We construct dynamical models of the Milky Way's box/peanut (B/P) bulge, using the recently measured 3D density of red clump giants (RCGs) as well as kinematic data from the Bulge Radial Velocity ...Assay (BRAVA) survey. We match these data using the nmagic made-to-measure method, starting with N-body models for barred discs in different dark matter haloes. We determine the total mass in the bulge volume of the RCGs measurement ( ± 2.2 × ±1.4 × ±1.2 kpc) with unprecedented accuracy and robustness to be 1.84 ± 0.07 × 1010 M⊙. The stellar mass in this volume varies between 1.25 and 1.6 × 1010 M⊙, depending on the amount of dark matter in the bulge. We evaluate the mass-to-light and mass-to-clump ratios in the bulge and compare them to theoretical predictions from population synthesis models. We find a mass-to-light ratio in the K band in the range 0.8–1.1. The models are consistent with a Kroupa or Chabrier initial mass function (IMF), but a Salpeter IMF is ruled out for stellar ages of 10 Gyr. To match predictions from the Zoccali IMF derived from the bulge stellar luminosity function requires ∼40 per cent or ∼ 0.7 × 1010 M⊙ dark matter in the bulge region. The BRAVA data together with the RCGs 3D density imply a low pattern speed for the Galactic B/P bulge of Ωp = 25-30 km s− 1 kpc− 1. This would place the Galaxy among the slow rotators (
$\mathcal {R}\ge 1.5$
). Finally, we show that the Milky Way's B/P bulge has an off-centred X structure, and that the stellar mass involved in the peanut shape accounts for at least 20 per cent of the stellar mass of the bulge, significantly larger than previously thought.
We present an approach for recognizing multi-stroke hand-drawn symbols. The main feature of the approach is its capacity of recognizing partially drawn symbols. Furthermore, it is invariant with ...respect to scale, and supports symbol recognition independently from the number and order of strokes. The recognition technique is based on subgraph isomorphism and exploits a novel spatial descriptor, based on polar histograms, to represent relations between two stroke primitives. Using different symbol sets, both hand-drawn and artificially deformed, we evaluated the effectiveness of the approach in recognizing the symbols as a function of the number of primitives already drawn by the users. The results show that the approach gives a satisfactory recognition rate with partially drawn symbols, also with a very low level of drawing completion, and outperforms the existing approaches proposed in the literature. We also report the results of a user study aimed at evaluating whether the users can efficiently exploit symbol autocompletion.
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•We present an approach for recognizing multi-stroke partially drawn symbols.•It is invariant with respect to scale, number and order of strokes.•It exploits a novel spatial descriptor to represent relations between two primitives.•It is effective and efficient enough to enable the design of a system for symbol autocompletion.•It outperforms the existing approaches in the recognition of partially drawn symbols.
We propose adjustable phase shift pilots (APSPs) for channel acquisition in wideband massive multiple-input multiple-output (MIMO) systems employing orthogonal frequency division multiplexing (OFDM) ...to reduce the pilot overhead. Based on a physically motivated channel model, we first establish a relationship between channel space-frequency correlations and the channel power angle-delay spectrum in the massive antenna array regime, which reveals the channel sparsity in massive MIMO-OFDM. With this channel model, we then investigate channel acquisition, including channel estimation and channel prediction, for massive MIMO-OFDM with APSPs. We show that channel acquisition performance in terms of sum mean square error can be minimized if the user terminals' channel power distributions in the angle-delay domain can be made nonoverlapping with proper pilot phase shift scheduling. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The performance of APSPs is investigated for both one symbol and multiple symbol data models. Simulations demonstrate that the proposed APSP approach can provide substantial performance gains in terms of achievable spectral efficiency over the conventional phase shift orthogonal pilot approach in typical mobility scenarios.
The present work interrogates the history of Confederate memorializations by examining the relationship between these memorializations and lynching, an explicitly racist act of violence. We obtained ...and merged data on Confederate memorializations at the county level and lynching victims, also at the county level. We find that the number of lynching victims in a county is a positive and significant predictor of the number of Confederate memorializations in that county, even after controlling for relevant covariates. This finding provides concrete, quantitative, and historically and geographically situated evidence consistent with the position that Confederate memorializations reflect a racist history, one marred by intentions to terrorize and intimidate Black Americans in response to Black progress.
We present a model for producing tidal streams from disrupting progenitors in arbitrary potentials, utilizing the idea that the majority of stars escape from the progenitor's two Lagrange points. The ...method involves releasing test particles at the Lagrange points as the satellite orbits the host and dynamically evolving them in the potential of both host and progenitor. The method is sufficiently fast to allow large-dimensional parameter exploration using Monte Carlo methods. We provide the first direct modelling of 6D stream observations – assuming a stream rather than an orbit – by applying our methods to GD-1. This is a kinematically cold stream spanning 60° of the sky and residing in the outer Galaxy ≈15 kpc distant from the centre. We assume the stream moves in a flattened logarithmic potential characterized by an asymptotic circular velocity v
0 and a flattening q. We recover values of normalization v
0 =
$227.2^{+15.6}_{-18.2}$
kms−1 and flattening q =
$0.91^{+0.04}_{-0.1}$
, if the stream is assumed to be leading, and v
0 =
$226.5^{+17.9}_{-17.0}$
kms−1, q =
$0.90^{+0.05}_{-0.09}$
, if it is assumed to be trailing. This can be compared to the values v
0 = 224 ± 13 kms−1 and
$q= 0.87^{+0.07}_{-0.04}$
obtained by Koposov et al. using the simpler technique of orbit fitting. Although there are differences between stream and orbit fitting, we conclude that orbit fitting can provide accurate results given the current quality of the data, at least for this kinematically cold stream in this logarithmic model of the Galaxy.
Cosmological simulations of the low-density intergalactic medium exhibit a strikingly tight power-law relation between temperature and density that holds over two decades in density. It is found that ...this relation should roughly apply Δz ∼ 1–2 after a reionization event, and this limiting behaviour has motivated the power-law parameterizations used in most analyses of the Ly α forest. This relation has been explained by using equations linearized in the baryonic overdensity (which does not address why a tight power-law relation holds over two decades in density) or by equating the photoheating rate with the cooling rate from cosmological expansion (which we show is incorrect). Previous explanations also did not address why recombination cooling and Compton cooling off of the cosmic microwave background, which are never negligible, do not alter the character of this relation. We provide an understanding for why a tight power-law relation arises for unshocked gas at all densities for which collisional cooling is unimportant. We also use our results to comment on (1) how quickly fluctuations in temperature redshift away after reionization processes, (2) how much shock heating occurs in the low-density intergalactic medium, and (3) how the temperatures of collapsing gas parcels evolve.
We have found a rotationally split series of core g-mode triplets and surface p-mode multiplets in a main-sequence F star, KIC 9244992. Comparison with models shows that the star has a mass of about ...1.45 M..., and is at an advanced stage of main-sequence evolution in which the central hydrogen abundance mass fraction is reduced to about 0.1. This is the second case, following KIC 11145123, of an asteroseismic determination of the rotation of the deep core and surface of an A-F main-sequence star. We have found, essentially model independently, that the rotation near the surface, obtained from p-mode splittings, is 66?d, slightly slower than the rotation of 64 d in the core, measured by g-mode splittings. KIC 9244992 is similar to KIC 11145123 in that both are near the end of main-sequence stage with very slow and nearly uniform rotation. This indicates the angular momentum transport in the interior of an A-F star during the main-sequence stage is much stronger than that expected from standard theoretical formulations. (ProQuest: ... denotes formulae/symbols omitted.)
A detailed spectroscopic analysis of SN 1986G has been performed. SN 1986G 'bridges the gap' between normal and subluminous Type Ia supernovae (SNe Ia). The abundance tomography technique is used to ...determine the abundance distribution of the elements in the ejecta. SN 1986G was found to be a low-energy Chandrasekhar mass explosion. Its kinetic energy was 70 per cent of the standard W7 model (0.9 x 10 super( 51) erg). Oxygen dominates the ejecta from the outermost layers down to ~9000 km s super( -1), intermediate mass elements (IMEs) dominate from ~9000 to ~3500 km s super( -1) with Ni and Fe dominating the inner layers < ~3500 km s super( -1). The final masses of the main elements in the ejecta were found to be, O = 0.33 M..., IME = 0.69 M..., stable NSE = 0.21 M..., super( 56)Ni = 0.14 M... An upper limit of the carbon mass is set at C = 0.02 M... The spectra of SN 1986G consist of almost exclusively singly ionized species. SN 1986G can be thought of as a low-luminosity extension of the main population of SN Ia, with a large deflagration phase that produced more IMEs than a standard SN Ia. (ProQuest: ... denotes formulae/symbols omitted.)
The requirements for facilitating spectral efficiency and energy efficiency become increasing important for future wireless networks. Ambient backscatter communication (AmBC) has recently been ...recognized as a technology to meet these requirements. Furthermore, reconfigurable intelligent surfaces (RISs) have recently emerged as an effective technology to ameliorate the performance of wireless communications. Motivated by these, this letter investigates the channel characterization and the performance of the RIS-assisted AmBC system. Particularly, we derive the closed-form expressions of the outage probability (OP) and average symbol error rate (ASER) of the considered system. To gain insight into the systems, the asymptotic OP and diversity order are obtained too. Monte Carlo simulations are employed to verify our obtained analytical result. Our findings unveil that the performance of the RIS-assisted AmBC systems is significantly better than that of the conventional AmBC system.
We have observed 99 mid-infrared-bright, massive young stellar objects and compact H ii regions drawn from the Red MSX source survey in the J = 3−2 transition of 12CO and 13CO, using the James Clerk ...Maxwell Telescope. 89 targets are within 6 kpc of the Sun, covering a representative range of luminosities and core masses. These constitute a relatively unbiased sample of bipolar molecular outflows associated with massive star formation. Of these, 59, 17 and 13 sources (66, 19 and 15 per cent) are found to have outflows, show some evidence of outflow, and have no evidence of outflow, respectively. The time-dependent parameters of the high-velocity molecular flows are calculated using a spatially variable dynamic time-scale. The canonical correlations between the outflow parameters and source luminosity are recovered and shown to scale with those of low-mass sources. For coeval star formation, we find the scaling is consistent with all the protostars in an embedded cluster providing the outflow force, with massive stars up to ∼30 M⊙ generating outflows. Taken at face value, the results support the model of a scaled-up version of the accretion-related outflow-generation mechanism associated with discs and jets in low-mass objects with time-averaged accretion rates of ∼10−3 M⊙ yr−1 on to the cores. However, we also suggest an alternative model, in which the molecular outflow dynamics are dominated by the entrained mass and are unrelated to the details of the acceleration mechanism. We find no evidence that outflows contribute significantly to the turbulent kinetic energy of the surrounding dense cores.
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