The Origin of Radio Emission in Black Hole X-ray Binaries

We studied the relation of accretion-jet power and disk luminosity, especially the jet efficiencies and disk radiative efficiencies for different accretion disks as well as black hole (BH) spin, in order to explore the origin of radio emission in black hole X-ray binaries (BHXBs). We found that jet efficiency increases more rapidly (efficient) than the nearly constant disk radiative efficiency for thin disk component in high accretion regime, which could account for the steep track (μ>1) in the observed radio and X-ray luminosity relations (LR∝LXμ), but the thin disk component may not be able to explain the standard track (μ≈0.6) in the BHXBs. For hot accretion flows (HAF), the resulting jet efficiency changes along with the large range of accretions from quiescent state to nearly Eddington state, which could account for the standard track in the BHXBs. The BH spin-jet is discussed for the magnetic arrested disk (MAD) state; in this state, the spin-jet power might contribute to a linear correlation between jet power and mass accretion rate for a given source. More accurate observations are required to test the results.

The far reaches of the β Pictoris debris disk

The nearby young star β Pictoris hosts a rich and complex planetary system, with at least two giant planets and a nearly edge-on debris disk that contains several dynamical subpopulations of planetesimals. While the inner ranges of the debris disk have been studied extensively, less information is known about the outer, fainter parts of the disk. Here we present an analysis of archival FORS V -band imaging data from 2003–2004, which have previously not been explored scientifically because the halo substructure of the bright stellar point spread function is complex. Through a high-contrast scheme based on angular differential imaging, with a forward-modelling approach to mitigate self-subtraction, we produced the deepest imaging yet for the outer range of the β Pic disk, and extracted its morphological characteristics. A brightness asymmetry between the two arms of the edge-on disk, which was previously noted in the inner disk, is even more pronounced at larger angular separations, reaching a factor ~10 around 1000 AU. Approaching 2000 AU, the brighter arm is visible at a surface brightness of 27–28 mag arcsec−2. Much like for the brightness asymmetry, a tilt angle asymmetry exists between the two arms that becomes increasingly extreme at large separations. The outer tilt angle of 7.2 deg can only be explained if the outer disk is farther from an edge-on inclination than the inner disk, or if its dust has a stronger scattering anisotropy, or (most likely) both. The strong asymmetries imply the presence of a highly eccentric kinematic disk component, which may have been caused by a disruptive event thought to have taken place at a closer-in location in the disk.

The SAMI Galaxy Survey: decomposed stellar kinematics of galaxy bulges and disks

ABSTRACT We investigate the stellar kinematics of the bulge and disk components in 826 galaxies with a wide range of morphology from the Sydney-AAO Multi-object Integral-field spectroscopy Galaxy Survey. The spatially resolved rotation velocity (V) and velocity dispersion (σ) of bulge and disk components have been simultaneously estimated using the penalized pixel fitting (ppxf) method with photometrically defined weights for the two components. We introduce a new subroutine of ppxf for dealing with degeneracy in the solutions. We show that the V and σ distributions in each galaxy can be reconstructed using the kinematics and weights of the bulge and disk components. The combination of two distinct components provides a consistent description of the major kinematic features of galaxies over a wide range of morphological types. We present Tully–Fisher and Faber–Jackson relations showing that the galaxy stellar mass scales with both V and σ for both components of all galaxy types. We find a tight Faber–Jackson relation even for the disk component. We show that the bulge and disk components are kinematically distinct: (1) the two components show scaling relations with similar slopes, but different intercepts; (2) the spin parameter λR indicates bulges are pressure-dominated systems and disks are supported by rotation; and (3) the bulge and disk components have, respectively, low and high values in intrinsic ellipticity. Our findings suggest that the relative contributions of the two components explain, at least to first order, the complex kinematic behaviour of galaxies.

First detection of the 448 GHz ortho-H2O line at high redshift: probing the structure of a starburst nucleus at z = 3.63

Submillimeter rotational lines of H2O are a powerful probe in warm gas regions of the interstellar medium (ISM), tracing scales and structures ranging from kiloparsec disks to the most compact and dust-obscured regions of galactic nuclei. The ortho-H2O(423 − 330 line at 448 GHz, which has recently been detected in a local luminous infrared galaxy, offers a unique constraint on the excitation conditions and ISM properties in deeply buried galaxy nuclei because the line requires high far-infrared optical depths to be excited. In this letter, we report the first high-redshift detection of the 448 GHz H2O(423–330) line using ALMA in a strongly lensed submillimeter galaxy (SMG) at z = 3.63. After correcting for magnification, the luminosity of the 448 GHz H2O line is ∼106 L⊙. In combination with three other previously detected H2O lines, we build a model that resolves the dusty ISM structure of the SMG, and find that it is composed of a ∼1 kpc optically thin (optical depth at 100 μm τ100 ∼ 0.3) disk component with a dust temperature Tdust ≈ 50 K that emits a total infrared power of 5 × 1012 L⊙ with a surface density ΣIR = 4 × 1011 L⊙ kpc−2, and a very compact (0.1 kpc) heavily dust-obscured (τ100 ≳ 1) nuclear core with very warm dust (100 K) and ΣIR = 8 × 1012 L⊙ kpc−2. The H2O abundance in the core component, XH2O ∼ (0.3–5) × 10−5, is at least one order of magnitude higher than in the disk component. The optically thick core has the characteristic properties of an Eddington-limited starburst, providing evidence that radiation pressure on dust is capable of supporting the ISM in buried nuclei at high redshifts. The multicomponent ISM structure revealed by our models illustrates that dust and molecules such as H2O are present in regions that are characterized by highly differing conditions and scales, extending from the nucleus to more extended regions of SMGs.

Globular clusters in the inner Galaxy classified from dynamical orbital criteria

Globular clusters (GCs) are the most ancient stellar systems in the Milky Way. Therefore, they play a key role in the understanding of the early chemical and dynamical evolution of our Galaxy. Around 40% of them are placed within ∼4 kpc from the Galactic center. In that region, all Galactic components overlap, making their disentanglement a challenging task. With Gaia DR2, we have accurate absolute proper motions for the entire sample of known GCs that have been associated with the bulge/bar region. Combining them with distances, from RR Lyrae when available, as well as radial velocities from spectroscopy, we can perform an orbital analysis of the sample, employing a steady Galactic potential with a bar. We applied a clustering algorithm to the orbital parameters apogalactic distance and the maximum vertical excursion from the plane, in order to identify the clusters that have high probability to belong to the bulge/bar, thick disk, inner halo, or outer halo component. We found that $\sim 30\%$ of the clusters classified as bulge GCs based on their location are just passing by the inner Galaxy, they appear to belong to the inner halo or thick disk component, instead. Most of GCs that are confirmed to be bulge GCs are not following the bar structure and are older than the epoch of the bar formation.

Spotting a counter-rotating galaxy

The presence of counter-rotating (CR) components in galaxies is not that rare but their origin is still unclear. Important clues to the formation and evolution of CR galaxies are provided by galaxy kinematics, such as the mass distribution and the shape of the gravitational potential. In order to better understand the origin and incidence of CR galaxies, we aim at modeling CR stellar disks, as they would be observed with Integral Field Units (IFU) instruments, and measuring the kinematics of these peculiar astrophysical objects to reveal the CR signatures. In the bi-dimensional maps of analysed models, the double sigma signature is the best diagnostic to spot the presence of a CR disk component.

A New Image Restoration Method for MUSER

Solar radio images in decimeter wave range consist of many complicated components including a disk component, some bright and weak compact sources, and many diffuse features. Complicated structures combining these various components maybe cause restoration failure when using conventional algorithms. Furthermore, the images at different frequencies band are pretty different. Therefore, restoration method for solar radio image is different from other radio sources. Some image restoration methods were applied and obtained good results on Nancay radioheliograph images and Nobeyama radioheliograph images, and some new methods were introduced into processing these complicated solar radio images in recent years. For a new radioheliograph with ultrawide frequency band, new image restoration method which can maximize function of telescope is demanded. Different images could be obtained from the same visibilities data by using different weighting functions in imaging processing. In this paper, a new restoration method for solar radio image was proposed. Two images with different weighting functions from the same data are combined in this method. This restoration method has applied to data processing of Mingantu spectral radioheliograph.

Stellar populations of the central region of M 31

Aims. We continue the analysis of the data set of our spectroscopic observation campaign of M 31, whose ultimate goal is to provide an understanding of the three-dimensional structure of the bulge, its formation history, and composition in terms of a classical bulge, boxy-peanut bulge, and bar contributions. Methods. We derive simple stellar population (SSP) properties, such as age metallicity and α-element overabundance, from the measurement of Lick/IDS absorption line indices. We describe their two-dimensional maps taking into account the dust distribution in M 31. Results. We found 80% of the values of our age measurements are larger than 10 Gyr. The central 100 arcsec of M 31 are dominated by the stars of the classical bulge of M 31. These stars are old (11−13 Gyr), metal-rich (as high as [Z/H] ≈ 0.35 dex) at the center with a negative gradient outward and enhanced in α-elements ([α/Fe]≈ 0.28±0.01 dex). The bar stands out in the metallicity map, where an almost solar value of [Z/H] (≈0.02 ± 0.01 dex) with no gradient is observed along the bar position angle (55.7 deg) out to 600 arcsec from the center. In contrast, no signature of the bar is seen in the age and [α/Fe] maps, which are approximately axisymmetric, delivering a mean age and overabundance for the bar and boxy-peanut bulge of 10–13 Gyr and 0.25–0.27 dex, respectively. The boxy-peanut bulge has almost solar metallicity (−0.04 ± 0.01 dex). The mass-to-light ratio of the three components is approximately constant at M/LV ≈ 4.4−4.7 M⊙/L⊙. The disk component at larger distances is made of a mixture of stars, as young as 3–4 Gyr, with solar metallicity and smaller M/LV (≈3 ± 0.1 M⊙/L⊙). Conclusions. We propose a two-phase formation scenario for the inner region of M 31, where most of the stars of the classical bulge come into place together with a proto-disk, where a bar develops and quickly transforms it into a boxy-peanut bulge. Star formation continues in the bulge region, producing stars younger than 10 Gyr, in particular along the bar, thereby enhancing its metallicity. The disk component appears to build up on longer timescales.