Using the weak gravitational lensing data from the Hyper Suprime-Cam Subaru Strategic Program (HSC survey), we study the potential of different stellar mass estimates in tracing halo mass. We consider galaxies with $log {M_{star}/M_{odot}}>11.5$ at 0
.2 < z < 0.5 with carefully measured light profiles and clusters from the redMaPPer and CAMIRA richness-based algorithms. We devise a method (the TopN test) to evaluate the scatter in the halo mass-observable relation for different tracers and inter-compare halo mass proxies in four number density bins using stacked galaxy-galaxy lensing profiles. This test reveals three key findings. The stellar mass based on cModel photometry or aperture luminosity within R<30 kpc is a poor proxy of halo mass. In contrast, the stellar mass of the outer envelope is an excellent halo mass proxy. The stellar mass within R=[50,100] kpc, M*[50,100], has performance comparable to the state-of-the-art richness-based cluster finders at $log{M_{rm vir}/M_{odot}}>14.0$ and could be a better halo mass tracer at lower halo masses. Finally, using N-body simulations, we find that the lensing profiles of massive halos selected by M*[50,100] are consistent with the expectation for a sample without projection or mis-centering effects. On the other hand, Richness-selected clusters display an excess at R~1 Mpc in their lensing profiles, which may suggest a more significant impact from selection biases. These results suggest that Mstar-based tracers have distinct advantages in identifying massive halos, which could open up new avenues for cluster cosmology.
A significant fraction of binary neutron star mergers occur in star-forming galaxies where the UV-optical and soft X-ray afterglow emission from the relativistic jet may be absorbed by dust and re-emitted at longer wavelengths. We show that, for merg
ers occurring in gas-rich environment (n_H > 0.5 cm^{-3} at a few to tens of pc) and when the viewing angle is less than about 30 degrees, the emission from heated dust should be detectable by James Webb Space Telescope (JWST), with a detection rate of the order once per year. The spatial separation between the dust emission and the merger site is a few to 10 milli-arcsecs (for a source distance of 150 Mpc), which may be astrometrically resolved by JWST for sufficiently high signal-noise-ratio detections. Measuring the superluminal apparent speed of the flux centroid directly gives the orbital inclination of the merger, which can be combined with gravitational wave data to measure the Hubble constant. For a line of sight within the jet opening angle, the dust echoes are much brighter and may contaminate the search for kilonova candidates from short gamma-ray bursts, such as the case of GRB 130603B.
The recent discovery of a fast radio burst (FRB) in a globular cluster of M81 points to more than one channels for the formation of objects that produce these powerful radio pulses. Association of an FRB to a globular cluster (or other old stellar sy
stems) suggests that strongly magnetized neutron stars, which are the most likely objects responsible for these bursts, are born not only when young massive stars undergo core-collapse, but also by mergers of old white dwarfs. We find that the fractional contribution to the total FRB rate by old stellar populations is at least a few percent, and the precise fraction can be constrained by FRB searches in the directions of nearby galaxies, both star-forming and elliptical ones. Using very general arguments, we show that the activity time of the M81-FRB is between 10^4 and 10^6 years under conservative assumptions, and more likely of order 10^5 years. The energetics of radio outbursts puts a lower limit on the magnetic field strength of 10^{13} G, and the spin period > 0.2 sec, thereby ruling out the source being a milli-second pulsar. The upper limit on the persistent X-ray luminosity (provided by Chandra), together with the high FRB luminosity and frequent repetitions, severely constrains (or rules out) the possibility that the M81-FRB is a scaled-up version of giant pulses from Galactic pulsars. Finally, the 50 ns variability time of the FRB lightcurve suggests that the emission is produced in a compact region inside the neutron star magnetosphere, as it cannot be accounted for when the emission is at distances > 10^{10} cm.
In recent years many efforts have been undertaken to simplify coil designs for stellarators due to the difficulties in fabricating non-planar coils. The FOCUS code removes the need for a winding surface and represents the coils as arbitrary curves in
3D. In the following work, the implementation of a spline representation for the coils in FOCUS is described, along with the implementation of a new engineering constraint to design coils with a straighter outer section. The new capabilities of the code are shown as an example on HSX, NCSX, and a prototype quasi-axisymmetric reactor-sized stellarator. The flexibility granted by splines along with the new constraint will allow for stellarator coil designs with improved accessibility and simplified maintenance
We present an approach for maximizing a global utility function by learning how to allocate resources in an unsupervised way. We expect interactions between allocation targets to be important and therefore propose to learn the reward structure for ne
ar-optimal allocation policies with a GNN. By relaxing the resource constraint, we can employ gradient-based optimization in contrast to more standard evolutionary algorithms. Our algorithm is motivated by a problem in modern astronomy, where one needs to select-based on limited initial information-among $10^9$ galaxies those whose detailed measurement will lead to optimal inference of the composition of the universe. Our technique presents a way of flexibly learning an allocation strategy by only requiring forward simulators for the physics of interest and the measurement process. We anticipate that our technique will also find applications in a range of resource allocation problems.
Interstellar thermal pressures can be measured using C I absorption lines that probe the pressure-sensitive populations of the fine-structure levels of its ground state. In a survey of C I absorption toward Galactic hot stars, Jenkins & Tripp (2011)
found evidence of small amounts ($sim 0.05%$) of gas at high pressures ($p/k gg 10^4{rm cm^{-3}K}$) mixed with a more general presence of lower pressure material exhibiting a log normal distribution that spanned the range $10^3 lesssim p/k lesssim 10^4{rm cm^{-3}K}$. In this paper, we study Milky Way C I lines in the spectra of extragalactic sources instead of Galactic stars and thus measure the pressures without being influenced by regions where stellar mass loss and H II region expansions could create localized pressure elevations. We find that the distribution of low pressures in the current sample favors slightly higher pressures than the earlier survey, and the fraction of gaseous material at extremely high pressures is about the same as that found earlier. Thus we conclude that the earlier survey was not appreciably influenced by the stellar environments, and the small amounts of high pressure gas indeed exist within the general interstellar medium.
We present a comprehensive analysis of 20 years worth of multi-color photometric light curves, multi-epoch optical spectra, and X-ray data of an off-nuclear variable object SDSS1133 in Mrk 177 at $z=0.0079$. The UV-optical light curves reveal that SD
SS1133 experienced three outbursts in 2001, 2014, and 2019. The persistent UV-optical luminosity in the non-outbursting state is $sim 10^{41}$ erg/s with small-scale flux variations, and peak luminosities during the outbursts reach $sim 10^{42}$ erg/s. The optical spectra exhibit enduring broad hydrogen Balmer P-Cygni profiles with the absorption minimum at $sim -2,000$ km/s, indicating the presence of fast moving ejecta. Chandra detected weak X-ray emission at a 0.3-10 keV luminosity of $L_{X} = 4 times 10^{38}$ erg/s after the 2019 outburst. These lines of evidence strongly suggests that SDSS1133 is an extremely luminous blue variable (LBV) star experiencing multiple giant eruptions with interactions of the ejected shell with different shells and/or circumstellar medium (CSM), and strongly disfavors the recoiling Active Galactic Nuclei (AGN) scenario suggested in the literature. We suggest that pulsational pair-instability may provide a viable explanation for the multiple energetic eruptions in SDSS1133. If the current activity of SDSS1133 is a precursor of a supernova explosion, we may be able to observe a few additional giant eruptions and then the terminal supernova explosion in future observations.
From a new perspective, we re-examine self-gravity and turbulence jointly, in hopes of understanding the physical basis for one of the most important empirical relations governing clouds in the interstellar medium (ISM), the Larsons Relation relating
velocity dispersion ($sigma_R$) to cloud size ($R$). We report on two key new findings. First, the correct form of the Larsons Relation is $sigma_R=alpha_v^{1/5}sigma_{pc}(R/1pc)^{3/5}$, where $alpha_v$ is the virial parameter of clouds and $sigma_{pc}$ is the strength of the turbulence, if the turbulence has the Kolmogorov spectrum. Second, the amplitude of the Larsons Relation, $sigma_{pc}$, is not universal, differing by a factor of about two between clouds on the Galactic disk and those at the Galactic center, evidenced by observational data.
This document is the final report of the Community Planning Process (CPP) that describes a comprehensive plan to deliver fusion energy and to advance plasma science. The CPP was initiated by the executive committee of the American Physical Society Di
vision of Plasma Physics (APS DPP) to help the Fusion Energy Sciences Advisory Committee (FESAC) fulfill a charge from the U.S. Department of Energy (DOE) to develop a strategic plan for the DOE Office of Fusion Energy Sciences (FES). In this charge, dated Nov 30, 2018, DOE Deputy Director for Science Dr. Stephen Binkley requested that FESAC undertake a new long range strategic planning activity for the Fusion Energy Sciences (FES) program. The strategic planning activity to encompass the entire FES research portfolio (namely, burning plasma science and discovery plasma science) should identify and prioritize the research required to advance both the scientific foundation needed to develop a fusion energy source, as well as the broader FES mission to steward plasma science. The CPP represents the first phase in developing a long range strategic plan for FES, and will serve as the basis for the second phase activity conducted by FESAC. It is worth noting that enacting the full scope of the recommendations in the strategic plan in this document will require suitable partnerships with other offices and governmental agencies, as well as with private industry and international partners.
We study ErdH oss distinct distances problem under $ell_p$ metrics with integer $p$. We improve the current best bound for this problem from $Omega(n^{4/5})$ to $Omega(n^{6/7-epsilon})$, for any $epsilon>0$. We also characterize the sets that span an
asymptotically minimal number of distinct distances under the $ell_1$ and $ell_infty$ metrics.
