Near-Infrared Imaging of M51 and Triggering of Star Formation in the Spiral Arms
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Session 19 -- Gas and Star Formation in Spiral Galaxies
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [19.01] Near-Infrared Imaging of M51 and Triggering of Star Formation in the Spiral Arms

Robert A. Gruendl, Stuart N. Vogel, and Richard J. Rand (University of Maryland)

We present near-infrared mosaics of the grand design spiral M51 obtained with the SQIID and COB arrays at Kitt Peak. Dust lanes, including secondary compression ridges in the interarms, are evident in the color maps. Also, extinction-free images of regions of massive star formation are indicated by K-band peaks which trace the infrared-bright K supergiants. Peaks in the extinction along the dust lanes are well-correlated with the K-band and H$\alpha$\ peaks, confirming that the extinction traces star-forming gas. H$\alpha$\ kinematics obtained with the Maryland-Caltech Fabry-Perot show that the high-extinction regions are produced by density wave compression. Although extinction and H$\alpha$/K-band peaks are well-correlated, the extinction peaks are offset upstream from the regions of recent star formation traced by H$\alpha$\ and K-band. This indicates a time delay between the formation of the clouds causing the extinction and subsequent star formation, and shows that, rather than simply scaling linearly with gas column density, star formation can be triggered by passage through a spiral arm. The extinction is well correlated with velocity-integrated $^{12}$CO $J=1-0$ intensity in the dust lanes, implying that CO traces gas column density and is relatively unaffected by heating from massive stars.