ShantanuT01/DACTYL-Pretraining huggingface dataset:
Massive stars play a dominant role in the process of clustered star formation, with their feedback into the molecular cloud through ionizing radiation, stellar winds and outflows. The formation process of massive stars is poorly constrained because of their scarcity, the short formation timescale and obscuration. By obtaining a census of the newly formed stellar population, the star formation history of the young cluster and the role of the massive stars within it can be unraveled. We aim to reconstruct the formation history of the young stellar population of the massive star-forming region RCW 36. We study several dozens of individual objects, both photometrically and spectroscopically, look for signs of multiple generations of young stars and investigate the role of the massive stars in this process. We obtain a census of the physical parameters and evolutionary status of the young stellar population. Using a combination of near-infrared photometry and spectroscopy we estimate ages and masses of individual objects. We identify the population of embedded young stellar objects (YSO) by their infrared colors and emission line spectra. RCW 36 harbors a stellar population of massive and intermediate-mass stars located around the center of the cluster. Class 0/I and II sources are found throughout the cluster. The central population has a median age of 1.1 +/- 0.6 Myr. Of the stars which could be classified, the most massive ones are situated in the center of the cluster. The central cluster is surrounded by filamentary cloud structures; within these, some embedded and accreting YSOs are found. Our age determination is consistent with the filamentary structures having been shaped by the ionizing radiation and stellar winds of the central massive stars. The formation of a new generation of stars is ongoing, as demonstrated by the presence of embedded protostellar clumps, and two exposed jets.
Context: R Coronae Borealis (RCB) variables and their non-variable counterparts, the dustless Hydrogen-Deficient Carbon (dLHdC) stars have been known to exhibit enhanced s-processed material on their surfaces, especially Sr, Y, and Ba. No comprehensive work has been done to explore the s-process in these types of stars, however one particular RCB star, U Aqr, has been under scrutiny for its extraordinary Sr enhancement. Aims: We aim to identify RCB and dLHdC stars that have significantly enhanced Sr abundances, such as U Aqr, and use stellar evolution models to begin to estimate the type of neutron exposure that occurs in a typical HdC star. Methods: We compare the strength of the Sr II 4077 $\AA$ spectral line to Ca II H to identify the new subclass of Sr-rich HdCs. We additionally use the structural and abundance information from existing RCB MESA models to calculate the neutron exposure parameter, $\tau$ Results: We identify six stars in the Sr-rich class. Two are RCBs, and four are dLHdCs. We additionally find that the preferred RCB MESA model has a neutron exposure $\tau$ ~ 0.1 mb$^{-1}$, which is lower than the estimated $\tau$ between 0.15 and 0.6 mb$^{-1}$ for the Sr-rich star U Aqr found in the literature. We find trends in the neutron exposure corresponding to He-burning shell temperature, metallicity, and assumed s-processing site. Conclusions: We have found a sub-class of 6 HdCs known as the Sr-rich class, which tend to lie in the halo, outside the typical distribution of RCBs and dLHdCs. We find that dLHdC stars are more likely to be Sr-rich than RCBs, with an occurrence rate of ~13\% for dLHdCs and ~2\% for RCBs. This is one of the first potential spectroscopic differences between RCBs and dLHdCs, along with dLHdCs having stronger surface abundances of $^{18}$O.
We present a study of graphene/substrate interactions on UHV-grown graphene islands with minimal surface contamination using \emph{in situ} low-temperature scanning tunneling microscopy (STM). We compare the physical and electronic structure of the sample surface with atomic spatial resolution on graphene islands versus regions of bare Cu(111) substrate. We find that the Rydberg-like series of image potential states is shifted toward lower energy over the graphene islands relative to Cu(111), indicating a decrease in the local work function, and the resonances have a much smaller linewidth, indicating reduced coupling to the bulk. In addition, we show the dispersion of the occupied Cu(111) Shockley surface state is influenced by the graphene layer, and both the band edge and effective mass are shifted relative to bare Cu(111).
In the context of simple models illustrating field transformations in Lagrangian field theories we discuss the impossibility of measuring off-shell effects in nucleon-nucleon bremsstrahlung, Compton scattering, and related processes. To that end we introduce a simple phenomenological Lagrangian describing nucleon-nucleon bremsstrahlung and perform an appropriate change of variables leading to different off-shell behavior in the nucleon-nucleon amplitude as well as the photon-nucleon vertex. As a result we obtain a class of equivalent Lagrangians, generating identical S-matrix elements, of which the original Lagrangian is but one representative. We make use of this property in order to show that what appears as an off-shell effect in an S-matrix element for one Lagrangian may originate in a contact term from an equivalent Lagrangian. By explicit calculation we demonstrate for the case of nucleon-nucleon bremsstrahlung as well as nucleon Compton scattering the equivalence of observables from which we conclude that off-shell effects cannot in any unambiguous way be extracted from an S-matrix element. Finally, we also discuss some implications of introducing off-shell effects on a phenomenological basis, resulting from the requirement that the description of one process be consistent with that of other processes described by the same Lagrangian.
We completely describe the components of expected dimension of the Hilbert Scheme of rational curves of fixed degree $k$ in the moduli space ${\rm SU}_{C}(r,L)$ of semistable vector bundles of rank $r$ and determinant $L$ on a curve $C$. We show that for every $k \geq 1$ there are ${\rm gcd}(r, \deg L)$ unobstructed components. In addition, if $k$ is divisible by $r_1(r-r_1)(g-1)$ for $1\le r_1\le r-1$, there is an additional obstructed component of the expected dimension for each such $r_1$. We construct families of obstructed components and show that their generic point is not the generic vector bundle of given rank and determinant. Finally, we also obtain an upper bound on the degree of rational connectedness of ${\rm SU}_{C}(r,L)$ which is linear in the dimension.
Supermassive Black Holes (BHs) residing in brightest cluster galaxies (BCGs) are overly massive when considering the local relationships between the BH mass and stellar bulge mass or velocity dispersion. Due to the location of these BHs within the cluster, large-scale cluster processes may aid the growth of BHs in BCGs. In this work, we study a sample of 71 galaxy clusters to explore the relationship between the BH mass, stellar bulge mass of the BCG, and the total gravitating mass of the host clusters. Due to difficulties in obtaining dynamically measured BH masses in distant galaxies, we use the Fundamental Plane relationship of BHs to infer their masses. We utilize X-ray observations taken by $Chandra$ to measure the temperature of the intra-cluster medium (ICM), which is a proxy for the total mass of the cluster. We analyze the $\rm M_{BH}-kT$ and $\rm M_{BH}-M_{Bulge}$ relationships and establish the best-fitting power laws:$\log_{10}(M_{\rm BH} /10^9 M_{\odot})=-0.35+2.08 \log_{10}(kT / 1 \rm keV)$ and $\log_{10}(\rm M_{BH}/10^9M_{\odot})= -1.09+ 1.92 \log_{10}(M_{\rm bulge}/10^{11}M_{\odot})$. Both relations are comparable with that established earlier for a sample of brightest group/cluster galaxies with dynamically measured BH masses. Although both the $\rm M_{BH}-kT$ and the $\rm M_{BH}-M_{Bulge}$ relationships exhibit large intrinsic scatter, based on Monte Carlo simulations we conclude that dominant fraction of the scatter originates from the Fundamental Plane relationship. We split the sample into cool core and non-cool core resembling clusters, but do not find statistically significant differences in the $\rm M_{BH}-kT$ relation. We speculate that the overly massive BHs in BCGs may be due to frequent mergers and cool gas inflows onto the cluster center.
We have detected gamma-ray emission at the 6sigma level at energies greater than 500GeV from the supernova remnant RX J0852.0-4622 (G266.2-1.2) using the CANGAROO-II Imaging Atmospheric Cherenkov Telescope (IACT). The flux was 0.12 times of that of Crab at 1TeV. The signal centroid is consistent with the peak of the X-ray emission in the north-west rim of the remnant.
The quest for understanding the late-time acceleration is haunted by an immense freedom in the analysis of dynamical models for dark energy in extended parameter spaces. Often-times having no prior knowledge at our disposal, arbitrary choices are implemented to reduce the degeneracies between parameters. We also encounter this issue in the case of quintessence fields, where a scalar degree of freedom drives the late-time acceleration. In this study, we implement a more physical prescription, the \textit{flow} condition, to fine-tune the quintessence evolution for several field potentials. We find that this prescription agrees well with the most recent catalogue of data, namely supernovae type Ia, baryon acoustic oscillations, cosmic clocks and distance to last scattering surface, and it enables us to infer the initial conditions for the field, both potential and cosmological parameters. At $2\sigma$ we find stricter bounds on the potential parameters $f/m_{pl}>0.26$ and $n<0.15$ for the PNGB and IPL potentials, respectively, while constraints on cosmological parameters remain extremely consistent across all assumed potentials. By implementing information criteria to assess their ability to fit the data, we do not find any evidence against thawing models, which in fact are statistically equivalent to $\Lambda$CDM, and the freezing ones are moderately disfavoured. Through our analysis we place upper bounds on the slope of quintessence potentials, consequently revealing a strong tension with the recently proposed swampland criterion, finding the 2$\sigma$ upper bound of $\lambda \sim 0.31$ for the exponential potential.
We describe measurements of 100 nK temperature oscillations at room temperature, driven at the complex interface between p-doped Germanium, a nm size metal layer, and an electrolyte. We show that heat is deposited at this interface by thermoelectric effects, however the precise microscopic mechanism remains to be established. The temperature measurement is accomplished by observing the modulation of black body radiation from the interface. We argue that this geometry offers a method to study molecular scale dissipation phenomena. The Debye layer on the electrolyte side of the interface controls much of the dynamics. Interpreting the measurements from first principles, we show that in this geometry the Debye layer behaves like a low frequency transmission line.
In this article, we discuss the vertex decomposability of three well-studied simplicial complexes associated to forests. In particular, we show that the bounded degree complex of a forest and the complex of directed trees of a multidiforest are vertex decomposable. We then prove that the non-cover complex of a forest is either contractible or homotopy equivalent to a sphere. Finally, we provide a complete characterization of forests whose non-cover complexes are vertex decomposable.
We define $\overline{\psi}$ to be the multiplicative arithemtic function that satisfies \[\overline{\psi}(p^{\alpha})=\begin{cases} p^{\alpha-1}(p+1), & \mbox{if } p\neq 2; \\ p^{\alpha-1}, & \mbox{if } p=2 \end{cases}\] for all primes $p$ and positive integers $\alpha$. Let $\lambda(n)$ be the number of iterations of the function $\overline{\psi}$ needed for $n$ to reach $2$. It follows from a theorem due to White that $\lambda$ is additive. Following Shapiro's work on the iterated $\varphi$ function, we determine bounds for $\lambda$. We also use the function $\lambda$ to partition the set of positive integers into three sets $S_1,S_2,S_3$ and determine some properties of these sets.
In this paper, we study the compressibility of random processes and fields, called generalized L\'evy processes, that are solutions of stochastic differential equations driven by $d$-dimensional periodic L\'evy white noises. Our results are based on the estimation of the Besov regularity of L\'evy white noises and generalized L\'evy processes. We show in particular that non-Gaussian generalized L\'evy processes are more compressible in a wavelet basis than the corresponding Gaussian processes, in the sense that their $n$-term approximation error decays faster. We quantify this compressibility in terms of the Blumenthal-Getoor index of the underlying L\'evy white noise.
We performed deep observations to search for radio pulsations in the directions of 375 unassociated Fermi Large Area Telescope (LAT) gamma-ray sources using the Giant Metrewave Radio Telescope (GMRT) at 322 and 607 MHz. In this paper we report the discovery of three millisecond pulsars (MSPs), PSR J0248+4230, PSR J1207$-$5050 and PSR J1536$-$4948. We conducted follow up timing observations for around 5 years with the GMRT and derived phase coherent timing models for these MSPs. PSR J0248$+$4230 and J1207$-$5050 are isolated MSPs having periodicities of 2.60 ms and 4.84 ms. PSR J1536-4948 is a 3.07 ms pulsar in a binary system with orbital period of around 62 days about a companion of minimum mass 0.32 solar mass. We also present multi-frequency pulse profiles of these MSPs from the GMRT observations. PSR J1536-4948 is an MSP with an extremely wide pulse profile having multiple components. Using the radio timing ephemeris we subsequently detected gamma-ray pulsations from these three MSPs, confirming them as the sources powering the gamma-ray emission. For PSR J1536-4948 we performed combined radio-gamma-ray timing using around 11.6 years of gamma-ray pulse times of arrivals (TOAs) along with the radio TOAs. PSR J1536-4948 also shows evidence for pulsed gamma-ray emission out to above 25 GeV, confirming earlier associations of this MSP with a >10 GeV point source. The multi-wavelength pulse profiles of all three MSPs offer challenges to models of radio and gamma-ray emission in pulsar magnetospheres.
Outdoor scene completion is a challenging issue in 3D scene understanding, which plays an important role in intelligent robotics and autonomous driving. Due to the sparsity of LiDAR acquisition, it is far more complex for 3D scene completion and semantic segmentation. Since semantic features can provide constraints and semantic priors for completion tasks, the relationship between them is worth exploring. Therefore, we propose an end-to-end semantic segmentation-assisted scene completion network, including a 2D completion branch and a 3D semantic segmentation branch. Specifically, the network takes a raw point cloud as input, and merges the features from the segmentation branch into the completion branch hierarchically to provide semantic information. By adopting BEV representation and 3D sparse convolution, we can benefit from the lower operand while maintaining effective expression. Besides, the decoder of the segmentation branch is used as an auxiliary, which can be discarded in the inference stage to save computational consumption. Extensive experiments demonstrate that our method achieves competitive performance on SemanticKITTI dataset with low latency. Code and models will be released at https://github.com/jokester-zzz/SSA-SC.
Intercalation is an effective method to improve and modulate properties of two-dimensional materials. Even so, spatially controlled intercalation at atomic scale, which is important to introduce and modulated properties, has not been successful due to difficulties in controlling the diffusion of intercalants. Here, we show formation of angstrom-wide conductive channels (~4.3 A) in black phosphorus by Cu intercalation. The atomic structure, resultant microstructural effects, intercalation mechanism, and local variations of electronic properties modulated in black phosphorus by Cu intercalation were investigated extensively by transmission electron microscopy including in situ observation, DFT calculation, and conductive atomic force microscopy.
Large synoptic (repeated scan) imaging sky surveys are poised to observe enormous numbers of core-collapse supernovae. We quantify the discovery potential of upcoming projects, including DES, Pan-STARRS, and LSST. These surveys will map out the cosmic core-collapse supernova redshift distribution via direct counting, with very small statistical uncertainties out to a redshift depth which is a strong function of the survey limiting magnitude. This supernova redshift history encodes rich information about cosmology, star formation, and supernova astrophysics and phenomenology; the large statistics of the supernova sample will be crucial to disentangle possible degeneracies among these issues. For example, the cosmic supernova rate can be measured to high precision out to z ~ 0.5 for all core-collapse types, and out to redshift z ~ 1 for Type IIn events. Because of the tight link between supernovae and star formation, synoptic sky surveys will provide precision measurements of the normalization and z < 1 history of cosmic star-formation rate in a manner independent of and complementary to current methods. Furthermore, Type II supernovae can serve as distance indicators and would independently cross-check Type Ia distances measured in the same surveys. Arguably the largest and least-controlled uncertainty in these efforts comes from dust obscuration of supernovae in their host galaxies; we outline a strategy to determine empirically the obscuration properties by leveraging the large supernova samples over a broad range of redshift. [abstract abridged]
Simulations of the generation of the atomic polarization is necessary for interpreting the second solar spectrum. For this purpose, it is important to rigorously determine the effects of the isotropic collisions with neutral hydrogen on the atomic polarization of the neutral atoms, ionized atoms and molecules. Our aim is to treat in generality the problem of depolarizing isotropic collisions between singly ionized atoms and neutral hydrogen in its ground state. Using our numerical code, we computed the collisional depolarization rates of the $p$-levels of ions for large number of values of the effective principal quantum number $n^{*}$ and the Uns\"old energy $E_p$. Then, genetic programming has been utilized to fit the available depolarization rates. As a result, strongly non-linear relationships between the collisional depolarization rates, $n^{*}$ and $E_p$ are obtained, and are shown to reproduce the original data with accuracy clearly better than 10\%. These relationships allow quick calculations of the depolarizing collisional rates of any simple ion which is very useful for the solar physics community. In addition, the depolarization rates associated to the complex ions and to the hyperfine levels can be easily derived from our results. In this work we have shown that by using powerful numerical approach and our collisional method, general model giving the depolarization of the ions can be obtained to be exploited for solar applications.
In the Batalin - Fradkin - Vilkovisky approach to quantization of gauge theories a principal role is given to the BRST charge which can be constructed as a series in Grassmannian (ghost) variables with coefficients given by generalized structure functions of constraints algebra. Alternatively, the BRST charge can be derived making use of the Noether theorem and global BRST invariance of the effective action. In the case of Yang - Mills fields the both methods lead to the same expression for the BRST charge, but it is not valid in the case of General Relativity. It is illustrated by examples of an isotropic cosmological model as well as by spherically-symmetric gravitational model which imitates the full theory of gravity much better. The consideration is based on Hamiltonian formulation of General Relativity in extended phase space. At the quantum level the structure of the BRST charge is of great importance since BRST invariant quantum states are believed to be physical states. Thus, the definition of the BRST charge at the classical level is inseparably related to our attempts to find a true way to quantize Gravity.
Einstein Gravitational Field Equations (EFE) of Chaplygin gas dominated Bianchi-type models are obtained by using metric approximation. The solutions of equations for a special case, namely Bianchi I model which is a generalization of isotropic Friedmann-Robertson-Walker (FRW) cosmology, are obtained. The early and late behaviours of some kinematic parameters in model are presented in graphically.
The sizes of interstellar grains are widely distributed, ranging from a few angstroms to a few micrometers. The ultraviolet (UV) and optical extinction constrains the dust in the size range of a couple hundredth micrometers to several submicrometers. The near and mid infrared (IR) emission constrains the nanometer-sized grains and angstrom-sized very large molecules. However, the quantity and size distribution of micrometer-sized grains remain unknown as they are gray in the UV/optical extinction and they are too cold and emit too little in the IR to be detected by IRAS, Spitzer, or Herschel. In this work, we employ the ~3-8 micron mid-IR extinction which is flat in both diffuse and dense regions to constrain the quantity, size, and composition of the micron-sized grain component. We find that, together with nano- and submicron-sized silicate and graphite (as well as PAHs), micron-sized graphite grains with C/H=137 ppm and a mean size of ~1.2 micron closely fit the observed interstellar extinction of the Galactic diffuse interstellar medium from the far-UV to the mid-IR as well as the near-IR to millimeter thermal emission obtained by COBE/DIRBE, COBE/FIRAS, and Planck up to lambda < 1000 micron. The micron-sized graphite component accounts for ~14.6% of the total dust mass and ~2.5% of the total IR emission.
We investigate the dynamical evolution of double-sided jets and present detailed numerical studies on the emission from the receding jet of gamma-ray bursts. It is found that the receding jet emission is generally very weak and only manifests as a plateau in the late time radio afterglow light curves. Additionally, we find that the effect of synchrotron self-absorption can influence the peak time of the receding jet emission significantly.
Joule-Thomson expansion process is studied for charged Gauss-Bonnet black holes in AdS space. Firstly, in five-dimensional space-time, the isenthalpic curve in $T-P$ graph is obtained and the cooling-heating region is determined. Secondly, the explicit expression of Joule-Thomson coefficient is obtained from the basic formulas of enthalpy and temperature. Our methods can also be applied to van der Waals system as well as other black hole systems. And the inversion curve $\tilde{T}(\tilde{P})$ which separates the cooling region and heating region is obtained and investigated. Thirdly, interesting dependence of the inversion curves on the charge $(Q)$ and the Gauss-Bonnet parameter $(\alpha)$ is revealed. In $\tilde{T}-\tilde{P}$ graph, the cooling region decreases with charge, but increases with the Gauss-Bonnet parameter. Fourthly, by applying our methods, the Joule-Thomson expansion process for $\alpha=0$ case in four dimension is studied, where the Gauss-Bonnet AdS black hole degenerates into RN-AdS black hole. The inversion curves for van der Waals systems consist of two parts. One has positive slope, while the other has negative slope. However, for black hole systems, the slopes of the inversion curves are always positive, which seems to be a universal feature.