Kinematic Evidence for Superbubbles in I Zw 18: Constraints on the Star Formation History and Chemical Evolution

We have combined measurements of the kinematics, morphology, and oxygen abundance of the ionized gas in \IZw18, one of the most metal-poor galaxies known, to examine the star formation history and chemical mixing processes.Comment: 31 pages including 6 figures. Accepted for publication in the Astrophysical Journa

Resolving Gas Flows in the Ultraluminous Starburst IRAS23365+3604 with Keck LGSAO/OSIRIS

Keck OSIRIS/LGSAO observations of the ultraluminous galaxy IRAS~23365+3604 resolve a circumnuclear bar (or irregular disk) of semimajor axis 0.42" (520 pc) in Paschen-alpha emission. The line-of-sight velocity of the ionized gas increases from the northeast toward the southwest; this gradient is perpendicular to the photometric major axis of the infrared emission. Two pairs of bends in the zero-velocity line are detected. The inner bend provides evidence for gas inflow onto the circumnuclear disk/bar structure. We interpret the gas kinematics on kiloparsec scales in relation to the molecular gas disk and multiphase outflow discovered previously. In particular, the fast component of the outflow (detected previously in line wings) is not detected, adding support to the conjecture that the fast wind originates well beyond the nucleus. These data directly show the dynamics of gas inflow and outflow in the central kiloparsec of a late-stage, gas-rich merger and demonstrate the potential of integral field spectroscopy to improve our understanding of the role of gas flows during the growth phase of bulges and supermassive black holes.Comment: 14 pages with 7 figures accepted to the astrophysical journa

The ring around SN1987A

Stars in the 9-40 solar mass range play a prominent role in the hydrodynamical and chemical evolution of galaxies. Their stellar winds and supernova explosions are believed to create the hot component of the interstellar medium (ISM). In some galactic disks, the kiloparsec sized super bubbles formed around clusters of massive stars may blow out of the disk plane and release hot, metal enriched gas into the galaxy's halo. Additionally, the expanding shock front of a super bubble in the disk may trigger additional star formation. Furthermore, similar processes probably drive the galactic winds associated with star burst nuclei that enrich the intracluster and intergalactic mediums. Nonetheless, the explosion of a blue super giant in the Large Magellanic Cloud (LMC), SN1987A, illuminated the incompleteness of our understanding of massive stars. Evolutionary models of massive stars do not synthesize the observed super giant populations in either the Milky Way or LMC. Our modeling of the formation of SN1987A's ring will improve our knowledge of both the post-main-sequence evolution of massive stars and their coupling to the ISM in galaxies