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Disks around young stars are the sites of planet formation. As such, the physical and chemical structure of disks have a direct impact on the formation of planetary bodies. Outflowing winds remove angular momentum and mass and affect the disk structure and therefore potentially planet formation. Until very recently, we have lacked the facilities to provide the necessary observational tools to peer into the wind launching and planet forming regions of the young disks. Within the framework of the Resolving star formation with ALMA program, young protostellar systems are targeted with ALMA to resolve the disk formation, outflow launching and planet formation. This contribution presents the first results of the program. The first resolved images of outflow launching from a disk were recently reported towards the Class I source TMC1A (Bjerkeli et al. 2016) where we also present early evidence of grain growth (Harsono et al. 2018).
We performed a far-IR imaging survey of the circumstellar dust shells of 144 evolved stars as a mission program of the AKARI infrared astronomical satellite. Our objectives were to characterize the far-IR surface brightness distributions of the cold dust component in the circumstellar dust shells. We found that (1) far-IR emission was detected from all but one object, (2) roughly 60–70 % of the target sources showed some extension, (3) 29 sources were newly resolved in the far-IR in the vicinity of the target sources, (4) the results of photometry measurements were reasonable with respect to the entries in the AKARI/FIS Bright Source Catalogue, and (5) an IR two-color diagram would place the target sources in a roughly linear distribution that may correlate with the age of the circumstellar dust shell.
Ultraluminous X-ray sources (ULXs) are end points of stellar evolution. They are mostly interpreted as binary systems with a massive donor. They are also the most probable progenitors for BH-BH, and even more, for BH-NS coalescence. Parameters of ULXs are not know and need to be better determined, in particular the link with the metallicity of the environment which has been invoked frequently but not proven strongly. We have tackled this problem by using a MUSE DEEP mosaic of the Cartwheel galaxy and applying a Monte Carlo code that jointly fits spectroscopy and photometry. We measure the metallicity of the emitting gas in the ring and at the positions of X-ray sources by constructing spatially resolved emission line ratio maps and BPT diagnostic maps. The Carthweel is the archetypal ring galaxy and the location and formation time of new stellar populations is easier to reconstruct than in more normal galaxies. It has the largest population of ULXs ever observed in a single galaxy (16 sources have been classified as ULXs in Chandra and XMM-Newton data). The Cartwheel galaxy is therefore the ideal laboratory to study the relation between Star Formation (SF Rates and SF History) and number of ULXs and also their final fate. We find that the age of the stellar population in the outer ring is consistent with being produced in the impact (≤300Myr) and that the metallicity is mostly sub-solar, even if solutions can be found with a solar metallicity that account for most observed properties. The findings for the Cartwheel will be a testbed for further modelisation of binary formation and evolution paths.
Color term corrections for magnitudes measured on the UVIS2 relative to the UVIS1 detector of the WFC3 camera on board Hubble Space Telescope are needed for three ultra-violet filters, namely F218W, F225W, and F275W. The two WFC3 detectors have different quantum efficiencies in the ultra-violet regime (λ < 4,000 Å), resulting in different count rate ratios as a function of the spectral type of the source. In the worst case, for cool red sources measured on UVIS2, there is a magnitude offset relative to UVIS1 up to ∼ 0.08 mag, while the offset is negligible for hot (Teff ≳ 30,000 K) blue sources.
Using spatially resolved spectroscopy from the SDSS-IV Mapping Nearby Galaxies at APO (MaNGA) survey, we identify 69 dwarf elliptical (dE) galaxies in the nearby Universe fainter than Mr = −19 (MB = −18), selected independently of morphology and environment. The majority exhibit coherent rotation in their stellar kinematics, consistent with an origin as morphologically transformed disk galaxies. Six galaxies in this dE sample appear to host Active Galactic Nuclei (AGN) that are likely preventing current star formation through maintenance mode feedback. The ionised gas component of these dEs is typically kinematically offset from the stellar component, suggesting the gas is either recently accreted or outflowing. We therefore demonstrate the potential of IFU spectroscopy for understanding the physical properties of dwarf galaxies in detail.
Isotopic ratios are a powerful tool for gaining insights into stellar evolution and nucleosynthesis. The isotopic ratios of the key elements carbon and oxygen are perfectly suited to investigate the pristine composition of red giants, the conditions in their interiors, and the mixing in their extended atmospheres. Of course the dust ejected from red giants in their final evolution also contains isotopically tagged material. This red giant dust is present in the solar system as presolar dust grains. We have measured isotopic ratios of carbon and oxygen in spectra from a large sample of AGB stars including both Miras and semiregular variables. We show how the derived ratios compare with expectations from stellar models and with measurements in presolar grains. Comparison of isotopes that are affected by different types of nucleosynthesis provides insights into galactic evolution.
We present radiative transfer modelling of the dust around U Ant, a well-studied detached-shell source. U Ant is among the >400 sources targeted by the Nearby Evolved Stars Survey (NESS; PI: P. Scicluna), and the procedure used to model this source will be applied to the rest of the AGB sample in NESS.
A few Be X-ray binaries might constitute a group of special sources because the neutron stars in them may have superstrong magnetic fields. Generally, the neutron stars have long spin periods and some emission lines are shown from the B type star, which is attributed to an equatorial disc. We re-build new dimensionless torque models and obtain the superstrong magnetic fields of the neutron stars in the Be X-ray binaries in Large Magellanic Cloud, Small Magellanic Cloud and Milky Way when the compressed magnetosphere is considered. Although our conclusions are obtained when the disk accretion mode is considered, the results may be applied the Be X-ray binaries with wind accretion mode. SXP1323 and 4U 2206+54, in which the magnetic fields of the NSs may be close to the maximum ‘virial’ value, are the best objects to explore superstrong magnetic field.
To select asteroid families, the D(a) distribution of asteroid sizes by their semimajor axes and the N(p) distribution of the number of asteroids by their albedo values for individual families were used. A statistically significant reduction in the mean albedo with increasing semimajor axis is observed for almost all correctly identified families that are not truncated by resonances. This points on an action of a specific nongravitational effect (NGE) in the asteroid belt, and results in the spatial separation of asteroids with different albedos.
The outer stellar halo is home to a number of substructures that are remnants of former interactions of the Galaxy with its dwarf satellites. Triangulum-Andromeda (TriAnd) is one of these halo substructures, found as a debris cloud by Rocha-Pinto et al., (2004) using 2MASS M giants. Would be these structures related to dwarf galaxies or to the galactic disk? To uncover the nature of these stars we performed a high-resolution spectroscopic study (R = 40,000) along with a kinematic analysis using Gaia data. We determined the atmospheric parameters and chemical abundances of Ca and Mg for the 13 TriAnd candidate stars along with their respective orbits. Our results indicate that the TriAnd stars analyzed have a galactic nature but that these stars are not from the local thin disk.
Processing our increasingly large datasets poses a bottleneck for producing real scientific outcomes and citizen science - engaging the public in research - provides a solution, particularly when coupled with automated routines. In this talk we will provide a broad overview of citizen science approaches and best practices. We will also highlight in particular recent advances through Zooniverse, the world’s largest platform for online citizen science, engaging more than 1.7 million volunteers in tasks including discovering exoplanets, identifying features on Mars’ surface, transcribing artist’s notebooks, and tracking resistance to antibiotics.
We studied a sample of 1672 galaxies in regions where a GRB event had occurred, in order to determine if the galactic environment plays a significant role on these energetic events. The Luminosity Function distribution for these galaxies shows some interesting features. For instance, there is a decline on the Luminosity Function at Mr~ −20.5; a lack of flatness at Mr~ −14 and higher-than-expected values of Φ(Mr) for Mr < −22.5. A comparison between our data and the Void, Wall and Early galaxies Luminosity Function was performed.
Results of mass imaging nearby dwarf galaxies in emission Hα line and red continuum with the 6-meter BTA telescope are available via the address: http://www.sao.ru/lv/lvgdb. The sample of dwarfs limited by a distance of 11 Mpc contains about 500 objects. Their Hα - fluxes are used to derive integrated and specific star formation rates of the galaxies. We evaluate the consistency between star formation rates obtained from our Hα-survey and GALEX far-ultraviolet survey. We fix a systematic rise of the ratio SFR(FUV)/SFR(Hα) with the decreasing stellar mass of dwarf galaxies. In the sample there were included only galaxies of late types: T = 10 (Ir), 9 (Im, BCD), 8 (Sdm), 7 (Sd), 6 (Scd), since elliptical and lenticular galaxies, and also spiral with massive bulges, have a significantly different history of star formation.
Dwarf spheroidal galaxies of the Local Group share a similar characteristic nowadays: a low amount of gas in their interiors. In this work, we present results from a three-dimensional hydrodynamical simulation of the gas inside an object with similar characteristics of the Ursa Minor galaxy. We evolved the initial gas distribution over 3 Gyr, considering the effects of the types Ia and II supernovae. The instantaneous supernovae rates were derived from a chemical evolution model applied to spectroscopic data of the Ursa Minor galaxy. Our simulation shows that the amount of gas that is lost varies with time and galactocentric radius. The highest gas-loss rates occurred during the first 600 Myr of evolution. Our results also indicate that types Ia and II supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and probably in other similar dwarf galaxies).
The standard scenario for the production of carbon-enhanced extremely metal-poor (CEMP) stars requires a more massive binary companion, which has evolved through the AGB stage and transferred carbon-rich material to the surface of the surviving, likewise extremely metal-poor (EMP) star. Evidently, the binary companion plays a key role in this process.
In order to characterise the polluting star, if any, the stage of evolution of the observed star (whether RGB or AGB), and whether pulsations exist, must be known. The Gaia DR2 parallaxes and photometry should contain the answer.
At the end of their evolution, asymptotic giant branch (AGB) stars undergo strong pulsation, mass loss, and dust production. Their mass loss results in substantial chemical and dust enrichment of the interstellar medium. Dust evolution models and isotope abundances in presolar grains suggest that AGB stars play a key role in both dust evolution and the star formation process. They are also the brightest stars in galaxies, potentially dominating in the near-infrared. As a result, AGB stars have a significant influence on the evolution and appearance of their host galaxies and thus must be accounted for when interpreting a galaxy’s integrated light. I will highlight new results that describe the impact AGB stars have on galaxies, including how AGB stars are used to probe galaxy evolution.
With their sizes larger than 0.7 Mpc, Giant Radio Galaxies (GRGs) are the largest individual objects in the Universe. To date, the reason why they reach such enormous extensions is still unclear. One of the proposed scenarios suggests that they are the result of multiple episodes of jet activity. Cross-correlating the INTEGRAL+Swift AGN population with radio catalogues (NVSS, FIRST, SUMSS), we found that 22% of the sources are GRG (a factor four higher than those selected from radio catalogues). Remarkably, all of the sources in the sample show signs of restarting radio activity. The X-ray properties are consistent with this scenario, the sources being in a high-accretion, high-luminosity state with respect to the previous activity responsible for the radio lobes.