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KOALA, a new ATLAS9 database
No full textWe present the KOALA database, a new set of local thermodynamic equilibrium line-blanketed model atmospheres calculated with the code ATLAS9, together with the corresponding opacity distribution functions and emergent fluxes. The latter were also used to calculate G-band bolometric corrections and theoretical magnitudes and colours for several photometric systems, i.e. UBVRI, 2MASS, Hypparcos-Tycho, SDSS, Galex, Euclid, and Gaia DR3. With respect to previous grids of ATLAS9 model atmospheres, we adopted the solar mixture by Caffau/Lodders, and we extend the sampling in metallicity (from −5.0 to −2.5 dex, with a step of 0.5 dex, and from −2.5 dex to +0.5 dex, with a step of 0.25 dex) and in [α/Fe] (from −0.4 to +0.4 dex, with a step of 0.2 dex). We also provide a finer sampling in Teff for Teff lower than 7000 K. This finer grid allows for more accurate interpolation of colours, and in many cases it makes computing a new model atmosphere unnecessary since the atmosphere of the grid can be used directly. We computed a total of 51 663 model atmospheres and emergent fluxes. Finally, we discuss the impact of [M/H] and [α/Fe] on the thermal and pressure structures of the model atmospheres and on theoretical colours
The hard ultraluminous state of NGC 5055 ULX X-1
No full textWe present the results of the first broadband X-ray analysis of the ultraluminous X-ray source NGC 5055 ULX X-1, combining simultaneous data from XMM–Newton and NuSTAR missions, with a combined exposure time of ∼100 ks across the 0.3–20 keV energy range. The source exhibits a stable flux across the entire exposure with no detectable pulsations by any instrument on their X-ray light curves, placing pulsed-fraction upper limits of 10% and 32% for XMM–Newton and NuSTAR, respectively. The X-ray spectrum is dominated by two thermal components consistent with the emission from an accretion disk, and shows a weak high-energy tail above 10 keV, with no statistical requirement for an additional nonthermal component. The unabsorbed 0.3 − 20 keV luminosity is ∼2 × 1040 erg s−1, evidencing the ULX nature of the source. The parameters obtained from spectral modeling are consistent with the hard ultraluminous state. Despite the fact that a neutron-star accretor cannot be ruled out by the available data, under the assumption that the compact object in NGC 5055 ULX X-1 is a black hole accreting through a geometrically thick, radiation-pressure-supported disk that drives an optically thick wind, we constrained its putative mass to 11 − 26 M⊙
Quantification of abundance uncertainties in chemical models of exoplanet atmospheres
No full textChemical models are routinely used to predict the atmospheric composition of exoplanets and compare it with the composition retrieved from observations, but little is known about the reliability of the calculated composition. We carried out a sensitivity analysis to quantify the uncertainties in the abundances calculated by a state-of-the-art chemical atmosphere model of the widely observed planets WASP-33b, HD 209458b, HD 189733b, WASP-39b, GJ 436b, and GJ 1214b. We found that the abundance uncertainties in the observable atmosphere are relatively small, below one order of magnitude and in many cases below a factor of two, where vertical mixing is a comparable or even larger source of uncertainty than (photo)chemical kinetics. In general, planets with a composition close to chemical equilibrium have smaller abundance uncertainties than planets whose composition is dominated by photochemistry. Some molecules, such as H2O, CO, CO2, and SiO, show low abundance uncertainties, while others such as HCN, SO2, PH3, and TiO have more uncertain abundances. We identified several critical albeit poorly constrained processes involving S-, P-, Si-, and Ti-bearing species whose better characterization should lead to a global improvement in the accuracy of models. Some of these key processes are the three-body association reactions S + H2, Si + O, NH + N, and N2H2 + H; the chemical reactions S + OH → SO + H, NS + NH2 → H2S + N2, P + PH → P2 + H, and N + NH3 → N2H + H2; and the photodissociation of molecules such as P2, PH2, SiS, CH, and TiO
TESS phase curve of ultra-hot Jupiter WASP-189 b
No full textContext. The thermal structures of highly irradiated ultra-hot Jupiters can deviate substantially from those of cooler hot Jupiters. For planets orbiting host stars that are rapidly rotating (and, thus, oblate), photometric light curves provide a unique opportunity to measure the spin-orbit angle. Moreover, in systems with significant spin-orbit misalignment, the stellar oblateness can induce an observable orbital precession.
Aims. We wish to study the atmosphere and orbital architecture of an ultra-hot Jupiter WASP-189 b, orbiting a hot A-type star.
Methods. We used the photometric phase curves and gravity-darkened transits of WASP-189 b observed with the Transiting Exoplanet Survey Satellite (TESS). We complemented these data with archival observations from CHaracterising ExOPlanet Satellite (CHEOPS).
Results. We detected a phase-curve signal with significant occultation depth of 203.4−16.3+16.2 ppm, while the nightside flux, −71.8−36.0+36.4 ppm, is consistent with zero at 2σ. We inverted the phase-curve signal to construct the temperature map of the planet. The map was subsequently used to estimate the Bond albedo and heat redistribution efficiency, whose expected median ranges were found to be 0.19–0.35 and 0.09–0.41, respectively. Finally, we analysed gravity-darkened transits to find that the planet is in polar orbit with the spin-orbit angle of 89.46−1.08+1.08 deg. We found no hint of any orbital precession when comparing our results with the literature.
Conclusions. Our observations, together with atmospheric modelling, suggest that the dayside emission of WASP-189b in TESS and CHEOPS bandpasses is dominated by thermal emission from an atmosphere with extremely inefficient heat transport and a negligible contribution from reflected light
Evolution of the kinematic properties of rotating, multiple-population globular clusters
No full textGlobular clusters host multiple stellar populations differing in their chemical and dynamical properties. A number of models for the formation of multiple populations predict that the subsystem of second-generation (SG) stars (those with anomalous chemical abundances) is characterised by a more centrally concentrated spatial distribution and a more rapid rotation than the system of firstgeneration (FG) stars (those with chemical properties similar to field stars). In this paper, we present the results of a suite of N-body simulations aimed at exploring the long-term dynamical evolution of rotating, multiple-population globular clusters. We studied the evolution of systems starting with four different orientations of the cluster’s total internal angular momentum vector relative to the orbital angular momentum. This allows us not only to explore the internal evolution driven by two-body relaxation, but also the effects of the cluster’s interaction with the galactic tidal field and how this interaction affects the cluster’s internal rotation over time. We focused our attention on the kinematic differences between the two generations, and we quantify these differences by exploring the FG and SG stars’ rotational velocity and angular momenta. We find that kinematic differences between the generations persist for a majority of the simulations’ lifetimes, although the strength of these differences rapidly decreases after a few relaxation times. The differences can be seen most clearly in the lowest mass stars in the models. We find that the clusters’ internal angular momentum gradually aligns with the orbital angular momentum over time, although there is little difference in this alignment between the FG and SG systems. We also find that stars in the cluster’s outer regions align with the orbital angular momentum vector more rapidly than those in the inner regions leading to a variation of the orientation of the internal angular momentum with the clustercentric distance. The alignment between internal angular momentum and orbital angular momentum occurs more rapidly for low-mass stars. We also studied the evolution of the anisotropy in the velocity distribution and, in agreement with previous results, find the SG to be characterised by a stronger radial anisotropy than the FG. Overall, our results show that the kinematic properties of multiple populations provide key information related to their formation and dynamical evolution
Glycolaldehyde and ethanol toward the L1157 outflow: Resolved images and constraints on glycolaldehyde formation
No full textContext. Interstellar complex organic molecules, also known as iCOMs, are species of special interest in astrochemistry because of their potential role in the emergence of life. The discovery of iCOMs in the interstellar medium has sparked a decades-long debate about how they are formed. In principle, two main routes are possible: on the surfaces of dust grains and in the gas phase. A powerful way to discriminate between and constrain the two routes is to observe iCOMs along protostellar outflow-shocked regions, provided their ages are well constrained. In this way, the chemical evolution over time can be probed.
Aims. We focused on glycolaldehyde (CH2OHCHO) and ethanol (C2H5OH), and their possible daughter-mother relationship, as suggested by previous studies. More precisely, our objective was to verify whether the gas-phase reactions derived in these studies dominate the formation of glycolaldehyde, so whether this gas-phase formation pathway can account for the abundance of glycolaldehyde observed in star-forming regions. We targeted the well-known southern outflow of L1157, which hosts three shocked regions, B0, B1 and B2, of increasing ages: approximately 900, 1500 and 2300 years, respectively.
Methods. We obtained high-resolution (∼4″) IRAM NOEMA maps of three glycolaldehyde lines and one ethanol line toward the entire southern outflow lobe of L1157 and used them to derive the abundances of the two species in B0, B1 and B2, as well as their abundance ratio. We then used a pseudo time-dependent astrochemical code to model the post-shock gas-phase chemistry of the two molecules under study, in which glycolaldehyde is formed via gas-phase reactions starting from ethanol, via the so-called ethanol-tree scheme, or on the grain surfaces. On the contrary, ethanol is assumed to be form on grain surfaces and to be released into the gas phase by the passage of the shocks. Once in the gas, C2H5OH is gradually consumed to form, among other iCOMs, glycolaldehyde. Ethanol is mainly destroyed through reactions with the OH radical, which in turn is primarily formed by injected (previously frozen) water (H2O).
Results. We present the first spatially resolved maps of ethanol and glycolaldehyde toward the L1157 southern outflow and, more generally, toward solar-like star-forming regions. From these maps, we computed their column densities in B0, B1 and B2. Assuming an excitation temperature of 30 K for both species, we find column densities ranging between 1 and 3 ×1013 cm−2 for glycolaldehyde and between 4 and 6 ×1013 for ethanol. Their relative abundance ratio [CH2OHCHO] / [C2H5OH], equal to 0.25-0.4, increases between B1 and B2. The measured abundance ratios in B1 and B2 are relatively well reproduced by the astrochemical model. However, our model cannot simultaneously reproduce the observations toward B0, and toward B1 and B2, whether we assume that glycolaldehyde is primarily formed in the gas phase or on the grain-surfaces. This likely indicates that one of the assumptions in our model is incorrect. Possible candidates include the excitation temperature and grain mantle composition, assumed to be the same in B0, B1 and B2; the age of B0; and the gas temperature, assumed to be constant after the shock passage. Nonetheless, our modeling rules out the possibility that all the observed gaseous glycolaldehyde is a grain-surface product.
Conclusions. The study of resolved iCOM emission in the direction of protostellar molecular outflows proves to be an efficient way to constrain their formation routes. In the future, it will be important to carry out similar studies in regions other than L1157 outflow. In addition, improved modeling of shock chemistry should be developed, in which physical properties vary with time along with chemistry
ZTF SN Ia DR2 follow-up: Exploring the origin of the Type Ia supernova host galaxy step through Si II velocities
No full textThe relation between Type Ia supernovae (SNe Ia) and the stellar masses of their host galaxy is well documented. In particular, Hubble residuals display a distinct luminosity shift based on host mass. This is known as the mass step. This effect is widely used as an additional correction factor in the standardisation of SN Ia luminosities. We investigate the Hubble residuals and the mass step of normal SNe Ia in the context of Si I
Magnetic fields in the intracluster medium with TNG-Cluster: Properties, morphology, and tangential anisotropy
No full textWe characterized the magnetic field properties of 352 massive galaxy clusters from the TNG-Cluster magnetohydrodynamical (MHD) cosmological simulation with a focus on central magnetic field morphology in cool-core (CC) versus non-cool-core (NCC) clusters. We present the central values and radial profiles of magnetic field strength and plasma parameter as a function of mass, cooling status, and redshift. Compared to low-redshift observations, TNG-Cluster produces reasonable magnetic field amplitudes in the central regions of clusters, spanning a range of 1 − 200 μG. In this paper, we discuss the main finding of this work, namely, that z = 0 CC clusters have preferentially tangential magnetic fields at a characteristic scale of ∼0.1r500c. These strongly tangential field orientations are specific to CCs. In contrast, across the full cluster population, magnetic fields show isotropic configurations at all radii and redshifts. As individual halos grow, the evolution of their magnetic field topologies is diverse: tangential features can be short-lived, persist over large cosmological time-scales, or periodically appear, vanish, and reappear towards z = 0. We discuss the underlying physics and possible physical scenarios to explain the origin of these structures. We argue that both short-term active galactic nucleus (AGN) feedback-driven outflows and merger-driven sloshing motions, cannot explain the population-wide tangential bias in magnetic field orientation. Instead, we propose that the trapping of internal gravity waves is responsible for the tangentially biased magnetic field topologies that we find in CC TNG-Cluster halos, due to the strong entropy gradient in these clusters
On the dusty proximate damped Lyman-
No full textQuasar absorption systems not only affect the way quasars are selected, but also serve as key probes of galaxies, providing insight into their chemical evolution and interstellar medium (ISM). Recently, a method based on Gaia astrometric measurements has aided the selection of quasars reddened by dust hitherto overlooked. We conducted a spectroscopic study using VLT/X-Shooter on one such dust-reddened quasar, Q 2310–3358. This quasar, at z = 2.3909 ± 0.0022, is associated with a damped Lyman-α absorber (DLA) at nearly the same redshift 2.4007 ± 0.0003, with a neutral hydrogen column density of log N(H
The mass-metallicity relation of bulges
No full textContext. Bulges, located at the central regions of galaxies, are complex structures, expected to be shaped by the physical processes involved in the assembly history of their host galaxy, such as gravitational collapse, mergers, interactions, and bars. As a consequence, a variety of bulges with distinct morphologies and chemistry could be produced.
Aim. We aim to explore the existence of a stellar mass-metallicity relation of bulges, MZ*R, and analyze the possible imprint of distinctive features by accretion and migration of stars, which could store information in their assembly histories.
Methods. We used 44 central galaxies from the CIELO cosmological simulations. Their stellar masses are within the range of ∼[107.6, 1010.6] M⊙. We decomposed the galaxy into bulge and disk using the circularity and binding energies. We tracked the stellar populations in bulges back in time to their birth locations, classifying them as bulge- and disk-born, in-situ, and accreted.
Results. We find that most of the stars in our bulges are formed in-situ, but 33% of our bulges show a non-negligible contribution of stellar accretion from satellites, which could add to about 35% of the population. The accreted material is generally contributed by two or three satellites at most. In some bulges, we also find up to 32% of stars that migrated from the disk due to secular evolution, with a median of 10%. Regardless of the formation histories, we find a clear MZ*R for bulges, which is more enriched by about 0.4 dex than the corresponding relation of the disk components, and about 0.15 dex more enriched than the galaxy MZ*R. We find evidence that the dispersion in the bulge MZ*R is influenced by both stellar accretion from satellites and migration from the disk, such that, at a fixed bulge mass, bulges with higher fractions of accreted and migrated stars tend to be less metal-rich. Therefore, we find a MZ*R for bulges, which is consistent with an increase in metallicity with increasing mass, while its dispersion stores information on the contribution from different formation channels