scholarly journals Proto-planetary disks with CARMA: sub-arsecond observations at millimeter wavelengths

2009 ◽  
Vol 5 (H15) ◽  
pp. 738-738
Author(s):  
Isella Andrea ◽  
John M. Carpenter ◽  
Laura Perez ◽  
Anneila I. Sargent
Keyword(s):  
Surface Density ◽  
Angular Resolution ◽  
Spatial Scales ◽  
Radial Profile ◽  
Continuum Emission ◽  
Disk Radius ◽  
Orbital Radius ◽  
Disk Structure ◽  
Millimeter Wavelengths ◽  
Radial Profiles

Using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) we observed several proto-planetary disks in the dust continuum emission at 1.3 and 2.8 mm (Isella et al. 2009a, 2009b). The observations have angular resolution between 0.15 and 0.7 arcsecond, corresponding to spatial scales spanning from about the orbit of Saturn up to about the orbital radius of Pluto. The observed disks are characterized by a variety of radial profiles for the dust density. We observe inner disk clearing as well as smooth density profiles, suggesting that disks may form, or evolve, in different ways. Despite that, we find that the characteristic disk radius is correlated with the stellar age increasing from 20 AU to 100 AU over about 5 Myr. Interpreting our results in terms of the temporal evolution of a viscous α-disk, we estimate that (i) at the beginning of the disk evolution about 60% of the circumstellar material was located inside radii of 25-40 AU, (ii) that disks formed with masses from 0.05 to 0.4 solar masses and (iii) that the viscous timescale at the disk initial radius is about 0.1-0.3 Myr. Viscous disk models tightly link the surface density Σ(R) with the radial profile of the disk viscosity ν(R)∝ Rγ. We find values of γ ranging from -0.8 to 0.8, suggesting that the viscosity dependence on the orbital radius can be very different in the observed disks. We demonstrate that the similarity solution for the surface density for γ < 0 can explain the properties of some “transitional” disks without requiring discontinuities in the disk surface density. In the case of LkCa 15, a smooth distribution of material from few stellar radii to about 240 AU can produce both the observed SED and the spatially resolved continuum emission at millimeter wavelengths. For two sources, RY Tau and DG Tau, we observed the dust emission with a resolution as high as 0.15 arcsecond, which corresponds to a spatial scale of 20 AU at the distance of the two stars. The achieved angular resolution is a factor 2 higher than any existing observation of circumstellar disks at the same wavelengths and enable us to investigate the disk structure with unprecedent details. In particular, we present a first attempt to derive the radial profile of the slope of the dust opacity β. We find mean values of β of 0.5 and 0.7 for DG Tau and RY Tau respectively and we exclude that β may vary by more than ±0.4 between 20-70 AU. This implies that the circumstellar dust has a maximum grain size between 10 μm and few centimeters.

scholarly journals A 45 AU radius source around L1551-IRS 5: a possible accretion disk

1991 ◽  
Vol 147 ◽  
pp. 361-372
Author(s):  
J. Keene ◽  
C. R. Masson
Keyword(s):  
Accretion Disk ◽  
Optical Depth ◽  
Column Density ◽  
Angular Resolution ◽  
Continuum Emission ◽  
Millimeter Wavelengths ◽  
High Column ◽  
Rule Out ◽  
The Continuum

Our interferometric and single-dish observations of the continuum emission from L1551-IRS 5 show that, at millimeter wavelengths, there are two distinct components to the source, an envelope with a radius ≥ 2000 AU, and a compact core with a radius ≤ 64 AU. The compact core has a large optical depth, indicating a high column density (∼ 1000 g cm—2). By modeling the temperature in the region of the compact core, we show that its size must lie in the range 45 ± 20 AU. The compact core is most plausibly identified with an accretion, or preplanetary, disk around the star, although the present observations do not have sufficient angular resolution to rule out other structures.

scholarly journals Extreme fragmentation and complex kinematics at the center of the L1287 cloud

2019 ◽  
Vol 621 ◽  
pp. A140 ◽  
Author(s):  
Carmen Juárez ◽  
Hauyu Baobab Liu ◽  
Josep M. Girart ◽  
Aina Palau ◽  
Gemma Busquet ◽  
...  
Keyword(s):  
Velocity Gradient ◽  
Angular Resolution ◽  
Spatial Scales ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Dense Gas ◽  
Continuum Image ◽  
Velocity Gradients ◽  
Low Mass

Aims. The filamentary ~10-pc-scale infrared dark cloud L1287 located at a parallax distance of ~929 pc is actively forming a dense cluster of low-mass young stellar objects (YSOs) at its inner ~0.1 pc region. To help understand the origin of this low-mass YSO cluster, the present work aims at resolving the gas structures and kinematics with high angular resolution. Methods. We performed ~1′′ angular resolution (~930 AU) observations at ~1.3 mm wavelengths using the Submillimeter Array (SMA), which simultaneously cover the dust continuum emission and various molecular line tracers for dense gas, warm gas, shocks, and outflows. Results. From a 1.3-mm continuum image with a resolution of ~2′′ we identified six dense cores, namely SMA1-6. Their gas masses are in the range of ~0.4–4 M⊙. From a 1.3-mm continuum image with a resolution of ~1′′, we find a high fragmentation level, with 14 compact millimeter sources within 0.1 pc: SMA3 contains at least nine internal condensations; SMA5 and SMA6 are also resolved with two internal condensations. Intriguingly, one condensation in SMA3 and another in SMA5 appear associated with the known accretion outburst YSOs RNO 1C and RNO 1B. The dense gas tracer DCN (3–2) well traces the dust continuum emission and shows a clear velocity gradient along the NW-SE direction centered at SMA3. There is another velocity gradient with opposite direction around the most luminous YSO, IRAS 00338 + 6312. Conclusions. The fragmentation within 0.1 pc in L1287 is very high compared to other regions at the same spatial scales. The incoherent motions of dense gas flows are sometimes interpreted by being influenced by (proto)stellar feedback (e.g., outflows), which is not yet ruled out in this particular target source. On the other hand, the velocities (with respect to the systemic velocity) traced by DCN are small, and the directions of the velocity gradients traced by DCN are approximately perpendicular to those of the dominant CO outflow(s). Therefore, we alternatively hypothesize that the velocity gradients revealed by DCN trace the convergence from the ≳0.1 pc scales infalling motion towards the rotational motions around the more compact (~0.02 pc) sources. This global molecular gas converging flow may feed the formation of the dense low-mass YSO cluster. Finally, we also found that IRAS 00338 + 6312 is the most likely powering source of the dominant CO outflow. A compact blue-shifted outflow from RNO 1C is also identified.

scholarly journals Non-Keplerian spirals, a gas-pressure dust trap, and an eccentric gas cavity in the circumbinary disc around HD 142527

2021 ◽  
Vol 504 (1) ◽  
pp. 782-791
Author(s):  
H Garg ◽  
C Pinte ◽  
V Christiaens ◽  
D J Price ◽  
J S Lazendic ◽  
...  
Keyword(s):  
Surface Density ◽  
Angular Resolution ◽  
Stokes Number ◽  
Continuum Emission ◽  
Vertical Temperature ◽  
Dust Trap ◽  
Density Peaks ◽  
Density Maps ◽  
Gas Cavity ◽  
Spiral Structures

ABSTRACT We present ALMA observations of the 12CO, 13CO, C18O J = 2-1 transitions and the 1.3 mm continuum emission for the circumbinary disc around HD 142527, at an angular resolution of ≈ 0${_{.}^{\prime\prime}}$3. We observe multiple spiral structures in intensity, velocity, and velocity dispersion for the 12CO and 13CO gas tracers. A newly detected 12CO spiral originates from the dust horseshoe, and is rotating at super-Keplerian velocity or vertically ascending, whilst the interspiral gas is rotating at sub-Keplerian velocities. This new spiral possibly connects to a previously identified spiral, thus spanning &gt;360°. A spatial offset of  30 au is observed between the 12CO and 13CO spirals, to which we hypothesize that the gas layers are propagating at different speeds (surfing) due to a non-zero vertical temperature gradient. Leveraging the varying optical depths between the CO isotopologues, we reconstruct temperature and column density maps of the outer disc. Gas surface density peaks at r ≈ 180 au, coincident with the peak of continuum emission. Here, the dust grains have a Stokes number of ≈ 1, confirming radial and azimuthal trapping in the horseshoe. We measure a cavity radius at half-maximum surface density of ≈ 100 au, and a cavity eccentricity between 0.3 and 0.45.

scholarly journals Fragmentation and disk formation during high-mass star formation

2018 ◽  
Vol 617 ◽  
pp. A100 ◽  
Author(s):  
H. Beuther ◽  
J. C. Mottram ◽  
A. Ahmadi ◽  
F. Bosco ◽  
H. Linz ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Line ◽  
Angular Resolution ◽  
Spatial Scales ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
Star Forming ◽  
Disk Formation ◽  
Star Forming Regions

Context. High-mass stars form in clusters, but neither the early fragmentation processes nor the detailed physical processes leading to the most massive stars are well understood. Aims. We aim to understand the fragmentation, as well as the disk formation, outflow generation, and chemical processes during high-mass star formation on spatial scales of individual cores. Methods. Using the IRAM Northern Extended Millimeter Array (NOEMA) in combination with the 30 m telescope, we have observed in the IRAM large program CORE the 1.37 mm continuum and spectral line emission at high angular resolution (~0.4″) for a sample of 20 well-known high-mass star-forming regions with distances below 5.5 kpc and luminosities larger than 104 L⊙. Results. We present the overall survey scope, the selected sample, the observational setup, and the main goals of CORE. Scientifically, we concentrated on the mm continuum emission on scales on the order of 1000 AU. We detect strong mm continuum emission from all regions, mostly due to the emission from cold dust. The fragmentation properties of the sample are diverse. We see extremes where some regions are dominated by a single high-mass core whereas others fragment into as many as 20 cores. A minimum-spanning-tree analysis finds fragmentation at scales on the order of the thermal Jeans length or smaller suggesting that turbulent fragmentation is less important than thermal gravitational fragmentation. The diversity of highly fragmented vs. singular regions can be explained by varying initial density structures and/or different initial magnetic field strengths. Conclusions. A large sample of high-mass star-forming regions at high spatial resolution allows us to study the fragmentation properties of young cluster-forming regions. The smallest observed separations between cores are found around the angular resolution limit which indicates that further fragmentation likely takes place on even smaller spatial scales. The CORE project with its numerous spectral line detections will address a diverse set of important physical and chemical questions in the field of high-mass star formation.

scholarly journals A 45 AU radius source around L1551-IRS 5: a possible accretion disk

1991 ◽  
Vol 147 ◽  
pp. 361-372
Author(s):  
J. Keene ◽  
C. R. Masson
Keyword(s):  
Accretion Disk ◽  
Optical Depth ◽  
Column Density ◽  
Angular Resolution ◽  
Continuum Emission ◽  
Millimeter Wavelengths ◽  
High Column ◽  
Rule Out ◽  
The Continuum

Our interferometric and single-dish observations of the continuum emission from L1551-IRS 5 show that, at millimeter wavelengths, there are two distinct components to the source, an envelope with a radius ≥ 2000 AU, and a compact core with a radius ≤ 64 AU. The compact core has a large optical depth, indicating a high column density (∼ 1000 g cm—2). By modeling the temperature in the region of the compact core, we show that its size must lie in the range 45 ± 20 AU. The compact core is most plausibly identified with an accretion, or preplanetary, disk around the star, although the present observations do not have sufficient angular resolution to rule out other structures.

scholarly journals Probing the protoplanetary disk gas surface density distribution with 13CO emission

2018 ◽  
Vol 619 ◽  
pp. A113 ◽  
Author(s):  
A. Miotello ◽  
S. Facchini ◽  
E. F. van Dishoeck ◽  
S. Bruderer
Keyword(s):  
Density Distribution ◽  
Power Law ◽  
Surface Density ◽  
Disk Surface ◽  
Input Power ◽  
Disk Radius ◽  
Spatially Resolved ◽  
Radial Profiles ◽  
Power Law Index ◽  
Freeze Out

Context. How protoplanetary disks evolve is still an unsolved problem where different processes may be involved. Depending on the process, the disk gas surface density distribution Σgas may be very different and this could have diverse implications for planet formation. Together with the total disk mass, it is key to constrain Σgas as function of disk radius R from observational measurements. Aims. In this work we investigate whether spatially resolved observations of rarer CO isotopologues, such as 13CO, may be good tracers of the gas surface density distribution in disks. Methods. Physical-chemical disk models with different input Σgas(R) were run, taking into account CO freeze-out and isotope-selective photodissociation. The input disk surface density profiles were compared with the simulated 13CO intensity radial profiles to check whether and where the two follow each other. Results. For each combination of disk parameters, there is always an intermediate region in the disk where the slope of the 13CO radial emission profile and Σgas(R) coincide. In the inner part of the disk, the line radial profile underestimates Σgas, as 13CO emission becomes optically thick. The same happens at large radii where the column densities become too low and 13CO is not able to efficiently self-shield. Moreover, the disk becomes too cold and a considerable fraction of 13CO is frozen out, thus it does not contribute to the line emission. If the gas surface density profile is a simple power-law of the radius, the input power-law index can be retrieved within a ~20% uncertainty if one choses the proper radial range. If instead Σgas(R) follows the self-similar solution for a viscously evolving disk, retrieving the input power-law index becomes challenging, in particular for small disks. Nevertheless, we find that the power-law index γ can be in any case reliably fitted at a given line intensity contour around 6 K km s−1, and this produces a practical method to constrain the slope of Σgas(R). Application of such a method is shown in the case study of the TW Hya disk. Conclusions. Spatially resolved 13CO line radial profiles are promising to probe the disk surface density distribution, as they directly trace Σgas(R) profile at radii well resolvable by ALMA. There, chemical processes like freeze-out and isotope-selective photodissociation do not affect the emission, and, assuming that the volatile carbon does not change with radius, no chemical model is needed when interpreting the observations.

scholarly journals High gas-to-dust size ratio indicating efficient radial drift in the mm-faint CX Tauri disk

2019 ◽  
Vol 626 ◽  
pp. L2 ◽  
Author(s):  
S. Facchini ◽  
E. F. van Dishoeck ◽  
C. F. Manara ◽  
M. Tazzari ◽  
L. Maud ◽  
...  
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Spectral Energy Distribution ◽  
Theoretical Models ◽  
Intensity Profile ◽  
Continuum Emission ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Sharp Drop ◽  
Large Program

The large majority of protoplanetary disks have very compact continuum emission (≲15 AU) at millimeter wavelengths. However, high angular resolution observations that resolve these small disks are still lacking, due to their intrinsically fainter emission compared with large bright disks. In this Letter we present 1.3 mm ALMA data of the faint disk (∼10 mJy) orbiting the TTauri star CX Tau at a resolution of ∼40 mas, ∼5 AU in diameter. The millimeter dust disk is compact, with a 68% enclosing flux radius of 14 AU, and the intensity profile exhibits a sharp drop between 10 and 20 AU, and a shallow tail between 20 and 40 AU. No clear signatures of substructure in the dust continuum are observed, down to the same sensitivity level of the DSHARP large program. However, the angular resolution does not allow us to detect substructures on the scale of the disk aspect ratio in the inner regions. The radial intensity profile closely resembles the inner regions of more extended disks imaged at the same resolution in DSHARP, but with no rings present in the outer disk. No inner cavity is detected, even though the disk has been classified as a transition disk from the spectral energy distribution in the near-infrared. The emission of 12CO is much more extended, with a 68% enclosing flux radius of 75 AU. The large difference of the millimeter dust and gas extents (> 5) strongly points to radial drift, and closely matches the predictions of theoretical models.

scholarly journals The intracluster light as a tracer of the total matter density distribution: a view from simulations

2020 ◽  
Vol 494 (2) ◽  
pp. 1859-1864 ◽  
Author(s):  
Isaac Alonso Asensio ◽  
Claudio Dalla Vecchia ◽  
Yannick M Bahé ◽  
David J Barnes ◽  
Scott T Kay
Keyword(s):  
Mass Density ◽  
Radial Profile ◽  
Stellar Mass ◽  
Matter Density ◽  
Density Profiles ◽  
Radial Profiles ◽  
Intracluster Light ◽  
Baryonic Mass ◽  
Mass Density Profile ◽  
Total Matter

ABSTRACT By using deep observations of clusters of galaxies, it has been recently found that the projected stellar mass density closely follows the projected total (dark and baryonic) mass density within the innermost ∼140 kpc. In this work, we aim to test these observations using the Cluster-EAGLE simulations, comparing the projected densities inferred directly from the simulations. We compare the iso-density contours using the procedure of Montes & Trujillo, and find that the shape of the stellar mass distribution follows that of the total matter even more closely than observed, although their radial profiles differ substantially. The ratio between stellar and total matter density profiles in circular apertures shows a slope close to −1, with a small dependence on the cluster’s total mass. We propose an indirect method to calculate the halo mass and mass density profile from the radial profile of the intracluster stellar mass density.

scholarly journals Radio Continuum Observations of the Barred Galaxy NGC 4314

1987 ◽  
Vol 115 ◽  
pp. 626-627 ◽  
Author(s):  
J.A. García-Barreto ◽  
P. Pişmiş
Keyword(s):  
Angular Resolution ◽  
Radio Continuum ◽  
Continuum Emission ◽  
No Emission ◽  
The Galaxy ◽  
Thermal Origin ◽  
Linearly Polarized ◽  
Barred Spiral Galaxy ◽  
Compact Sources ◽  
The Continuum

VLA observations have been made of the continuum emission at 20-cm from the barred spiral galaxy NGC 4314 with an angular resolution of 3.5 arcseconds that corresponds to a linear scale of approximately 156 pc at a distance to the galaxy. This resolution was sufficient to resolve the central region into several compact sources. The radiation is linearly polarized which may indicate a non-thermal origin. No emission was detected from the extended bar to a level of 130 Jy.

scholarly journals Spatially resolved signature of quenching in star-forming galaxies

2019 ◽  
Vol 490 (2) ◽  
pp. 2347-2366 ◽  
Author(s):  
Salvatore Quai ◽  
Lucia Pozzetti ◽  
Michele Moresco ◽  
Annalisa Citro ◽  
Andrea Cimatti ◽  
...  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Galaxy Evolution ◽  
Spatial Information ◽  
Formation Rate ◽  
Radial Profile ◽  
Control Sample ◽  
Star Forming ◽  
Radial Profiles ◽  
Two Samples

ABSTRACT Understanding when, how, and where star formation ceased (quenching) within galaxies is still a critical subject in galaxy evolution studies. Taking advantage of the new methodology developed by Quai et al. to select recently quenched galaxies, we explored the spatial information provided by the IFU data to get critical insights on this process. In particular, we analyse 10 SDSS-IV MaNGA galaxies that show regions with low [O iii]/H α compatible with a recent quenching of the star formation. We compare the properties of these 10 galaxies with those of a control sample of 8 MaNGA galaxies with ongoing star formation in the same stellar mass, redshift, and gas-phase metallicity range. The quenching regions found are located between 0.5 and 1.1 effective radii from the centre. This result is supported by the analysis of the average radial profile of the ionization parameter, which reaches a minimum at the same radii, while the one of the star-forming sample shows an almost flat trend. These quenching regions occupy a total area between ∼ 15 and 45 per cent of our galaxies. Moreover, the average radial profile of the star formation rate surface density of our sample is lower and flatter than that of the control sample, at any radii, suggesting a systematic suppression of the star formation in the inner part of our galaxies. Finally, the radial profiles of gas-phase metallicity of the two samples have a similar slope and normalization. Our results cannot be ascribed to a difference in the intrinsic properties of the analysed galaxies, suggesting a quenching scenario more complicated than a simple inside-out quenching.

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