Position‐Velocity Diagrams for the Maser Emission Coming from a Keplerian Ring

Uscanga, L.; Cantó, J.; Raga, A. C.

doi:10.1086/518640

Cited by 3 publications

(4 citation statements)

References 19 publications

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“…The linear position-velocity diagram in Figure 5 may be explained by an edge-on Keplerian rotating ring (e.g., Uscanga et al 2007), despite the nearly face-on geometry of the jet as shown in Motogi et al (2016). Such an apparently misaligned geometry might be possible, if the jet significantly bends within 100 au from the launching point.…”

Section: Origin Of the Velocity Gradientmentioning

confidence: 96%

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

Motogi

Hirota

Saito

et al. 2017

ApJ

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We report on interferometric observations of a face-on accretion system around the High-Mass young stellar object, G353.273+0.641. The innermost accretion system of 100 au radius was resolved in a 45 GHz continuum image taken with the Jansky-Very Large Array. Our spectral energy distribution analysis indicated that the continuum could be explained by optically thick dust emission. The total mass of the dusty system is ∼ 0.2 M ⊙ at minimum and up to a few M ⊙ depending on the dust parameters. 6.7 GHz CH 3 OH masers associated with the same system were also observed with the Australia Telescope Compact Array. The masers showed a spiral-like, non-axisymmetric distribution with a systematic velocity gradient. The line-of-sight velocity field is explained by an infall motion along a parabolic streamline that falls onto the equatorial plane of the face-on system. The streamline is quasi-radial and reaches the equatorial plane at a radius of 16 au. This is clearly smaller than that of typical accretion disks in High-Mass star formation, indicating that the initial angular momentum was very small, or the CH 3 OH masers selectively trace accreting material that has small angular momentum. In the former case, the initial specific angular momentum is estimated to be 8 × 10 20 (M * /10 M ⊙ ) 0.5 cm 2 s −1 , or a significant fraction of the initial angular momentum was removed outside of 100 au. The physical origin of such a streamline is still an open question and will be constrained by the higher-resolution (∼ 10 mas) thermal continuum and line observations with ALMA long baselines.

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Section: Origin Of the Velocity Gradientmentioning

confidence: 96%

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

Motogi

Hirota

Saito

et al. 2017

ApJ

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“…In particular, locating the position of emitters precisely is a critical point (e.g. Uscanga et al 2007). In order to check whether the method is "robust" enough to infer some reliable information about masses, we generated a sample of N points {̟ i ,μ i }, obeying exactly Eq.…”

Section: Uncertainties and Data Dispersionmentioning

confidence: 99%

AGN disks and black holes on the weighting scales

Huré¹,

Hersant²,

Surville³

et al. 2011

A&A

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We exploit our formula for the gravitational potential of finite size, power-law disks to derive a general expression linking the mass of the black hole in active galactic nuclei (AGN), the mass of the surrounding disk, its surface density profile (through the power index s), and the differential rotation law. We find that the global rotation curve v(R) of the disk in centrifugal balance does not obey a power law of the cylindrical radius R (except in the confusing case s = −2 that mimics a Keplerian motion), and discuss the local velocity index. This formula can help to understand how, from position-velocity diagrams, mass is shared between the disk and the black hole. To this purpose, we checked the idea by generating a sample of synthetic data with different levels of Gaussian noise, added in radius. It turns out that, when observations are spread over a large radial domain and exhibit low dispersion (standard deviation σ 10% typically), the disk properties (mass and s-parameter) and black hole mass can be deduced from a non linear fit of kinematic data plotted on a (R, Rv 2 )-diagram. For σ 10%, masses are estimated fairly well from a linear regression (corresponding to the zeroth-order treatment of the formula), but the power index s is no longer accessible. We have applied the model to 7 AGN disks whose rotation has already been probed through water maser emission. For NGC 3393 and UGC 3789, the masses seem well constrained through the linear approach. For IC 1481, the power-law exponent s can even be deduced. Because the model is scale-free, it applies to any kind of star/disk system. Extension to disks around young stars showing deviation from Keplerian motion is thus straightforward.

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“…We subtracted the ring systemic velocity of 476 km s −1 from the observed LSR velocity of the maser spots in order to compare the observed PV diagram with the modelled one. The positions and velocities are in units of the outer radius of the ring (8 mas) and the rotation velocity at the outer edge of the ring (770 km s −1 ), respectively (Uscanga et al 2007).…”

Section: Model and Resultsmentioning

confidence: 99%

“…The systemic masers lie within a narrow range of radii, on the near side inner edge of the ring, while the high-velocity masers are located near the ring diameter. Previously, Watson & Wallin (1994) showed that the maser emission from a rapidly rotating, thin Keplerian ring viewed edge-on can reproduce the general features of the observed 22 GHz radiation of this galaxy. However, their assumption of a uniform absorption coefficient within the amplifying ring results in a PV diagram for the most intense masers that is qualitatively different from the observed one.…”

Section: Introductionmentioning

confidence: 90%

PV diagrams for the maser emission from a Keplerian ring

Uscanga¹,

Cantó

Raga

2007

Proc. IAU

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Abstract. We study the maser emission arising from a thin, planar, gaseous ring in Keplerian rotation around a central mass when it is observed edge-on. Assuming that the absorption coefficient within the amplifying ring is a decreasing function of distance from the central mass (i.e., κ = κ 0 r −q ), we calculated position-velocity (PV) diagrams for the most intense maser features using different values of the exponent q. We found that, depending on the value of q, these diagrams can be qualitatively different.

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Position‐Velocity Diagrams for the Maser Emission Coming from a Keplerian Ring

Cited by 3 publications

References 19 publications

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

AGN disks and black holes on the weighting scales

PV diagrams for the maser emission from a Keplerian ring

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