Miracle-dz/UniFAR-FTUs huggingface dataset:
Testing the universality of the IMF with Bayesian statistics: young clusters

The universality of the stellar initial mass function (IMF) is tested using Bayesian statistics with a sample of eight young stellar clusters (IC 348, ONC, NGC 2024, NGC 6611, NGC 2264, ρ Ophiuchi, Chameleon I, and Taurus). We infer the posterior probability distribution function (pPDF) of the IMF parameters when the likelihood function is described by a tapered power law function, a lognormal distribution at low masses coupled to a power law at higher masses, and a multi-component power law function. The inter-cluster comparison of the pPDFs of the IMF parameters for each likelihood function shows that these distributions do not overlap within the 1σ uncertainty level. Furthermore, the most probable values of the IMF parameters for most of the clusters deviate substantially from their values for the Galactic field stellar IMF. We also quantify the effects of taking into account the completeness correction as well as the uncertainties on the measured masses. The inclusion of the former affects the inferred pPDFs of the slope of the IMF at the low mass end while considering the latter affects the pPDFs of the slope of the IMF in the intermediate- to high mass regime. As variations are observed in all of the IMF parameters at once and for each of the considered likelihood functions, even for completeness corrected samples, we argue that the observed variations are real and significant, at least for the sample of eight clusters considered in this work. The results presented here clearly show that the IMF is not universal.
Rhizospheres of Rubus ellipticus and Ageratina riparia from Meghalaya exhibit Actinomycetota that promote plant growth

The mounting pressure on food security due to the increasing human population and climate change has prompted environment-friendly approaches to increase food crop productivity. Medicinal plant-associated microorganisms offer a solution due to their capability to antagonize phytopathogens and promote plant growth. Rhizosphere-dwelling Actinomycetota, which are mostly Gram-positive bacteria with high DNA G + C content, are potential plant growth promoters and biocontrol agents. Due to the infancy of research in medicinal plant-associated rhizosphere Actinomycetota, especially in the state of Meghalaya, India, they were isolated from the rhizospheres of two medicinal plants, Rubus ellipticus and Ageratina riparia, from Meghalaya, and the isolates were evaluated for their antimicrobial and plant growth-promoting (PGP) activities. Several antimicrobial Amycolatopsis strains were isolated from the rhizosphere of R. ellipticus and PGP Streptomyces strains from the rhizosphere of A. riparia . Five isolates were selected and tested for their ability to promote plant growth on tomato plants. All of them could significantly increase seedling vigor and plant growth on soil amended with organic manure. Plant-associated Actinomycetota from the rhizospheres of the two medicinal plants, therefore, exhibited their potential as bioinoculants that can be further developed and applied for increased crop productivity and for the maintenance of food security.
Simulating the H2 content of high-redshift galaxies

We introduce a sub-grid model for the non-equilibrium abundance of molecular hydrogen in cosmological simulations of galaxy formation. We improve upon previous work by accounting for the unresolved structure of molecular clouds in a phenomenological way which combines both observational and numerical results on the properties of the turbulent interstellar medium. We apply the model to a cosmological simulation of the formation of a Milky-Way-sized galaxy at z=2, and compare the results to those obtained using other popular prescriptions that compute the equilibrium abundance of H2. In these runs we introduce an explicit link between star formation and the local H2 abundance, and perform an additional simulation in which star formation is linked directly to the density of cold gas. In better agreement with observations, we find that the simulated galaxy produces less stars and harbors a larger gas reservoir when star formation is regulated by molecular hydrogen. In this case, the galaxy is composed of a younger stellar population as early star formation is inhibited in small, metal poor dark-matter haloes which cannot efficiently produce H2. The number of luminous satellites orbiting within the virial radius of the galaxy at z=2 is reduced by 10-30 per cent in models with H2-regulated star formation.
CANGAROO-III Observations of the 2006 Outburst of PKS 2155–304

We have used the CANGAROO-III imaging atmospheric Cerenkov telescopes to observe the high-frequency-peaked BL Lacertae (HBL) object PKS 2155–304 between 2006 July 28 (MJD 53,944) and August 2, triggered by the H.E. S.S. report that the source was in a high state of TeV gamma-ray emission. A signal was detected at the 4.8 σ level in an effective live time of 25.1 hr during the outburst period. The flux of very high energy gamma rays from the CANGAROO-III observations shows variability on the timescale of less than a few hours. The averaged integral flux above 660 GeV is (1.6 ± 0.3stat± 0.5syst) × 10−11 cm−2 s−1, which corresponds to ~45% of the flux observed from the Crab Nebula. Follow-up observations between August 17 (MJD 53,964) and 25 indicate that the source activity had decreased.
Large group delay in a microwave metamaterial analog of electromagnetically induced transparency

We report on our experimental work concerning a planar metamaterial exhibiting classical electromagnetically induced transparency (EIT). Using a structure with two mirrored split-ring resonators as the dark element and a cut wire as the radiative element, we demonstrate that an EIT-like resonance can be achieved without breaking the symmetry of the structure. The mirror symmetry of the metamaterial's structural element results in a selection rule inhibiting magnetic dipole radiation for the dark element, and the increased quality factor leads to low absorption (<10%) and large group index (of the order of 30).
New constraints on the average escape fraction of Lyman continuum radiation in z~4 galaxies from the VIMOS Ultra Deep Survey (VUDS)

Determining the average fraction of Lyman continuum (LyC) photons escaping high redshift galaxies is essential for understanding how reionization proceeded in the z>6 Universe. We want to measure the LyC signal from a sample of sources in the Chandra Deep Field South (CDFS) and COSMOS fields for which ultra-deep VIMOS spectroscopy as well as multi-wavelength Hubble Space Telescope (HST) imaging are available. We select a sample of 46 galaxies at $z\sim 4$ from the VIMOS Ultra Deep Survey (VUDS) database, such that the VUDS spectra contain the LyC part of the spectra, that is, the rest-frame range $880-910\AA$. Taking advantage of the HST imaging, we apply a careful cleaning procedure and reject all the sources showing nearby clumps with different colours, that could potentially be lower-redshift interlopers. After this procedure, the sample is reduced to 33 galaxies. We measure the ratio between ionizing flux (LyC at $895\AA$) and non-ionizing emission (at $\sim 1500 \AA$) for all individual sources. We also produce a normalized stacked spectrum of all sources. Assuming an intrinsic average $L_{\nu}(1470)/L_{\nu}(895)$ of 3, we estimate the individual and average relative escape fraction. We do not detect ionizing radiation from any individual source, although we identify a possible LyC emitter with very high Ly$\alpha$ equivalent width (EW). From the stacked spectrum and assuming a mean transmissivity for the sample, we measure a relative escape fraction $f_{esc}^{rel}=0.09\pm0.04$. We also look for correlations between the limits in the LyC flux and source properties and find a tentative correlation between LyC flux and the EW of the Ly$\alpha$ emission line. Our results imply that the LyC flux emitted by $V=25-26$ star-forming galaxies at z$\sim$4 is at most very modest, in agreement with previous upper limits from studies based on broad and narrow band imaging.
How Gas Accretion Feeds Galactic Disks

Numerous observations indicate that galaxies need a continuous gas supply to fuel star formation and explain the star formation history. However, direct observational evidence of gas accretion remains rare. Using the EAGLE cosmological hydrodynamic simulation suite, we study cold gas accretion onto galaxies and the observational signatures of the cold gas kinematics. For EAGLE galaxies at z = 0.27, we find that cold gas accretes onto galaxies anisotropically with typical inflow speeds between 20 and 60 km s−1. Most of these galaxies have comparable mass inflow rates and star formation rates, implying that the cold inflowing gas plausibly accounts for sustaining the star-forming activities of the galaxies. As motivation for future work to compare the cold gas kinematics with measurements from quasar sightline observations, we select an EAGLE galaxy with an extended cold gas disk, and we probe the cold gas using mock quasar sightlines. We demonstrate that by viewing the disk edge on, sightlines at azimuthal angles below 10° and impact parameters out to 60 pkpc can detect cold gas that corotates with the galaxy disk. This example suggests that cold gas disks extending beyond the optical disks possibly explain the sightline observations that detect corotating cold gas near galaxy major axes.
Approximate Riemann solvers for the cosmic ray magnetohydrodynamical equations

We analyze the cosmic-ray magnetohydrodynamic (CR MHD) equations to improve the numerical simulations. We propose to solve them in the fully conservation form, which is equivalent to the conventional CR MHD equations. In the fully conservation form, the CR energy equation is replaced with the CR "number" conservation, where the CR number density is defined as the three fourths power of the CR energy density. The former contains an extra source term, while latter does not. An approximate Riemann solver is derived from the CR MHD equations in the fully conservation form. Based on the analysis, we propose a numerical scheme of which solutions satisfy the Rankine-Hugoniot relation at any shock. We demonstrate that it reproduces the Riemann solution derived by Pfrommer et al. (2006) for a 1D CR hydrodynamic shock tube problem. We compare the solution with those obtained by solving the CR energy equation. The latter solutions deviate from the Riemann solution seriously, when the CR pressure dominates over the gas pressure in the post-shocked gas. The former solutions converge to the Riemann solution and are of the second order accuracy in space and time. Our numerical examples include an expansion of high pressure sphere in an magnetized medium. Fast and slow shocks are sharply resolved in the example. We also discuss possible extension of the CR MHD equations to evaluate the average CR energy.
High-contrast imaging of Sirius A with VLT/SPHERE: looking for giant planets down to one astronomical unit

Sirius has always attracted a lot of scientific interest, especially after the discovery of a companion white dwarf at the end of the 19th century. Very early on, the existence of a potential third bodywas put forward to explain some of the observed properties of the system. We present new coronagraphic observations obtained with VLT/SPHERE (Very Large Telescope/SpectroPolarimetric High-contrast Exoplanet REsearch) that explore, for the very first time, the innermost regions of the system down to 0.2 arcsec(0.5 au) from Sirius A. Our observations cover the near-infrared from 0.95 to 2.3 mu m and they offer the best on-sky contrast ever reached at these angular separations. After detailing the steps of our SPHERE/IRDIFS data analysis, we present a robust method to derive detection limits for multispectral data from high-contrast imagers and spectrographs. In terms of raw performance, we report contrasts of 14.3 mag at 0.2 arcsec, similar to 16.3 mag in the 0.4-1.0 arcsec range and down to 19 mag at 3.7 arcsec. In physical units, our observations are sensitive to giant planets down to 11 M-Jup at 0.5 au, 6-7 M-Jup in the 1-2 au range and similar to 4 M-Jup at 10 au. Despite the exceptional sensitivity of our observations, we do not report the detection of additional companions around Sirius A. Using a Monte Carlo orbital analysis, we show that we can reject, with about 50 per cent probability, the existence of an 8 M-Jup planet orbiting at 1 au.
Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster

Context. Within the central 10 pc of our Galaxy lies a dense cluster of stars. This nuclear star cluster forms a distinct component of the Galaxy, and similar nuclear star clusters are found in most nearby spiral and elliptical galaxies. Studying the structure and kinematics of nuclear star clusters reveals the history of mass accretion and growth of galaxy nuclei and central massive black holes. Aims. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, we can spatially resolve the cluster on sub-parsec scales. This makes the Milky Way nuclear star cluster a reference object for understanding the formation of all nuclear star clusters. Methods. We have used the near-infrared long-slit spectrograph ISAAC (VLT) in a drift-scan to construct an integral-field spectroscopic map of the central 9:5 8 pc of our Galaxy, and six smaller fields out to 19 pc along the Galactic plane. We use this spectroscopic data set to extract stellar kinematics both of individual stars and from the unresolved integrated light spectrum. We present a velocity and dispersion map from the integrated light spectra and model these kinematics using kinemetry and axisymmetric Jeans models. We also measure radial velocities and CO bandhead strengths of 1375 spectra from individual stars. Results. We find kinematic complexity in the nuclear star clusters radial velocity map including a misalignment of the kinematic position angle by 9 counterclockwise relative to the Galactic plane, and indications for a rotating substructure perpendicular to the Galactic plane at a radius of 20 00 or 0.8 pc. We determine the mass of the nuclear star cluster within r = 4:2 pc to (1.4 +0:6 0:7 ) 10 7 M . We also show that our kinematic data results in a significant underestimation of the supermassive black hole (SMBH) mass. Conclusions. The kinematic substructure and position angle misalignment may hint at distinct accretion events. This indicates that the Milky Way nuclear star cluster grew at least partly by the mergers of massive star clusters. Compared to other nuclear star clusters, the Milky Way nuclear star cluster is on the compact side of the re MNSC relation. The underestimation of the SMBH mass might be caused by the kinematic misalignment and a stellar population gradient. But it is also possible that there is a bias in SMBH mass measurements obtained with integrated light, and this might a ect SMBH mass determinations of other galaxies.
A deep, wide-field study of Holmberg II with Suprime-Cam

We present a deep, wide-field optical study of the M81 group dwarf galaxy Holmberg II (HoII) based on Subaru/Suprime-Cam imaging. Individual stars are resolved down to I similar to 25.2, that is, about 1.5? mag below the tip of the red giant branch (RGB). We use resolved star counts in the outskirts of the galaxy to measure the radial surface brightness profile down to mu V similar to 32? mag arcsec-2, from which we determine a projected exponential scalelength of 0.70 +/- 0.01? arcmin (i.e. 0.69 +/- 0.01? kpc). The composite profile, ranging from the cored centre out to R = 7? arcmin, is best fitted by an ElsonFallFreeman profile which gives a half-light radius of 1.41 +/- 0.04? arcmin (i.e. 1.39 +/- 0.04? kpc), and an absolute magnitude MV = -16.3. The low surface brightness stellar component of HoII is regular and symmetric and has an extent much smaller than the vast H? i cloud in which it is embedded. We compare the spatial distribution of the young, intermediate-age and old stellar populations, and find that the old RGB stars are significantly more centrally concentrated than the young stellar populations, contrary to what is observed in most dwarf galaxies of the local Universe. We discuss these properties in the context of the comet-like distribution of H? i gas around HoII, and argue for the presence of a hot intragroup medium in the vicinity of HoII to explain the contrasting morphologies of gas and stars.
Conformal symmetry and accelerating cosmology in teleparallel gravity

We discuss conformal issues of pure and extended teleparallel gravity. In particular, we present formulations of conformal transformation in teleparallel gravity. Furthermore, we propose conformal scalar and gauge field theories in teleparallel gravity and study conformal torsion gravity. We explicitly demonstrate that a power-law acceleration (including the $\Lambda$CDM universe) as well as the de Sitter expansion of the universe can be realized in extended teleparallel gravity with a conformal scalar field, and that pure teleparallel gravity with a conformal scalar field can lead to the $\Lambda$CDM model. It is also shown that there can exist the de Sitter solution in conformal torsion gravity.
Onset of Fast Reconnection in Hall Magnetohydrodynamics Mediated by the Plasmoid Instability

The role of a super-Alfv\'enic plasmoid instability in the onset of fast reconnection is studied by means of the largest Hall magnetohydrodynamics simulations to date, with system sizes up to $10^{4}$ ion skin depths ($d_{i}$). It is demonstrated that the plasmoid instability can facilitate the onset of rapid Hall reconnection, in a regime where the onset would otherwise be inaccessible because the Sweet-Parker width is significantly above $d_{i}$. However, the topology of Hall reconnection is not inevitably a single stable X-point. There exists an intermediate regime where the single X-point topology itself exhibits instability, causing the system to alternate between a single X-point geometry and an extended current sheet with multiple X-points produced by the plasmoid instability. Through a series of simulations with various system sizes relative to $d_{i}$, it is shown that system size affects the accessibility of the intermediate regime. The larger the system size is, the easier it is to realize the intermediate regime. Although our Hall MHD model lacks many important physical effects included in fully kinetic models, the fact that a single X-point geometry is not inevitable raises the interesting possibility for the first time that Hall MHD simulations may have the potential to realize reconnection with geometrical features similar to those seen in fully kinetic simulations, namely, extended current sheets and plasmoid formation.
IS THE REGIME WITH SHOT NOISE SUPPRESSION BY A FACTOR 1/3 ACHIEVABLE IN SEMICONDUCTOR DEVICES WITH MESOSCOPIC DIMENSIONS?

We discuss the possibility of diffusive conduction and thus of suppression of shot noise by a factor 1/3 in mesoscopic semiconductor devices with two-dimensional and one-dimensional potential disorder, for which existing experimental data do not provide a conclusive result. On the basis of our numerical analysis, we conclude that it is quite difficult to achieve diffusive transport over a reasonably wide parameter range, unless the device dimensions are increased up to the macroscopic scale where, however, shot noise disappears because the device length exceeds the Debye length. In addition, in the case of one-dimensional disorder, some mechanism capable of mode-mixing has to be present in order to reach or even approach the diffusive regime.
DETECTION OF THE 158 μm [C ii] TRANSITION AT z = 1.3: EVIDENCE FOR A GALAXY-WIDE STARBURST

We report the detection of 158 μm [C ii] fine-structure line emission from MIPS J142824.0+352619, a hyperluminous (LIR ∼ 1013 L☉) starburst galaxy at z = 1.3. The line is bright, corresponding to a fraction L[C ii]/LFIR ≈ 2 × 10−3 of the far-IR (FIR) continuum. The [C ii], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n ∼ 104.2 cm−3, and that are illuminated by a far-UV radiation field ∼103.2 times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L[C ii]/LFIR ratio is higher than observed in local ultraluminous infrared galaxies or in the few high-redshift QSOs detected in [C ii], but the L[C ii]/LFIR and LCO/LFIR ratios are similar to the values seen in nearby starburst galaxies. This suggests that MIPS J142824.0+352619 is a scaled-up version of a starburst nucleus, with the burst extended over several kiloparsecs.
On the contribution of active galactic nuclei to reionization (Research Note)

Theelectron scattering optical depth constraints on reionization suggest that there may be other sources that contributeto theionization of hydrogen aside from observable star forming galaxies. Often the calculated value of the electron scattering optical depth, τes, falls below the measurements derived from observations of the cosmic microwave background, or an assumption about non-observable sources must be made in order to reach agreement. Here, we calculate the hydrogen ionization fraction as a function of redshift and the electron scattering optical depth from both galaxies and active galactic nuclei (AGN) factoring in the secondary collisional ionizations from the AGN X-ray emission. In this paper we use the most current determination of the evolving hard X-ray luminosity function and extrapolate its evolution beyond z = 6. The AGN spectral energy distributions include both UV and X-ray ionizing photons. To search for the largest possible effect, all AGNs are assumed to have λEdd = 1.0 and to be completely unobscured. The results show that AGNs produce a perturbative effect on the reionization of hydrogen and they remain in agreement with current constraints. Our calculations find the epoch of reionization still ends at z ≈ 6 and only increases the electron scattering optical depth by ∼2.3% under ideal conditions. This can only be moderately increased by assuming a constant black hole mass of MBH = 10 5 M� . As a result, we conclude that there is a need for other sources beyond observable galaxies and AGNs that contribute to the reionization of hydrogen at z > 6.
Pitch-angle Diffusion and Bohm-type Approximations in Diffusive Shock Acceleration

The problem of accelerating cosmic rays is one of fundamental importance, particularly given the uncertainty in the conditions inside the acceleration sites. Here we examine diffusive shock acceleration in arbitrary turbulent magnetic fields, constructing a new model that is capable of bridging the gap between the very weak (δB/B0 ≪ 1) and the strong turbulence regimes. To describe the diffusion we provide a quantitative analytical description of the “Bohm exponent” in each regime. We show that our results converge to the well known quasi-linear theory in the weak turbulence regime. In the strong regime, we quantify the limitations of the Bohm-type models. Furthermore, our results account for the anomalous diffusive behavior which has been noted previously. Finally, we discuss the implications of our model in the study of possible acceleration sites in different astronomical objects.