TY - JOUR
T1 - Column Density Profiles of Cold Clouds Driven by Galactic Outflows
AU - Cottle, J'Neil
AU - Scannapieco, Evan
AU - Brüggen, Marcus
N1 - Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved..
PY - 2018/9/1
Y1 - 2018/9/1
N2 - Absorption line studies are essential to understanding the origin, nature, and impact of starburst-driven galactic outflows. Such studies have revealed a multiphase medium with a number of poorly understood features leading to a need to study the ionization mechanism of this gas. To better interpret these observations, we make use of a suite of adaptive mesh refinement hydrodynamic simulations of cold, atomic clouds driven by hot, supersonic outflows, including the effect of radiative cooling, thermal conduction, and an ionizing background characteristic of a starbursting galaxy. Using a new analysis tool, trident, we estimate the equilibrium column density distributions for 10 different ions: H i, Mg ii, C ii, C iii, C iv, Si iii, Si iv, N v, O vi, and Ne viii. These are fit to model profiles with two parameters describing the maximum column density and coverage, and for each ion we provide a table of these fit parameters, along with average velocities and line widths. Our results are most sensitive to Mach number and conduction efficiency, with higher Mach numbers and more efficient conduction leading to more compact, high column density clouds. We use our results to interpret down-the-barrel observations of outflows and find that the adopted ionization equilibrium model overpredicts column densities of ions such as Si iv and does not adequately capture the observed trends for N v and O vi, implying the presence of strong nonequilibrium ionization effects.
AB - Absorption line studies are essential to understanding the origin, nature, and impact of starburst-driven galactic outflows. Such studies have revealed a multiphase medium with a number of poorly understood features leading to a need to study the ionization mechanism of this gas. To better interpret these observations, we make use of a suite of adaptive mesh refinement hydrodynamic simulations of cold, atomic clouds driven by hot, supersonic outflows, including the effect of radiative cooling, thermal conduction, and an ionizing background characteristic of a starbursting galaxy. Using a new analysis tool, trident, we estimate the equilibrium column density distributions for 10 different ions: H i, Mg ii, C ii, C iii, C iv, Si iii, Si iv, N v, O vi, and Ne viii. These are fit to model profiles with two parameters describing the maximum column density and coverage, and for each ion we provide a table of these fit parameters, along with average velocities and line widths. Our results are most sensitive to Mach number and conduction efficiency, with higher Mach numbers and more efficient conduction leading to more compact, high column density clouds. We use our results to interpret down-the-barrel observations of outflows and find that the adopted ionization equilibrium model overpredicts column densities of ions such as Si iv and does not adequately capture the observed trends for N v and O vi, implying the presence of strong nonequilibrium ionization effects.
KW - galaxies: ISM
KW - galaxies: abundances
KW - galaxies: kinematics and dynamics
KW - galaxies: starburst
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U2 - 10.3847/1538-4357/aad55c
DO - 10.3847/1538-4357/aad55c
M3 - Article
AN - SCOPUS:85053131617
SN - 0004-637X
VL - 864
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 96
ER -