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30 Doradus: The Starburst Next Door

Listing of Poster Abstracts

Anatomy of Starbursts in Extragalactic Giant HII Regions: M51 Case Study
Miss  Jessica Evans (University of Illinois)
Extragalactic giant HII regions (EGHRs) are sites of active, concentrated star formation, and thus provide excellent labs to analyze starburst phenomenon. Although they have been known for a long time, ground-based observations cannot resolve the physical structures and stellar content of EGHRs. The high resolution and sensitivity of Hubble Space Telescope (HST) are ideal for detailed studies of EGHRs. We have searched the Hubble Legacy Archives (HLA) and found 17 nearby galaxies, within ~15 Mpc, with H-alpha and continuum images; to determine the best methods for analyzing these data, we perform an in-depth analysis of the EGHRs in M51. M51 is a face-on spiral galaxy ~8.4 Mpc away, with well-resolved multi-wavelength observations in the HLA. We sample the 25 most luminous HII regions in M51, many of which are bonafide EGHRs with an H-alpha luminosity > 10^39 ergs/s. We use the H-alpha image to study the distribution and physical structure of the gas in each HII region and determine its H-alpha luminosity and required ionizing flux. We use the continuum images to determine whether super stellar clusters (SSCs) are found these HII regions, and use photometric measurements to determine the mass and age spread of the resolved stellar population. These are then compared with the interstellar structures. The results help us provide the groundwork for studying EGHRs in multiple galaxies and elucidate the starburst phenomenon by investigating questions such as: What role does environment play in the formation of EGHRs? How do EGHRs evolve? How does star formation proceed in an EGHR?
Iron-Line Diagnostics in the Extreme Colliding-Wind Binary Eta Carinae
Jean-Christophe Leyder (Goddard Space Flight Center)
Eta Carinae, one of the most peculiar objects in our Galaxy, was the second brightest object in the sky during its eruption in 1843. The large quantities of matter that were ejected at that time are now forming an extended nebula, while Eta Car is still ejecting matter through energetic stellar winds. Eta Car is a colliding-wind binary system: the dense stellar wind coming from the massive luminous blue variable primary star collides with the higher-velocity, lower-density wind from the hotter and luminous (and otherwise unseen) companion star in a highly eccentric orbit. Monitoring observations in the radio, UV, optical, and X-ray domains all indicate an orbital period of 5.5 years. X-ray observations of a colliding-wind binary system such as Eta Carinae provide numerous clues as to the shock physics and mechanisms responsible for particle acceleration and emission in the hydrodynamical shocks that form between the stellar winds. Furthermore, Eta Carinae's long period and high eccentricity provides varying physical conditions, and allow to probe a large parameter space of densities and wind speeds, especially when observing periastron passages where strong variations occur over a short timescale. In my poster, I will present a set of 23 high-resolution X-ray spectra of Eta Carinae obtained by the Chandra satellite, with a particularly detailed coverage around the X-ray minima of 2003.5 and 2009. I will mostly focus on the variations and peculiarities observed in the Fe K line region. The relative intensities of the Fe XXV and Fe XXVI lines provide a diagnostic of the temperature in the apex of the shock, and they vary along the orbital phase. The unexpected presence of a variable “red wing” in the profile of the Fe XXV triplet is also puzzling, and I will suggest possible explanations.
Numerical Simulations of Shocks Encountering Clumpy Regions
Dr.  Julian Pittard (The University of Leeds)
We present numerical simulations of the adiabatic interaction of a shock with a clumpy region containing many individual clouds. We vary the Mach number of the shock, the density contrast of the clouds, and the ratio of cloud mass to inter-cloud mass within the clumpy region. Strong turbulence is generated in the post-shock flow as it sweeps through the clumpy region. Clouds exposed to this turbulence are destroyed more rapidly than a similar cloud in an “isolated” environment.
The Ruby Ring and 30 Doradus: A Comparison of Two Star Cluster Complexes
Jenna Ryon (UW-Madison)
The Ruby Ring (Adamo et al. 2012) is an isolated star cluster complex found in the tidal tail of NGC 2146, a nearby starburst galaxy. This structure consists of a symmetric ring of young clusters coinciding with strong H-alpha emission. A slightly older cluster sits at the center of the ring and has a notable lack of H-alpha. Our HST study of the cluster ages and masses suggests that the "collect and collapse" model may explain the formation of the Ruby Ring. We present a comparison of the properties of the Ruby Ring and 30 Doradus as a step towards understanding star cluster complex formation and evolution. This will be useful for interpreting observations of starburst clumps at high redshift. This work is part of the HST GO-12229 Snapshot Hubble U-band Cluster Survey (SHUCS, PI L. J. Smith).
What the Present Day Mass Function Tells Us About the Massive Stellar Content of Star Clusters
Mr.  Fabian Schneider (Argelander Institute for Astronomy, University of Bonn)
The initial mass function (IMF) gives the distribution of stellar masses at birth and thus governs observable properties of stellar systems, the chemical enrichment of the interstellar medium, supernova rates and predicts the outcome of star formation. It is however impossible to measure the IMF directly because we can only observe the current distribution of stellar masses. We explore the influence of single and binary star evolution on the present day mass function (PDMF) with a rapid binary evolution code. Stellar wind mass loss, mass transfer because of Roche lobe overflow, stellar mergers and rejuvenation shape the PDMF at the high mass end. From this shape it is possible to determine the age of star clusters and to identify the rejuvenated remnants of binary evolution. The most massive stars in a star cluster originate from binary interactions if binary stars have enough time to interact efficiently, i.e. if the star cluster has an age of the order of the MS lifetime of its initially most massive stars. The determination of the stellar upper-mass limit and ages of star clusters based on the most massive stars are thus biased by binary interactions. We apply our findings to the PDMFs of the Arches and Quintuplet clusters and to their nitrogen enriched Wolf Rayet stars. We conclude that single and binary star evolution must be taken into account to better understand the stellar content and the star formation of star clusters.
Studying the Kinematic of the Star-Forming Complex N11
Dr.  Sergio Torres-Flores (Universidad de La Serena)
N11 is the second largest HII in the LMC, after the 30 Doradus nebula and consists of a huge bubble surrounded by several HII regions. Given its proximity, N11 becomes in an ideal laboratory to analyze the kinematic of the ionized gas in a GHR. In this poster, we present high resolution spectra of this region, obtained with the GIRAFFE instrument on the Very Large Telescope. By using this data set, we find that most of the Halpha emission lines in this complex can be fitted by a single Gaussian. We also presents the velocity field and the velocity dispersion map of this region. By adding all the spectra, we derive the integrated Halpha profile of this complex, which displays a width of about 17 km/s (uncorrected by instrumental and thermal width). As can be expected, this width is lower than the value presented by the giant-star forming region of 30 Doradus. Given its evolutionary stage, a comparison of the kinematics of the ionized gas in N11 and 30 Doradus can gives important insights in the understanding of the stellar feedback in giant star-forming regions.