TY - JOUR

T1 - Metal-THINGS

T2 - On the Metallicity and Ionization of ULX Sources in NGC 925

AU - Lara-Lopez, Maritza A.

AU - Zinchenko, Igor A.

AU - Pilyugin, Leonid S.

AU - Gunawardhana, Madusha L. P.

AU - Lopez-Cruz, Omar

AU - O'Sullivan, Shane P.

AU - Feltre, Anna

AU - Rosado, Margarita

AU - Sanchez-Cruces, Monica

AU - Chevallard, Jacopo

AU - Emilia De Rossi, Maria

AU - Dib, Sami

AU - Fritz, Jacopo

AU - Fuentes-Carrera, Isaura

AU - Garduno, Luis E.

AU - Ibar, Eduardo

PY - 2021/1/1

Y1 - 2021/1/1

N2 - 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.

AB - 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.

KW - Emission line galaxies

KW - Ionization

KW - Chemical abundances

KW - Abundance ratios

KW - Spectroscopy

KW - X-ray sources

KW - X-RAY SOURCES

KW - EMISSION-LINE DIAGNOSTICS

KW - STAR-FORMING GALAXIES

KW - SKY SURVEY GALAXIES

KW - SDSS IV MANGA

KW - H-II REGIONS

KW - HOST GALAXIES

KW - SEMIEMPIRICAL ANALYSIS

KW - EFFECTIVE TEMPERATURE

KW - IONIZING STARS

U2 - 10.3847/1538-4357/abc892

DO - 10.3847/1538-4357/abc892

M3 - Journal article

VL - 906

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

M1 - 42

ER -