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This paper presents the multiscale temperature structures in the Milky Way (MW) hot gas, as part of the XMM-Newton Line Emission Analysis Program, surveying the O vii, O viii, and Fe-L band emission features in the XMM-Newton archive. In particular, we define two temperature tracers, I OVIII/ I OVII (O87) and I FeL/(I OVII + I OVIII) (FeO). These two ratios cannot be explained simultaneously using single-temperature collisional ionization models, which indicates the need for multitemperature structures in hot gas. In addition, we show three large-scale features in the hot gas: the eROSITA bubbles around the Galactic center (GC), the disk, and the halo. In the eROSITA bubbles, the observed line ratios can be explained by a log-normal temperature distribution with a median of log T / K ≈ 6.4 and a scatter of σ T ≈ 0.2 dex. Beyond the bubbles, the line ratio dependence on the Galactic latitude suggests higher temperatures around the midplane of the MW disk. The scale height of the temperature variation is estimated to be ≈2 kpc assuming an average distance of 5 kpc for the hot gas. The halo component is characterized by the dependence on the distance to the GC, showing a temperature decline from log T / K ≈ 6.3 to 5.8. Furthermore, we extract the autocorrelation and cross-correlation functions to investigate the small-scale structures. O87 and FeO ratios show a consistent autocorrelation scale of ≈5° (i.e., ≈400 pc at 5 kpc), which is consistent with the expected physical sizes of X-ray bubbles associated with star-forming regions or supernova remnants. Finally, we examine the cross-correlation between the hot and UV-detected warm gas and show an intriguing anticorrelation. [ABSTRACT FROM AUTHOR]

Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we have recorded over 1.2 × 104 single pulses from PSR B0823+26 (J0826+2637) at 1.25 GHz with 500 MHz bandwidth. These high-sensitivity observations detected with FAST are unprecedented. We investigated potentially interesting emission features by analyzing the polarimetric individual pulses during the bright state. The average pulse profile has a weak postcursor component and a wide interpulse along with a narrow main pulse. The pulse energy distribution of the main pulse shows the presence of triple emission modes. When the emission ceases in the main pulse component, low-level emission in the interpulse component is detected, whereas the absence of any emission in the postcursor component is shown. In the postcursor emission region, bright pulses are detected in 422 rotations with the relative pulse energy described by a power-law distribution with index of −2.52 ± 0.09, while the peak flux density ratio appears to follow a logarithmic normal distribution. The intervals between bright pulses can be described with a Poisson process with the occurrence rate estimated to be one bright pulse every 14 s. The fluctuation spectral analysis reveals the existence of a form of periodic amplitude modulation unrelated to subpulse drifting in both the main pulse and interpulse components. Furthermore, the modulation patterns in the main pulse and interpulse are found to be locked in pulse longitude, signifying some information transfer between the two magnetic polar regions. [ABSTRACT FROM AUTHOR]

We investigated the probability distributions of sunspot area and magnetic flux by using data from the Royal Greenwich Observatory and USAF/NOAA. We constructed a sample of 2995 regions with maximum-development areas ≥500 MSH (millionths of solar hemisphere), covering 146.7 yr (1874–2020). The data were fitted by a power-law distribution and four two-parameter distributions (tapered-power-law, gamma, lognormal, and Weibull distributions). The power-law model was unfavorable compared to the four models in terms of AIC, and was not acceptable according to the classical Kolmogorov–Smirnov test. The lognormal and Weibull distributions were excluded because their behavior extended to smaller regions (S ≪ 500 MSH) do not connect to previously published results. Therefore, our choices were tapered-power-law and gamma distributions. The power-law portion of the tapered-power-law and gamma distributions was found to have a power exponent of 1.35–1.9. Due to the exponential falloff of these distributions, the expected frequencies of large sunspots are low. The largest sunspot group observed had an area of 6132 MSH, and the frequency of sunspots larger than 104 MSH was estimated to be every 3–8 × 104 yr. We also estimated the distributions of the Sun-as-a-star total sunspot areas. The largest total area covered by sunspots on record was 1.67% of the visible disk, and can be up to 2.7% by artificially increasing the lifetimes of large sunspots in an area evolution model. These values are still smaller than those found on active Sun-like stars. [ABSTRACT FROM AUTHOR]

Quasi-periodic pulsations (QPPs) with various periods that originate in the underlying magnetohydrodynamic processes of flaring structures are detected repeatedly in solar flare emissions. We apply a 2D cellular automaton (CA) avalanche model to simulate QPPs as a result of a repetitive load/unload mechanism. We show that the frequent occurrence of magnetic reconnections in a flaring loop could induce quasi-periodic patterns in the detected emissions. We find that among 21,070 simulated flares, 813 events last over 50 s, scaled with the temporal resolution of the Yohkoh Hard X-ray Telescope, and about 70% of these rather long-lasting events exhibit QPPs. We also illustrate that the applied CA model provides a wide range of periodicities for QPPs. Furthermore, we observe the presence of multiple periods in nearly 50% of the cases by applying the Lombâ€"Scargle periodogram. A lognormal distribution is fitted to the unimodal distribution of the periods as a manifestation of an underlying multiplicative mechanism that typifies the effect of the system’s independently varying parameters. The global maximum of the periods’ lognormal distribution is located at 29.29 ± 0.67 s. We compare statistics of the simulated QPPs with parameters of the host flares and discuss the impacts of flare properties on the periods of QPPs. Considering the intrinsic characteristic of CA models, namely the repetitive load/unload mechanism, and the obtained pieces of evidence, we suggest that CA models may generate QPPs. We also examine the applicability of autoregressive integrated moving average models to describe the simulated and observed QPPs. [ABSTRACT FROM AUTHOR]

Electron-scale magnetic peaks (ESMPs) with spatial sizes less than one local ion gyroradius have been recently revealed to exist in the terrestrial magnetosheath and solar wind at 1 au. Whether they widely exist in the astrophysical plasma is unclear. Here, we investigate the magnetic peaks with a period of 0.1â€"100 s upstream of Mercury’s bow shock by using the magnetic field data from the MESSENGER spacecraft. Based on the distribution of their durations, these magnetic peaks can be divided into two groups: one with durations less than 0.6 s and the other with durations larger than 0.6 s. The durations in each group obey a log-normal distribution. The magnetic peaks with durations less than 0.6 s are inferred to be electron scale, suggesting that ESMPs exist in the solar wind at Mercury’s orbit. The median duration of these ESMPs is ∼0.3 s. The ESMPs have a larger occurrence rate near the bow shock and prefer to occur when the ambient interplanetary magnetic field (IMF) can be connected to the bow shock, which suggests that the foreshock could be one source region of these ESMPs. Their occurrence rate also tends to be larger when the IMF strength is weaker. Our observations also suggest that some ESMPs originate from the upstream solar wind. The properties of the ESMPs found here could help to shed light on their generation mechanisms and their roles in the astrophysical plasma. [ABSTRACT FROM AUTHOR]

We have developed a tracking algorithm to determine the speeds of supra-arcade downflows (SADs) and set up a system to automatically track SADs and measure some interesting parameters. By conducting an analysis of six flares observed by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory, we detect more smaller and slower SADs than prior work, due to the higher spatial resolution of our observational data. The inclusion of these events with smaller and slower SADs directly results in lower median velocities and widths than in prior work, but the fitted distributions and evolutions of the parameters still show good consistency with prior work. The observed distributions of the widths, speeds, and lifetimes of SADs are consistent with log-normal distributions, indicating that random and unstable processes are responsible for generating SADs during solar eruptions. Also, we find that the fastest SADs occur at approximately the middle of the height ranges. The number of SADs in each image versus time shows that there are “rest phases” of SADs, when few SADs are seen. These findings support the idea that SADs originate from a fluid instability. We compare our results with a numerical simulation that generates SADs using a mixture of the Rayleighâ€"Taylor instability and the Richtmyerâ€"Meshkov instability, and find that the simulation generates quantities that are consistent with our observational results. [ABSTRACT FROM AUTHOR]

Long-term γ-ray variability of a non-blazar Active Galactic Nucleus PKS 0521-36 is investigated by using Fermi Large Area Telescope (Fermi-LAT) pass 8 data covering from 2008 August to 2021 March. The results show that the histogram of the γ-ray fluxes follows a log-normal distribution. Interestingly, in the analysis of ∼5.8 yr (from MJD 56317–58447) LAT data between two outbursts (occurring during 2012 October and 2019 May respectively), a quasi-periodic oscillation (QPO) with a period of ∼1.1 yr (∼5σ of significance) is found in the Lomb–Scargle Periodogram (LSP), the Weighted Wavelet Z-transform, and the REDFIT results. This quasiperiodic signal also appears in the results of Gaussian process modeling the light curve. Therefore, the robustness of the QPO is examined by four different methods. This is the first γ-ray QPO found in a mildly beamed jet. Our results imply that the γ-ray outbursts play an important role in the formation of the γ-ray QPO. [ABSTRACT FROM AUTHOR]

We report on the detection of 146 (0.96%) bright pulses with a peak flux density >0.86 Jy from PSR B0031–07 in 4 hr of continuous observations made at 4.82 GHz, with a bandwidth of 1 GHz, using the Shanghai Tian Ma 65 m radio telescope. We find that the peak flux density distribution follows a power law with index α = −3.6 ± 0.2, while the pulse energy appears to follow a logarithmic normal distribution. The bright pulses from PSR B0031–07 were observed to repeat in an irregular fashion. The intervals between bright pulses can be described with an exponentiated Weibull distribution. Furthermore, the sensitive observations at higher frequency with a short time resolution of 65.54 μs form a reliable basis for detailed microstructure studies. Close inspection of the detected bright pulses reveals that 38 pulses exhibit well-defined quasi-periodicities. No unanimous period for the quasi-periodicities is found, and the peak flux density is independent of the micropulse width. Finally, possible physical mechanisms are discussed. [ABSTRACT FROM AUTHOR]

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 found evidence of small amounts (∼0.05%) of gas at high pressures () mixed with a more general presence of lower pressure material exhibiting a log-normal distribution that spanned the range. 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. [ABSTRACT FROM AUTHOR]

We study the dependence of Lyα escape from galaxies on UV continuum size and luminosity using a sample of 40 Green Pea (GP) galaxies, which are the best local analogs of high-redshift Lyα emitters (LAEs). We use the Cosmic Origins Spectrograph near-ultraviolet images from the Hubble Space Telescope to measure the UV size and luminosity with 0.″047 spatial resolution. Like most galaxies the GPs show a log-normal size distribution. They also show a positive correlation between size and UV-continuum luminosity. The slope of the size-continuum luminosity relation for GPs is consistent with those of continuum-selected star-forming galaxies (SFGs) at low and high redshifts. A distinctive feature of GPs is a very compact typical radius of 0.33 kpc with a population spread (1σ) of 0.19 kpc. The peak of the size distribution and the intercept of the size–luminosity relation of GPs are noticeably smaller than those of continuum-selected SFGs at similar redshifts. There are statistically significant anticorrelations found between the circularized half-light radius (rcir,50), the Lyα equivalent width (EW(Lyα)), and the Lyα escape faction (), suggesting that small UV-continuum radii are crucial for Lyα emission. GPs and high-redshift LAEs have similar sizes, once spatial resolution effects are properly considered. Our results show that a compact small size is crucial for escape of Lyα photons, and that Lyα emitters show constant characteristic size independent of their redshift. [ABSTRACT FROM AUTHOR]

The ubiquitous relativistic jet phenomena associated with black holes play a major role in high and very-high-energy (VHE) astrophysics. In particular, observations have demonstrated that blazars show VHE emission with time variability from days to minutes (in the gigaelectronvolt and teraelectronvolt bands), implying very compact emission regions. The real mechanism of the particle acceleration process responsible for this emission is still being debated, but magnetic reconnection has lately been discussed as a strong potential candidate. In this work, we present the results of three-dimensional special relativistic magnetohydrodynamic simulations of the development of reconnection events driven by turbulence induced by current-driven kink instability along a relativistic jet. We have performed a systematic identification of all reconnection regions in the system, characterizing their local magnetic field topology and quantifying the reconnection rates. We obtained average rates of 0.051 ± 0.026 (in units of Alfvén speed), which are comparable to the predictions of the theory of turbulence-induced fast reconnection. A detailed statistical analysis also demonstrated that the fast reconnection events follow a log-normal distribution, which is a signature of its turbulent origin. To probe the robustness of our method, we have applied our results to the blazar Mrk 421. Building a synthetic light curve from the integrated magnetic reconnection power, we evaluated the time variability from a power spectral density analysis, obtaining good agreement with observations in the gigaelectronvolt band. This suggests that turbulent fast magnetic reconnection can be a possible process behind the high-energy emission variability phenomena observed in blazars. [ABSTRACT FROM AUTHOR]

The dark matter halos that surround Milky Way–like galaxies in cosmological simulations are, to first order, triaxial. Nearly 30 yr ago it was predicted that such triaxial dark matter halos should exhibit steady figure rotation or tumbling motions for durations of several gigayears. The angular frequency of figure rotation predicted by cosmological simulations is described by a log-normal distribution of pattern speed Ωp with a median value 0.15 h km s−1 kpc−1 (∼0.15 h rad Gyr−1 ∼ 9° h Gyr−1) and a width of 0.83h km s−1 kpc−1. These pattern speeds are so small that they have generally been considered both unimportant and undetectable. In this work we show that even extremely slow figure rotation can significantly alter the structure of extended stellar streams produced by the tidal disruption of satellites in the Milky Way halo. We simulate the behavior of a Sagittarius-like polar tidal stream in triaxial dark matter halos with different shapes, when the halos are rotated about the three principal axes. For pattern speeds typical of cosmological halos, we demonstrate, for the first time, that a Sagittarius-like tidal stream would be altered to a degree that is detectable even with current observations. This discovery will potentially allow for a future measurement of figure rotation of the Milky Way's dark matter halo, perhaps enabling the first evidence of this relatively unexplored prediction of cold dark matter. [ABSTRACT FROM AUTHOR]

We investigate the dispersion measure (DM) and scattering of fast radio bursts (FRBs) by the intergalactic medium (IGM), foreground halos, and host halos using cosmological hydrodynamical simulation. We find that the median DM caused by foreground halos is around 30% of that caused by the IGM, but it has a much larger variance. The DM induced by hosts deviates from a log-normal distribution but exhibits an extended distribution in the range of with a median value. Then we produce mock FRB sources, assuming a uniform distribution in the range , to consider the propagation effect of IGM, foreground, and host halos on FRB signals simultaneously. The DM distribution of mock sources agrees well with the observation. The fitted DM–redshift relation of the mock sources can provide a rough estimation of the redshifts of observed events with errors. The distribution of mock sources in the DM scattering time (τ) space can also match the observation, assuming a Kolmogorov turbulence model where the inner and outer scales are 1000 km to 1 au and 0.2–10 pc, respectively. Finally, we estimate the relative importance of these media for DM and τ in our models. The IGM and host halos are the primary and secondary sources for the extragalactic DM (). Meanwhile, the contribution from foreground halos increases as increases. The host and foreground halos may be the most important media for scattering. Statistically, the latter may dominate the scattering of events with. [ABSTRACT FROM AUTHOR]

We use daily observations from the Royal Greenwich Observatory and Kislovodsk Mountain Astronomical Station of Pulkovo Observatory to study the distribution properties of sunspot areas. To mitigate the poor statistics in the distribution of small areas, we introduce a "precision randomization" approach based on the assumption that all measured areas have a random component within the measurement uncertainty of 1 millionth of the solar hemisphere (M.S.H.). We confirm the presence of two distinct components in the distribution of sunspots previously reported by several authors, and show that the area distribution is described by the sum of two lognormal distributions responsible for small and large groups (sunspots), respectively. We also demonstrate that the area of the main spots in the groups correlates well with the total area of the group, and, thus, the findings derived for the total group areas are equally applicable to the main spots of groups. [ABSTRACT FROM AUTHOR]

We show that the growth rate of dust grains in cold molecular clouds is enhanced by the high degree of compressibility of a turbulent, dilute gas. By means of high-resolution (10243) numerical simulations, we confirm the theory that the spatial mean growth rate is proportional to the gas-density variance. This also results in broadening of the grain-size distribution (GSD) due to turbulence-induced variation of the grain-growth rate. We show, for the first time in a detailed numerical simulation of hydrodynamic turbulence, that the GSD evolves toward a shape that is a reflection of the gas-density distribution, regardless of the initial distribution. That is, in case of isothermal, rotationally forced turbulence, the GSD tends to be a lognormal distribution. We also show that in hypersonic turbulence, decoupling of gas and dust becomes important and that this leads to an even further accelerated grain growth. [ABSTRACT FROM AUTHOR]

We present a catalog of probabilistic redshift estimates for 1366 individual Long-duration Gamma-ray Bursts (LGRBs) detected by the Burst And Transient Source Experiment (BATSE). This result is based on a careful selection and modeling of the population distribution of 1366 BATSE LGRBs in the five-dimensional space of redshift and the four intrinsic prompt gamma-ray emission properties: the isotropic 1024 ms peak luminosity (), the total isotropic emission (), the spectral peak energy (), as well as the intrinsic duration (), while carefully taking into account the effects of sample incompleteness and the LGRB-detection mechanism of BATSE. Two fundamental plausible assumptions underlie our purely probabilistic approach: (1) LGRBs trace, either exactly or closely, the cosmic star formation rate, with a possibility of the excess rates of LGRBs in the nearby universe, and (2) the joint four-dimensional distribution of the aforementioned prompt gamma-ray emission properties is well described by a multivariate log-normal distribution. Our modeling approach enables us to constrain the redshifts of individual BATSE LGRBs to within 0.36 and 0.96 average uncertainty ranges at 50% and 90% confidence levels, respectively. Our redshift predictions are completely at odds with the previous redshift estimates of BATSE LGRBs that were computed via the proposed phenomenological high-energy relations, specifically, the apparently strong correlation of LGRBs' peak luminosity with the spectral peak energy, lightcurve variability, and spectral lag. The observed discrepancies between our predictions and the previous works can be explained by the strong influence of detector threshold and sample incompleteness in shaping these phenomenologically proposed high-energy correlations in the literature. Finally, we also discuss the potential effects of an excess cosmic rate of LGRBs at low redshifts and the possibility of a luminosity evolution of LGRBs on our results. [ABSTRACT FROM AUTHOR]

A broad and widely used class of stationary, linear, additive time-series models can have statistical properties that many authors have asserted imply that the underlying process must be nonlinear, nonstationary, multiplicative, or inconsistent with shot noise. This result is demonstrated with exact and numerical evaluation of the model flux distribution function and dependence of flux standard deviation on mean flux (here and in the literature called the rms–flux relation). These models can (1) exhibit normal, lognormal, or other flux distributions; (2) show linear or slightly nonlinear rms–mean flux dependencies; and (3) match arbitrary second-order statistics of the time-series data. Accordingly, the above assertions cannot be made on the basis of statistical time-series analysis alone. Also discussed are ambiguities in the meaning of terms relevant to this study—linear, stationary, and multiplicative—and functions that can transform observed fluxes to a normal distribution as well as or better than the logarithm. [ABSTRACT FROM AUTHOR]

A determination of the mass function (MF) of stellar clusters can be quite dependent on the range of measured masses, the fitting technique, and the analytic function that is being fit to the data. Here, we use Hubble Space Telescope/WFPC2 data of NGC 1711, a stellar cluster in the Large Magellanic Cloud, as a test case to explore a range of possible determinations of the MF from a single data set. We employ the analytic modified lognormal power-law (MLP) distribution, a hybrid function that has a peaked lognormal-like body and a power-law tail at intermediate and high masses. A fit with the MLP has the advantage that the resulting best-fit function can be either a hybrid function, a pure lognormal, or a pure power law, in different limits of the function. The completeness limit for the observations means that the data contains masses above ∼0.90 M⊙. In this case, the MLP fits yield essentially a pure power-law MF. We demonstrate that the nonlinear regression/least-squares approach is not justified since the underlying assumptions are not satisfied. By using maximum-likelihood estimation, which is independent of binning, we find a best-fit functional form , where α = 1.72 ± 0.05 or 1.75 ± 0.05 for two different theoretical isochrone models, respectively. Furthermore, we explore the possibility of systematic errors in the determination of the power-law index due to the depth of the observations. When we combine the observational data with artificially generated data from the lognormal Chabrier initial MF for masses below 0.90M⊙, the best-fit MLP is a hybrid function but with a steeper asymptotic slope i.e., α = 2.04 ± 0.07. This illustrates the systematic uncertainties in commonly used MF parameters that can depend on the range of data that is fitted. [ABSTRACT FROM AUTHOR]

Small-amplitude quasi-periodic pulsations (QPPs) detected in soft X-ray emission are commonplace in many flares. To date, the underpinning processes resulting in the QPPs are unknown. In this paper, we attempt to constrain the prevalence of stationary QPPs in the largest statistical study to date, including a study of the relationship of QPP periods to the properties of the flaring active region, flare ribbons, and coronal mass ejection (CME) affiliation. We build upon the work of Inglis et al. and use a model comparison test to search for significant power in the Fourier spectra of lightcurves of the GOES 1–8 Å channel. We analyze all X-, M- and C-class flares of the past solar cycle, a total of 5519 flares, and search for periodicity in the 6–300 s timescale range. Approximately 46% of X-class, 29% of M-class, and 7% of C-class flares show evidence of stationary QPPs, with periods that follow a log-normal distribution peaked at 20 s. The QPP periods were found to be independent of flare magnitude; however, a positive correlation was found between QPP period and flare duration. No dependence of the QPP periods on the global active region properties was identified. A positive correlation was found between QPPs and ribbon properties, including unsigned magnetic flux, ribbon area, and ribbon separation distance. We found that both flares with and without an associated CME can host QPPs. Furthermore, we demonstrate that for X- and M-class flares, decay-phase QPPs have statistically longer periods than impulsive-phase QPPs. [ABSTRACT FROM AUTHOR]

We analyze the distribution of CO brightness temperature and integrated intensity in M51 at ∼40 pc resolution using new 12CO(J = 1 → 0) data from the Plateau de Bure Arcsecond Whirlpool Survey (PAWS). We present probability distribution functions (PDFs) of the CO emission within the PAWS field of view, which covers the inner ∼11 × 7 kpc of M51. We find clear variations in the shape of CO PDFs both within different M51 environments, defined according to dynamical criteria, and among M51 and two nearby low-mass galaxies, M33 and the Large Magellanic Cloud (LMC). Globally, the PDFs for the inner disk of M51 can be represented by narrow lognormal functions that cover ∼1-2 orders of magnitude in CO brightness and integrated intensity. The PDFs for M33 and the LMC are narrower and peak at lower CO intensities, consistent with their lower gas surface densities. However, the CO PDFs for different dynamical environments within the PAWS field depart significantly from the shape of the global distribution. The PDFs for the interarm region are approximately lognormal, but in the spiral arms and central region of M51, they exhibit diverse shapes with a significant excess of bright CO emission. The observed environmental dependence on the shape of the CO PDFs is qualitatively consistent with changes that would be expected if molecular gas in the spiral arms is characterized by a larger range of average densities, gas temperatures, and velocity fluctuations, although further work is required to disentangle the relative importance of large-scale dynamical effects versus star formation feedback in regulating these properties. We show that the shape of the CO PDFs for different M51 environments is only weakly related to global properties of the CO emission, e.g., the total CO luminosity, but is strongly correlated with properties of the local giant molecular cloud (GMC) and young stellar cluster populations, including the shape of their mass distributions. For galaxies with strong spiral structure such as M51, our results indicate that galactic-scale dynamical processes play a significant role in the formation and evolution of GMCs and stellar clusters. [ABSTRACT FROM AUTHOR]

It is proposed that the luminosity function, the rest-frame spectral correlations, and distributions of cosmological long-duration (Type-II) gamma-ray bursts (LGRBs) may be very well described as a multivariate log-normal distribution. This result is based on careful selection, analysis, and modeling of LGRBs' temporal and spectral variables in the largest catalog of GRBs available to date: 2130 BATSE GRBs, while taking into account the detection threshold and possible selection effects. Constraints on the joint rest-frame distribution of the isotropic peak luminosity (Liso), total isotropic emission (Eiso), the time-integrated spectral peak energy (Ep,z), and duration (T90,z) of LGRBs are derived. The presented analysis provides evidence for a relatively large fraction of LGRBs that have been missed by the BATSE detector with Eiso extending down to ~1049 erg and observed spectral peak energies (Ep) as low as ~5 keV. LGRBs with rest-frame duration T90,z ≲ 1 s or observer-frame duration T90 ≲ 2 s appear to be rare events (≲0.1% chance of occurrence). The model predicts a fairly strong but highly significant correlation (ρ = 0.58 ± 0.04) between Eiso and Ep,z of LGRBs. Also predicted are strong correlations of Liso and Eiso with T90,z and moderate correlation between Liso and Ep,z. The strength and significance of the correlations found encourage the search for underlying mechanisms, though undermine their capabilities as probes of dark energy's equation of state at high redshifts. The presented analysis favors--but does not necessitate--a cosmic rate for BATSE LGRBs tracing metallicity evolution consistent with a cutoff Z/Z☉ ~ 0.2-0.5, assuming no luminosity-redshift evolution. [ABSTRACT FROM AUTHOR]

The initial mass function for stars is usually fitted by three straight lines, which means it has seven parameters. The presence of brown dwarfs (BDs) increases the number of straight lines to four and the number of parameters to nine. Another common fitting function is the lognormal distribution, which is characterized by two parameters. This paper is devoted to demonstrating the advantage of introducing a left truncated beta probability density function, which is characterized by four parameters. The constant of normalization, the mean, the mode, and the distribution function are calculated for the left truncated beta distribution. The normal beta distribution that results from convolving independent normally distributed and beta distributed components is also derived. The chi-square test and the Kolmogorov-Smirnov test are performed on a first sample of stars and BDs that belongs to the massive young cluster NGC 6611, and on a second sample that represents the masses of the stars of the cluster NGC 2362. [ABSTRACT FROM AUTHOR]

Motivated by recent results on lognormal statistics showing that the moment hierarchy of a lognormal variable completely fails at capturing its information content in the large variance regime, in this work we discuss the inadequacy of the hierarchy of correlation functions to describe a correlated lognormal field, which provides a roughly accurate description of the nonlinear cosmological matter density field. We present families of fields having the same hierarchy of correlation functions than the lognormal field at all orders. This explicitly demonstrates the little studied though known fact that the correlation function hierarchy never provides a complete description of a lognormal field, and that it fails to capture information in the nonlinear regime, where other simple observables are left totally unconstrained. We discuss why perturbative, Edgeworth-like approaches to statistics in the nonlinear regime, common in cosmology, can never reproduce or predict that effect, and why it is, however, generic for tailed fields, hinting at a breakdown of the perturbation theory based on the field fluctuations. We make a rough but successful quantitative connection to N-body simulations results that showed that the spectrum of the log-density field carries more information than the spectrum of the field entering the nonlinear regime. [ABSTRACT FROM AUTHOR]

We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of ≿5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars. Several other low-redshift WLQ candidates have normal ratios of X-ray-to-optical/UV flux, and their average X-ray spectral properties are also similar to those of typical radio-quiet quasars. The X-ray weak and X-ray normalWLQ candidates may belong to the same subset of quasars having high-ionization "shielding gas" covering most of the wind-dominated broad emission-line region, but be viewed at different inclinations. The mid-infrared-to-X-ray spectral energy distributions (SEDs) of these sources are generally consistent with those of typical SDSS quasars, showing that they are not likely to be BL Lac objects with relativistically boosted continua and diluted emission lines. The mid-infrared-to-UV SEDs of most radio-quiet weak-featured AGNs without sensitive X-ray coverage (34 objects) are also consistent with those of typical SDSS quasars. However, one source in our X-ray-observed sample is remarkably strong in X-rays, indicating that a small fraction of low-redshift WLQ candidates may actually be BL Lac objects residing in the radio-faint tail of the BL Lac population. We also investigate universal selection criteria for WLQs over a wide range of redshift, finding that it is not possible to select WLQ candidates in a fully consistent way using different prominent emission lines (e.g., Lyα, C IV, Mg II, and Hβ) as a function of redshift. [ABSTRACT FROM AUTHOR]

We analyze the "microscale fluctuations" of the magnetic field strength B on a scale of several hours observed by Voyager1 (V1) in the heliosheath during 2009. The microscale fluctuations of B range from coherent to stochastic structures. The amplitude of microscale fluctuations of B during 1 day is measured by the standard deviation (SD) of 48 s averages of B. The distribution of the daily values of SD is lognormal. SD(t) from day of year (DOY) 1 to 331, 2009, is very intermittent. SD(t) has a 1/f or "pink noise" spectrum on scales from 1 to 100 days, and it has a broad multifractal spectrum f(α) with 0.57 ≤ α ≤ 1.39. The time series of increments SD(t + τ) -- SD(t) has a pink noise spectrum with α' = 0.88 ± 0.14 on scales from 1 to 100 days. The increments have a Tsallis (q-Gaussian) distribution on scales from 1 to 165 days, with an average q = 1.75 ± 0.12. The skewness S and kurtosis K have Gaussian and lognormal distributions, respectively. The largest spikes in K(t) and S(t) are often associated with a change in B across a data gap and with identifiable physical structures. The "turbulence" observed by V1 during 2009 was weakly compressible on average but still very intermittent, highly variable, and highly compressible at times. The turbulence observed just behind the termination shock by Voyager 2 was twice as strong. These observations place strong constraints on any model of "turbulence" in the heliosheath. [ABSTRACT FROM AUTHOR]

We trace with analytical methods and in a model parameter-independent manner the independent bits of Fisher information of each of the moments of the lognormal distribution as a now standard prescription for the distribution of the cosmological matter density field as it departs from Gaussian initial conditions. We show that, when entering the regime of large fluctuations, only a tiny, dramatically decaying fraction of the total information content remains accessible through the extraction of the full series of moments of the field. This is due to the known peculiarity of highly tailed distributions that they cannot be uniquely recovered given the values of all of their moments. Under this lognormal assumption, cosmological probes such as the correlation function hierarchy or, equivalently, their Fourier transforms, are rendered fundamentally limited once the field becomes nonlinear, for any parameter of interest. We show that the fraction of the information accessible from two-point correlations decays to zero following the inverse squared variance of the field. We discuss what general properties of a random field's probability density function are making the correlation function hierarchy an efficient or inefficient, complete or incomplete, set of probes of any model parameter. [ABSTRACT FROM AUTHOR]

The matter density field exhibits a nearly lognormal probability density distribution after entering into the nonlinear regime. Recently, it has been shown that the shape of the power spectrum of a logarithmically transformed density field is very close to the linear density power spectrum, motivating an analytic study of it. In this paper, we develop cosmological perturbation theory for the power spectrum of this field. Our formalism is developed in the context of renormalized perturbation theory, which helps to regulate the convergence behavior of the perturbation series, and of the Taylor series expansion we use for the logarithmic mapping. This approach allows us to handle the critical issue of density smoothing in a straightforward way. We also compare our perturbative results with simulation measurements. [ABSTRACT FROM AUTHOR]

We present an in-depth and systematic variability study of a sample of 20 powerful blazars, including 12 BL Lacs and 8 flat-spectrum radio quasars, applying various analysis tools such as flux distribution, symmetry analysis, and time-series analysis on the decade-long Fermi/LAT observations. The results show that blazars with steeper γ-ray spectral indexes are found to be more variable, and the γ-ray flux distribution closely resembles a log-normal probability distribution function. The statistical variability properties of the sources as studied by power spectral density analysis are consistent with flicker noise (P(ν) ∝ 1/ν)—an indication of long-memory processes at work. Statistical analysis of the distribution of flux rise and decay rates in the light curves of the sources, aimed at distinguishing between particle acceleration and energy-dissipation timescales, counterintuitively suggests that both kinds of rates follow a similar distribution and the derived mean variability timescales are on the order of a few weeks. The corresponding emission region size is used to constrain the location of γ-ray production sites in the sources to be a few parsecs. Additionally, using Lomb–Scargle periodogram and weighted wavelet z-transform methods and extensive Monte Carlo simulations, we detected year-timescale quasi-periodic oscillations in the sources S5 0716+714, Mrk 421, ON +325, PKS 1424−418, and PKS 2155−304. The detection significance was computed taking proper account of the red noise and other artifacts inherent in the observations. We explain the results in light of current blazar models with relativistic shocks propagating down the jet viewed close to the line of sight. [ABSTRACT FROM AUTHOR]

Chondrules are approximately millimeter-sized beads of crystallized silicate melt. They formed mainly in the first ∼3 Ma of the Sun's protoplanetary disk and are the main constituents of chondritic asteroids. Here we report on the size–frequency distributions (2D and 3D) of chondrules in the brecciated ordinary chondrite (OC) Northwest Africa (NWA) 5205. We investigated three large (centimeter- to decimeter-sized) chondritic lithic clasts of a particular textural type ("cluster chondrite") with eye-catching different chondrule sizes. One clast shows the largest mean chondrule size (∼1.5 mm) ever measured in a chondrite. As in the other OCs, we find a positive correlation between the minimum and mean chondrule size, which we consider as an argument for chondrule size sorting. Chondrule size–frequency distributions in the clasts are distinctly more symmetric than the about log-normal distributions in other OCs. Furthermore, we find a co-enrichment of chondrule types with a priori small mean sizes (type I, porphyritic) in clasts with overall small mean chondrule sizes. We consider this as the fingerprint of an additional/second size-sorting process, which acted later on these chondrule populations. This process possibly subdivided a typical LL-type chondrule population into several subpopulations with different mean chondrule sizes. We speculate that this second sorting occurred in a unidirectional gas stream or headwind, e.g., by settling of chondrules through an asteroidal atmosphere or interaction with an expanding impact plume. Possibly, fine-grained matrix was almost completely removed by this, and the size-sorted chondrule subpopulations accreted in a hot state separately in different regions of the asteroid. [ABSTRACT FROM AUTHOR]

In many statistical solar flare studies, power laws are claimed and exponents derived by fitting a line to a log–log histogram. It is well known that this approach is statistically unstable, and very large statistics are needed to produce reliable exponent estimates. This may explain part of the observed divergence in power-law exponents in various studies. Moreover, the question is seldom addressed to what extent the data really do support power-law behavior. In this paper, we perform a comprehensive study of 6924 flares detected in SDO/AIA 9.4 nm images by the Solar Demon flare detection software between 2010 May 13 and 2018 March 16 and 9601 flares detected during the same period in GOES/XRS data by the LYRAFF flare detection software. We apply robust statistics to the SDO/AIA 9.4 nm peak intensity and the GOES/XRS raw peak flux, background-subtracted peak flux, and background-subtracted fluence and find clear indications that most background-corrected data are not well described by a power law and that all are better described by a lognormal distribution, while the raw GOES/XRS peak flux is best described by a power law. This may explain the success of power-law fits in flare studies using uncorrected data. The behavior of flare distributions has important implications for large-scale science questions such as coronal heating and the nature of solar flares. The apparent lognormal character of flare distributions in our data sets suggests that the assumed power-law nature of flares and its consequences need to be reexamined with great care. [ABSTRACT FROM AUTHOR]

The typical blazar S5 0716+714 is very interesting due to its rapid and large-amplitude variability and high duty cycle of microvariability in the optical band. We analyze the observations in the I, R, and V bands obtained with the 1.0 m telescope at Weihai observatory of Shandong University from 2011 to 2018. The model of synchrotron radiation from turbulent cells in a jet has been proposed as a mechanism for explaining microvariability seen in blazar light curves. Parameters such as the sizes of turbulent cells, the enhanced particle densities, and the location of the turbulent cells in the jet can be studied using this model. The model predicts a time lag between variations, as observed in different frequency bands. An automatic model fitting method for microvariability is developed, and the fitting results of our multi-frequency microvariability observations support the model. The results show that both the amplitude and duration of flares decomposed from the microvariability light curves conform to the log-normal distribution. The turbulent cell size is within the range of about 5–55 au, and the time lags of the microvariability flares between the I–R and R–V bands should be several minutes. The time lags obtained from the turbulence model are consistent with the fitting statistical results, and the time lags of flares are correlated with the time lags of the whole light curve. [ABSTRACT FROM AUTHOR]

Based on the early-year observations from Neil Gehrels Swift Observatory, Liang et al. performed a systematic analysis for the shallow decay component of gamma-ray bursts (GRBs) X-ray afterglow, in order to explore its physical origin. Here we revisit the analysis with an updated sample (with Swift/XRT GRBs between 2004 February and 2017 July). We find that with a larger sample, (1) the distributions of the characteristic properties of the shallow decay phase (e.g., tb, SX, ΓX,1, and αX,1) still accord with normal or lognormal distribution; (2) ΓX,1 and Γγ still show no correlation, but the tentative correlations of durations, energy fluences, and isotropic energies between the gamma-ray and X-ray phases still exist; (3) for most GRBs, there is no significant spectral evolution between the shallow decay segment and its follow-up segment, and the latter is usually consistent with the external-shock models; (4) assuming that the central engine has a power-law luminosity release history as , we find that the value q is mainly distributed between −0.5 and 0.5, with an average value of 0.16 ± 0.12; (5) the tentative correlation between and disappears, so that the global three-parameter correlation () becomes less significant; (6) the anticorrelation between LX and and the three-parameter correlation () indeed exist with a high confidence level. Overall, our results are generally consistent with Liang et al., confirming their suggestion that the shallow decay segment in most bursts is consistent with an external forward shock origin, probably due to a continuous energy injection from a long-lived central engine. [ABSTRACT FROM AUTHOR]

Observations of various molecular lines toward a disk region of a nearby galaxy are now feasible, and they are being employed as diagnostic tools to study star formation activities there. However, the spatial resolution attainable for a nearby galaxy with currently available radio telescopes is 10–1000 pc, which is much larger than the scales of individual star-forming regions and molecular-cloud cores. Hence, it is of fundamental importance to elucidate which part of an interstellar medium such spatially unresolved observations are tracing. Here we present sensitive measurements of the H2CO () line at 72 GHz toward giant molecular clouds (GMCs) in the spiral arm of M51 using the NRO 45 m and IRAM 30 m telescopes. In conjunction with the previously observed H2CO (202 − 101) and CS (2 − 1 and 3 − 2) lines, we derive the H2 density of the emitting regions to be (0.6–2.6) × 104 cm−3 and (2.9–12) × 104 cm−3 for H2CO and CS, respectively, by the non-LTE analyses, where we assume the source size of 0.8–1 kpc and the gas kinetic temperature of 10–20 K. The derived H2 density indicates that the emission of H2CO and CS is not localized to star-forming cores, but is likely distributed over an entire region of GMCs. Such widespread distributions of H2CO and CS are also supported by models assuming lognormal density distributions over the 1 kpc region. Thus, contributions from the widespread less dense components should be taken into account for interpretation of the molecular emission observed with a GMC-scale resolution. The different H2 densities derived for H2CO and CS imply their different distributions. We discuss these differences in terms of the formation processes of H2CO and CS. [ABSTRACT FROM AUTHOR]

We have conducted a large-field simultaneous survey of 12CO, 13CO, and C18O J = 1 − 0 emission toward the Cassiopeia A (Cas A) supernova remnant (SNR), which covers a sky area of 3.°5 × 3.°1. The Cas giant molecular cloud (GMC) mainly consists of three individual clouds with masses on the order of 104−105 M☉. The total mass derived from the 13CO emission of the GMC is 2.1 × 105 M☉ and is 9.5 × 105 M☉ from the 12CO emission. Two regions with broadened (6–7 km s−1) or asymmetric 12CO line profiles are found in the vicinity (within a 10′ × 10′ region) of the Cas A SNR, indicating possible interactions between the SNR and the GMC. Using the GAUSSCLUMPS algorithm, 547 13CO clumps are identified in the GMC, 54% of which are supercritical (i.e., αvir < 2). The mass spectrum of the molecular clumps follows a power-law distribution with an exponent of −2.20. The pixel-by-pixel column density of the GMC can be fitted with a log-normal probability distribution function (N-PDF). The median column density of molecular hydrogen in the GMC is 1.6 × 1021 cm−2 and half the mass of the GMC is contained in regions with H2 column density lower than 3 × 1021 cm−2, which is well below the threshold of star formation. The distribution of the YSO candidates in the region shows no agglomeration. [ABSTRACT FROM AUTHOR]

We present the results of a suite of numerical simulations designed to explore the origin of the angular momenta of protostellar cores. Using the hydrodynamic grid code Athena with a sink implementation, we follow the formation of protostellar cores and protostars (sinks) from the subvirial collapse of molecular clouds on larger scales to investigate the range and relative distribution of core properties. We find that the core angular momenta are relatively unaffected by large-scale rotation of the parent cloud; instead, we infer that angular momenta are mainly imparted by torques between neighboring mass concentrations and exhibit a log-normal distribution. Our current simulation results are limited to size scales ∼0.05 pc (∼104 au), but serve as first steps toward the ultimate goal of providing initial conditions for higher-resolution studies of core collapse to form protoplanetary disks. [ABSTRACT FROM AUTHOR]

Relativistic outflows are believed to be a common feature of black hole X-ray binaries (BHXBs) at the lowest accretion rates, when they are in their “quiescent” spectral state. However, we still lack a detailed understanding of how quiescent jet emission varies with time. Here we present 24 yr of archival radio observations (from the Very Large Array and the Very Long Baseline Array) of the BHXB V404 Cygni in quiescence (totaling 150 observations from 1.4 to 22 GHz). The observed flux densities follow lognormal distributions with means and standard deviations of and at 4.9 and 8.4 GHz, respectively (where fν is the flux density in units of mJy). As expected, the average radio spectrum is flat with a mean and standard deviation of , where . We find that radio flares that increase the flux density by factors of 2–4 over timescales as short as <10 minutes are commonplace, and that long-term variations (over 10–4000 day timescales) are consistent with shot-noise impulses that decay to stochastic variations on timescales ≲10 days (and perhaps as short as tens of minutes to several hr). We briefly compare the variability characteristics of V404 Cygni to jetted active galactic nuclei, and we conclude with recommendations on how to account for variability when placing quiescent BHXB candidates with radio luminosities comparable to V404 Cygni (LR ≈ 1028 erg s−1) onto the radio/X-ray luminosity plane. [ABSTRACT FROM AUTHOR]

There are various ways of describing intermittent features in space plasma turbulence, but we lack a unified paradigm to connect the results from these different approaches. In this work, we aim to construct a unified paradigm to describe various intermittency-related quantities with the same set of parameters. The Castaing function, which describes the scale-dependent turbulence amplitude as a logarithmic normal distribution, is adopted as a fitting function to describe the probability distribution of magnetic field difference at various timescales τ. Two fitting parameters (μ, λ) as a function of τ are obtained and regarded as the fundamental information, based on which various characteristics related to intermittency can be derived at one time, e.g., the high-order structure functions, their scaling exponent as a function of the order, or the flatness as a function of τ. We find it is the derivative ratio, DR = , that determines the order trend of the scaling exponent ζ(m). A negative DR of a small absolute is responsible for a curved ζ(m) in the inertial range, and a large positive DR leads to a straight ζ(m) in the kinetic range. Therefore, it is suggested that the probability distribution function of the magnetic increments spreads in width (λ(τ)) with decreasing τ in the inertial range, while it is saturated and even slightly reduced in the kinetic range. Moreover, it is found that the turnings between the inertial and kinetic scales for the two Castaing fitting parameters μ(τ) and λ2(τ) occur at different scales: lnτ ∼ 0 and lnτ ∼ 2, respectively. The reason for this different behavior is still unclear. [ABSTRACT FROM AUTHOR]

Rotating radio transients (RRATs) are a sub-class of pulsars characterized by sporadic emission and thus can generally only be studied by analysis of their single pulses. Here we present a single-pulse analysis using 11 years of timing data at 1400 MHz of three RRATs, PSRs J1819−1458, J1317−5759, and J1913+1330. We perform a spectral analysis on the single pulses of these RRATs for the first time, finding their mean spectral indices to be −1.1 ± 0.1, −0.6 ± 0.1, and −1.2 ± 0.2 respectively, within the known range of pulsar spectral indices. We find no evidence for narrowband features as seen for FRB 121102. However, we find the spread of single-pulse spectral indices for these RRATs (ranging from −7 to +4) to be larger than has been seen in other pulsars, with the exception of the Crab pulsar. We also analyze the time between detected pulses, or wait time, and find that the pulses are not random and cluster around wait times of a few pulse periods as well as ∼25 pulse periods for PSRs J1819−1458 and J1317−5759. Additionally we find that there is no correlation between the wait time and pulse flux density. Finally we find that the distribution of the pulse energy for PSRs J1317−5759 and J1913+1330 are log-normal, while that of PSR J1819−1458 is log-normal with possible evidence of an additional power-law component. [ABSTRACT FROM AUTHOR]

Observations of globular clusters show that they have universal lognormal mass functions with a characteristic peak at , but the origin of this peaked distribution is highly debated. Here we investigate the formation and evolution of star clusters (SCs) in interacting galaxies using high-resolution hydrodynamical simulations performed with two different codes in order to mitigate numerical artifacts. We find that massive SCs in the range of form preferentially in the highly shocked regions produced by galaxy interactions. The nascent cluster-forming clouds have high gas pressures in the range of , which is times higher than the typical pressure of the interstellar medium but consistent with recent observations of a pre-super-SC cloud in the Antennae Galaxies. Furthermore, these massive SCs have quasi-lognormal initial mass functions with a peak around . The number of clusters declines with time due to destructive processes, but the shape and the peak of the mass functions do not change significantly during the course of galaxy collisions. Our results suggest that gas-rich galaxy mergers may provide a favorable environment for the formation of massive SCs such as globular clusters, and that the lognormal mass functions and the unique peak may originate from the extreme high-pressure conditions of the birth clouds and may survive the dynamical evolution. [ABSTRACT FROM AUTHOR]

We have measured the probability distribution function (PDF) of a cosmic matter density field from a suite of N-body simulations. We propose the generalized normal distribution of version 2 () as an alternative fitting formula to the well-known log-normal distribution. We find that provides a significantly better fit than that of the log-normal distribution for all smoothing radii (2, 5, 10, 25 [Mpc h−1]) that we studied. The improvement is substantial in the underdense regions. The development of non-Gaussianities in the cosmic matter density field is captured by continuous evolution of the skewness and shift parameters of the distribution. We present the redshift evolution of these parameters for aforementioned smoothing radii and various background cosmology models. All the PDFs measured from large and high-resolution N-body simulations that we use in this study can be obtained from the web site https://astro.kias.re.kr/jhshin. [ABSTRACT FROM AUTHOR]

We discuss magnetic field and plasma observations of the heliosheath made by Voyager 2 (V2) during 2013 and 2014 near solar maximum. A transition from a unipolar region to a sector zone was observed in the azimuthal angle λ between ∼2012.45 and 2013.82. The distribution of λ was strongly singly peaked at in the unipolar region and double peaked in the sector zone. The δ-distribution was strongly peaked in the unipolar region and very broad in the sector zone. The distribution of daily averages of the magnetic field strength B was Gaussian in the unipolar region and lognormal in the sector zone. The correlation function of B was exponential with an e-folding time of ∼5 days in both regions. The distribution of hourly increments of B was a Tsallis distribution with nonextensivity parameter q = 1.7 ± 0.04 in the unipolar region and q = 1.44 ± 0.12 in the sector zone. The CR–B relationship qualitatively describes the 2013 observations, but not the 2014 observations. A 40 km s−1 increase in the bulk speed associated with an increase in B near 2013.5 might have been produced by the merging of streams. A “D sheet” (a broad depression in B containing a current sheet moved past V2 from days 320 to 345, 2013. The R- and N-components of the plasma velocity changed across the current sheet. [ABSTRACT FROM AUTHOR]

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of these data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius. [ABSTRACT FROM AUTHOR]

We construct an analytic phenomenological model for extended warm/hot gaseous coronae of L* galaxies. We consider UV O vi Cosmic Origins Spectrograph (COS)-Halos absorption line data in combination with Milky Way (MW) X-ray O vii and O viii absorption and emission. We fit these data with a single model representing the COS-Halos galaxies and a Galactic corona. Our model is multi-phased, with hot and warm gas components, each with a (turbulent) log-normal distribution of temperatures and densities. The hot gas, traced by the X-ray absorption and emission, is in hydrostatic equilibrium in an MW gravitational potential. The median temperature of the hot gas is K and the mean hydrogen density is . The warm component as traced by the O vi, is gas that has cooled out of the high density tail of the hot component. The total warm/hot gas mass is high and is . The gas metallicity we require to reproduce the oxygen ion column densities is 0.5 solar. The warm O vi component has a short cooling time ( years), as hinted by observations. The hot component, however, is of the total gas mass and is relatively long-lived, with years. Our model supports suggestions that hot galactic coronae can contain significant amounts of gas. These reservoirs may enable galaxies to continue forming stars steadily for long periods of time and account for “missing baryons” in galaxies in the local universe. [ABSTRACT FROM AUTHOR]

We present the discovery of 15 extremely low-mass () white dwarf (WD) candidates, 9 of which are in ultra-compact double-degenerate binaries. Our targeted extremely low-mass Survey sample now includes 76 binaries. The sample has a lognormal distribution of orbital periods with a median period of 5.4 hr. The velocity amplitudes imply that the binary companions have a normal distribution of mass with 0.76 M⊙ mean and 0.25 M⊙ dispersion. Thus extremely low-mass WDs are found in binaries with a typical mass ratio of 1:4. Statistically speaking, 95% of the WD binaries have a total mass below the Chandrasekhar mass, and thus are not type Ia supernova progenitors. Yet half of the observed binaries will merge in less than 6 Gyr due to gravitational wave radiation; probable outcomes include single massive WDs and stable mass transfer AM CVn binaries. [ABSTRACT FROM AUTHOR]

The distribution of orbital period ratios of adjacent planets in extrasolar planetary systems discovered by the Kepler space telescope exhibits a peak near ∼1.5–2, a long tail of larger period ratios, and a steep drop-off in the number of systems with period ratios below ∼1.5. We find from these data that the dimensionless orbital separations have an approximately log-normal distribution. Using Hill’s criterion for the dynamical stability of two planets, we find an upper bound on planet masses such that the most common planet mass does not exceed , or about two-thirds of Jupiter’s mass for solar-mass stars. Assuming that the mass ratio and the dynamical separation (orbital spacings in units of mutual Hill radius) of adjacent planets are independent random variates, and adopting empirical distributions for these, we use Hill’s criterion in a statistical way to estimate the planet mass distribution function from the observed distribution of orbital separations. We find that the planet mass function is peaked in logarithm of mass, with a peak value and standard deviation of of and , respectively. [ABSTRACT FROM AUTHOR]

We use the distance probability density function formalism of Ellsworth-Bowers et al. to derive physical properties for the collection of 1,710 Bolocam Galactic Plane Survey (BGPS) version 2 sources with well-constrained distance estimates. To account for Malmquist bias, we estimate that the present sample of BGPS sources is 90% complete above and 50% complete above . The mass distributions for the entire sample and astrophysically motivated subsets are generally fitted well by a lognormal function, with approximately power-law distributions at high mass. Power-law behavior emerges more clearly when the sample population is narrowed in heliocentric distance (power-law index for sources nearer than 6.5 kpc and for objects between 2 and 10 kpc). The high-mass power-law indices are generally for various subsamples of sources, intermediate between that of giant molecular clouds and the stellar initial mass function. The fit to the entire sample yields a high-mass power-law . Physical properties of BGPS sources are consistent with large molecular cloud clumps or small molecular clouds, but the fractal nature of the dense interstellar medium makes it difficult to map observational categories to the dominant physical processes driving the observed structure. The face-on map of the Galactic disk’s mass surface density based on BGPS dense molecular cloud structures reveals the high-mass star-forming regions W43, W49, and W51 to be prominent mass concentrations in the first quadrant. Furthermore, we present a 0.25 kpc resolution map of the dense gas mass fraction across the Galactic disk that peaks around 5%. [ABSTRACT FROM AUTHOR]

We numerically study the thermal pressure distribution in a gas with thermal properties similar to those of the cold neutral interstellar gas by analyzing three-dimensional hydrodynamic models in boxes with sides of 100 pc with turbulent compressible forcing at 50 pc and different Mach numbers. We find that at high pressures and for large Mach numbers, both the volume-weighted and the density-weighted distributions can be appropriately described by a log-normal distribution, whereas for small Mach numbers they are better described by a power law. Thermal pressure distributions resulting from similar simulations but with self-gravity differ only for low Mach numbers; in this case, they develop a high pressure tail. [ABSTRACT FROM AUTHOR]