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

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 spax...

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Bibliographic Details
Published in:The Astrophysical journal 2021-01, Vol.906 (1), p.42
Main Authors: Lara-López, Maritza A., Zinchenko, Igor A., Pilyugin, Leonid S., Gunawardhana, Madusha L. P., López-Cruz, Omar, O’Sullivan, Shane P., Feltre, Anna, Rosado, Margarita, Sánchez-Cruces, Mónica, Chevallard, Jacopo, De Rossi, Maria Emilia, Dib, Sami, Fritz, Jacopo, Fuentes-Carrera, Isaura, Garduño, Luis E., Ibar, Eduardo
Format: Article
Language:English
Subjects:
Abundance ratios
Astrophysics
Binary stars
Chemical abundances
Context
Deposition
Emission line galaxies
Ionization
Kinematics
Metallicity
Nebulae
Neutron stars
Optical properties
Parameters
Sciences of the Universe
Spectroscopy
Spiral galaxies
Star formation
Stellar evolution
X ray binaries
X ray stars
X-ray sources
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Summary: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.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/abc892