Radiative cooling rates, ion fractions, molecule abundances, and line emissivities including self-shielding and both local and metagalactic radiation fields

Abstract

We use the spectral synthesis code cloudy to tabulate the properties of gas for an extensive range in redshift (z = 0 - 9), temperature (log T[K] = 1 - 9.5), metallicity (log Z/Z⊙ = −4 - +0.5, Z = 0), and density (log nH[ cm−3] = −8 - +6). This therefore includes gas with properties characteristic of the interstellar, circumgalactic and intergalactic media. The gas is exposed to a redshift-dependent UV/X-ray background, while for the self-shielded lower-temperature gas (i.e. ISM gas) an interstellar radiation field and cosmic rays are added. The radiation field is attenuated by a density- and temperature-dependent column of gas and dust. Motivated by the observed star formation law, this gas column density also determines the intensity of the interstellar radiation field and the cosmic ray density. The ionization balance, molecule fractions, cooling rates, line emissivities, and equilibrium temperatures are calculated self-consistently. We include dust, cosmic rays, and the interstellar radiation field step-by-step to study their relative impact. These publicly available tables are ideal for hydrodynamical simulations. They can be used stand alone or coupled to a non-equilibrium network for a subset of elements. The release includes a C routine to read in and interpolate the tables, as well as an easy to use python graphical user interface to explore the tables.

Predictions for the angular dependence of gas mass flow rate and metallicity in the circumgalactic medium

“…Better measurements will also indirectly help constrain stellar population yields (e.g. Kobayashi, Leung & Nomoto 2020), particularly as more complete treatments of the relevant chemistry become common in cosmological simulations (Ploeckinger & Schaye 2020).…”

Diagnosing the interstellar medium of galaxies with far-infrared emission lines

“…We predict line luminosities with the help of Cloudy v17.01 (Ferland et al 2017), using a set of cooling tables presented by Ploeckinger & Schaye (2020). Cloudy is a 1D spectral synthesis code that predicts atomic and molecular line intensities in different environments using an escape probability formalism.…”

“…The two cooling tables we use in this work, ideal for cosmological simulations, have the ISRF and CR rate values reduced by 1 dex relative to the MW values (Black 1987;Indriolo et al 2007) to better match the observations of the transition between atomic and molecular hydrogen (Ploeckinger & Schaye 2020). In other words, physical parameters decrease: the SFR surface density Σ SFR decreases from 10 −3 M yr −1 kpc −2 to 10 −4 M yr −1 kpc −2 , and the CR hydrogen ionisation rate log ζ decreases from −15.7 s −1 to −16.7 s −1 .…”

“…The neutral gas mass and the ISRF are used to create the neutral cloud structures inside galaxies, while the ionised gas mass is used to create the DIG. After calibration with the [N ii] lines for the DIG, we obtain the luminosity of [C ii] line for each phase using Cloudy cooling tables (Ploeckinger & Schaye 2020). Finally, we calculate the total [C ii] luminosity in a galaxy with the contributions from the three ISM phases combined.…”

“…Next, we calculate physical properties in each phase to obtain the neutral clouds and DIG structures. We use Cloudy cooling tables (Ploeckinger & Schaye 2020) to get the line luminosity for [C ii]. We first calculate L [C ii],DIG and then calibrate the ionised gas using the predicted luminosities of the [N ii] lines.…”