Arp 299 HI paper

A 180 Kpc Tidal Tail in the Luminous Infrared Merger Arp 299

J. E. Hibbard & M. S. Yun, NRAO

The Astronomical Journal, 118, 162 (1999) (pdf) (ADS)

Left: RGB representation of UH88" B-band image (green & yellow) and VLA C+D array HI (blue). Right: Spectral color representation of R-band image with HI contours

We present VLA HI observations and UH88" deep optical B- and R-band observations of the IR luminous merger Arp 299 (= NGC 3690 + IC 694). These data reveal a gas-rich (MHI=3.3E9 Msun) optically faint (mB~27 mag arcsec-2, mR~ 26 mag arcsec-2) tidal tail with a length of over 180 kpc. The size of this tidal feature necessitates an old interaction age for the merger (> 750 Myr since first periapse), which is currently experiencing a very young (< 20 Myr), very intense star burst. The most remarkable characteristic of these observations is that the tidal tail is comprised of two parallel filaments separated by ~ 20 kpc: one gas rich with little if any starlight and the other gas poor. We believe that this bifurcation results from a warped disk in one of the progenitors. The quantities and kinematics of the tidal HI suggest that Arp 299 results from the collision of a retrograde Sab-Sb galaxy (IC 694) and a prograde Sbc-Sc galaxy (NGC 3690) that occurred 750 Myr ago and which will merge into a single object in ~ 60 Myr. We suggest that the present IR luminous phase in this system is due in part to the retrograde spin of IC 694. Finally, we discuss the apparent lack of tidal dwarf galaxies within the tail.

(Previewed in Hibbard & Yun 1996).

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