Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1509.05428

Velocity and magnetic fields within 1000 AU from a massive YSO

A. Sanna·G. Surcis·L. Moscadelli·R. Cesaroni·C. Goddi·W. H. T. Vlemmings·A. Caratti o Garatti
View original source ↗Read source document ↗Export metadata ↓

Abstract

We want to study the velocity and magnetic field morphology in the vicinity (<1000 AU) of a massive young stellar object (YSO), at very high spatial resolution (10-100 AU). We performed milli-arcsecond polarimetric observations of the strong CH3OH maser emission observed in the vicinity of an O-type YSO, in G023.01-00.41. We have combined this information with the velocity field of the CH3OH masing gas previously measured at the same angular resolution. We analyse the velocity and magnetic fields in the reference system defined by the direction of the molecular outflow and the equatorial plane of the hot molecular core at its base, as recently observed on sub-arcsecond scales. We provide a first detailed picture of the gas dynamics and magnetic field configuration within a radius of 2000 AU from a massive YSO. We have been able to reproduce the magnetic field lines for the outer regions (>600 AU) of the molecular envelope, where the magnetic field orientation shows a smooth change with the maser cloudlets position (0.2 degree/AU). Overall, the velocity field vectors well accommodate with the local, magnetic field direction, but still show an average misalignment of 30 degrees. We interpret this finding as the contribution of a turbulent velocity field of about 3.5 km/s, responsible for braking up the alignment between the velocity and magnetic field vectors. We do resolve different gas flows which develop both along the outflow axis and across the disk plane, with an average speed of 7 km/s. In the direction of the outflow axis, we establish a collimation of the gas flow, at a distance of about 1000 AU from the disk plane. In the disk region, gas appears to stream outward along the disk plane for radii greater than 500-600 AU, and inward for shorter radii.

Explore related subjects

astro-ph.SRastro-ph.GA

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. Sanna, G. Surcis, L. Moscadelli, R. Cesaroni, C. Goddi, W. H. T. Vlemmings, A. Caratti o Garatti. 2015-09-17. Velocity and magnetic fields within 1000 AU from a massive YSO. https://doi.org/10.1051/0004-6361%2F201526806

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Stochasticity in Stellar Yields Reflected in Supernova Dust Masses Across All Massive-Star Progenitors

Massive stars, ending their lives as supernovae (SNe), are among the primary sources of dust in galaxies. In this study, we derive theoretical upper limits on dust masses as a function of SN progenitors, assuming non-rotating single stars of solar metallicity, with initial masses between 9 and 120 Msun. Based on previously established models of dust formation chemistry in core-collapse SNe (CCSNe), we find that O-rich dust, particularly silicates and silica, dominates the dust budget, with masses ranging from 0.02 to 1.43 Msun, and that the total mass of O-rich dust increases with progenitor mass. C-rich amorphous carbon and silicon carbide dust are significant for lower-mass progenitors (10--15 Msun), but their mass never exceed 0.05 Msun. For progenitors up to 30 Msun, we provide best-fit functions describing the masses of O-rich dust, C-rich dust, and CO molecules. A large stochastic variation is found in the predicted masses of silicate dust, which correlates with the randomness of shell-merger events in the pre-explosion phases of massive stars. Furthermore, we show that the dust mass for a given progenitor can vary by a factor of 2--5, reflecting differences in pre-explosion abundance distributions predicted by the different stellar evolution models. We emphasize that the final dust yield in SNe is primarily determined by stochastic stellar yields and uncertainties in pre-explosion nucleosynthesis, while explosion properties mainly influence the timescales of dust formation.

astro-ph.SR↗
arXiv2026

3D Radiative MHD Modeling of Particle Beam Heating of the Solar Atmosphere

While solar flares are primarily associated with enhanced ultraviolet and X-ray emission, a subset of flares exhibit significant continuum brightening in visible light and are classified as white-light flares (WLFs). Despite extensive observational and modeling efforts, the physical mechanisms responsible for the compact, short-lived photospheric brightenings in WLF kernels observed during the impulsive phase of solar flares remain uncertain. Thick-target electron-beam models typically deposit energy in the upper chromosphere, and their ability to reproduce the magnitude and spatial localization of photospheric continuum enhancements observed in white-light flare kernels remains an open question. To investigate the role of self-consistent atmospheric structuring and multidimensional hydrodynamic transport in flare energy deposition, we perform three-dimensional radiative MHD simulations of electron-beam heating using the StellarBox code for a beam energy flux density of $10^{12}$ erg\,s$^{-1}$\,cm$^{-2}$ and low-energy cutoffs of 10--25\,keV. We then compute Fe\,I 6173\,Å~Stokes profiles using the RH 1.5D radiative transfer code for direct comparison with Helioseismic and Magnetic Imager (HMI) observations. The simulations produce strong upper-chromospheric heating, multiple shock fronts, and continuum enhancements up to a factor of 2.5 relative to pre-flare levels, comparable to continuum enhancements observed during strong X-class white-light flares. Comparison with one-dimensional RADYN simulations highlights the influence of fine-scale structuring on flare dynamics and continuum emission that arises in three-dimensional geometry.

astro-ph.SR↗
arXiv2026

Preparing for the Early eVolution Explorer: Photometric Diagnostics of Magnetospheric Accretion Geometry in Young Stellar Objects

The inner disk truncation radius, $R_T$, plays a crucial role in the regulation of star-disk interaction and the early evolution of star-disk-planet systems; however, measuring this parameter is observationally challenging. We present a new method for determining $R_T$ in young accreting systems that hinges on the color dependence of the accretion shock emission in multi-band time-domain surveys. Based on the accretion simulations of Robinson et al. (2017, 2021), we produce synthetic color-magnitude diagrams at near-UV and optical wavelengths that predict the loci of accreting stars as a function of $R_T$. We test these model predictions on young stars with interferometric $R_T$ estimates, finding very good agreement in our results. We apply this novel technique to a pilot survey of 26 classical T Tauri stars in Taurus and Upper Scorpius. We find a predominance of sources with small truncation radii, $R_T < 4\ R_\star$, and an overall distribution of $R_T$ that is statistically similar to that inferred from interferometric studies, while differing from those inferred from emission line modeling. Finally, we discuss the application of this technique to NASA's mission concept EVE, with the goal to provide simultaneous measurements of inner disk truncation radii, corotation radii and mass accretion rates for hundreds of young stars across the Galaxy. The unprecedented survey of inner disk properties that the mission would produce would enable the first stringent test of angular momentum evolution theories in young stars and reveal the impact of the inner disk conditions on early planet architectures.

astro-ph.SR↗