Intrinsic Bar--Inner Ring Misalignment and a Starburst Nuclear Ring in ESO 565--11

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Session 77 -- Starbursts
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[77.06] Intrinsic Bar--Inner Ring Misalignment and a Starburst Nuclear Ring in ESO 565--11

Guy B. Purcell, R. Buta, and D. A. Crocker (U. Alabama)

Statistical studies of the distributions of apparent inner ring axial ratios and relative bar--inner ring position angles in SB galaxies have indicated that these rings are in general intrinsically oval and are aligned with the bar axis (Buta 1986 ApJS 61, 609). This is consistent with the expectations of $n$-body models of barred spirals, where features resembling inner rings develop from gas gathered into a periodic orbit near the inner 4:1 resonance (Schwarz 1984, MNRAS 209, 93). However, at this time, it is becoming clear that striking exceptions to the rule of alignment exist (see Crocker et al. 1992, BAAS 24, 1123). We have identified the most clear-cut example in the peculiar southern barred spiral ESO 565$-$11 ($\alpha$ = 09$^h$ 27$^m$, $\delta$ = $-$20$^{\circ}$ 10$^{\prime}$, 1950). This remarkable object contains a starburst nuclear ring of colossal proportions, about 4 kpc in diameter, which is lined with giant, luminous HII regions. The ring is the largest nuclear ring (both in linear and relative size) yet observed of more than 60 known examples (Buta and Crocker 1993, AJ 105, 1344). The galaxy also has an unusual bar showing a ``candlepin'' morphology, that is, broad in the middle and tapering off to flat ends. Most interesting is that this bar is neither perpendicular nor parallel to the inner ring major axis, but is misaligned by 56$^{\circ}$, even though the galaxy is not highly inclined. We present deep $BVI$ CCD surface photometry and Rutgers Fabry-Perot velocity maps that conclusively show that the bar--inner ring misalignment is intrinsic to the galaxy. The inner ring is a weak feature at the boundary of a clear oval lens feature. We also suspect that the faint outer ring is intrinsically oval, based on a comparison between the redshift distance and the distance estimated from the Tully-Fisher relation.

Galaxies like ESO 565$-$11 add a new dimension to our understanding of barred galaxies. The cause of the bar--inner ring misalignment is a mystery. We discuss a few mechanisms for misalignment, including a tidal interaction and different pattern speeds for the bar and spiral structure. The photometric properties of the nuclear ring are also discussed.

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