Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA High-Mass Protobinary System in the Hot Core W3(H2O)
85
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We have observed a high-mass protobinary system in the hot core W3(H2O) with the BIMA Array. Our continuum maps at wavelengths of 1.4mm and 2.8mm both achieve sub-arcsecond angular resolutions and show a double-peaked morphology. The angular separation of the two sources is 1.19 corresponding to 2.43X10^3 AU at the source distance of 2.04 kpc. The flux densities of the two sources at 1.4mm and 2.8mm have a spectral index of 3, translating to an opacity law of kappa ~ nu. The small spectral indices suggest that grain growth has begun in the hot core. We have also observed 5 K components of the CH3CN (12-11) transitions. A radial velocity difference of 2.81 km/s is found towards the two continuum peaks. Interpreting these two sources as binary components in orbit about one another, we find a minimum mass of 22 Msun for the system. Radiative transfer models are constructed to explain both the continuum and methyl cyanide line observations of each source. Power-law distributions of both density and temperature are derived. Density distributions close to the free-fall value, r^-1.5, are found for both components, suggesting continuing accretion. The derived luminosities suggest the two sources have equivalent zero-age main sequence (ZAMS) spectral type B0.5 - B0. The nebular masses derived from the continuum observations are about 5 Msun for source A and 4 Msun for source C. A velocity gradient previously detected may be explained by unresolved binary rotation with a small velocity difference.
rate research
Read More
Sensitive and high angular resolution ($sim$ $0rlap.{}7$) (sub)millimeter line and continuum observations of the massive star forming region W3(OH) made with the Submillimeter Array are presented. We report the first detection of two bipolar outflows emanating from the young and massive Turner-Welch [TW] protobinary system detected by the emission of the carbon monoxide. The outflows are massive (10 M$_odot$), highly-collimated (10$^circ$), and seem to be the extended molecular component of the strong radio jets and a 22 GHz maser water outflow energized also by the stars in the W3(OH)TW system. Observations of the 890 $mu$m continuum emission and the thermal emission of the CH$_3$OH might suggest the presence of two rotating circumstellar disk-like structures associated with the binary system. The disks-like structures have sizes of about 1500 AU, masses of a few M$_odot$ and appear to energize the molecular outflows and radio jets. We estimate that the young stars feeding the outflows and that are surrounded by the massive disk-like structures maybe are B-type.
The fragmentation mode of high-mass molecular clumps and the properties of the central rotating structures surrounding the most luminous objects have yet to be comprehensively characterised. Using the IRAM NOrthern Extended Millimeter Array (NOEMA) and the IRAM 30-m telescope, the CORE survey has obtained high-resolution observations of 20 well-known highly luminous star-forming regions in the 1.37 mm wavelength regime in both line and dust continuum emission. We present the spectral line setup of the CORE survey and a case study for W3(H2O). At ~0.35 (700 AU at 2 kpc) resolution, the W3(H2O) clump fragments into two cores (West and East), separated by ~2300 AU. Velocity shifts of a few km/s are observed in the dense-gas tracer, CH3CN, across both cores, consistent with rotation and perpendicular to the directions of two bipolar outflows, one emanating from each core. The kinematics of the rotating structure about W3(H2O) W shows signs of differential rotation of material, possibly in a disk-like object. The observed rotational signature around W3(H2O) E may be due to a disk-like object, an unresolved binary (or multiple) system, or a combination of both. We fit the emission of CH3CN (12-11) K = 4-6 and derive a gas temperature map with a median temperature of ~165 K across W3(H2O). We create a Toomre Q map to study the stability of the rotating structures against gravitational instability. The rotating structures appear to be Toomre unstable close to their outer boundaries, with a possibility of further fragmentation in the differentially-rotating core W3(H2O) W. Rapid cooling in the Toomre-unstable regions supports the fragmentation scenario. Combining millimeter dust continuum and spectral line data toward the famous high-mass star-forming region W3(H2O), we identify core fragmentation on large scales, and indications for possible disk fragmentation on smaller spatial scales.
High-mass multiples might form via fragmentation of self-gravitational disks or alternative scenarios such as disk-assisted capture. However, only few observational constraints exist on the architecture and disk structure of high-mass protobinaries and their accretion properties. Here we report the discovery of a close ($57.9pm0.2$mas=170au) high-mass protobinary, IRAS17216-3801, where our VLTI/GRAVITY+AMBER near-infrared interferometry allows us to image the circumstellar disks around the individual components with 3 milliarcsecond resolution. We estimate the component masses to $sim20$ and $sim18 M_{odot}$ and find that the radial intensity profiles can be reproduced with an irradiated disk model, where the inner regions are excavated of dust, likely tracing the dust sublimation region in these disks. The circumstellar disks are strongly misaligned with respect to the binary separation vector, which indicates that the tidal forces did not have time to realign the disks, pointing towards a young dynamical age of the system. We constrain the distribution of the Br$gamma$ and CO-emitting gas using VLTI/GRAVITY spectro-interferometry and VLT/CRIRES spectro-astrometry and find that the secondary is accreting at a higher rate than the primary. VLT/NACO imaging shows $L$-band emission on 3-4 times larger scales than the binary separation, matching the expected dynamical truncation radius for the circumbinary disk. The IRAS17216-3801 system is $sim3times$ more massive and $sim5times$ more compact than other high-mass multiplies imaged at infrared wavelengths and the first high-mass protobinary system where circumstellar and circumbinary dust disks could be spatially resolved. This opens exciting new opportunities for studying star-disk interactions and the role of multiplicity in high-mass star formation.
We present the first interferometric polarization map of the W3(OH) massive star-forming region observed with the Submillimeter Array (SMA) at 878 mum with an angular resolution of 1.5 (about 3 times 10 AU). Polarization is detected in the W3(H2O) hot core, an extended emission structure in the north-west of W3(H2O), and part of the W3(OH) ultracompact HII region. The W3(H2O) hot core is known to be associated with a synchrotron jet along the east-west direction. In this core, the inferred magnetic field orientation is well aligned with the synchrotron jet and close to the plane of sky. Using the Chandrasekhar-Fermi method with the observed dispersion in polarization angle, we estimate a plane-of-sky magnetic field strength of 17.0 mG. Combined with water maser Zeeman measurements, the total magnetic field strength is estimated to be 17.1 mG, comparable to the field strength estimated from the synchrotron model. The magnetic field energy dominates over turbulence in this core. In addition, the depolarization effect is discerned in both SMA and JCMT measurements. Despite the great difference in angular resolutions and map extents, the polarization percentage shows a similar power-law dependence with the beam averaged column density. We suggest that the column density may be an important factor to consider when interpreting the depolarization effect.
We present SubMillimeter-Array observations of a Keplerian disk around the Class I protobinary system L1551 NE in 335 GHz continuum emission and submillimeter line emission in 13CO (J=3-2) and C18O (J=3-2) at a resolution of ~120 x 80 AU. The 335-GHz dust-continuum image shows a strong central peak closely coincident with the binary protostars and likely corresponding to circumstellar disks, surrounded by a ~600 x 300 AU feature elongated approximately perpendicular to the [Fe II] jet from the southern protostellar component suggestive of a circumbinary disk. The 13CO and C18O images confirm that the circumbinary continuum feature is indeed a rotating disk; furthermore, the C18O channel maps can be well modeled by a geometrically-thin disk exhibiting Keplerian rotation. We estimate a mass for the circumbinary disk of ~0.03-0.12 Msun, compared with an enclosed mass of ~0.8 Msun that is dominated by the protobinary system. Compared with several other Class I protostars known to exhibit Keplerian disks, L1551 NE has the lowest bolometric temperature (~91 K), highest envelope mass (~0.39 Msun), and the lowest ratio in stellar mass to envelope + disk + stellar mass (~0.65). L1551 NE may therefore be the youngest protostellar object so far found to exhibit a Keplerian disk. Our observations present firm evidence that Keplerian disks around binary protostellar systems, ``Keplerian circumbinary disks, can exist. We speculate that tidal effects from binary companions could transport angular momenta toward the inner edge of the circumbinary disk and create the Keplerian circumbinary disk.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
