Circumnuclear star formation in Mrk 42 mapped with Gemini Near-infrared
  Integral Field Spectrograph
  We present Gemini Near-infrared Integral Field Spectrograph (NIFS)
observations of the inner $1.5\times1.5$ kpc$^2$ of the narrow-line Seyfert 1
galaxy Mrk 42 at a spatial resolution of 60 pc and spectral resolution of 40 km
s$^{-1}$. The emission-line flux and equivalent width maps clearly show a ring
of circumnuclear star formation regions (CNSFRs) surrounding the nucleus with
radius of $\sim$500 pc. The spectra of some of these regions show molecular
absorption features which are probably of CN, TiO or VO, indicating the
presence of massive evolved stars in the thermally pulsing asymptotic giant
branch (TP-AGB) phase. The gas kinematics of the ring is dominated by rotation
in the plane of the galaxy, following the large scale disk geometry, while at
the nucleus an additional outflowing component is detected blueshifted by
300-500 kms$^{-1}$, relative to the systemic velocity of the galaxy. Based on
the equivalent width of Br$\gamma$, we find evidences of gradients in the age
of HII regions along the ring of Mrk 42, favoring the pearls on a string
scenario of star formation. The broad component of Pa$\beta$ emission line
presents a Full Width at Half Maximum (FWHM) of $\sim$1480 kms$^{-1}$, implying
in a mass of $\sim\,2.5\times10^{6}$~M$_{\odot}$ for the central supermassive
black hole. Based on emission-line ratios we conclude that besides the active
galactic nucleus, Mrk 42 presents nuclear Starburst activity.
