scholarly journals Using HCO+ isotopologues as tracers of gas depletion in protoplanetary disk gaps

2020 ◽  
Vol 644 ◽  
pp. A4
Author(s):  
Grigorii V. Smirnov-Pinchukov ◽  
Dmitry A. Semenov ◽  
Vitaly V. Akimkin ◽  
Thomas Henning
Keyword(s):  
Line Emission ◽  
Physical Structure ◽  
Protoplanetary Disk ◽  
Line Ratio ◽  
X Rays ◽  
Disk Model ◽  
Moment Maps ◽  
Disk Structure ◽  
Molecular Abundances ◽  
Far Ultraviolet

Context. The widespread rings and gaps seen in the dust continuum in protoplanetary disks are sometimes accompanied by similar substructures seen in molecular line emission. One example is the outer gap at ~100 au in AS 209, which shows that the H13CO+ and C18O emission intensities decrease along with the continuum in the gap, while the DCO+ emission increases inside the gap. Aims. We aim to study the behavior of DCO+/H13CO+ and DCO+/HCO+ ratios in protoplanetary disk gaps assuming the two scenarios: (A) the gas depletion follows the dust depletion and (B) only the dust is depleted. Methods. We first modeled the physical disk structure using the thermo-chemical model ANDES. This 1+1D steady-state disk model calculates the thermal balance of gas and dust and includes the far ultraviolet, X-rays, cosmic rays, and other ionization sources together with the reduced chemical network for molecular coolants. Afterward, this physical structure was adopted for calculations of molecular abundances with the extended gas-grain chemical network with deuterium fractionation. Ideal synthetic spectra and 0th-moment maps were produced with the LIne Modeling Engine. Results. We are able to qualitatively reproduce the increase in the DCO+ intensity and the decrease in the H13CO+ and C18O intensities inside the disk gap, which is qualitatively similar to what is observed in the outer AS 209 gap. The corresponding disk model (A) assumes that both the gas and dust are depleted in the gap. The model (B) with the gas-rich gap, where only the dust is depleted, produces emission that is too bright in all HCO+ isotopologues and C18O. Conclusions. The DCO+/H13CO+ line ratio can be used to probe gas depletion in dust continuum gaps outside of the CO snow line. The DCO+/C18O line ratio shows a similar, albeit weaker, effect; however, these species can be observed simultaneously with a single (sub)mm interferometer setup.

scholarly journals The ALMA-PILS survey: 3D modeling of the envelope, disks and dust filament of IRAS 16293–2422

2018 ◽  
Vol 612 ◽  
pp. A72 ◽  
Author(s):  
S. K. Jacobsen ◽  
J. K. Jørgensen ◽  
M. H. D. van der Wiel ◽  
H. Calcutt ◽  
T. L. Bourke ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
3D Model ◽  
Line Emission ◽  
Protoplanetary Disk ◽  
Scale Height ◽  
High Angular Resolution ◽  
High Scale ◽  
Disk Model ◽  
Complex Morphology ◽  
Radiative Transfer Modeling

Context. The Class 0 protostellar binary IRAS 16293–2422 is an interesting target for (sub)millimeter observations due to, both, the rich chemistry toward the two main components of the binary and its complex morphology. Its proximity to Earth allows the study of its physical and chemical structure on solar system scales using high angular resolution observations. Such data reveal a complex morphology that cannot be accounted for in traditional, spherical 1D models of the envelope. Aims. The purpose of this paper is to study the environment of the two components of the binary through 3D radiative transfer modeling and to compare with data from the Atacama Large Millimeter/submillimeter Array. Such comparisons can be used to constrain the protoplanetary disk structures, the luminosities of the two components of the binary and the chemistry of simple species. Methods. We present 13CO, C17O and C18O J = 3–2 observations from the ALMA Protostellar Interferometric Line Survey (PILS), together with a qualitative study of the dust and gas density distribution of IRAS 16293–2422. A 3D dust and gas model including disks and a dust filament between the two protostars is constructed which qualitatively reproduces the dust continuum and gas line emission. Results. Radiative transfer modeling in our sampled parameter space suggests that, while the disk around source A could not be constrained, the disk around source B has to be vertically extended. This puffed-up structure can be obtained with both a protoplanetary disk model with an unexpectedly high scale-height and with the density solution from an infalling, rotating collapse. Combined constraints on our 3D model, from observed dust continuum and CO isotopologue emission between the sources, corroborate that source A should be at least six times more luminous than source B. We also demonstrate that the volume of high-temperature regions where complex organic molecules arise is sensitive to whether or not the total luminosity is in a single radiation source or distributed into two sources, affecting the interpretation of earlier chemical modeling efforts of the IRAS 16293–2422 hot corino which used a single-source approximation. Conclusions. Radiative transfer modeling of source A and B, with the density solution of an infalling, rotating collapse or a protoplanetary disk model, can match the constraints for the disk-like emission around source A and B from the observed dust continuum and CO isotopologue gas emission. If a protoplanetary disk model is used around source B, it has to have an unusually high scale-height in order to reach the dust continuum peak emission value, while fulfilling the other observational constraints. Our 3D model requires source A to be much more luminous than source B; LA ~ 18 L⊙ and LB ~ 3 L⊙.

scholarly journals First detections of H13CO+ and HC15N in the disk around HD 97048

2019 ◽  
Vol 629 ◽  
pp. A75 ◽  
Author(s):  
Alice S. Booth ◽  
Catherine Walsh ◽  
John D. Ilee
Keyword(s):  
Dust Emission ◽  
Line Emission ◽  
Abundance Ratio ◽  
Protoplanetary Disk ◽  
Temperature Structure ◽  
Exchange Reactions ◽  
Gas Kinematics ◽  
Spatially Resolved ◽  
Chemical Models ◽  
Disk Structure

Observations of different molecular lines in protoplanetary disks provide valuable information on the gas kinematics, as well as constraints on the radial density and temperature structure of the gas. With ALMA we have detected H13CO+ (J = 4–3) and HC15N (J = 4–3) in the HD 97048 protoplanetary disk for the first time. We compare these new detections to the ringed continuum mm-dust emission and the spatially resolved CO (J = 3–2) and HCO+ (J = 4–3) emission. The radial distributions of the H13CO+ and HC15N emission show hints of ringed sub-structure whereas, the optically thick tracers, CO and HCO+, do not. We calculate the HCO+/H13CO+ intensity ratio across the disk and find that it is radially constant (within our uncertainties). We use a physio-chemical parametric disk structure of the HD 97048 disk with an analytical prescription for the HCO+ abundance distribution to generate synthetic observations of the HCO+ and H13CO+ disk emission assuming LTE. The best by-eye fit models require radial variations in the HCO+/H13CO+ abundance ratio and an overall enhancement in H13CO+ relative to HCO+. This highlights the need to consider isotope selective chemistry and in particular low temperature carbon isotope exchange reactions. This also points to the presence of a reservoir of cold molecular gas in the outer disk (T ≲ 10 K, R ≳ 200 au). Chemical models are required to confirm that isotope-selective chemistry alone can explain the observations presented here. With these data, we cannot rule out that the known dust substructure in the HD 97048 disk is responsible for the observed trends in molecular line emission, and higher spatial resolution observations are required to fully explore the potential of optically thin tracers to probe planet-carved dust gaps. We also report non-detections of H13CO+ and HC15N in the HD 100546 protoplanetary disk.

scholarly journals Revisiting the case of R Monocerotis: Is CO removed at R < 20 au?

2018 ◽  
Vol 617 ◽  
pp. A31 ◽  
Author(s):  
T. Alonso-Albi ◽  
P. Riviere-Marichalar ◽  
A. Fuente ◽  
S. Pacheco-Vázquez ◽  
B. Montesinos ◽  
...  
Keyword(s):  
Spectral Type ◽  
Protoplanetary Disk ◽  
Emission Lines ◽  
Disk Model ◽  
Dispersal Mechanism ◽  
Disk Structure ◽  
Upper Limits ◽  
Intense Emission ◽  
Uv Photons ◽  
Continuum Data

Context. To our knowledge, R Mon is the only B0 star in which a gaseous Keplerian disk has been detected. However, there is some controversy about the spectral type of R Mon. Some authors propose that it could be a later B8e star, where disks are more common. Aims. Our goal is to re-evaluate the R Mon spectral type and characterize its protoplanetary disk. Methods. The spectral type of R Mon has been re-evaluated using the available continuum data and UVES emission lines. We used a power-law disk model to fit previous 12CO 1 →0 and 2 →1 interferometric observations and the PACS CO data to investigate the disk structure. Interferometric detections of 13CO J = 1 →0, HCO+ 1 →0, and CN 1 →0 lines using the IRAM Plateau de Bure Interferometer (PdBI) are presented. The HCN 1 →0 line was not detected. Results. Our analysis confirms that R Mon is a B0 star. The disk model compatible with the 12CO 1 →0 and 2 →1 interferometric observations falls short of predicting the observed fluxes of the 14 < Ju < 31 PACS lines; this is consistent with the scenario in which some contribution to these lines is coming from a warm envelope and/or UV-illuminated outflow walls. More interestingly, the upper limits to the fluxes of the Ju > 31 CO lines suggest the existence of a region empty of CO at R ≲ 20 au in the protoplanetary disk. The intense emission of the HCO+ and CN lines shows the strong influence of UV photons on gas chemistry. Conclusions. The observations gathered in this paper are consistent with the presence of a transition disk with a cavity of Rin ≳ 20 au around R Mon. This size is similar to the photoevaporation radius that supports the interpretation that UV photoevaporation is main disk dispersal mechanism in massive stars

scholarly journals Interpreting high spatial resolution line observations of planet-forming disks with gaps and rings: the case of HD 163296

2020 ◽  
Vol 642 ◽  
pp. A165
Author(s):  
Ch. Rab ◽  
I. Kamp ◽  
C. Dominik ◽  
C. Ginski ◽  
G. A. Muro-Arena ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Line Emission ◽  
High Angular Resolution ◽  
Back Side ◽  
Gas Temperature ◽  
Disk Model ◽  
Gas Density ◽  
The Impact ◽  
Gas Properties

Context. Spatially resolved continuum observations of planet-forming disks show prominent ring and gap structures in their dust distribution. However, the picture from gas observations is much less clear and constraints on the radial gas density structure (i.e. gas gaps) remain rare and uncertain. Aims. We want to investigate the importance of thermo-chemical processes for the interpretation of high-spatial-resolution gas observations of planet-forming disks and their impact on the derived gas properties. Methods. We applied the radiation thermo-chemical disk code PRODIMO (PROtoplanetary DIsk MOdel) to model the dust and gas disk of HD 163296 self-consistently, using the DSHARP (Disk Substructure at High Angular Resolution) gas and dust observations. With this model we investigated the impact of dust gaps and gas gaps on the observables and the derived gas properties, considering chemistry, and heating and cooling processes. Results. We find distinct peaks in the radial line intensity profiles of the CO line data of HD 163296 at the location of the dust gaps. Our model indicates that those peaks are not only a consequence of a gas temperature increase within the gaps but are mainly caused by the absorption of line emission from the back side of the disk by the dust rings. For two of the three prominent dust gaps in HD 163296, we find that thermo-chemical effects are negligible for deriving density gradients via measurements of the rotation velocity. However, for the gap with the highest dust depletion, the temperature gradient can be dominant and needs to be considered to derive accurate gas density profiles. Conclusions. Self-consistent gas and dust thermo-chemical modelling in combination with high-quality observations of multiple molecules are necessary to accurately derive gas gap depths and shapes. This is crucial to determine the origin of gaps and rings in planet-forming disks and to improve the mass estimates of forming planets if they are the cause of the gap.

scholarly journals Variability in X-ray line ratios in helium-like ions of massive stars: the wind-driven case

2019 ◽  
Vol 625 ◽  
pp. A86 ◽  
Author(s):  
R. Ignace ◽  
Z. Damrau ◽  
K. T. Hole
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Variable Mass ◽  
Line Ratio ◽  
High Spectral Resolution ◽  
X Rays ◽  
Wind Integration ◽  
X Ray ◽  
Wind Variability

Context. High spectral resolution and long exposure times are providing unprecedented levels of data quality of massive stars at X-ray wavelengths. Aims. A key diagnostic of the X-ray emitting plasma are the fir lines for He-like triplets. In particular, owing to radiative pumping effects, the forbidden-to-intercombination line luminosity ratio, R = f∕i, can be used to determine the proximity of the hot plasma to the UV-bright photospheres of massive stars. Moreover, the era of large observing programs additionally allows for investigation of line variability. Methods. This contribution is the second to explore how variability in the line ratio can provide new diagnostic information about distributed X-rays in a massive star wind. We focus on wind integration for total line luminosities, taking account of radiative pumping and stellar occultation. While the case of a variable stellar radiation field was explored in the first paper, the effects of wind variability are emphasized in this work. Results. We formulate an expression for the ratio of line luminosities f∕i that closely resembles the classic expression for the on-the-spot result. While there are many ways to drive variability in the line ratio, we use variable mass loss as an illustrative example for wind integration, particularly since this produces no variability for the on-the-spot case. The f∕i ratio can be significantly modulated owing to evolving wind properties. The extent of the variation depends on how the timescale for the wind flow compares to the timescale over which the line emissivities change. Conclusions. While a variety of factors can ellicit variable line ratios, a time-varying mass-loss rate serves to demonstrate the range of amplitude and phased-dependent behavior in f∕i line ratios. Importantly, we evaluate how variable mass loss might bias measures of f∕i. For observational exposures that are less than the timescale of variable mass loss, biased measures (relative to the time-averaged wind) can result; if exposures are long, the f∕i ratio is reflective of the time-averaged spherical wind.

scholarly journals Searching for kinematic evidence of Keplerian disks around Class 0 protostars with CALYPSO

2020 ◽  
Vol 635 ◽  
pp. A15 ◽  
Author(s):  
S. Maret ◽  
A. J. Maury ◽  
A. Belloche ◽  
M. Gaudel ◽  
Ph. André ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Angular Resolution ◽  
Line Emission ◽  
Protoplanetary Disks ◽  
High Angular Resolution ◽  
Moment Maps ◽  
Large Program ◽  
Jet Axis

The formation of protoplanetary disks is not well understood. To understand how and when these disks are formed, it is crucial to characterize the kinematics of the youngest protostars at a high angular resolution. Here we study a sample of 16 Class 0 protostars to measure their rotation profile at scales from 50 to 500 au and search for Keplerian rotation. We used high-angular-resolution line observations obtained with the Plateau de Bure Interferometer as part of the CALYPSO large program. From 13CO (J = 2−1), C18O (J = 2−1) and SO (Nj = 56−45) moment maps, we find that seven sources show rotation about the jet axis at a few hundred au scales: SerpS-MM18, L1448-C, L1448-NB, L1527, NGC 1333-IRAS 2A, NGC 1333-IRAS 4B, and SVS13-B. We analyzed the kinematics of these sources in the uv plane to derive the rotation profiles down to 50 au scales. We find evidence for Keplerian rotation in only two sources, L1527 and L1448-C. Overall, this suggests that Keplerian disks larger than 50 au are uncommon around Class 0 protostars. However, in some of the sources, the line emission could be optically thick and dominated by the envelope emission. Due to the optical thickness of these envelopes, some of the disks could have remained undetected in our observations.

Voyager Observations of Diffuse Far-Ultraviolet Continuum and Line Emission in Eridanus

1993 ◽  
Vol 419 ◽  
pp. 739 ◽  
Author(s):  
Jayant Murthy ◽  
M. Im ◽  
R. C. Henry ◽  
J. B. Holberg
Keyword(s):  
Line Emission ◽  
Ultraviolet Continuum ◽  
Far Ultraviolet

Possible detection of far-ultraviolet line emission from a hot galactic corona

1981 ◽  
Vol 249 ◽  
pp. L51 ◽  
Author(s):  
P. D. Feldman ◽  
W. H. Brune ◽  
R. C. Henry
Keyword(s):  
Line Emission ◽  
Far Ultraviolet

Detection of Far-Ultraviolet High-Excitation Line Emission and Lyman- beta Absorption in the Gravitational Lens Q0957+561

1993 ◽  
Vol 417 ◽  
pp. L57 ◽  
Author(s):  
A. G. Michalitsianos ◽  
J. Nichols-Bohlin ◽  
F. C. Bruhweiler ◽  
D. Kazanas ◽  
Y. Kondo ◽  
...  
Keyword(s):  
Line Emission ◽  
Gravitational Lens ◽  
High Excitation ◽  
Excitation Line ◽  
Far Ultraviolet

scholarly journals Accretion Disk Structure in SS Cygni

1987 ◽  
Vol 93 ◽  
pp. 351-364
Author(s):  
F.V. Hessman
Keyword(s):  
High Resolution ◽  
Phase Shift ◽  
Accretion Disk ◽  
Phase Stability ◽  
Large Scale ◽  
Large Fraction ◽  
Line Emission ◽  
Simple Explanation ◽  
Disk Structure ◽  
Magnetic Origin

AbstractHigh-resolution Coude observations of non-axisymmetric line emission -from the dwarf nova SS Cygni are presented. By subtracting the constant line component, the asymmetric line emission responsible for the observed phase shift between the absorption and emission line radial velocity curves can be isolated. The extra emission is a large fraction of the total line emission and extends to large velocities (~1500 km sec−1). The phase stability of the emission demands a large-scale structure which is fixed in the frame of the binary. A magnetic origin of the excitation cannot De ruled out but is implausible. A simple explanation is that the accretion stream from the companion star is able to spill over the sags of the disk, introducing emission at non-circular velocities and most likely disturbing the upper layers of the accretion disk.

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