The high mass X-ray binaries (HMXBs) provide an exciting framework to investigate the evolution of massive stars and the processes behind binary evolution. HMXBs have shown to be good tracers of recent star formation in galaxies and might be important feedback sources at early stages of the Universe. Furthermore, HMXBs are likely the progenitors of gravitational wave sources (BH–BH or BH–NS binaries that may merge producing gravitational waves). In this work, we investigate the nature and properties of HMXB population in star-forming galaxies. We combine the results from the population synthesis model MOBSE (Giacobbo & Mapelli 2018a) together with galaxy catalogs from EAGLE simulation (Schaye et al. 2015). Therefore, this method describes the HMXBs within their host galaxies in a self-consistent way. We compute the X-ray luminosity function (XLF) of HMXBs in star-forming galaxies, showing that this methodology matches the main features of the observed XLF.

SCALA is a physical calibration device for the SuperNova Integral Field Spectrograph (SNIFS), mounted to the University Hawaii 2.2m telescope on Mauna Kea. For type Ia supernova (SN Ia) cosmology programs, an improved fundamental calibration directly translates into improved cosmological constraints. The aim of SCALA is to perform a fundamental calibration of the CALSPEC (Bohlin 2014) standard stars, which are currently calibrated relative to white dwarf model atmospheres.

We have searched for a sign of the past dynamical disturbance events on NGC 1068, an archetypical Type-2 Seyfert galaxy, using deep and wide optical imaging data by the Subaru telescope. The data taken by Hyper Suprime-Cam (HSC) as well as the archived data by Suprime-Cam reveal several faint outer structures of the galaxy, most of which were never reported before. We discover three large (re = 3 -5.5 kpc), extremely diffuse objects (UDOs) within 45 kpc from the center of NGC 1068. We suggest that two of these UDOs are actually a part of a large loop-like structure surrounding NGC 1068. Such an extremely faint loop or stream is the direct evidence for a past minor merger event. The third UDO has a distorted morphology, suggesting that it is under the influence of strong tidal field. Furthermore, we have identified another ultra-diffuse but compact (μ0,r > 25 mag arcsec-2, re ~ 0.8kpc) dwarf galaxy within ~140 kpc from NGC 1068. We speculate that this ultra-diffuse dwarf could be the object related to the ancient tidal disruption event (tidal dwarf) during the early mass assembly period of NGC 1068. We also detect an asymmetric outer one-arm structure emanated from the western edge of the outermost disk of NGC 1068 together with a ripple-like structure at the opposite side. These structures are also expected to arise in a late phase (up to several billion years ago) of a minor merger, according to numerical simulations. Our findings are consistent with the idea that the AGN activity in NGC 1068 is caused by a past minor merger.

We study the distribution of mid-infrared light in stellar structures in a large sample (∽ 400) of low-mass (Mstellar <109 MSun) galaxies. Our sample is selected from the Spitzer Survey of Stellar Structures in Galaxies (S4G), which entails deep imaging of nearby galaxies with the IRAC instrument at 3.6/4.5 μ m. Based on the 2D decomposition of the 3.6μ m images, we find that the majority (∽65%) of galaxies in our sample is well-fit by a single disk profile. The rest of the sample is more adequately fit by a disk and an additional component (e.g., bar, nucleus, bulge, second disk component). Bars are present in ∽11% of the sample, marking a sharp drop in the bar fraction compared to that found for more massive galaxies. The typical contribution of bars to the 3.6 μ m light in dwarfs is ∽1-2%, lower than that found in more massive galaxies. These results bring a number of issues into question: why do low-mass galaxies have such low bar fraction? does the bar instability act differently in low-mass galaxies such that a smaller proportion of stellar mass is typically involved in the bar structure? Is the fact that dwarfs are more dark matter dominated playing a role?

In this work, we carry out two-fluid (gas+dust) hydrodynamical simulations on a large family of models in order to study the dust coagulation and the dust-gas dynamical processes in protoplanetary disks. Our theoretical effort is guided by the observational results of disks in nearby star forming regions at sub-millimeter and millimeter (mm) wavelengths. By a systematic comparison with the continuum emission at several mm bands from ALMA observations, we find that ringed structures are predicated in the unresolved faint disks for those with mm spectral indexes as low as about 2.0. Our parameter exploration can also be used to constrain the fragmentation velocity, one key parameter of the dust coagulation model, and some other disk parameters.

The supergiant high-mass X-ray binary IGR J16318-4848 was detected by INTEGRAL in 2003 and distinguishes itself by its high intrinsic absorption and B[e] phenomenon. It is the perfect candidate to study both binary interaction and the environment of supergiant B[e] stars. We report on VLT/X-Shooter observations from July 2012 in both optical and near-infrared, which provide unprecedented wide-range, well-resolved spectra of IGR J16318-4848 from 0.5 to 2.5 μm. Adding VLT/VISIR and Herschel data, the spectral energy distribution fitting allows us to further constrain the contribution of each emission region (central star, irradiated rim, dusty disc). We derive geometrical parameters using the numerous emitting and absorbing elements in each different sites in the binary. Various line shapes are detected, such as P-Cygni profiles and flat-topped lines, which are the signature of outflowing material. Preliminary results confirm the edge-on line of sight and the equatorial configuration of expanding material, along with the detection of a potentially very collimated polar outflow. These are evidence that the extreme environment of IGR J16318-4848 is ideal to have a better grasp of highly obscured high-mass X-ray binaries.

The role of asymptotic giant branch (AGB) stars in chemical enrichment is significant for producing 12,13C, 14N, F, 25,26Mg, 17O and slow neutron-capture process (s-process) elements. The contribution from super-AGB stars is negligible in classical, one-zone chemical evolution models, but the mass ranges can be constrained through the contribution from electron-capture supernovae and possibly hybrid C+O+Ne white dwarfs, if they explode as Type Iax supernovae. In addition to the recent s-process yields of AGB stars, we include various sites for rapid neutron-capture processes (r-processes) in our chemodynamical simulations of a Milky Way type galaxy. We find that neither electron-capture supernovae or neutrino-driven winds are able to adequately produce heavy neutron-capture elements such as Eu in quantities to match observations. Both neutron-star mergers (NSMs) and magneto-rotational supernovae (MRSNe) are able to produce these elements in sufficient quantities. Using the distribution in [Eu/(Fe, α)] – [Fe/H], we predict that NSMs alone are unable to explain the observed Eu abundances, but may be able to together with MRSNe. In order to discuss the role of long-lifetime sources such as NSMs and AGB stars at the early stages of galaxy formation, it is necessary to use a model that can treat inhomogeneous chemical enrichment, such as in our chemodynamical simulations. In our cosmological, chemodynamical simulations, we succeed in reproducing the observed N/O-O/H relations both for global properties of galaxies and for local inter-stellar medium within galaxies, without rotation of stars. We also predict the evolution of CNO abundances of disk galaxies, from which it will be possible to constrain the star formation histories.

This study has been published in Sánchez-Menguiano et al. (2018). We encourage the reader to that article for more details on the study and the results.

We analyse the vertical distribution of High Mass X-ray Binaries (HMXBs) in NGC 55, the nearest edge-on galaxy to the Milky Way. Our analysis reveals significant spatial offsets of HMXBs from the star forming regions, greater than those observed in the SMC and the LMC but similar with the Milky Way. The spatial offsets can be explained by a momentum kick the X-ray binaries receive during the formation of the compact object. The difference between the scale height of the vertical distribution of HMXBs and the vertical distribution of star-forming activity is 0.48±0.04 kpc. The centre-of-mass velocity of the distribution of HMXBs in NGC 55 is moving at a velocity of 52.4±11.4 km s−1, greater than the corresponding velocity of HMXBs in the SMC and LMC, but consistent with velocities of Milky Way HMXBs.

Carbon-enhanced metal-poor stars are probes of the early universe, that teach us about metal-poor AGB stars and supernovae physics in the very first stars. We find a large fraction of CEMP-no stars with large absolute carbon abundance to be in binary systems. This may be an indication of binary interaction with ultra or extremely metal-poor AGB stars, curiously without enhancement in s-process elements.

The DARA Big Data project is a flagship UK Newton Fund & GCRF program in partnership with the South African Department of Science & Technology (DST). DARA Big Data provides bursaries for students from the partner countries of the African VLBI Network (AVN), namely Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia, to study for MSc(R) and PhD degrees at universities in South Africa and the UK. These degrees are in the three data intensive DARA Big Data focus areas of astrophysics, health data and sustainable agriculture. The project also provides training courses in machine learning, big data techniques and data intensive methodologies as part of the Big Data Africa initiative.

The populations of planetary nebulae (PNe) probe metallicity and chemical content (and its evolution) of the parent galaxy, giving clues to galaxy formation and evolution. This sub-field of extra-galactic PN research has been particularly active in the recent years. Comparison of data and models yielded estimates of global cosmic enrichment and provided constraints to galaxy formation history. In external spiral galaxies, the chemical contents of PNe and H II regions can be compared to disclose possible evolution of the radial metallicity gradient, which is, in turn, a powerful constraint to galactic chemical evolutionary models. In the Milky Way, recent PN progenitor dating and new chemical abundances offer an updated look into our own Galaxy. Collectively, Galactic and extra-galactic radial metallicity gradients from emission-line probes (PNe and H II regions) can be compared to have a cosmological outlook on galactic evolution.

Winds of hot stars are driven by the radiative force due to absorption of light in the lines of heavier elements. Consequently, the mass-loss rate and the wind velocity depend on the ionization state of the wind. As a result of this, there is a feedback between the ionizing X-ray source and the stellar wind in HMXBs powered by wind accretion. We study the influence of the small-scale wind structure (clumping) on this feedback using our NLTE hydrodynamical wind models. We find that clumping weakens the effect of X-ray irradiation. Moreover, we show that the observed X-ray luminosities of HMXBs can not be explained by wind accretion scenario without introducing the X-ray feedback. Taking into account the feedback, the observed and estimated X-ray luminosities nicely agree. We identify two cases of X-ray feedback with low and high X-ray luminosities that can explain the dichotomy between SFXTs and sgXBs.

A sample of 28 oxygen-rich evolved stars is selected based on the presence of crystalline silicate emission features in their ISO/SWS spectra. The crystallinity, measured as the flux fraction of crystalline silicate features, is found not to be related to mass loss rate that is derived from fitting the spectral energy distribution.

We have constructed a chemical evolution model in order to reproduce the both metallicity distribution functions (MDFs) of red giant branch stars (RGBs) and RR Lyrae stars (RRLs) of a dwarf galaxy, simultaneously. The detailed chemical abundances of RGBs of the Local Group dwarf galaxies have been measured by spectroscopic observations. Moreover, the metallicity of RRLs of a dwarf galaxy are estimated by using the theoretical period-luminosity relations in the previous study and it is found that the mean metallicity of RRLs are lower than that of RGBs. In order to investigate the MDFs of RGBs and RRLs, we combine our chemical evolution model with the stellar evolutionally isochrones and calculate the metallicity of RGBs and RRLs, respectively. As a result, our chemical evolution model reproduces the peak metallicity of both MDFs of RGBs and RRLs of Sculptor and Fornax dwarf spheroidal galaxies (dSphs), simultaneously. Therefore, it is found that the difference of the mean metallicity between RGBs and RRLs are caused by the effects of stellar evolution. Moreover, by using the theoretical period-luminosity-metallicity relation of the RRLs, our chemical evolution model determines that the distance modulus of Sculptor and Fornax dSphs are 19.68 ± 0.09 and ${20.81^{+0.13}_{-0.11}}$, respectively. However, our model underestimates the number of metal-rich RRLs ([Fe/H] > −1.5) of Fornax dSph. This result suggests that the mass-loss rate of metal-rich RGBs would be larger than that of metal-poor RGBs.

We present a catalog of the observed properties of Mira-type variable stars detected with the Kilodegree Extremely Little Telescope (KELT). Asymptotic giant branch (AGB) candidates were identified in KELT using a combination of photometric data from KELT and 2MASS colors. Of the 4 million objects with KELT photometry, 3332 Mira-like variables were identified. Here, we present their observed periods and luminosities which will place important constraints on future theoretical work on the effect convection has on pulsation periods and mode stability.

Astronomy has an enviable wealth of historical observations. Some verge on the archaeological, and display rare events such as novæ and supernovæ; others range up to 100 or more years in age, and bear unique information about events that will never repeat in detail. Yet most astronomers today know little of those resources and the scientific potential which they harbour, so rather infrequent use is made today of those historical data. The problem is that historical data were perforce obtained in analogue formats, and because of those formats the data too tend to be regarded as hailing from a culture whose scientific significance is passé. But the medium is not the message! Astronomy’s archives of photographic observations constitute an irreplaceable resource. The change in technology from analogue to electronic recording in the late 20th Century was abrupt, and it left most of today’s astronomers unable to handle and use photographic data, and led to a general skepticism of the value of photographic observations for present-day studies of variability in the cosmos. But that is precisely what older data can do; in particular, the older the data the more reliable the base-line against which one can measure new trends, refine orbital parameters, discern period modulations, etc.