Dr. Claudia Cyganowski is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the Harvard-Smithsonian Center for Astrophysics, the National Radio Astronomy Observatory, and the University of Virginia. Massive star formation remains a poorly understood phenomenon, largely due to the difficulty of identifying and studying massive young stellar objects (MYSOs) in the crucial early stage of active accretion. Dr. Cyganowski's research will probe the importance of protostellar feedback in the formation of massive star clusters by observing a unique new sample of MYSOs presently in their active accretion and outflow phase. Identified based on their extended 4.5-micron emission in Spitzer Space Telescope images, these sources are known as Extended Green Objects (EGOs) from the common coding of the 4.5-micron band as green in three-color Spitzer images.
Massive stars generally form in clusters, in distant (>1 kpc) and deeply embedded massive star-forming regions. The high angular resolution and sensitivity of the Expanded Very Large Array (EVLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) at unextincted cm-(sub)mm wavelengths will provide revolutionary new capabilities for MYSO studies. Dr. Cyganowski will use sensitive, high angular resolution cm-sub(mm) line and continuum observations of EGOs to: (1) characterize the masses and clustering properties of compact cores associated with 4.5-micron outflows; (2) constrain the relative importance of different feedback mechanisms (e.g. outflows, heating, ionization); and (3) place EGOs in an evolutionary sequence of massive protostars, relative to each other and to MYSOs from other samples. In sum, the research will use new observational capabilities at cm-(sub)mm wavelengths to address key questions of how protostellar feedback during the formation process affects the masses, number, and clustering properties of the resulting stars, and to assemble a robust observationally-based evolutionary sequence for MYSOs.
Dr. Cyganowski will also broaden science education in rural elementary schools by means of the outreach program "Dark Skies, Bright Kids" (DSBK). DSBK combines an after-school astronomy club for students with onsite night-sky viewing for both students and their families with portable telescopes. Her educational and outreach activities will focus on expanding DSBK to reach students from underrepresented minority groups, through both elementary schools and other organizations, including local Boys and Girls Clubs.
Massive stars dominate our view of galaxies, including our own home, the Milky Way. They do so by injecting tremendous energy into their environments, throughout their lives. While still young, massive stars become hot and luminous enough to ionize the gas around them, producing bright nebulae (HII regions). Massive stars heat their surroundings, and drive powerful winds and outflows. The deaths of massive stars, as gamma ray bursts and supernovae, are among the most energetic events in the universe. Phenomena produced by massive stars account for most of what we can see in distant galaxies, which are our windows into the history of the universe. Despite their importance, the formation and early evolution of massive stars is not well understood. A major roadblock has been identifying very young massive stars that are still growing by accreting gas from their surroundings. Observations of massive star forming regions are also challenging, even within our own galaxy. Massive stars form in dense clouds of gas and dust and so are shrouded from view at optical wavelengths. Observations at longer (infrared to millimeter) wavelengths can penetrate the obscuring layers and detect emission from young massive stars. However, massive star-forming regions, where we can observe the process in action, are distant. As a result, large telescopes or arrays of many telescopes spread over large areas (interferometers) are required to resolve individual forming massive stars. The aim of this project was to study the formation and early evolution of young massive (proto)stars and star clusters. To do so, the Submillimeter Array (SMA) and the Very Large Array (VLA), interferometers operating at (sub)millimeter and centimeter wavelengths, respectively, were used to image the cold dust and gas that participates in the process of star formation. An important outcome of this project was the completion of the SMA Survey of Protocluster Evolution, among the largest millimeter-wavelength interferometric surveys of massive (proto)clusters to date. The design, execution, and analysis of the SMA survey were made possible by this AAPF project. The SMA survey shows that most of the target objects (young massive stars selected to show evidence for ongoing accretion) are forming in the presence of other young massive (proto)stars: in other words, they are (proto)clusters, with at least two massive members. The detected (proto)stars exhibit a striking level of chemical diversity, even within the same (proto)cluster: some (proto)stars are molecule-poor, while others are associated with rich "hot cores" that include complex organic molecules. The range in chemistry (among sources that share many traditional star formation "signposts") indicates that millimeter-wavelength line emission provides a more precise, and powerful, gauge of the evolutionary state of young massive (proto)stars. This project has also yielded significant serendipitous discoveries, including a very unusual "line-free" core. Massive, cold, and exceptionally dense, this core—the best candidate for a massive prestellar core identified to date—shows no line emission at (sub)millimeter wavelengths in extensive SMA observations. The discovery of this unique source continues to provide exciting opportunities to test astrochemical and star formation models. Work is ongoing on the very rich SMA survey dataset, which will be the basis for further publications. Observations and analysis carried out as part of this project also provided the foundation for a successful proposal for Atacama Large Millimeter/Submillimeter Array (ALMA) early science observations. ALMA, a revolutionary new facility now operating in Chile, will provide the sensitivity needed to detect low-mass star-forming cores within the massive (proto)clusters studied with the SMA, answering a key outstanding question about (proto)cluster formation: do the high-mass or low-mass stars form first? The focus of the education and public outreach component of this project was developing an astronomy curriculum for the afterschool program of the Boston-area Science Club for Girls. The Science Club for Girls program engages elementary-school-age students in hands-on science activities, with the aim of closing the achievement gap in STEM fields for young women and broadening participation in STEM fields. This project supported designing, writing, and piloting a curriculum for 5/6th grade students. The broader impacts of this project also included mentoring undergraduate research projects.
