Investigating H <scp>II</scp> Regions in the Disk of NGC 7331 with the Circumgalactic H <i>α</i> Spectrograph

Abstract We investigate the ionized gas kinematics of H ii regions in the disk of NGC 7331 using integral field unit data collected with the Circumgalactic H α Spectrograph (CH α S). NGC 7331 is a well-studied nearby galaxy with H ii regions resolved by seeing-limited observations, making it ideally suited for this work. The galaxy disk features vigorous star formation, especially in the central ring of starburst activity. We present a catalog of 136 H ii regions detected in the SIRTF Nearby Galaxies Survey (SINGS) H α image. Using this refined catalog, we perform aperture photometry on the SINGS narrowband H α images of NGC 7331, extracting the H α luminosity L (H α ) of these regions. We present corresponding measurements of the average line-of-sight ionized gas velocity dispersion σ in these H ii regions with CH α S. High-resolution velocity and dispersion maps of the galactic disk are produced from the CH α S spectral imaging, selecting spaxels with high signal to noise in order to measure velocity dispersions as low as 12 km s −1 . Our measurements of the L (H α ), Σ SFR , and σ in NGC 7331 are consistent with spatially resolved observations of H ii regions in large surveys of nearby galaxies. We explore the L (H α )– σ relationship, identifying turbulent H ii regions with nonthermal dispersions likely driven by stellar feedback. The dispersion is correlated with the star formation rate surface density, and using the relation <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>σ</mml:mi> <mml:mo>∝</mml:mo> <mml:mi>ϵ</mml:mi> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">Σ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">SFR</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> , H ii regions in NGC 7331 are best fit by ϵ = 80, α = 0.285.