Nicole Lea Homeier

Kinematics and Structure of the Starburst Galaxy NGC 7673

The morphology and kinematics of the luminous blue starburst galaxy NGC 7673 are explored using the WIYN (Wisconsin-Indiana-Yale-NOAO) 3.5 m telescope. Signs of a past kinematic disturbance are detected in the outer galaxy; the most notable feature is a luminous ripple located from the center 1@ of NGC 7673. Subarcsecond imaging in B and R —lters also reveals red dust lanes and blue star clusters that delineate spiral arms in the bright inner disk, and narrowband Ha imaging shows that the luminous star clusters are associated with giant H II regions. The Ha kinematics measured with echelle imaging spectroscopy using the WIYN DensePak —ber array imply that these H II regions are con—ned to a smoothly rotating disk. The velocity dispersion in ionized gas in the disk is p D 24 km s~1, which sets an upper boundary on the dispersion of young stellar populations. Broad emission components with p D 63 km s~1 found in some regions are likely produced by mechanical power supplied by massive, young stars; a violent starburst is occurring in a kinematically calm disk. Although the asymmetric outer features point to a merger or interaction as the starburst trigger, the inner disk structure constrains the strength of the event to the scale of a minor merger or weak interaction that occurred at least an outer disk dynamical timescale in the past. Subject headings: galaxies: individual (NGC 7673) ¨ galaxies: ISM ¨ galaxies: kinematics and dynamicsgalaxies: starburstgalaxies: structure

Results from a near infrared search for emission-line stars in the Inner Galaxy: Spectra of new Wolf-Rayet stars

We present follow-up spectroscopy of emission line candidates detected on near-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The filters are optimized for the detection of Wolf-Rayet stars and other objects which exhibit emission-lines in the 2 µm region. Approximately three square degrees along the Galactic plane have been analyzed in seven narrow-filters (four emission-lines and three continuum). We have discovered 4 new Wolf-Rayet stars and present coordinates, finding charts, and K-band spectra.

The star cluster system of the NGC 7673 starburst

We investigate the star cluster system in the starburst galaxy NGC 7673 using archival Hubble Space Telescope WFPC2 broad-band images. For the first time we are able to examine the internal structures of the prominent optical clumps in this galaxy. The clumps are composed of young stars, 16-33% of which are in bright star clusters. We identify 268 star cluster candidates in both the F555W and F814W images, and 50 clusters with the F255W filter. These data allow us to estimate ages and masses using color-magnitude and two-color diagrams for our sample. We find a population of young,<6 Myr clusters located throughout the galaxy with concentrations in the clumps. Star cluster mass estimates are 5-50 10 4 M for the brightest objects. The starburst remains active in physically well-separated regions, indicating a widespread starburst trigger. We discuss clump lifetimes, their implications for the future evolution of NGC 7673, and possible relationships to high redshift starbursts.

A near-infrared survey for Galactic Wolf-Rayet stars

Initial results, techniques, and rationalefor a near-infrared survey of evolved emission-line stars towards the Galactic Center are presented. We use images taken through narrow-band emission-line and continuum filters to select candidates for spectroscopic follow-up. The filters are optimized for the detection of Wolf-Rayet stars and other objects that exhibit emission- lines in the 2 µm region. Approximately three square degrees along the Galactic plane have been analyzed in seven narrow filters (four emission lines and three continuum). Four new Wolf-Rayet stars have been found and are the subject of a following paper.

Morphology and structure of nearby starburst galaxies in the UV and optical

We present results of a panchromatic morphological study to determine how UV and Ho morphology relates to the underlying stellar populations, the ISM, and structure of nearby starbursts.