Chemistry in disks I - Deep search for N${}_2$H${}^{+}$ in the protoplanetary disks around LkCa 15, MWC 480, and DM Tau

Abstract

Aims: To constrain the ionization fraction in protoplanetary disks, we present new high-sensitivity interferometric observations of N${}_2$H${}^{+}$ in three disks surrounding DM Tau, LkCa 15, and MWC 480. Methods: We used the IRAM PdBI array to observe the N${}_2$H${}^{+}$ J=1-0 line and applied a ${\chi }^2$-minimization technique to estimate corresponding column densities. These values are compared, together with HCO${}^{+}$ column densities, to results of a steady-state disk model with a vertical temperature gradient coupled to gas-grain chemistry. Results: We report two \ndhp detections for LkCa 15 and DM Tau at the $5\sigma$ level and an upper limit for MWC 480. The column density derived from the data for LkCa 15 is much lower than previously reported. The [N${}_2$H${}^{+}$/HCO${}^{+}$] ratio is on the order of 0.02--0.03. So far, HCO${}^{+}$ remains the most abundant observed molecular ion in disks. Conclusions: All the observed values generally agree with the modelled column densities of disks at an evolutionary stage of a few million years (within the uncertainty limits), but the radial distribution of the molecules is not reproduced well. The low inferred concentration of N${}_2$H${}^{+}$ in three disks around low-mass and intermediate-mass young stars implies that this ion is not a sensitive tracer of the overall disk ionization fraction.

arXiv comment10 pages, 6 figures

References in corpus (25)

• Accretion Disks Around Young Objects. II. Tests of Well-Mixed Models with Ism Dust
• Dynamical Masses of T Tauri Stars and Calibration of PMS Evolution
• Molecular ions in L1544. II. The ionization degree
• Organic molecules in protoplanetary disks around TTauri and HerbigAe stars
• Molecular Evolution in Collapsing Prestellar Cores III: Contraction of A Bonnor-Ebert Sphere
• Desorption rates and sticking coefficients for CO and N2 interstellar ices
• Imaging the Disk around TW Hya with the Submillimeter Array
• Molecular ions in L1544. I. Kinematics
• Submillimeter lines from circumstellar disks around pre-main sequence stars
• Resolving the inner dust disks surrounding LkCa 15 and MWC 480 at mm wavelengths
• Axi-symmetric models of ultraviolet radiative transfer with applications to circumstellar disk chemistry
• Comparative Chemistry of Diffuse Clouds II: CN, HCN, HNC, CH3CN & N2H+
• Reduction of chemical networks. II. Analysis of the fractional ionisation in protoplanetary discs
• A New Probe of the Planet-Forming Region in T Tauri Disks
• Continuum and CO/HCO+ Emission from the Disk Around the T Tauri Star LkCa 15
• Imaging chemical differentiation around the low-mass protostar L483-mm
• Gas-phase CO in protoplanetary disks: a challenge for turbulent mixing
• Estimation and reduction of the uncertainties in chemical models: Application to hot core chemistry
• Millimeter observations and modeling of the AB Aurigae system
• Interferometric Observations of Formaldehyde in the Protoplanetary Disk around LkCa15
• Deuterated H${}_3^{+}$ in proto-planetary disks
• Deuterated molecules in DM Tau: DCO+, but no HDO
• On the Influence of Uncertainties in Chemical Reaction Rates on Results of the Astrochemical Modelling
• Dynamical and chemical properties of the "starless" core L1014
• Line emission from circumstellar disks around A stars

Cited by in corpus (57)

• Protoplanetary Disks and Their Evolution
• A simple model for the evolution of the dust population in protoplanetary disks
• Our astrochemical heritage
• 2021 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• 2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• A dual-frequency sub-arcsecond study of proto-planetary disks at mm wavelengths: First evidence for radial variations of the dust properties
• Molecules with ALMA at Planet-forming Scales (MAPS) I: Program Overview and Highlights
• The cometary composition of a protoplanetary disk as revealed by complex cyanides
• Chemistry in Disks. IV. Benchmarking gas-grain chemical models with surface reactions
• Constraining the X-ray and Cosmic Ray Ionization Chemistry of the TW Hya Protoplanetary Disk: Evidence for a Sub-interstellar Cosmic Ray Rate
• Chemical Processes in Protoplanetary Disks
• Chemical evolution of turbulent protoplanetary disks and the Solar nebula
• Disk Imaging Survey of Chemistry with SMA: II. Southern Sky Protoplanetary Disk Data and Full Sample Statistics
• Disk Imaging Survey of Chemistry with SMA (DISCS): I. Taurus Protoplanetary Disk Data
• Detecting Weak Spectral Lines in Interferometric Data through Matched Filtering
• H2CO and N2H+ in Protoplanetary Disks: Evidence for a CO-ice Regulated Chemistry
• Photodissociation of interstellar N2
• Rotating molecular outflows: the young T Tauri star in CB26
• Consistent dust and gas models for protoplanetary disks III. Models for selected objects from the FP7 DIANA project
• Chemistry in Protoplanetary Disks: A Sensitivity Analysis
• Chemistry in Disks. III. -- Photochemistry and X-ray driven chemistry probed by the ethynyl radical (CCH) in DM Tau, LkCa 15, and MWC 480
• Protoplanetary Disk Structure With Grain Evolution: the ANDES Model
• Consistent dust and gas models for protoplanetary disks: II. Chemical networks and rates
• Chemistry in disks. XI. Sulfur-bearing species as tracers of protoplanetary disk physics and chemistry: the DM Tau case
• The masses of young stars: CN as a probe of dynamical masses
• First detection of c-C3H2 in a circumstellar disk
• Chemistry in Disks X: The Molecular Content of Proto-planetary Disks in Taurus
• CID: Chemistry in disks VI.sulfur-bearing molecules in the protoplanetary disks surrounding LkCa15, MWC480, DM Tau, and GO Tau
• Chemistry in Disks. IX. Observations and modeling of HCO+ and DCO+ in DM Tau
• First detection of gas-phase ammonia in a planet-forming disk
• Chemistry in Disks. V: CN and HCN in proto-planetary disks
• Impact of grain evolution on the chemical structure of protoplanetary disks
• The Distribution and Chemistry of H${}_2$CO in the DM Tau Protoplanetary Disk
• Stellar energetic particle ionization in protoplanetary disks around T Tauri stars
• Stacking Spectra in Protoplanetary Disks: Detecting Intensity Profiles from Hidden Molecular Lines in HD 163296
• Molecular line radiative transfer in protoplanetary disks: Monte Carlo simulations versus approximate methods
• An unbiased ALMA spectral survey of the LkCa 15 and MWC 480 protoplanetary disks
• The chemistry of disks around T Tauri and Herbig Ae/Be stars
• Chemistry in a gravitationally unstable protoplanetary disc
• Millimeter Observations of the Transition Disk around HD135344B (SAO 206462)
• Molecular line emission from a protoplanetary disk irradiated externally by a nearby massive star
• The CN/C15 N isotopic ratio towards dark clouds
• H2CO distribution and formation in the TW Hya disk
• The Ionization Fraction in the DM Tau Protoplanetary Disk
• Chemical and thermal structure of protoplanetary disks as observed with ALMA
• The Effects of Initial Abundances on Nitrogen in Protoplanetary Disks
• X-ray radiative transfer in protoplanetary disks - The role of dust and X-ray background fields
• Molecular content of the circumstellar disk in AB Aur: First detection of SO in a circumstellar disk
• Chemical composition of the circumstellar disk around AB Aurigae
• Protoplanetary disks: Sensitivity of the chemical composition to various model parameters
• H${}_2$S observations in young stellar disks in Taurus
• An Unbiased 1.3 mm Emission Line Survey of the Protoplanetary Disk Orbiting LkCa 15
• Modeling Time Dependent Water Chemistry Due to Powerful X-ray Flares from T-Tauri Stars
• PRODIGE -- Planet-forming disks in Taurus with NOEMA. I. Overview and first results for 12CO, 13CO, and C18O
• Chemical evolution of a protoplanetary disk
• Chemistry in protoplanetary disks (short review in Russian)
• Protoplanetary Disk Chemistry