Lupus disks with faint CO isotopologues: low gas/dust or large carbon depletion?

Abstract

An era has started in which gas and dust can be observed independently in protoplanetary disks, thanks to the recent surveys with ALMA. The first near-complete high-resolution disk survey in both dust and gas in a single star-forming region has been carried out in Lupus, finding surprisingly low gas/dust ratios. The goal of this work is to fully exploit CO isotopologues observations in Lupus, comparing them with physical-chemical model results, in order to obtain gas masses for a large number of disks. We have employed physical-chemical models to analyze continuum and CO isotopologues observations of Lupus disks, including isotope-selective processes and freeze-out. Employing also the ALMA 13CO-only detections, disk gas masses have been calculated for a total of 34 sources, expanding the sample of 10 disks studied by Ansdell et al. (2016), where also C18O was detected. We confirm that overall gas-masses are very low, often smaller than 1 $M_{\mathrm{J}}$, if volatile carbon is not depleted. Accordingly, global gas/dust ratios predominantly between 1 and 10. Low CO-based gas masses and gas/dust ratios may indicate rapid loss of gas, or alternatively chemical evolution, e.g. via sequestering of carbon from CO to more complex molecules, or carbon locked up in larger bodies. Current ALMA observations cannot distinguish between these two hypotheses. We have simulated both scenarios, but chemical model results do not allow us to rule out one of the two. Assuming that all Lupus disks have evolved mainly due to viscous processes over the past few Myr, the observed correlation between the current mass accretion rate and dust mass found by Manara et al. (2016) implies a constant gas-to-dust ratio, which is close to 100 based on the observed $M_{\mathrm{disk}}/{\dot{M}}_{\mathrm{acc}}$ ratio. This in turn points to a scenario in which carbon depletion is responsible for the low CO isotopologue line luminosities.

11 pages, 9 figures, A&A accepted

References in corpus (13)

• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• X-Shooter spectroscopy of young stellar objects in Lupus: Accretion properties of class II and transitional objects
• A Steeper than Linear Disk Mass-Stellar Mass Scaling Relation
• Protoplanetary disk masses from CO isotopologues line emission
• Spitzer observations of the Orion OB1 association: disk census in the low mass stars
• Setting the volatile composition of (exo)planet-building material. Does chemical evolution in disk midplanes matter?
• Gas disks to gas giants: Simulating the birth of planetary systems
• Exploring the Origins of Carbon in Terrestrial Worlds
• The Nature of Transition Circumstellar Disks II. Southern Molecular Clouds
• The complex chemistry of outflow cavity walls exposed: the case of low-mass protostars
• Effects of accretion flow on the chemical structure in the inner regions of protoplanetary disks
• A Ring of C2H in the Molecular Disk Orbiting TW Hya
• Identification of new transitional disk candidates in Lupus with Herschel

Cited by in corpus (64)

• On the diversity and statistical properties of protostellar discs
• The Disk Substructures at High Angular Resolution Project (DSHARP): III. Spiral Structures in the Millimeter Continuum of the Elias 27, IM Lup, and WaOph 6 Disks
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• Different dust and gas radial extents in protoplanetary disks: consistent models of grain growth and CO emission
• CO and dust properties in the TW Hya disk from high-resolution ALMA observations
• CO Depletion in Protoplanetary Disks: A Unified Picture Combining Physical Sequestration and Chemical Processing
• Planet-forming material in a protoplanetary disc: the interplay between chemical evolution and pebble drift
• An ALMA Survey of CO isotopologue emission from Protoplanetary Disks in Chamaeleon I
• Measurement of Circumstellar Disk Sizes in the Upper Scorpius OB Association with ALMA
• A survey of C2H, HCN, and C18O in protoplanetary disks
• The efficiency of dust trapping in ringed proto-planetary discs
• HD far infrared emission as a measure of protoplanetary disk mass
• CN rings in full protoplanetary disks around young stars as probes of disk structure
• Probing the Protosolar Disk Using Dust Filtering at Gaps in the Early Solar System
• Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud
• New Constraints From Dust Lines On The Surface Densities Of Protoplanetary Disks
• A dust and gas cavity in the disc around CQ Tau revealed by ALMA
• The TW Hya Rosetta Stone Project III: Resolving the Gaseous Thermal Profile of the Disk
• On the secular evolution of the ratio between gas and dust radii in protoplanetary discs
• An unbiased ALMA spectral survey of the LkCa 15 and MWC 480 protoplanetary disks
• Dynamical mass measurements of two protoplanetary discs
• A dusty origin for the correlation between protoplanetary disc accretion rates and dust masses
• 13C17O suggests gravitational instability in the HL Tau disc
• ALMA Detection of Extended Millimeter Halos in the HD 32297 and HD 61005 Debris Disks
• Carbon depletion observed inside T Tauri inner rims: Formation of icy, kilometer size planetesimals by 1 Myr
• A novel way of measuring the gas disk mass of protoplanetary disks using N2H+ and C18O
• Gas mass tracers in protoplanetary disks: CO is still the best
• Observing Carbon & Oxygen Carriers in Protoplanetary Disks at Mid-infrared Wavelengths
• Detectability of embedded protoplanets from hydrodynamical simulations
• ALMA study of the HD 100453 AB system and the tidal interaction of the companion with the disk
• Large-scale CO spiral arms and complex kinematics associated with the T Tauri star RU Lup
• The ODYSSEUS Survey. Motivation and First Results: Accretion, Ejection, and Disk Irradiation of CVSO 109
• Accreting Transition Discs with large cavities created by X-ray photoevaporation in C and O depleted discs
• High Precision Dynamical Masses of Pre-Main Sequence Stars with ALMA and Gaia
• Chemical Feedbacks of Pebble Growth: Impacts on CO depletion and C/O ratios
• Solving grain size inconsistency between ALMA polarization and VLA continuum in the Ophiuchus IRS 48 protoplanetary disk
• Radiation-Hydrodynamical Models of X-ray Photoevaporation in Carbon Depleted Circumstellar Discs
• Destruction of refractory carbon grains drives the final stage of proto-planetary disk chemistry
• Tracing pebble drift and trapping using radial carbon depletion profiles in protoplanetary disks
• Constraining the radial drift of millimeter-sized grains in the protoplanetary disks in Lupus
• New Constraints on Protoplanetary Disk Gas Masses in Lupus
• The ALMA view of MP Mus (PDS 66): a protoplanetary disk with no visible gaps down to 4 au scales
• The coexistence of the streaming instability and the vertical shear instability in protoplanetary disks: Planetesimal formation thresholds explored in two-dimensional global models
• The dry and carbon poor inner disk of TW Hya: evidence for a massive icy dust trap
• Asymmetric mid-plane gas in ALMA images of HD~100546
• If you like C/O variations, you should have put a ring on it
• The nitrogen carrier in protoplanetary disks
• Resolved molecular line observations reveal an inherited molecular layer in the young disk around TMC1A
• Measuring elemental abundance ratios in protoplanetary disks at millimeter wavelengths
• Discovery of Line Pressure Broadening and Direct Constraint on Gas Surface Density in a Protoplanetary Disk
• Different degrees of nitrogen and carbon depletion in the warm molecular layers of protoplanetary disks
• Exploring HNC and HCN line emission as probes of the protoplanetary disk temperature
• Vertically extended and asymmetric CN emission in the Elias 2-27 protoplanetary disk
• ALMA Observations of Young Eruptive Stars: continuum disk sizes and molecular outflows
• Dust Accumulation near the Magnetospheric Truncation of Protoplanetary Discs around T Tauri Stars
• H${}_2$O distribution in the disc of HD 100546 and HD 163296: the role of dust dynamics and planet--disc interaction
• Cosmic-ray ionization rate in protoplanetary disks with sheared magnetic fields
• Modeling the Protoplanetary Disks of Two Brown Dwarfs in the Taurus Molecular Cloud
• Testing protoplanetary disc evolution with CO fluxes. A proof of concept in Lupus and Upper Sco
• The formation of CO${}_2$ through consumption of gas-phase CO on vacuum-UV irradiated water ice
• Dust entrainment in photoevaporative winds: Synthetic observations of transition disks
• An Incipient Debris Disk in the Chamaeleon I Cloud
• A CO-to-H${}_2$ ratio of $\approx 10^{-5}$ towards the Herbig Ae star HK Ori
• Planet formation in intermediate-separation binary systems