Near--Infrared Imaging of the Starburst Ring in UGC12815

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Session 40 -- Starburst Galaxies
Display presentation, Wednesday, June 14, 1995, 9:20am - 6:30pm

[40.04] Near--Infrared Imaging of the Starburst Ring in UGC12815

D.A. Smith (NRC/NASA/GSFC/Cornell U.), T. Herter, M.P. Haynes (Cornell U.), S.G. Neff (NASA/GSFC/LASP)

Starburst galaxies define an enigmatic class of objects undergoing a brief, intense episode of star formation. In order to investigate the nature of nearby starbursts, we have analyzed the 20 starburst galaxies with the highest 4.85 GHz luminosities from the survey of Condon, Frayer, \& Broderick (1991, AJ, 101, 362) at infrared and optical wavelengths. As part of our study, we recently used the Cassegrain Infrared Camera at the Hale 5 m telescope to obtain high spatial resolution near--infrared images of the cores of 17 of these galaxies in order to better understand the starburst triggering mechanism. We find that one galaxy, UGC12815 (NGC7771), possesses a nucleus surrounded by a bright starburst ring.

We present 1.25, 1.65, and 2.2 $\mu$m ($J$, $H$, and $K$ band) images of the nuclear region of UGC12815 and a preliminary analysis of the properties of the starburst ring. The resolution of our $K$ band image is $0.6^{\prime\prime}$ FWHM. The ring is $\sim 1.6$ kpc ($6^{\prime\prime}$) in diameter assuming $H_0=75$ km/s/Mpc; several knots are detected in the ring at 2.2 $\mu$m. The spatial distribution of these knots is compared to that observed at 6 cm. The luminosities of the ring and nucleus, as mapped in the near--infrared and radio, are also discussed. Color maps ($H-K$ and $J-H$) constructed from the near--infrared images trace the relative roles of extinction, and emission from evolved red stars, blue stars, thermal gas, and hot dust in the nucleus and starburst ring. A comparison between UGC12815 and other systems with circumnuclear starbursts is also made.

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