Gas excitation in galaxies and active galactic nuclei with HeIIλ4686 and X-ray emission

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F25%3A00619111" target="_blank" >RIV/67985815:_____/25:00619111 - isvavai.cz</a>

Výsledek na webu

<a href="https://hdl.handle.net/11104/0365917" target="_blank" >https://hdl.handle.net/11104/0365917</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202453192" target="_blank" >10.1051/0004-6361/202453192</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Gas excitation in galaxies and active galactic nuclei with HeIIλ4686 and X-ray emission

Popis výsledku v původním jazyce

The origin of He II emission in galaxies remains a debated topic, requiring ionizing photons with energies exceeding 54 eV. While massive stars, such as Wolf-Rayet stars, have been considered potential sources, their UV flux often fails to fully explain the observed He II emission. Recent studies suggest that X-ray binaries (XRBs) might contribute significantly to this ionization. Aims. We explore the relationship between X-ray and He II lambda 4686 emission in a statistically significant sample of galaxies, investigating whether X-ray sources, including active galactic nuclei (AGNs) and XRBs, serve as the primary mechanism for He II ionization across different galactic environments. Methods. We cross-matched a sample of known well-detected He II galaxies with the Chandra Source Catalog, yielding 165 galaxies with X-ray and He II lambda 4686 detections. The sources were classified into star-forming galaxies (SFGs) and AGNs based on the BPT diagram and a classification scheme defined for He II galaxies. We analyzed the correlation between X-ray and He II luminosity across different energy bands and other parameters. Results. The comparison between X-ray and He II luminosity shows a strong, linear correlation across AGNs and SFGs spanning over seven orders of magnitude. AGNs generally exhibit higher He II/H beta flux ratios, stronger extinction, and harder X-ray spectra. The O32 ratio of SFGs is tightly correlated with the H beta equivalent width (EWH beta) but not with the He II/H beta ratio, suggesting a different excitation mechanism. We derive an O32-EWH beta line above which only AGNs of our sample reside. Conclusions. The tight correlation between X-ray and He II luminosity supports X-rays as the primary driver of He II excitation. While AGNs have one common ionization source, the central black hole, in SFGs low-energy species are mainly excited by UV emission related to star-forming activity, however, high-energy species like He II require the presence of XRBs.

Název v anglickém jazyce

Gas excitation in galaxies and active galactic nuclei with HeIIλ4686 and X-ray emission

Popis výsledku anglicky

The origin of He II emission in galaxies remains a debated topic, requiring ionizing photons with energies exceeding 54 eV. While massive stars, such as Wolf-Rayet stars, have been considered potential sources, their UV flux often fails to fully explain the observed He II emission. Recent studies suggest that X-ray binaries (XRBs) might contribute significantly to this ionization. Aims. We explore the relationship between X-ray and He II lambda 4686 emission in a statistically significant sample of galaxies, investigating whether X-ray sources, including active galactic nuclei (AGNs) and XRBs, serve as the primary mechanism for He II ionization across different galactic environments. Methods. We cross-matched a sample of known well-detected He II galaxies with the Chandra Source Catalog, yielding 165 galaxies with X-ray and He II lambda 4686 detections. The sources were classified into star-forming galaxies (SFGs) and AGNs based on the BPT diagram and a classification scheme defined for He II galaxies. We analyzed the correlation between X-ray and He II luminosity across different energy bands and other parameters. Results. The comparison between X-ray and He II luminosity shows a strong, linear correlation across AGNs and SFGs spanning over seven orders of magnitude. AGNs generally exhibit higher He II/H beta flux ratios, stronger extinction, and harder X-ray spectra. The O32 ratio of SFGs is tightly correlated with the H beta equivalent width (EWH beta) but not with the He II/H beta ratio, suggesting a different excitation mechanism. We derive an O32-EWH beta line above which only AGNs of our sample reside. Conclusions. The tight correlation between X-ray and He II luminosity supports X-rays as the primary driver of He II excitation. While AGNs have one common ionization source, the central black hole, in SFGs low-energy species are mainly excited by UV emission related to star-forming activity, however, high-energy species like He II require the presence of XRBs.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10308 - Astronomy (including astrophysics,space science)

Projekt

<a href="/cs/project/GA22-22643S" target="_blank" >GA22-22643S: Galaktická gastronomie: Hrášky a Borůvky</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2025

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Astronomy & Astrophysics

ISSN

0004-6361

e-ISSN

1432-0746

Svazek periodika

696

Číslo periodika v rámci svazku

Apr.

Stát vydavatele periodika

FR - Francouzská republika

Počet stran výsledku

16

Strana od-do

A133

Kód UT WoS článku

001464282900002

EID výsledku v databázi Scopus

2-s2.0-105002693265