Papers for Thursday, May 04 2023

We present five far- and near-ultraviolet spectra of the Type II plateau supernova, SN 2022acko, obtained 5, 6, 7, 19, and 21 days after explosion, all observed with the Hubble Space Telescope/Space Telescope Imaging Spectrograph. The first three epochs are earlier than any Type II plateau supernova has been observed in the far-ultraviolet revealing unprecedented characteristics. These three spectra are dominated by strong lines, primarily from metals, which contrasts with the relatively featureless early optical spectra. The flux decreases over the initial time series as the ejecta cools and line-blanketing takes effect. We model this unique dataset with the non-local thermodynamic equilibrium radiation transport code CMFGEN, finding a good match to the explosion of a low mass red supergiant with energy Ekin = 6 x 10^50 erg. With these models we identify, for the first time, the ions that dominate the early UV spectra. We also present optical photometry and spectroscopy, showing that SN 2022acko has a peak absolute magnitude of V = -15.4 mag and plateau length of ~115d. The spectra closely resemble those of SN 2005cs and SN 2012A. Using the combined optical and UV spectra, we report the fraction of flux redwards of the uvw2, U, B, and V filters on days 5, 7, and 19. We also create a spectral time-series of Type II supernovae in the ultraviolet, demonstrating the rapid decline of UV flux over the first few weeks of evolution. Future observations of Type II supernovae will continue to explore the diversity seen in the limited set of high-quality UV spectra.

The motion of an observer in the rest frame of the cosmic 21-cm background induces an anisotropy in the observed background, even when the background is isotropic. The induced anisotropy includes a dipole and a quadrupole, in the order decreasing in amplitude. If observed, these multipole anisotropies can be used as additional probes of the spectral shape of the global 21-cm background for mitigating the ambiguity in the monopole spectrum probed by single-element radio telescopes such as EDGES and SARAS. This could also help with understanding the astrophysical and cosmological processes that occurred during the cosmic dawn and the epoch of reionization, and even improving on the estimation of the solar velocity and the foreground spectra. Here, we study the feasibility of such observations and present science drivers for the measurement of the 21-cm dipole and quadrupole.

A star destroyed by a supermassive black hole (SMBH) in a tidal disruption event (TDE) is transformed into a filamentary structure known as a tidally disrupted stellar debris stream. We show that when ideal gas pressure dominates the thermodynamics of the stream, there is an exact solution to the hydrodynamics equations that describes the stream evolution and accounts for self-gravity, pressure, the dynamical expansion of the gas, and the transverse structure of the stream. We analyze the stability of this solution to cylindrically symmetric perturbations, and show that there is a critical stream density below which the stream is unstable and is not self-gravitating; this critical density is a factor of at least 40-50 smaller than the stream density in a TDE. Above this critical density the stream is overstable, self-gravity confines the stream, the oscillation period is exponentially long, and the growth rate of the overstability scales as $t^{1/6}$. The power-law growth and small power-law index of the overstability implies that the stream is effectively stable to cylindrically symmetric perturbations. We also use this solution to analyze the effects of hydrogen recombination, and suggest that even though recombination substantially increases the gas entropy, it is likely incapable of completely destroying the influence of self-gravity. We also show that the transient produced by recombination is far less luminous than previous estimates.

Surveys have looked for H alpha emission from accreting gas giants but found very few objects. Analyses of the detections and non-detections have assumed that the entire gas flow feeding the planet is in radial free-fall. However, hydrodynamical simulations suggest that this is far from reality. We calculate the H alpha emission from multidimensional accretion onto a gas giant, following the gas flow from Hill-sphere scales down to the circumplanetary disc (CPD) and the planetary surface. We perform azimuthally-symmetric radiation-hydrodynamics simulations around the planet and use modern tabulated gas and dust opacities. Crucially, contrasting with most previous simulations, we do not smooth the gravitational potential and do follow the flow down to the planetary surface, where grid cells are 0.01 Jupiter radii small radially. We find that only roughly one percent of the net gas inflow into the Hill sphere reaches directly the planet. As expected for ballistic infall trajectories, most of the gas falls at too large a distance on the CPD to generate H alpha. Including radiation transport removes the high-velocity sub-surface flow previously seen in hydrodynamics-only simulations, so that only the free planet surface and the inner regions of the CPD emit substantially H alpha. Unless magnetospheric accretion, which we neglect here, additionally produces H alpha, the corresponding H alpha production efficiency is much smaller than usually assumed, which needs to be taken into account when analysing (non-)detection statistics.

Recent observations with the James Webb Space Telescope (JWST) are yielding tantalizing hints of an early population of massive, bright galaxies at $z > 10$, with Atacama Large Millimeter Array (ALMA) observations indicating significant dust masses in place as early as $z\sim 7$. To understand the implications of these observations, we use the DELPHI semi-analytic model that jointly tracks the assembly of dark matter halos and their constituent baryons, including the key processes of dust enrichment. Our model employs only two redshift- and mass-independent free parameters that are tuned against all available galaxy data at $z \sim 5-9$ before it is used to make predictions up to $z \sim 20$. Our key results are: (1) the model progressively under-predicts the observed ultraviolet luminosity function (UV LF) at $z > 12$; observations at $z>16$ lie close to, or even above, a "maximal" model where all available gas is turned into stars; (2) UV selection would miss 34% of the star formation rate density at $z \sim 5$, decreasing to 17% by $z \sim 10$ for bright galaxies with $\rm{M_{UV}} < -19$; (3) the dust mass ($M_d$) evolves with the stellar mass ($M_*$) and redshift as $\log(M_d) = 1.194\log(M_*) + 0.0975z - 5.433$; (4) the escape fraction of UV photons ($f_{\rm esc}^{\rm UV}$) decreases with increasing mass and star formation rate. At $z \sim 7$, $f_{\rm esc}^{\rm UV} \sim 0.8~(0.1)$ for $M_* \sim 10^9~ (10^{11}) \, M_\odot$ galaxies; (5) the dust temperature increases with stellar mass, ranging between $30-33$ K for $M_* \sim 10^{9-11}M_\odot$ galaxies at $z \sim 7$. Finally, we predict the far infrared (FIR) LF at $z \sim 5-20$, testable with ALMA observations, and caution that spectroscopic redshifts and dust masses must be pinned down before invoking unphysical extrema in galaxy formation models.

Numerical integrations of the Solar System reveal a remarkable stability of the orbits of the inner planets over billions of years, in spite of their chaotic variations characterized by a Lyapunov time of only 5 million years and the lack of integrals of motion able to constrain their dynamics. To open a window on such long-term behavior, we compute the entire Lyapunov spectrum of a forced secular model of the inner planets. We uncover a hierarchy of characteristic exponents that spans two orders of magnitude, manifesting a slow-fast dynamics with a broad separation of timescales. A systematic analysis of the Fourier harmonics of the Hamiltonian, based on computer algebra, reveals three symmetries that characterize the strongest resonances responsible for the orbital chaos. These symmetries are broken only by weak resonances, leading to the existence of quasi-integrals of motion that are shown to relate to the smallest Lyapunov exponents. A principal component analysis of the orbital solutions independently confirms that the quasi-integrals are among the slowest degrees of freedom of the dynamics. Strong evidence emerges that they effectively constrain the chaotic diffusion of the orbits, playing a crucial role in the statistical stability over the Solar System lifetime.

The hunt is on for dozens of protoplanets hypothesised to reside in protoplanetary discs with imaged gaps. How bright these planets are, and what they will grow to become, depend on their accretion rates, which may be in the runaway regime. Using 3D global simulations we calculate maximum gas accretion rates for planet masses $M_{\rm p}$ from 1$\,M_{\oplus}$ to $10\,M_{\rm J}$. When the planet is small enough to be fully embedded in the disc, with a Bondi radius $r_{\rm Bondi}$ smaller than the disc's scale height $H_{\rm p}$ -- such planets have thermal mass parameters $q_{\rm th} \equiv (M_{\rm p}/M_{\star}) / (H_{\rm p}/R_{\rm p})^3 \lesssim 0.5$, for host stellar mass $M_{\star}$ and orbital radius $R_{\rm p}$ -- the maximum accretion rate follows a Bondi scaling, with $\max \dot{M}_{\rm p} \propto M_{\rm p}^2 / (H_{\rm p}/R_{\rm p})^3$. For more massive planets with $0.5 \lesssim q_{\rm th} \lesssim 10$, the Hill sphere replaces the Bondi sphere as the gravitational sphere of influence, and $\max \dot{M}_{\rm p} \propto M_{\rm p}^1$, with no dependence on $H_{\rm p}/R_{\rm p}$. In the strongly superthermal limit when $q_{\rm th} \gtrsim 10$, the Hill sphere pops well out of the disc and $\max \dot{M}_{\rm p} \propto M_{\rm p}^{2/3} (H_{\rm p}/R_{\rm p})^1$. Applied to the two confirmed protoplanets PDS 70b and c, our numerically calibrated maximum accretion rates imply their Jupiter-like masses may increase by up to a factor of $\sim$2 before their parent disc dissipates.

Ultraluminous X-ray sources (ULXs) are our best laboratories for studying extreme super-Eddington accretion. Most studies of these objects are of relatively persistent sources, however there is growing evidence to suggest a large fraction of these sources are transient. Here we present a sample of five newly reported transient ULXs in the galaxies NGC 4945, NGC 7793 and M81 serendipitously discovered in Swift/XRT observations. Swift monitoring of these sources have provided well sampled lightcurves, allowing for us to model the lightcurves with the disk instability model of Hameury & Lasota (2020) which implies durations of 60-400 days and that the mass accretion rate through the disk is close to or greater than the Eddington rate. Of the three source regions with prior HST imaging, color magnitude diagrams of the potential stellar counterparts show varying ages of the possible stellar counterparts. Our estimation of the rates of these sources in these three galaxies is 0.4-1.3 year$^{-1}$. We find that while persistent ULXs dominate the high end of galaxy luminosity functions, the number of systems that produce ULX luminosities are likely dominated by transient sources.

AT 2021loi is an optical-ultraviolet transient located at the center of its host galaxy. Its spectral features identify it as a member of the ``Bowen Fluorescence Flare'' (BFF) class. The first member of this class was considered to be related to a tidal disruption event, but enhanced accretion onto an already active supermassive black hole was suggested as an alternative explanation. AT 2021loi, having occurred in a previously-known unobscured AGN, strengthens the latter interpretation. Its light curve is similar to those of previous BFFs, showing a rebrightening approximately one year after the main peak (which was not explicitly identified, but might be the case, in all previous BFFs). An emission feature around 4680 A, seen in the pre-flare spectrum, strengthens by a factor of $\sim$2 around the optical peak of the flare, and is clearly seen as a double peaked feature then, suggesting a blend of NIII $\lambda 4640$ with HeII $\lambda4686$ as its origin. The appearance of OIII $\lambda$3133 and possible NIII $\lambda\lambda4097,4103$ (blended with H$\delta$) during the flare further support a Bowen Fluorescence classification. Here, we present ZTF, ATLAS, Keck, Las Cumbres Observatory, NEOWISE-R, $Swift$, AMI and VLA observations of AT 2021loi, making it one of the best observed BFFs to date. AT 2021loi thus provides some clarity on the nature of BFFs but also further demonstrates the diversity of nuclear transients.

This Technical Note presents a catalog of calibrated reference stars that was generated by the Forward Calibration Method (FGCM) pipeline (arXiv:1706.01542) as part of the FGCM photometric calibration of the full Dark Energy Survey (DES) 6-Year data set (Y6). This catalog provides DES grizY magnitudes for 17 million stars with i-band magnitudes mostly in the range 16 < i < 21 spread over the full DES footprint covering 5000 square degrees over the Southern Galactic Cap at galactic latitudes b < -20 degrees (plus a few outlying fields disconnected from the main survey footprint). These stars are calibrated to a uniformity of better than 1.8 milli-mag (0.18%) RMS over the survey area. The absolute calibration of the catalog is computed with reference to the STISNIC.007 spectrum of the Hubble Space Telescope CalSpec standard star C26202; including systematic errors, the absolute flux system is known at the approximately 1% level. As such, these stars provide a useful reference catalog for calibrating grizY-band or grizY-like band photometry in the Southern Hemisphere, particularly for observations within the DES footprint.

Multiple parametric limb-darkening laws have been presented, and there are many available sources of theoretical limb-darkening coefficients (LDCs) calculated using stellar model atmospheres. The power-2 limb-darkening law allows a very good representation of theoretically predicted intensity profiles, but few LDCs are available for this law from spherically symmetric model atmospheres. We therefore present such coefficients in this work. We computed LDCs for the space missions \textit{Gaia}, \textit{Kepler}, TESS, and CHEOPS and for the passbands $uvby$, $UBVRIJHK$, and SDSS $ugriz$, using the \textsc{phoenix-cond} spherical models. We adopted two methods to characterise the truncation point, which sets the limb of the star: the first (M1) uses the point where the derivative d$I(r)$/d$r$ is at its maximum where I(r) is the specific intensity as a function of the normalised radius r corresponding to $\mu_{\rm cri}$, and the second (M2) uses the midpoint between the point $\mu_{\rm cri}$ and the point located at $\mu_{\rm cri-1}$. The LDCs were computed adopting the Levenberg-Marquardt least-squares minimisation method, with a resolution of 900 equally spaced $\mu$ points, and covering 823 model atmospheres for a solar metallicity, effective temperatures of 2300 to 12000\,K, $\log g$ values from 0.0 to 6.0, and microturbulent velocities of 2\,km\,s$^{-1}$. As our previous calculations of LDCs using spherical models included only 100 $\mu$ points, we also updated the calculations for the four-parameter law for the passbands listed above, and compared them with those from the power-2 law. Comparisons between the quality of the fits provided by the power-2 and four-parameter laws show that the latter presents a lower merit function, $\chi^2$, than the former for both cases (M1 and M2). This is important when choosing the best approach for a particular science goal.

Stellar counter-rotation in disk galaxies directly relates to the complex phenomenon of the disk mass assembly believed to be driven by external processes, such as accretion and mergers. The detailed study of such systems makes it possible to reveal the source of external accretion and establish the details of this process. In this paper, we investigate the galaxy PGC 66551 (MaNGA ID~1-179561) which hosts two large-scale counter-rotating stellar disks suspected in the SDSS MaNGA data and then confirmed using deep follow-up spectroscopy with the 10-m Southern African Large Telescope. We measured properties of ionized gas and stellar populations of both counter-rotating disks in PGC 66551. We found that the counter-rotating disk is compact, contains young stars with subsolar metallicity, and has a stellar mass $5\times10^{9}$ M$_\odot$ which amounts to $\approx$20\% of the galaxy's total. Surprisingly, the main 8 Gyr old disk has a significantly lower metallicity -0.8 dex than other counter-rotating galaxies. We developed a simple analytic model for the metal enrichment history, which we applied to PGC 66551 and constrained the parameters of the galactic outflow wind and estimated the metallicity of the infalling gas that formed the counter-rotating disk to be $-0.9 ... -0.5$ dex. Our interpretation prefers a merger with gas-rich satellite over cold accretion from a cosmic filament as a source of gas, which then formed the counter-rotating disk in PGC 66551.

The Dark Energy Survey is able to collect image data of an extremely large number of extragalactic objects, and it can be reasonably assumed that many unusual objects of high scientific interest are hidden inside these data. Due to the extreme size of DES data, identifying these objects among many millions of other celestial objects is a challenging task. The problem of outlier detection is further magnified by the presence of noisy or saturated images. When the number of tested objects is extremely high, even a small rate of noise or false positives leads to a very large number of false detections, making an automatic system impractical. This study applies an automatic method for automatic detection of outlier objects in the first data release of the Dark Energy Survey. By using machine learning-based outlier detection, the algorithm is able to identify objects that are visually different from the majority of the other objects in the database. An important feature of the algorithm is that it allows to control the false-positive rate, and therefore can be used for practical outlier detection. The algorithm does not provide perfect accuracy in the detection of outlier objects, but it reduces the data substantially to allow practical outlier detection. For instance, the selection of the top 250 objects after applying the algorithm to more than $2\cdot10^6$ DES images provides a collection of uncommon galaxies. Such collection would have been extremely time-consuming to compile by using manual inspection of the data.

Magnetic fields are one of most concealed components of the universe. They are observed as part of the intergalactic medium and on galaxy cluster scales, however their origin and evolution is unclear. In this work we use the IllustrisTNG simulation to investigate the effects of magnetic fields in cosmic voids, the least dense regions of the universe. We find that, under the hypothesis of a uniform primordial magnetic field, the voids still reflect the primordial properties of the fields. On the other hand, the galaxies in their interior acquire weaker magnetic fields than galaxies in denser environments.

We present an analysis of the two-point spatial correlation functions of high-mass X-ray binary (HMXB) and young star cluster (YSC) populations in M31 and M33. We find evidence that HMXBs are spatially correlated with YSCs to a higher degree than would be expected from random chance in both galaxies. When supplemented with similar studies in the Milky Way, Small Magellanic Cloud, and NGC 4449, we find that the peak value of the spatial correlation function correlates strongly with the specific star formation rate of the host galaxy. We additionally perform an X-ray stacking analysis of 211 non-X-ray detected YSCs in M31 and 463 YSCs in M33. We do not detect excess X-ray emission at the stacked cluster locations down to 3$\sigma$ upper limits of $\sim10^{33}$ erg s$^{-1}$ (0.35-8 keV) in both galaxies, which strongly suggests that dynamical formation within YSCs is not a major HMXB formation channel. We interpret our results in the context of (1) the recent star formation histories of the galaxies, which may produce differences in the demographics of compact objects powering the HMXBs, and (2) the differences in natal kicks experienced by compact objects during formation, which can eject newly-formed HMXB from their birth clusters.

In the Halo21 absorption modeling challenge we generated synthetic absorption spectra of the circumgalactic medium (CGM), and attempted to estimate the metallicity, temperature, and density (Z, T, and nH) of the underlying gas using observational methods. We iteratively generated and analyzed three increasingly-complex data samples: ion column densities of isolated uniform clouds, mock spectra of 1--3 uniform clouds, and mock spectra of high-resolution turbulent mixing zones. We found that the observational estimates were accurate for both uniform cloud samples, with Z, T, and nH retrieved within 0.1 dex of the source value for >90% of absorption systems. In the turbulent-mixing scenario, the mass, temperature, and metallicity of the strongest absorption components were also retrieved with high accuracy. However, the underlying properties of the subdominant components were poorly constrained because the corresponding simulated gas contributed only weakly to the H I absorption profiles. On the other hand, including additional components beyond the dominant ones did improve the fit, consistent with the true existence of complex cloud structures in the source data.

The lithium present in the photospheres of solar-type stars is transported to the inner parts by convection, reaching regions even somewhat below the convection zone, by non-standard transport mechanisms. In stars with deeper convective zones, this element can reach regions with temperatures sufficient enough to be destroyed, implying in a lower Li content. More metallic stars show a deepening of their convective zones, so they could deplete more Li in comparison with stars of lower metallicity. In order to verify this effect and its amplitude, we selected stars with ~1 M$_{\odot}$ and metallicities within a factor of two relative to the Sun. We studied a sample of 41 metal-rich and -poor solar analogues, and carried out a joint analysis with a sample of 77 solar twins from our previous work, resulting in a total sample of 118 stars covering the metallicity range -0.3 $\leq$ [Fe/H] $\leq$ +0.3 dex. We employed high-resolution (R = 115 000) and high-signal-to-noise ratio (S/N = 400-1000) HARPS spectra and determined the atmospheric parameters using a line-by-line differential analysis and the Li abundance through spectral synthesis. The ages and masses of the whole sample were improved by refining the isochronal method. We also investigated the impact of planets on Li. We found robust anticorrelations between Li abundance and both metallicity and age, with a significance above 10$\sigma$ in both cases. Our results agree qualitatively with theoretical predictions and are useful to constrain non-standard models of Li depletion, and to better understand transport and mixing mechanisms inside stars.

We present the deep homogeneous $UBVRI$ photometric data of 135,071 stars down to $V\sim23$ mag and I ~ 22 mag toward the Carina Nebula. These stars are cross-matched with those from the previous surveys in the X-ray, near-infrared, and mid-infrared wavelengths as well as the Gaia Early Data Release 3 (EDR3). This master catalog allows us to select reliable members and determine the fundamental parameters distance, size, stellar density of stellar clusters in this star-forming region. We revisit the reddening toward the nebula using the optical and the near-infrared colors of early-type stars. The foreground reddening [E(B-V)_fg] is determined to be 0.35+/-0.02, and it seems to follow the standard reddening law. On the other hand, the total-to-selective extinction ratio of the intracluster medium (R_V,cl) decreases from the central region (Trumpler 14 and 16, R_V,cl ~ 4.5) to the northern region (Trumpler 15, R_V,cl ~ 3.4). It implies that the central region is more dusty than the northern region. We find that the distance modulus of the Carina Nebula to be 11.9+/-0.3 mag (d = 2.4+/-0.35 kpc) using a zero-age main-sequence fitting method, which is in good agreement with that derived from the Gaia EDR3 parallaxes. We also present the catalog of 3,331 pre-main-sequence (PMS) members and 14,974 PMS candidates down to V ~ 22 mag based on spectrophotometric properties of young stars at infrared, optical, and X-ray wavelengths. From the spatial distribution of PMS members and PMS candidates, we confirm that the member selection is very reliable down to faint stars. Our data will have a legacy value for follow-up studies with different scientific purposes.

We demonstrate so-called repetitive non-destructive readout (RNDR) for the first time on a Single electron Sensitive Readout (SiSeRO) device. SiSeRO is a novel on-chip charge detector output stage for charge-coupled device (CCD) image sensors, developed at MIT Lincoln Laboratory. This technology uses a p-MOSFET transistor with a depleted internal gate beneath the transistor channel. The transistor source-drain current is modulated by the transfer of charge into the internal gate. RNDR was realized by transferring the signal charge non-destructively between the internal gate and the summing well (SW), which is the last serial register. The advantage of the non-destructive charge transfer is that the signal charge for each pixel can be measured at the end of each transfer cycle and by averaging for a large number of measurements ($\mathrm{N_{cycle}}$), the total noise can be reduced by a factor of 1/$\mathrm{\sqrt{N_{cycle}}}$. In our experiments with a prototype SiSeRO device, we implemented nine ($\mathrm{N_{cycle}}$ = 9) RNDR cycles, achieving around 2 electron readout noise (equivalent noise charge or ENC) with spectral resolution close to the fano limit for silicon at 5.9 keV. These first results are extremely encouraging, demonstrating successful implementation of the RNDR technique in SiSeROs. They also lay foundation for future experiments with more optimized test stands (better temperature control, larger number of RNDR cycles, RNDR-optimized SiSeRO devices) which should be capable of achieving sub-electron noise sensitivities. This new device class presents an exciting technology for next generation astronomical X-ray telescopes requiring very low-noise spectroscopic imagers. The sub-electron sensitivity also adds the capability to conduct in-situ absolute calibration, enabling unprecedented characterization of the low energy instrument response.

The linear polarization of thermal dust emission provides a powerful tool to probe interstellar and circumstellar magnetic fields, because aspherical grains tend to align themselves with magnetic field lines. While the Radiative Alignment Torque (RAT) mechanism provides a theoretical framework to this phenomenon, some aspects of this alignment mechanism still need to be quantitatively tested. One such aspect is the possibility that the reference alignment direction changes from the magnetic field ("B-RAT") to the radiation field k-vector ("k-RAT") in areas of strong radiation fields. We investigate this transition toward the Orion Bar PDR, using multi-wavelength SOFIA HAWC+ dust polarization observations. The polarization angle maps show that the radiation field direction is on average not the preferred grain alignment axis. We constrain the grain sizes for which the transition from B-RAT to k-RAT occur in the Orion Bar (grains > 0.1 {\mu}m toward the most irradiated locations), and explore the radiatively driven rotational disruption that may take place in the high-radiation environment of the Bar for large grains. While the grains susceptible to rotational disruption should be in supra-thermal rotation and aligned with the magnetic field, k-RAT aligned grains would rotate at thermal velocities. We find that the grain size at which the alignment shifts from B-RAT to k-RAT corresponds to grains too large to survive the rotational disruption. Therefore, we expect a large fraction of grains to be aligned at supra-thermal rotation with the magnetic field, and potentially be subject to rotational disruption depending on their tensile strength.

The elastic scattering between dark matter (DM) and radiation can potentially explain small-scale observations that the cold dark matter faces as a challenge, as damping density fluctuations via dark acoustic oscillations in the early universe erases small-scale structure. We study a semi-analytical subhalo model for interacting dark matter with radiation, based on the extended Press-Schechter formalism and subhalos' tidal evolution prescription. We also test the elastic scattering between DM and neutrinos using observations of Milky-Way satellites from the Dark Energy Survey and PanSTARRS1. We conservatively impose strong constraints on the DM-neutrino scattering cross section of $\sigma_{{\rm DM}\text{-}\nu,n}\propto E_\nu^n$ $(n=0,2,4)$ at $95\%$ confidence level (CL), $\sigma_{{\rm DM}\text{-}\nu,0}< 10^{-32}\ {\rm cm^2}\ (m_{\rm DM}/{\rm GeV})$, $\sigma_{{\rm DM}\text{-}\nu,2}< 10^{-43}\ {\rm cm^2}\ (m_{\rm DM}/{\rm GeV})(E_\nu/E_{\nu}^0)^2$ and $\sigma_{{\rm DM}\text{-}\nu,4}< 10^{-54}\ {\rm cm^2}\ (m_{\rm DM}/{\rm GeV})(E_\nu/E_{\nu}^0)^4$, where $E_\nu^0$ is the average momentum of relic cosmic neutrinos today, $E_\nu^0 \simeq 3.15 T_\nu^0 \simeq 6.1\ {\rm K}$. By imposing a satellite forming condition, we obtain the strongest upper bounds on the DM-neutrino cross section at $95\%$ CL, $\sigma_{{\rm DM}\text{-}\nu,0}< 4\times 10^{-34}\ {\rm cm^2}\ (m_{\rm DM}/{\rm GeV})$, $\sigma_{{\rm DM}\text{-}\nu,2}< 10^{-46}\ {\rm cm^2}\ (m_{\rm DM}/{\rm GeV})(E_\nu/E_{\nu}^0)^2$ and $\sigma_{{\rm DM}\text{-}\nu,4}< 7\times 10^{-59}\ {\rm cm^2}\ (m_{\rm DM}/{\rm GeV})(E_\nu/E_{\nu}^0)^4$.

We extract the galaxy density and momentum power spectra from a subset of early-type galaxies in the SDSS DR7 main galaxy catalog. Using galaxy distance information inferred from the improved fundamental plane described in Yoon et al. (2020), we reconstruct the peculiar velocities of the galaxies and generate number density and density-weighted velocity fields, from which we extract the galaxy density and momentum power spectra. We compare the measured values to the theoretical expectation of the same statistics, assuming an input $\Lambda$CDM model and using a third-order perturbative expansion. After validating our analysis pipeline with a series of mock data sets, we apply our methodology to the SDSS data and arrive at constraints $f \sigma_{8} = 0.485_{-0.083}^{+0.075} $ and $b_{1}\sigma_{8} = 0.883_{-0.059}^{+0.059}$ at a mean redshift $\bar{z} = 0.043$. Our result is consistent with the Planck cosmological best fit parameters for the $\Lambda$CDM model. The momentum power spectrum is found to be strongly contaminated by small scale velocity dispersion, which suppresses power by $\sim {\cal O}(30\%)$ on intermediate scales $k \sim 0.05 \, h \, {\rm Mpc}^{-1}$.

Scientific data reduction on-board deep space missions is a powerful approach to maximise science return, in the absence of wide telemetry bandwidths. The Polarimetric and Helioseismic Imager (PHI) on-board the Solar Orbiter (SO) is the first solar spectropolarimeter that opted for this solution, and provides the scientific community with science-ready data directly from orbit. This is the first instance of full solar spectropolarimetric data reduction on a spacecraft. In this paper, we analyse the accuracy achieved by the on-board data reduction, which is determined by the trade-offs taken to reduce computational demands and to ensure the autonomous operation of the instrument during the data reduction process. We look at the magnitude and nature of errors introduced in the different pipeline steps of the processing. We use an MHD sunspot simulation to isolate the data processing from other sources of inaccuracy. We process the data set with calibration data obtained from SO/PHI in orbit, and compare results calculated on a representative SO/PHI model on ground with a reference implementation of the same pipeline, without the on-board processing trade-offs. Our investigation shows that the accuracy in the Stokes vectors, achieved by the data processing, is at least two orders of magnitude better than what the instrument was designed to achieve. We also found that the errors in the physical parameters are within the accuracy of typical RTE inversions with Milne-Eddington approximation of the atmosphere. This paper demonstrates that the on-board data reduction of the data from SO/PHI does not compromise the accuracy of the processing. This places on-board data processing as a viable alternative for future scientific instruments that would need more telemetry than many missions are able to provide, in particular those in deep space.

Galaxy pairs constitute the initial building blocks of galaxy evolution, which is driven through merger events and interactions. Thus, the analysis of these systems can be valuable in understanding galaxy evolution and studying structure formation. In this work, we present a new publicly available catalogue of close galaxy pairs identified using photometric redshifts provided by the Physics of the Accelerating Universe Survey (PAUS). To efficiently detect them we take advantage of the high-precision photo$-z$ ($\sigma_{68} < 0.02$) and apply an identification algorithm previously tested using simulated data. This algorithm considers the projected distance between the galaxies ($r_p < 50$ kpc), the projected velocity difference ($\Delta V < 3500$ km/s) and an isolation criterion to obtain the pair sample. We applied this technique to the total sample of galaxies provided by PAUS and to a subset with high-quality redshift estimates. Finally, the most relevant result we achieved was determining the mean mass for several subsets of galaxy pairs selected according to their total luminosity, colour and redshift, using galaxy-galaxy lensing estimates. For pairs selected from the total sample of PAUS with a mean $r-$band luminosity $10^{10.6} h^{-2} L_\odot$, we obtain a mean mass of $M_{200} = 10^{12.2} h^{-1} M_\odot$, compatible with the mass-luminosity ratio derived for elliptical galaxies. We also study the mass-to-light ratio $M/L$ as a function of the luminosity $L$ and find a lower $M/L$ (or steeper slope with $L$) for pairs than the one extrapolated from the measurements in groups and galaxy clusters.

The particle origin of dark matter (DM) is still one of the main puzzles in modern physics. One of the most promising search strategy to detect DM at laboratories is through the indirect search of cosmic particles that are produced from DM annihilation in space. In particular, the flux of cosmic positrons has been measured with high precision by the AMS-02 experiment demonstrating that an excess above 10 GeV, with respect to the secondary production, is present. We study in this paper the possible DM origin of the positron excess finding the values of the DM mass $M$ and annihilation cross section $\langle \sigma v \rangle$ that are needed to fit high-energy positron data. In particular, we find that for DM annihilating into $b\bar{b}$ it is required to have $M=43$ TeV and $\langle \sigma v \rangle = 10^{-21}$ cm$^3$/s while for $\tau^+\tau^-$ $M=2$ TeV and $\langle \sigma v \rangle = 3\times 10^{-23}$ cm$^3$/s. If DM produce positrons, they are expected to generate gamma rays from the center of the Milky Way and around dwarf galaxy satellites of the Galaxy. We thus combine the values for the DM mass and annihilation cross section obtained with the fit to AMS-02 positron data with the upper limits derived with the non-detection of $\gamma$ rays with HESS in the direction of the Galactic center and Fermi-LAT for the combined analysis of dwarf galaxies. The main result of the paper is that only DM annihilating into $\mu^+ \mu^-$ with a mass around 500 GeV and $\langle \sigma v \rangle = 4\times 10^{-24}$ cm$^3$/s can fit AMS-02 data and be compatible with the upper limits found with $\gamma$ rays. As for the $\tau^+ \tau^-$ ($b\bar{b}$) channel, DM can contribute at most at a few tens $\%$ (a few \%) level.

Radiative emissions from electrons and positrons generated by dark matter (DM) annihilation or decay are one of the most investigated signals in indirect searches of WIMPs. Ideal targets must have large ratio of DM to baryonic matter. However, such ``dark'' systems have a poorly known level of magnetic turbulence, which determines the residence time of the electrons and positrons and therefore also the strength of the expected signal. This typically leads to significant uncertainties in the derived DM bounds. In a novel approach, we compute the self-confinement of the DM-induced electrons and positrons. Indeed, they themselves generate irregularities in the magnetic field, thus setting a lower limit on the presence of the magnetic turbulence. We specifically apply this approach to dwarf spheroidal galaxies. Finally, by comparing the expected synchrotron emission with radio data from the direction of the Draco galaxy collected at the Giant Metre Radio Telescope, we show that the proposed approach can be used to set robust and competitive bounds on WIMP DM.

We present the early science results from a blind search of the extragalactic HI 21-cm absorption lines at z $\leqslant$ 0.09 with the drift-scan observation of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We carried out the search using the data collected in 643.8 hours by the ongoing Commensal Radio Astronomy FasT Survey (CRAFTS), which spans a sky area of 3155 deg$^{2}$ and covers 44827 radio sources with a flux density greater than 12 mJy. Due to the radio frequency interference (RFI), only the relatively clean data in the frequency range of 1.3-1.45 GHz are used in the present work. Under the assumption of $T_{s}/c_{f}$ = 100 K, the total completeness-corrected comoving absorption path length spanned by our data and sensitive to Damped Lyman $\alpha$ Absorbers (DLAs) are $\Delta X^{inv}$ = 8.33$\times10^3$ ($\Delta z^{inv} = 7.81\times10^{3}$) for intervening absorption. For associated absorption, the corresponding values are $\Delta X^{asc}$ = 12.8 ($\Delta z^{asc} = 11.9$). Three known HI absorbers (UGC 00613, 3C 293 and 4C +27.14) and two new HI absorbers (towards NVSS J231240-052547 and NVSS J053118+315412) are detected blindly. We fit the HI profiles with multi-components Gaussian functions and calculate the redshift (0.063, 0.066), width, flux density, optical depth and HI column densities for each absorption. Our results demonstrate the power of FAST in blindly searching HI absorbers. For absorption towards NVSS J231240-052547, the optical counterparts are faint and currently lack existing spectra. The most likely interpretation is that a radio-loud active galactic nucleus (AGN) is faint in the optical as the background source, with a faint optical absorber in between. NVSS J053118+315412 exhibits an associated absorption with a complex profile, which may suggest unsettled gas structures or gas accretion onto the supermassive black hole (SMBH).

Here we discuss the feasibility of photosynthesis on Earth-like rocky planets in close orbit around ultra-cool red dwarf stars. Stars of this type have very limited emission in the \textit{photosynthetically active} region of the spectrum ($400 - 700$ nm), suggesting that they may not be able to support oxygenic photosynthesis. However, photoautotrophs on Earth frequently exploit very dim environments with the aid of highly structured and extremely efficient antenna systems. Moreover, the anoxygenic photosynthetic bacteria, which do not need to oxidize water to source electrons, can exploit far red and near infrared light. Here we apply a simple model of a photosynthetic antenna to a range of model stellar spectra, ranging from ultra-cool (2300 K) to Sun-like (5800 K). We assume that a photosynthetic organism will evolve an antenna that maximizes the rate of energy input while also minimizing fluctuations. The latter is the 'noise cancelling' principle recently reported by Arp et al. 2020. Applied to the Solar spectrum this predicts optimal antenna configurations in agreement with the chlorophyll Soret absorption bands. Applied to cooler stars, the optimal antenna peaks become redder with decreasing stellar temperature, crossing to the typical wavelength ranges associated with anoxygenic photoautotrophs at $\sim 3300$ K. Lastly, we compare the relative input power delivered by antennae of equivalent size around different stars and find that the predicted variation is within the same order of magnitude. We conclude that low-mass stars do not automatically present light-limiting conditions for photosynthesis but they may select for anoxygenic organisms.

We measure the scaling relations of the bulges and disks of the EFIGI galaxies in the nearby Universe versus morphology, using bulge and disk decomposition of SDSS gri images with SourceXtractor++. The Kormendy (1977) relation between effective surface brightness and effective radius of E galaxies extends to the bulges of types S0 to Sb, whereas fainter and smaller bulges of later Hubble types depart from it, with decreasing bulge-to-total ratio (B/T) and S\'ersic indices. There is a continuous transition from pseudo-bulges to classical ones, proposed to occur for g magnitudes between -17.8 to -19.1. The size-luminosity relations for E and dE types are steeper and similar to those from Binggeli et al. (1984), resp., below which EFIGI lenticular and spiral bulges display a curved relation. The disks and irregulars also follow a continuous curved size-luminosity relation such that while they grow, they first brighten and then stabilize in surface brightness. Moreover, we obtain the unprecedented result that the effective radii of both the bulges and disks of spirals increase as power-laws of B/T, with a steeper increase for the bulges. The increase with B/T is much steeper and similar for the bulges and disks of lenticulars. The ratio of disk-to-bulge effective radii varies accordingly across 2 orders of magnitude in B/T for all lenticular and spiral types, with a mean disk-to-bulge ratio decreasing from ~15 for Sbc to Scd types to ~6 for S0. We tabulate all derived scaling relations, so that they can be used to build realistic mock images of nearby galaxies. The new curved size-luminosity relations will prevent over or under estimates of bulge, disk and galaxy sizes at all magnitudes. These results complement the analysis of Quilley & de Lapparent (2022) by providing the joint size and luminosity variations of bulges and disks, as they evolve reversely along the Hubble sequence.

After the first quasi-periodic eruptions (QPEs, GSN069) was reported in 2019, four other sources have been identified as QPEs or its candidate. However, the physics behind QPEs is still unclear so far, though several models have been proposed. Pan et al. (2022) proposed an instability model for the accretion disk with magnetically driven outflows in the first QPEs GSN 069, which is able to reproduce both the light curve and the evolution of spectrum fairly well. In this work, we exploit this model to all the QPEs. We imporve the calculations of the spectrum of disk by introducing a hardening factor, which is caused by the deviation of opacity from the blackbody. We find that the light curves and evolution of the spectra of the four QPEs or candidate can all be well reproduced by our model calculations.

We present gas-phase elemental abundance ratios of 7 local extremely metal-poor galaxies (EMPGs) including our new Keck/LRIS spectroscopy determinations together with 33 JWST $z\sim 4-10$ star-forming galaxies in the literature, and compare chemical evolution models. We develop chemical evolution models with the yields of core-collapse supernovae (CCSNe), Type Ia supernovae, hypernovae (HNe), and pair-instability supernovae (PISNe), and compare the EMPGs and high-$z$ galaxies in conjunction with dust depletion contributions. We find that high Fe/O values of EMPGs can (cannot) be explained by PISN metal enrichments (CCSN/HN enrichments even with the mixing-and-fallback mechanism enhancing iron abundance), while that the observed Ar/O and S/O values are much smaller than the predictions of the PISN models. The abundance ratios of the EMPGs can be explained by the combination of Type Ia SNe and CCSNe/HNe whose inner layers of argon and sulfur mostly fallback, which are comparable with Sculptor stellar chemical abundance distribution, suggesting that early chemical enrichment is taken place in the EMPGs. Comparing our chemical evolution models with the star-forming galaxies at $z\sim 4-10$, we find that the Ar/O and S/O ratios of the high-$z$ galaxies are comparable with those of the CCSNe/HNe models, while majority of the high-$z$ galaxies do not have constraints good enough to rule out contributions from PISNe. The high N/O ratio recently reported in GN-z11 cannot be explained even by rotating PISNe, but could be reproduced by the winds of rotating Wolf Rayet stars that end up as a direct collapse.

Recent works have developed samples of blazars from among the Fermi-LAT unassociated sources via machine learning comparisons with known blazar samples. Continued analysis of these new blazars tests the predictions of the blazar sequence and enables more flux-complete samples of blazars as a population. Using Fermi, Swift, WISE, and archival radio data, we construct broadband spectral energy distributions for 106 recently identified blazars. Drawn from the unassociated 4FGL source sample, this new sample has a lower median flux than the overall sample of gamma-ray blazars. By measuring the synchrotron peak frequency, we compare our sample of new blazars with known blazars from the 4LAC catalog. We find that the bulk of the new blazars are similar to High-Synchrotron Peak (HSP) BL Lac objects, with a higher median synchrotron peak; the sample has a median $ log( {\nu}_{syn} /Hz ) = 15.5 $ via BLaST peak estimation, compared to $ log( {\nu}_{syn} /Hz ) = 14.2 $ for the 4LAC BL Lacs. Finally, we conduct synchrotron self-Compton (SSC) leptonic modeling, comparing fitted physical and phenomenological properties to brighter blazars. We find that the new blazars have smaller characteristic Lorentz factors ${\gamma}_{boost}$ and fitted magnetic fields $B$, in agreement with blazar sequence predictions. The new blazars have slightly higher Compton dominance ratios than expected, which may point to alternative emission models for these dim blazars. Our results extend the predictions of the blazar sequence to a sample of dimmer blazars, confirming the broad predictions of that theory.

The aim of this paper is to demonstrate the possible use of the new coronal model COCONUT to compute a detailed representation of a numerical CME at 0.1~AU, after its injection at the solar surface and propagation in a realistic solar wind, as derived from observed magnetograms. We present the implementation and propagation of modified Titov-D\'emoulin (TDm) flux ropes in the COCONUT 3D MHD coronal model. The background solar wind is reconstructed in order to model two opposite configurations representing a solar activity maximum and minimum respectively. Both were derived from magnetograms which were obtained by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory (SDO) satellite. We track the propagation of 24 flux ropes, which differ only by their initial magnetic flux. We especially investigate the geometry of the flux rope during the early stages of the propagation as well as the influence of its initial parameters and solar wind configuration on 1D profiles derived at 0.1~AU. At the beginning of the propagation, the shape of the flux ropes varies between simulations during low and high solar activity. We find dynamics that are consistent with the standard CME model, such as the pinching of the legs and the appearance of post-flare loops. Despite the differences in geometry, the synthetic density and magnetic field time profiles at 0.1~AU are very similar in both solar wind configurations. These profiles are similar to those observed further in the heliosphere and suggest the presence of a magnetic ejecta composed of the initially implemented flux rope and a sheath ahead of it. Finally, we uncover relationships between the properties of the magnetic ejecta, such as density or speed and the initial magnetic flux of our flux ropes.

The ESA Gaia space mission has revealed a bifurcation of the white dwarf (WD) sequence on the color magnitude diagram in two branches: A and B. While the A branch consists mostly of WDs with H-rich atmospheres, the B branch is not completely understood. Although invoked to be populated mainly by He-rich WDs, the B branch overlaps a $\sim 0.8M_\odot$ evolutionary track with a pure He envelope, fact that would imply an unexpected peak in the WD mass distribution. In cold He-rich WDs, it is expected that the outer convective zone penetrates into deep C-rich layers, thus leading to a slight C contamination in their surfaces at $\sim 10,000$K. Here we aim at studying the Gaia bifurcation as the natural consequence of C dredge-up by convection in cold He-dominated WDs. Relying on accurate atmosphere models, we provide a new set of evolutionary models for He-rich WDs employing different prescriptions for the C enrichment. On the basis of these models, we made a population synthesis study of the Gaia 100pc WD sample to constrain the models that best fit the bifurcation. Our study shows that He-rich WD models with a slight C contamination below the optical detection limit can accurately reproduce the Gaia bifurcation. We refer to these stars as stealth DQ WDs because they do not exhibit detectable C signatures in their optical spectra, but the presence of C in their atmosphere produces a continuum absorption favouring the emission in bluer wavelengths, thereby creating the B branch of the bifurcation. Also, we show that the mass distribution for He-rich WDs obtained when a stealth C contamination is considered is consistent with the mass distribution for H-rich WDs and with the standard evolutionary channels for their formation. We conclude that stealth DQ WDs can account for the lower branch in the Gaia bifurcation. The C signatures of these stars could be detectable in Ultra-Violet spectra.

In General Relativity approximations based on the spherical collapse model such as Press--Schechter theory and its extensions are able to predict the number of objects of a certain mass in a given volume. In this paper we use a machine learning algorithm to test whether such approximations hold in screened modified gravity theories. To this end, we train random forest classifiers on data from N-body simulations to study the formation of structures in $\Lambda$CDM as well as screened modified gravity theories, in particular $f(R)$ and nDGP gravity. The models are taught to distinguish structure membership in the final conditions from spherical aggregations of density field behaviour in the initial conditions. We examine the differences between machine learning models that have learned structure formation from each gravity, as well as the model that has learned from $\Lambda$CDM. We also test the generalisability of the $\Lambda$CDM model on data from $f(R)$ and nDGP gravities of varying strengths, and therefore the generalisability of Extended-Press-Schechter spherical collapse to these types of modified gravity.

Context: Recent advances in the development of precise radial velocity (RV) instruments in the near-infrared (nIR) domain, such as SPIRou, have facilitated the study of M-type stars to more effectively characterize planetary systems. However, the nIR presents unique challenges in exoplanet detection due to various sources of planet-independent signals which can result in systematic errors in the RV data. Aims: In order to address the challenges posed by the detection of exoplanetary systems around M-type stars using nIR observations, we introduce a new data-driven approach for correcting systematic errors in RV data. The effectiveness of this method is demonstrated through its application to the star GJ\,251. Methods: Our proposed method, referred to as \texttt{Wapiti} (Weighted principAl comPonent analysIs reconsTructIon), uses a dataset of per-line RV time-series generated by the line-by-line (LBL) algorithm and employs a weighted principal component analysis (wPCA) to reconstruct the original RV time-series. A multi-step process is employed to determine the appropriate number of components, with the ultimate goal of subtracting the wPCA reconstruction of the per-line RV time-series from the original data in order to correct systematic errors. Results: The application of \texttt{Wapiti} to GJ\,251 successfully eliminates spurious signals from the RV time-series and enables the first detection in the nIR of GJ\,251b, a known temperate super-Earth with an orbital period of 14.2 days. This demonstrates that, even when systematics in SPIRou data are unidentified, it is still possible to effectively address them and fully realize the instrument's capability for exoplanet detection. Additionally, in contrast to the use of optical RVs, this detection did not require to filter out stellar activity, highlighting a key advantage of nIR RV measurements.

Disk solids are critical in many planet formation processes, however, their effect on planet migration remains largely unexplored. Here we assess for the first time this important issue by building on the systematic measurements of dust torques on an embedded planet by Benitez-Llambay & Pessah (2018). Adopting standard models for the gaseous disk and its solid content, we quantify the impact of the dust torque for a wide range of conditions describing the disk/planet system. We show that the total torque can be positive and revert inward planet migration for planetary cores with $M_{\rm p} \lesssim 10 M_\oplus$. We compute formation tracks for low-mass embryos for conditions usually invoked when modeling planet formation processes. Our most important conclusion is that dust torques can have a significant impact on the migration and formation history of planetary embryos. The most important implications of our findings are: $\it{i})$ For nominal dust-to-gas mass ratios $\epsilon \simeq 0.01$, low-mass planets migrate outwards beyond the water ice-line if most of the mass in solids is in particles with Stokes numbers St $\simeq 0.1$. $\it{ii})$. For $\epsilon \gtrsim 0.02-0.05$, solids with small Stokes numbers, St $\simeq 0.01$, can play a dominant role if most of the mass is in those particles. $\it{iii})$ Dust torques have the potential to enable low-mass planetary cores formed in the inner disk to migrate outwards and act as the seed for massive planets at distances of tens of au.

We present ionizing spectra estimated at 13.6--100 eV for ten dwarf galaxies with strong high ionization lines of He {\sc {ii}}$\lambda$4686 and [Ne {\sc{v}}]$\lambda$3426 ([Ne {\sc{iv}}]$\lambda$2424) at $z=0$ ($z=8$) that are identified in our Keck/LRIS spectroscopy and the literature (the JWST ERO program). With the flux ratios of these high ionization lines and $>10$ low-ionization lines of hydrogen, helium, oxygen, neon, and sulfur, we determine ionizing spectra consisting of stellar and non-thermal power-law radiation by photoionization modeling with free parameters of nebular properties including metallicity and ionization parameter, cancelling out abundance ratio differences. We find that all of the observed flux ratios are well reproduced by the photoinization models with the power law index $\alpha_{\rm EUV}$ of $\alpha_{\rm EUV}\sim (-1)-0$ and the luminosity $L_{\rm EUV}$ of $L_{\rm EUV}\sim 10^{40}-10^{42}$ erg s$^{-1}$ at $\sim 55-100$ eV for six galaxies, while four galaxies include large systematics in $\alpha_{\rm EUV}$ caused by stellar radiation contamination. We then compare $\alpha_{\rm EUV}$ and $L_{\rm EUV}$ of these six galaxies with those predicted by the black hole (BH) accretion disk models, and find that these galaxies have moderately soft/luminous ionizing spectra whose $\alpha_{\rm EUV}$ and $L_{\rm EUV}$ are similar to those of the intermediate mass black holes (IMBHs) in BH accretion disk models. Confirming these results with a known IMBH having a mass $M_{\rm BH}$ of $M_{\rm BH}=10^{5.75} \ M_\odot$, we find that four local galaxies and one $z=7.665$ galaxy have ionizing spectra consistent with those of IMBHs with $M_{\rm BH} \sim 10^3-10^5 \ M_\odot$.

Theoretical models for the solar dynamo range from simple low-dimensional ``toy models'' to complex 3D-MHD simulations. Here we mainly discuss appproaches that are motivated and guided by solar (and stellar) observations. We give a brief overview of the evolution of solar dynamo models since 1950s, focussing upon the development of the Babcock-Leighton approach between its introduction in the 1960s and its revival in the 1990s after being long overshadowed by mean-field turbulent dynamo theory. We summarize observations and simple theoretical deliberations that demonstrate the crucial role of the surface fields in the dynamo process and and give quantitative analyses of the generation and loss of toroidal flux in the convection zone as well as of the production of poloidal field resulting from flux emergence at the surface. Furthermore, we discuss possible nonlinearities in the dynamo process suggested by observational results and present models for the long-term variability of solar activity motivated by observations of magnetically active stars and the inherent randomness of the dynamo process.

The application of Very Long Baseline Interferometry (VLBI) to the Search for Extraterrestrial Intelligence (SETI) has been limited to date, despite the technique offering many advantages over traditional single-dish SETI observations. In order to further develop interferometry for SETI, we used the European VLBI Network (EVN) at $21$~cm to observe potential secondary phase calibrators in the Kepler field. Unfortunately, no secondary calibrators were detected. However, a VLBA primary calibrator in the field, J1926+4441, offset only $\sim1.88'$ from a nearby exoplanet Kepler-111~b, was correlated with high temporal $\left(0.25 \ \rm{s}\right)$ and spectral $\left(16384 \times 488\ \rm{Hz \ channels}\right)$ resolution. During the analysis of the high-resolution data, we identified a spectral feature that was present in both the auto and cross-correlation data with a central frequency of $1420.424\pm0.0002$ MHz and a width of 0.25 MHz. We demonstrate that the feature in the cross-correlations is an artefact in the data, associated with a significant increase in each telescope's noise figure due to the presence of \ion{H}{i} in the beam. This would typically go unnoticed in data correlated with standard spectral resolution. We flag (excluded from the subsequent analysis) these channels and phase rotate the data to the location of Kepler-111~b aided by the GAIA catalogue and search for signals with $\rm{SNR}>7$. At the time of our observations, we detect no transmitters with an Equivalent Isotropically Radiated Power (EIRP) > $\sim4\times10^{15}$ W.

Multiwavelength observations of the propagating disturbances (PDs), discovered by Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO), are analyzed to determine its driving mechanism and physical nature. Two magnetic strands in the localised corona are observed to approach and merge with each other followed by the generation of brightening, which further propagates in a cusp-shaped magnetic channel. Differential emission measure analysis shows an occurrence of heating in this region-of-interest (ROI). We extrapolate potential magnetic field lines at coronal heights from observed Helioseismic and Magnetic Imager (HMI) vector magnetogram via Green's function method using MPI-AMRVAC. We analyze the field to locate magnetic nulls and quasi-separatrix layers (QSLs) which are preferential locations for magnetic reconnection. Dominant QSLs including a magnetic null are found to exist and match the geometry followed by PDs, therefore, it provides conclusive evidence of magnetic reconnection. In addition, spectroscopic analysis of Interface Region Imaging Spectrograph (IRIS) Si IV 1393.77 {\AA} line profiles show a rise of line-width in the same time range depicting presence of mass motion in the observed cusp-shaped region. PDs are observed to exhibit periodicities of around four minutes. The speeds of PDs measured by Surfing Transform Technique are almost close to each other in four different SDO/AIA bandpasses, i.e., 304, 171, 193 and 131 {\AA} excluding the interpretation of PDs in terms of slow magnetoacoustic waves. We describe comprehensively the observed PDs as quasi-periodic plasma flows generated due to periodic reconnection in vicinity of a coronal magnetic null.

The tidal deformations of a planet are often considered as markers of its inner structure. In this work, we use the tide excitations induced by the Sun on Venus for deciphering the nature of its internal layers. In using a Monte Carlo Random Exploration of the space of parameters describing the thickness, density and viscosity of 4 or 5 layer profiles, we were able to select models that can reproduce the observed mass, total moment of inertia, $k_2$ Love number and expected quality factor $Q$. Each model is assumed to have homogeneous layers with constant density, viscosity and rigidity. These models show significant contrasts in the viscosity between the upper mantle and the lower mantle. They also rather favor a S-free core and a slightly hotter lower mantle consistent with previous expectations.

Pandora is an upcoming NASA SmallSat mission that will observe transiting exoplanets to study their atmospheres and the variability of their host stars. Efficient mission planning is critical for maximizing the science achieved with the year-long primary mission. To this end, we have developed a scheduler based on a metaheuristic algorithm that is focused on tackling the unique challenges of time-constrained observing missions, like Pandora. Our scheduling algorithm combines a minimum transit requirement metric, which ensures we meet observational requirements, with a `quality' metric that considers three factors to determine the scientific quality of each observation window around an exoplanet transit (defined as a visit). These three factors are: observing efficiency during a visit, the amount of the transit captured by the telescope during a visit, and how much of the transit captured is contaminated by a coincidental passing of the observatory through the South Atlantic Anomaly. The importance of each of these factors can be adjusted based on the needs or preferences of the science team. Utilizing this schedule optimizer, we develop and compare a few schedules with differing factor weights for the Pandora SmallSat mission, illustrating trade-offs that should be considered between the three quality factors. We also find that under all scenarios probed, Pandora will not only be able to achieve its observational requirements using the planets on the notional target list but will do so with significant time remaining for ancillary science.

We report high-resolution ALMA observations toward a massive protostellar core C1-Sa ($\sim$30 M$_\odot$) in the Dragon Infrared Dark Cloud. At the resolution of 140 AU, the core fragments into two kernels (C1-Sa1 and C1-Sa2) with a projected separation of $\sim$1400 AU along the elongation of C1-Sa, consistent with a Jeans length scale of $\sim$1100 AU. Radiative transfer modeling using RADEX indicates that the protostellar kernel C1-Sa1 has a temperature of $\sim$75 K and a mass of 0.55 M$_\odot$. C1-Sa1 also likely drives two bipolar outflows, one being parallel to the plane-of-the-sky. C1-Sa2 is not detected in line emission and does not show any outflow activity but exhibits ortho-H$_2$D$^+$ and N$_2$D$^+$ emission in its vicinity, thus it is likely still starless. Assuming a 20 K temperature, C1-Sa2 has a mass of 1.6 M$_\odot$. At a higher resolution of 96 AU, C1-Sa1 begins to show an irregular shape at the periphery, but no clear sign of multiple objects or disks. We suspect that C1-Sa1 hosts a tight binary with inclined disks and outflows. Currently, one member of the binary is actively accreting while the accretion in the other is significantly reduced. C1-Sa2 shows hints of fragmentation into two sub-kernels with similar masses, which requires further confirmation with higher sensitivity.

Context: Carbon Enhanced Metal-Poor (CEMP) stars ($\mathrm{[C/Fe]} > 0.7$) are known to exist in large numbers at low metallicity in the Milky Way halo and are important tracers of early Galactic chemical evolution. However, very few such stars have been identified in the classical dwarf spheroidal (dSph) galaxies, and detailed abundances, including neutron-capture element abundances, have only been reported for 12 stars. Aims: We aim to derive detailed abundances of six CEMP stars identified in the Carina dSph and compare the abundances to CEMP stars in other dSph galaxies and the Milky Way halo. This is the largest sample of CEMP stars in a dSph galaxy analysed to date. Methods: 1D LTE elemental abundances are derived via equivalent width and spectral synthesis using high-resolution spectra of the six stars obtained with the MIKE spectrograph at Las Campanas Observatory. Results: Abundances or upper limits are derived for up to 27 elements from C to Os in the six stars. The analysis reveals one of the stars to be a CEMP-no star with very low neutron-capture element abundances. In contrast, the other five stars all show enhancements in neutron-capture elements in addition to their carbon enhancement, classifying them as CEMP-$s$ and -$r/s$ stars. The six stars have similar $\alpha$ and iron-peak element abundances as other stars in Carina, except for the CEMP-no star, which shows enhancement in Na, Mg, and Si. We explore the absolute carbon abundances ($A(\rm C)$) of CEMP stars in dSph galaxies and find similar behaviour as is seen for Milky Way halo CEMP stars, but highlight that CEMP-$r/s$ stars primarily have very high $A(\rm C)$ values. We also compare the neutron-capture element abundances of the CEMP-$r/s$ stars in our sample to recent $i$-process yields, which provide a good match to the derived abundances.

We demonstrate that the Peccei-Quinn-electromagnetic anomaly coefficient $\mathcal A$ can be directly measured from axion string-induced cosmic birefringence by applying scattering transform to the anisotropic polarization rotation of the cosmic microwave background. This breaks the degeneracy between $\mathcal A$ and the effective number of string loops in traditional inference analyses that are solely based on the spatial power spectrum of polarization rotation. Carrying out likelihood-based parameter inference on mock rotation realizations generated according to phenomenological string network models, we show that scattering transform is able to extract enough non-Gaussian information to clearly distinguish a number of discrete $\mathcal A$ values, for instance $\mathcal{A}=1/9,\,1/3,\,2/3$, in the ideal case of noise-free rotation reconstruction, and, to a lesser but interesting degree, at reconstruction noise levels comparable to that expected for the proposed CMB-HD concept. In the event of a statistical detection of cosmic birefringence by Stage III or IV CMB experiments, our technique can be applied to test the stringy nature of the birefringence pattern and extract fundamental information about the smallest unit of charge in theories beyond the Standard Model.

Ultralight bosons are predicted in many extensions to the Standard Model and are popular dark matter candidates. The black hole superradiance mechanism allows for these particles to be probed using only their gravitational interaction. In this scenario, an ultralight boson cloud may form spontaneously around a spinning black hole and extract a non-negligible fraction of the black hole's mass. These oscillating clouds produce quasi-monochromatic, long-duration gravitational waves that may be detectable by ground-based or space-based gravitational wave detectors. We discuss the capability of a new long-duration signal tracking method, based on a hidden Markov model, to detect gravitational wave signals generated by ultralight vector boson clouds, including cases where the signal frequency evolution timescale is much shorter than that of a typical continuous wave signal. We quantify the detection horizon distances for vector boson clouds with current- and next-generation ground-based detectors. We demonstrate that vector clouds hosted by black holes with mass $\gtrsim 60 M_{\odot}$ and spin $\gtrsim 0.6$ are within the reach of current-generation detectors up to a luminosity distance of $\sim 1$ Gpc. This search method enables one to target vector boson clouds around remnant black holes from compact binary mergers detected by gravitational-wave detectors. We discuss the impact of the sky localization of the merger events and demonstrate that a typical remnant black hole reasonably well-localized by the current generation detector network is accessible in a follow-up search.

We provide an algorithm for evolving general spin-$s$ Gross-Pitaevskii / non-linear Schr\"odinger systems carrying a variety of interactions, where the $2s+1$ components of the `spinor' field represent the different spin-multiplicity states. We consider many nonrelativistic interactions up to quartic order in the Schr\"odinger field (both short and long-range, and spin-dependent and spin-independent interactions), including explicit spin-orbit couplings. The algorithm allows for spatially varying external and/or self-generated vector potentials that couple to the spin density of the field. Our work can be used for scenarios ranging from laboratory systems such as spinor Bose-Einstein condensates (BECs), to cosmological/astrophysical systems such as self-interacting bosonic dark matter. As examples, we provide results for two different setups of spin-$1$ BECs that employ a varying magnetic field and spin-orbit coupling, respectively, and also collisions of spin-$1$ solitons in dark matter. Our symplectic algorithm is second-order accurate in time, and is extensible to the known higher-order accurate methods.

We reexamine the consequences of perturbative unitarity on dark matter freeze-out when both Sommerfeld enhancement and bound state formation affect dark matter annihilations. At leading order (LO) the annihilation cross-section is infrared dominated and the connection between the unitarity bound and the upper bound on the dark matter mass depends only on how the different partial waves are populated. We compute how this picture is modified at next-to-leading order (NLO) with the goal of assigning a reliable theory uncertainty to the freeze-out predictions. We explicitly compute NLO corrections in a simple model with abelian gauge interactions and provide an estimate of the theoretical uncertainty for the thermal masses of heavy electroweak $n$-plets. Along the way, we clarify the regularization and matching procedure necessary to deal with singular potentials in quantum mechanics with a calculable relativistic UV completion.

We evaluate the Lorentzian gravitational path integral in the presence of non-vanishing torsion with the application of the Picard-Lefschetz theory for minisuperspaces corresponding to a number of phenomenological bouncing cosmological models as well as for the inflationary paradigm. It turns out that the semi-classical wave function derived from the saddle points of the path integral formalism coincides with the solutions of the Wheeler-DeWitt equation. Intriguingly, our analysis showed that the relative probability, derived using these semi-classical wave functions favors universes with smaller values of torsion. Moreover, we find that in the inflationary case, non-zero values of a certain parity-violating component of the torsion enhance the power in the large physical length scales, which can have important observational implications. On the other hand, in the case of bouncing models, the power spectrum is characterized by an initial region of growth, an intermediate oscillatory region, and then again a final region of growth. The shape of the power spectrum in the initial and intermediate regions is sensitive to the abundance of the bounce-enabling matter and torsion, along with the initial wave function of the universe, while the final size modifies the behavior of the power spectrum in the smaller length scales.

The cosmic microwave background (CMB) has proven to be an invaluable tool for studying the properties and interactions of neutrinos, providing insight not only into the sum of neutrino masses but also the free streaming nature of neutrinos prior to recombination. The CMB is a particularly powerful probe of new eV-scale bosons interacting with neutrinos, as these particles can thermalize with neutrinos via the inverse decay process, $\nu\bar{\nu} \rightarrow X$, and suppress neutrino free streaming near recombination -- even for couplings as small as $\lambda_\nu \sim \mathcal{O}(10^{-13})$. Here, we revisit CMB constraints on such bosons, improving upon a number of approximations previously adopted in the literature and generalizing the constraints to a broader class of models. This includes scenarios in which the boson is either spin-$0$ or spin-$1$, the number of interacting neutrinos is either $N_{\rm int} = 1,2 $ or $3$, and the case in which a primordial abundance of the species is present. We apply these bounds to well-motivated models, such as the singlet majoron model or a light $U(1)_{L_\mu-L_\tau}$ gauge boson, and find that they represent the leading constraints for masses $m_X\sim 1\, {\rm eV}$. Finally, we revisit the extent to which neutrino-philic bosons can ameliorate the Hubble tension, and find that recent improvements in the understanding of how such bosons damp neutrino free streaming reduces the previously found success of this proposal.

In our previous papers [arXiv:2106.03150, arXiv:2110.10917, arXiv:2208.00822], we analyzed the asymptotic behavior of future directed null geodesics near future null infinity and then we showed a proposition on the accessibility of the null geodesics to future null infinity in a specific class of asymptotically flat spacetimes. In this paper, we adopt the retarded time of the Bondi coordinate as the parameter for the null geodesics and then see that one can relax the assumptions imposed in our previous studies. As a consequence, we obtain a new null-access theorem for generic asymptotically flat spacetimes.

Numerous observations suggest that there exist undiscovered beyond-the-Standard-Model particles and fields. Because of their unknown nature, these exotic particles and fields could interact with Standard Model particles in many different ways and assume a variety of possible configurations. Here we present an overview of the Global Network of Optical Magnetometers for Exotic physics searches (GNOME), our ongoing experimental program designed to test a wide range of exotic physics scenarios. The GNOME experiment utilizes a worldwide network of shielded atomic magnetometers (and, more recently, comagnetometers) to search for spatially and temporally correlated signals due to torques on atomic spins from exotic fields of astrophysical origin. We survey the temporal characteristics of a variety of possible signals currently under investigation such as those from topological defect dark matter (axion-like particle domain walls), axion-like particle stars, solitons of complex-valued scalar fields (Q-balls), stochastic fluctuations of bosonic dark matter fields, a solar axion-like particle halo, and bursts of ultralight bosonic fields produced by cataclysmic astrophysical events such as binary black hole mergers.

High-frequency gravitational waves (HFGWs) carry a wealth of information on the early Universe with a tiny comoving Hubble horizon and astronomical objects of small scale but with dense energy. We demonstrate that the nearby planets, such as Earth and Jupiter, can be utilized as a laboratory for detecting the HFGWs. These GWs are then expected to convert to signal photons in the planetary magnetosphere, across the frequency band of astronomical observation. As a proof of concept, we present the first limits from the existing low-Earth-orbit satellite for specific frequency bands and project the sensitivities for the future more-dedicated detections. The first limits from Juno, the latest mission orbiting Jupiter, are also presented. Attributed to the long path of effective GW-photon conversion and the wide angular distribution of signal flux, we find that these limits are highly encouraging, for a broad range of frequencies including a large portion unexplored before.

TRIDENT (The tRopIcal DEep-sea Neutrino Telescope) is a proposed next-generation neutrino telescope to be constructed in the South China Sea. In September 2021, the TRIDENT Pathfinder experiment (TRIDENT EXplorer, T-REX for short) was conducted to evaluate the in-situ optical properties of seawater. The T-REX experiment deployed three digital optical modules at a depth of 3420 meters, including a light emitter module (LEM) and two light receiver modules (LRMs) equipped with photomultiplier tubes (PMTs) and cameras to detect light signals. The LEM emits light in pulsing and steady modes. It features a fast tunable driver to activate light-emitting diodes (LEDs) that emit nanosecond-width light pulses with tunable intensity. The PMTs in the LRM receive single photo-electron (SPE) signals with an average photon number of approximately 0.3 per 1-microsecond time window, which is used to measure the arrival time distribution of the SPE signals. The fast tunable driver can be remotely controlled in real-time by the data acquisition system onboard the research vessel, allowing for convenient adjustments to the driver's parameters and facilitating the acquisition of high-quality experimental data. This paper describes the requirements, design scheme, and test results of the fast tunable driver, highlighting its successful implementation in the T-REX experiment and its potential for future deep-sea experiments.

This thesis explores the effects of dark matter (DM) on neutron stars (NSs) using the relativistic mean-field (RMF) model. The effects of DM on NS properties, including the mass-radius relation, the moment of inertia, and tidal deformability, are calculated by varying its fraction. The study found that the EOS becomes softer with increasing DM momentum, and the DM has marginal effects on nuclear matter properties, except for the EOSs and binding energy per particle. The study also calculated the properties of isolated, static, and rotating DM admixed NS and found that the DM has significant effects on both static and rotating NS. We have also observed that a tiny amount of DM can accumulate inside the NS, and more amount of it makes the NS unstable. The study also suggests that the secondary component might be a NS with DM content if the underlying nuclear EOS is sufficiently stiff. The $f$-mode oscillations of the DM admixed hyperon stars are calculated and found that there exist a correlation between canonical $f$-mode frequency and the dimensionless tidal deformability parameter ($\Lambda_{1.4}$) and we have put a constraint on $f$-mode frequency using GW170817 data. Finally, we have calculated the DM admixed binary NS properties and found that the binary system becomes less deformed and sustains more time in its inspiral phases with the addition of DM. Therefore, we suggest that one can take DM inside the compact objects while modeling the inspiral waveforms for the BNS systems.

The oscillations of climatic parameters of North Atlantic Ocean play important role in various events in North America and Europe. Several climatic indices are associated with these oscillations. The long term Atlantic temperature anomalies are described by the Atlantic Multidecadal Oscillation (AMO). The Atlantic Multidecadal Oscillation also known as Atlantic Multidecadal Variability (AMV), is the variability of the sea surface temperature (SST) of the North Atlantic Ocean at the timescale of several decades. The AMO is correlated to air temperatures and rainfall over much of the Northern Hemisphere, in particular in the summer climate in North America and Europe. The long-term variations of surface temperature are driven mainly by the cycles of solar activity, represented by the variations of the Total Solar Irradiance (TSI). The frequency and amplitude dependences between the TSI and AMO are analyzed by wavelet coherence of millennial time series since 800 AD till now. The results of wavelet coherence are compared with the detected common solar and climate cycles in narrow frequency bands by the method of Partial Fourier Approximation. The long-term coherence between TSI and AMO can help to understand better the recent climate change and can improve the long term forecast.