Papers for Friday, Jul 01 2022

Stars provide an enormous gain for interstellar communications at their gravitational focus, perhaps as part of an interstellar network. If the Sun is part of such a network, there should be probes at the gravitational foci of nearby stars. If there are probes within the solar system connected to such a network, we might detect them by intercepting transmissions from relays at these foci. Here, we demonstrate a search across a wide bandwidth for interstellar communication relays beyond the Sun's innermost gravitational focus at 550 AU using the Green Bank Telescope (GBT) and Breakthrough Listen (BL) backend. As a first target, we searched for a relay at the focus of the Alpha Centauri AB system while correcting for the parallax due to Earth's orbit around the Sun. We searched for radio signals directed at the inner solar system from such a source in the L and S bands. Our analysis, utilizing the turboSETI software developed by BL, did not detect any signal indicative of a non-human-made artificial origin. Further analysis excluded false negatives and signals from the nearby target HD 13908. Assuming a conservative gain of 10^3 in L-band and roughly 4 times that in S-band, a ~1 meter directed transmitter would be detectable by our search above 7 W at 550 AU or 23 W at 1000 AU in L-band, and above 2 W at 550 AU or 7 W at 1000 AU in S-band. Finally, we discuss the application of this method to other frequencies and targets.

The idea of a planetary origin for the solar cycle dates back to the nineteenth century. Despite unsurmounted problems, it is still advocated by some. Stefani, Giesecke, and Weier (2019) thus recently proposed a scenario based on this idea. A key argument they put forward is evidence that the $\sim$11 years-solar cycle is clocked. Their demonstration rests upon the computation of a ratio proposed by Dicke (1978) applied to the solar cycle time series of Schove (1955). I show that their demonstration is invalid, because the assumptions used by Schove to build his time series force a clocked behaviour. I also show that instabilities in a magnetized fluid can produce fluctuation time series that are close to being clocked.

We analyze the completeness of the MOSDEF survey, in which z ~ 2 galaxies were selected for rest-optical spectroscopy from well-studied HST extragalactic legacy fields down to a fixed rest-optical magnitude limit (H_AB = 24.5). The subset of z ~ 2 MOSDEF galaxies with high signal-to-noise (S/N) emission-line detections analyzed in previous work represents a small minority (<10%) of possible z ~ 2 MOSDEF targets. It is therefore crucial to understand how representative this high S/N subsample is, while also more fully exploiting the MOSDEF spectroscopic sample. Using spectral-energy-distribution (SED) models and rest-optical spectral stacking, we compare the MOSDEF z ~ 2 high S/N subsample with the full MOSDEF sample of z ~ 2 star-forming galaxies with redshifts, the latter representing an increase in sample size of more than a factor of three. We find that both samples have similar emission-line properties, in particular in terms of the magnitude of the offset from the local star-forming sequence on the [N II] BPT diagram. There are small differences in median host galaxy properties, including the stellar mass (M_*), star-formation rate (SFR) and specific SFR (sSFR), and UVJ colors; however, these offsets are minor considering the wide spread of the distributions. Using SED modeling, we also demonstrate that the sample of z ~ 2 star-forming galaxies observed by the MOSDEF survey is representative of the parent catalog of available such targets. We conclude that previous MOSDEF results on the evolution of star-forming galaxy emission-line properties were unbiased relative to the parent z ~ 2 galaxy population.

A unique challenge for data analysis with the Laser Interferometer Space Antenna (LISA) is that the noise backgrounds from instrumental noise and astrophysical sources will change significantly over both the year and the entire mission. Variations in the noise levels will be on time scales comparable to, or shorter than, the time most signals spend in the detector's sensitive band. The variation in the amplitude of the galactic stochastic GW background from galactic binaries as the antenna pattern rotates relative to the galactic center is a particularly significant component of the noise variation. LISA's sensitivity to different source classes will therefore vary as a function of sky location and time. The variation will impact both overall signal-to-noise and the efficiency of alerts to EM observers to search for multi-messenger counterparts.

A key goal of heliophysics is to understand how cosmic rays propagate in the solar system's complex, dynamic environment. One observable is solar modulation, i.e., how the flux and spectrum of cosmic rays changes as they propagate inward. We construct an improved force-field model, taking advantage of new measurements of magnetic power spectral density by Parker Solar Probe to predict solar modulation within the Earth's orbit. We find that modulation of cosmic rays between the Earth and Sun is modest, at least at solar minimum and in the ecliptic plane. Our results agree much better with the limited data on cosmic-ray radial gradients within Earth's orbit than past treatments of the force-field model. Our predictions can be tested with forthcoming direct cosmic-ray measurements in the inner heliosphere by Parker Solar Probe and Solar Orbiter. They are also important for interpreting the gamma-ray emission from the Sun due to scattering of cosmic rays with solar matter and photons.

Machine learning has become widely used in astronomy. Gaussian Process (GP) regression in particular has been employed a number of times to fit or re-sample supernova (SN) light-curves, however by their nature typical GP models are not suited to fit SN photometric data and they will be prone to over-fitting. Recently GP re-sampling was used in the context of studying the morphologies of type II and IIb SNe and they were found to be clearly distinct with respect to four parameters: the rise time (t$_{\rm rise}$), the magnitude difference between 40 and 30 days post explosion ($\Delta m_{\rm 40-30}$), and the earliest maxima of the first and second derivative of the light curve (dm1 and dm2). Here we take a close look at Gaussian process regression and its limitations in the context of SNe light-curves in general, and we also discuss the uncertainties on these specific parameters, finding that dm1 and dm2 cannot give reliable astrophysical information. We do reproduce the clustering in t$_{\rm rise}$--$\Delta m_{\rm 40-30}$ space although it is not as clear cut as previously presented. The best strategy to accurately populate the t$_{\rm rise}$-- $\Delta m_{\rm 40-30}$ space will be to use an expanded sample of high quality light-curves (such as those in the ATLAS transient survey) and analytical fitting methods. Finally, using the BPASS fiducial models, we predict that future photometric studies will reveal clear clustering of the type IIb and II light curve morphologies with a distinct continuum of transitional events.

We present a new analytical solution to the steady-state distribution of stars close to a central supermassive black hole of mass $M_{\bullet}$ in the center of a galaxy. Assuming a continuous mass function of the form $dN/dm \propto m^{\gamma}$, stars with a specific orbital energy $x = GM_{\bullet}/r - v^2/2$ are scattered primarily by stars of mass $m_{\rm d}(x) \propto x^{-5/(4\gamma+10)}$ that dominate the scattering of both lighter and heavier species at that energy. Stars of mass $m_{\rm d}(x)$ are exponentially rare at energies lower than $x$, and follow a density profile $n(x') \propto x'^{3/2}$ at energies $x' \gg x$. Our solution predicts a negligible flow of stars through energy space for all mass species, similarly to the conclusions of Bahcall & Wolf (1977), but in contrast to the assumptions of Alexander & Hopman (2009). This is the first analytic solution which smoothly transitions between regimes where different stellar masses dominate the scattering.

We study the relationship between the scale-height of the molecular gas disc and the turbulent velocity dispersion of the molecular interstellar medium within a simulation of a Milky Way-like galaxy in the moving-mesh code Arepo. We find that the vertical distribution of molecular gas can be described by a Gaussian function with a uniform scale-height of ~50 pc. We investigate whether this scale-height is consistent with a state of hydrostatic balance between gravity and turbulent pressure. We find that the hydrostatic prediction using the total turbulent velocity dispersion (as one would measure from kpc-scale observations) gives an over-estimate of the true molecular disc scale-height. The hydrostatic prediction using the velocity dispersion between the centroids of discrete giant molecular clouds (cloud-cloud velocity dispersion) leads to more-accurate estimates. The velocity dispersion internal to molecular clouds is elevated by the locally-enhanced gravitational field. Our results suggest that observations of molecular gas need to reach the scale of individual molecular clouds in order to accurately determine the molecular disc scale-height.

From the nature of dark matter to the rate of expansion of our Universe, observations of distant galaxies distorted through strong gravitational lensing have the potential to answer some of the major open questions in astrophysics. Modeling galaxy-galaxy strong lensing observations presents a number of challenges as the exact configuration of both the background source and foreground lens galaxy is unknown. A timely call, prompted by a number of upcoming surveys anticipating high-resolution lensing images, demands methods that can efficiently model lenses at their full complexity. In this work, we introduce a method that uses continuous neural fields to non-parametrically reconstruct the complex morphology of a source galaxy while simultaneously inferring a distribution over foreground lens galaxy configurations. We demonstrate the efficacy of our method through experiments on simulated data targeting high-resolution lensing images similar to those anticipated in near-future astrophysical surveys.

Delayed radio flares of optical tidal disruption events (TDEs) indicate the existence of non-relativistic outflows accompanying TDEs. The interaction of TDE outflows with the surrounding circumnuclear medium creates quasi-perpendicular shocks in the presence of toroidal magnetic fields. Because of the large shock obliquity and large outflow velocity, we find that the shock acceleration induced by TDE outflows generally leads to a steep particle energy spectrum, with the power-law index significantly larger than the "universal" index for a parallel shock. The measured synchrotron spectral indices of recently detected TDE radio flares are consistent with our theoretical expectation. It suggests that the particle acceleration at quasi-perpendicular shocks can be the general acceleration mechanism accounting for the delayed radio emission of TDEs.

In intermediate-temperature (T = 2.5 - 4.5 keV) galaxy clusters, abundance measurements are almost-equally driven by Fe K and L transitions, at $\sim$ 6.7 keV and 0.9 - 1.3 keV, respectively. While K-shell-derived measurements are considered reliable, the resolution of the currently available instrumentation, as well as our current knowledge of the atomic processes, makes the modelling of the L-line complex challenging, resulting in potential biases for abundance measurements. In this work, we study systematics related to the modelling of the Fe L-line complex that may influence iron-abundance measurements in the intermediate-temperature range. To this aim, we select a sample of three bright galaxy clusters, with long XMM-Newton observations available and temperature in the 2.5 - 4.5 keV range. We fit spectra extracted from concentric rings with APEC and APEC+APEC models, by alternatively excluding the L and K bands, and derive the fractional difference of the metal abundances, $\Delta Z/Z$, as indication of the consistency between K- and L-shell-derived measurements. The $\Delta Z/Z$ distribution is then studied as a function of the cluster radius, ring temperature and X-ray flux. The L-induced systematics, measured through an individual fit of each MOS and pn spectrum, remain constant at a 5 - 6% value in the whole 2.5 - 4.5 keV temperature range. Conversely, a joint fit of MOS and pn spectra leads to a slight excess of 1 - 2% in the above estimate. No significant dependence on the ring X-ray flux is highlighted. The measured 5 - 8% value indicates a modest contribution of the systematics to the derived iron abundances, giving confidence for future measurements. To date, these findings represent the best-achievable estimate of the systematics in analysis, while future microcalorimeters will significantly improve our understanding of the atomic processes underlying the Fe L emissions.

We present a new set of cosmological zoom-in simulations of a MW-like galaxy which for the first time include elastic velocity-dependent self interacting dark matter (SIDM) and IllustrisTNG physics. With these simulations we investigate the interaction between SIDM and baryons and its effects on the galaxy evolution process. We also introduce a novel set of modified DMO simulations which can reasonably replicate the effects of fully realized hydrodynamics on the DM halo while simplifying the analysis and lowering the computational cost. We find that baryons change the thermal structure of the central region of the halo to a greater extent than the SIDM scatterings for MW-like galaxies. Additionally, we find that the new thermal structure of the MW-like halo causes SIDM to create cuspier central densities rather than cores because the SIDM scatterings remove the thermal support by transferring heat away from the center of the galaxy. We find that this effect, caused by baryon contraction, begins to affect galaxies with a stellar mass of $10^8$ M$_\odot$ and increases in strength to the MW-mass scale. This implies that any simulations used to constrain the SIDM cross sections for galaxies with stellar masses between $10^8$ and at least $10^{11}$ M$_\odot$ will require baryons to make accurate predictions.

Dark compact objects ("clumps") transiting the Solar System exert accelerations on the test masses (TM) in a gravitational-wave (GW) detector. We reexamine the detectability of these clump transits in a variety of current and future GW detectors, operating over a broad range of frequencies. TM accelerations induced by clump transits through the inner Solar System have frequency content around $f \sim \mu$Hz. Some of us [arXiv:2112.11431] recently proposed a GW detection concept with $\mu$Hz sensitivity, based on asteroid-to-asteroid ranging. From the detailed sensitivity projection for this concept, we find both analytically and in simulation that purely gravitational clump-matter interactions would yield one detectable transit every $\sim20$ yrs, if clumps with mass $m_{\text{cl}} \sim 10^{14} \text{kg}$ saturate the dark-matter (DM) density. Other (proposed) GW detectors using local TMs and operating in higher frequency bands, are sensitive to smaller clump masses and have smaller rates of discoverable signals. We also consider the case of clumps endowed with an additional long-range clump-matter fifth force significantly stronger than gravity (but evading known fifth-force constraints). For the $\mu$Hz detector concept, we use simulations to show that, for example, a clump-matter fifth-force $\sim 10^3$ times stronger than gravity with a range of $\sim$ AU would boost the rate of detectable transits to a few per year for clumps in the mass range $10^{11} \text{kg} \lesssim m_{\text{cl}} \lesssim 10^{14} \text{kg}$, even if they are a $\sim 1$% sub-component of the DM. The ability of $\mu$Hz GW detectors to probe asteroid-mass-scale dark objects that may otherwise be undetectable bolsters the science case for their development.

In 1933, Fritz Zwicky's famous investigations of the mass of the Coma cluster led him to infer the existence of dark matter \cite{1933AcHPh...6..110Z}. His fundamental discoveries have proven to be foundational to modern cosmology; as we now know such dark matter makes up 85\% of the matter and 25\% of the mass-energy content in the universe. Galaxy clusters like Coma are massive, complex systems of dark matter in addition to hot ionized gas and thousands of galaxies, and serve as excellent probes of the dark matter distribution. However, empirical studies show that the total mass of such systems remains elusive and difficult to precisely constrain. Here, we present new estimates for the dynamical mass of the Coma cluster based on Bayesian deep learning methodologies developed in recent years. Using our novel data-driven approach, we predict Coma's $\mthc$ mass to be $10^{15.10 \pm 0.15}\ \hmsun$ within a radius of $1.78 \pm 0.03\ h^{-1}\mathrm{Mpc}$ of its center. We show that our predictions are rigorous across multiple training datasets and statistically consistent with historical estimates of Coma's mass. This measurement reinforces our understanding of the dynamical state of the Coma cluster and advances rigorous analyses and verification methods for empirical applications of machine learning in astronomy.

Ground based observations appear to indicate that Ultra High Energy Cosmic Rays (UHECR) of the highest energies (>10^{18.7} eV) consist of heavy particles -- shower depth and muon production data both pointing towards this conclusion. On the other hand, cosmic-ray arrival directions at energies >10^{18.9} eV exhibit a dipole anisotropy, which disfavours heavy composition, since higher-Z nuclei are strongly deflected by the Galactic magnetic field, suppressing anisotropy. This is the composition problem of UHECR. One solution could be the existence of yet-unknown effects in proton interactions at CM energies 50 TeV, which would alter the interaction cross section and the multiplicity of interaction products, mimicking heavy primaries. We aim to study the impact of such changes on cosmic-ray observables using simulations of Extensive Air-Shower (EAS), in order to place constrains on the phenomenology of any new effects for high energy proton interactions that could be probed by sqrt{s}>50 TeV collisions. We simulated showers of primaries with energies in the range 10^{17} - 10^{20} eV using the CORSIKA code, modified to implement a possible increase in cross-section and multiplicity in hadronic collisions exceeding a center-of-mass (CM) energy of 50 TeV threshold. We studied the composition-sensitive shower observables (shower depth, muons) as a function of cross-section, multiplicity, and primary energy. We found that in order to match the Auger shower depth measurements by means of new hadronic collision effects alone (if extragalactic UHECR are all protons even at the highest energies), the cross-section of proton-air interactions has to be 800 mb at 140 TeV CM energy, accompanied by an increase of a factor of 2-3 in secondary particles. We also studied the muon production of the showers in the same scenario.

Parametric equations of state (EoSs) provide an important tool for systematically studying EoS effects in neutron star merger simulations. In this work, we perform a numerical validation of the M*-framework for parametrically calculating finite-temperature EoS tables. The framework, introduced in Raithel et al. (2019), provides a model for generically extending any cold, beta-equilibrium EoS to finite-temperatures and arbitrary electron fractions. In this work, we perform numerical evolutions of a binary neutron star merger with the SFHo finite-temperature EoS, as well as with the M*-approximation of this same EoS, where the approximation uses the zero-temperature, beta-equilibrium slice of SFHo and replaces the finite-temperature and composition-dependent parts with the M*-model. We find that the approximate version of the EoS is able to accurately recreate the temperature and thermal pressure profiles of the binary neutron star remnant, when compared to the results found using the full version of SFHo. We additionally find that the merger dynamics and gravitational wave signals agree well between both cases, with differences of ~1-2% introduced into the post-merger gravitational wave peak frequencies by the approximations of the EoS. We conclude the M*-framework can be reliably used to probe neutron star merger properties in numerical simulations.

Taking advantage of the recent Gaia Data Release 3 (DR3), we map chemical inhomogeneities in the Milky Way's disc out to a distance of $\sim$ 4 kpc of the Sun, using different samples of bright giant stars (log($g$) < 1.5 dex, T$_{\rm{eff}}$ \sim 3500-5500 K). We detect remarkable inhomogeneities, which appear to be more prominent and structured for the sample containing stars with relatively hotter effective temperatures. For this sample, we identify three (possibly four) metal-rich elongated features in the Galactic plane, which are located in proximity of the spiral arms in the Galactic disc. When projected onto Galactic radius, those features manifest themselves as statistically significant bumps on top of the observed radial gradients, making the assumption of a linear radial decrease not applicable to this sample. In contrast, the sample containing cooler giants exhibits a relatively smooth decrease as a function of Galactic radius. Considering different slices in Galactic azimuth $\phi$, the slope of the measured radial metallicity gradient for the cool giants varies gradually from $\sim$-0.05 dex kpc$^{-1}$ at $\phi \sim -20^{\circ}$ to $\sim$ -0.03 dex kpc$^{-1}$ at $\phi \sim 20^{\circ}$. The strong correlation between the spiral structure of the Galaxy and the observed chemical pattern in the sample with relatively hotter effective temperatures indicates that the spiral arms might be at the origin for the detected chemical inhomogeneities. In this scenario, the spiral arms would leave in the hotter stars a strong signature, which progressively disappears when cooler giants stars are considered.

We present photometric metallicity measurements for a sample of 2.6 million bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS). Similar to previous studies, we find that the bulge exhibits a strong vertical metallicity gradient, and that at least two peaks in the metallicity distribution functions appear at b < -5. We can discern a metal-poor ([Fe/H] ~ -0.3) and metal-rich ([Fe/H] ~ +0.2) abundance distribution that each show clear systematic trends with latitude, and may be best understood by changes in the bulge's star formation/enrichment processes. Both groups exhibit asymmetric tails, and as a result we argue that the proximity of a star to either peak in [Fe/H] space is not necessarily an affirmation of group membership. The metal-poor peak shifts to lower [Fe/H] values at larger distances from the plane while the metal-rich tail truncates. Close to the plane, the metal-rich tail appears broader along the minor axis than in off-axis fields. We also posit that the bulge has two metal-poor populations -- one that belongs to the metal-poor tail of the low latitude and predominantly metal-rich group, and another belonging to the metal-poor group that dominates in the outer bulge. We detect the X-shape structure in fields with |Z| > 0.7 kpc and for stars with [Fe/H] > -0.5. Stars with [Fe/H] < -0.5 may form a spheroidal or "thick bar" distribution while those with [Fe/H] > -0.1 are strongly concentrated near the plane.

(Abridged) Long Gamma-Ray Bursts (GRBs) offer a promising tool to trace the cosmic history of star formation, especially at high redshift where conventional methods are known to suffer from intrinsic biases. Previous studies of GRB host galaxies at low redshift showed that high surface densities of stellar mass and star formation rate (SFR) can potentially enhance the GRB production. We assess how the size, the stellar mass and SFR surface densities of distant galaxies affect their probability to host a long GRB, using a sample of GRB hosts at $z > 1$ and a control sample of star-forming sources from the field. We gather a sample of 45 GRB host galaxies at $1 < z < 3.1$ observed with the Hubble Space Telescope WFC3 camera in the near-infrared. Using the GALFIT parametric approach, we model the GRB host light profile and derive the half-light radius for 35 GRB hosts, which we use to estimate the SFR and stellar mass surface densities of each object. We compare the distribution of these physical quantities to the SFR-weighted properties of a complete sample of star-forming galaxies from the 3D-HST deep survey at comparable redshift and stellar mass. We show that, similarly to $z < 1$, GRB hosts are smaller in size and they have higher stellar mass and SFR surface densities than field galaxies at $1 < z < 2$. Interestingly, this result is robust even when considering separately the hosts of GRBs with optically-bright afterglows and the hosts of dark GRBs. At $z > 2$ though, GRB hosts appear to have sizes and stellar mass surface densities more consistent with those characterizing the field galaxies. In addition to a possible trend toward low metallicity environment, other environmental properties such as stellar density appears to play a role in the formation of long GRBs, at least up to $z \sim 2$. This might suggest that GRBs require special environments to be produced.

Cometary activity may be driven by ices with very low sublimation temperatures, such as carbon monoxide ice, which can sublimate at distances well beyond 20 au. This point is emphasized by the discovery of Oort cloud comet C/2014 UN$_{271}$ (Bernardinelli-Bernstein), and its observed activity out to $\sim$26 au. Through observations of this comet's optical brightness and behavior, we can potentially discern the drivers of activity in the outer solar system. We present a study of the activity of comet Bernardinelli-Bernstein with broad-band optical photometry taken at 19-20 au from the Sun (2021 June to 2022 February) as part of the LCO Outbursting Objects Key (LOOK) Project. Our analysis shows that the comet's optical brightness during this period was initially dominated by cometary outbursts, stochastic events that ejected $\sim10^7$ to $\sim10^8$ kg of material on short (< 1 day) timescales. We present evidence for three such outbursts occurring in 2021 June and September. The nominal nuclear volumes excavated by these events are similar to the 10-100 m pit-shaped voids on the surfaces of short-period comet nuclei, as imaged by spacecraft. Two out of three Oort cloud comets observed at large pre-perihelion distances exhibit outburst behavior near 20 au, suggesting such events may be common in this population. In addition, quiescent CO-driven activity may account for the brightness of the comet in 2022 January to February, but that variations in the cometary active area (i.e., the amount of sublimating ice) with heliocentric distance are also possible.

Gaseous flows inside and outside galaxies are the key to understand galaxy evolution, as they regulate their star-formation activity across cosmic time. We study the ISM kinematics of 330 CIII] or HeII emitters, using far-UV absorption lines detected in the VANDELS spectra. These galaxies span a broad range of stellar masses from 10$^8$ to 10$^{11}$ M$_\odot$, and SFRs from 1 to 500 M$_\odot$/yr, in the redshift range between 2 and 5. We find that the bulk ISM velocity v$_{ism}$ is globally in outflow, with a v$_{ism}$ of -60 $\pm$ 10 km/s for low ionization gas traced by SiII 1260 Angstrom, CII 1334, SiII 1526, and AlII 1670, and v$_{ism}$ of -160 $\pm$ 30 and -170 $\pm$ 30 km/s for higher ionization gas traced respectively by AlIII 1854-1862 and SiIV 1393-1402. Interestingly, BPASS models are able to better reproduce the stellar continuum around the SiIV doublet than other stellar population templates. We also find that 34% of our sample has signatures of inflows (v$_{ism}>0$), almost double than the fraction reported at lower redshifts. Comparing v$_{ism}$ to the host galaxies properties, we find no significant correlations with the stellar mass and SFR, and a marginally significant dependence (at $\sim 2\sigma$) on morphology related parameters, with slightly higher velocities found in galaxies with smaller size (probed by the equivalent radius), higher concentration and higher SFR surface density. The outflows are consistent with models of accelerating, momentum-driven winds, and density decreasing with radius. Our moderately lower v$_{ism}$ compared to similar studies at lower redshifts suggest that inflows and internal turbulence might play an increased role at z>2. We estimate mass outflow rates comparable to the SFRs of the galaxies, and an average escape velocity of 625 km/s, suggesting that most of the ISM will remain bound to the galaxy halo.

Next generation telescopes, such as Euclid, Rubin/LSST, and Roman, will open new windows on the Universe, allowing us to infer physical properties for tens of millions of galaxies. Machine learning methods are increasingly becoming the most efficient tools to handle this enormous amount of data, not only as they are faster to apply to data samples than traditional methods, but because they are also often more accurate. Properly understanding their applications and limitations for the exploitation of these data is of utmost importance. In this paper we present an exploration of this topic by investigating how well redshifts, stellar masses, and star-formation rates can be measured with deep learning algorithms for galaxies within data that mimics the Euclid and Rubin/LSST surveys. We find that Deep Learning Neural Networks and Convolutional Neutral Networks (CNN), which are dependent on the parameter space of the sample used for training, perform well in measuring the properties of these galaxies and have an accuracy which is better than traditional methods based on spectral energy distribution fitting. CNNs allow the processing of multi-band magnitudes together with $H_{E}$-band images. We find that the estimates of stellar masses improve with the use of an image, but those of redshift and star-formation rates do not. Our best machine learning results are deriving i) the redshift within a normalised error of less than 0.15 for 99.9% of the galaxies in the sample with S/N>3 in the $H_{E}$-band; ii) the stellar mass within a factor of two ($\sim$0.3 dex) for 99.5% of the considered galaxies; iii) the star-formation rates within a factor of two ($\sim$0.3 dex) for $\sim$70% of the sample. We discuss the implications of our work for application to surveys, mainly but not limited to Euclid and Rubin/LSST, and how measurements of these galaxy parameters can be improved with deep learning.

It is well-known that the $\gamma$-ray emission in blazars originate in the relativistic jet pointed at the observers. However, it is not clear whether the exact location of the GeV emission is less than a pc from the central engine, such that it may receive sufficient amount of photons from the broad line region (BLR) or farther out at 1-100 pc range. The former assumption has been successfully used to model the spectral energy distribution of many blazars. However, simultaneous detection of TeV $\gamma$-rays along with GeV outbursts in some cases indicate that the emission region must be outside the BLR. In addition, GeV outbursts have sometimes been observed to be simultaneous with the passing of a disturbance through the so called "VLBI core," which is located tens of pc away from the central engine. Hence, the exact location of $\gamma$-ray emission remains ambiguous. Here we present a method we have developed to constrain the location of the emission region. We identify simultaneous months-timescale GeV and optical outbursts in the light curves spanning over 8 years of a sample of eleven blazars. Using theoretical jet emission models we show that the energy ratio of simultaneous optical and GeV outbursts is strongly dependent on the location of the emission region. Comparing the energy dissipation of the observed multi-wavelength outbursts and that of the simulated flares in our theoretical model we find that most of the above outbursts originate beyond the BLR at approximately a few pc from the central engine.

The precessing jet-nozzle scenario previously proposed was applied to interpret the VLBI-measured kinematics of five superluminal components (C4,C5,C9,C10 and C22) and their flux density evolution in blazar 3C345. It is shown that in the inner-trajectory sections their kinematic properties, including trajectory,coordinates, core separation and apparent velocity can be well model-simulated by using the scenario with a precession period of 7.30yr (4.58yr in the source frame) and a precessing common trajectory, which produces the individual knot-trajectories at their corresponding precession phases. Through the model-simulation of their kinematic behavior their bulk Lorentz factor ,viewing angle and Doppler factor were derived as functions of time. These anticipatively-determined Lorentz/Doppler factors were used to investigate the knots' Doppler-boosting effect and interpret their flux evolution. It was found that the light-curves of the five superluminal components observed at 15, 22 and 43GHz were extraordinarily well coincident with their Doppler boosting profiles. Additionally, some flux fluctuations on shorter time-scales could be due to variations in knots' intrinsic flux and spectral index. The close relation between the flux evolution and the Doppler boosting effect not only firmly validates the precessing jet-nozzle scenario being fully appropriate to explain the kinematic and emission properties of superluminal components in QSO 3C345, but also strongly supports the traditioal common point-view: superluminal components are physical entities (shocks or plasmoids) participating relativistic motion toward us with acceleration/deceleration along helical trajectories.

We present an updated study on assessing the axes stability of the third generation of the International Celestial Reference Frame (ICRF3) in terms of linear drift and scatter based on the extragalactic source position time series from analyses of archival very long baseline interferometry observations. Our results show that the axes of the ICRF3 are stable at a level of 10 to 20 microseconds of arc, and it does not degrade after the adoption of the ICRF3 when observations from new networks are included. We also show that the commonly used method of deriving the position time series (four-step solution) is robust.

Context. Massive star-formation leads to enrichment with heavy elements of the interstellar medium. On the other hand, the abundance of heavy elements is a key parameter to study the star-formation history of galaxies. Furthermore, the total molecular hydrogen mass, usually determined by converting CO or [C ii] 158 $\mu$m luminosities, depends on the metallicity as well. The excitation of metallicity-sensitive emission lines, however, depends on the gas density of H ii regions, where they arise. Aims. We used spectroscopic observations from SOFIA, Herschel, and Spitzer of the nuclear region of the starburst galaxy NGC 253, as well as photometric observations from GALEX, 2MASS, Spitzer, and Herschel in order to derive physical properties such as the optical depth to correct for extinction, as well as the gas density and metallicity of the central region. Methods. Ratios of the integrated line fluxes of several species were utilised to derive the gas density and metallicity. The [O iii] along with the [S iii] and [N ii] line flux ratios for example, are sensitive to the gas density but nearly independent of the local temperature. As these line ratios trace different gas densities and ionisation states, we examined if these lines may originate from different regions within the observing beam. The ([Ne ii] 13 $\mu$m + [Ne iii] 16 $\mu$m)/Hu $\alpha$ line flux ratio on the other hand, is independent of the depletion onto dust grains but sensitive to the Ne/H abundance ratio and will be used as a tracer for metallicity of the gas. Results. We derived values for gas phase abundances of the most important species, as well as estimates for the optical depth and the gas density of the ionised gas in the nuclear region of NGC 253. We obtained densities of at least two different ionised components $(< 84$ cm$^{-3}$ and $\sim 170 - 212$ cm$^{-3})$ and a metallicity of solar value.

The physics behind the ionization structure of outflows from black holes is yet to be fully understood. Using archival observations with the Chandra\HETG gratings over the past two decades, we measured an absorption measure distribution for a sample of outflows in nine active galaxies (AGNs), namely the dependence of outflow column density, $N_H$, on the ionization parameter, $\xi$. The slope of $\log(N_H)$ vs. $\log\xi$ is found to be between 0.00 and 0.72. We find an anti-correlation between the log of total column density of the outflow and the log of AGN luminosity, and none with the black hole mass and accretion efficiency. A major improvement in the diagnostics of AGN outflows will potentially occur with the launch of the XRISM/Resolve spectrometer. We study the ability of Resolve to reveal the outflow ionization structure by constructing the absorption measure distribution from simulated Resolve spectra, utilizing its superior resolution and effective area. Resolve constrains the column density as well as HETG, but with much shorter observations.

Gaussian processes have been widely used in cosmology to reconstruct cosmological quantities in a model-independent way. However, the validity of the adopted mean function and hyperparameters, and the dependence of the results on the choice have not been well explored. In this paper, we study the effects of the underlying mean function and the hyperparameter selection on the reconstruction of the distance moduli from type Ia supernovae. We show that the choice of an arbitrary mean function affects the reconstruction: a zero mean function leads to unphysical distance moduli and the best-fit LCDM to biased reconstructions. We propose to marginalize over a family of mean functions and over the hyperparameters to effectively remove their impact on the reconstructions. We further explore the validity and consistency of the results considering different kernel functions and show that our method is unbiased.

The next generation of radio telescopes will strive for unprecedented dynamic range across wide fields of view, and direction-dependent gains such as the gain from the primary-beam pattern, or leakage of one Stokes product into another, must be removed from the cleaned images if dynamic range is to reach its full potential. Unfortunately, such processing is extremely computationally intensive, and is made even more challenging by the very large volumes of data that these instruments will generate. Here we describe a new GPU-based imager, aimed primarily at use with the ASKAP telescope, that is capable of generating cleaned, full-polarisation images that include wide-field, primary-beam, and polarisation leakage corrections.

Novel techniques are indispensable to process the flood of data from the new generation of radio telescopes. In particular, the classification of astronomical sources in images is challenging. Morphological classification of radio galaxies could be automated with deep learning models that require large sets of labelled training data. Here, we demonstrate the use of generative models, specifically Wasserstein GANs (wGAN), to generate artificial data for different classes of radio galaxies. Subsequently, we augment the training data with images from our wGAN. We find that a simple fully-connected neural network for classification can be improved significantly by including generated images into the training set.

The InSight mission has measured Mars' seismicity since February 2018 and has allowed to investigate tectonics on another planet. Seismic data shows that most of the widely distributed surface faults are not seismically active, and that seismicity is mostly originating from a single graben structure, the Cerberus Fossae. We show that both major families of marsquakes characterized by low and high frequency content, LF and HF events respectively, are located on central and eastern parts of this graben system. LF hypocenters are located at 15-50 km depth and the spectral character suggests a structurally weak, potentially warm source region consistent with recent volcanic activity at those depths. HF marsquakes occur in the brittle, shallow part of the crust and might originate in fault planes associated with the graben flanks. Estimated magnitudes are between 2.8 and 3.8, resulting in a total seismic moment release within Cerberus Fossae of 1.4-5.6 $\times10^{15}$ Nm/yr, or at least half of the observed value of the entire planet. Our findings confirm that Cerberus Fossae represents a unique tectonic setting shaped by current day volcanic processes, with implications for minimum local heat flow.

CarbON CII line in post-rEionization and ReionizaTiOn (CONCERTO) is a low-resolution spectrometer with an instantaneous field-of-view of 18.6 arcmin, operating in the 130-310 GHz transparent atmospheric window. It is installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5100 m above sea level. The Fourier transform spectrometer (FTS) contains two focal planes hosting a total of 4304 kinetic inductance detectors. The FTS interferometric pattern is recorded on the fly while continuously scanning the sky. One of the goals of CONCERTO is to characterize the large-scale structure of the Universe by observing the integrated emission from unresolved galaxies. This methodology is an innovative technique and is called line intensity mapping. In this paper, we describe the CONCERTO instrument, the effect of the vibration of the FTS beamsplitter, and the status of the CONCERTO main survey.

The X-IFU is the cryogenic spectrometer onboard the future ATHENA X-ray observatory. It is based on a large array of TES microcalorimeters, which works in combination with a Cryogenic AntiCoincidence detector (CryoAC). This is necessary to reduce the particle background level thus enabling part of the mission science goals. Here we present the first joint test of X-IFU TES array and CryoAC Demonstration Models, performed in a FDM setup. We show that it is possible to operate properly both detectors, and we provide a preliminary demonstration of the anti-coincidence capability of the system achieved by the simultaneous detection of cosmic muons.

Far-infrared detectors for future cooled space telescopes require ultra-sensitive detectors with optical noise equivalent powers of order 0.2 aW/\sqrt Hz. This performance has already been demonstrated in arrays of transition edge sensors. A critical step is demonstrating a method of fabrication and assembly that maintains the performance but that is extendable to create large-scale arrays suitable, for example, for application in dispersive spectrometers where it may be advantageous to fabricate the array from smaller sub-arrays. Critical here are the methods of assembly and metrology that maintain the required tolerances on the spatial alignment of the components in order to maintain overall performance. These are discussed and demonstrated.

We developed the functional form of the two-point correlation function under the approximation of fixed particle number density n(bar). We solved the quasi-linear partial differential equation (PDE) through the method of characteristics to obtain the parametric solution for the canonical ensemble. We attempted many functional forms and concluded that the functional form should be such that the two-point correlation function should go to zero as the value of system temperature increases or the separation between the galaxies becomes large. Also, we studied the graphical behavior of the developed two-point correlation function for large values of temperature T and spatial separation r. The behavior of the two-point function was also studied from the temperature measurement of clusters in the redshift range of 0.023 to 0.546.

This review summarizes our current understanding of the outer heliosphere and local interstellar medium (LISM) inferred from observations and modeling of interplanetary Lyman-$\alpha$ emission. The emission is produced by solar Lyman-alpha photons (121.567 nm) backscattered by interstellar H atoms inflowing to the heliosphere from the LISM. Studies of Lyman-alpha radiation determined the parameters of interstellar hydrogen within a few astronomical units from the Sun. The interstellar hydrogen atoms appeared to be decelerated, heated, and shifted compared to the helium atoms. The detected deceleration and heating proved the existence of secondary hydrogen atoms created near the heliopause. This finding supports the discovery of a Hydrogen Wall beyond the heliosphere consisting of heated hydrogen observed in HST/GHRS Lyman-alpha absorption spectra toward nearby stars. The shift of the interstellar hydrogen bulk velocity was the first observational evidence of the global heliosphere asymmetry confirmed later by Voyager in situ measurements. SOHO/SWAN all-sky maps of the backscattered Lyman-alpha intensity identified variations of the solar wind mass flux with heliolatitude and time. In particular, two maxima at mid-latitudes were discovered during solar activity maximum, which Ulysses missed due to its specific trajectory. Finally, Voyager/UVS and New Horizons/Alice UV spectrographs discovered extra-heliospheric Lyman-alpha emission. We review these scientific breakthroughs, outline open science questions, and discuss potential future heliospheric Lyman-alpha experiments.

The rotation of the galactic objects has been seen by asymmetric Doppler shift in the CMB data. Molecular hydrogen clouds at virial temperature may contribute to the galactic halo dark matter and they might be the reason for the observed rotational asymmetry in the galactic halos. We present a method to constrain the parameters of these virial clouds given that they are composed of a single fluid. The method is such that it should be possible to extend it to more than one fluid.

We perform a detailed study of the stellar populations in a sample of massive Fornax dwarf galaxies using a set of newly defined line indices. Using data from the Integral field spectroscopic data, we study abundance ratios of eight dEs with stellar mass ranging from 10$^8$ to 10$^{9.5}$ M$_\odot$ in the Fornax cluster. We present the definitions of a new set of high-resolution Lick-style indices to be used for stellar population studies of unresolved small stellar systems. We identify 23 absorption features and continuum regions, mainly dominated by 12 elements (Na, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Ba and Nd) in the wavelength range 4700 - 5400 \r{A} and characterise them as a function of age, metallicity and alpha element abundance ratios. We analyse eight dEs and interpret the line strengths, measured in our new high resolution system of indices, with the aid of stellar population models with high enough spectral resolution. We obtain abundance ratio proxies for a number of elements that have never been studied before for dwarf ellipticals outside the Local Group. These proxies represent relative deviations from predicted index-strengths of base stellar population models built-up following the abundance pattern of The Galaxy. The abundance proxy trend results are compared to abundance ratios from resolved stars in the Local Group, and indices from integrated light of larger early-type galaxies. We find that all our dwarfs show a pattern of abundance ratios consistent with the disk of the Milky Way, indicative of slow formation in comparison to their high mass counterparts.

The loss of magnetic pressure accompanying the decay of the magnetic field in a magnetar may trigger exothermic electron captures by nuclei in the shallow layers of the stellar crust. Very accurate analytical formulas are obtained for the threshold density and pressure, as well as for the maximum amount of heat that can be possibly released, taking into account the Landau-Rabi quantization of electron motion. These formulas are valid for arbitrary magnetic field strengths, from the weakly quantizing regime to the most extreme situation in which electrons are all confined to the lowest level. Numerical results are also presented based on experimental nuclear data supplemented with predictions from the Brussels-Montreal model HFB-24. This same nuclear model has been already employed to calculate the equation of state in all regions of magnetars.

Despite their relative sparseness, during the recent years it has become more and more clear that extragalactic radio sources (both AGN and star-forming galaxies) constitute an extremely interesting mix of populations, not only because of their intrinsic value, but also for their fundamental role in shaping our Universe the way we see it today. Indeed, radio-active AGN are now thought to be the main players involved in the evolution of massive galaxies and clusters. At the same time, thanks to the possibility of being observed up to very high redshifts, radio galaxies can also provide crucial information on both the star-formation history of our Universe and on its Large-Scale Structure properties and their evolution. In the light of present and forthcoming facilities such as LOFAR, MeerKAT and SKA that will probe the radio sky to unprecedented depths and widths, this review aims at providing the current state of the art on our knowledge of extragalactic radio sources in connection with their hosts, large-scale environments and cosmological context.

M dwarfs remain active over longer timescales than their Sunlike counterparts, with potentially devastating implications for the atmospheres of their planets. However, the age at which fully-convective M dwarfs transition from active and rapidly rotating to quiescent and slowly rotating is poorly understood, as these stars remain rapidly rotating in the oldest clusters that are near enough for a large sample of low-mass M dwarfs to be studied. To constrain the spindown of these low-mass stars, we measure photometric rotation periods for field M dwarfs in wide binary systems, primarily using TESS and MEarth. Our analysis includes M-M pairs, which are coeval but of unknown age, as well as M dwarfs with white dwarf or Sunlike primaries, for which we can estimate ages using techniques like white dwarf cooling curves, gyrochronology, and lithium abundance. We find that the epoch of spindown is strongly dependent on mass. Fully-convective M dwarfs initially spin down slowly, with the population of 0.2--0.3M$_\odot$ rapid rotators evolving from $P_{\rm rot} < 2$ days at 600 Myr to $2 < P_{\rm rot} < 10$ days at 1--3 Gyr before rapidly spinning down to long rotation periods at older ages. However, we also identify some variability in the spindown of fully-convective M dwarfs, with a small number of stars having substantially spun down by 600 Myr. These observations are consistent with models of magnetic morphology-driven spindown, where angular momentum loss is initially inefficient until changes in the magnetic field allow spindown to progress rapidly.

On icy worlds, the ice shell and subsurface ocean form a coupled system -- heat and salinity flux from the ice shell induced by the ice thickness gradient drives circulation in the ocean, and in turn, the heat transport by ocean circulation shapes the ice shell. Therefore, understanding the dependence of the efficiency of ocean heat transport (OHT) on orbital parameters may allow us to predict the ice shell geometry before direct observation is possible, providing useful information for mission design. Inspired by previous works on baroclinic eddies, I first derive scaling laws for the OHT on icy moons, driven by ice topography, and then verify them against high resolution 3D numerical simulations. Using the scaling laws, I am then able to make predictions for the equilibrium ice thickness variation knowing that the ice shell should be close to heat balance. Ice shell on small icy moons (e.g., Enceladus) may develop strong thickness variations between the equator and pole driven by the polar-amplified tidal dissipation in the ice, to the contrary, ice shell on large icy moons (e.g., Europa, Ganymede, Callisto etc.) tends to be flat due to the smoothing effects of the efficient OHT. These predictions are manifested by the different ice evolution pathways simulated for Enceladus and Europa, considering the ice freezing/melting induced by ice dissipation, conductive heat loss and OHT as well as the mass redistribution by ice flow.

Common envelope (CE) evolution is an outstanding open problem in stellar evolution, critical to the formation of compact binaries including gravitational-wave (GW) sources. In the "classical" isolated binary evolution scenario for double compact objects, the CE is usually the second mass transfer phase. Thus, the donor star of the CE is the product of a previous binary interaction, often stable Roche-lobe overflow (RLOF). Because of the accretion of mass during the first RLOF, the main-sequence core of the accretor star grows and is "rejuvenated". This modifies the core-envelope boundary region and decreases significantly the envelope binding energy for the remaining evolution. Comparing accretor stars from self-consistent binary models to stars evolved as single, we demonstrate that the rejuvenation can lower the energy required to eject a CE by $\sim 4 - 58\%$ for both black hole and neutron star progenitors, depending on the evolutionary stage and final orbital separation. Therefore, GW progenitors experiencing a first stable mass transfer may more easily survive subsequent possible CE events and result in possibly wider final separations compared to current predictions. Despite their high mass, our accretors also experience extended "blue loops", which may have observational consequences for low-metallicity stellar populations and asteroseismology.

We analyze Near-Infrared Integral Field Spectrograph (NIFS) observations of the type-2 quasar (QSO2) SDSS J094521.33+173753.2 to investigate its warm molecular and ionized gas kinematics. This QSO2 has a bolometric luminosity of 10$^{45.7}$ erg s$^{-1}$ and a redshift of z = 0.128. The K-band spectra provided by NIFS cover a range of 1.99-2.40 $\mu$m where low-ionization (Pa$\alpha$ and Br$\delta$), high ionization ([S XI]$\lambda$1.920 $\mu$m and [Si~VI]$\lambda$1.963 $\mu$m) and warm molecular lines (from H$_2$ 1-0S(5) to 1-0S(1)) are detected, allowing us to study the multi-phase gas kinematics. Our analysis reveals gas in ordinary rotation in all the emission lines detected and also outflowing gas in the case of the low- and high-ionization emission lines. In the case of the nuclear spectrum, which corresponds to a circular aperture of 0.3\arcsec~(686 pc) in diameter, the warm molecular lines can be characterized using a single Gaussian component of full width at half maximum (FWHM)= 350-400 km s$^{-1}$, while Pa$\alpha$, Br$\delta$, and [Si~VI] are best fitted with two blue-shifted Gaussian components of FWHM$\sim$800 and 1700 km s$^{-1}$, in addition to a narrow component of $\sim$300 km s$^{-1}$. We interpret the blue-shifted broad components as outflowing gas, which reaches the highest velocities, of up to $-$840 km s$^{-1}$, in the south-east direction (PA$\sim$125$^{\circ}$), extending up to a distance of $\sim$3.4 kpc from the nucleus. The ionized outflow has a maximum mass outflow rate of $\dot{\text{{M}}}_{\text{{out, max}}}$=42-51 M$_\odot$ yr$^{-1}$, and its kinetic power represents 0.1$\%$ of the quasar bolometric luminosity.

The Double Asteroid Redirection Test (DART) is a NASA mission intended to crash a projectile on Dimorphos, the secondary component of the binary (65803) Didymos system, to study its orbit deflection. As a consequence of the impact, a dust cloud will be be ejected from the body, potentially forming a transient coma- or comet-like tail on the hours or days following the impact, which might be observed using ground-based instrumentation. Based on the mass and speed of the impactor, and using known scaling laws, the total mass ejected can be roughly estimated. Then, with the aim to provide approximate expected brightness levels of the coma and tail extent and morphology, we have propagated the orbits of the particles ejected by integrating their equation of motion, and have used a Monte Carlo approach to study the evolution of the coma and tail brightness. For typical power-law particle size distribution of index --3.5, with radii r$_{rmin}$=1 $\mu$m and r$_{max}$=1 cm, and ejection speeds near 10 times the escape velocity of Dimorphos, we predict an increase of brightness of $\sim$3 magnitudes right after the impact, and a decay to pre-impact levels some 10 days after. That would be the case if the prevailing ejection mechanism comes from the impact-induced seismic wave. However, if most of the ejecta is released at speeds of the order of $\gtrsim$100 $\mathrm{m\; s^{-1}}$, the observability of the event would reduce to a very short time span, of the order of one day or shorter.

The spectrum of eight-times ionized iron, Fe IX, was studied in the 110-200 {\AA} region. A low inductance vacuum spark and a 3-m grazing incidence spectrograph were used for the excitation and recording of the spectrum. Previous analyses of Fe IX have been greatly extended and partly revised. The numbers of known lines in the 3p^53d - 3p^54f and 3p^53d - 3p^43d^2 transition arrays are extended to 25 and 81, respectively. Most of the identifications of the Fe IX lines from the 3p^53d - 3p^43d^2 transition array in the solar spectrum have been confirmed and several new identifications are suggested.

The Planck mission detected a positive correlation between the intensity ($T$) and $B$-mode polarization of the Galactic thermal dust emission. The $TB$ correlation is a parity-odd signal, whose statistical mean vanishes in models with mirror symmetry. Recent work has shown with strong evidence that local handedness of the misalignment between the dust filaments and the sky-projected magnetic field produces $TB$ signals. However, it remains unclear whether the observed global $TB$ signal is caused by statistical fluctuations of magnetic misalignment angles, or whether some parity-violating physics in the interstellar medium sets a preferred misalignment handedness. The present work aims to make a quantitative statement about how confidently the statistical-fluctuation interpretation is ruled out by filament-based simulations of polarized dust emission. We use the publicly available DUSTFILAMENTS code to simulate the dust emission from filaments whose magnetic misalignment angles are symmetrically randomized, and construct the probability density function of $\xi_{p}$, a weighted sum of $TB$ power spectrum. We find that Planck data has a $\gtrsim 10\sigma$ tension with the simulated $\xi_{p}$ distribution. Our results strongly support that the Galactic filament misalignment has a preferred handedness, whose physical origin is yet to be identified.

Line-intensity mapping (LIM) is an emerging approach to survey the Universe, using relatively low-aperture instruments to scan large portions of the sky and collect the total spectral-line emission from galaxies and the intergalactic medium. Mapping the intensity fluctuations of an array of lines offers a unique opportunity to probe redshifts well beyond the reach of other cosmological observations, access regimes that cannot be explored otherwise, and exploit the enormous potential of cross-correlations with other measurements. This promises to deepen our understanding of various questions related to galaxy formation and evolution, cosmology, and fundamental physics. Here we focus on lines ranging from microwave to optical frequencies, the emission of which is related to star formation in galaxies across cosmic history. Over the next decade, LIM will transition from a pathfinder era of first detections to an early-science era where data from more than a dozen missions will be harvested to yield new insights and discoveries. This review discusses the primary target lines for these missions, describes the different approaches to modeling their intensities and fluctuations, surveys the scientific prospects of their measurement, presents the formalism behind the statistical methods to analyze the data, and motivates the opportunities for synergy with other observables. Our goal is to provide a pedagogical introduction to the field for non-experts, as well as to serve as a comprehensive reference for specialists.

Double white dwarf (DWD) systems are unique among gravitational-wave sources because their evolution is governed not just by general relativity, but also by mass transfer and tides. While the black hole and neutron star binaries observed with ground-based gravitational-wave detectors are driven to inspiral due to the emission of gravitational radiation - manifesting as a ``chirp''-like gravitational-wave signal - the astrophysical processes at work in DWDs can cause the inspiral to stall and even reverse into an outspiral. The dynamics of the DWD outspiral thus encode information about tides, which tell us about the behaviour of electron-degenerate matter. We carry out a population study to determine the effect of the strength of tides on the distributions of the DWD binary parameters that the Laser Interferometer Space Antenna (LISA) will be able to constrain. We find that the strength of tidal coupling leaves a unique signature in the distribution of gravitational-wave frequencies and frequency derivatives for detectably mass transferring DWD systems. By measuring the population properties of DWDs, LISA will be able to probe the behavior of electron-degenerate matter.

On 11 February 2016, the LIGO and Virgo scientific collaborations announced the first direct detection of gravitational waves, a signal caught by the LIGO interferometers on 14 September 2015, and produced by the coalescence of two stellar-mass black holes. The discovery represented the beginning of an entirely new way to investigate the Universe. The latest gravitational-wave catalog by LIGO, Virgo and KAGRA brings the total number of gravitational-wave events to 90, and the count is expected to significantly increase in the next years, when additional ground-based and space-born interferometers will be operational. From the theoretical point of view, we have only fuzzy ideas about where the detected events came from, and the answers to most of the five Ws and How for the astrophysics of compact binary coalescences are still unknown. In this work, we review our current knowledge and uncertainties on the astrophysical processes behind merging compact-object binaries. Furthermore, we discuss the astrophysical lessons learned through the latest gravitational-wave detections, paying specific attention to the theoretical challenges coming from exceptional events (e.g., GW190521 and GW190814).

The Cosmic Infrared Background (CIB) traces the emission of star-forming galaxies throughout all cosmic epochs. Breaking down the contribution from galaxies at different redshifts to the observed CIB maps would allow us to probe the history of star formation. In this paper, we cross-correlate maps of the CIB with galaxy samples covering the range $z\lesssim2$ to measure the bias-weighted star-formation rate (SFR) density $\langle b\rho_{\rm SFR}\rangle$ as a function of time in a model independent way. This quantity is complementary to direct measurements of the SFR density $\rho_{\rm SFR}$, giving a higher weight to more massive haloes, and thus provides additional information to constrain the physical properties of star formation. Using cross-correlations of the CIB with galaxies from the DESI Legacy Survey and the extended Baryon Oscillation Spectroscopic Survey, we obtain high signal-to-noise ratio measurements of $\langle b\rho_{\rm SFR}\rangle$, which we then use to place constraints on halo-based models of the star-formation history. We fit halo-based SFR models to our data and compare the recovered $\rho_{\rm SFR}$ with direct measurements of this quantity. We find a qualitatively good agreement between both independent datasets, although the details depend on the specific halo model assumed. This constitutes a useful robustness test for the physical interpretation of the CIB, and reinforces the role of CIB maps as valuable astrophysical probes of the large-scale structure. We report our measurements of $\langle b\rho_{\rm SFR}\rangle$ as well as a thorough account of their statistical uncertainties, which can be used to constrain star formation models in combination with other data.

This study explores the link between the [OIII]88mu emission, a well-known tracer of HII regions, and 24mu continuum, often used to trace warm dust in the ionized phases of galaxies. We investigate the local conditions driving the relation between those tracers in the Magellanic Clouds, comparing observations with Cloudy models consisting of an HII region plus a photodissociation region (PDR) component, varying the stellar age, the initial density (at the illuminated edge of the cloud), and the ionization parameter. We introduce a new parameter, cPDR, to quantify the proportion of emission arising from PDRs and that with an origin in HII regions along each line of sight. We use the ratio ([CII]+[OI])/[OIII] as a proxy for the ratio of PDR versus HII region emission, and compare it to [OIII]/24mu. The use of [OIII]/24mu and [OIII]/70mu together allows us to constrain the models most efficiently. We find a correlation over at least 3 orders of magnitude in [OIII]88mu and 24mu continuum in spatially resolved maps of the Magellanic Cloud regions as well as unresolved galaxy-wide low metallicity galaxies of the Dwarf Galaxy Survey. Most of the regions have low proportions of PDRs along the lines of sight (< 12%), while a limited area of some of the mapped regions can reach 30 to 50%. For most lines of sight within the star-forming regions we have studied in the Magellanic Clouds, HII regions are the dominant phase. We propose the use of the correlation between the [OIII]88mu and 24mu continuum as a new predictive tool to estimate, for example, the [OIII]88mu emission when the 24mu continuum is available or inversely. This can be useful to prepare for ALMA observations of [OIII]88mu in high-z galaxies. This simple and novel method may also provide a way to disentangle different phases along the line of sight, when other 3D information is not available.

Forward modeling approaches in cosmology have made it possible to reconstruct the initial conditions at the beginning of the Universe from the observed survey data. However the high dimensionality of the parameter space still poses a challenge to explore the full posterior, with traditional algorithms such as Hamiltonian Monte Carlo (HMC) being computationally inefficient due to generating correlated samples and the performance of variational inference being highly dependent on the choice of divergence (loss) function. Here we develop a hybrid scheme, called variational self-boosted sampling (VBS) to mitigate the drawbacks of both these algorithms by learning a variational approximation for the proposal distribution of Monte Carlo sampling and combine it with HMC. The variational distribution is parameterized as a normalizing flow and learnt with samples generated on the fly, while proposals drawn from it reduce auto-correlation length in MCMC chains. Our normalizing flow uses Fourier space convolutions and element-wise operations to scale to high dimensions. We show that after a short initial warm-up and training phase, VBS generates better quality of samples than simple VI approaches and reduces the correlation length in the sampling phase by a factor of 10-50 over using only HMC to explore the posterior of initial conditions in 64$^3$ and 128$^3$ dimensional problems, with larger gains for high signal-to-noise data observations.

We set constraints on the dark matter halo mass and concentration of ~22,000 individual galaxies visible both in HI (from the ALFALFA survey) and optical light (from the SDSS). This is achieved by combining two Bayesian models, one for the HI line width as a function of the stellar and neutral hydrogen mass distributions in a galaxy using kinematic modelling, and the other for the galaxy's total baryonic mass using the technique of inverse subhalo abundance matching. We hence quantify the constraining power on halo properties of spectroscopic and photometric observations, and assess their consistency. We find good agreement between the two sets of posteriors, although there is a sizeable population of low-line width galaxies that favour significantly smaller dynamical masses than expected from abundance matching (especially for cuspy halo profiles). Abundance matching provides significantly more stringent bounds on halo properties than the HI line width, even with a mass--concentration prior included, although combining the two provides a mean gain of 40% for the sample when fitting an NFW profile. We also use our kinematic posteriors to construct a baryonic mass--halo mass relation, which we find to be near power-law, and with a somewhat shallower slope than expected from abundance matching. Our method demonstrates the potential of combining photometric and spectroscopic observations to precisely map out the dark matter distribution at the galaxy scale using upcoming HI surveys such as the SKA.

We investigate how much can be learnt about four types of primordial non-Gaussianity (PNG) from small-scale measurements of the halo field. Using the \textsc{quijote-png} simulations, we quantify the information content accessible with measurements of the halo power spectrum monopole and quadrupole, the matter power spectrum, the halo-matter cross spectrum and the halo bispectrum monopole. This analysis is the first to include small, non-linear scales, up to $k_\mathrm{max}=0.5 \mathrm{h/Mpc}$, and to explore whether these scales can break degeneracies with cosmological and nuisance parameters making use of thousands of N-body simulations. For \emph{local} PNG, measurements of the scale dependent bias effect from the power spectrum using sample variance cancellation provide significantly tighter constraints than measurements of the halo bispectrum. In this case measurements of the small scales add minimal additional constraining power. In contrast, the information on \emph{equilateral} and \emph{orthogonal} PNG is primarily accessible through the bispectrum. For these shapes, small scale measurements increase the constraining power of the halo bispectrum by up to $\times4$, though the addition of scales beyond $k\approx 0.3 \mathrm{h/Mpc}$ improves constraints largely through reducing degeneracies between PNG and the other parameters. These degeneracies are even more powerfully mitigated through combining power spectrum and bispectrum measurements. However even with combined measurements and small scale information, \emph{equilateral} non-Gaussianity remains highly degenerate with $\sigma_8$ and our bias model.

The Beam Expander Testing X-ray facility (BEaTriX) is a unique X-ray apparatus now operated at the Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Brera (OAB), in Merate, Italy. It has been specifically designed to measure the point spread function (PSF) and the effective area (EA) of mirror modules (MM) of the Advanced Telescope for High-ENergy Astrophysics (ATHENA) X-ray telescope, based on the silicon pore optics (SPO) technology, for acceptance before integration into the mirror assembly. To this end, BEaTriX generates a broad, uniform, monochromatic, and collimated X-ray beam at 4.51 keV [...] In BEaTriX, a micro-focus X-ray source with titanium anode is placed in the focus of a paraboloidal mirror, which generates a parallel beam. A crystal monochromator selects the 4.51 keV line, which is expanded to the final size by a crystal asymmetrically cut with respect to the crystalline planes. [...] After characterization, the BEaTriX beam has the nominal dimensions of 60 mm x 170 mm, with a vertical divergence of 1.65 arcsec and an horizontal divergence varying between 2.7 and 3.45 arcsec, depending on the monochromator setting on either high collimation or high intensity. The flux per area unit varies from 10 to 50 photons/s/cm2 from one configuration to another. The BEaTriX beam performance was tested using an SPO MM, whose entrance pupil was fully illuminated by the expanded beam, and its focus was directly imaged onto the camera. The first light test returned a PSF and an EA in full agreement with the expectations. As of today, the 4.51 keV beamline of BEaTriX is operational and can characterize modular X-ray optics, measuring their PSF and EA with a typical exposure of 30 minutes. [...] We expect BEaTriX to be a crucial facility for the functional test of modular X-ray optics, such as the SPO MMs for ATHENA.

We review the peculiarities that make neutrino a very special cosmic messenger in high-energy astrophysics, and, in particular, to provide possible indications of deviations from special relativity, as it is suggested theoretically by quantum gravity models. In this respect, we examine the effects that one could expect in the production, propagation, and detection of neutrinos, not only in the well-studied scenario of Lorentz Invariance Violation, but also in models which maintain, but deform, the relativity principle, such as those considered in the framework of Doubly Special Relativity. We discuss the challenges and the promising future prospects offered by this phenomenological window to physics beyond special relativity.

It is by now well established that charged rotating Kerr-Newman black holes can support bound-state charged matter configurations which are made of minimally coupled massive scalar fields. We here prove that the externally supported stationary charged scalar configurations {\it cannot} be arbitrarily compact. In particular, for linearized charged massive scalar fields supported by charged rotating near-extremal Kerr-Newman black holes, we derive the remarkably compact lower bound $(r_{\text{field}}-r_+)/(r_+-r_-)>1/s^2$ on the effective lengths of the external charged scalar `clouds' [here $r_{\text{field}}$ is the radial peak location of the stationary scalar configuration, and $\{s\equiv J/M^2, r_{\pm}\}$ are respectively the dimensionless angular momentum and the horizon radii of the central supporting Kerr-Newman black hole]. Remarkably, this lower bound is universal in the sense that it is independent of the physical parameters (proper mass, electric charge, and angular momentum) of the supported charged scalar fields.

In this paper, we suggest a framework for cosmology based on gravitational effective field theories with a negative fundamental cosmological constant, which may exhibit accelerated expansion due to the positive potential energy of rolling scalar fields. The framework postulates an exact time-reversal symmetry of the quantum state (with a time-symmetric big bang / big crunch background cosmology) and an analyticity property that relates cosmological observables to observables in a Euclidean gravitational theory defined with a pair of asymptotically Anti-de Sitter (AdS) planar boundaries. We propose a microscopic definition for this Euclidean theory using holography, so the model is UV complete. While it is not yet clear whether the framework can give realistic predictions, it has the potential to resolve various naturalness puzzles without the need for inflation. This is a shorter version of arXiv:2203.11220, emphasizing the effective field theory point of view.

We revisit the predictions for the duration of the inflationary phase after the bounce in Loop Quantum Cosmology. We present our analysis for different classes of inflationary potentials that include the monomial power-law chaotic type of potentials, the Starobinsky and the Higgs-like symmetry breaking potential with different values for the vacuum expectation value. Our set up can easily be extended to other forms of primordial potentials than the ones we have considered. Independently on the details of the contracting phase, if the dynamics starts sufficiently in the far past, the kinetic energy will come to dominate at the bounce, uniquely determining the amplitude of the inflaton at this moment. This will be the initial condition for the further evolution that will provide us with results for the number of {\it e}-folds from the bounce to the beginning of the accelerated inflationary regime and the subsequent duration of inflation. We also discuss under which conditions each model considered could lead to observable signatures on the spectrum of the Cosmic Microwave Background (CMB), or, else, be excluded for not predicting a sufficient amount of accelerated expansion. A first analysis is performed considering the standard value for the Barbero-Immirzi parameter, $\gamma \simeq 0.2375$, which is obtained from black hole entropy calculations. In a second analysis, we consider the possibility of varying the value of this parameter, which is motivated by the fact that the Barbero-Immirzi parameter can be considered a free parameter of the underlying quantum theory in the context of Loop Quantum Gravity. {}From this analysis, we obtain a lower limit for this parameter by requiring the minimum amount of inflationary expansion that makes the model consistent with the CMB observations.

In this contribution I review the connection between compact stars and high-baryon density matter, focusing on astrophysical observables for deconfinement to quark matter. I discuss modern ingredients, repositories, and constraints for the neutron-star equations of state. Finally, I draw comparisons between dense and hot matter created in neutron-star mergers and heavy-ion collisions, and the possibility of quantitatively establishing a link between them.

Launching large (> 1 g) well-characterized projectiles to velocities beyond 10 km/s is of interest for a number of scientific fields but is beyond the reach of current hypervelocity launcher technology. This paper reports the development of an explosively driven light-gas gun that has demonstrated the ability to launch 8 mm diameter, 0.36 g magnesium projectiles to 10.4 km/s. The implosion-driven launcher (IDL) uses the linear implosion of a pressurized tube to shock-compress helium gas to a pressure of \SI{5}{\giga\pascal}, which then expands to propel a projectile to hypervelocity. The launch cycle of the IDL is explored with the use of down-bore velocimetry experiments and a quasi-one-dimensional internal ballistics solver. A detailed overview of the design of the 8 mm launcher is presented, with an emphasis on the unique considerations which arise from the explosively driven propellant compression and the resulting extreme pressures and temperatures. The high average driving pressure results in a launcher that is compact, with a total length typically less than a meter. The possibility to scale the design to larger projectile sizes (25 mm diameter) is demonstrated. Finally, concepts for a modified launch cycle which may allow the IDL to reach significantly greater projectile velocities are explored conceptually and with preliminary experiments.

About half of the elements beyond iron are synthesized in stars by rapid-neutron capture process (r-process). The stellar environment provides very high neutron flux in a short time ($\sim$ seconds) which is conducive for the creation of progressively neutron-rich nuclei till the waiting point is reached after which no further neutron capture reactions proceed. At this point such extremely neutron-rich nuclei become stable via $\beta^-$ decay. A detailed understanding of the r-process remains illusive. In the present work, we explore the radiative neutron-capture (n,$\gamma$) cross sections and reaction rates around the r-process peak near mass number eighty. The inherent uncertainties remain large in some cases, particularly in case of neutron-rich nuclei. When the low-energy enhancement exists, it results in significant increase in the reaction rate for neutron-capture.

The sub-barrier fusion hindrance has been observed in the domain of very low energies of astrophysical relevance. This phenomenon can be analyzed effectively using an uncomplicated straightforward elegant mathematical formula gleaned presuming diffused barrier with a Gaussian distribution. The mathematical formula for cross section of nuclear fusion reaction has been obtained by folding together a Gaussian function representing the fusion barrier height distribution and the expression for classical cross section of fusion assuming a fixed barrier. The variation of fusion cross section as a function of energy, thus obtained, describes well the existing data on sub-barrier heavy-ion fusion for lighter systems of astrophysical interest. Employing this elegant formula, cross sections of interacting nuclei from $^{16}$O + $^{18}$O to $^{12}$C + $^{198}$Pt, all of which were measured down to $<$ 10 $\mu$b have been analyzed. The agreement of the present analysis with the measured values is comparable, if not better, than those calculated from more sophisticated calculations. The three parameters of this formula varies rather smoothly implying its usage in estimating the excitation function or extrapolating cross sections for pairs of interacting nuclei which are yet to be measured. Possible effects of neutron transfers on the hindrance in heavy-ion fusion have been explored.

General relativity offers a classical description to gravitation and spacetime, and is a cornerstone for modern physics. It has passed a number of empirical tests with flying colours, mostly in the weak-gravity regimes, but nowadays also in the strong-gravity regimes. Radio pulsars provide one of the earliest extrasolar laboratories for gravity tests. They, in possession of strongly self-gravitating bodies, i.e. neutron stars, are playing a unique role in the studies of strong-field gravity. Radio timing of binary pulsars enables very precise measurements of system parameters, and the pulsar timing technology is extremely sensitive to various types of changes in the orbital dynamics. If an alternative gravity theory causes modifications to binary orbital evolution with respect to general relativity, the theory prediction can be confronted with timing results. In this chapter, we review the basic concepts in using radio pulsars for strong-field gravity tests, with the aid of some recent examples in this regard, including tests of gravitational dipolar radiation, massive gravity theories, and the strong equivalence principle. With more sensitive radio telescopes coming online, pulsars are to provide even more dedicated tests of strong gravity in the near future.

Nuclear systems under constraints, with high degrees of symmetries and/or collectivities may be considered as moving effectively in spaces with reduced spatial dimensions. We first derive analytical expressions for the nucleon specific energy $E_0(\rho)$, pressure $P_0(\rho)$, incompressibility coefficient $K_0(\rho)$ and skewness coefficient $J_0(\rho)$ of symmetric nucleonic matter (SNM), the quadratic symmetry energy $E_{\rm{sym}}(\rho)$, its slope parameter $L(\rho)$ and curvature coefficient $K_{\rm{sym}}(\rho)$ as well as the fourth-order symmetry energy $E_{\rm{sym,4}}(\rho)$ of neutron-rich matter in general $d$ spatial dimensions (abbreviated as "$d$D") in terms of the isoscalar and isovector parts of the isospin-dependent single-nucleon potential according to the generalized Hugenholtz-Van Hove (HVH) theorem. The equation of state (EOS) of nuclear matter in $d$D can be linked to that in the conventional 3-dimensional (3D) space by the $\epsilon$-expansion which is a perturbative approach successfully used previously in treating second-order phase transitions and related critical phenomena and more recently in studying the EOS of cold atoms. The $\epsilon$-expansion of nuclear EOS in $d$D based on a reference dimension $d_{\rm{f}}=d-\epsilon$ is shown to be effective with $-1\lesssim\epsilon\lesssim1$ starting from $1\lesssim d_{\rm{f}}\lesssim3$ in comparison with the exact expressions derived using the HVH theorem. Moreover, the EOS of SNM (with/without considering its potential part) is found to be reduced (enhanced) in lower (higher) dimensions, indicating in particular that the many-nucleon system tends to be deeper bounded but saturate at higher densities in spaces with lower dimensions. The links between the EOSs in 3D and $d$D spaces from the $\epsilon$-expansion provide new perspectives to the EOS of neutron-rich matter.

An ambitious goal of the astrophysical community is not only to constrain the equation of state (EOS) of neutron star (NS) matter by confronting it with astrophysics observations, but ultimately also to infer the NS composition. Nevertheless, the composition of the NS core is likely to remain uncertain unless we have an accurate determination of the nuclear symmetry energy at supra saturation density ($\rho>\rho_0$). We investigate how the nucleonic direct Urca (dUrca) processes can be used as an effective probe to constraint the high density nuclear symmetry energy. A large number of minimally constrained EOSs has been constructed by applying a Bayesian approach to study the correlations of the symmetry energy at different densities with a few selected properties of a NS. The nuclear symmetry energy above the baryon density 0.5 fm$^{-3}$ ($\sim 3 \rho_0$) is found to be strongly correlated with NS mass at which the onset of nucleonic dUrca neutrino cooling takes place in the core. This allows us to constrain the high density behavior of nuclear symmetry energy within narrow bounds. {The pure neutron matter pressure constraint from chiral effective field theory rules out the onset of nucleonic dUrca in stars with a mass $\lesssim$ 1.4 $M_\odot$.} The onset of dUrca inside 1.6 M$_\odot$ to 1.8 M$_\odot$ NS implies a slope of the symmetry energy $L$ at $\sim 2.5~\rho_0$, respectively, between 54 and 48 MeV.