Extreme gas kinematics in an off-nuclear HII region of SDSS J143245.98+404300.3

Del Pino, B. R., Arribas, S., López, J. P., Gómez, A. C., Vilchez, J. M. 2019. Extreme gas kinematics in an off-nuclear HII region of SDSS J143245.98+404300.3. Astronomy and Astrophysics 630 DOI: 10.1051/0004-6361/201936140

We present and discuss the properties of an ionized gas component with extreme kinematics in a recently reported off-nuclear HII region located at similar to 0.8-1.0 kpc from the nucleus of SDSS J143245.98+404300.3. The high-velocity-gas component is identified by the detection of very broad emission wings in the H alpha line, with full width at half maximum (FWHM) >= 850-1000 km s(-1). Such gas kinematics are outstandingly high compared to other HII regions in local galaxies and are similar to those reported in some star-forming clumps of galaxies at z similar to 2. The spatially resolved analysis indicates that the high-velocity gas extends at least similar to 90 pc and it could be compatible with an ionized outflow entraining gas at a rate between approximately seven and nine times faster than the rate at which gas is being converted into stars. We do not detect broad emission wings in other emission lines such as H beta, perhaps due to moderate dust extinction, nor in [NII]lambda lambda 6548, 6584 or [SII]lambda lambda 6717, 6731, which could be due to the presence of turbulent mixing layers originated by the impact of fast-flowing winds. The lack of spectral signatures associated to the presence of Wolf-Rayet stars points towards stellar winds from a large number of massive stars and/or supernovae as the likely mechanisms driving the high-velocity gas.

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