Papers for Wednesday, May 12 2021

We present a star formation rate function (SFRF) at $z\sim4.5$ based on photometric data from rest UV to optical of galaxies in the CANDELS GOODS-South field using spectral energy distribution (SED) fitting. We evaluate the incompleteness of our sample and correct for it to properly confront the SFRF in this study with those estimated based on other probes. The SFRF is obtained down to $\sim10\ M_\odot\ \mathrm{yr}^{-1}$ and it shows a significant excess to that estimated from UV luminosity function and dust correction based on UV spectral slope. As compared with the UV-based SFRF, the number density is larger by $\sim1$ dex at a fixed SFR, or the best-fit Schechter parameter of $\mathrm{SFR}^*$ is larger by $\sim1$ dex. We extensively examine several assumptions on SED fitting to see the robustness of our result, and find that the excess still exist even if the assumptions change such as star formation histories, dust extinction laws, and one- or two-component model. By integrating our SFRF to $0.22\ M_\odot\ \mathrm{yr}^{-1}$, the cosmic star formation rate density at this epoch is calculated to be $4.53^{+0.94}_{-0.87}\times10^{-2}\ M_\odot\ \mathrm{yr}^{-1}\ \mathrm{Mpc}^{-3}$, which is $\sim0.25$ dex larger than the previous measurement based on UV observations. We also find that galaxies with intensive star formation ($>10\ M_\odot\ \mathrm{yr}^{-1}$) occupies most of the cosmic star formation rate density ($\sim80\%$), suggesting that star formation activity at this epoch is dominant by intensively star-forming galaxies.

Supermassive black hole binary mergers generate a stochastic gravitational wave background detectable by pulsar timing arrays. While the amplitude of this background is subject to significant uncertainties, the frequency dependence is a robust prediction of general relativity. We show that the effects of new forces beyond the Standard Model can modify this prediction and introduce unique features into the spectral shape. In particular, we consider the possibility that black holes in binaries are charged under a new long-range force, and we find that pulsar timing arrays are capable of robustly detecting such forces. Supermassive black holes and their environments can acquire charge due to high-energy particle production or dark sector interactions, making the measurement of the spectral shape a powerful test of fundamental physics.

We investigate the formation of the satellite galaxy population of a Milky Way-mass halo in a very highly resolved magneto-hydrodynamic cosmological zoom-in simulation (baryonic mass resolution $m_b =$ 800 $\rm M_{\odot}$). We show that the properties of the central star-forming galaxy, such as the radial stellar surface density profile and star formation history, are: i) robust to stochastic variations associated with the so-called "Butterfly Effect"; and ii) well converged over 3.5 orders of magnitude in mass resolution. We find that there are approximately five times as many satellite galaxies at this high resolution compared to a standard ($m_b\sim 10^{4-5}\, \rm M_{\odot}$) resolution simulation of the same system. This is primarily because 2/3rds of the high resolution satellites do not form at standard resolution. A smaller fraction (1/6th) of the satellites present at high resolution form and disrupt at standard resolution; these objects are preferentially low-mass satellites on intermediate- to low-eccentricity orbits with impact parameters $\lesssim 30$ kpc. As a result, the radial distribution of satellites becomes substantially more centrally concentrated at higher resolution, in better agreement with recent observations of satellites around Milky Way-mass haloes. Finally, we show that our galaxy formation model successfully forms ultra-faint galaxies and reproduces the stellar velocity dispersion, half-light radii, and $V$-band luminosities of observed Milky Way and Local Group dwarf galaxies across 7 orders of magnitude in luminosity ($10^3$-$10^{10}$ $\rm L_{\odot}$).

We report the discovery of a 'folded' gravitationally lensed image, 'Hamilton's Object', found in a HST image of the field near the AGN SDSS J223010.47-081017.8 ($z=0.62$). The lensed images are sourced by a galaxy at a spectroscopic redshift of 0.8200$\pm0.0005$ and form a fold configuration on a caustic caused by a foreground galaxy cluster at a photometric redshift of 0.526$\pm0.018$ seen in the corresponding Pan-STARRS PS1 image and marginally detected as a faint ROSAT All-Sky Survey X-ray source. The lensed images exhibit properties similar to those of other folds where the source galaxy falls very close to or straddles the caustic of a galaxy cluster. The folded images are stretched in a direction roughly orthogonal to the critical curve, but the configuration is that of a tangential cusp. Guided by morphological features, published simulations and similar fold observations in the literature, we identify a third or counter-image, confirmed by spectroscopy. Because the fold-configuration shows highly distinctive surface brightness features, follow-up observations of microlensing or detailed investigations of the individual surface brightness features at higher resolution can further shed light on kpc-scale dark matter properties. We determine the local lens properties at the positions of the multiple images according to the observation-based lens reconstruction of Wagner et al. (2019). The analysis is in accordance with a mass density which hardly varies on an arc-second scale (6 kpc) over the areas covered by the multiple images.

Asteroseismic measurements enable inferences of the underlying stellar structure, such as the density and the speed of sound at various points within the interior of the star. This provides an opportunity to test stellar evolution theory by assessing whether the predicted structure of a star agrees with the measured structure. Thus far, this kind of inverse analysis has only been applied to the Sun and three solar-like main-sequence stars. Here we extend the technique to stars on the subgiant branch, and apply it to one of the best-characterized subgiants of the Kepler mission, HR 7322. The observation of mixed oscillation modes in this star facilitates inferences of the conditions of its inert helium core, nuclear-burning hydrogen shell, and the deeper parts of its radiative envelope. We find that despite significant differences in the mode frequencies, the structure near to the center of this star does not differ significantly from the predicted structure.

We present the first results of an MMT/Hectospec campaign to measure the kinematics of globular clusters (GCs) around M49 -- the brightest galaxy in the Virgo galaxy cluster, which dominates the Virgo B subcluster. The data include kinematic tracers beyond 95 kpc (~5.2 effective radii) for M49 for the first time, enabling us to achieve three key insights reported here. First, beyond ~20'-30' (~100-150 kpc), the GC kinematics sampled along the minor photometric axis of M49 become increasingly hotter, indicating a transition from GCs related to M49 to those representing the Virgo B intra-cluster medium. Second, there is an anomaly in the line-of-sight radial velocity dispersion ($\sigma_{r,los}$) profile in an annulus ~10-15' (~50-90 kpc) from M49 in which the kinematics cool by $\Delta \sigma_{r,los}~150$ km s$^{-1}$ relative to those in- or outward. The kinematic fingerprint of a previous accretion event is hinted at in projected phase-space, and we isolate GCs that both give rise to this feature, and are spatially co-located with two prominent stellar shells in the halo of M49. Third, we find a subsample of GCs with velocities representative of the dwarf galaxy VCC1249 that is currently interacting with M49. The spatial distribution of these GCs closely resembles the morphology of VCC1249's isophotes, indicating that several of these GCs are likely in the act of being stripped from the dwarf during its passage through M49's halo. Taken together, these results point toward the opportunity of witnessing on-going giant halo assembly in the depths of a cluster environment.

We model the distribution of the observed profiles of 21 cm line emission from neutral hydrogen (HI) in central galaxies selected from a statistically representative mock catalog of the local Universe in the Lambda-cold dark matter framework. The distribution of these HI velocity profiles (specifically, their widths $W_{50}$) has been observationally constrained, but has not been systematically studied theoretically. Our model profiles derive from rotation curves of realistically baryonified haloes in an N-body simulation, including the quasi-adiabatic relaxation of the dark matter profile of each halo in response to its baryons. We study the predicted $W_{50}$ distribution using a realistic pipeline applied to noisy profiles extracted from our luminosity-complete mock catalog with an ALFALFA-like survey geometry and redshift selection. Our default mock is in good agreement with observed ALFALFA results for $W_{50}\gtrsim700$ km/s, being incomplete at lower widths due to the intrinsic threshold of $M_r\leq-19$. Variations around the default model show that the velocity width function at $W_{50}\gtrsim300$ km/s is most sensitive to a possible correlation between galaxy inclination and host concentration, followed by the physics of quasi-adiabatic relaxation. We also study the excess kurtosis of noiseless velocity profiles, obtaining a distribution which tightly correlates with $W_{50}$, with a shape and scatter that depend on the properties of the turbulent HI disk. Our results open the door towards using the shapes of HI velocity profiles as a novel statistical probe of the baryon-dark matter connection.

We report on the discovery of SPLUS J210428.01-004934.2, an ultra metal-poor (UMP) star first identified from the narrow-band photometry of the Southern Photometric Local Universe Survey (S-PLUS) Data Release 1, in the SDSS Stripe 82 region. Follow-up medium- and high-resolution spectroscopy (with Gemini South and Magellan-Clay, respectively) confirmed the effectiveness of the search for low-metallicity stars using the S-PLUS narrow-band photometry. At [Fe/H]=-4.03, SPLUS J2104-0049 has the lowest detected carbon abundance, A(C)=+4.34, when compared to the 34 previously known UMP stars in the literature, which is an important constraint on its stellar progenitor and also on stellar evolution models at the lowest metallicities. Based on its chemical abundance pattern, we speculate that SPLUS J2104-0049 could be a bonafide second-generation star, formed from a gas cloud polluted by a single metal-free ~30Mo star. This discovery opens the possibility of finding additional UMP stars directly from narrow-band photometric surveys, a potentially powerful method to help complete the inventory of such peculiar objects in our Galaxy.

Linear polarization measurements in the optical band show polarization degrees of a few percent at late times. Recently, polarization at sub-percent level was also detected in radio by ALMA, opening the window for multi-wavelength polarimetry and stressing the importance of properly modeling polarization in GRB afterglows across the EM spectrum. We introduce a numerical tool that can calculate the polarization from relativistically moving surfaces by discretizing them to small patches of uniform magnetic field, calculating the polarized emission from each cell assuming synchrotron radiation and summing it to obtain the total degree of polarization. We apply this tool to afterglow shocks with random magnetic fields confined to the shock plane, considering electron radiative cooling. We analyze the observed polarization curves in several wavelengths above the cooling frequency and below the minimal synchrotron frequency and point to the characteristic differences between them. We present a method to constrain the jet opening angle and the viewing angle within the context of our model. Applying it to GRB 021004 we obtain angles of 10 and 8 degrees respectively and conclude that a non-negligible component of radial magnetic field is required to explain the 1% polarization level observed 3.5 days after the burst.

The dwarf galaxy NGC 3109 is receding 105 km/s faster than expected in a $\Lambda$CDM timing argument analysis of the Local Group and external galaxy groups within 8 Mpc (Banik \& Zhao 2018). If this few-body model accurately represents long-range interactions in $\Lambda$CDM, this high velocity suggests that NGC 3109 is a backsplash galaxy that was once within the virial radius of the Milky Way and was slingshot out of it. Here, we use the Illustris TNG300 cosmological hydrodynamical simulation and its merger tree to identify backsplash galaxies. We find that backsplashers as massive ($\geq 4.0 \times 10^{10} M_\odot$) and distant ($\geq 1.2$ Mpc) as NGC 3109 are extremely rare, with none having also gained energy during the interaction with their previous host. This is likely due to dynamical friction. Since we identified 13225 host galaxies similar to the Milky Way or M31, we conclude that postulating NGC 3109 is a backsplash galaxy causes $>3.96\sigma$ tension with the expected distribution of backsplashers in $\Lambda$CDM. We show that the dark matter only version of TNG300 yields much the same result, demonstrating its robustness to how the baryonic physics is modelled. If instead NGC 3109 is not a backsplasher, consistency with $\Lambda$CDM would require the 3D timing argument analysis to be off by 105 km/s for this rather isolated dwarf, which we argue is unlikely. We discuss a possible alternative scenario for NGC 3109 and the Local Group satellite planes in the context of MOND, where the Milky Way and M31 had a past close flyby $7-10$ Gyr ago.

We calculate the deflection angle, as well as the positions and magnifications of the lensed images, in the case of covariant $f(T)$ gravity. We first extract the spherically symmetric solutions for both the pure-tetrad and the covariant formulation of the theory, since considering spherical solutions the extension to the latter is crucial, in order for the results not to suffer from frame-dependent artifacts. Applying the weak-field, perturbative approximation we extract the deviations of the solutions comparing to General Relativity. Furthermore, we calculate the deflection angle and then the differences of the positions and magnifications in the lensing framework. This effect of consistent $f(T)$ gravity on the lensing features can serve as an observable signature in the realistic cases where $f(T)$ is expected to deviate only slightly from General Relativity, since lensing scales in general are not restricted as in the case of Solar System data, and therefore deviations from General Relativity could be observed more easily.

Being one of the most abundant atomic/molecular species observed in dense molecular gas, atomic carbon ($\mathrm{C}^0$) is a potential good tracer of molecular gas mass in many chemical/physical environments, though the $\mathrm{C^0}$ abundance variation outside the Galactic disk region is yet to be fully known. This paper presents a wide-field 500 GHz [CI] map of the Galactic central molecular zone (CMZ) obtained with the ASTE 10-m telescope. Principal component analysis and non-LTE multi-transition analysis have shown that the [CI] emission predominantly originates from the low-excitation gas component with a 20-50 K temperature and $\sim 10^3\ \mathrm{cm}^{-3}$ density, whereas $\mathrm{C^0}$ abundance is likely suppressed in the high-excitation gas component. The average $N(\mathrm{C}^0)$/$N(\mathrm{CO})$ abundance ratio in the CMZ is 0.3-0.4, which is 2-3 times that in the Galactic disk. The $N(\mathrm{C}^0)$/$N(\mathrm{CO})$ ratio increases to 0.7 in the innermost 10 pc region and to $\sim2$ in the circumnuclear disk. We discovered $\mathrm{C^0}$-rich regions distributed in a ring-shape encircling the supernova remnant (SNR) Sgr A east, indicative that the $\mathrm{C}^0$-enrichment in the central 10 pc region is a consequence of a molecular cloud-SNR interaction. In the 15 atom/molecules included in principal component analysis (PCA), CN is the only other species that increases in the [CI]-bright ring. The origin of the [CI]-bright ring is likely a cosmic-ray dominated region created by low-energy cosmic-ray particles accelerated by Sgr A east or primitive molecular gas collected by the SNR in which the $\mathrm{C}^0$-to-CO conversion has not reached the equilibrium.

Mid- to far-infrared (IR) lines are suited to study dust obscured regions in galaxies, because IR spectroscopy allows us to explore the most hidden regions where heavily obscured star formation as well as accretion onto supermassive black-holes occur. This is mostly important at redshifts of 1<z<3, when most of the baryonic mass in galaxies has been assembled. We provide reliable calibrations of the mid- to far-IR ionic fine structure lines, the brightest H2 pure rotational lines and the Polycyclic Aromatic Hydrocarbons (PAHs) features, that will be used to analyse current and future observations in the mm/submm range from the ground, as well as mid-IR spectroscopy from the upcoming James Webb Space Telescope. We use three samples of galaxies observed in the local Universe: star forming galaxies, AGN and low-metallicity dwarf galaxies. For each population we derive different calibrations of the observed line luminosities versus the total IR luminosities. We derive spectroscopic measurements of SFR and BHAR using mid- and far-IR fine structure lines, H2 pure rotational lines and PAH features. We derive robust star-formation tracers based on the [CII]158 $\mu$m line; the sum of the [OI]63$\mu$m and [OIII]88$\mu$m lines; a combination of the neon and sulfur mid-IR lines; the bright PAH features at 6.2 and 11.3 $\mu$m, and the H2 rotational lines at 9.7, 12.3 and 17 $\mu$m. We propose the [CII]158$\mu$m line, the combination of two neon lines and, for solar-like metallicity galaxies that may harbor an AGN, the PAH11.3$\mu$m feature as the best SFR tracers. A reliable measure of the BHAR can be obtained using the [OIV]25.9 $\mu$m and the [NeV]14.3 and 24.3 $\mu$m lines. For the most commonly observed fine-structure lines in the far-IR we compare our calibration with the existing ALMA observations of high redshift galaxies finding overall a good agreement with local results.

Context. The physical processes driving the formation of Galactic spiral arms are still under debate. Studies using open clusters favour the description of the Milky Way spiral arms as long-lived structures following the classical density wave theory. Current studies comparing the Gaia DR2 field stars kinematic information of the Solar neighbourhood to simulations, find a better agreement with short-lived arms with a transient behaviour. Aims. Our aim is to provide an observational, data-driven view of the Milky Way spiral structure and its dynamics using open clusters as the main tracers, and to contrast it with simulation-based approaches. We use the most complete catalogue of Milky Way open clusters, with astrometric Gaia EDR3 updated parameters, estimated astrophysical information and radial velocities, to re-visit the nature of the spiral pattern of the Galaxy. Methods. We use a Gaussian mixture model to detect overdensities of open clusters younger than 30 Myr that correspond to the Perseus, Local, Sagittarius and Scutum spiral arms, respectively. We use the birthplaces of the open cluster population younger than 80 Myr to trace the evolution of the different spiral arms and compute their pattern speed. We analyse the age distribution of the open clusters across the spiral arms to explore the differences in the rotational velocity of stars and spiral arms. Results. We are able to increase the range in Galactic azimuth where present-day spiral arms are described, better estimating its parameters by adding 264 young open clusters to the 84 high-mass star-forming regions used so far, thus increasing by a 314% the number of tracers. We use the evolution of the open clusters from their birth positions to find that spiral arms nearly co-rotate with field stars at any given radius, discarding a common spiral pattern speed for the spiral arms explored. [abridged]

Previous work concerning planet formation around low-mass stars has often been limited to large planets and individual systems. As current surveys routinely detect planets down to terrestrial size in these systems, a more holistic approach that reflects their diverse architectures is timely. Here, we investigate planet formation around low-mass stars and identify differences in the statistical distribution of planets. We compare the synthetic planet populations to observed exoplanets. We used the Generation III Bern model of planet formation and evolution to calculate synthetic populations varying the central star from solar-like stars to ultra-late M dwarfs. This model includes planetary migration, N-body interactions between embryos, accretion of planetesimals and gas, and long-term contraction and loss of the gaseous atmospheres. We find that temperate, Earth-sized planets are most frequent around early M dwarfs and more rare for solar-type stars and late M dwarfs. The planetary mass distribution does not linearly scale with the disk mass. The reason is the emergence of giant planets for M*>0.5 Msol, which leads to the ejection of smaller planets. For M*>0.3 Msol there is sufficient mass in the majority of systems to form Earth-like planets, leading to a similar amount of Exo-Earths going from M to G dwarfs. In contrast, the number of super-Earths and larger planets increases monotonically with stellar mass. We further identify a regime of disk parameters that reproduces observed M-dwarf systems such as TRAPPIST-1. However, giant planets around late M dwarfs such as GJ 3512b only form when type I migration is substantially reduced. We quantify the stellar mass dependence of multi-planet systems using global simulations of planet formation and evolution. The results compare well to current observational data and predicts trends that can be tested with future observations.

The unusual Type IIP SN 2017gmr is revisited in order to pinpoint the origin of its anomalous features, including the peculiar light curve after about 100 days. The hydrodynamic modelling suggests the enormous explosion energy of about 10^52 erg. We find that the light curve with the prolonged plateau/tail transition can be reproduced either in the model with a high hydrogen abundance in the inner ejecta and a large amount of radioactive Ni-56, or in the model with an additional central energy source associated with the fallback/magnetar interaction in the propeller regime. The asymmetry of the late H-alpha emission and the reported linear polarization are reproduced by the model of the bipolar Ni-56 ejecta. The similar bipolar structure of the oxygen distribution is responsible for the two-horn structure of the [O I] 6360, 6364 A emission. The bipolar Ni-56 structure along with the high explosion energy are indicative of the magneto-rotational explosion. We identify narrow high-velocity absorption features in H-alpha and He I 10830 A lines with their origin in the fragmented cold dense shell formed due to the outer ejecta deceleration in a confined circumstellar shell.

Large-scale experiments are building blocks of the physics community: they involve a large fraction of the scientific staff working in multiple countries, and absorb a significant volume of the science budget. They are also a collection of carbon-emitting sources and practices. As such, it is essential to assess their environmental impact. We describe here a methodology to estimate the main greenhouse gas (GHG) emissions of a large-scale astrophysics collaboration project, using transparent open data. The goal is neither to consider all possible emission sources of a project, nor to calculate accurate values. It is rather to identify the biggest emission sources of the project, obtain orders of magnitude for them and analyse their relative weights. We discuss methods to quantify the GHG-generating activities and their related emission factors for the three typical biggest emission sources that can be controlled by the collaboration: travel, digital and hardware.

We present the latest results of our ongoing multiplicity study of (Community) TESS Objects of Interest, using astro- and photometric data from the ESA-Gaia mission, to detect stellar companions of these stars and to characterize their properties. In total, 113 binary, 5 hierarchical triple star systems, as well as one quadruple system were detected among 585 targets surveyed, which are all located at distances closer than about 500pc around the Sun. As proven with their accurate Gaia EDR3 astrometry the companions and the targets are located at the same distance and share a common proper motion, as it is expected for components of gravitationally bound stellar systems. The companions exhibit masses in the range between about 0.09$M_\odot$ and 4.5$M_\odot$ and are most frequently found in the mass range between 0.15 and 0.6$M_{\odot}$. The companions are separated from the targets by about 120 up to 9500au and their frequency is the highest and constant within about 500au while it continually decreases for larger separations. Beside mainly early to mid M dwarfs, also 5 white dwarf companions were identified in this survey, whose true nature was revealed by their photometric properties.

Significant progress in cosmic ray (CR) studies was achieved over the past decade. Particularly important are precise measurements of primary and secondary species in the TV rigidity domain that show a bump in the spectra of CR species from 0.5-50 TV. In this letter, we argue that it is likely caused by a stellar bow- or wind-termination shock that reaccelerates preexisting CRs, which further propagate to the Sun along the magnetic field lines. This single universal process is responsible for the observed spectra of all CR species in the rigidity range below 100 TV. A viable candidate is Epsilon Eridani star at 3.2 pc from the Sun, which is well-aligned with the direction of the local magnetic field. We provide a simple formula that reproduces the spectra of all CR species with only two nonadjustable shock parameters, uniquely derived from the proton data. We show how our formalism predicts helium and carbon spectra and the B/C ratio.

A number of hardware upgrades for the Low-Frequency Array (LOFAR) are currently under development. These upgrades are collectively referred to as the LOFAR 2.0 upgrade. The first stage of LOFAR 2.0 will introduce a distributed clock signal and allow for simultaneous observation with all the low-band and high-band antennas of the array. Our aim is to provide a tool for accurate simulations of LOFAR 2.0. We present a software to simulate LOFAR and LOFAR 2.0 observations, which includes realistic models for all important systematic effects such as the first and second order ionospheric corruptions, time-variable primary-beam attenuation, station based delays and bandpass response. The ionosphere is represented as a thin layer of frozen turbulence. Furthermore, thermal noise can be added to the simulation at the expected level. We simulate a full 8-hour simultaneous low- and high-band antenna observation of a calibrator source and a target field with the LOFAR 2.0 instrument. The simulated data is calibrated using readjusted LOFAR calibration strategies. We examine novel approaches of solution-transfer and joint calibration to improve direction-dependent ionospheric calibration for LOFAR. We find that the calibration of the simulated data behaves very similarly to a real observation and reproduces characteristic properties of LOFAR data such as realistic solutions and image quality. We analyze strategies for direction-dependent calibration of LOFAR 2.0 and find that the ionospheric parameters can be determined most accurately when combining the information of the high-band and low-band in a joint calibration approach. In contrast, the transfer of total electron content solutions from the high-band to the low-band shows good convergence but is highly susceptible to the presence of non-ionospheric phase errors in the data.

Rich and poor galaxy clusters have the same measured halo metallicity, 0.35-0.4 $Z_\odot$, despite being an order of magnitude apart in stellar fraction, $M_*/M_{gas}$. The measured ICM metallicity in rich clusters cannot be explained by the visible stellar population as stars make up only 5% of the total gas mass. The independence of metallicity from $M_*/M_{gas}$ suggests an external and universal source of metals such as an Early Enrichment Population (EEP). Galaxy cluster RX J1416.4+2315 has the lowest stellar fraction known, $M_*/M_{gas}=0.015\pm0.003$, and here we improve the halo metallicity determination using archival $\textit{Chandra}$ and $\textit{XMM Newton}$ observations. We determine the ICM metallicity of RXJ to be $0.336\pm0.058$ $Z_\odot$ within $0.3<R/R_{500}<0.75$, excluding the central galaxy. We combine this measurement with other clusters with a wider range of $M_*/M_{gas}$ resulting in the fit of $Z_{tot}=(0.37\pm0.01)+(0.13\pm 0.17)(M_*/M_{gas})$. This fit is largely independent of $M_*/M_{gas}$, and shows that for a low $M_*/M_{gas}$ system the observed stellar population can make only 10-20% of the total metals. We quantify the Fe contribution of the EEP further by adopting a standard Fe yield for visible stellar population, and find that $Z_{EEP}=(0.36\pm0.01)-(1.44\pm0.17)(M_*/M_{gas})$. To account for the observed Fe mass, a supernova rate of $6.6\pm3.0$ SNe yr$^{-1}$ (Type Ia) and $5.0\pm2.5$ SNe yr$^{-1}$ (core collapse) is required over the redshift range $3<z<10$ for a single galaxy cluster with mass $\sim3\times10^{14}$ $M_\odot$ at z=0. These supernovae might be visible in JWST observation of high redshift clusters and protoclusters.

M-stars are the most common hosts of planetary systems in the Galaxy. Protoplanetary disks around M-stars thus offer a prime opportunity to study the chemistry of planet-forming environments. We present an ALMA survey of molecular line emission toward a sample of five protoplanetary disks around M4-M5 stars (FP Tau, J0432+1827, J1100-7619, J1545-3417, and Sz 69). These observations can resolve chemical structures down to tens of AU. Molecular lines of $^{12}$CO, $^{13}$CO, C$^{18}$O, C$_2$H, and HCN are detected toward all five disks. Lines of H$_2$CO and DCN are detected toward 2/5 and 1/5 disks, respectively. For disks with resolved C$^{18}$O, C$_2$H, HCN, and H$_2$CO emission, we observe substructures similar to those previously found in disks around solar-type stars (e.g., rings, holes, and plateaus). C$_2$H and HCN excitation conditions estimated interior to the pebble disk edge for the bright disk J1100-7619 are consistent with previous measurements around solar-type stars. The correlation previously found between C$_2$H and HCN fluxes for solar-type disks extends to our M4-M5 disk sample, but the typical C$_2$H/HCN ratio is higher for the M4-M5 disk sample. This latter finding is reminiscent of the hydrocarbon enhancements found by previous observational infrared surveys in the innermost ($<$10AU) regions of M-star disks, which is intriguing since our disk-averaged fluxes are heavily influenced by flux levels in the outermost disk, exterior to the pebble disk edge. Overall, most of the observable chemistry at 10-100AU appears similar for solar-type and M4-M5 disks, but hydrocarbons may be more abundant around the cooler stars.

Resonant torques couple stellar bars to dark matter halos. Here we use high-resolution numerical simulations to demonstrate long-term angular momentum transfer between stellar bars and dark matter orbits of varying orientation. We show that bar-driven reversals of dark matter orbit orientations can play a surprisingly large role in the evolution of the bar pattern speed. In predominantly prograde (co-rotating) halos, dark matter orbits become trapped in the stellar bar forming a parallel dark matter bar. This dark matter bar reaches more than double the vertical height of the stellar bar. In halos dominated by retrograde orbits, a dark matter wake forms oriented perpendicular to the stellar bar. These dark matter over-densities provide a novel space to look for dark matter annihilation or decay signals. % We predict that the Milky Way hosts a dark matter bar aligned with the stellar bar as well as a dark matter wake the near-side of which should extend from Galactic center to a galactic longitude of $l \approx 323^\circ$.

Population studies of Kepler's multi-planet systems have revealed a surprising degree of structure in their underlying architectures. Information from a detected transiting planet can be combined with a population model to make predictions about the presence and properties of additional planets in the system. Using a statistical model for the distribution of planetary systems (He et al. 2020; arXiv:2007.14473), we compute the conditional occurrence of planets as a function of the period and radius of Kepler--detectable planets. About half ($0.52 \pm 0.03$) of the time, the detected planet is not the planet with the largest semi-amplitude $K$ in the system, so efforts to measure the mass of the transiting planet with RV follow-up will have to contend with additional planetary signals in the data. We simulate RV observations to show that assuming a single--planet model to measure the $K$ of the transiting planet often requires significantly more observations than in the ideal case with no additional planets, due to the systematic errors from unseen planet companions. Our results show that planets around 10-day periods with $K$ close to the single--measurement RV precision ($\sigma_{1,\rm obs}$) typically require $\sim 100$ observations to measure their $K$ to within 20% error. For a next generation RV instrument achieving $\sigma_{1,\rm obs} = 10$ cm/s, about $\sim 200$ ($600$) observations are needed to measure the $K$ of a transiting Venus in a Kepler--like system to better than 20% (10%) error, which is $\sim 2.3$ times as many as what would be necessary for a Venus without any planetary companions.

In this third paper in our cloud-collision series, we present the results from simulations of head-on collisions with a strongly centrally-condensed initial density profile of $\rm \rho \propto R^{-2}$. We investigate the impact of these density profiles on the overall evolution of the simulations: the structures formed, their dynamical evolution, and their star formation activity. We consider clouds which are globally bound and globally unbound, leading to three different scenarios -- the collision of a bound cloud with a bound cloud, the collision of two unbound clouds, or the collision of one cloud of each type. In all the simulations dense star clusters form before the collisions occur, and we find that star formation remains confined to these systems and is little affected by the collisions. If the clouds' are both initially bound, the collision forms a filamentary structure, but otherwise, this does not occur. We observe that rotating structures form around the clusters, but they also form in our non-colliding control simulations, so are not a consequence of the collisions. Dissipation of kinetic energy in these simulations is inefficient because of the substructure created in the clouds by turbulence before the collisions. As a result, although some gas is left bound in the COM frame, the star clusters formed in the simulations do not become bound to each other.

Recent X-ray observations by Jiang et al. have identified an active galactic nucleus (AGN) in the bulgeless spiral galaxy NGC 3319, located just $14.3\pm1.1\,$Mpc away, and suggest the presence of an intermediate-mass black hole (IMBH; $10^2\leq M_\bullet/\mathrm{M_{\odot}}\leq10^5$) if the Eddington ratios are as high as 3 to $3\times10^{-3}$. In an effort to refine the black hole mass for this (currently) rare class of object, we have explored multiple black hole mass scaling relations, such as those involving the (not previously used) velocity dispersion, logarithmic spiral-arm pitch angle, total galaxy stellar mass, nuclear star cluster mass, rotational velocity, and colour of NGC 3319, to obtain ten mass estimates, of differing accuracy. We have calculated a mass of $3.14_{-2.20}^{+7.02}\times10^4\,\mathrm{M_\odot}$, with a confidence of 84% that it is $\leq$$10^5\,\mathrm{M_\odot}$, based on the combined probability density function from seven of these individual estimates. Our conservative approach excluded two black hole mass estimates (via the nuclear star cluster mass, and the fundamental plane of black hole activity $\unicode{x2014}$ which only applies to black holes with low accretion rates) that were upper limits of $\sim$$10^5\,{\rm M}_{\odot}$, and it did not use the $M_\bullet\unicode{x2013}L_{\rm 2-10\,keV}$ relation's prediction of $\sim$$10^5\,{\rm M}_{\odot}$. This target provides an exceptional opportunity to study an IMBH in AGN mode and advance our demographic knowledge of black holes. Furthermore, we introduce our novel method of meta-analysis as a beneficial technique for identifying new IMBH candidates by quantifying the probability that a galaxy possesses an IMBH.

Rotation is a critical physical process operating in the formation of Am stars. There is a strong correlation between low-velocity rotation and chemical peculiarity. However, the existence of many non-CP slow rotators challenges the understanding of Am stars. The purpose of our work is to search for low-velocity rotating non-CP A-type stars and Am stars and to make a comparative analysis. In this paper, we pick out a sample from the LAMOST-Kepler project, including 21 Am stars, 125 non-CP slow rotators, and 53 non-CP fast rotators. We calculate the rotational frequencies through periodic change of light curves caused by inhomogeneous stellar surfaces and then obtain the rotational velocities. For slow rotators, the age of Am stars is statistically younger than that of non-CP stars in the same temperature bin. In the comparison of the period, the average amplitude, and stellar mass of Am and non-CP stars, we discover that there is no difference in the photometric variability between Am and non-CP stars, which implies similar inhomogeneities on the surfaces. The average amplitude of non-CP stars has a downward trend with the increase of effective temperature and stellar mass, which is consistent with the theoretical prediction caused by weak dynamo-generated magnetic fields in A-type stars. In addition, we confirm four non-non-CP stars which have flares by checking FOV images, 24 pixel images, and pixel-level light curves.

Solar-type stars exhibit their highest levels of magnetic activity during their early convective pre-main sequence (PMS) phase of evolution. The most powerful PMS flares, super-flares and mega-flares, have peak X-ray luminosities of $\log(L_X)=30.5-34.0$~erg~s$^{-1}$ and total energies $\log(E_X)=34-38$~erg. Among $>24,000$ X-ray selected young ($t<5$~Myr) members of 40 nearby star-forming regions from our earlier $Chandra$ MYStIX and SFiNCs surveys, we identify and analyze a well-defined sample of 1,086 X-ray super-flares and mega-flares, the largest sample ever studied. Most are considerably more powerful than optical/X-ray super-flares detected on main sequence stars. This study presents energy estimates of these X-ray flares and the properties of their host stars. These events are produced by young stars of all masses over evolutionary stages ranging from protostars to diskless stars, with the occurrence rate positively correlated with stellar mass. Flare properties are indistinguishable for disk-bearing and diskless stars indicating star-disk magnetic fields are not involved. A slope $\alpha\simeq2$ in the flare energy distributions $dN/dE_X \propto E_X^{-\alpha}$ is consistent with those of optical/X-ray flaring from older stars and the Sun. Mega-flares ($\log(E_X) > 36.2$~erg) from solar-mass stars have occurrence rate of $1.7_{-0.6}^{+1.0}$ flares/star/year and contribute at least $10-20$\% to the total PMS X-ray energetics. These explosive events may have important astrophysical effects on protoplanetary disk photoevaporation, ionization of disk gas, production of spallogenic radionuclides in disk solids, and hydrodynamic escape of young planetary atmospheres. Our following paper details plasma and magnetic loop modeling of the $>50$ brightest X-ray mega-flares.

Heavily obscured active galactic nuclei (AGNs) are known to show deep silicate absorption features in the mid-infrared (IR) wavelength range of 10--20~$\mu$m. The detailed profiles of the features reflect the properties of silicate dust, which are likely to include information on AGN activities obscured by large amounts of dust. In order to reveal AGN activities obscured by large amounts of dust, we select 115 mid-IR spectra of heavily obscured AGNs observed by Spitzer/IRS, and systematically analyze the composition of silicate dust by spectral fitting using the 10~$\mu$m amorphous and 23~$\mu$m crystalline bands. We find that the main component of the silicate dust obscuring AGNs is amorphous olivine, the median mass column density of which is one order of magnitude higher than those of the minor components of amorphous pyroxene and crystalline forsterite. The median mass fraction of the amorphous pyroxene, $\sim$2\%, is significantly lower than that of the diffuse interstellar medium (ISM) dust in our Galaxy, while the median mass fraction of the crystalline forsterite, $\sim$6\%, is higher than that of the diffuse ISM dust. We also find that the mass fractions of the amorphous pyroxene and the crystalline forsterite positively correlate with each other. The low mass fraction of the amorphous pyroxene suggests that the obscuring silicate dust is newly formed, originating from starburst activities. The relatively high mass fraction of crystalline forsterite implies that the silicate dust is processed in the high temperature environment close to the nucleus and transported to outer cooler regions by molecular outflows. The positive correlation between the mass fractions can be naturally explained considering that amorphous pyroxene is transformed from crystalline forsterite by ion bombardments.

The line-of-sight peculiar velocities are good indicators of the gravitational fluctuation of the density field. Techniques have been developed to extract cosmological information from the peculiar velocities in order to test the cosmological models. These techniques include measuring cosmic flow, measuring two-point correlation and power spectrum of the peculiar velocity fields, reconstructing the density field using peculiar velocities. However, some measurements from these techniques are biased due to the non-Gaussianity of the estimated peculiar velocities. Therefore, we use the 2MTF survey to explore a power transform that can Gaussianize the estimated peculiar velocities. We find a tight linear relation between the transformation parameters and the measurement errors of log-distance ratio. To show an example for the implement of the Gaussianized peculiar velocities in cosmology, we develop a bulk flow estimator and estimate bulk flow from the Gaussianized peculiar velocities. We use 2MTF mocks to test the algorithm, we find the algorithm yields unbiased measurements. We also find this technique gives smaller measurement errors compared to other techniques. Under the Galactic coordinates, at the depth of $30$ $h^{-1}$ Mpc, we measure a bulk flow of $332\pm27$ km s$^{-1}$ in the direction $(l,b)=(293\pm 5^{\circ}, 13\pm 4^{\circ})$. The measurement is consistent with the $\Lambda$CDM prediction.

We present an analysis of the galaxy environment and physical properties of a partial Lyman limit system at z = 0.83718 with HI and metal line components closely separated in redshift space ($|\Delta v| \approx 400$ km/s) towards the background quasar HE1003+0149. The HST/COS far-ultraviolet spectrum provides coverage of lines of oxygen ions from OI to OV. Comparison of observed spectral lines with synthetic profiles generated from Bayesian ionization modeling reveals the presence of two distinct gas phases in the absorbing medium. The low-ionization phase of the absorber has sub-solar metallicities (1/10-th solar) with indications of [C/O] < 0 in each of the components. The OIV and OV trace a more diffuse higher-ionization medium with predicted HI column densities that are $\approx 2$ dex lower. The quasar field observed with VLT/MUSE reveals three dwarf galaxies with stellar masses of $M^* \sim 10^{8} - 10^{9}$ M$_\odot$, and with star formation rates of $\approx 0.5 - 1$ M$_\odot$ yr$^{-1}$, at projected separations of $\rho/R_{\mathrm{vir}} \approx 1.8 - 3.0$ from the absorber. Over a wider field with projected proper separation of $\leq 5$ Mpc and radial velocity offset of $|\Delta v| \leq 1000$ km/s from the absorber, 21 more galaxies are identified in the $VLT$/VIMOS and Magellan deep galaxy redshift surveys, with 8 of them within $1$ Mpc and $500$ km/s, consistent with the line of sight penetrating a group of galaxies. The absorber presumably traces multiple phases of cool ($T \sim 10^4$ K) photoionized intragroup medium. The inferred [C/O] < 0 hints at preferential enrichment from core-collapse supernovae, with such gas displaced from one or more of the nearby galaxies, and confined to the group medium.

We aim to constrain the mixing processes in low-mass stars by investigating the behaviour of the Li surface abundance after the main sequence. We take advantage of the data from the sixth internal data release of Gaia-ESO, idr6, and from the Gaia Early Data Release 3, edr3. We select a sample of main sequence, sub-giant, and giant stars in which Li abundance is measured by the Gaia-ESO survey, belonging to 57 open clusters with ages from 120~Myr to about 7 Gyr and to Milky Way fields, covering a range in [Fe/H] between -1.0 and +0.5dex. We study the behaviour of the Li abundances as a function of stellar parameters. We compare the observed Li behaviour in field giant stars and in giant stars belonging to individual clusters with the predictions of a set of classical models and of models with mixing induced by rotation and thermohaline instability. The comparison with stellar evolution models confirms that classical models cannot reproduce the lithium abundances observed in the metallicity and mass regimes covered by the data. The models that include the effects of both rotation-induced mixing and thermohaline instability account for the Li abundance trends observed in our sample, in all metallicity and mass ranges. The differences between the results of the classical models and of the rotation models largely differ (up to ~2 dex), making lithium the best element to constrain stellar mixing processes in low-mass stars. For stars with well-determined masses, we find a better agreement between observed surface abundances and models with rotation-induced and thermohaline mixings, the former dominating during the main sequence and the first phases of the post-main sequence evolution and the latter after the bump in the luminosity function.

General relativity probably is not the definitive theory of gravity, due a number or issues, both from the theoretical and from the observational point of view. Alternative theories of gravity were conceived to extend general relativity and account for such issues. Among the most promising ones are scalar-tensor theories, which predict an enrichment of the phenomenology of compact objects, like neutron stars. We updated the well-tested XNS code to numerically solve the Einstein-Maxwell equations for a stationary, magnetised neutron star in a class of scalar-tensor theories containing the spontaneous scalarisation phenomenon. We found that there exist "quasi-universal relations" among the mass, radius, scalar charge and magnetic deformation of a neutron star that are true independently of the equation of state, both in general relativity and in scalar-tensor theories. This result could potentially provide new tools to test scalar-tensor theories and the magnetic field geometry inside neutron stars.

The aim of the project is to identify wide common proper motion companions to a sample of spectroscopically confirmed M and L metal-poor dwarfs (also known as subdwarfs) to investigate the impact of metallicity on the binary fraction of low-mass metal-poor binaries and to improve the determination of their metallicity from the higher-mass binary. We made use of Virtual Observatory tools and large-scale public surveys to look in Gaia for common proper motion companions to a well-defined sample of ultracool subdwarfs with spectral types later than M5 and metallicities below or equal to $-$0.5 dex. We collected low-resolution optical spectroscopy for our best system, which is a binary composed of one sdM1.5 subdwarf and one sdM5.5 subdwarf located at $\sim$1,360 au, and for another two likely systems separated by more than 115,000 au. We confirm one wide companion to an M subdwarf, and infer a multiplicity for M subdwarfs (sdMs) of $1.0_{-1.0}^{+2.0}$% for projected physical separations of up to 743,000 au. We also find four M$-$L systems, three of which are new detections. No colder companion was identified in any of the 219 M and L subdwarfs of the sample, mainly because of limitations on the detection of faint sources with Gaia. We infer a frequency of wide systems for sdM5$-$9.5 of $0.60_{-0.60}^{+1.17}$% for projected physical separations larger than 1,360 au (up to 142,400 au). This study shows a multiplicity rate of $1.0_{-1.0}^{+2.0}$% in sdMs, and $1.9_{-1.9}^{+3.7}$% in extreme M subdwarfs (esdMs). We did not find any companion for the ultra M subdwarfs (usdMs) of our sample, establishing an upper limit of 5.3% on binarity for these objects.

We present the detection and characterisation of mesoscale waves on the lower clouds of Venus using images from the Visible Infrared Thermal Imaging Spectrometer onboard the European Venus Express space mission and from the 2 $\mu$m camera (IR2) instrument onboard the Japanese space mission Akatsuki. We used image navigation and processing techniques based on contrast enhancement and geometrical projections to characterise morphological properties of the detected waves, such as horizontal wavelength and the relative optical thickness drop between crests and troughs. Additionally, we performed phase velocity and trajectory tracking of wave packets. We combined these observations to derive other properties of the waves such as the vertical wavelength of detected packets. Our observations include 13 months of data from August 2007 to October 2008, and the entire available data set of IR2 from January to November 2016.We characterised almost 300 wave packets across more than 5500 images over a broad region of the globe of Venus. Our results show a wide range of properties and are not only consistent with previous observations but also expand upon them, taking advantage of two instruments that target the same cloud layer of Venus across multiple periods. In general, waves observed on the nightside lower cloud are of a larger scale than the gravity waves reported in the upper cloud. This paper is intended to provide a more in-depth view of atmospheric gravity waves on the lower cloud and enable follow-up works on their influence in the general circulation of Venus.

The direct detection of exoplanets with high-contrast instruments can be boosted with high spectral resolution. For integral field spectrographs yielding hyperspectral data, this means that the field of view consists of diffracted starlight spectra and a spatially localized planet. Analysis usually relies on cross-correlation with theoretical spectra. In a purely blind-search context, this supervised strategy can be biased with model mismatch and/or be computationally inefficient. Using an approach that is inspired by the remote-sensing community, we aim to propose an alternative to cross-correlation that is fully data-driven, which decomposes the data into a set of individual spectra and their corresponding spatial distributions. This strategy is called spectral unmixing. We used an orthogonal subspace projection to identify the most distinct spectra in the field of view. Their spatial distribution maps were then obtained by inverting the data. These spectra were then used to break the original hyperspectral images into their corresponding spatial distribution maps via non-negative least squares. The performance of our method was evaluated and compared with a cross-correlation using simulated hyperspectral data with medium resolution from the ELT/HARMONI integral field spectrograph. We show that spectral unmixing effectively leads to a planet detection solely based on spectral dissimilarities at significantly reduced computational cost. The extracted spectrum holds significant signatures of the planet while being not perfectly separated from residual starlight. The sensitivity of the supervised cross-correlation is three to four times higher than with unsupervised spectral unmixing, the gap is biased toward the former because the injected and correlated spectrum match perfectly. The algorithm was furthermore vetted on real data obtained with VLT/SINFONI of the beta Pictoris system.

We present the first measurements of the outermost edges of the Milky Way (MW) halo in terms of the depletion and turnaround radii. The inner depletion radius, $r_\mathrm{id}$, identified at the maximum infall location, separates a growing halo from the draining environment, while the turnaround radius, $r_\mathrm{ta}$, marks the outermost edge of infalling material towards the halo, both of which are located well outside the virial radius. Using the motions of nearby dwarf galaxies within $3\mathrm{Mpc}$, we obtain a marginal detection of the infall zone around the MW with a maximum velocity of $v_\mathrm{inf, max}=-46_{-39}^{+24}\mathrm{km s^{-1}}$. This enables us to measure $r_\mathrm{id}=559\pm 107 \mathrm{kpc}$ and $r_\mathrm{ta}=839\pm 121 \mathrm{kpc}$. The measured depletion radius is about 1.5 times the MW virial radius ($R_\mathrm{200m}$) measured from internal dynamics. Compared with halos in the cosmological simulation Illustris TNG100, the factor 1.5 is consistent with that of halos with similar masses and dynamical environments to the MW but slightly smaller than typical values of Local Group analogs, potentially indicating the unique evolution history of the MW. These measurements of halo edges directly quantify the ongoing evolution of the MW outer halo and provide constraints on the current dynamical state of the MW that are independent from internal dynamics.

In this paper, we quantify the ability of multiple measurements of high-redshift quasars (QSOs) to constrain several theories of modified gravity, including the Dvali-Gabadadze-Porrati braneworld scenario, generalized Chaplygin gas, $f(T)$ modified gravity, and Modified Polytropic Cardassian model. Recently released sample of 1598 quasars with X-ray and UV flux measurements in the redshift range of $0.036\leq z \leq 5.1003$, as well as a compilation of 120 intermediate-luminosity radio quasars covering the redshift of $0.46 < z < 2.76$ are respectively used as standard probes at higher redshifts. For all considered modified gravity theories, our results show that there is still some possibility that the standard $\Lambda$CDM scenario might not be the best cosmological model preferred by the current quasar observations. In order to improve cosmological constraints, the quasar data are also combined with the latest observations of baryon acoustic oscillations (BAO), which strongly complement the constraints. Finally, we discuss the support given by the data to modified gravity theories, applying different information theoretic techniques like the Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC) and Jensen-Shannon divergence (JSD).

Gamma-ray bursts (GRBs) have been phenomenologically classified into long and short populations based on the observed bimodal distribution of duration. Multi-wavelength and multi-messenger observations in recent years have revealed that in general long GRBs originate from massive star core collapse events, whereas short GRBs originate from binary neutron star mergers. It has been known that the duration criterion is sometimes unreliable, and multi-wavelength criteria are needed to identify the physical origin of a particular GRB. Some apparently long GRBs have been suggested to have a neutron star merger origin, whereas some apparently short GRBs have been attributed to genuinely long GRBs whose short, bright emission is slightly above the detector's sensitivity threshold. Here we report the comprehensive analysis of the multi-wavelength data of a bright short GRB 200826A. Characterized by a sharp pulse, this burst shows a duration of 1 second and no evidence of an underlying longer-duration event. Its other observational properties such as its spectral behaviors, total energy, and host galaxy offset, are, however, inconsistent with those of other short GRBs believed to originate from binary neutron star mergers. Rather, these properties resemble those of long GRBs. This burst confirms the existence of short duration GRBs with stellar core-collapse origin, and presents some challenges to the existing models.

Built upon a sample of 134 quasars that was dedicated to a systematic study of \mgii-BAL variability from Yi et al. (2019a), we investigate these quasars showing \mgii-BAL disappearance or emergence with the aid of at least three epoch optical spectra sampled more than 15 yr in the observed frame. We identified 3/3 quasars undergoing pristine/tentative BAL transformations. The incidence of pristine BAL transformations in the sample is therefore derived to be 2.2$_{-1.2}^{+2.2}$\%, consistent with that of high-ionization BAL transformations from the literature. Adopting an average \mgii-BAL disappearance timescale of rest-frame 6.89 yr among the six quasars, the average characteristic lifetime of \mgii\ BALs in the sample is constrained to be $>$160 yr along our line of sight. There is a diversity of BAL-profile variability observed in the six quasars, probably reflecting a variety of mechanisms at work. Our investigations of \mgii-BAL transitions, combined with observational studies of BAL transitions from the literature, imply an overall FeLoBAL/LoBAL$\rightarrow$HiBAL/non-BAL transformation sequence along with a decrease in reddening. This sequence is consistent with the evacuation models for the origin of commonly seen blue quasars, in which LoBAL quasars are in a shorted-lived, blowout phase.

Gamma-ray bursts (GRBs) are among the brightest and most energetic events in the universe. The duration and hardness distribution of GRBs has two clusters, now understood to reflect (at least) two different progenitors. Short-hard GRBs (SGRBs; T90 <2 s) arise from compact binary mergers, while long-soft GRBs (LGRBs; T90 >2 s) have been attributed to the collapse of peculiar massive stars (collapsars). The discovery of SN 1998bw/GRB 980425 marked the first association of a LGRB with a collapsar and AT 2017gfo/GRB 170817A/GW170817 marked the first association of a SGRB with a binary neutron star merger, producing also gravitational wave (GW). Here, we present the discovery of ZTF20abwysqy (AT2020scz), a fast-fading optical transient in the Fermi Satellite and the InterPlanetary Network (IPN) localization regions of GRB 200826A; X-ray and radio emission further confirm that this is the afterglow. Follow-up imaging (at rest-frame 16.5 days) reveals excess emission above the afterglow that cannot be explained as an underlying kilonova (KN), but is consistent with being the supernova (SN). Despite the GRB duration being short (rest-frame T90 of 0.65 s), our panchromatic follow-up data confirms a collapsar origin. GRB 200826A is the shortest LGRB found with an associated collapsar; it appears to sit on the brink between a successful and a failed collapsar. Our discovery is consistent with the hypothesis that most collapsars fail to produce ultra-relativistic jets.

We measured the mid-infrared (MIR) extinction using Spitzer photometry and spectroscopy (3.6--37 micron) for a sample of Milky Way sightlines (mostly) having measured ultraviolet extinction curves. We used the pair method to determine the MIR extinction that we then fit with a power law for the continuum and modified Drude profiles for the silicate features. We derived 16 extinction curves having a range of A(V) (1.8-5.5) and R(V) values (2.4-4.3). Our sample includes two dense sightlines that have 3 micron ice feature detections and weak 2175 A bumps. The average A(lambda)/A(V) diffuse sightline extinction curve we calculate is lower than most previous literature measurements. This agrees better with literature diffuse dust grain models, though it is somewhat higher. The 10 micron silicate feature does not correlate with the 2175 A bump, for the first time providing direct observational confirmation that these two features arise from different grain populations. The strength of the 10 micron silicate feature varies by $\sim$2.5 and is not correlated with A(V) or R(V). It is well fit by a modified Drude profile with strong correlations seen between the central wavelength, width, and asymmetry. We do not detect other features with limits in A(lambda)/A(V) units of 0.0026 (5--10 micron), 0.004 (10--20 micron), and 0.008 (20-40 micron). We find that the standard prescription of estimating R(V) from C times E(K_s-V)/E(B-V) has C = -1.14 and a scatter of $\sim$7%. Using the IRAC 5.6 micron band instead of K_s gives C = -1.03 and the least scatter of $\sim$3\%.

We present the first post-cosmic-microwave-background early-Universe observational constraints on $\sigma_8$, $\Omega_{\rm m}$, mean galaxy star-forming efficiency and galaxy UV magnitude scatter at redshifts $z = 4-10$. We perform a simultaneous 11-parameter cosmology and star-formation physics fit using the new code GalaxyMC, with redshift $z>4$ galaxy UV luminosity and correlation function data. Consistent with previous studies, we find evidence for redshift-independent star formation physics, regulated by halo assembly. For a flat $\Lambda$CDM universe with a low-redshift Hubble constant and a Type Ia supernovae $\Omega_{\rm m}$ prior, we constrain $\sigma_8 = 0.81 \pm 0.03$, and a mean star-forming efficiency peaking at $\log_{10} {\rm SFE} = -[(0.09 \pm 0.20) + (0.58 \pm 0.29) \times \log_{10} (1+z)]$ for halo mass $\log_{10} M_{\rm p} / h^{-1} M_{\odot} = 11.48 \pm 0.09$. The suppression of star formation due to feedback is given by a double power law in halo mass with indices $\alpha = 0.56 \pm 0.08, \beta = -1.03 \pm 0.07$. The scatter in galaxy UV magnitude for fixed halo mass is $\sigma_M = 0.56 \pm 0.08$. Without a prior on $\Omega_{\rm m}$ we obtain $\sigma_8 = 0.78 \pm 0.06$, $\Omega_{\rm m} = 0.33 \pm 0.07$ and at most $1\sigma$ differences in all other parameter values. Our best-fit galaxy luminosity functions yield a reionization optical depth $\tau \approx 0.048$, consistent with the Planck 2018 value.

The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) includes a volumetrically complete sample of 82 gas-rich dwarfs with M_HI~<10^7.2 Msun selected from the ALFALFA survey. We are obtaining extensive follow-up observations of the SHIELD galaxies to study their gas, stellar, and chemical content, and to better understand galaxy evolution at the faint end of the HI mass function. Here, we investigate the properties of 30 SHIELD galaxies using Hubble Space Telescope imaging of their resolved stars and Westerbork Synthesis Radio Telescope observations of their neutral hydrogen. We measure tip of the red giant branch (TRGB) distances, star formation activity, and gas properties. The TRGB distances are up to 4x greater than estimates from flow models, highlighting the importance of velocity-independent distance indicators in the nearby universe. The SHIELD galaxies are in under-dense regions, with 23% located in voids; one galaxy appears paired with a more massive dwarf. We quantify galaxy properties at low masses including stellar and HI masses, SFRs, sSFRs, SFEs, birthrate parameters, and gas fractions. The lowest mass systems lie below the mass thresholds where stellar mass assembly is predicted to be impacted by reionization. Even so, we find the star formation properties follow the same trends as higher mass gas-rich systems, albeit with a different normalization. The HI disks are small (<r><0.6 kpc) making it difficult to measure the HI rotation using standard techniques; we develop a new methodology and report the velocity extent, and its associated spatial extent, with robust uncertainties.

While it is known that the sharp-line star Vega (vsini ~ 20km/s) is actually a rapid rotator seen nearly pole-on with low i (< 10 deg), no consensus has yet been accomplished regarding its intrinsic rotational velocity (v_e), for which rather different values have been reported so far. Methodologically, detailed analysis of spectral line profiles is useful for this purpose, since they reflect more or less the v_e-dependent gravitational darkening effect. However, direct comparison of observed and theoretically simulated line profiles is not necessarily effective in practice, where the solution is sensitively affected by various conditions and the scope for combining many lines is lacking. In this study, determination of Vega's v_e was attempted based on an alternative approach making use of the first zero (q_1) of the Fourier transform of each line profile, which depends upon K (temperature sensitivity parameter differing from line to line) and v_e. It turned out that v_e and vsini could be separately established by comparing the observed q_1^obs and calculated q_1^cal values for a number of lines of different K. Actually, independent analysis applied to two line sets (49 Fe I lines and 41 Fe II lines) yielded results reasonably consistent with each other. The final parameters of Vega's rotation were concluded as vsini = 21.6 (+/- 0.3) km/s, v_e = 195 (+/- 15) km/s, and i = 6.4 (+/- 0.5) deg.

We present the results of a near-infrared (NIR) monitoring program carried out between 1999 and 2005 to determine the variability properties of the Arecibo sample of OH/IR stars. The sample consists of 385 IRAS-selected Asymptotic Giant Branch (AGB) candidates, for which their O-rich chemistry has been proven by the detection of 1612 MHz OH maser emission. The monitoring data was complemented by data collected from public optical and NIR surveys. We fitted the light curves obtained in the optical and NIR bands with a model using an asymmetric cosine function, and derived a period for 345 sources (90% of the sample). Based on their variability properties, most of the Arecibo sources are classified as long-period large-amplitude variable stars (LPLAV), 4% as (candidate) post-AGB stars, and 3% remain unclassified although they are likely post-AGB stars or highly obscured AGB stars. The period distribution of the LPLAVs peaks at 400 days, with periods between 300 and 800 days for most of the sources, and has a long tail up to 2100 days. Typically, the amplitudes are between 1 and 3 mag in the NIR and between 2 and 6 mag in the optical. We find correlations between periods and amplitudes, with larger amplitudes associated to longer periods, as well as between the period and the infrared colours, with the longer periods linked to the redder sources. Among the post-AGB stars, the light curve of IRAS 19566+3423 was exceptional, showing a large systematic increase in K-band brightness over 7 years.

We have adapted the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) Science Pipelines to process data from the Gravitational-Wave Optical Transient Observer (GOTO) prototype. In this paper, we describe how we used the Rubin Observatory LSST Science Pipelines to conduct forced photometry measurements on nightly GOTO data. By comparing the photometry measurements of sources taken on multiple nights, we find that the precision of our photometry is typically better than 20~mmag for sources brighter than 16 mag. We also compare our photometry measurements against colour-corrected PanSTARRS photometry, and find that the two agree to within 10~mmag (1$\sigma$) for bright (i.e., $\sim14^{\rm th}$~mag) sources to 200~mmag for faint (i.e., $\sim18^{\rm th}$~mag) sources. Additionally, we compare our results to those obtained by GOTO's own in-house pipeline, {\sc gotophoto}, and obtain similar results. Based on repeatability measurements, we measure a $5\sigma$ L-band survey depth of between 19 and 20 magnitudes, depending on observing conditions. We assess, using repeated observations of non-varying standard SDSS stars, the accuracy of our uncertainties, which we find are typically overestimated by roughly a factor of two for bright sources (i.e., $<15^{\rm th}$~mag), but slightly underestimated (by roughly a factor of 1.25) for fainter sources ($>17^{\rm th}$~mag). Finally, we present lightcurves for a selection of variable sources, and compare them to those obtained with the Zwicky Transient Factory and GAIA. Despite the Rubin Observatory LSST Science Pipelines still undergoing active development, our results show that they are already delivering robust forced photometry measurements from GOTO data.

Recent rapid progress in multimessenger observations of neutron stars (NSs) offers great potential to constrain the properties of strongly interacting matter under the most extreme conditions. In order to fully exploit the current observational inputs and to study the impact of future observations, we analyze a large ensemble of randomly generated model-independent equations of state (EoSs) and the corresponding rotating stellar structures without the use of quasi-universal relations. We discuss the compatibility and the impact on the EoS of various hypotheses and measurements, including those involving the merger product in GW170817, the binary merger components in GW190814, and radius measurements of PSR J0740+6620. We obtain an upper limit for the dimensionless spin of a rigidly rotating NS, |chi| < 0.84, and find that the conservative hypothesis that the remnant in GW170817 ultimately collapsed to a black hole strongly constrains the EoS and the maximal mass of NSs, implying M_TOV < 2.53M_sol (or M_TOV < 2.19M_sol if we assume that a hypermassive NS was created). Furthermore, we find that radius measurements of massive NSs stars can dramatically limit the EoS, with strict lower limits around 12 km and above offering particularly efficient constraints. Finally, we find that radius values for a two-solar mass NS around 11-13 km would be completely compatible with the presence of quark matter inside massive NSs.

On Saturday 26 September, around 4am, John Barrow died aged 67, with his wife Elizabeth and son Roger at his side. From a scientific perspective, it is hard to conceive a more premature end. During lockdown alone, whilst undergoing chemotherapy and in the full knowledge that his cancer was inoperable, John managed to co-author 11 scientific papers and write a new book ("One Plus One"). Even by his own standards of productivity, this is staggeringly impressive, an achievement he was openly proud of. From a broader perspective, with a wife, 3 children and 5 young grandchildren, many strong friendships, and so much more to offer the world, he departed far too soon.

Light curves of type I X-ray bursts, also known as photospheric radius expansion (PRE) bursts, have been used as standard candles to estimate the "nominal PRE distances" for 63% of PRE bursters (bursters), assuming PRE bursts are spherically symmetric. Model-independent geometric parallaxes of bursters provide a valuable chance to test models of PRE bursts (PRE models), and can be provided in some cases by Gaia astrometry of the donor stars in bursters. We searched for counterparts to 115 known bursters in the Gaia Early Data Release 3, and confirmed 4 bursters with Gaia counterparts that have detected (>3sigma, prior to zero-point correction) parallaxes. We describe a generic approach to the Gaia parallax zero point as well as its uncertainty using an ensemble of Gaia quasars individually determined for each target. Assuming the spherically symmetric PRE model is correct, we refined the resultant nominal PRE distances of three bursters (i.e. Cen X-4, Cyg X-2 and 4U 0919-54), and put constraints on their compositions of the nuclear fuel powering the bursts. Finally, we describe a method for testing the correctness of the spherically symmetric PRE model using parallax measurements, and provide preliminary results.

We present deep, narrowband imaging of the nearby spiral galaxy M101 and its group environment to search for star-forming dwarf galaxies and outlying HII regions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, H$\alpha$, H$\beta$, and [OIII], to detect potential outlying star-forming regions. Our survey covers $\sim$6 square degrees around M101, and we detect objects in emission down to an H$\alpha$ flux level of $5.7 \times 10^{-17}$ erg s$^{-1}$ cm$^{-2}$ (equivalent to a limiting SFR of $1.7 \times 10^{-6}$ $M_\odot$ yr$^{-1}$ at the distance of M101). After careful removal of background contaminants and foreground M stars, we detect 19 objects in emission in all three bands, and 8 objects in emission in H$\alpha$ and [OIII]. We compare the structural and photometric properties of the detected sources to Local Group dwarf galaxies and star-forming galaxies in the 11HUGS and SINGG surveys. We find no large population of outlying HII regions or undiscovered star-forming dwarfs in the M101 Group, as most sources (93%) are consistent with being M101 outer disk HII regions. Only two sources were associated with other galaxies: a faint star-forming satellite of the background galaxy NGC 5486, and a faint outlying HII region near the M101 companion NGC 5474. We also find no narrowband emission associated with recently discovered ultradiffuse galaxies and starless HI clouds near M101. The lack of any hidden population of low luminosity star-forming dwarfs around M101 suggests a rather shallow faint end slope (as flat as $\alpha \sim -1.0$) for the star-forming luminosity function in the M101 Group. We discuss our results in the context of tidally-triggered star formation models and the interaction history of the M101 Group.

The astrophysical sites where r-process elements are synthesized remain mysterious: it is clear that neutron-star mergers (kilonovae, KNe) contribute, and some classes of core-collapse supernovae (SNe) are also likely sources of at least the lighter r-process species. The discovery of the live isotope Fe60 on the Earth and Moon implies that one or more astrophysical explosions occurred near the Earth within the last few Myr, probably a SN. Intriguingly, several groups have reported evidence for deposits of Pu244, some overlapping with the Fe60 pulse. However, the putative Pu244 flux appears to extend to at least 12 Myr ago, pointing to a different origin. Motivated by this observation, we propose that ejecta from a KN enriched the giant molecular cloud that gave rise to the Local Bubble in which the Sun resides. Accelerator Mass Spectrometry (AMS) measurements of Pu244 and searches for other live isotopes could probe the origins of the r-process and the history of the solar neighborhood, including triggers for mass extinctions, e.g., at the end of the Devonian epoch, motivating the calculations of the abundances of live r-process radioisotopes produced in SNe and KNe that we present here. Given the presence of Pu244, other r-process species such as Zr93, Pd107, I129, Cs135, Hf182, U236, Np237 and Cm247 should be present. Their abundances could distinguish between SN and KN scenarios, and we discuss prospects for their detection in deep-ocean deposits and the lunar regolith. We show that AMS I129 measurements in Fe-Mn crusts already constrain a possible nearby KN scenario.

We present the Democratic Samples of Supernovae (DSS), a compilation of 775 low-redshift Type Ia and II supernovae (SNe Ia & II), of which 137 SN Ia distances are derived via the newly developed snapshot distance method. Using the objects in the DSS as tracers of the peculiar-velocity field, we compare against the corresponding reconstruction from the 2M++ galaxy redshift survey. Our analysis -- which takes special care to properly weight each DSS subcatalogue and cross-calibrate the relative distance scales between them -- results in a measurement of the cosmological parameter combination $f\sigma_8 = 0.390_{-0.022}^{+0.022}$ as well as an external bulk flow velocity of $195_{-23}^{+22}$ km s$^{-1}$ in the direction $(\ell, b) = (292_{-7}^{+7}, -6_{-4}^{+5})$ deg, which originates from beyond the 2M++ reconstruction. Similarly, we find a bulk flow of $245_{-31}^{+32}$ km s$^{-1}$ toward $(\ell, b) = (294_{-7}^{+7}, 3_{-5}^{+6})$ deg on a scale of $\sim 30 h^{-1}$ Mpc if we ignore the reconstructed peculiar-velocity field altogether. Our constraint on $f\sigma_8$ -- the tightest derived from SNe to date (considering only statistical error bars), and the only one to utilise SNe II -- is broadly consistent with other results from the literature. We intend for our data accumulation and treatment techniques to become the prototype for future studies that will exploit the unprecedented data volume from upcoming wide-field surveys.

Water maser emitting planetary nebulae (H$_2$O-PNe) are believed to be among the youngest PNe. We present new optical narrow- and broad-band images, intermediate- and high-resolution long-slit spectra, and archival optical images of the H$_2$O-PN IRAS 18061--2505. It appears a pinched-waist bipolar PN consisting of knotty lobes with some point-symmetric regions, a bow-shock near the tip of each lobe, and a very compact inner nebula where five components are identified in the spectra by their kinematic and emission properties. The water masers most probably reside in an oxygen-rich ring tracing the equatorial region of the bipolar lobes. These two structures probably result from common envelope evolution plus several bipolar and non-bipolar collimated outflows that have distorted the lobes. The bow-shocks could be related to a previous phase to that of common envelope. The inner nebula may be attributed to a late or very late thermal pulse that occurred before 1951.6 when it was not detectable in the POSSI-Blue image. Chemical abundances and other properties favour a 3--4 M$_{\odot}$ progenitor, although if the common envelope phase accelerated the evolution of the central star, masses <1.5 M$_{\odot}$ cannot be discarded. The age of the bipolar lobes is incompatible with the existence of water masers in IRAS 18061--2505, which may have been lately reactivated through shocks in the oxygen-rich ring, that are generated by the thermal pulse, implying that this PN is not extremely young. We discuss H$_2$O-PNe and possibly related objects in the light of our results for IRAS 18061--2505.

A number of challenges of the standard $\Lambda$CDM model has been emerging during the past few years as the accuracy of cosmological observations improves. In this review we discuss in a unified manner many existing signals in cosmological and astrophysical data that appear to be in some tension ($2\sigma$ or larger) with the standard $\Lambda$CDM model as defined by the Planck18 parameter values. In addition to the major well studied $5\sigma$ challenge of \lcdm (the Hubble $H_0$ crisis) and other well known tensions (the growth tension and the lensing amplitude $A_L$ anomaly), we discuss a wide range of other less discussed less-standard signals which appear at a lower statistical significance level than the $H_0$ tension (also known as 'curiosities' in the data) which may also constitute hints towards new physics. For example such signals include cosmic dipoles (the fine structure constant $\alpha$, velocity and quasar dipoles), CMB asymmetries, BAO Ly$\alpha$ tension, age of the Universe issues, the Lithium problem, small scale curiosities like the core-cusp and missing satellite problems, quasars Hubble diagram, oscillating short range gravity signals etc. The goal of this pedagogical review is to collectively present the current status of these signals and their level of significance, with emphasis to the Hubble crisis and refer to recent resources where more details can be found for each signal. We also briefly discuss possible theoretical approaches that can potentially explain the non-standard nature of some of these signals.

Fast-rotating pulsars and magnetars have been suggested as the central engines of super-luminous supernovae (SLSNe) and fast radio bursts, and this scenario naturally predicts non-thermal synchrotron emission from their nascent pulsar wind nebulae (PWNe). We report results of high-frequency radio observations with ALMA and NOEMA for three SLSNe (SN 2015bn, SN 2016ard, and SN 2017egm), and present a detailed theoretical model to calculate non-thermal emission from PWNe with an age of about 1-3 yr. We find that the ALMA data disfavors a PWN model motivated by the Crab nebula for SN 2015bn and SN 2017egm, and argue that this tension can be resolved if the nebular magnetization is very high or very low. Such models can be tested by future MeV-GeV gamma-ray telescopes such as AMEGO.

The dark photon is a massive hypothetical particle that interacts with the Standard Model by kinetically mixing with the visible photon. For small values of the mixing parameter, dark photons can evade cosmological bounds to be a viable dark matter candidate. Due to the similarities with the electromagnetic signals generated by axions, several bounds on dark photon signals are simply reinterpretations of historical bounds set by axion haloscopes. However, the dark photon has a property that the axion does not: an intrinsic polarisation. Due to the rotation of the Earth, accurately accounting for this polarisation is nontrivial, and highly experiment-dependent. We show that if one does account for this polarisation, and the rotation of the Earth, experimental sensitivity to the dark photon's kinetic mixing parameter can be improved by over an order of magnitude. We detail the strategies that would need to be taken to properly optimise a dark photon search. These include judiciously choosing the location and orientation of the experiment, as well as strategically timing any repeated measurements. We also point out that several well-known searches for axions employ techniques for testing signals that preclude their ability to set exclusion limits on dark photons, and hence should not be reinterpreted as such.

The Event Horizon Telescope (EHT) with unprecedented angular resolution opens exciting opportunities to search for new physics beyond the particle Standard Model. Recently, the polarization properties of the radiation near the supermassive black hole M87$^\star$ are measured in four individual days. This is exactly what is needed to test the existence of a dense axion cloud produced from extracting the black hole spinning energy by the superradiance mechanism. The presence of the axion cloud leads to a frequency independent oscillation to the electric vector position angle (EVPA) of the linearly polarized radiation. For M87$^\star$, which is approximately face-on, such an oscillation of the EVPA appears as a propagating wave along the azimuthal angle on the sky. In this paper, we apply the azimuthal distribution of EVPA measured by the EHT and study the axion-photon coupling. We propose a novel differential analysis procedure to minimize the astrophysical background and derive stringent constraints on the axion parameters. The EHT data can rule out a considerable portion of the axion parameter space for axion mass window $\sim (10^{-21}-10^{-20})$~eV, which was unexplored by previous experiments.

New observational data of neutron stars since GW170817 have helped improve our knowledge about nuclear symmetry energy especially at high densities. We have learned particularly: (1) The slope parameter $L$ of nuclear symmetry energy at saturation density $\rho_0$ of nuclear matter from 24 new analyses is about $L\approx 57.7\pm 19$ MeV at 68\% confidence level consistent with its fiducial value, (2) The curvature $K_{\rm{sym}}$ from 16 new analyses is about $K_{\rm{sym}}\approx -107\pm 88$ MeV, (3) The magnitude of nuclear symmetry energy at $2\rho_0$, i.e. $E_{\rm{sym}}(2\rho_0)\approx 51\pm 13$ MeV at 68\% confidence level, has been extracted from 9 new analyses of neutron star observables consistent with results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories, (4) while the available data from canonical neutron stars do not provide tight constraints on nuclear symmetry energy at densities above about $2\rho_0$, the lower radius boundary $R_{2.01}=12.2$ km from NICER's very recent observation of PSR J0740+6620 of mass $2.08\pm 0.07$ $M_{\odot}$ and radius $R=12.2-16.3$ km at 68\% confidence level sets a tight lower limit for nuclear symmetry energy at densities above $2\rho_0$, (5) Bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars indicate that the phase transition shift appreciably both the $L$ and $K_{\rm{sym}}$ to higher values but with larger uncertaintie , (6) The high-density behavior of nuclear symmetry energy affects significantly the minimum frequency necessary to rotationally support GW190814's secondary component of mass (2.50-2.67) $M_{\odot}$ as the fastest and most massive pulsar discovered so far.

String length is a fundamental parameter in string theory. A strategy on how to determine it through experiments is proposed. Our work focuses on the stochastic gravitational waves from string gas cosmology. With the help of the Lambert W function, we find the non-Hagedorn phase is ruled out by the B-mode polarization in the cosmic microwave background. The spectrum from the Hagedorn phase with a logarithmic term is found to be unique. We propose a strategy on how to constrain the string length through stochastic gravitational waves. Considering the sensitivities of the current and the upcoming detectors, the string length is found to be lower than 7 $\sim$ orders of the Planck scale.

The information conservation principle is probed for classically isolated systems, like the Hubble sphere and black holes, for which the rise of entanglement entropy across their horizons is expected. We accept the analog of Landauer's principle that entanglement information should introduce some negative potential energy, which corresponds to the positive energy of measurements that destroy this quantum behavior. We estimated these dark-energy-like contributions and found that they can explain the dark energy of the Universe and also are able to resolve the observed superluminal motion and redshift controversies for black holes.

We study the charge of the 4D-Einstein-Gauss-Bonnet black hole by a negative charge and a positive charge of a particle-antiparticle pair on the horizons r- and r+, respectively. We show that there are two types of the Schwarzschild black hole. We show also that the Einstein-Gauss-Bonnet black hole charge has quantified values. We obtain the Hawking-Bekenstein formula with two logarithmic corrections, the second correction depends on the cosmological constant and the black hole charge. Finally, we study the thermodynamics of the EGB-AdS black hole.

Quantum gravity is a challenge in physics, and the existence of graviton is the prime question. We study the detectability of the quantum noise induced by gravitons. With the squeezed factor fixed properly, a spectrum of the quantum noise in the squeezed state of the form $\Omega_0 \sim \nu^{4+a_0 \beta+b_0}$ is found. Compared to the sensitivities of several gravitational wave detectors, we conclude that the quantum noise might be detected in the future.

We provide strong observational evidence for a multimode black hole ringdown spectrum, using the gravitational wave event GW190521. We show strong evidence for the presence of at least two ringdown modes, with a Bayes factor of $43.4^{+8.1}_{-6.8}$ preferring two modes over one. The dominant mode is the fundamental $\ell=m=2$ harmonic, and the sub-dominant mode corresponds to the fundamental $\ell=m=3$ harmonic. We estimate the redshifted mass and dimensionless spin of the final black hole as $332^{+31}_{-35}\,M_\odot$ and $0.871^{+0.052}_{-0.096}$ respectively. The detection of the two modes disfavors a binary progenitor with equal masses, and the mass ratio is constrained to $0.45^{+0.22}_{-0.29}$. General relativity predicts that the frequency and damping time of each mode in the spectrum depends only on two parameters, the black hole mass and angular momentum. Consistency between the different modes thus provides a test of general relativity. As a test of the black hole no-hair theorem, we constrain the fractional deviation of the sub-dominant mode frequency from the Kerr prediction to $\delta f_{330} = -0.010^{+0.073}_{-0.121}$