J/A+A/629/A134 Radiative contribution from stripped stars (Goetberg+, 2019)
The impact of stars stripped in binaries on the integrated spectra of
stellar populations.
Goetberg Y., de Mink S.E., Groh J.H., Leitherer C., Norman C.
<Astron. Astrophys. 629, A134 (2019)>
=2019A&A...629A.134G 2019A&A...629A.134G (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Galaxies, optical ; Populations, stellar ; Spectroscopy
Keywords: ultraviolet: galaxies - binaries: close - stars: atmospheres -
galaxies: starburst - galaxies: stellar content
Abstract:
Stars stripped of their envelopes from interaction with a binary
companion emit a significant fraction of their radiation as ionizing
photons. They are potentially important stellar sources of ionizing
radiation, however, they are still often neglected in spectral
synthesis simulations or simulations of stellar feedback. In
anticipating the large datasets of galaxy spectra from the upcoming
James Webb Space Telescope, we modeled the radiative contribution from
stripped stars by using detailed evolutionary and spectral models. We
estimated their impact on the integrated spectra and specifically on
the emission rates of HI-, HeI-, and HeII-ionizing photons
from stellar populations. We find that stripped stars have the largest
impact on the ionizing spectrum of a population in which star
formation halted several Myr ago. In such stellar populations,
stripped stars dominate the emission of ionizing photons, mimicking a
younger stellar population in which massive stars are still present.
Our models also suggest that stripped stars have harder ionizing
spectra than massive stars. The additional ionizing radiation, with
which stripped stars contribute affects observable properties that are
related to the emission of ionizing photons from stellar populations.
In co-eval stellar populations, the ionizing radiation from stripped
stars increases the ionization parameter and the production efficiency
of hydrogen ionizing photons. They also cause high values for these
parameters for about ten times longer than what is predicted for
massive stars. The effect on properties related to non-ionizing
wavelengths is less pronounced, such as on the ultraviolet continuum
slope or stellar contribution to emission lines. However, the hard
ionizing radiation from stripped stars likely introduces a
characteristic ionization structure of the nebula, which leads to the
emission of highly ionized elements such as O2+ and C3+. We,
therefore, expect that the presence of stripped stars affects the
location in the BPT diagram and the diagnostic ratio of OIII to
OII nebular emission lines. Our models are publicly available
through CDS database and on the STARBURST99 website.
Description:
We provide results for the radiative contribution from stripped stars
at four different metallicities: Z = 0.014 (solar), 0.006 (similar to
the Large Magellanic Cloud), 0.002 (similar to the Small Magellanic
Cloud), and 0.0002 (very low metallicity environment).
For each metallicity, we provide the following files:
nbrstrippedZ0.0XX.txt
QZ0.0XXstripped_starburst.txt
SEDZ0.0XXstarburst.txt
UVZ0.0XXstarburst.txt
optZ0.0XXstarburst.txt
SEDZ0.0XXconstant.txt
UVZ0.0XXconstant.txt
optZ0.0XXconstant.txt
where the XX is replaced to match the specific metallicity.
We label the quantities for a 106M☉ instantaneous starburst
with '_starburst' and the quantities for a population in which stars
are formed at a constant rate of 1M☉/yr with '_constant'. The
files only contain the contribution from stripped stars and neglects
the contribution from other stars in the stellar population.
Below, we describe the content of the different files in detail.
------------------------
nbrs0XX.dat (nbrstrippedZ0.0XX.txt)
------------------------
This file gives the number of stripped stars present in a stellar
population at given times. It has eight columns and the first row is a
header. The file only exists for the instantaneous starburst. The
first column contains the time in years. The second column provides
the total number of stripped stars present in the population at the
given time. The columns number 3, 4, and 5 give the number of stripped
stars present that were formed via Case A type mass transfer, Case B
type mass transfer, and successful ejection of a common envelope that
was initiated during the Hertzsprung gap passage of the donor star,
respectively. The columns number 6, 7, and 8 contain the number of
stripped stars that have progenitors that were initially more massive
than 10M☉, 5M☉, and 3M☉, respectively.
-----------------------
q0.0XX.dat (QZ0.0XXstripped_starburst.txt)
-----------------------
This file gives the emission rates of ionizing photons from stripped
stars at different times. It has four columns and the first five rows
are a header. The file only exists for the instantaneous starburst.
The first column gives the time in years. The column number 2, 3, and
4 provide the logarithm of the emission rates of HI-, HeI-, and
HeII-ionizing photons from stripped stars respectively. In the case
there were no stripped stars present in the population, the logarithm
of the ionizing emission rates are set to -30.
-----------------------
sed/SEDZ0.0XXxxx.txt
-----------------------
This file gives the spectral energy distribution from stripped stars
at different times. The header is six rows. The first row of data is
the wavelength array with values in Angstrom and the first element in
the array is empty. The first column represents the time given in
years. Each row gives the spectral energy distribution for the
contribution from stripped stars at each time (given in the first
element of each row). The spectral energy distribution is given in
luminosity in units of erg/s/Å. There is one file for the
instantaneous starburst and one for the constant star-formation.
-----------------------
uv/UVZ0.0XXxxx.txt
-----------------------
This file gives the contribution from stripped stars in the UV
spectral range (1000-3000 Angstrom) in a higher resolution than the
spectral energy distribution file. The first six rows are part of the
header. The first row of data corresponds to the wavelength array in
Angstrom (first element empty). The following rows contain the
spectral energy distribution from stripped stars and in the UV. The
first element in each row gives the time in years. The UV spectral
energy distribution is given in luminosity in unit erg/s?Å. This
file exists for both the instantaneous starburst and the constant star
formation.
-----------------------
opt/optZ0.0XXxxx.txt
-----------------------
This file gives the contribution from stripped stars in the optical
spectral range (3000-9000 Angstrom) in a higher resolution than the
spectral energy distribution file. The first six rows are part of the
header. The first row of data corresponds to the wavelength array in
Angstrom (first element empty). The following rows contain the
spectral energy distribution from stripped stars and in the optical.
The first element in each row gives the time in years. The optical
spectral energy distribution is given in luminosity in unit erg/s/Å.
This file exists for both the instantaneous starburst and the
constant star formation.
For achieving the number of stripped stars as function of time or the
emission rates of ionizing photons from stripped stars as function of
time in the case of constant star-formation, the values in the files
for the instantaneous starburst can easily be convolved with time.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
nbrs0002.dat 77 500 Z=0.0002 number of stripped stars
nbrs002.dat 77 500 Z=0.002 number of stripped stars
nbrs006.dat 77 500 Z=0.006 number of stripped stars
nbrs014.dat 77 500 Z=0.014 number of stripped stars
q0002.dat 83 500 Z=0.0002 emission rates of ionizing photons
from stripped stars
q002.dat 83 500 Z=0.002 emission rates of ionizing photons
from stripped stars
q006.dat 83 500 Z=0.006 emission rates of ionizing photons
from stripped stars
q014.dat 83 500 Z=0.014 emission rates of ionizing photons
from stripped stars
sed/* . 8 Spectral energy distribution from stripped stars
at different times
uv/* . 8 Contribution from stripped stars in the UV
spectral range (1000-3000Å) in a higher
resolution than the spectral energy
distribution file.
opt/* . 8 Contribution from stripped stars in the optical
spectral range (3000-9000Å) in a higher
resolution than the spectral energy
distribution file
--------------------------------------------------------------------------------
Byte-by-byte Description of file (#): nbrs*.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 F22.11 yr Time Time
25- 29 F5.1 --- NTot Total number of stripped stars present in the
population at the given time (total_nbr)
33- 37 F5.1 --- NcaseA Number of stripped stars present that were formed
via Case A type mass transfer (nbr_caseA)
41- 45 F5.1 --- NCaseB Number of stripped stars present that were formed
via Case B type mass transfer (nbr_caseB)
48- 52 F5.1 --- NBCEE Number of stripped stars present that were formed
via successful ejection of a common envelope
that was initiated during the Hertzsprung gap
passage of the donor star (nbr_BCEE)
57- 61 F5.1 --- Ngtr10 Number of stripped stars that have progenitors
that were initially more massive than 10M☉
(nbrgtr10)
65- 69 F5.1 --- Ngtr5 Number of stripped stars that have progenitors
that were initially more massive than 5M☉
(nbrgtr5)
73- 77 F5.1 --- Ngtr3 Number of stripped stars that have progenitors
that were initially more massive than 3M☉
(nbrgtr3)
--------------------------------------------------------------------------------
Byte-by-byte Description of file (#): q*.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 F22.11 yr Time Time
24- 42 F19.15 [s-1] log10(Q0) ?=-30 logarithm of the emission rates of
HI-ionizing photons from stripped stars
44- 62 F19.15 [s-1] log10(Q1) ?=-30 logarithm of the emission rates of
HeI-ionizing photons from stripped stars
65- 83 F19.15 [s-1] log10(Q2) ?=-30 logarithm of the emission rates of
HeII-ionizing photons from stripped stars
--------------------------------------------------------------------------------
Acknowledgements:
Ylva Gotberg, ygoetberg(at)carnegiescience.edu
(End) Patricia Vannier [CDS] 16-Aug-2019