Papers for Monday, Apr 25 2022

Nearly a hundred stellar streams have been found to date around the Milky Way and the number keeps growing at an ever faster pace. Here we present the \galstreams\ library, a compendium of angular position, distance, proper motion and radial velocity tracks for nearly a hundred (\Nunique) Galactic stellar streams. The information published in the literature has been collated and homogenised in a consistent format and used to provide a set of features uniformly computed throughout the library: e.g. stream length, end points, mean pole, stream's coordinate frame, polygon footprint, and pole and angular momentum tracks. We also use the information compiled to analyse the distribution of several observables across the library and to assess where the main deficiencies are found in the characterisation of individual stellar streams, as a resource for future follow-up efforts. The library is intended to facilitate keeping track of new discoveries and to encourage the use of automated methods to characterise and study the ensemble of known stellar streams by serving as a starting point. The library is publicly available as a Python package and served at the galstreams GitHub repository.

Accretion at sustained or episodic super-Eddington (SE) rates has been proposed as a pathway to grow efficiently light seeds produced by Pop-III stars. We investigate if SE accretion can be sustained onto a black hole (BH) with $M_{\rm BH} \sim 10^3M_{\odot}$ in the centre of a gas-rich proto-galaxy at $z=15$. We perform high-resolution smoothed-particle hydrodynamical simulations, including two different sub-grid models for SE accretion, one based on the slim disc paradigm, and one inspired by recent radiation-magnetohydrodynamical simulations by Jiang and collaborators. Radiative feedback has the form of a thermal dump to surrounding gas particles, with the radiative efficiency being set according to the different SE accretion models. We find that, in all simulations, supernova feedback rapidly quenches accretion after $\sim1Myr$, irrespective of the sub-grid model used for accretion, because it drives winds that evacuate the gas in the inner disc. Quenching is stronger in the model based on the simulations of Jiang and collaborators relative to the slim disc model because of its higher radiative efficiency. The SE growth phase is always very brief, lasting a few $10^5$yr. In the most optimistic case, the BH reaches $\sim$10$^4M_{\odot}$. We extrapolate the final BH masses from $z=15$ to $z\sim6$, assuming subsequent galaxy mergers will replenish the gas reservoir and trigger new cycles of SE accretion. We find that at most BH seeds would grow to $\sim$10$^6M_{\odot}$, comparable to the mass of massive BHs in spiral galaxies such as the Milky Way, but falling short of the mass of the high-redshift quasars.

Understanding the connections between galaxy stellar mass, star formation rate, and dark matter halo mass represents a key goal of the theory of galaxy formation. Cosmological simulations that include hydrodynamics, physical treatments of star formation, feedback from supernovae, and the radiative transfer of ionizing photons can capture the processes relevant for establishing these connections. The complexity of these physics can prove difficult to disentangle and obfuscate how mass-dependent trends in the galaxy population originate. Here, we train a machine learning method called Explainable Boosting Machines (EBMs) to infer how the stellar mass and star formation rate of nearly 6 million galaxies simulated by the Cosmic Reionization on Computers (CROC) project depend on the physical properties of halo mass, the peak circular velocity of the galaxy during its formation history $v_\mathrm{peak}$, cosmic environment, and redshift. The resulting EBM models reveal the relative importance of these properties in setting galaxy stellar mass and star formation rate, with $v_\mathrm{peak}$ providing the most dominant contribution. Environmental properties provide substantial improvements for modeling the stellar mass and star formation rate in only $\lesssim10\%$ of the simulated galaxies. We also provide alternative formulations of EBM models that enable low-resolution simulations, which cannot track the interior structure of dark matter halos, to predict the stellar mass and star formation rate of galaxies computed by high-resolution simulations with detailed baryonic physics.

We use the IllustrisTNG suite of cosmological simulations to measure intrinsic alignment (IA) bispectra of dark matter subhalos between redshifts 0 and 1. We decompose the intrinsic shear field into E- and B-modes and find that the bispectra $B_{\delta\delta\mathrm{E}}$ and $B_{\delta\mathrm{EE}}$, between the matter overdensity field, $\delta$, and the E-mode field, are detected with high significance. We also model the IA bispectra analytically using a method consistent with the two-point non-linear alignment model. We use this model and the simulation measurements to infer the intrinsic alignment amplitude $A_\mathrm{IA}$ and find that values of $A_\mathrm{IA}$ obtained from IA power spectra and bispectra agree well at scales up to $k_\mathrm{max}= 2 \, h \mathrm{Mpc}^{-1}$, for example at $z=1$ $A_\mathrm{IA} = 2.13 \pm$ 0.02 from the cross power spectrum between the matter overdensity and E-mode fields and $A_\mathrm{IA} =2.11 \pm$ 0.03 from $B_{\delta\delta \mathrm{E}}$. This demonstrates that a single physically motivated model can jointly model two-point and three-point statistics of intrinsic alignments, thus enabling a cleaner separation between intrinsic alignments and cosmological weak lensing signals.

The emissivity of the accretion flow is a key parameter affecting the shape of both the energy and variability power spectrum of AGN. We explore the energy-dependence of the power spectrum for five AGN, across the XMM-Newton bandpass, and across the 0.01-1 mHz frequency range, finding a ubiquitous flattening of the power spectrum towards higher energies. We develop a framework to explore this behaviour and thereby extract the energy dependence of the emissivity assuming a simple disc-like geometry for the inflow. We find that the emissivity ranges from R^-2 at energies around the soft excess and increases to R^-4 or steeper above ~4-6 keV. We describe the changing emissivity index with a linear function in energy, finding the best-fitting slopes to vary between AGN. We attempt to correlate the slope of the linear function against key AGN parameters but, as yet, the sample size is too small to confirm hints of a correlation with Eddington ratio.

We present a formalism for jointly fitting pre- and post-reconstruction redshift-space clustering (RSD) and baryon acoustic oscillations (BAO) plus gravitational lensing (of the CMB) that works directly with the observed 2-point statistics. The formalism is based upon (effective) Lagrangian perturbation theory and a Lagrangian bias expansion, which models RSD, BAO and galaxy-lensing cross correlations within a consistent dynamical framework. As an example we present an analysis of clustering measured by the Baryon Oscillation Spectroscopic Survey in combination with CMB lensing measured by Planck. The post-reconstruction BAO strongly constrains the distance-redshift relation, the full-shape redshift-space clustering constrains the matter density and growth rate, and CMB lensing constrains the clustering amplitude. Using only the redshift space data we obtain $\Omega_\mathrm{m} = 0.303\pm 0.008$, $H_0 = 69.21\pm 0.78$ and $\sigma_8 = 0.743\pm 0.043$. The addition of lensing information, even when restricted to the Northern Galactic Cap, improves constraints to $\Omega_m = 0.300 \pm 0.008$, $H_0 = 69.21 \pm 0.77$ and $\sigma_8 = 0.707 \pm 0.035$, in tension with CMB and cosmic shear constraints. The combination of $\Omega_m$ and $H_0$ are consistent with Planck, though their constraints derive mostly from redshift-space clustering. The low $\sigma_8$ value are driven by cross correlations with CMB lensing in the low redshift bin ($z\simeq 0.38$) and at large angular scales, which show a $20\%$ deficit compared to expectations from galaxy clustering alone. We conduct several systematics tests on the data and find none that could fully explain these tensions.

The hadron-quark phase transition in quantum chromodyanmics has been suggested as an alternative explosion mechanism for core-collapse supernovae. We study the impact of three different hadron-quark equations of state (EoS) with first-order (DD2F, STOF-B145) and second-order (CMF) phase transitions on supernova dynamics by performing 97 simulations for solar- and zero-metallicity progenitors in the range of $14\texttt{-}100\,\text{M}_\odot$. We find explosions only for two low-compactness models ($14 \text{M}_\odot$ and $16\,\text{M}_\odot$) with the DD2F EoS, both with low explosion energies of $\mathord{\sim}10^{50}\,\mathrm{erg}$. These weak explosions are characterised by a neutrino signal with several mini-bursts in the explosion phase due to complex reverse shock dynamics, in addition to the typical second neutrino burst for phase-transition driven explosions. The nucleosynthesis shows significant overproduction of nuclei such as $^{90}\mathrm{Zr}$ for the $14\,\text{M}_\odot$ zero-metallicity model and $^{94}\mathrm{Zr}$ for the $16\,\text{M}_\odot$ solar-metallicity model, but the overproduction factors are not large enough to place constraints on the occurrence of such explosions. Several other low-compactness models using the DD2F EoS and two high-compactness models using the STOS EoS end up as failed explosions and emit a second neutrino burst. For the CMF EoS, the phase transition never leads to a second bounce and explosion. For all three EoS, inverted convection occurs deep in the core of the proto-compact star due to anomalous behaviour of thermodynamic derivatives in the mixed phase, which heats the core to entropies up to $4k_\text{B}/\text{baryon}$ and may have a distinctive gravitational wave signature, also for a second-order phase transition.

Weak gravitational lensing shear could be measured far more precisely if information about unlensed attributes of source galaxies were available. Disk galaxy velocity fields supply such information, at least in principle, with idealized models predicting orders of magnitude more Fisher information when velocity field observations are used to complement images. To test the level at which realistic features of disk galaxies (warps, bars, spiral arms, and other substructure) inject noise or bias into such shear measurements, we fit an idealized disk model, including shear, to unsheared galaxies in the Illustris TNG simulation. The inferred shear thus indicates the extent to which unmodeled galaxy features inject noise and bias. We find that $\gamma_+$, the component of shear parallel to the galaxy's first principal axis, is highly biased and noisy because disks display a range of intrinsic axis ratios from 0.8-1. The other shear component, $\gamma_\times$, shows little bias and is well-described by a double Gaussian distribution with central core scatter $\sigma_{\text{core}} \approx$ 0.03, with low-amplitude, broad wings. This is the first measurement of the natural noise floor in the proposed velocity field lensing technique. We conclude that the technique will achieve impressive precision gains for measurements of $\gamma_\times$, but little gain for measurements of $\gamma_+$.

We present a study of photometric flares on 154 low-mass ($\leq 0.2 \textrm{M}_{\odot}$) objects observed by the SPECULOOS-South Observatory from 1st June 2018 to 23rd March 2020. In this sample we identify 85 flaring objects, ranging in spectral type from M4 to L0. We detect 234 flares in this sample, with energies between $10^{29.2}$ and $10^{32.7}$ erg, using both automated and manual methods. With this work, we present the largest photometric sample of flares on late-M and ultra-cool dwarfs to date. By extending previous M dwarf flare studies into the ultra-cool regime, we find M5-M7 stars are more likely to flare than both earlier, and later, M dwarfs. By performing artificial flare injection-recovery tests we demonstrate that we can detect a significant proportion of flares down to an amplitude of 1 per cent, and we are most sensitive to flares on the coolest stars. Our results reveal an absence of high-energy flares on the reddest dwarfs. To probe the relations between rotation and activity for fully convective stars, we extract rotation periods for fast rotators and lower-bound period estimates of slow rotators. These rotation periods span from 2.2 hours to 65 days, and we find that the proportion of flaring stars increases for the very fastest rotators. Finally, we discuss the impact of our flare sample on planets orbiting ultra-cool stars. As stars become cooler, they flare less frequently; therefore, it is unlikely that planets around the very reddest dwarfs would enter the `abiogenesis' zone or drive visible-light photosynthesis through flares alone.

A problem of determining attainable landing sites on the surface of Venus is an essential part of the Venera-D project aimed to explore the planet using a lander. This problem appears due to the inability for the descent module to land at any point on the surface of Venus because of the short duration of the launch window (about 2 weeks from the optimal launch date), as well as restrictions on the maximum permissible overload. An additional factor affecting the reduction of attainable landing sites is the low angular velocity of Venus own rotation. This study proposes a new approach to expand the attainable landing areas. The approach is based on the use of the gravitational field of Venus to transfer the spacecraft to an orbit resonant to the Venusian one with a ratio of periods of 1:1. All the simulations were performed at the patched conic approximation. As an example, we considered a flight to Venus at launch in 2029 or 2031. For both cases maps of attainable landing areas on the surface were constructed. It has been demonstrated that there is always at least one launch date within the launch window, allowing the spacecraft to reach almost any point on the surface of Venus. It is shown that the application of the proposed approach makes it possible to achieve a significant expansion of the attainable landing areas (over 70\% of the surface) and, in some cases, provide access to any point on the surface of Venus. However, the price of this advantage is an increase in the flight duration by one Venusian year.

We present a study on the stellar populations and stellar ages of sub-sample of far-infrared AGN and non-AGN green valley analysed in Mahoro et al. (2017,2019) at 0.6 < z < 1.0 using the data from the COSMOS field. We used long-slit spectroscopy and derived stellar populations and stellar ages using the stellar population synthesis code "STARLIGHT" and analysed the available Lick/IDS indices, such as Dn4000 and $\rm{H\delta_{A}}$. We find that both FIR AGN and non-AGN green valley galaxies are dominated by intermediate stellar populations 67 % and 53 %, respectively. The median stellar ages for AGN and non-AGN are log t = 8.5 [yr] and log t = 8.4 [yr], respectively. We found that majority of our sources (62 % of AGN and 66 % non-AGN) could have experienced bursts and continuous star formation. In addition, most of our FIR AGN (38 %) compared to FIR non-AGN (27 %) might have experienced a burst of SF more than 0.1 Gyr ago. We also found that our FIR AGN and non-AGN green valley galaxies have similar quenching time-scales of ~ 70 Myr. Therefore, the results obtained here are in line with our previous results where we do not find that our sample of FIR AGN in the green valley shows signs of negative AGN feedback, as has been suggested previously in optical studies.

In this Letter we present the analysis of multi-band public data and high sensitivity EVN and e-MERLIN follow-up observations of the candidate host galaxy of GRB 200716C, namely J1304+2938. GRB 200716C is a long-duration $\gamma$-ray burst (GRB), which surprisingly lies among the short-duration GRBs in the E$_{iso}$-E$_{p,z}$ Amati relation. Because of this property and the presence of two peaks in the $\gamma$-ray light curve, it has been recently suggested that GRB 200716C might be a short-GRB gravitationally lensed by an intermediate-mass black hole (IMBH) hosted by J1304+2938 at z = 0.341. While no detections of the afterglow have been reported in radio hitherto, we present here the discovery of significant emission in survey data between 130 MHz and 3 GHz, together with the results of deep, dedicated high-angular-resolution observations carried out with EVN+e-MERLIN, which do not reveal any significant emission down to the $\sim$10 uJy beam$^{-1}$ level. We associate the radio emission to J1304+2938, and we derive a luminosity larger than (2.9$\pm$0.4) $\times$ 10$^{30}$ erg s$^{-1}$ Hz$^{-1}$: if GRB 200716C belongs to J1304+2938, the latter would be one of the brightest host galaxy detected so far in the radio. As a matter of fact, altogether the properties of J1304+2938 are consistent with a highly star forming galaxy (SFR > 186 M$_{\odot}$ yr$^{-1}$), which is the typical environment expected for long-GRBs. Conversely, neither the public data nor our VLBI observations can confirm or rule out the presence of an IMBH acting as a (milli-)lens, and thus the nature of the burst still remains unknown.

The measurements of expansion rate $H(z)$ and the growth rate $f\sigma_8(z)$ describe the evolution of the universe, and both of them can constrain the cosmological models through data analysis. Due to the lack of data points, combining those datasets through the traditional combined method ($\chi^2$ method) to select a best-fitting cosmological model. In 2017, Linder proposed a joint method, which describes the evolution of the universe through $H(z)-f\sigma_8$ diagram instead of the redshift z. And Linder showed the advantages of distinguishing cosmologies of the joint method compared to the individual dataset. In this paper, we compare the significance between the traditional combined method and Linder's joint method by constraining the density parameter $\Omega_M$ using Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). The result shows that the joint method is more significant than the traditional combined method.

Eisner et al. (2022) reported the discovery of TIC 470710327, a massive compact hierarchical triple star system. TIC 470710327 is comprised of a compact (1.10 d) circular eclipsing binary, with total mass $\approx 10.9-13.2\ \rm{M_{\odot}}$, and a more massive ($\approx 14-17\ \rm{M_{\odot}}$) eccentric non-eclipsing tertiary in a $52.04$ d orbit. Here we present a progenitor scenario for TIC 470710327 in which '2+2' quadruple dynamics result in Zeipel-Lidov-Kozai (ZLK) resonances that lead to a contact phase of the more massive binary. In this scenario, the two binary systems should form in a very similar manner, and dynamics trigger the merger of the more massive binary either during late phases of star formation or several Myr after the zero-age main sequence (ZAMS), when the stars begin to expand. Any evidence that the tertiary is a highly-magnetised ($\sim 1-10$ kG), slowly-rotating blue main-sequence star would hint towards a quadruple origin. Finally, our scenario suggests that the population of inclined, compact multiple-stellar systems is reduced into co-planar systems, via mergers, late during star formation or early in the main sequence. The elucidation of the origin of TIC 470710327 is crucial in our understanding of multiple massive-star formation and evolution.

Meteorites display an isotopic composition dichotomy between non-carbonaceous (NC) and carbonaceous (CC) groups, indicating that planetesimal formation in the solar protoplanetary disk occurred in two distinct reservoirs. The prevailing view is that a rapidly formed Jupiter acted as a barrier between these reservoirs. We show a fundamental inconsistency in this model: if Jupiter is an efficient blocker of drifting pebbles, then the interior NC reservoir is depleted by radial drift within a few hundred thousand years. If Jupiter lets material pass it, then the two reservoirs will be mixed. Instead, we demonstrate that the arrival of the CC pebbles in the inner disk is delayed for several million years by the viscous expansion of the protoplanetary disk. Our results support that Jupiter formed in the outer disk (>10 AU) and allowed a considerable amount of CC material to pass it and become accreted by the terrestrial planets.

Having two "sibling" Type Ia supernovae (SNe Ia) in the same galaxy offers additional advantages in reducing a variety of systematic errors involved in estimating the Hubble constant, $H_{0}$. NGC 4414 is a nearby galaxy included in the Hubble Space Telescope Key Project to measure its distance using Cepheid variables. It hosts two sibling SNe Ia: SN 2021J and SN 1974G. This provides the opportunity to improve the precision of the previous estimate of $H_{0}$, which was based solely on SN 1974G. Here we present new optical $BVRI$ photometry obtained at the Observatorio de Sierra Nevada and complement it with Swift UVOT $UBV$ data, which cover the first 70 days of emission of SN 2021J. A first look at SN 2021J optical spectra obtained with the Gran Telescopio Canarias (GTC) reveals typical SN type Ia features. The main SN luminosity parameters for the two sibling SNe are obtained by using SNooPy, a light curve fitting code based on templates. Using a hierarchical bayesian approach, we build the Hubble diagram with a sample of 95 SNe Ia obtained from the Combined Pantheon Sample in the redshift range $z = 0.02-0.07$, and calibrate the zero point with the two sibling type-Ia SNe in NGC 4414. We report a value of the Hubble constant $H_{0}$ $= 72.19 \pm 2.32$ (stat.) km s$^{-1}$Mpc$^{-1}$, with a systematic error of 5.44 km s$^{-1}$Mpc$^{-1}$ due mostly to the pre-Gaia LMC zero-point systematics adopted in the HST photometry calibration of the NGC 4414 Cepheids which were used to measure the distance to NGC 4414. We expect a significant reduction of this systematic error after a new analysis of the Cepheids period-luminosity relation and photometry calibration using the upcoming Gaia DR4

The merger of two galaxies, each hosting a supermassive black hole (SMBH) of mass $10^6$\,M$_{\odot}$ or more, could yield a bound SMBH binary. For the early-type galaxy NGC\,4472, we study how astrometry with a next-generation Very Large Array (ngVLA) could be used to monitor the reflex motion of the primary SMBH of mass $M_{\rm pri}$, as it is tugged on by the secondary SMBH of mass $M_{\rm sec}$. Casting the orbit of the putative SMBH binary in terms of its period $P$, semimajor axis $a_{\rm bin}$, and mass ratio $q = M_{\rm sec} / M_{\rm pri} \le 1$, we find the following: (1) Orbits with fiducial periods of $P = 4$\,yr and 40\,yr could be spatially resolved and monitored. (2) For a 95\% accuracy of $2\,\mu$as per monitoring epoch, sub-parsec values of $a_{\rm bin}$ could be accessed over a range of mass ratios notionally encompassing major ($q > \frac{1}{4}$) and minor ($q < \frac{1}{4}$) galaxy mergers. (3) If no reflex motion is detected for $M_{\rm pri}$ after 1(10)\,yr of monitoring, a SMBH binary with period $P = 4(40)$\,yr and mass ratio $q > 0.01(0.003)$ could be excluded. This would suggest no present-day evidence for a past major merger like that recently simulated, where scouring by a $q \sim 1$ SMBH binary formed a stellar core with kinematic traits like those of NGC\,4472. (4) Astrometric monitoring could independently check the upper limits on $q$ from searches for continuous gravitational waves from NGC\,4472.

The large scale structures observed in cosmic maps correspond to super-horizon (causally disconnected) perturbations in the early Universe that are usually attributed to scale invariant adiabatic modes from cosmic Inflation. Here, we interpret discrepant measurements of the expansion rate $H_0$ (the so called Hubble tension) as super-horizon perturbations and show that they are neither adiabatic nor scale invariant. We argue that these measurements indicate that cosmic expansion originates from gravitational collapse and bounce, rather than from a singular Big Bang. This explains the observed cosmic acceleration and large scale structure without the need of Dark Energy or Inflation.

In this paper we study the applicability of a set of supervised machine learning (ML) models specifically trained to infer observed related properties of the baryonic component (stars and gas) from a set of features of dark matter only cluster-size halos. The training set is built from THE THREE HUNDRED project which consists of a series of zoomed hydrodynamical simulations of cluster-size regions extracted from the 1 Gpc volume MultiDark dark-matter only simulation (MDPL2). We use as target variables a set of baryonic properties for the intra cluster gas and stars derived from the hydrodynamical simulations and correlate them with the properties of the dark matter halos from the MDPL2 N-body simulation. The different ML models are trained from this database and subsequently used to infer the same baryonic properties for the whole range of cluster-size halos identified in the MDPL2. We also test the robustness of the predictions of the models against mass resolution of the dark matter halos and conclude that their inferred baryonic properties are rather insensitive to their DM properties which are resolved with almost an order of magnitude smaller number of particles. We conclude that the ML models presented in this paper can be used as an accurate and computationally efficient tool for populating cluster-size halos with observational related baryonic properties in large volume N-body simulations making them more valuable for comparison with full sky galaxy cluster surveys at different wavelengths. We make the best ML trained model publicly available.

With the ever-increasing sensitivity and timing baselines of modern radio telescopes, a growing number of pulsars are being shown to exhibit transitions in their rotational and radio emission properties. In many of these cases, the two are correlated with pulsars assuming a unique spin-down rate ($\dot{\nu}$) for each of their specific emission states. In this work we revisit 17 radio pulsars previously shown to exhibit spin-down rate variations. Using a Gaussian process regression (GPR) method to model the timing residuals and the evolution of the profile shape, we confirm the transitions already observed and reveal new transitions in 8 years of extended monitoring with greater time resolution and enhanced observing bandwidth. We confirm that 7 of these sources show emission-correlated $\dot{\nu}$ transitions ($\Delta \dot{\nu}$) and we characterise this correlation for one additional pulsar, PSR B1642$-$03. We demonstrate that GPR is able to reveal extremely subtle profile variations given sufficient data quality. We also corroborate the dependence of $\Delta \dot{\nu}$ amplitude on $\dot{\nu}$ and pulsar characteristic age. Linking $\Delta \dot{\nu}$ to changes in the global magnetospheric charge density $\Delta \rho$, we speculate that $\dot{\nu}$ transitions associated with large $\Delta \rho$ values may be exhibiting detectable profile changes with improved data quality, in cases where they have not previously been observed.

The study of impulsive astrophysical radio emission makes it possible to probe the intervening plasma between the emission source and the Earth. In cold electron-ion plasmas, the circular propagating wave modes primarily alter the linear polarization plane that scales with the inverse-square of the emission frequency. In relativistic plasmas, the wave modes are elliptically polarized, and it is possible to convert linearly polarized emission into circular and vice versa. Fast radio bursts (FRBs) enable the study of not only the electron-ion plasma of the intergalactic medium but potentially the extreme magneto-ionic medium in which these intense pulses are produced. Here we report on the polarimetric analysis of a repeat burst from the FRB 20201124A source. The burst displayed a significant frequency-dependent circularly polarized component, unlike other bursts from this source or any other FRB found to date. We model the frequency dependence of the circular polarization using a phenomenological generalized Faraday rotation framework. From this, we interpret the observed circular polarization in the burst as having been induced by radiative propagation through a relativistic plasma within or close to the magnetosphere of the progenitor.

Many tidally locked icy satellites in the outer Solar System show leading/trailing hemispherical asymmetries in the strength of near-infrared (NIR) H$_2$O ice absorption bands, in which the absorption bands are stronger on the leading hemisphere. This is often attributed to a combination of magnetospheric irradiation effects and impact gardening, which can modify grain size, expose fresh ice, and produce dark contaminating compounds that reduce the strength of absorption features. Previous research identified this leading/trailing asymmetry on the four largest classical Uranian satellites but did not find a clear leading/trailing asymmetry on Miranda, the smallest and innermost classical moon. We undertook an extensive observational campaign to investigate variations of the NIR spectral signature of H$_2$O ice with longitude on Miranda's northern hemisphere. We acquired 22 new spectra with the TripleSpec spectrograph on the ARC 3.5m telescope and 4 new spectra with GNIRS on Gemini North. Our analysis also includes 3 unpublished and 7 previously published spectra taken with SpeX on the 3m IRTF. We confirm that Miranda has no substantial leading/trailing hemispherical asymmetry in the strength of its H$_2$O ice absorption features. We additionally find evidence for an anti-Uranus/sub-Uranus asymmetry in the strength of the 1.5-$\mu$m H$_2$O ice band that is not seen on the other Uranian satellites, suggesting that additional endogenic or exogenic processes influence the longitudinal distribution of H$_2$O ice band strengths on Miranda.

M-dwarfs are thought to be hostile environments for exoplanets. Stellar events are very common on such stars. These events might cause the atmospheres of exoplanets to change significantly over time. It is not only the major stellar flare events that contribute to this disequilibrium, but the smaller flares might also affect the atmospheres in an accumulating manner. In this study, we aim to investigate the effects of time-dependent stellar activity on the atmospheres of known exoplanets. We simulate the chemistry of GJ876c, GJ581c, and GJ832c that go from H$_2$-dominated to N$_2$-dominated atmospheres using observed stellar spectra from the MUSCLES-collaboration. We make use of the chemical kinetics code VULCAN and implement a flaring routine that stochastically generates synthetic flares based on observed flare statistics. Using the radiative transfer code petitRADTrans we also simulate the evolution of emission and transmission spectra. We investigate the effect of recurring flares for a total of 11 days covering 515 flares. Results show a significant change in abundance for some relevant species such as H, OH, and CH$_4$, with factors going up to 3 orders of magnitude difference with respect to the preflare abundances. We find a maximum change of $\sim$12 ppm for CH$_4$ in transmission spectra on GJ876c. These changes in the spectra remain too small to observe. We also find that the change in abundance and spectra of the planets accumulate throughout time, causing permanent changes in the chemistry. We conclude this small but gradual change in chemistry arises due to the recurring flares.

The anthropic principle implies that life can emerge and be sustained only in a narrow range of values of fundamental constants (FCs). We extend the anthropic arguments to a regime of transient variations of FCs. Such regime is characteristic of clumpy dark matter models where inside the clumps FCs can reach values vastly different from their everyday values. We show that the passage of such a macroscopic clump through Earth would make Earth uninhabitable. The periodic table of elements is truncated and water fails to serve as a universal solvent. Anthropic principle enables us to improve existing astrophysical bounds on certain dark matter model couplings by five orders of magnitude.

The question of how heavy a sterile neutrino can be probed in experiments leads us to investigate the Primakoff production of heavy sterile neutrinos up to PeV masses from ultrahigh-energy neutrinos via the magnetic dipole portal. Despite the suppression from the small magnetic moment, the transition is significantly enhanced by tiny $t$-channel momentum transfers, similar to the resonant production of pions and axions in an external electromagnetic field. Based on the current IceCube measurement of astrophysical neutrinos up to PeV energies, strong constraints can already be derived on the transition magnetic moments of sterile neutrinos up to TeV masses. Moreover, we investigate the sensitivity of future tau neutrino telescopes, which are designed for EeV cosmogenic neutrino detection. We find that sterile neutrino masses as large as $30~{\rm TeV}$ can be probed at tau neutrino telescopes such as GRAND, POEMMA, and Trinity.

We introduce an interactive image segmentation and visualization framework for identifying, inspecting, and editing tiny objects (just a few pixels wide) in large multi-megapixel high-dynamic-range (HDR) images. Detecting cosmic rays (CRs) in astronomical observations is a cumbersome workflow that requires multiple tools, so we developed an interactive toolkit that unifies model inference, HDR image visualization, segmentation mask inspection and editing into a single graphical user interface. The feature set, initially designed for astronomical data, makes this work a useful research-supporting tool for human-in-the-loop tiny-object segmentation in scientific areas like biomedicine, materials science, remote sensing, etc., as well as computer vision. Our interface features mouse-controlled, synchronized, dual-window visualization of the image and the segmentation mask, a critical feature for locating tiny objects in multi-megapixel images. The browser-based tool can be readily hosted on the web to provide multi-user access and GPU acceleration for any device. The toolkit can also be used as a high-precision annotation tool, or adapted as the frontend for an interactive machine learning framework. Our open-source dataset, CR detection model, and visualization toolkit are available at https://github.com/cy-xu/cosmic-conn.

We revisit D-term inflation with the bounds of the cosmic string tension from gravitational wave observations and consider the possible deviation of the spectral index compared with $\Lambda$CDM model in light of pre-recombination resolutions of the Hubble tension. D-term inflation requires very small coupling constants under these constraints. We show that large coupling constants can be achieved in the case of D-term inflation on the brane.

We develop a novel hyperspectral imaging system using structured illumination in an SLM-based Michelson interferometer. In our design, we use a reflective SLM as a mirror in one of the arms of a Michelson interferometer, and scan the interferometer by varying the phase across the SLM display. For achieving the latter, we apply a checkerboard phase mask on the SLM display where the gray value varies between 0-255, thereby imparting a dynamic phase of up to 262{\deg} to the incident light beam. We couple a supercontinuum source into the interferometer in order to mimic an astronomical object such as the Sun, and choose a central wavelength of 637.4 nm akin to the strong emission line of Fe X present in the solar spectrum. We use a bandwidth of 30 nm, and extract fringes corresponding to a spectral resolution of 3.8 nm which is limited by the reflectivity of the SLM. We also demonstrate a maximum wavelength tunability of ~8 nm by varying the phase over the phase mask with a spectral sampling of around 0.03 nm between intermediate fringes. The checkerboard phase mask can be adapted close to real time on time-scales of a few tens of milliseconds to obtain spectral information for other near-contiguous wavelengths. The compactness, potential low cost, low power requirements, real-time tunability and lack of moving mechanical parts in the setup implies that it can have very useful applications in settings which require near real-time, multi-wavelength spectroscopic applications, and is especially relevant in space astronomy.

We develop a Birman-Schwinger principle for the spherically symmetric, asymptotically flat Einstein-Vlasov system. It characterizes stability properties of steady states such as the positive definiteness of an Antonov-type operator or the existence of exponentially growing modes in terms of a one-dimensional variational problem for a Hilbert-Schmidt operator. This requires a refined analysis of the operators arising from linearizing the system, which uses action-angle type variables. For the latter, a single-well structure of the effective potential for the particle flow of the steady state is required. This natural property can be verified for a broad class of singularity-free steady states. As a particular example for the application of our Birman-Schwinger principle we consider steady states where a Schwarzschild black hole is surrounded by a shell of Vlasov matter. We prove the existence of such steady states and derive linear stability if the mass of the Vlasov shell is small compared to the mass of the black hole.

In the context of testing general relativity with gravitational waves, constraints obtained with multiple events are typically combined either through a hierarchical formalism or though a combined multiplicative Bayes factor. We show that the well-known dependence of Bayes factors on the analysis priors in regions of the parameter space without likelihood support can lead to strong confidence in favor of incorrect conclusions when one employs the multiplicative Bayes factor. Bayes factors $\mathcal{O}(1)$ are ambivalent as they depend sensitively on the analysis priors, which are rarely set in a principled way; additionally, combined Bayes factors $>\mathcal{O}(10^3)$ can be obtained in favor of the incorrect conclusion depending on the analysis priors when many $\mathcal{O}(1)$ Bayes factors are multiplied, and specifically when the priors are much wider than the underlying population. The hierarchical analysis that instead infers the ensemble distribution of the individual beyond-general-relativity constraints does not suffer from this problem, and generically converges to favor the correct conclusion. Rather than a naive multiplication, a more reliable Bayes factor can be computed from the hierarchical analysis. We present a number of toy models showing that the practice of multiplying Bayes Factors can lead to incorrect conclusions.

The CPC (Covariant Physical Couplings) framework is a modified gravity set up assuming Einstein Field Equations wherein the quantities $\{G,c,\Lambda\}$ are promoted to spacetime functions. Bianchi identity and the requirement of stress-energy tensor conservation entangle the possible variations of the couplings $\{G,c,\Lambda\}$, which are forced to co-vary as dictated by the General Constraint (GC). In this paper we explore a cosmological model wherein $G$, $c$ and $\Lambda$ are functions of the redshift respecting the GC of the CPC framework. We assume a linear parameterization of $\Lambda$ in terms of the scale factor $a$. We use the ansatz $\dot{G}/G = \sigma \left( \dot{c}/c \right)$ with $\sigma =$ constant to deduce the functional forms of $c=c(z)$ and $G=G(z)$. We show that this varying-$\{G,c,\Lambda\}$ model fits SNe Ia data and $H(z)$ data with $\sigma = 3$. The model parameters can be constrained to describe dark energy at the background level.

A special class of conformal gravity theories is proposed to solve the long standing problem of the fine-tuned cosmological constant. In the proposed model time evolution of the inflaton field leaves behind a nearly vanishing, but finite value of dark energy density of order (a few meV)$^4$ to explain the late-time accelerating universe. A multiple scalar inflaton field is assumed to have a conformal coupling to the Ricci scalar curvature in the lagrantian, which results in, after a Weyl rescaling to the Einstein metric frame, modification of inflaton kinetic and potential terms along with its coupling to Higgs fields in the standard model. One may define an effective cosmological $\Lambda$ function in the Einstein metric frame, which controls, when the potential is added, a slow-roll inflation and subsequent oscillation at the potential minimum of a spontaneous symmetry breaking phase. The inflaton oscillation accompanies particle production towards thermalized hot big-bang universe. At the same time zero-point quantum fluctuation of second inflaton field is generated,and its accumulated fluctuation gives rise to a symmetry restoration, pushing back the inflaton field towards the infinity. This gives a dynamical relaxation of vanishing effective cosmological constant. Both inhomogeneous inflaton modes and their collapsed black holes of primordial origin are good candidates of cold dark matter.

We present experimental results on optical trapping of Yb-doped $\beta-$NaYF sub-wavelength-thickness high-aspect-ratio hexagonal prisms with a micron-scale radius. The prisms are trapped in vacuum using an optical standing wave, oriented with the normal vector to their face along the beam propagation direction, and exhibit characteristic modes of three translational and two torsional degrees of freedom. The measured motional spectra are compared with numerical simulations. This plate-like geometry simultaneously enables trapping with low photon-recoil-heating, high mass, and high trap frequency, potentially leading to advances in high frequency gravitational wave searches in the Levitated Sensor Detector (LSD), currently under construction. The material used here has previously been shown to exhibit internal cooling via laser refrigeration when optically trapped and illuminated with light of suitable wavelength. Employing such laser refrigeration methods in the context of our work may enable higher trapping intensity thus and higher trap frequencies for gravitational wave searches approaching the several hundred kHz range.