TY - JOUR
T1 - SÍGAME Simulations of the [{\rm{C}}\,{\rm{II}}], [{\rm{O}}\,{\rm{I}}], and [{\rm{O}}\,{\rm{III}}] Line Emission from Star-forming Galaxies at z\simeq 6
AU - Olsen, Karen
AU - Greve, Thomas R.
AU - Narayanan, Desika
AU - Thompson, Robert
AU - Davé, Romeel
AU - Niebla Rios, Luis
AU - Stawinski, Stephanie
PY - 2017/9/7
Y1 - 2017/9/7
N2 - Of the almost 40 star-forming galaxies at z≳ 5 (not counting
quasi-stellar objects) observed in [{{C}} {{II}}] to date, nearly half
are either very faint in [{{C}} {{II}}] or not detected at all, and fall
well below expectations based on locally derived relations between star
formation rate and [{{C}} {{II}}] luminosity. This has raised questions
as to how reliable [{{C}} {{II}}] is as a tracer of star formation
activity at these epochs and how factors such as metallicity might
affect the [{{C}} {{II}}] emission. Combining cosmological zoom
simulations of galaxies with SÍGAME (SImulator of GAlaxy
Millimeter/submillimeter Emission), we modeled the multiphased
interstellar medium (ISM) and its emission in [{{C}} {{II}}], as well as
in [O I] and [O III], from 30 main-sequence galaxies at z≃ 6 with
star formation rates ˜3-23 {M}⊙
{{yr}}-1, stellar masses ˜ (0.7{--}8)×
{10}9 {M}⊙ , and metallicities ˜
(0.1{--}0.4)× {Z}⊙ . The simulations are able to
reproduce the aforementioned [{{C}} {{II}}] faintness of some normal
star-forming galaxy sources at z≥slant 5. In terms of [O I] and [O
III], very few observations are available at z≳ 5, but our
simulations match two of the three existing z≳ 5 detections of [O
III] and are furthermore roughly consistent with the [O I] and [O III]
luminosity relations with star formation rate observed for local
starburst galaxies. We find that the [{{C}} {{II}}] emission is
dominated by the diffuse ionized gas phase and molecular clouds, which
on average contribute ˜66% and ˜27%, respectively. The
molecular gas, which constitutes only ˜ 10 % of the total gas
mass, is thus a more efficient emitter of [{{C}} {{II}}] than the
ionized gas, which makes up ˜85% of the total gas mass. A
principal component analysis shows that the [{{C}} {{II}}] luminosity
correlates with the star formation activity of a galaxy as well as its
average metallicity. The low metallicities of our simulations together
with their low molecular gas mass fractions can account for their [{{C}}
{{II}}] faintness, and we suggest that these factors may also be
responsible for the [{{C}} {{II}}]-faint normal galaxies observed at
these early epochs.
AB - Of the almost 40 star-forming galaxies at z≳ 5 (not counting
quasi-stellar objects) observed in [{{C}} {{II}}] to date, nearly half
are either very faint in [{{C}} {{II}}] or not detected at all, and fall
well below expectations based on locally derived relations between star
formation rate and [{{C}} {{II}}] luminosity. This has raised questions
as to how reliable [{{C}} {{II}}] is as a tracer of star formation
activity at these epochs and how factors such as metallicity might
affect the [{{C}} {{II}}] emission. Combining cosmological zoom
simulations of galaxies with SÍGAME (SImulator of GAlaxy
Millimeter/submillimeter Emission), we modeled the multiphased
interstellar medium (ISM) and its emission in [{{C}} {{II}}], as well as
in [O I] and [O III], from 30 main-sequence galaxies at z≃ 6 with
star formation rates ˜3-23 {M}⊙
{{yr}}-1, stellar masses ˜ (0.7{--}8)×
{10}9 {M}⊙ , and metallicities ˜
(0.1{--}0.4)× {Z}⊙ . The simulations are able to
reproduce the aforementioned [{{C}} {{II}}] faintness of some normal
star-forming galaxy sources at z≥slant 5. In terms of [O I] and [O
III], very few observations are available at z≳ 5, but our
simulations match two of the three existing z≳ 5 detections of [O
III] and are furthermore roughly consistent with the [O I] and [O III]
luminosity relations with star formation rate observed for local
starburst galaxies. We find that the [{{C}} {{II}}] emission is
dominated by the diffuse ionized gas phase and molecular clouds, which
on average contribute ˜66% and ˜27%, respectively. The
molecular gas, which constitutes only ˜ 10 % of the total gas
mass, is thus a more efficient emitter of [{{C}} {{II}}] than the
ionized gas, which makes up ˜85% of the total gas mass. A
principal component analysis shows that the [{{C}} {{II}}] luminosity
correlates with the star formation activity of a galaxy as well as its
average metallicity. The low metallicities of our simulations together
with their low molecular gas mass fractions can account for their [{{C}}
{{II}}] faintness, and we suggest that these factors may also be
responsible for the [{{C}} {{II}}]-faint normal galaxies observed at
these early epochs.
KW - cosmology: theory
KW - galaxies: high-redshift
KW - galaxies: ISM
KW - line: formation
KW - methods: numerical
KW - submillimeter: ISM
U2 - 10.3847/1538-4357/aa86b4
DO - 10.3847/1538-4357/aa86b4
M3 - Article
VL - 846
SP - 105
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
ER -