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Over the last two decades, strong gravitational lensing has emerged as a potential method for studying the nature and distribution of dark matter on sub-galactic scales. In addition to the main lens substructure, line-of-sight dark matter haloes contribute greatly to the subtle perturbations of lensed images. Line-of-sight haloes, unlike dark matter subhaloes, imprint distinct anisotropic and quadrupole signatures in the maps that depict the divergence and curl of the effective deflection field, respectively, giving rise to quadrupole moments of the image-plane averaged two-point correlation function of these maps. In terms of central density evolution and dark matter halo distribution, the shapes and amplitudes of the two-point function multipoles alter dramatically in the presence of warm dark matter and self-interacting dark matter. This method, in conjunction with upcoming large-scale surveys, provides the prospect of improving the constraints on dark matter at a critical time in strong gravitational lensing research.
The 64-dish MeerKAT telescope was inaugurated in 2018 and has been conducting regular science operations since then. In the meantime, new observation modes have been under development. Spectral line modes are available, as well as L-, UHF- and S-band receivers. MeerKAT’s excellent sensitivity over a wide range of angular scales makes it an excellent choice for studies of HII regions, supernova remnants and planetary nebulae. In addition, an OH megamaser has been detected at z > 0.5 for the first time.
OH/IR stars are low- to intermediate-mass stars (about 0.5-8 solar masses) in the AGB phase, and are considered to be in the process of evolving from Mira variables to planetary nebulae. We aim to understand the evolutionary stages of these AGB stars by approaching them from astrometric VLBI observations with VERA. In 2017, we have started VLBI observations of several OH/IR stars including OH39.7+1.5 presented in this poster. We observed the H2O maser of OH39.7+1.5 and obtained an annual parallax of 0.55 ± 0.03 mas (distance D = 1.81 ± 0.12 kpc). Using this annual parallax, we revealed distribution (about 35 au square), internal motions, and expansion velocities (average about 15.4 ± 5.1 km s-1) of the maser spots. We compared expansion velocity of H2O maser with that of OH maser and found to be consistent across the error range. This suggests that the radial velocity of H2O gas around OH39.7+1.5 has reached a terminal velocity. OH39.7+1.5 has not data on annual parallax or proper motion in Gaia DR3, and this is the first time that annual parallax has been measured.
The space domain has undergone several changes in the last decade (aka “new space era”), and will continue to do so in coming years. This led to several challenges which should be recognized and tackled by all actors of this domain, including scientists.
Investigating the thermal and non-thermal processes in galaxies is vital to understand their evolution over cosmic time. This can best be studied by combining the radio and optical/near-infrared observations of galaxies. The JWST can resolve the evolution of the thermal processes by mapping ionized gas and dust in distant galaxies. This information combined with the upcoming surveys with the Square Kilometer Array (SKA) will make a major breakthrough in mapping the non-thermal processes and understanding their role in the evolution of galaxies. Our simulations show that SKA surveys will be able to trace the evolution history of spiral galaxies such as M 51 and NGC 6946 back to a redshift of 3 already in its first phase of construction. This study indicates the important role of the non-thermal pressure inserted by cosmic rays and magnetic fields in deriving winds and outflows at cosmic noon as deduced by a flat synchrotron spectrum in star forming galaxies.
We present in the following the introductory talk on “Hazardous asteroids and the Hera mission”, made during the round table on Space Awareness. It reminds the context of our awareness for near-Earth objects, the characterisation of risk, current international surveillance programmes, and mitigation measures in particular with space missions, and last, a rendez-vous with Apophis to note in your agenda for 2029.
Pulsating stars play a crucial role in the calibration of the cosmic distance scale as well as in tracing the properties of the associated stellar populations. In the era of large observational surveys and precise astrometric missions, it is crucial to rely on accurate stellar pulsation models able to predict the observed behaviors for different physical assumptions. Indeed, the relations currently used in the literature to derive individual and mean distances of mainly radially pulsating stars such as Cepheids and RR Lyrae are well physically understood, but are also known to depend on a number of often unknown parameters. Recent extensive sets of stellar pulsation models developed by various authors show how variations in the physical assumptions can affect the theoretical prediction of the instability strip boundaries, the morphology and amplitude of light and radial velocity curves, and the consequent Period-Luminosity, Period-Luminosity-Color and Period-Wesenheit relations. These aspects are discussed in the framework of current open problems in the field of classical pulsating stars.
We present the first results of simultaneous observations of the 6.035 GHz exited OH and 6.7 GHz methanol masers toward a sample of 10 high-mass young stellar objects (HMYSOs), observed using eMERLIN in 2020 and 2022. Searching for the coincidence and avoidance of these two maser transitions, we estimate physical conditions around central protostars. We identify Zeeman-splittings of the OH emission and determine the strength of the magnetic field. Combining it with linear polarization, we derive the magnetic field structure in these high-mass star-forming regions.
This is a multi-wavelength study to examine the G45.804-0.355 massive star-forming region (SFR) and its environs. Using MeerKAT with angular resolution (θ) of 8″ at 1.28 GHz, we identify for the first time, a faint radio continuum emission core in G45.804-0.355. At 1.3 mm, ALMA observations (θ∼0″ 7) resolved the core into multiple dust continuum condensations including MM1 which was found to be the primary massive dust dense core in the region (mass Mc∼ 54.3M⊙). The dust continuum shows an arm-like extended emission within which other dense cores are situated. The velocity gradient of the MM1 core indicates that the source is associated with a rotation gas motion. The red- and blue-shifted lobes overlap at the position of MM1. The compact morphology of the 4.5 μm IR emission, the presence of spiral arms and overlapping of the red- and blue-shifted lobes suggest a face-on geometry of G45.80-40.355.
HD34445 is a system that consists of a star and six planets. In some previous work, we investigated the dynamical stability of the system by means of numerical simulations. Here, we explore the system further by carrying out additional numerical experiments. A total of 100000 simulations confirm previous findings of the stability status of the system at the 1σ and 99% c.i. level. We find that only 2.7% of the systems with parameters varied within 1σ from the mean were unstable, while that percentage rose to about 28% for systems with parameter values taken within the 99% c.i. These preliminary results are presented and discussed herein.
Maser polarization observations have been successfully used to characterize magnetic fields towards a variety of astrophysical objects. Circular polarization yields the magnetic field strength of the maser source, and linear polarization yields information on the magnetic field morphology. Linear polarization can be produced when the maser saturates or through its anisotropic pumping. We present a comprehensive model of the polarization of masers. In contrast to regular excitation modeling, we relax the assumption of isotropically populated level populations, and model both the total population and level alignments. Through this approach, we obtain quantitative estimates on the anisotropic pumping of a variety of maser sources. In this way, the maser polarization may be related to the gas density, temperature, geometry and the magnetic field. Using the results of our modeling, we discuss, and give predictions, of the polarization of SiO, methanol, and water (mega)masers.
Gaia space mission of the European Space Agency was launched at the end of 2013 and will continue operations until 2025. The published data releases revolutionize the view of the Milky Way galaxy and beyond thanks to its unprecedented astrometry, photometry and spectroscopy. The paper reviews the products of the last data release of the Gaia mission and some of the scientific impacts of the data. We also discuss the future perspectives of Galaxy astrometry from space.
In the last 20 years a small group of 6.7GHz methanol maser sources displaying periodic variability have been identified. This variability is thought to reflect local processes linked to star formation. A number of models have been proposed e.g. colliding wind binary, protostellar pulsation, accretion on binary system. Recent studies of known sources as well as non-periodic flaring masers suggest an episodic accretion as a driving mechanism. We present the results of VLBI observation program aimed at studying known periodic methanol maser sources. High resolution maps of emission, source morphology and evolution in time will be discussed. Those results will help us fully understand the nature of maser periodicity in star forming regions.
We report new detections of SiO ν = 1 and ν = 2 J = 1 → 0 masers in the “water fountain” source IRAS 16552-3050, which was observed with the Nobeyama 45 m telescope from March 2021 to April 2023. Water fountains are evolved stars whose H2O maser spectra trace high-velocity outflows of >100 Km s−. This is the second known case of SiO masers in a water fountain, after their prototypical source, W 43A. The line-of-sight velocity of the SiO masers are blue-shifted by ∼25 km s−1 from the systemic velocity. This velocity offset imply that the SiO masers are associated with nozzle structure formed by a jet penetrating the circumstellar envelope, and that new gas blobs of the jet erupted recently. Thus, the SiO masers imply this star to be in a new evolutionary stage.
Since 2009, the Torun 32 m radio telescope has been used to monitor a sample of ∼140 sources of the 6.7 GHz methanol maser emission. In 2022, the sample was extended to about 250 targets. Approximately three-quarters show variability greater than 10% on timescales of a few weeks to several years. The most significant results are detecting a few flare events and discovering about a dozen periodic variables with periods ranging from a month to a few years. Here, we present the preliminary analysis of the properties of periodic masers.
Imaging the bright maser emission produced by the various molecular species from 1.6 to 116 GHz provides a way to probe the kinematics of dense molecular gas at high angular resolution. Unimpeded by the high dust optical depths that affect shorter wavelength (sub)mm observations, the high brightness temperature of these emission lines have become an essential tool for understanding the process of massive star formation. Operating from 1.2–116 GHz, the next generation Very Large Array (ngVLA) of 263 antennas will provide the capabilities needed to fully exploit these powerful tracers, including the ability to resolve accretion and outflow motions down to scales as fine as ∼1-10 au in deeply embedded Galactic star-forming regions, and at sub-pc scales in nearby galaxies. I will summarize the proposed specifications of the ngVLA, describe the current status of the project, and offer examples of future experiments designed to image the vicinity of massive protostars in continuum, thermal lines, and maser lines simultaneously.