Physical conditions in diffuse interstellar medium of local and high redshift galaxies: measurements based on excitation of H$_2$ rotational and CI fine-structure levels. (arXiv:2007.12231v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Klimenko_V/0/1/0/all/0/1">V.V. Klimenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Balashev_S/0/1/0/all/0/1">S.A. Balashev</a>
We present results of analysis of physical conditions (number density,
intensity of UV field, kinetic temperature) in the cold H$_2$-bearing
interstellar medium of local and high redshift galaxies. Our measurements based
on the fit to the observed population of H$_2$ rotational levels and CI
fine-structure levels with the help of grids of numerical models calculated
with the PDR Meudon code. A joint analysis of low H$_2$ rotational levels and
CI fine-structure levels allows to break the degeneracy in the
$I_{UV}-n_{rm{H}}$ plane and provides significantly tighter constraints on the
number density and intensity of UV field. Using archive data from the VLT/UVES,
KECK/HIRES, HST/STIS and FUSE telescopes we selected 12 high redshift damped
Ly$alpha$ systems (DLAs) in quasar spectra and 14 H$_2$ absorption systems
along the lines of sight towards stars in the Milky-Way and the Magellanic
Clouds galaxies. These systems have strong H$_2$ components with the column
density $log N({rm{H_2}})/{rm{cm}}^{-2}>18$ and associated CI absorptions.
We find that H$_2$-bearing medium in high redshift DLAs and in local galaxies
has similar values of the kinetic temperatures $T_{rm{kin}}sim100$K and
number density $10-500$ cm$^{-3}$. However, the intensity of incident UV
radiation in DLAs is varied in the wide range ($0.1-100$ units of Mathis
field), while it is $sim0.1-3$ units of Mathis field for H$_2$ systems in
Milky-Way and LMC and SMC galaxies. The large dispersion of measured UV flux in
DLAs is probably a consequence that DLA sample probes the galaxies selected
from the overall galaxy population at high-z and therefore corresponds to the
wide range of the physical conditions.
We present results of analysis of physical conditions (number density,
intensity of UV field, kinetic temperature) in the cold H$_2$-bearing
interstellar medium of local and high redshift galaxies. Our measurements based
on the fit to the observed population of H$_2$ rotational levels and CI
fine-structure levels with the help of grids of numerical models calculated
with the PDR Meudon code. A joint analysis of low H$_2$ rotational levels and
CI fine-structure levels allows to break the degeneracy in the
$I_{UV}-n_{rm{H}}$ plane and provides significantly tighter constraints on the
number density and intensity of UV field. Using archive data from the VLT/UVES,
KECK/HIRES, HST/STIS and FUSE telescopes we selected 12 high redshift damped
Ly$alpha$ systems (DLAs) in quasar spectra and 14 H$_2$ absorption systems
along the lines of sight towards stars in the Milky-Way and the Magellanic
Clouds galaxies. These systems have strong H$_2$ components with the column
density $log N({rm{H_2}})/{rm{cm}}^{-2}>18$ and associated CI absorptions.
We find that H$_2$-bearing medium in high redshift DLAs and in local galaxies
has similar values of the kinetic temperatures $T_{rm{kin}}sim100$K and
number density $10-500$ cm$^{-3}$. However, the intensity of incident UV
radiation in DLAs is varied in the wide range ($0.1-100$ units of Mathis
field), while it is $sim0.1-3$ units of Mathis field for H$_2$ systems in
Milky-Way and LMC and SMC galaxies. The large dispersion of measured UV flux in
DLAs is probably a consequence that DLA sample probes the galaxies selected
from the overall galaxy population at high-z and therefore corresponds to the
wide range of the physical conditions.
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