Evidence for a Galactic Wind and a Peculiar Triaxial Bulge

We present new optical imaging and spectroscopy of the peculiar, edge-on Sbc galaxy UGC 10043. Using the WIYN telescope, we have obtained B, R, and Hα+[N ii] images, together with DensePak integral field spectroscopic measurements of the stellar Ca ii infrared triplet and the Hα and [N ii] lines from the ionized gas. The imaging observations show that the inner bulge of UGC 10043 (a ≤7 .5) is elongated perpendicular to the galaxy major axis. At larger r, the bulge isophotes twist to become oblate and nearly circular, suggesting the bulge is triaxial. The bulge shows no clear evidence for rotation about either its major or minor axis. The inner, southwestern quadrant of the bulge is girdled by a narrow dust lane parallel to the minor axis; unsharp masking reveals that this minor axis dust lane may be part of an inner polar ring, although we find no unambiguous kinematic evidence of orthogonally rotating material. The stellar disk of UGC 10043 has a rather low optical surface brightness [μ(0)R,i ∼23.2 mag arcsec ], a small scale height (hz = 395 pc for D = 33.4 Mpc), and a mild integral sign warp. A dusty, inner disk component that appears tilted relative to the outlying disk is also seen. The Hα and [N ii] emission lines in UGC 10043 resolve into multiple velocity components, indicating the presence of a large-scale galactic wind with an outflow velocity of Vout >∼104 km s . Hα+[N ii] imaging reaffirms this picture by revealing ionized gas extended to |z| ∼3.5 kpc in the form of a roughly biconical structure. The [N ii]/Hα line intensity ratio increases with increasing distance from the plane, reaching values as high as 1.7. Unlike most galaxies with large-scale winds, UGC 10043 has only a modest global star formation rate ( <∼1M⊙ yr ), implying the wind is powered by a rather feeble central starburst. We discuss evolutionary scenarios that could account for both the structural complexities of UGC 10043 and its large-scale wind. The most plausible scenarios require a major accretion or merger event at least a few Gyr ago. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 USA, Electronic mail: [email protected] Visiting Astronomer, Kitt Peak National Observatory. National Optical Observatories is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation. Department of Physics & Astronomy, the University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom, Electronic mail: [email protected]