scholarly journals Search for high-mass protostars with ALMA revealed up to kilo-parsec scales (SPARKS)

2019 ◽  
Vol 632 ◽  
pp. A57 ◽  
Author(s):  
T. Csengeri ◽  
A. Belloche ◽  
S. Bontemps ◽  
F. Wyrowski ◽  
K. M. Menten ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Moderate Temperature ◽  
Molecular Composition ◽  
High Mass ◽  
Central Position ◽  
Molecular Emission ◽  
Physical Location ◽  
Inner Region ◽  
Inner Envelope ◽  
Accretion Shocks

Context. Classical hot cores are rich in molecular emission, and they show a high abundance of complex organic molecules (COMs). The emergence of molecular complexity that is represented by COMs, in particular, is poorly constrained in the early evolution of hot cores. Aims. We put observational constraints on the physical location of COMs in a resolved high-mass protostellar envelope associated with the G328.2551−0.5321 clump. The protostar is single down to ~400 au scales and we resolved the envelope structure down to this scale. Methods. High angular resolution observations using the Atacama Large Millimeter Array allowed us to resolve the structure of the inner envelope and pin down the emission region of COMs. We use local thermodynamic equilibrium modelling of the available 7.5 GHz bandwidth around ~345 GHz to identify the COMs towards two accretion shocks and a selected position representing the bulk emission of the inner envelope. We quantitatively discuss the derived molecular column densities and abundances towards these positions, and use our line identification to qualitatively compare this to the emission of COMs seen towards the central position, corresponding to the protostar and its accretion disk. Results. We detect emission from 10 COMs, and identify a line of deuterated water (HDO). In addition to methanol (CH3OH), methyl formate (CH3OCHO) and formamide (HC(O)NH2) have the most extended emission. Together with HDO, these molecules are found to be associated with both the accretion shocks and the inner envelope, which has a moderate temperature of Tkin ~ 110 K. We find a significant difference in the distribution of COMs. O-bearing COMs, such as ethanol, acetone, and ethylene glycol are almost exclusively found and show a higher abundance towards the accretion shocks with Tkin ~ 180 K. Whereas N-bearing COMs with a CN group, such as vinyl and ethyl cyanide peak on the central position, thus the protostar and the accretion disk. The molecular composition is similar towards the two shock positions, while it is significantly different towards the inner envelope, suggesting an increase in abundance of O-bearing COMs towards the accretion shocks. Conclusions. We present the first observational evidence for a large column density of COMs seen towards accretion shocks at the centrifugal barrier at the inner envelope. The overall molecular emission shows increased molecular abundances of COMs towards the accretion shocks compared to the inner envelope. The bulk of the gas from the inner envelope is still at a moderate temperature of Tkin ~ 110 K, and we find that the radiatively heated inner region is very compact (<1000 au). Since the molecular composition is dominated by that of the accretion shocks and the radiatively heated hot inner region is very compact, we propose this source to be a precursor to a classical, radiatively heated hot core. By imaging the physical location of HDO, we find that it is consistent with an origin within the moderately heated inner envelope, suggesting that it originates from sublimation of ice from the grain surface and its destruction in the vicinity of the heating source has not been efficient yet.

Chemical differentiation in the inner envelope of a young high-mass protostar associated with Class II methanol maser emission

2017 ◽  
Vol 13 (S336) ◽  
pp. 331-333
Author(s):  
T. Csengeri ◽  
S. Bontemps ◽  
F. Wyrowski ◽  
A. Belloche ◽  
K. M. Menten ◽  
...  
Keyword(s):  
Excited State ◽  
Accretion Disk ◽  
State Transition ◽  
Dust Emission ◽  
High Mass ◽  
Methanol Maser ◽  
Molecular Outflow ◽  
Bright Emission ◽  
Inner Envelope

AbstractWe present a case study of a single high-mass protostar associated with an infrared quiet massive clump selected from the ATLASGAL survey. The thermal dust emission reveals a single collapsing object associated with a prominent molecular outflow. We detect bright emission from a torsionally excited state transition of CH3OH offset from the protostar that is well explained by shocks at the transition from the infalling envelope onto an accretion disk.

scholarly journals HOT HIGH-MASS ACCRETION DISK CANDIDATES

2009 ◽  
Vol 184 (2) ◽  
pp. 366-386 ◽  
Author(s):  
H. Beuther ◽  
A. J. Walsh ◽  
S. N. Longmore
Keyword(s):  
Accretion Disk ◽  
High Mass

scholarly journals Orbital motion and quasi-quantized disk around rotating neutron stars

2014 ◽  
Vol 23 (06) ◽  
pp. 1450053 ◽  
Author(s):  
Joan Jing Wang ◽  
Hsiang-Kuang Chang
Keyword(s):  
Accretion Disk ◽  
Orbital Motion ◽  
Photon Polarization ◽  
X Ray ◽  
Frame Dragging ◽  
Accretion Flows ◽  
Promising Tool ◽  
Disk Structure ◽  
Low Mass ◽  
Inner Region

In accreting neutron star (NS) low-mass X-ray binary (LMXB) systems, NS accretes material from its low-mass companion via a Keplerian disk. In a viscous accretion disk, inflows orbit the NS and spiral in due to dissipative processes, such as the viscous process and collisions of elements. The dynamics of accretion flows in the inner region of an accretion disk is significantly affected by the rotation of NS. The rotation makes NS, thus the spacetime metric, deviate from the originally spherical symmetry, and leads to gravitational quadrupole, on one hand. On the other hand, a rotating NS drags the local inertial frame in its vicinity, which is known as the rotational frame-dragging effect. In this paper, we investigate the orbital motion of accretion flows of accreting NS/LMXBs and demonstrate that the rotational effects of NS result in a band of quasi-quantized structure in the inner region of the accretion disk, which is different, in nature, from the scenario in the strong gravity of black hole arising from the resonance for frequencies related to epicyclic and orbital motions. We also demonstrate that such a disk structure may account for frequencies seen in X-ray variability, such as quasi-periodic oscillations (QPOs), and can be a potential promising tool for the investigation of photon polarization.

scholarly journals Dynamical Evolution of Accretion Flow onto a Black Hole

1998 ◽  
Vol 188 ◽  
pp. 455-456
Author(s):  
M. Yokosawa
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Event Horizon ◽  
Accretion Disk ◽  
Dynamical Evolution ◽  
Galactic Nuclei ◽  
Thick Disk ◽  
X Ray ◽  
General Relativistic ◽  
Inner Region

Active galactic nuclei(AGN) produce many type of active phenomena, powerful X-ray emission, UV hump, narrow beam ejection, gamma-ray emission. Energy of these phenomena is thought to be brought out binding energy between a black hole and surrounding matter. What condition around a black hole produces many type of active phenomena? We investigated dynamical evolution of accretion flow onto a black hole by using a general-relativistic, hydrodynamic code which contains a viscosity based on the alpha-model. We find three types of flow's pattern, depending on thickness of accretion disk. In a case of the thin disk with a thickness less than the radius of the event horizon at the vicinity of a marginally stable orbit, the accreting flow through a surface of the marginally stable orbit becomes thinner due to additional cooling caused by a general-relativistic Roche-lobe overflow and horizontal advection of heat. An accretion disk with a middle thickness, 2rh≤h≤ 3rh, divides into two flows: the upper region of the accreting flow expands into the atmosphere of the black hole, and the inner region of the flow becomes thinner, smoothly accreting onto the black hole. The expansion of the flow generates a dynamically violent structure around the event horizon. The kinetic energy of the violent motion becomes equivalent to the thermal energy of the accreting disk. The shock heating due to violent motion produces a thermally driven wind which flows through the atmosphere above the accretion disk. A very thick disk, 4rh≤h,forms a narrow beam whose energy is largely supplied from hot region generated by shock wave. The accretion flowing through the thick disk,h≥ 2rh, cannot only form a single, laminar flow falling into the black hole, but also produces turbulent-like structure above the event horizon. The middle disk may possibly emit the X-ray radiation observed in active galactic nuclei. The thin disk may produce UV hump of Seyfert galaxy. Thick disk may produce a jet observed in radio galaxy. The thickness of the disk is determined by accretion rate, such ashκ κes/cṁf(r) κ 10rhṁf(r), at the inner region of the disk where the radiation pressure dominates over the gas pressure. Here, Ṁ is the accretion rate and ṁ is the normarized one by the critical-mass flux of the Eddington limit. κesandcare the opacity by electron scattering and the velocity of light.f(r) is a function with a value of unity far from the hole.

scholarly journals Carina’s pillars of destruction: the view from ALMA

2019 ◽  
Vol 491 (1) ◽  
pp. 178-200 ◽  
Author(s):  
P D Klaassen ◽  
M R Reiter ◽  
A F McLeod ◽  
J C Mottram ◽  
J E Dale ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Incident Radiation ◽  
High Mass ◽  
Next Generation ◽  
Molecular Emission ◽  
Internal Motions ◽  
Wide Range ◽  
Stochastic Development ◽  
Feedback Pathways ◽  
Compact Array

ABSTRACT Forming high-mass stars have a significant effect on their natal environment. Their feedback pathways, including winds, outflows, and ionizing radiation, shape the evolution of their surroundings which impacts the formation of the next generation of stars. They create or reveal dense pillars of gas and dust towards the edges of the cavities they clear. They are modelled in feedback simulations, and the sizes and shapes of the pillars produced are consistent with those observed. However, these models predict measurably different kinematics which provides testable discriminants. Here we present the first ALMA Compact Array (ACA) survey of 13 pillars in Carina, observed in 12CO, 13CO, and C18O J = 2–1, and the 230 GHz continuum. The pillars in this survey were chosen to cover a wide range in properties relating to the amount and direction of incident radiation, proximity to nearby irradiating clusters and cloud rims, and whether they are detached from the cloud. With these data, we are able to discriminate between models. We generally find pillar velocity dispersions of &lt;1 km s−1 and that the outer few layers of molecular emission in these pillars show no significant offsets from each other, suggesting little bulk internal motions within the pillars. There are instances where the pillars are offset in velocity from their parental cloud rim, and some with no offset, hinting at a stochastic development of these motions.

scholarly journals Inelastic and quasi-elastic neutron scattering. Application to soft-matter

2018 ◽  
Vol 188 ◽  
pp. 05001 ◽  
Author(s):  
Quentin Berrod ◽  
Karine Lagrené ◽  
Jacques Ollivier ◽  
Jean-Marc Zanotti
Keyword(s):  
Neutron Scattering ◽  
Polymer Chain ◽  
Soft Matter ◽  
Common Ground ◽  
High Mass ◽  
Central Position ◽  
Multiscale Approach ◽  
Elastic Neutron ◽  
Matter Transport ◽  
Elastic Neutron Scattering

Microscopic dynamical events control many of the physical processes at play in condensed matter: transport, magnetism, catalysis and even function of biological assemblies. Inelastic (INS) and Quasi-Elastic Neutron Scattering (QENS) are irreplaceable probes of these phenomena. These experimental techniques reveal the displacements of atoms and molecules over distances spanning from angstroms to a few tens of nanometers, on time scales ranging from a fraction of picoseconds to microseconds. In this context, the different INS and QENS machines (Time-of-Flight (ToF), Backscattering (BS) and Neutron spin-echo (NSE)) stand at a central position. After introducing an underlying basic theoretical toolbox for neutron scattering, the principles and key elements of a ToF measurement are described. While, here, we mainly focus on disk choppers spectrometers, all the INS/QENS instruments share a common ground: they directly and simultaneously probe correlation functions in both time and space, so that the scattering vector (Q) dependence of the systems characteristic time(s) can be measured. To illustrate, the potentialities of the technique in the field of soft-matter, we show a multiscale approach of the dynamics of a polymer melt. The system is probed from the molecular to the mesoscopic scale (1 ps to 0.6 μs and 0.1 to 40 nm), in bulk and under nanometric confinement. We address the different dynamical modes of a high mass entangled polymer chain: local monomer dynamics, Rouse modes up to the reptation process. This study exemplifies that, used in conjunction with hydrogen/deuterium isotopic effects, high resolution QENS can be bridged to the Zero Average Contrast (ZAC) method to probe, in a non destructive way, the dynamics of a single polymer chain in bulk but also under severe nanometric confinement. Connection and complementarity of the neutron derived analysis with Pulsed-Field Gradient and Relaxation NMR techniques are discussed.

scholarly journals THE 3-D NUMERICAL SIMULATIONS OF THE DEPENDENCE OF THE DISK STRUCTURE FROM THE WIND CONFIGURATION IN ONE-POINT IN MICROQUASAR CYG X-1. THE CASE OF THE HIGH RESOLUTION GRID IN THE VERTICAL DIRECTION

2021 ◽  
Vol 34 ◽  
pp. 56-58
Author(s):  
V.V. Nazarenko
Keyword(s):  
Accretion Disk ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Vertical Direction ◽  
The Other ◽  
High Mass ◽  
Close Binary ◽  
Standard Size ◽  
Disk Radius ◽  
Disk Structure

The present paper is devoted to the investigation how the disk structure is depending from the one-point wind one in microquasar CYG X-1. The results show that when the region in which the wind is absent in the vicinity of one-point has the size less or equal to 0.07 the disk radius is very small, order of 0.08 in units of orbital separation. When this size is increased to 0.115 the disk radius becomes to be of standard size to be equal to 0.22 in units of orbital separation. By the other words these results show that the disk structure is strong depending from many factors including and the donor’s wind configuration in the vicinity of one-point. This configuration is inherent to microquasars only. Indeed, since microqausars are the massive close binary systems; the donor in these systems is massive star from which the strong radiation- driving wind is blowing. On the other hand, in microquasars accretion disks are present and it means that one-point stream is also present in microqausars. It in turn means that the matter configuration in the vicinity of one-point is very complicated since the high mass loss rate donor’s wind and one-point stream must be existing in the vicinity of one-point simultaneously. This situation maybe resolved when we suppose that the central source in an accretion disk will influence on the donor’s atmosphere structure in the vicinity of  one-point and in turn will be result in the break of wind in the vicinity of one-point. This finally will be means that one-point stream will be existing in one-point without a wind and it, flowing in the accretor’s Roche lobe, will be result in an accretion disk forma- tion. Here one problem is arising: what is the configuration of wind in the extended vicinity of one-point  and from what the parameters this configuration is depending and haw this configuration will be results to the disk structure change. We good understand that this situation is arising in the case of microquasars only and we try to resolve this problem in the present paper.

scholarly journals Hybrid Accretion-Disks in AGN and the AGN Contribution to the XRB

1994 ◽  
Vol 159 ◽  
pp. 491-491
Author(s):  
Amri Wandel
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Power Law ◽  
Accretion Rate ◽  
Bremsstrahlung Spectrum ◽  
Spectral Evolution ◽  
X Ray ◽  
X Ray Background ◽  
Inner Region ◽  
Two Temperature

The hybrid accretion-disk (HAD) model links the two characteristic components of AGN spectra – the UV bump and the X-ray power-law – in the framework of one physical model. The radially stratified hybrid disk is a self consistent combination of a thin, cool accretion disk at large radii, with an inner hot two-temperature disk. Its spectrum consists of three components, corresponding to the three radial disk regions: a blackbody thermal spectrum from the outer cool disk, a Comptonized soft photon power-law spectrum from the intermediate region, and a thermal Comptonized bremsstrahlung spectrum from the inner region. The dependence of the hybrid disk spectrum on the accretion rate and on other parameters is discussed and applied to AGN spectral evolution, and in particular to explaining the cosmic X-ray background by AGN.

scholarly journals The warm-up phase in massive star-forming cores around RCW 120

2021 ◽  
Vol 503 (1) ◽  
pp. 633-642
Author(s):  
M S Kirsanova ◽  
S V Salii ◽  
S V Kalenskii ◽  
D S Wiebe ◽  
A M Sobolev ◽  
...  
Keyword(s):  
High Mass ◽  
Physical Parameters ◽  
Evolutionary Stage ◽  
Gas Temperature ◽  
Warm Up ◽  
Molecular Emission ◽  
Star Forming ◽  
Hot Gas ◽  
H Ii Region ◽  
In The Beginning

ABSTRACT We study molecular emission in a massive condensation at the border of the H ii region RCW 120, paying particular attention to the Core 1 and 2 objects, the most massive fragments of the condensation found previously by ALMA. The latter fragment was previously suggested to host a high-mass analogue of Class 0 young stellar object. We present spectra of molecular emission in the 1 mm range made with the APEX telescope. We detect CH3OH and C34S lines in Cores 1 and 2. The CH3CN series and the SO2 lines are only found in Core 2. We estimate gas physical parameters using methanol lines and obtain gas temperature less than 100 K in both regions. Molecular hydrogen number density in Core 2 is in the range of 105−107 cm−3 and is more uncertain in Core 1. However, the detection of the CH3CN lines corresponding to highly excited transitions (Eu &gt; 400 K) in Core 2 indicates that the region contains hot gas, while the abundances of CH3OH, CS, SO2, and CH3CN are quite low for a hot core stage. We propose that Core 2 is in the warm-up phase prior to the establishing of the hot gas chemistry. We suggest that Core 2 is in the beginning of the hot core stage. There are no detected CH3CN lines in Core 1; therefore, it might be on an even less evolved evolutionary stage.

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