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30 Doradus: The Starburst Next Door

Listing of Talk Abstracts

The Stellar Initial Mass Function: 30-Doradus and Beyond
Daniela  Calzetti  (Department of Astronomy, University of Massachusetts)
The resolved central cluster R136 has offered unprecedented opportunities to probe the stellar Initial Mass Function (IMF) in a very young cluster. However, relatively few young clusters offer the same possibility of being resolved into individual stars, while being massive enough to fully sample the IMF. This has spurred the search for methods to constrain the stellar IMF under unresolved conditions. I review one such method, and the results obtained from the analysis of two nearby galaxies: M51 and NGC4214.
30 Doradus: Just How Unusual Is It?
You-Hua Chu (University of Illinois)
What makes 30 Dor fascinating is its intense star formation and violent energy feedback. Just how unusual is 30 Dor? I will compare 30 Dor to other star-forming complexes in the Large Magellanic Cloud and giant HII regions in other galaxies in terms of star formation properties (distribution, history, and massive YSOs) energy feedback effects (kinematics and physical conditions of the interstellar gas). The comparisons may help us gain insight into the physical processes that produce giant HII regions like 30 Dor.
Census of the Hot, Luminous Stellar Population of 30 Doradus: Radiative and Mechanical Feedback
Prof.  Paul Crowther (University of Sheffield)
In this review I provide an overview of the hot, luminous stellar population of the supergiant HII region 30 Doradus, based largely upon the VLT-FLAMES Tarantula Survey (VFTS, Evans et al. 2011), supplemented by Hubble Space Telescope spectroscopy of the central R136a cluster (e.g. Massey & Hunter 1998). The global radiative and mechanical energy budget from OB, Of/WN and Wolf-Rayet stars in 30 Doradus is calculated, and compared with empirical results. The contribution from the most massive stars in R136a is also highlighted.
Recent Developments in Our Understanding of Mass-Loss From Massive Stars
Prof.  Alex de Koter  (University of Amsterdam )
The evolution of massive stars and the characteristics of their supernova explosions are greatly affected by the amount of mass and angular momentum lost during their lifetime. An important mass-loss mechanism, at least at galactic and Magellanic Cloud metallicities, is the transfer of momentum from photons to the atmospheric gas through line interactions, initiating and driving an outflow. The 30 Doradus region in the Large Magellanic Cloud is so rich in massive stars that it provides meaningful samples of morphological sub-groups, representing a sequence of evolutionary epochs. In particular, this allows to study whether O- and WNh-star winds share the same driving mechanism, even though the mass-loss rates of the WNh stars are known to be much higher than of the O stars. Understanding this connection may provide new insights in the winds of stars up to hundreds of solar masses. We also present recent empirical and theoretical results regarding other aspects of line-driven winds, including the cause of the so-called 'weak wind problem' (Muijres et al. 2012) and the unexpected behavior of stellar wind strengths at sub-SMC metallicities (Tramper et al. 2011).
The Evolution of Massive Stars 30 Dor Under the Influence of Rotation and Binary Interaction
Dr.  Selma E. de Mink (STScI / JHU)
With their large luminosities, strong stellar winds and spectacular explosions massive stars heat and enrich their surroundings, where the next generation of stars are forming. With its rich stellar populations, 30 Doradus is an excellent laboratory to investigate major outstanding questions concerning the evolution of massive stars. I will discuss recent progress in modeling the evolution of massive stars in the context of the VLT-FLAMES Tarantula Survey of Massive Stars addressing in particular questions related to the effects of rotation and binarity.
The VLT-FLAMES Tarantula Survey
Dr.  Chris Evans (UK Astronomy Technology Centre)
The VLT-FLAMES Tarantula Survey has obtained multi-epoch optical spectroscopy for over 800 massive stars in 30 Doradus. I will introduce the survey, and present selected highlights from the first papers.
30 Doradus: A Giant Among Local Star-Forming Complexes?
Jay  Gallagher (University of Wisconsin-Madison)
The 30 Dor region offers a unique opportunity to explore the internal workings of a massive young stellar context. Although rare, these types of regions exist in a variety of nearby galaxies that cover a range in structure, mass and environment, suggesting that massive star-forming complexes owe their origin to special local conditions in the ISM. Comparisons between 30 Dor and other giant extragalactic star forming regions can be made, e.g., in terms of HII region sizes and luminosities; properties of massive stellar populations; star cluster masses and mass fractions; or relationships with associated molecular clouds. Although none of these indicators give complete pictures of these spectacular objects, they reveal properties ranging from those of up-scaled versions of relatively normal star forming regions to starburst systems. In this talk I compare 30 Dor with nearby extragalactic analogs, and discuss how these systems fit into our developing models for intensely star-forming regions and their starburst clump relatives.
Low-Mass Pre-Main Sequence Stars: A Treasury of Information on Clustered Star Formation in the Magellanic Clouds
Dr.  Dimitrios Gouliermis (MPIA, ZAH/ITA Heidelberg)
The best places to observe the formation and early evolution of stellar clusters and associations are HII regions, the natal environments of these systems. Low-mass stars in such regions are still in their pre--main-sequence (PMS) evolutionary phase, and while being faint they can be efficiently detected (down to the sub-solar mass regime) in the Magellanic Clouds with the Hubble Space Telescope due to the low extinction and stellar field contamination. The Tarantula nebula being the most exciting of all HII regions in the Local Group, is possibly the best place to study clustered star formation in the Clouds through their low-mass PMS stars, but the investigation of other more quiescent star-forming regions provide a unique comparative sample of such objects. I will outline the most recent developments in the investigation of PMS stars in the Magellanic Clouds, as they are revealed with HST imaging, in terms of a comparative analysis between the straburst of 30 Doradus (from data from the literature) and "milder" star-forming regions of the Clouds, as investigated by us.
The Dynamics of R136
Mr.  Vincent Henault-Brunet (Institute for Astronomy, University of Edinburgh)
I will present recent results on the dynamics of R136 based on multi-epoch radial velocity measurements obtained as part of the VLT-FLAMES Tarantula Survey. First, a low velocity dispersion of ~5 km/s was measured when selecting out binaries, implying that the cluster is in dynamical equilibrium from a very young age. Then, evidence was found for rotation of the cluster with a rotational velocity of ~3 km/s, suggesting that star clusters may form with at least 20% of the kinetic energy in rotation.
ALMA's View of Molecular Gas in 30 Doradus
Remy Indebetouw (University of Virginia)
30 Doradus is the nearest super-star cluster, and an ideal laboratory in which to study the effects of vigorous star formation on molecular gas in galaxies. We present observations of the northern molecular cloud in 30 Doradus, showcasing the power of ALMA, even in early science, to understand detailed physical conditions in extragalactic multiphase interstellar media. We image the cloud in the most commonly used extragalactic dense gas tracers including HCN, HCO+, CS, and CO. We study in detail the properties of dense starless and starforming clumps and cores in the cloud, and conditions in the interclump medium. In combination with Spitzer, Herschel, and other data, we can obtain a highly detailed picture of physical conditions in a real starburst PDR at reduced metallicity for the first time. These detailed studies are important to inform the interpretation of many ALMA observations of PDRs and molecular gas in more distant galaxies.
A Study of Stellar Feedback in 30 Doradus
Dr.  Laura Lopez (Massachusetts Institute of Technology)
Observations show that star formation is an inefficient and slow process. This result can be attributed to the injection of energy and momentum by stars that prevents the free-fall collapse of molecular clouds. The mechanism of this stellar feedback is debated theoretically; possible sources of pressure include the classical warm HII gas, the hot gas generated by shock heating from stellar winds and supernovae, direct radiation of stars, and the dust-processed radiation field trapped inside an HII shell. In this talk, I will present recent work to measure observationally the pressures associated with each of these components across the giant HII region 30 Doradus. We exploit high-resolution, multi-wavelength images (radio, infrared, optical, and X-ray) to map these pressures as a function of position. I will compare the 30 Dor results to those from analysis of a large sample of Magellanic Cloud HII regions, and I will consider the implications regarding the dynamics and regulation of star formation in 30 Dor.
The 30 Doradus Optical/NIR Extinction Law
Dr.  Jesús Maíz Apellániz (IAA-CSIC)
We have generated a new one-parameter family of optical/NIR extinction laws intended to replace the Cardelli et al. (1989) family that yield significantly lower chi^2 residuals when fitting stellar models to optical-NIR photometry. The new laws have been obtained using two state-of-the-art surveys: the VLT-FLAMES Tarantula Survey, which obtained high-resolution spectra of ~1000 stars in 30 Doradus, and the WFC3-ERS survey, which obtained HST multiband photometry of a number of starburst regions, including 30 Doradus. Hence, our input data clearly surpass in quality and quantity the photometry and spectral types used by Cardelli et al. to derive their extinction laws almost a quarter of a century ago. Even though obtained for 30 Doradus, we have positively tested their applicability to Galactic stars (the main differences between the MW, LMC, and SMC extinction laws occur in the UV, not in the optical/NIR). The new family of extinction laws solve two outstanding problems: the failure of the Cardelli et al. laws to accurately describe the Strömgren colors and indices for highly extinguished stars and the inability of optical/NIR photometry to determine effective temperatures of massive hot stars.
VFTS 682: An Isolated Twin of the R136a WN5h Massive Stars
Dr.  Francisco Najarro (Centro de Astrobiologia CSIC-INTA)
We will present first results from our VLT-XSHOOTER multiwavelength observations of the reddened, massive WN5h star VFTS#682, covering from the optical to the NIR.
Star Formation in 30 Doradus
Prof.  Nino Panagia (STScI)
Using observations obtained with the HST-WFC3 we have studied the properties of the stellar populations in the central regions of 30 Dor in the Large Magellanic Cloud. We have searched for pre-main-sequence (PMS) stars by selecting objects with a strong (>4σ) Hα excess emission and find about 1150 of them over the entire field. We have determined their physical parameters (effective temperature, luminosity, mass, and age) by comparing their locations in the HR diagram with theoretical PMS evolutionary tracks. We find that about one-third of these objects are younger than 4 Myr, compatible with the age of the massive stars in the central ionizing cluster R 136, whereas the rest have ages up to 30 Myr, with a median age of 12 Myr. This indicates that star formation has proceeded over an extended period of time. While the younger PMS population preferentially occupies the central regions of the cluster, older PMS objects are more uniformly distributed across the field and are remarkably few at the very center of the cluster. We attribute this latter effect to photo-evaporation of the older circumstellar disks caused by the massive ionizing members of R 136. For all PMS stars we also determined the mass accretion rates from the luminosity of their H-alpha emission. We find values that are up to an order of magnitude higher than for galactic PMS stars with similar masses and ages but which are comparable to the ones determined for PMS stars in other young regions in the LMC and SMC.
The Feedback, Pressure and Energy Ballance in 30 Doradus
Dr.  Eric Pellegrini (University of Toledo)
Using photoionization models with observatinal data we probe the physical conditions and ionization mechanisms at more than 4000 individual lines of sight in 30 Doradus inorder to probe the feedback mechanisms and derive the nebular equation of state. We focus on the geometry and importance of radiation pressure on a point-by-point basis, with the aim of setting observational constraints on important feedback processes. We find that the dynamics and large scale structure of 30 Dor are set by a confined system of X-ray bubbles in rough pressure equilibrium with each other and with the confining molecular gas. Although the warm (10,000K) gas is photoionized by the massive young stars in NGC 2070, the radiation pressure does not currently play a major role in shaping the overall structure.
The Magnetic OB Star Population in Our Galaxy and Beyond
Dr.  Veronique Petit (West Chester University)
Massive star magnetism is often considered an astronomical "wildcard", as it is hard to predict in which stars it may occur. This reflects our fundamental ignorance of the origin of massive star magnetism, and compels us to better understand the scope of its influence on massive stars individually, and also as a population. Over the past 5 years, the Magnetism in Massive Stars (MiMeS) Collaboration has been seeking out magnetic massive stars in the Galaxy, to better understand their origins, physical properties, and how they influence observable stellar characteristics. In this talk, we review the general properties of OB star magnetism in the Galaxy, using recent MiMeS discoveries as examples. It is now clear that the magnetic properties of massive stars are established early in their evolution. This raises interesting and fundamental questions about the physics of stellar formation and connections with stellar magnetism. We discuss the importance of rich and young clusters (like 30 Dor!) as laboratories for exploring field origin physics, and to what extent massive star magnetism may be an important consideration in the LMC. Indeed, MiMeS observations have established that about 1 in 15 Galactic OB stars hosts a magnetic field that is sufficiently strong to significantly influence its atmospheric and wind structure. Could your own mysterious and perplexing 30 Dor OB target be a magnetic massive star? To aid answering this question, we review many of the outstanding or exotic properties exhibited by known magnetic OB stars that relate directly to their magnetic nature. Finally, we explain how current and next-generation spectroscopic and spectropolarimetric instrumentation can provide a window to understanding massive star magnetism in the LMC.
The Effects of Winds and Supernovae on Clumpy Media
Dr.  Julian Pittard (The University of Leeds)
Energy input from massive stars into the interstellar medium drives high Mach number flows into and through clumpy regions. Simulations of stellar winds and supernovae from massive stars embedded in an inhomogeneous medium are presented. The time for dense material to be cleared from the local cluster environment is examined, and the time-history of the mass and energy flux into the wider medium is determined with a view for use in larger-scale models. Some preliminary X-ray calculations will also be shown.
Seeing Double in 30 Doradus
Dr.  Elena Sabbi (STScI)
We have identified two distinct stellar populations in the core of the giant HII region 30 Doradus using data obtained with the Wide Field Camera 3 on the Hubble Space Telescope. The richest and most compact component coincides with the center of R136 and is ~1Myr younger than the second, more diffuse clump, located toward the northeast. The morphology and age difference between the two components suggests that a merger may be occurring within the core of 30 Doradus. We will discuss this finding in the context of massive cluster formation and evolution.
(Preliminary) Multiplicity and Rotational Properties of Massive Stars Populations in 30 Doradus
Dr.  Hugues Sana (University of Amsterdam)
The VLT-Flames Tarantula Survey has acquired intermediate resolution spectroscopy of over 800 OB stars in the 30 Doradus. The multi epoch approach allow us to identify spectroscopic binaries with periods up to about one year. Using Monte Carlo simulations to model the observational biases we constrain the intrinsic multiplicity properties of the O- and B-type star populations. We also obtain measurements of the projected rotational velocities of the single OB stars in our sample and we derive the distribution of the equatorial velocities. I present an overview of our results and discuss them in the context of massive star evolution and their implications for the final fate of massive stars.
On the Nature of O Vz Stars in 30 Doradus
Dr.  Sergio Simon-Diaz (Instituto de Astrofisica de Canarias)
Preference: Session III. Star Clusters and Stellar content The VLT-FLAMES Tarantula Survey (VFTS) has found a large number of O Vz stars among the young massive stellar population of 30 Dor. The nature of these stars, displaying HeII 4686 absorption stronger than any other He II or He I line, is unknown, as their structural differences to standard O V stars. They have been previously hypothesized on spectroscopic grounds to be on or very near the ZAMS. If confirmed, O Vz stars would provide new insight of the very early evolutionary phases of massive stars. In this talk, we present the main results from a quantitative spectroscopic analysis of a sample of ~100 O main-sequence stars in 30 Dor (40 O Vz stars, plus 60 O V stars used for comparison). This study aims at quantitatively investigating the properties empirically assigned to the O Vz stars, i.e., being younger and having lower luminosity, higher gravity, and/or lower mass-loss rate than normal class V.
Interpreting X-ray Emission From the Most Massive Stars
Dr.  Jon Sundqvist (University of Delaware)
Orbiting satellites since Einstein have established that the X-ray luminosity of "normal" O-stars scales linearly as Lx ~ 10^-7 Lbol. We show here that this relationship can be understood by radiative embedded wind-shocks that mix under the influence of thin-shell instabilities. But extending this theory to also very massive stars, that are optically thick to bound-free absorption of X-rays, implies a saturation or even decline in the emergent X-ray luminosity. This suggests that some other mechanism may be responsible for the observed X-rays in the most massive WNH-stars in 30 Doradus, for example radiative shocks originating in wind-wind collisions of undetected close binary stars. Such colliding wind shocks should themselves be subject to thin-shell mixing.
The Formation of Massive Stars and Star Clusters - Recent Insights from the Galaxy
Prof.  Jonathan C. Tan (University of Florida)
I review the processes of massive star and star cluster formation and their associated open questions. A number of major issues are still debated, including: What is the accretion mechanism of massive stars? What sets the stellar initial mass function? What are the initial conditions for star cluster formation, especially massive star clusters, and how do they arise? What is the duration of star cluster formation and how is it influenced by stellar feedback? I describe theoretical models relevant to these questions and how they are being tested by recent observations of nearby Galactic systems.
A Kinematic Study of the Giant Star-Forming Region of 30 Doradus
Dr.  Sergio Torres-Flores (Universidad de La Serena)
Kinematically, giant HII regions (GHR) are known to display supersonic emission-line widths and large expanding structures. However, the main physical mechanism that produces these phenomena is still uncertain. In order to address these problems, we have obtained high resolution spectroscopic data of the GHR 30 Doradus, by using the instrument GIRAFFE on the Very Large Telescope at Paranal observatory. This new data set consists of a nebular regular, a nebular irregular and a stellar grid. We have used the nebular regular grid to derive a spectroscopic data cube of 30 Doradus, which was centered on R136 and covers a field of view of 10'x10'. The main emission lines present in this data cube correspond to [NII] 6548 A, Halpha, and [NII] 6584 A. By inspecting this data cube, we find that the Halpha emission line displays simple and multiple profiles at different locations, which suggests that different physical mechanisms act in different ways on the excited gas in 30 Doradus. In order to analyze the kinematics of 30 Doradus, we fit Gaussian to the observed Halpha profiles. We found that the narrowest Halpha profile in our field of view in 30 Doradus lies close to the SN remnant 30 Dor B. Also, we find three unclassified expanding structures and we derive the velocity field and velocity dispersion map of 30 Doradus. Finally, we found a low-intensity broad component in the integrated Halpha profile of 30 Doradus, as previously found by other authors.
Live Fast, Die Young, Blow Some Bubbles: The X-ray View of 30 Doradus from Chandra
Dr.  Leisa Townsley (Penn State University )
During their short lives, massive stars are the movers and shakers in star-forming regions, quickly modifying their birth environments via their ionizing radiation and powerful winds and finally destroying themselves and their natal clouds in supernovae, enriching neighboring young stellar disks with processed materials and blowing superbubbles that shape their surroundings on 100-pc scales. 30 Doradus is the result of many generations of massive star influence and X-ray observations reveal the high-energy impact of these massive stars and their ISM feedback. I will report on Chandra observations of 30 Dor and a few of its Galactic cousins, the younger and lower-mass stepping stones that we use to infer the inner workings of this great Local Group Giant.
The Current and Future Massive Stellar Generations in 30 Doradus
Dr.  Nolan Walborn (STScI)
Some characteristics of the most massive ionizing population of 30 Doradus from VLT-FLAMES Tarantula Survey spectroscopy, and of the triggered second generation from Spitzer/VISTA images, will be presented.