Related papers: Unlocking CO Depletion in Protoplanetary Disks I. …
CO is the most widely used gas tracer of protoplanetary disks. Its abundance is usually assumed to be an interstellar ratio throughout the warm molecular layer of the disk. But recent observations of low CO gas abundance in many…
The gas-phase CO abundance (relative to hydrogen) in protoplanetary disks decreases by up to 2 orders of magnitude from its ISM value ${\sim}10^{-4}$, even after accounting for freeze-out and photo-dissociation. Previous studies have shown…
CO is thought to be the main reservoir of volatile carbon in protoplanetary disks, and thus the primary initial source of carbon in the atmospheres of forming giant planets. However, recent observations of protoplanetary disks point towards…
CO has long been thought to be the best tracer to measure gas masses as it is readily detected at (sub)mm wavelengths in many disks. Inferred gas masses from CO in recent ALMA observations of large samples of disks seem inconsistent with…
Protoplanetary disk mass is a key parameter controlling the process of planetary system formation. CO molecular emission is often used as a tracer of gas mass in the disk. In this study we consider the ability of CO to trace the gas mass…
Molecular abundances in protoplanetary disks are highly sensitive to the local physical conditions, including gas temperature, gas density, radiation field, and dust properties. Often multiple factors are intertwined, impacting the…
Empirical constraints of fundamental properties of protoplanetary disks are essential for understanding planet formation and planetary properties (1,2). Carbon monoxide (CO) gas is often used to constrain disk properties (3). However,…
Carbon monoxide (CO) is the most commonly used tracer of molecular gas in the inner regions of protoplanetary disks. CO can be used to constrain the excitation and structure of the circumstellar environment. Absorption line spectroscopy…
The gas mass of protoplanetary disks, and the gas-to-dust ratio, are two key elements driving the evolution of these disks and the formation of planetary system. We explore here to what extent CO (or its isotopologues) can be used as a…
Recent observations show that the CO gas abundance, relative to H$_2$, in many 1-10 Myr old protoplanetary disks may be heavily depleted, by a factor of 10-100 compared to the canonical interstellar medium value of 10$^{-4}$. When and how…
Gas in protostellar disks provides the raw material for giant planet formation and controls the dynamics of the planetesimal-building dust grains. Accurate gas mass measurements help map the observed properties of planet-forming disks onto…
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…
One of the methods for deriving disk masses relies on direct observations of the gas, whose bulk mass is in the outer cold ($T\lesssim30$K) regions. This zone can be well traced by rotational lines of less abundant CO isotopologues, that…
In regions where stars form, variations in density and temperature can cause gas to freeze-out onto dust grains forming ice mantles, which influences the chemical composition of a cloud. The aim of this paper is to understand in detail the…
In this article we review the methods used to determine the gas and dust masses of protoplanetary disks, with an emphasis on the lesser characterized total gas mass. Our review encompasses all the indirect tracers and the methodology that…
The structure in density and temperature of protoplanetary disks surrounding low-mass stars is not yet well known. The protoplanetary disks mid-planes are expected to be very cold and thus depleted in molecules in gas phase, especially CO.…
The mass of a protoplanetary disk limits the formation and future growth of any planet. Masses of protoplanetary disks are usually calculated from measurements of the dust continuum emission by assuming an interstellar gas-to-dust ratio. To…
Understanding the gas abundance distribution is essential when tracing star formation using molecular line observations. Changing density and temperature conditions cause gas to freeze-out onto dust grains, and this needs to be taken into…
Molecular emission is used to investigate both the physical and chemical properties of protoplanetary disks. Therefore, to accurately derive disk properties, we need a thorough understanding of the behavior of the molecular probes we rely…
Despite intensive studies of protoplanetary disks, there is still no reliable way to determine their total mass and their surface density distribution, quantities that are crucial for describing both the structure and the evolution of disks…