Low-metallicity massive single stars with rotation III. Source
of ionization and C IV emission in I Zw 18

J 2025

Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18

SZECSI, Dorottya; Frank TRAMPER; Brankica KUBÁTOVÁ; Carolina KEHRIG; Jiri KUBAT et al.

Základní údaje

Originální název

Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18

Autoři

SZECSI, Dorottya; Frank TRAMPER; Brankica KUBÁTOVÁ; Carolina KEHRIG; Jiri KUBAT; Jiří KRTIČKA; Andreas A. C. SANDER a Miriam GARCIA

Vydání

ASTRONOMY & ASTROPHYSICS, LES ULIS CEDEX A, EDP SCIENCES S A, 2025, 0004-6361

Další údaje

Jazyk

angličtina

Typ výsledku

Článek v odborném periodiku

Obor

10308 Astronomy

Stát vydavatele

Francie

Utajení

není předmětem státního či obchodního tajemství

Odkazy

URL

Impakt faktor

Impact factor: 5.800 v roce 2024

Označené pro přenos do RIV

Ano

Kód RIV

RIV/00216224:14310/25:00144630

Organizační jednotka

Přírodovědecká fakulta

Klíčová slova anglicky

stars: evolution; stars: massive; stars: Wolf-Rayet; galaxies: dwarf; galaxies: starburst; ultraviolet: stars

Štítky

14312040, rivok

Příznaky

Mezinárodní význam, Recenzováno

Změněno: 21. 1. 2026 14:37, Mgr. Marie Novosadová Šípková, DiS.

Anotace

V originále

Context. Chemically homogeneously evolving stars have been proposed to account for several exotic phenomena, including gravitational-wave emissions, gamma-ray bursts and certain types of supernovae. Aims. Here we study whether these stars can explain the observations of the metal-poor star-forming dwarf galaxy, I Zwicky 18. Methods. We apply our synthetic spectral models from Paper II to (i) establish a classification sequence for these hot stars, (ii) predict the photonionizing flux and the strength of observable emission lines from a I Zw 18-like stellar population, and (iii) compare our predictions to all available observations of this galaxy. Results. Adding two new models computed with PoWR, we report that (i) these stars follow a unique sequence of classes: O -> WN -> WO (i.e. without ever being WC). From our population synthesis with standard assumptions, we predict that (ii) the source of the UV C IV lambda 1550 & Aring; and other emission bumps is a couple of dozen WO-type Wolf-Rayet stars (not WC as previously assumed) which are the result of chemically homogeneous evolution, while these, combined with the rest of the O-star population, account for the high He II ionizing flux and the spectral hardness. Contrasting our results against published optical and UV data from the literature and accounting for different aperture sizes and spatial regions probed by the observations, we find that (iii) our models are highly consistent with existing measurements. Conclusions. Since our "massive Pop II stars" might just as well exist in early star-forming regions, our findings have implications for upcoming James Webb Space Telescope (JWST) surveys: the first galaxies in the high-redshift Universe may also experience the extra contribution of UV photons and the kinds of exotic explosions that chemically homogeneous stellar evolution predicts. Given that our results apply for binary populations too as long as the same fraction (10%) of the systems evolves chemically homogeneously, we conclude that the stellar progenitors of gravitational waves may very well exist today in I Zw 18.

Návaznosti

GA25-15910S, projekt VaV

Název: Větry horkých hvězd: řešení nejistot ztráty hmoty v blízkosti Eddingtonovy limity

Investor: Grantová agentura ČR, Větry horkých hvězd: řešení nejistot ztráty hmoty v blízkosti Eddingtonovy limity

Citovat

SZECSI, Dorottya; Frank TRAMPER; Brankica KUBÁTOVÁ; Carolina KEHRIG; Jiri KUBAT; Jiří KRTIČKA; Andreas A. C. SANDER a Miriam GARCIA. Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18. ASTRONOMY & ASTROPHYSICS. LES ULIS CEDEX A: EDP SCIENCES S A, 2025, roč. 703, November, s. 1-18. ISSN 0004-6361. Dostupné z: https://doi.org/10.1051/0004-6361/202452483.

@article{2548994,
   author = {Szecsi, Dorottya and Tramper, Frank and Kubátová, Brankica and Kehrig, Carolina and Kubat, Jiri and Krtička, Jiří and Sander, Andreas A. C. and Garcia, Miriam},
   article_location = {LES ULIS CEDEX A},
   article_number = {November},
   doi = {https://doi.org/10.1051/0004-6361/202452483},
   keywords = {stars: evolution; stars: massive; stars: Wolf-Rayet; galaxies: dwarf; galaxies: starburst; ultraviolet: stars},
   language = {eng},
   issn = {0004-6361},
   journal = {ASTRONOMY & ASTROPHYSICS},
   title = {Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18},
   url = {https://doi.org/10.1051/0004-6361/202452483},
   volume = {703},
   year = {2025}
}

TY  - JOUR
ID  - 2548994
AU  - Szecsi, Dorottya - Tramper, Frank - Kubátová, Brankica - Kehrig, Carolina - Kubat, Jiri - Krtička, Jiří - Sander, Andreas A. C. - Garcia, Miriam
PY  - 2025
TI  - Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18
JF  - ASTRONOMY & ASTROPHYSICS
VL  - 703
IS  - November
SP  - 1-18
EP  - 1-18
PB  - EDP SCIENCES S A
SN  - 00046361
KW  - stars: evolution
KW  - stars: massive
KW  - stars: Wolf-Rayet
KW  - galaxies: dwarf
KW  - galaxies: starburst
KW  - ultraviolet: stars
UR  - https://doi.org/10.1051/0004-6361/202452483
N2  - Context. Chemically homogeneously evolving stars have been proposed to account for several exotic phenomena, including gravitational-wave emissions, gamma-ray bursts and certain types of supernovae. Aims. Here we study whether these stars can explain the observations of the metal-poor star-forming dwarf galaxy, I Zwicky 18. Methods. We apply our synthetic spectral models from Paper II to (i) establish a classification sequence for these hot stars, (ii) predict the photonionizing flux and the strength of observable emission lines from a I Zw 18-like stellar population, and (iii) compare our predictions to all available observations of this galaxy. Results. Adding two new models computed with PoWR, we report that (i) these stars follow a unique sequence of classes: O -> WN -> WO (i.e. without ever being WC). From our population synthesis with standard assumptions, we predict that (ii) the source of the UV C IV lambda 1550 & Aring; and other emission bumps is a couple of dozen WO-type Wolf-Rayet stars (not WC as previously assumed) which are the result of chemically homogeneous evolution, while these, combined with the rest of the O-star population, account for the high He II ionizing flux and the spectral hardness. Contrasting our results against published optical and UV data from the literature and accounting for different aperture sizes and spatial regions probed by the observations, we find that (iii) our models are highly consistent with existing measurements. Conclusions. Since our "massive Pop II stars" might just as well exist in early star-forming regions, our findings have implications for upcoming James Webb Space Telescope (JWST) surveys: the first galaxies in the high-redshift Universe may also experience the extra contribution of UV photons and the kinds of exotic explosions that chemically homogeneous stellar evolution predicts. Given that our results apply for binary populations too as long as the same fraction (10%) of the systems evolves chemically homogeneously, we conclude that the stellar progenitors of gravitational waves may very well exist today in I Zw 18.
ER  -

SZECSI, Dorottya; Frank TRAMPER; Brankica KUBÁTOVÁ; Carolina KEHRIG; Jiri KUBAT; Jiří KRTIČKA; Andreas A. C. SANDER a Miriam GARCIA. Low-metallicity massive single stars with rotation III. Source of ionization and C IV emission in I Zw 18. \textit{ASTRONOMY \&{} ASTROPHYSICS}. LES ULIS CEDEX A: EDP SCIENCES S A, 2025, roč.~703, November, s.~1-18. ISSN~0004-6361. Dostupné z: https://doi.org/10.1051/0004-6361/202452483.

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