This study examines the impact of audit committee (AC) characteristics on audit quality in the Saudi listed firms. In addition, this study is also evaluating the Saudi CG Code amended in 2017. The ...data for the study is obtained from secondary (annual reports) data. The sample firms are 210 firms listed on the Saudi Stock Exchange (Tadawul) over the period of 2017-2019. The audit firm type is used as a proxy for quality in this study. Multiple regression analysis is used to assess the relationship between AC characteristics and audit quality. The regression models show that firms with AC educational background in accounting and finance, and larger firms with higher state and institutional ownership are more likely to engage a big four audit firm, in so doing signalling greater audit quality. The results support agency and institutional theories concerning audit quality. In contrast, firms with more experts on the AC and higher leverage are more likely to select non-big four auditing firms which require lower audit fees. However, the size, number of meetings, and degree of independence of the AC do not significantly affect the level of audit quality. In addition, a combined AC effectiveness score is found to have a negative though insignificant impact on audit quality, contradicting governance regulation and theory expectations that effective ACs should improve audit quality. The results of this study present some key implications for CG regulators and other stakeholders. CG regulators should understand that the simple presence of an AC that meets baseline CG regulatory requirements does not automatically ensure its efficacy or improve auditing process quality. Therefore, boards and shareholders must continue to monitor and review AC decisions, particularly where they relate to auditor engagement, even where committees are, prima facie, deemed effective. The study contributes to the existing body of literature on the role of the audit committee in improving audit quality by addressing the paucity of evidence for emerging economies, and the case of Saudi Arabia in particular. The findings should prove useful for regulators and policy makers, academic researchers, accountants, financial experts, and audit practitioners in the Middle East and wider Arab region, particularly for those countries currently reviewing and setting guidelines for effective audit committees. Moreover, the findings should emphasise the importance of the concept of audit quality and its drivers in a Saudi Arabian corporate setting.
Context.
The Sagittarius (Sgr) stream is one of the best tools that we currently have to estimate the mass and shape of our Galaxy. However, assigning membership and obtaining the phase-space ...distribution of the stars that form the tails of the stream is quite challenging.
Aims.
Our goal is to produce a catalogue of the RR Lyrae stars of Sgr and obtain an empiric measurement of the trends along the stream in sky position, distance, and tangential velocity.
Methods.
We generated two initial samples from the
Gaia
DR2 RR Lyrae catalogue: one selecting only the stars within ±20° of the orbital plane of Sagittarius (Strip), and the other resulting from application of the Pole Count Map (nGC3) algorithm. We then used the model-independent, deterministic method developed in this work to remove most of the contamination by detecting and isolating the stream in distance and proper motions.
Results.
The output is two empiric catalogues: the Strip sample (higher-completeness, lower-purity) which contains 11 677 stars, and the nGC3 sample (higher-purity, lower-completeness) with 6608 stars. We characterise the changes along the stream in all the available dimensions, namely the five astrometric dimensions plus the metallicity, covering more than 2
π
rad in the sky, and obtain new estimates for the apocentres and the mean Fe/H of the RR Lyrae population. Also, we show the first map of the two components of the tangential velocity thanks to the combination of distances and proper motions. Finally, we detect the bifurcation in the leading arm and report no significant difference between the two branches in terms of metallicity, kinematics, or distance.
Conclusions.
We provide the largest sample of RR Lyrae candidates of Sgr, which can be used as input for a spectroscopic follow-up or as a reference for the new generation of models of the stream through the interpolators in distance and velocity that we constructed.
Human activity recognition (HAR) applications have received much attention due to their necessary implementations in various domains, including Industry 5.0 applications such as smart homes, ...e-health, and various Internet of Things applications. Deep learning (DL) techniques have shown impressive performance in different classification tasks, including HAR. Accordingly, in this article, we develop a comprehensive HAR system based on a novel DL architecture called Multi-ResAtt (multilevel residual network with attention). This model incorporates initial blocks and residual modules aligned in parallel. Multi-ResAtt learns data representations on the inertial measurement units level. Multi-ResAtt integrates a recurrent neural network with attention to extract time-series features and perform activity recognition. We consider complex human activities collected from wearable sensors to evaluate the Multi-ResAtt using three public datasets, Opportunity; UniMiB-SHAR; and PAMAP2. Additionally, we compared the proposed Multi-ResAtt to several DL models and existing HAR systems, and it achieved significant performance.
We present the high-resolution spectroscopic study of five −3.9 ≤ Fe/H ≤ −2.5 stars in the Local Group dwarf spheroidal, Sculptor, thereby doubling the number of stars with comparable observations in ...this metallicity range. We carry out a detailed analysis of the chemical abundances of α, iron peak, and light and heavy elements, and draw comparisons with the Milky Way halo and the ultra-faint dwarf stellar populations. We show that the bulk of the Sculptor metal-poor stars follow the same trends in abundance ratios versus metallicity as the Milky Way stars. This suggests similar early conditions of star formation and a high degree of homogeneity of the interstellar medium. We find an outlier to this main regime, which seems to miss the products of the most massive of the Type II supernovae. In addition to its help in refining galaxy formation models, this star provides clues to the production of cobalt and zinc. Two of our sample stars have low odd-to-even barium isotope abundance ratios, suggestive of a fair proportion of s-process. We discuss the implication for the nucleosynthetic origin of the neutron capture elements.
Dark influences Starkenburg, T K; Helmi, A; Sales, L V
Astronomy and astrophysics (Berlin),
11/2016, Letnik:
595
Journal Article
Recenzirano
Odprti dostop
Context. In the current concordance cosmology small halos are expected to be completely dark and can significantly perturb low-mass galaxies during minor merger interactions. These interactions may ...well contribute to the diversity of the dwarf galaxy population. Dwarf galaxies in the field are often observed to have peculiarities in their structure, morphology, and kinematics, as well as strong bursts of star formation without apparent cause. Aims. We aim to characterise the signatures of minor mergers of dwarf galaxies with dark satellites to aid their observational identification. Methods. We explored and quantified a variety of structural, morphological, and kinematic indicators of merging dwarf galaxies and their remnants using a suite of hydrodynamical simulations. Results. The most sensitive indicators of mergers with dark satellites are large asymmetries in the gaseous and stellar distributions, enhanced central surface brightness and starbursts, and velocity offsets and misalignments between the gas and stellar components. In general, merging systems span a wide range of values of the most commonly used indicators, while isolated objects tend to have more confined values. Interestingly, we find in our simulations that a significantly off-centred burst of star formation can pinpoint the location of the dark satellite. Observational systems with such characteristics are perhaps the most promising for unveiling the presence of the hitherto missing satellites.
We have developed spherically symmetric dynamical models of dwarf spheroidal (dSph) galaxies using Schwarzschild's orbit superposition method. This type of modelling yields constraints both on the ...total mass distribution (e.g. enclosed mass and scale radius) and on the orbital structure of the system (e.g. velocity anisotropy). This method is thus less prone to biases introduced by assumptions in comparison to the more commonly used Jeans modelling, and it allows us to put reliable constraints on their dark matter content. Here we present our results for the Sculptor dSph galaxy, after testing our methods on mock data sets. We fit both the second and fourth velocity moment profiles to break the mass-anisotropy degeneracy. For an Navarro, Frenk & White (NFW) dark matter halo profile, we find that the mass of Sculptor within 1 kpc is M
1 kpc = (1.03 ± 0.07) × 108 M, and that its velocity anisotropy profile is tangentially biased and nearly constant for radii beyond ∼100 pc. The preferred concentration (c ∼ 15) is low for its dark matter mass but consistent within the scatter found in N-body cosmological simulations. When we let the value of the central logarithmic slope α vary, we find that the best-fitting model has α = 0, although an NFW cusp or shallower is consistent at the 1σ confidence level. On the other hand, very cuspy density profiles with logarithmic central slopes α < −1.5 are strongly disfavoured for Sculptor.
We present our analysis of the FLAMES dataset targeting the central 25′ region of the Sextans dwarf spheroidal galaxy (dSph). This dataset is the third major part of the high-resolution spectroscopic ...section of the ESO large program 171.B-0588(A) obtained by the Dwarf galaxy Abundances and Radial-velocities Team. Our sample is composed of red giant branch stars down to
V
∼ 20.5 mag, the level of the horizontal branch in Sextans, and allows users to address questions related to both stellar nucleosynthesis and galaxy evolution. We provide metallicities for 81 stars, which cover the wide Fe/H = −3.2 to −1.5 dex range. The abundances of ten other elements are derived: Mg, Ca, Ti, Sc, Cr, Mn, Co, Ni, Ba, and Eu. Despite its small mass, Sextans is a chemically evolved system, showing evidence of a contribution from core-collapse and Type Ia supernovae as well as low-metallicity asymptotic giant branch stars (AGBs). This new FLAMES sample offers a sufficiently large number of stars with chemical abundances derived with high accuracy to firmly establish the existence of a plateau in
α
/Fe at ∼0.4 dex followed by a decrease above Fe/H ∼ −2 dex. These features reveal a close similarity with the Fornax and Sculptor dSphs despite their very different masses and star formation histories, suggesting that these three galaxies had very similar star formation efficiencies in their early formation phases, probably driven by the early accretion of smaller galactic fragments, until the UV-background heating impacted them in different ways. The parallel between the Sculptor and Sextans dSph is also striking when considering Ba and Eu. The same chemical trends can be seen in the metallicity region common to both galaxies, implying similar fractions of SNeIa and low-metallicity AGBs. Finally, as to the iron-peak elements, the decline of Co/Fe and Ni/Fe above Fe/H ∼ −2 implies that the production yields of Ni and Co in SNeIa are lower than that of Fe. The decrease in Ni/Fe favours models of SNeIa based on the explosion of double-degenerate sub-Chandrasekhar mass white dwarfs.
We use data from the Radial Velocity Experiment (RAVE) and the Tycho-Gaia astrometric solution (TGAS) catalogue to compute the velocity fields yielded by the radial (V-R), azimuthal (V-phi), and ...vertical (V-z) components of associated Galactocentric velocity. We search in particular for variation in all three velocity components with distance above and below the disc midplane, as well as how each component of V-z (line-of-sight and tangential velocity projections) modifies the obtained vertical structure. To study the dependence of velocity on proper motion and distance, we use two main samples: a RAVE sample including proper motions from the Tycho-2, PPMXL, and UCAC4 catalogues, and a RAVE-TGAS sample with inferred distances and proper motions from the TGAS and UCAC5 catalogues. In both samples, we identify asymmetries in V-R and V-z. Below the plane, we find the largest radial gradient to be partial derivative V-R/partial derivative R = -7.01 +/- 0.61 km s(-1) kpc(-1), in agreement with recent studies. Above the plane, we find a similar gradient with partial derivative V-R/partial derivative R = -9.42 +/- 1.77 km s(-1) kpc(-1). By comparing our results with previous studies, we find that the structure in V-z is strongly dependent on the adopted proper motions. Using the Galaxia Milky Way model, we demonstrate that distance uncertainties can create artificial wave-like patterns. In contrast to previous suggestions of a breathing mode seen in RAVE data, our results support a combination of bending and breathing modes, likely generated by a combination of external or internal and external mechanisms.
We use the Aquarius simulation series to study the imprint of assembly history on the structure of Galaxy-mass cold dark matter haloes. Our results confirm earlier work regarding the influence of ...mergers on the mass density profile and the inside-out growth of haloes. The inner regions that contain the visible galaxies are stable since early times and are significantly affected only by major mergers. Particles accreted diffusely or in minor mergers are found predominantly in the outskirts of haloes. Our analysis reveals trends that run counter to current perceptions of hierarchical halo assembly. For example, major mergers (i.e. those with progenitor mass ratios greater than 1:10) contribute little to the total mass growth of a halo, on average less than 20 per cent for our six Aquarius haloes. The bulk is contributed roughly equally by minor mergers and by 'diffuse' material which is not resolved into individual objects. This is consistent with modelling based on excursion-set theory which suggests that about half of this diffuse material should not be part of a halo of any scale. The simulations themselves suggest that a significant fraction is not truly diffuse, since it was ejected from earlier haloes by mergers prior to their joining the main system. The Aquarius simulations resolve haloes to much lower mass scales than are expected to retain gas or form stars. Thus, the fraction of diffuse dark matter accreted by haloes represents a lower limit to the fraction of diffuse baryons accreted by galaxies. Our results thus confirm that most of the baryons from which visible galaxies form are accreted diffusely, rather than through mergers, and they suggest that only relatively rare major mergers will affect galaxy structure at later times.
Context. In the context of the current Λ cold dark matter cosmological model small dark matter halos are abundant and satellites of dwarf galaxies are expected to be predominantly dark. Since low ...mass galaxies have smaller baryon fractions, interactions with these satellites may leave particularly dramatic imprints. Aims. We uncover the influence of the most massive of these dark satellites on disky dwarf galaxies and the possible dynamical and morphological transformations that result from these interactions. Methods. We use a suite of carefully set up, controlled simulations of isolated dwarf galaxies. The primary dwarf galaxies have solely a stellar disk in the dark matter halo and the secondaries are completely devoid of baryons. We vary the disk mass, halo concentration, initial disk thickness, and inclination of the satellite orbit. Results. The disky dwarf galaxies are heated and disrupted by the minor merger event, more extremely for higher satellite-to-disk-mass ratios, and the morphology and kinematics are significantly altered. Moreover, for less concentrated halos the minor merger can completely destroy the disk leaving a low-luminosity spheroidal-like galaxy instead. Conclusions. We conclude that dwarf galaxies are very susceptible to being disturbed by dark galaxies and that even a minor merger event can significantly disrupt and alter the structure and kinematics of a dwarf galaxy. This process may be seen as a new channel for the formation of dwarf spheroidal galaxies.
PDF
