Related papers: The CO-to-H2 Conversion Factor

The most common means of converting an observed CO line intensity into a molecular gas mass requires the use of a conversion factor (Xco). While in the Milky Way this quantity does not appear to vary significantly, there is good reason to…

Carbon monoxide (CO) emission is a widely used tracer of molecular hydrogen (H$_2$) in the interstellar medium (ISM), owing to its abundance, low excitation energy, and ease of detection in cold molecular environments, in contrast to…

CO(J=1-0) line emission is a widely used observational tracer of molecular gas, rendering essential the X_CO factor, which is applied to convert CO luminosity to H_2 mass. We use numerical simulations to study how X_CO depends on numerical…

Characterizing the conversion factor between CO emission and column density of molecular hydrogen, X_CO, is crucial in studying the gaseous content of galaxies, its evolution, and relation to star formation. In most cases the conversion…

Our ability to trace the star-forming molecular gas is important to our understanding of the Universe. We can trace this gas using CO emission, converting the observed CO intensity into the H$_2$ gas mass of the region using the CO-to-H$_2$…

CO is the most widely used observational tracer of molecular gas. The observable CO luminosity is translated to H_2 mass via a conversion factor, X_CO, which is a source of uncertainty and bias. Despite variations in X_CO, the…

We study the relationship between the H2 and CO abundances in simulated molecular clouds using a fully dynamical model of magnetized turbulence coupled to a detailed chemical network. We find that the CO-to-H2 conversion factor for a given…

A reliable estimate of the molecular gas content in galaxies plays a crucial role in determining their dynamical and star-forming properties. However, H2, the dominant molecular species, is difficult to observe directly, particularly in the…

Relating the observed CO emission from giant molecular clouds (GMCs) to the underlying H2 column density is a long-standing problem in astrophysics. While the Galactic CO-H2 conversion factor (Xco) appears to be reasonably constant,…

We derive the CO-to-H2 conversion factor, X_CO = N(H2)/I_CO, across the Perseus molecular cloud on sub-parsec scales by combining the dust-based N(H2) data with the I_CO data from the COMPLETE Survey. We estimate an average X_CO ~ 3 x 10^19…

Carbon monoxide (CO) emission is the most widely used tracer of the bulk molecular gas in the interstellar medium (ISM) in extragalactic studies. The CO-to-H$_2$ conversion factor, $\alpha_{\rm CO}$, links the observed CO emission to the…

The factor relating CO emission to molecular hydrogen column density, XCO, is still subject to uncertainty, in particular at low metallicity. Here, to quantify XCO at two different spatial resolutions, we exploit a dust-based method…

We study the CO(1-0)-to-H$_2$ conversion factor ($X_{\rm CO}$) and the line ratio of CO(2-1)-to-CO(1-0) ($R_{21}$) across a wide range of metallicity ($0.1 \leq Z/Z_\odot \leq 3$) in high-resolution (~0.2 pc) hydrodynamical simulations of a…

We performed correlation analyses between the $^{12}$CO and $^{13}$CO $J=$1-0 line intensities in order to derive the variability of the CO-to-H$_2$ conversion factor ($X_{\rm CO, iso}$) in the central molecular zone (CMZ) of our Galaxy.…

Theoretical and observational investigations have indicated that the abundance of carbon monoxide (CO) is very sensitive to intrinsic properties of the gaseous medium, such as density, metallicity, and the background UV field. In order to…

We present theoretically-established values of the CO-to-H2 and C-to-H2 conversion factors that may be used to estimate the gas masses of external galaxies. We consider four distinct galaxy types, represented by M51, NGC 6946, M82 and SMC…

We estimate the conversion factor relating CO emission to H2 mass, alpha_CO, in five Local Group galaxies that span approximately an order of magnitude in metallicity - M31, M 33, the Large Magellanic Cloud (LMC), NGC 6822, and the Small…

Analyzing the Galactic plane CO survey with the Nobeyama 45-m telescope, we compared the spectral column density (SCD) of H$_2$ calculated for $^{12}$CO line using the current conversion factor $X_{\rm CO}$ to that for $^{13}$CO line under…

We show that the XCO factor, which converts the CO luminosity into the column density of molecular hydrogen has similar values for dense, fully molecular gas and for diffuse, partially molecular gas. We discuss the reasons of this…

[Abridged] Do some environments favor efficient conversion of molecular gas into stars? To answer this, we need to be able to estimate the H2 mass. Traditionally, this is done using CO and a few assumptions but the Herschel observations in…