Metal-THINGS: On the Metallicity and Ionization of ULX Sources in NGC 925

Research output: Contribution to journalJournal articlepeer-review

  • Maritza A. Lara-Lopez
  • Igor A. Zinchenko
  • Leonid S. Pilyugin
  • Madusha L. P. Gunawardhana
  • Omar Lopez-Cruz
  • Shane P. O'Sullivan
  • Anna Feltre
  • Margarita Rosado
  • Monica Sanchez-Cruces
  • Jacopo Chevallard
  • Maria Emilia De Rossi
  • Sami Dib
  • Jacopo Fritz
  • Isaura Fuentes-Carrera
  • Luis E. Garduno
  • Eduardo Ibar

We present an analysis of the optical properties of three Ultra Luminous X-ray (ULX) sources identified in NGC 925. We use Integral field unit data from the George Mitchel spectrograph in the context of the Metal-THINGS survey. The optical properties for ULX-1 and ULX-3 are presented, while the spaxel associated with ULX-2 had a low S/N, which prevented its analysis. We also report the kinematics and dimensions of the optical nebula associated with each ULX using ancillary data from the PUMA Fabry-Perot spectrograph. A BPT analysis demonstrates that most spaxels in NGC 925 are dominated by star-forming regions, including those associated with ULX-1 and ULX-3. Using the resolved gas-phase metallicities, a negative metallicity gradient is found, consistent with previous results for spiral galaxies, while the ionization parameter tends to increase radially throughout the galaxy. Interestingly, ULX-1 shows a very low gas metallicity for its galactocentric distance, identified by two independent methods, while exhibiting a typical ionization. We find that such low gas metallicity is best explained in the context of the high-mass X-ray binary population, where the low-metallicity environment favors active Roche lobe overflows that can drive much higher accretion rates. An alternative scenario invoking accretion of a low-mass galaxy is not supported by the data in this region. Finally, ULX-3 shows both a high metallicity and ionization parameter, which is consistent with the progenitor being a highly accreting neutron star within an evolved stellar population region.

Original languageEnglish
Article number42
JournalAstrophysical Journal
Volume906
Issue number1
Number of pages11
ISSN0004-637X
DOIs
Publication statusPublished - 1 Jan 2021

    Research areas

  • Emission line galaxies, Ionization, Chemical abundances, Abundance ratios, Spectroscopy, X-ray sources, X-RAY SOURCES, EMISSION-LINE DIAGNOSTICS, STAR-FORMING GALAXIES, SKY SURVEY GALAXIES, SDSS IV MANGA, H-II REGIONS, HOST GALAXIES, SEMIEMPIRICAL ANALYSIS, EFFECTIVE TEMPERATURE, IONIZING STARS

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