479 research outputs found
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
The Kinematics of CIV in Star-Forming Galaxies at z~1.2
We present the first statistical sample of rest-frame far-UV spectra of
star-forming galaxies at z~1. These spectra are unique in that they cover the
high-ionization CIV{\lambda}{\lambda}1548, 1550 doublet. We also detect
low-ionization features such as SiII{\lambda}1527, FeII{\lambda}1608,
AlII{\lambda}1670, NiII{\lambda}{\lambda}1741, 1751 and SiII{\lambda}1808, and
intermediate-ionization features from AlIII{\lambda}{\lambda}1854, 1862.
Comparing the properties of absorption lines of lower- and higher- ionization
states provides a window into the multi-phase nature of circumgalactic gas. Our
sample is drawn from the DEEP2 survey and spans the redshift range 1.01 < z <
1.35 ( = 1.25). By isolating the interstellar CIV absorption from the
stellar P-Cygni wind profile we find that 69% of the CIV profiles are
blueshifted with respect to the systemic velocity. Furthermore, CIV shows a
small but significant blueshift relative to FeII (offset of the best-fit linear
regression -76 26 km/s). At the same time, the CIV blueshift is on
average comparable to that of MgII{\lambda}{\lambda}2796, 2803. At this point,
in explaining the larger blueshift of CIV absorption at the ~ 3-sigma level, we
cannot distinguish between the faster motion of highly-ionized gas relative to
gas traced by FeII, and filling in on the red side from resonant CIV emission.
We investigate how far-UV interstellar absorption kinematics correlate with
other galaxy properties using stacked spectra. These stacking results show a
direct link between CIV absorption and the current SFR, though we only observe
small velocity differences among different ionization states tracing the
outflowing ISM.Comment: 21 pages, 14 figures, ApJ, accepte
- …