Large Misalignment between Stellar and Dust Bars in NGC 3488 Revealed by Spitzer and SDSS

A large position angle misalignment between the stellar and dust bars in the late-type barred spiral NGC 3488 was discovered, using mid-infrared images from the Spitzer Space Telescope and optical images from the Sloan Digital Sky Survey (SDSS). The angle between the two distinctive bar patterns was measured to be 25±2, larger than most of the misalignments found previously in barred systems based on Hα or H ii/CO observations. The stellar bar is bright at optical and 3.6μm, while the dust bar is more prominent in the 8μm band but also shows up in the SDSS u and g-band images, suggesting a rich interstellar medium environment harboring ongoing star formation. The angular misalignment between the two bars in NGC 3488 is unlikely to have been caused by spontaneous bar formation. We suggest that the two bars have different formation histories, and that the large misalignment was triggered by a tidal interaction with a small companion. A statistical analysis of a large sample of nearby galaxies with archival Spitzer data indicates that bar structure such as that seen in NGC 3488 is quite rare in the local Universe. Subject headings: galaxies: individual(NGC 3488) — galaxies: spiral — galaxies: structure — infrared: galaxies National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, P. R. China; [email protected], [email protected] Graduate School, Chinese Academy of Sciences, Beijing 100039, China Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 College of Physical Sciences, Graduate School, Chinese Academy of Sciences, P.O. Box 3908, 100039 Beijing, China