Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

Glover, Simon C. O.; Clark, Paul

doi:10.1093/mnras/stv2863

Cited by 107 publications

(120 citation statements)

References 74 publications

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“…It is important to note that since the initial conditions affect the evolution of each cloud, when star formation is triggered will be at different times for each run. We make use of the clouds simulated in previous papers by and Glover & Clark (2016) since they already cover part of the parameter space we intend to study. Below we cover what the variations in initial conditions are but refer the reader to those papers for full details.…”

Section: Initial Conditionsmentioning

confidence: 99%

“…The simulations by Glover & Clark (2016) have an initial mass of 10 4 M⊙, initial density of n = 276 cm −3 , have an initial molecular fraction of f (H2) = 0 and have a turbulent velocity field that is generated from purely solenoidal modes. In addition the ISRF and CRIR are scaled in the same way as , however the CRIR is scaled proportional to ζH = 1 × 10 −17 s −1 .…”

Section: Initial Conditionsmentioning

confidence: 99%

“…To isolate the effect of varying individual environmental properties, we thus perform an additional set of simulations for our current study. First, and Glover & Clark (2016) scale the ISRF and CRIR together making it hard to disentangle the effect of either, therefore we run four clouds that vary either the ISRF or the CRIR. Additionally the small mass clouds in and all of the clouds in Glover & Clark (2016) have a slightly different initially density, different turbulent velocity field, a different αvir and slightly different ζH.…”

Section: Initial Conditionsmentioning

confidence: 99%

“…For more details one can also see the study by Bertram et al (2015) where they explore the binding and star-forming properties of cloud that are exposed to even higher ISRFs and CRIRs than we adopt here. In addition, clouds from Glover & Clark (2016) apply an external pressure term to prevent "evaporation" of material (Benz 1990). However we find that the external pressure has minimal influence on whether our clouds will collapse and form stars.…”

Section: Initial Conditionsmentioning

confidence: 99%

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CO line ratios in molecular clouds: the impact of environment

Peñaloza

Clark

Glover

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Line emission is strongly dependent on the local environmental conditions in which the emitting tracers reside. In this work, we focus on modelling the CO emission from simulated giant molecular clouds (GMCs), and study the variations in the resulting line ratios arising from the emission from the J = 1−0, J = 2−1 and J = 3−2 transitions. We perform a set of smoothed particle hydrodynamics (SPH) simulations with timedependent chemistry, in which environmental conditions -including total cloud mass, density, size, velocity dispersion, metallicity, interstellar radiation field (ISRF) and the cosmic ray ionisation rate (CRIR) -were systematically varied. The simulations were then post-processed using radiative transfer to produce synthetic emission maps in the 3 transitions quoted above. We find that the cloud-averaged values of the line ratios can vary by up to ±0.3 dex, triggered by changes in the environmental conditions. Changes in the ISRF and/or in the CRIR have the largest impact on line ratios since they directly affect the abundance, temperature and distribution of CO-rich gas within the clouds. We show that the standard methods used to convert CO emission to H 2 column density can underestimate the total H 2 molecular gas in GMCs by factors of 2 or 3, depending on the environmental conditions in the clouds.

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Section: Initial Conditionsmentioning

confidence: 99%

Section: Initial Conditionsmentioning

confidence: 99%

Section: Initial Conditionsmentioning

confidence: 99%

Section: Initial Conditionsmentioning

confidence: 99%

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CO line ratios in molecular clouds: the impact of environment

Peñaloza

Clark

Glover

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Detectable C I may be a useful indicator of the presence of colder, denser gas with higher molecular content in those more distant systems (Papadopoulos et al 2004;Srianand et al 2005;Glover & Clark 2016), and its excitation can provide both information on local physical conditions and constraints on the redshift dependence of the temperature of the cosmic microwave background (CMB).…”

Section: Introductionmentioning

confidence: 99%

Thermal Pressures in the Interstellar Medium of the Magellanic Clouds*

Welty

Lauroesch

Wong

et al. 2016

ApJ

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We discuss the thermal pressures (n H T) in predominantly cold, neutral interstellar gas in the Magellanic Clouds, derived from analyses of the fine-structure excitation of neutral carbon, as seen in high-resolution Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra of seven diverse sight lines in the LMC and SMC. Detailed fits to the line profiles of the absorption from C I, C I * , and C I ** yield consistent column densities for the three to six C I multiplets detected in each sight line. In the LMC and SMC, N(C I tot ) is consistent with Galactic trends versus N(Na I) and N(CH), but is slightly lower versus N(K I) and N(H 2 ). As for N(Na I) and N(K I), N(C I tot ) is generally significantly lower, for a given N(H tot ), in the LMC and (especially) in the SMC, compared to the local Galactic relationship. For the LMC and SMC components with well-determined column densities for C I, C I * , and C I ** , the derived thermal pressures are typically factors of a few higher than the values found for most cold, neutral clouds in the Galactic ISM. Such differences are consistent with the predictions of models for clouds in systems (like the LMC and SMC) that are characterized by lower metallicities, lower dust-to-gas ratios, and enhanced radiation fields-where higher pressures are required for stable cold, neutral clouds. The pressures may be further enhanced by energetic activity (e.g., due to stellar winds, star formation, and/or supernova remnants) in several of the regions probed by these sight lines. Comparisons are made with the C I observed in some quasar absorption-line systems.

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