet spectroscopy aims to measure the spectrum of an exoplanet while simultaneously minimizing the light collected from its host star. Isolating the planet light from the starlight improves the signal-to-noise ratio (S/N) per spectral channel when noise due to the star dominates, which may enable new studies of the exoplanet atmosphere with unprecedented detail at high spectral resolution (>30,000). However, the optimal instrument design depends on the flux level from the planet and star compared to the noise due to other sources, such as detector noise and thermal background. Here we present the design, fabrication, and laboratory demonstration of specially-designed optics to improve the S/N in two potential regimes in direct exoplanet spectroscopy with adaptive optics instruments. The first is a pair of beam-shaping lenses that increase the planet signal by improving the coupling efficiency into a single-mode fiber at the known position of the planet. The second is a grayscale apodizer that reduces the diffracted starlight for planets at small angular separations from their host star. The former especially increases S/N when dominated by detector noise or thermal background, while the latter helps reduce stellar noise. We show good agreement between the theoretical and experimental point spread functions in each case and predict the exposure time reduction ($\sim 33\%$) that each set of optics provides in simulated observations of 51 Eridani b using the Keck Planet Imager and Characterizer instrument at W.M. Keck Observatory.

The hot component of the circum-galactic medium (CGM) around star forming galaxies is detected as diffuse X-ray emission. The X-ray spectra from the CGM depend on the temperature and metallicity of the emitting plasma, providing important information about the feeding and feedback of the galaxy. The observed spectra are commonly fitted using simple 1-Temperature (1-T) or 2-T models. However, the actual temperature distribution of the gas can be complex because of the interaction between galactic outflows and halo gas. Here we demonstrate this by analysing 3-D hydrodynamical simulations of the CGM with a realistic outflow model. We investigate the physical properties of the simulated hot CGM, which shows a broad distribution in density, temperature, and metallicity. By constructing and fitting the simulated spectra, we show that, while the 1-T and 2-T models are able to fit the synthesized spectra reasonably well, the inferred temperature(s) bear little physical meaning. Instead, we propose a log-normal distribution as a more physical model. The log-normal model better fits the simulated spectra while reproducing the gas temperature distribution. We also show that when the star formation rate is high, the spectra inside the bi-conical outflows are distinct from that outside, as outflows are generally hotter and more metal-enriched. Finally, we produce mock spectra for future missions with the eV-level spectral resolution, such as Athena, Lynx, and HUBS.

We review the effect that the choice of a uniform or logarithmic prior has on the Bayesian evidence and hence on Bayesian model comparisons when data provide only a one-sided bound on a parameter. We investigate two particular examples: the tensor-to-scalar ratio $r$ of primordial perturbations and the mass of individual neutrinos $m_\nu$, using the cosmic microwave background temperature and polarisation data from Planck 2018 and the NuFIT 5.0 data from neutrino oscillation experiments. We argue that the Kullback-Leibler divergence, also called the relative entropy, mathematically quantifies the Occam penalty. We further show how the Bayesian evidence stays invariant upon changing the lower prior bound of an upper constrained parameter. While a uniform prior on the tensor-to-scalar ratio disfavours the $r$-extension compared to the base LCDM model with odds of about 1:20, switching to a logarithmic prior renders both models essentially equally likely. LCDM with a single massive neutrino is favoured over an extension with variable neutrino masses with odds of 20:1 in case of a uniform prior on the lightest neutrino mass, which decreases to roughly 2:1 for a logarithmic prior. For both prior options we get only a very slight preference for the normal over the inverted neutrino hierarchy with Bayesian odds of about 3:2 at most.

We analyse the metallicity histories of ~4,500 galaxies from the GAMA survey at z<0.06 modelled by the SED-fitting code ProSpect using an evolving metallicity implementation. These metallicity histories, in combination with the associated star formation histories, allow us to analyse the inferred gas-phase mass--metallicity relation. Furthermore, we extract the mass--metallicity relation at a sequence of epochs in cosmic history, to track the evolving mass--metallicity relation with time. Through comparison with observations of gas-phase metallicity over a large range of redshifts, we show that, remarkably, our forensic SED analysis has produced an evolving mass--metallicity relationship that is consistent with observations at all epochs. We additionally analyse the three dimensional mass--metallicity--SFR space, showing that galaxies occupy a clearly defined plane. This plane is shown to be subtly evolving, displaying an increased tilt with time caused by general enrichment, and also the slowing down of star formation with cosmic time. This evolution is most apparent at lookback times greater than 7 Gyr. The trends in metallicity recovered in this work highlight that the evolving metallicity implementation used within the SED fitting code ProSpect produces reasonable metallicity results over the history of a galaxy. This is expected to provide a significant improvement to the accuracy of the SED fitting outputs.

We investigate what the orbits of globular clusters (GCs) in the Fornax dwarf spheroidal (dSph) galaxy can teach us about dark matter (DM). This problem was recently studied for ultralight dark matter (ULDM). We consider two additional models: (i) fermionic degenerate dark matter (DDM), where Pauli blocking should be taken into account in the dynamical friction computation; and (ii) self-interacting dark matter (SIDM). We give a simple and direct Fokker-Planck derivation of dynamical friction, new in the case of DDM and reproducing previous results in the literature for ULDM and cold DM. ULDM, DDM and SIDM were considered in the past as leading to cores in dSphs, a feature that acts to suppress dynamical friction and prolong GC orbits. For DDM we derive a version of the cosmological free streaming limit that is independent of the DM production mechanism, finding that DDM cannot produce an appreciable core in Fornax without violating Ly-$\alpha$ limits. If the Ly-$\alpha$ limit is discounted for some reason, then stellar kinematics data does allow a DDM core which could prolong GC orbits. For SIDM we find that significant prolongation of GC orbits could be obtained for values of the self-interaction cross section considered in previous works. In addition to reassessing the inspiral time using updated observational data, we give a new perspective on the so-called GC timing problem, demonstrating that for a cuspy cold DM profile dynamical friction predicts a $z=0$ radial distribution for the innermost GCs that is independent of initial conditions. The observed orbits of Fornax GCs are consistent with this expectation with a mild apparent fine-tuning at the level of $\sim25\%$.

Fireballs are infrequently recorded by seismic sensors on the ground. If recorded, they are usually reported as one-off events. This study is the first seismic bulk analysis of the largest single fireball data set, observed by the Desert Fireball Network (DFN) in Australia in the period 2014-2019. The DFN typically observes fireballs from cm-m scale impactors. We identified 25 fireballs in seismic time series data recorded by the Australian National Seismograph Network (ANSN). This corresponds to 1.8% of surveyed fireballs, at the kinetic energy range of 10$^6$ to 10$^{10}$ J. The peaks observed in the seismic time series data were consistent with calculated arrival times of the direct airwave or ground-coupled Rayleigh wave caused by shock waves by the fireball in the atmosphere (either due to fragmentation or the passage of the Mach cone). Our work suggests that identification of fireball events in the seismic time series data depends both on physical properties of a fireball (such as fireball energy and entry angle in the atmosphere) and the sensitivity of a seismic instrument. This work suggests that fireballs are likely detectable within 200 km direct air distance between a fireball and seismic station, for sensors used in the ANSN. If each DFN observatory had been accompanied by a seismic sensor of similar sensitivity, 50% of surveyed fireballs could have been detected. These statistics justify the future consideration of expanding the DFN camera network into the seismic domain.

Fast radio bursts (FRBs) are astrophysical transients of still debated origin. So far several hundred events have been detected, mostly at extragalactic distances, and this number is expected to grow significantly over the next years. The radio signals from the burst experience dispersion as they travel through the free electrons along the line-of-sight characterised by the dispersion measure (DM) of the radio pulse. In addition, each photon also experiences a gravitational Shapiro time delay while travelling through the potentials generated by the large-scale structure. If the equivalence principle (EP) holds, the Shapiro delay is the same for photons of all frequencies. In case the EP is broken, one would expect an additional dispersion to occur which could be either positive or negative for individual sources. Here we suggest to use angular statistics of the DM fluctuations to put constraints on the EP parametrized by the post-Newtonian parameter $\gamma$. Previous studies suffer from the problem that the gravitational potential responsible for the delay diverges in a cosmological setting, which our approach avoids. We carry out a forecast for a population of FRBs observable within the next years and show that any significant detection of the DM angular power spectrum will place constraints on the EP that are by a few orders of magnitude more stringent than current limits.

High-quality astronomical images delivered by modern ground-based and space observatories demand adequate, reliable software for their analysis and accurate extraction of sources, filaments, and other structures, containing massive amounts of detailed information about the complex physical processes in space. The multi-wavelength observations with highly variable angular resolutions across wavebands require extraction tools that preserve and use the invaluable high-resolution information. This paper presents getsf, a new method for extracting sources and filaments in astronomical images using separation of their structural components, designed to handle multi-wavelength sets of images and very complex filamentary backgrounds. The method spatially decomposes the original images and separates the structural components of sources and filaments from each other and from their backgrounds, flattening their resulting images. It spatially decomposes the flattened components, combines them over wavelengths, detects the positions of sources and skeletons of filaments, and measures the detected sources and filaments. This paper presents a realistic multi-wavelength set of simulated benchmark images that can serve as the standard benchmark problem to evaluate qualities of source and filament extraction methods. This paper describes hires, an improved algorithm for the derivation of high-resolution surface densities from the multi-wavelength far-infrared Herschel images. The algorithm allows creation of the surface densities with angular resolutions reaching 5.6 arcsec, when using the 70 micron image. Both getsf and hires are illustrated by their applications to a variety of images, from the X-ray domain to the millimeter wavelengths.

In recent years, there have been significant advances in multi-messenger astronomy due to the discovery of the first, and so far only confirmed, gravitational wave event with a simultaneous electromagnetic (EM) counterpart, as well as improvements in numerical simulations, gravitational wave (GW) detectors, and transient astronomy. This has led to the exciting possibility of performing joint analyses of the GW and EM data, providing additional constraints on fundamental properties of the binary progenitor and merger remnant. Here, we present a new Bayesian framework that allows inference of these properties, while taking into account the systematic modeling uncertainties that arise when mapping from GW binary progenitor properties to photometric light curves. We extend the relative binning method presented in Zackay et al. (2018) to include extrinsic GW parameters for fast analysis of the GW signal. The focus of our EM framework is on light curves arising from r-process nucleosynthesis in the ejected material during and after merger, the so called kilonova, and particularly on black hole - neutron star systems. As a case study, we examine the recent detection of GW190425, where the primary object is consistent with being either a black hole (BH) or a neutron star (NS). We show quantitatively how improved mapping between binary progenitor and outflow properties, and/or an increase in EM data quantity and quality are required in order to break degeneracies in the fundamental source parameters.

Synchrotron radio emission from non-relativistic jets powered by massive protostars has been reported, indicating the presence of relativistic electrons and magnetic fields of strength ~0.3-5 mG. We study diffusive shock acceleration and magnetic field amplification in protostellar jets with speeds between 300 and 1500 km/s. We show that the magnetic field in the synchrotron emitter can be amplified by the non-resonant hybrid (Bell) instability excited by the cosmic-ray streaming. By combining the synchrotron data with basic theory of Bell instability we estimate the magnetic field in the synchrotron emitter and the maximum energy of protons. Protons can achieve maximum energies in the range 0.04-0.65 TeV and emit gamma rays in their interaction with matter fields. We predict detectable levels of gamma rays in IRAS 16547-5247 and IRAS 16848-4603. The gamma ray flux can be significantly enhanced by the gas mixing due to Rayleigh-Taylor instability. The detection of this radiation by the Fermi satellite in the GeV domain and the forthcoming Cherenkov Telescope Array at higher energies may open a new window to study the formation of massive stars, as well as diffusive acceleration and magnetic field amplification in shocks with velocities of about 1000 km/s.

Gamma-ray emission in active galaxies is likely produced within the inner jet, or in the close vicinity of the supermassive black hole (SMBH) at sub-parsec distances. Gamma rays have to pass through the surrounding massive stellar cluster which luminous stars can accidentally appear close to the observer's line of sight. In such a case, soft radiation of massive stars can create enough target for transient absorption of the gamma rays in multi-GeV to TeV energy range. We consider the effect of such stellar encounters on the gamma-ray spectrum produced within the massive stellar cluster surrounding a central SMBH. We predict characteristic, time-dependent effects on the gamma-ray spectra due to the encounter with the single luminous star and also stellar binary system. We conclude that during the encounter, the gamma-ray spectrum of an active galaxy should steepen at tens of GeV and harden in the range of hundreds of GeV. As an example, we consider such effects on the spectra observed from a typical blazar, 1ES\ 1959+650 (in an active state) and also in the case of a radio galaxy M87 (in a low state). It is shown that observation of such transient characteristic features in the gamma-ray spectra, observed from blazars and radio galaxies, lays within the sensitivity of the future Cherenkov Telescope Array.

We describe the application of Semantic Segmentation by using the Self Organizing Map technique to an high spatial and spectral resolution dataset acquired along the H$\alpha$ line at 656.28 nm by the Interferometric Bi-dimensional Spectrometer installed at the focus plane of the Dunn Solar Telescope. This machine learning approach allowed us to identify several features corresponding to the main structures of the solar photosphere and chromosphere. The obtained results show the capability and flexibility of this method to identifying and analyzing the fine structures which characterize the solar activity in the low atmosphere. This is a first successful application of the SOM technique to astrophysical data sets.

Matched filtering is a traditional method used to search a data stream for signals. If the source (and hence its $n$ parameters) are unknown, many filters must be employed. These form a grid in the $n$-dimensional parameter space, known as a template bank. It is often convenient to construct these grids as a lattice. Here, we examine some of the properties of these template banks for $\mathbb{Z}^n$ and $A_n^*$ lattices. In particular, we focus on the distribution of the mismatch function, both in the traditional quadratic approximation and in the recently-proposed spherical approximation. The fraction of signals which are lost is determined by the even moments of this distribution, which we calculate. Many of these quantities we examine have a simple and well-defined $n\to\infty$ limit, which often gives an accurate estimate even for small $n$. Our main conclusions are the following: (i) a fairly effective template-based search can be constructed at mismatch values that are shockingly high in the quadratic approximation; (ii) the minor advantage offered by an $A_n^*$ template bank (compared to $\mathbb{Z}^n$) at small template separation becomes even less significant at large mismatch. So there is little motivation for using template banks based on the $A_n^*$ lattice.

On 2019 October 25, the Fermi-Large Area Telescope observed the first gamma-ray flare from the radio-loud narrow-line Seyfert 1 (NLSy 1) galaxy PKS 2004$-$447 ($z=0.24$). We report on follow-up observations in the radio, optical-UV, and X-ray bands that were performed by ATCA, the Neil Gehrels Swift observatory, XMM-Newton, and NuSTAR, respectively, and our multi-wavelength analysis. We study the variability across all energy bands and additionally produce $\gamma$-ray light curves with different time binnings to study the variability on short timescales during the flare. We examine the X-ray spectrum from 0.5$-$50 keV by describing the spectral shape with an absorbed power law. We analyse multi-wavelength datasets before, during, and after the flare and compare these with a low activity state of the source by modelling the respective SEDs with a one-zone synchrotron inverse Compton radiative model. Finally, we compare our results to gamma-ray flares previously observed from other $\gamma$-loud NLSy 1 galaxies. At gamma-ray energies (0.1$-$300 GeV) the flare reached a total maximum flux of $(2.7\pm0.6)\times10^{-6}$~ph~cm$^{-2}$~s$^{-1}$ in 3-hour binning. With a photon index of $\Gamma_{0.1-300\mathrm{GeV}}=2.42\pm0.09$ during the flare, this corresponds to an isotropic gamma-ray luminosity of $(2.9\pm0.8)\times10^{47}\,\mathrm{erg}\,\mathrm{s}^{-1}$. The $\gamma$-ray, X-ray, and optical-UV light curves covering the end of September to the middle of November show significant variability, and we find indications for flux-doubling times of $\sim 2.2$~hours at $\gamma$-ray energies. During the flare, the SED exhibits large Compton dominance. While the increase in the optical-UV range can be explained by enhanced synchrotron emission, the elevated $\gamma$-ray flux can be accounted for by an increase in the bulk Lorentz factor of the jet, similarly observed for flaring gamma-ray blazars.

We study the structure of the accretion flow in the hard state of the black-hole X-ray binary MAXI J1820+070 with NICER data. We use the power spectra to reconstruct the energy spectra of the variability components peaking at four different time scales. We find that the spectrum changes as a function of time scales. The two variability components peaking at longer time scales have similar shape, while the two peaking at the shorter time scales differ significantly. In particular, the one corresponding to the shortest time scales has the hardest spectrum. Both the variability spectra and the time-averaged spectrum are well-modelled by a disc blackbody and thermal Comptonization, but the presence of (at least) two Comptonization zones with different temperatures and optical depths is required. The disc blackbody component is highly variable, but only in the variability components peaking at the longest time scales ($\geq1$ s). The seed photons for the spectrally harder zone come predominantly from the softer Comptonization zone. Our results require the accretion flow in this source to be structured, and cannot be described by a single Comptonization region upscattering disc blackbody photons, and reflection from the disc.

One of the main objectives of the Transiting Exoplanet Survey Satellite (TESS) mission is the discovery of small rocky planets around bright, nearby stars. Here, we report the confirmation and characterization of the transiting super-Earth planet orbiting LHS~1478 (TOI-1640). The star is an inactive red dwarf ($J=9.6$\,mag and spectral type M3.5\,V) with mass and radius estimates of $0.20\pm0.01$\,$M_{\odot}$ and $0.25\pm0.01$\,$R_{\odot}$, respectively, and an effective temperature of $3381\pm54$\,K. It was observed by \tess in four sectors. These data revealed a transit-like feature with a period of 1.949 days. We combined the TESS data with three ground-based transit measurements, 57 radial-velocity (RV) measurements from CARMENES, and 13 RV measurements from IRD to determine that the signal is produced by a planet with a mass of $2.33^{+0.20}_{-0.20}$\,$M_{\oplus}$ and radius $1.24^{+0.05}_{-0.05}$\,$R_{\oplus}$. The resulting bulk density of this planet is 6.66\,g\,cm$^{-3}$, consistent with a rocky planet with a Fe- and MgSiO$_3$-dominated composition. Although the planet would be too hot to sustain liquid water on its surface (its equilibrium temperature is of about $\sim$595\,K), spectroscopic metrics based on the capabilities of the forthcoming James Webb Space Telescope, and the fact that the host star is rather inactive indicate that this is one of the most favorable known rocky exoplanets for atmospheric characterization.

High resolution spectra of quasar absorption systems provide the best constraints on temporal or spatial changes of fundamental constants in the early universe. An important systematic that has never before been quantified concerns model non-uniqueness; the absorption component structure is generally complicated, comprising many blended lines. This characteristic means any given system can be fitted equally well by many slightly different models, each having a different value of \alpha, the fine structure constant. We use AI Monte Carlo modelling to quantify non-uniqueness and describe how it accounts for previously unexplained scatter seen in the majority of published measurements. Extensive supercomputer calculations are reported, revealing new systematic effects that guide future analyses: (i) systematic errors significantly increase if line broadening models are turbulent but are minimised if gas temperature is included as a free parameter; modelling quasar absorption systems using turbulent broadening should be avoided and compound broadening is preferable. (ii) The general overfitting tendency of AICc dramatically increases non-uniqueness and hence the overall error budget on estimates of \alpha variations. The newly introduced Spectral Information Criterion (SpIC) statistic is more suitable and substantially decreases non-uniqueness compared to AICc-based models.

Since the formation of the terrestrial planets, atmospheric loss has irreversibly altered their atmospheres, leading to remarkably different surface environments - Earth has remained habitable while Venus and Mars are apparently desolate. The concept of habitability centres around the availability of liquid water which depends greatly on the composition of the atmosphere. While the history of molecular oxygen O$_2$ in Earth's atmosphere is debated, geological evidence supports at least two major episodes of increasing oxygenation: the Great Oxidation Event and the Neoproterozoic Oxidation Event. Both are thought to have been pivotal for the development and evolution of life. We demonstrate through three-dimensional simulations that atmospheric O$_2$ concentrations on Earth directly control the evolution and distribution of greenhouse gases (such as O$_3$, H$_2$O, CH$_4$ and CO$_2$) and the atmospheric temperature structure. In particular, at $\leq 1$% the present atmospheric level (PAL) of O$_2$, the stratosphere collapses. Our simulations show that a biologically ineffective ozone shield, lower than previously thought, existed during the Proterozoic, with a need for a Phanerozoic ozone shield to allow the emergence of surface life. We find that O$_2$ acts as a valve for the loss rate of atmospheric hydrogen through the exosphere. Estimated levels of hydrogen escape for the Proterozoic eon are all lower than present day, enabling us to establish Earth's water loss timeline. Furthermore, we demonstrate how O$_2$ on terrestrial exoplanets determines their theoretical transmission spectra, challenging signal-to-nose ratio assumptions contributing to the design of next generation telescopes that will facilitate the characterisation of Earth-like worlds.

We use sub-arcsecond resolution ($\sim$0.4$''$) observations with NOEMA at 1.37 mm to study the dust emission and molecular gas of 18 high-mass star-forming regions. We combine the derived physical and chemical properties of individual cores in these regions to estimate their ages. The temperature structure of these regions are determined by fitting H2CO and CH3CN line emission. The density profiles are inferred from the 1.37 mm continuum visibilities. The column densities of 11 different species are determined by fitting the emission lines with XCLASS. Within the 18 observed regions, we identify 22 individual cores with associated 1.37 mm continuum emission and with a radially decreasing temperature profile. We find an average temperature power-law index of q = 0.4$\pm$0.1 and an average density power-law index of p = 2.0$\pm$0.2 on scales on the order of several 1 000 au. Comparing these results with values of p derived in the literature suggest that the density profiles remain unchanged from clump to core scales. The column densities relative to N(C18O) between pairs of dense gas tracers show tight correlations. We apply the physical-chemical model MUSCLE to the derived column densities of each core and find a mean chemical age of $\sim$60 000 yrs and an age spread of 20 000-100 000 yrs. With this paper we release all data products of the CORE project available at https://www.mpia.de/core. The CORE sample reveals well constrained density and temperature power-law distributions. Furthermore, we characterize a large variety in molecular richness that can be explained by an age spread confirmed by our physical-chemical modeling. The hot molecular cores show the most emission lines, but we also find evolved cores at an evolutionary stage, in which most molecules are destroyed and thus the spectra appear line-poor again.

Ultra-hot Jupiters are the hottest exoplanets discovered so far. Observations begin to provide insight into the composition of their extended atmospheres and their chemical day/night asymmetries. Both are strongly affected by cloud formation. We explore trends in cloud properties for a sample of five giant gas planets: WASP-43b, WASP-18b, HAT-P-7b, WASP-103b, and WASP-121b. This provides a reference frame for cloud properties for the JWST targets WASP-43b and WASP-121b. We further explore chemically inert tracers to observe geometrical asymmetries, and if the location of inner boundary of a 3D GCM matters for the clouds that form. The large day/night temperature differences of ultra-hot Jupiters cause large chemical asymmetries: cloud-free days but cloudy nights, atomic vs. molecular gases and respectively different mean molecular weights, deep thermal ionospheres vs. low-ionised atmospheres, undepleted vs enhanced C/O. WASP-18b, as the heaviest planet in the sample, has the lowest global C/O. The global climate may be considered as similar amongst ultra-hot Jupiters, but different to that of hot gas giants. The local weather, however, is individual for each planet since the local thermodynamic conditions, and hence the local cloud and gas properties, differ. The morning and the evening terminator of ultra-hot Jupiters will carry signatures of their strong chemical asymmetry such that ingress/egress asymmetries can be expected. An increased C/O ratio is a clear sign of cloud formation, making cloud modelling a necessity when utilizing C/O (or other mineral ratios) as tracer for planet formation. The changing geometrical extension of the atmosphere from the day to the nightside may be probed through chemically inert species like helium. Ultra-hot Jupiters are likely to develop deep atmospheric ionospheres which may impact the atmosphere dynamics through MHD processes.

Millisecond spinning, low magnetic field neutron stars are believed to attain their fast rotation in a 0.1-1 Gyr-long phase during which they accrete matter endowed with angular momentum from a low-mass companion star. Despite extensive searches, coherent periodicities originating from accreting neutron star magnetospheres have been detected only at X-ray energies and in ~10% of the presently known systems. Here we report the detection of optical and ultraviolet coherent pulsations at the X-ray period of the transient low mass X-ray binary system SAX J1808.4-3658, during an accretion outburst that occurred in August 2019. At the time of the observations, the pulsar was surrounded by an accretion disc, displayed X-ray pulsations and its luminosity was consistent with magnetically funneled accretion onto the neutron star. Current accretion models fail to account for the luminosity of both optical and ultraviolet pulsations; these are instead more likely driven by synchro-curvature radiation in the pulsar magnetosphere or just outside of it. This interpretation would imply that particle acceleration can take place even when mass accretion is going on, and opens up new perspectives in the study of coherent optical/UV pulsations from fast spinning accreting neutron stars in low-mass X-ray binary systems.

Access to microarcsecond astrometry is now routine in the radio, infrared, and optical domains. In particular the publication of the second data release from the Gaia mission made it possible for every astronomer to work with easily accessible, high-precision astrometry for 1.7 billion sources to 21st magnitude over the full sky. * Gaia provides splendid astrometry but at the limits of the data small systematic errors are present. A good understanding of the Hipparcos/Gaia astrometry concept, and of the data collection and processing, provides insights into the origins of the systematic errors and how to mitigate their effects. * A selected set of results from Gaia highlight the breadth of exciting science and unexpected results, from the solar system to the distant universe, to creative uses of the data. * Gaia DR2 provides for the first time a dense sampling of Galactic phase space with high precision astrometry, photometry, and radial velocities, allowing to uncover subtle features in phase space and the observational HR diagram. * In the coming decade, we can look forward to more accurate and richer Gaia data releases, and new photometric and spectroscopic surveys coming online that will provide essential complementary data. * The longer term promises exciting new opportunities for microarcsecond astrometry and beyond, including the plans for an infrared version of Gaia which would offer the dense sampling of phase space deep into the Milky Way's nuclear regions.

We present observations of the stellar kinematics of the centre of the core collapsed globular cluster M15 obtained with the MUSE integral field spectrograph on the VLT operating in narrow field mode. Thanks to the use of adaptive optics, we obtain a spatial resolution of 0.1arcsec and are able to reliably measure the radial velocities of 864 stars within 8 arcsec of the centre of M15 thus providing the largest sample of radial velocities ever obtained for the innermost regions of this system. Combined with previous observations of M15 using MUSE in wide field mode and literature data, we find that the central kinematics of M15 are complex with the rotation axis of the core of M15 offset from the rotation axis of the bulk of the cluster. While this complexity has been suggested by previous work, we confirm it at higher significance and in more detail.

We report the detection of multiple faint radio sources, that we identify as AGN-jets, within CLJ1449+0856 at z=2 using 3 GHz VLA observations. We study the effects of radio-jet based kinetic feedback at high redshifts, which has been found to be crucial in low redshift clusters to explain the observed thermodynamic properties of their ICM. We investigate this interaction at an epoch featuring high levels of AGN activity and a transitional phase of ICM in regards to the likelihood of residual cold-gas accretion. We measure a total flux of $\rm 30.6 \pm 3.3~\mu Jy$ from the 6 detected jets. Their power contribution is estimated to be $1.2 ~(\pm 0.6)~ \times 10^{44} ~\rm ergs~ s^{-1}$, although this value could be up to $4.7 ~ \times 10^{44} ~\rm ergs~ s^{-1}$. This is a factor $\sim 0.25 - 1.0$ of the previously estimated instantaneous energy injection into the ICM of CLJ1449+0856 from AGN outflows and star formation, that have already been found to be sufficient in globally offsetting the cooling flows in the cluster core. In line with the already detected abundance of star formation, this mode of feedback being distributed over multiple sites, contrary to a single central source observed at low redshifts, points to accretion of gas into the cluster centre. This also suggests a 'steady state' of the cluster featuring non cool-core like behaviour. Finally, we also examine the TIR-radio luminosity ratio for the known sample of galaxies within the cluster core and find that dense environments do not have any serious consequence on the compliance of galaxies to the IR-radio correlation.

The Very Large Array Sky Survey (VLASS) is observing the entire sky north of $-40^{\circ}$ in the S-band ($2<\nu<4\,$GHz), with the highest angular resolution ($2''.5$) of any all-sky radio continuum survey to date. VLASS will cover its entire footprint over three distinct epochs, the first of which has now been observed in full. Based on rapidly produced Quick Look images from this first epoch, we have created a catalog of $1.7\times10^{6}$ reliably detected radio components with $S_{\text{peak}}\gtrsim1\,$mJy/beam. We describe the production of this catalog and quantify the impact of the limited-quality Quick Look images on the scientific usability of the resultant data. Comparisons with independent observations show that flux density measurements at $S_{\text{peak}}\gtrsim3\,$mJy/beam are systematically underestimated by $\sim10\,\%$. Components with $S_\text{peak}<3\,$mJy/beam often have unreliable flux density measurements. We use this catalog to perform a statistical analysis of the $\nu \sim 3\,$GHz radio sky. Comparisons with the Faint Images of the Radio Sky at Twenty cm survey (FIRST) show the typical $1.4-3\,$GHz spectral index to be $\alpha\sim-0.76$. The radio color-color distribution of both point and extended VLASS components is explored by matching with FIRST and the LOFAR Two Meter Sky Survey. The VLASS $dN/dS$ is presented and found to be consistent with previous observations at both $1.4$ and $3\,$GHz. The improved resolution of VLASS relative to FIRST is demonstrated by excess power in the VLASS two-point correlation function at $\theta\lesssim 7''$, and by $17\,\%$ of active galactic nuclei associated with single FIRST component being observed as multi-component sources by VLASS.

Tidally locked exoplanets likely host global atmospheric circulations with a superrotating equatorial jet, planetary-scale stationary waves and thermally-driven overturning circulation. In this work, we show that each of these features can be separated from the total circulation by using a Helmholtz decomposition, which splits the circulation into rotational (divergence free) and divergent (vorticity free) components. This technique is applied to the simulated circulation of a terrestrial planet and a gaseous hot Jupiter. For both planets, the rotational component comprises the equatorial jet and stationary waves, and the divergent component contains the overturning circulation. Separating out each component allows us to evaluate their spatial structure and relative contribution to the total flow. In contrast with previous work, we show that divergent velocities are not negligible when compared with rotational velocities, and that divergent, overturning circulation takes the form of a single, roughly isotropic cell that ascends on the day-side and descends on the night-side. These conclusions are drawn for both the terrestrial case and the hot Jupiter. To illustrate the utility of the Helmholtz decomposition for studying atmospheric processes, we compute the contribution of each of the circulation components to heat transport from day- to night-side. Surprisingly, we find that the divergent circulation dominates day-night heat transport in the terrestrial case and accounts for around half of the heat transport for the hot Jupiter. The relative contributions of the rotational and divergent components to day-night heat transport are likely sensitive to multiple planetary parameters and atmospheric processes, and merit further study.

The Peaks of Eternal Light (PELs), that are largely unshaded regions mostly at the lunar south pole, have been suggested as a source of solar power for mining the water and other volatiles in the nearby permanently dark regions. As mining is a power-intensive activity, it is interesting to estimate the maximum solar power that could be generated at the PELs. Here we use average percentage illumination maps for a range of heights above the local topography from 2 m to 2 km to determine the total power available as a function of time of lunar day. Overshadowing of highly illuminated areas by towers placed in sunward locations (at a given time of day) limits the total power to much smaller values than the highly illuminated area would suggest. We find that for near-term realizable towers (up to 20 m), the upper limit to the time-averaged power available is ~55 MW at >70% illumination, and ~6 MW at >90% illumination. For the more distant future a maximum time-averaged power of order 21000 MW at >70% illumination could be realizable for towers up to 2 km in height, and ~5270 MW, respectively, at 90% illumination. Towers 1 km high provide about a factor 2.7 times less power. The variation with lunar time of day ranges from a factor of 1.1 to ~ 3.

Blazars emit a highly-variable non-thermal spectrum. It is usually assumed that the same non-thermal electrons are responsible for the IR-optical-UV emission (via synchrotron) and the gamma-ray emission (via inverse Compton). Hence, the light curves in the two bands should be correlated. Orphan gamma-ray flares (i.e., lacking a luminous low-frequency counterpart) challenge our theoretical understanding of blazars. By means of large-scale two-dimensional radiative particle-in-cell simulations, we show that orphan gamma-ray flares may be a self-consistent by-product of particle energization in turbulent magnetically-dominated pair plasmas. The energized particles produce the gamma-ray flare by inverse Compton scattering an external radiation field, while the synchrotron luminosity is heavily suppressed since the particles are accelerated nearly along the direction of the local magnetic field. The ratio of inverse Compton to synchrotron luminosity is sensitive to the initial strength of turbulent fluctuations (a larger degree of turbulent fluctuations weakens the anisotropy of the energized particles, thus increasing the synchrotron luminosity). Our results show that the anisotropy of the non-thermal particle population is key to modeling the blazar emission.

In this paper we test if the $\sim$ 0.3 - 15 keV XMM-Newton EPIC pn spectral continuum of IPs can be described by the thermal Comptonization compTT model. We used publicly observations of 12 IPs (AE Aqr, EX Hya, V1025 Cen, V2731 Oph, RX J2133.7+5107, PQ Gem, NY Lup, V2400 Oph, IGR J00234+6141, IGR J17195-4100, V1223 Sgr, and XY Ari). We find that our modeling is capable to fit well the average spectral continuum of these sources. In this framework, UV/soft X-ray seed photons (with $<kT_s>$ of 0.096 $\pm$ 0.013 keV) coming presumably from the star surface are scattered off by electrons present in an optically thick plasma (with $<kT_e>$ of 3.05 $\pm$ 0.16 keV and optical depth $<\tau>$ of 9.5 $\pm$ 0.6 for plane geometry) located nearby (on top) to the more central seed photon emission regions. A soft blackbody (bbody) component is observed in 5 out of the 13 observations analysed, with a mean temperature $<kT_{bb}>$ of $0.095 \pm 0.004$ keV. We observed that the spectra of IPs show in general two photon indices $\Gamma$, which are driven by the source luminosity and optical depth. Low luminosity IPs show $<\Gamma>$ of $1.83 \pm 0.19$, whereas high luminosity IPs show lower $<\Gamma>$ of $1.34 \pm 0.02$. Moreover, the good spectral fits of PQ Gem and V2400 Oph indicate that the polar subclass of CVs may be successfully described by the thermal Comptonization as well.

This study applies a new approach, the Theory of Functional Connections (TFC), to solve the two-point boundary-value problem (TPBVP) in non-Keplerian orbit transfer. The perturbations considered are drag, solar radiation pressure, higher-order gravitational potential harmonic terms, and multiple bodies. The proposed approach is applied to Earth-to-Moon transfers, and obtains exact boundary condition satisfaction and with very fast convergence. Thanks to this highly efficient approach, perturbed pork-chop plots of Earth-to-Moon transfers are generated, and individual analyses on the transfers' parameters are easily done at low computational costs. The minimum fuel analysis is provided in terms of the time of flight, thrust application points, and relative geometry of the Moon and Sun. The transfer costs obtained are in agreement with the literature's best solutions, and in some cases are even slightly better.

This work explores the dynamic properties of test particles surrounding a distorted, deformed compact object. The astrophysical motivation was to choose such background, which could constitute a more reasonable model of a real situation that arises in the vicinity of compact objects with the possibility of having parameters as the extra physical degrees of freedom. This can facilitate associating observational data with astrophysical systems. This work's main goal is to study the dynamic regime of motion and quasi-periodic oscillation in this background, depending on different parameters of the system. Also, we exercise the resonant phenomena of the radial and vertical oscillations at their observed quasi-periodic oscillations frequency ratio of 3:2.

Black hole superradiance is a powerful tool in the search for ultra-light bosons. Constraints on the existence of such particles have been derived from the observation of highly spinning black holes, absence of continuous gravitational-wave signals, and of the associated stochastic background. However, these constraints are only strictly speaking valid in the limit where the boson's interactions can be neglected. In this work we investigate the extent to which the superradiant growth of an ultra-light dark photon can be quenched via scattering processes with ambient electrons. For dark photon masses $m_{\gamma^\prime} \gtrsim 10^{-17}\,{\rm eV}$, and for reasonable values of the ambient electron number density, we find superradiance can be quenched prior to extracting a significant fraction of the black-hole spin. For sufficiently large $m_{\gamma^\prime}$ and small electron number densities, the in-medium suppression of the kinetic mixing can be efficiently removed, and quenching occurs for mixings $\chi_0 \gtrsim \mathcal{O}(10^{-8})$; at low masses, however, in-medium effects strongly inhibit otherwise efficient scattering processes from dissipating energy. Intriguingly, this quenching leads to a time- and energy-oscillating electromagnetic signature, with luminosities potentially extending up to $\sim 10^{57}\,{\rm erg / s}$, suggesting that such events should be detectable with existing telescopes. As a byproduct we also show that superradiance cannot be used to constrain a small mass for the Standard Model photon.

Subcomponent millicharged dark matter that cools baryons via Coulomb interactions has been invoked to explain the EDGES anomaly. However, this model is in severe tension with constraints from cosmology and stellar emissions. In this work, we consider the consequences of these millicharged particles existing in composite blobs. The relevant degrees of freedom at high temperature are minuscule elementary charges, which fuse at low temperatures to make up blobs of larger charge. These blobs serve as the degrees of freedom relevant in cooling the baryons sufficiently to account for the EDGES anomaly. In such a model, cosmology and stellar constraints (which involve high-temperature processes) apply only to the feebly-interacting elementary charges and not to the blobs. This salvages a large range of parameter space for millicharged blobs that can explain the EDGES anomaly. It also opens up new parameter space for direct detection, albeit at low momentum transfers.

In this work, we estimate the background components in muography using the MuTe: a hybrid muon telescope composed of two subdetectors -a scintillator hodoscope and a Water Cherenkov Detector (WCD). The hodoscope records the trajectories of particles crossing the telescope, while the WCD measures their energy loss. The MuTe hodoscope reconstructs 3841 different directions with an angular resolution of 32 mrad for an inter-panel distance of 2.5 m. The spatial resolution can reach $\sim$25.6 m assuming an 800 m distance to the target. The WCD measures the deposited energy from 50 MeV to 1.5 GeV with a resolution of 0.72 MeV. MuTe discriminates muography background sources such as: upward coming muons, scattered muons, the soft component of Extensive Air Showers (EAS), and particles arriving simultaneously. They are filtered by using measurements of deposited energy (WCD) and Time-of-Flight. The WCD differentiates single muons, electrons/positrons, and multiparticle events. On the other hand, the ToF measurements allow us to estimate the muon momentum establishing an energy threshold to decrease the background contribution of scattered muons. Upward coming muons are rejected by means of the particle arrival direction determined by the ToF sign. We concluded that near 36% of the recorded events belong to the electromagnetic component (electrons and positrons), roughly 30.4% is caused by multiple particle events that arrive with time differences < 100 ns and the last 34% are caused by muons. The muonic soft component (< 1 GeV/c) represents 46% of the single-muon events. The upward going particles add up the 22% of the total flux crossing the MuTe.

Motivated by the astrophysical problems of star formations from molecular clouds, we make the first step on the possible behaviors of certain molecular clouds. This article $(1)$ establishes the diffuse boundary problem of Euler-Poisson system for describing the evolution of molecular clouds; $(2)$ proves the local existence, uniqueness and continuation principle of the classical solution to the diffuse boundary problem; $(3)$ proves the classical solution (without any symmetry condition) to the diffuse problem blows up at finite time if there is no the first class of global solution and the data is admissible (large scale, irregularly-shaped, expanding and rotational molecular clouds); $(4)$ proves certain singularities can be removed from the boundary if the data is strongly admissible. This result partially answers Makino's conjecture $[69]$ on the finite blowup of any tame solution without symmetries and gives the possibilities of star formations, fragmentation and possibilities of formations of shocks and physical vacuum boundary in perfect fluids with Newtonian self-gravity.

We consider two classes of steady states of the three-dimensional, gravitational Vlasov-Poisson system: the spherically symmetric Antonov-stable steady states (including the polytropes and the King model) and their plane symmetric analogues. We completely describe the essential spectrum of the self-adjoint operator governing the linearized dynamics in the neighborhood of these steady states. We also show that for the steady states under consideration, there exists a gap in the spectrum. We then use a version of the Birman-Schwinger principle first used by Mathur to derive a general criterion for the existence of an eigenvalue inside the first gap of the essential spectrum, which corresponds to linear oscillations about the steady state. It follows in particular that no linear Landau damping can occur in the neighborhood of steady states satisfying our criterion. Verification of this criterion requires a good understanding of the so-called period function associated with each steady state. In the plane symmetric case we verify the criterion rigorously, while in the spherically symmetric case we do so under a natural monotonicity assumption for the associated period function. Our results explain the pulsating behavior triggered by perturbing such steady states, which has been observed numerically.

In scale-invariant models of fundamental physics, mass scales are generated by spontaneous symmetry breaking. In this work, we study inflation in scale-invariant $R^2$ gravity, in which the Planck mass is generated by a scalar field, which is responsible for spontaneous breaking of scale--symmetry. If the self-interactions of the scalar field are non-zero, a cosmological constant is generated, which can be potentially quite large. To avoid fine-tuning at late times, we introduce another scalar field which drives the classical cosmological constant to zero during inflation. Working in the Einstein-frame, we find that due to a conserved Noether current the corresponding three-field inflationary model (consisting of the two scalar fields plus the scalaron) becomes effectively a two-field model. The prize to be paid for introducing the field which cancels the classical cosmological constant at the end of inflation is that the running of the spectral index and the running of the running can be quite large due to entropy perturbations during inflation, making the model testable with future cosmological experiments.

We study how the evolution of a Dark Energy Quintessence fluid is modified by the presence of a matter inhomogeneity. To do so, we study linear perturbations of a flat FLRW background containing dust and a slowly rolling scalar field. Under the assumptions of spherical symmetry and a static density contrast, \textit{i.e.} $\dot{\delta}=0$, we obtain simple analytical solutions for perturbations in the matter and dark energy-dominated epochs. As a consequence, we show that perturbations of the scalar field, if a coupling \textit{\`a la} Bekenstein is assumed, trigger a spatial dependence of the fine-structure "constant" which then varies as $\Delta \alpha \propto 1/r$. We finally highlight that such variations can be constrained with spectroscopic observations of stars from within our galaxy, therefore offering a new probe of the nature of Dark Energy.

LUX-ZEPLIN (LZ) is a dark matter detector expected to obtain world-leading sensitivity to weakly interacting massive particles (WIMPs) interacting via nuclear recoils with a ~7-tonne xenon target mass. This manuscript presents sensitivity projections to several low-energy signals of the complementary electron recoil signal type: 1) an effective neutrino magnetic moment and 2) an effective neutrino millicharge, both for pp-chain solar neutrinos, 3) an axion flux generated by the Sun, 4) axion-like particles forming the galactic dark matter, 5) hidden photons, 6) mirror dark matter, and 7) leptophilic dark matter. World-leading sensitivities are expected in each case, a result of the large 5.6t 1000d exposure and low expected rate of electron recoil backgrounds in the $<$100keV energy regime. A consistent signal generation, background model and profile-likelihood analysis framework is used throughout.