High-Resolution Imaging of Dense Gas Structure and Kinematics in Nearby Molecular Clouds with the CARMA Large Area Star Formation Survey

This thesis utilizes new observations of dense gas in molecular clouds to develop an empirical framework for how clouds form structures which evolve into young cores and stars. Previous observations show the general turbulent and hierarchical nature of clouds. However, current understanding of the star formation pathway is limited by existing data that do not combine angular resolution needed to resolve individual cores with area coverage required to capture entire star-forming regions and with tracers that can resolve gas motions. The original contributions of this thesis to astrophysical research are the creation and analysis of the largest-area high-angular-resolution maps of dense gas in molecular clouds to-date, and the development of a non-binary dendrogram algorithm to quantify the hierarchical nature and three-dimensional morphology of cloud structure. I first describe the CARMA Large Area Star Formation Survey, which provides spectrally imaged \NtwoH{}, \HCO{}, and HCN ($J=1\rightarrow0$) emission across diverse regions of the Perseus and Serpens Molecular Clouds. I then present a detailed analysis of the Barnard~1 and L1451 regions in Perseus. A non-binary dendrogram analysis of Barnard~1 \NtwoH{} emission and all L1451 emission shows that the most hierarchically complex gas corresponds with sub-regions actively forming young stars. I estimate the typical depth of molecular emission in each region using the spatial and kinematic properties of dendrogram-identified structures. Barnard~1 appears to be a sheet-like region at the largest scales with filamentary substructure, while the L1451 region is composed of more spatially distinct ellipsoidal structures. I then do a uniform comparison of the hierarchical structure and young stellar content of all five regions. The more evolved regions with the most young stellar objects (YSOs) and strongest emission have formed the most hierarchical levels. However, all regions show similar mean branching properties at each level, suggesting that dense gas fragmentation proceeds in a hierarchically similar way from earlier to later stages of star formation. Compared to the more evolved YSOs, the youngest YSOs are preferentially forming within leaves and at high-level locations in dendrogram hierarchies, indicating that dense gas in molecular clouds must reach a state of hierarchical complexity before young stars form efficiently

Morphology and Kinematics of Filaments in the Serpens and Perseus Molecular Clouds

We present H13CO+ (J=1-0) and HNC (J=1-0) maps of regions in Serpens South, Serpens Main and NGC 1333 containing filaments. We also observe the Serpens regions using H13CN (J=1-0). These dense gas tracer molecular line observations carried out with CARMA have an angular resolution of ~7", a spectral resolution of ~0.16 km/s and a sensitivity of 50-100 mJy/beam. Although the large scale structure compares well with the Herschel dust continuum maps, we resolve finer structure within the filaments identified by Herschel. The H13CO+ emission distribution agrees with the existing CARMA N2H+ (J=1-0) maps; so they trace the same morphology and kinematics of the filaments. The H13CO+ maps additionally reveal that many regions have multiple structures partially overlapping in the line-of-sight. In two regions, the velocity differences are as high as 1.4 m/s. We identify 8 filamentary structures having typical widths of 0.03-0.08 pc in these tracers. At least 50% of the filamentary structures have distinct velocity gradients perpendicular to their major axis with average values in the range 4-10 km/s/pc. These findings are in support of the theoretical models of filament formation by 2-D inflow in the shock layer created by colliding turbulent cells. We also find evidence of velocity gradients along the length of two filamentary structures; the gradients suggest that these filaments are inflowing towards the cloud core.Comment: 30 pages, 16 figure

The Structure of Dense Gas in Perseus and Serpens: CLASSy Results

We present results of a dendrogram analysis of N2H+ J=1-0 data cubes from the CARMA Large Area Star-formation Survey (CLASSy). Dendrogram tree structures are characterized by their morphology and kinematics relative to one another, and provide a useful mechanism for analyzing the hierarchy of molecular regions from core-to-cloud spatial scales. Our CARMA data, with 7" spatial and 0.15 km/sec velocity resolution, yield the following results: (1) trees are more hierarchical in regions of high star formation activity; (2) in all regions, the leaf and branch morphology is widely varying and mostly not circularly symmetric; (3) there is evidence for multiple velocity components along a line of sight in only a small fraction of the mapped areas. We compare the identified N2H+ dendrogram tree structures to Herschel maps of dust emission and to Spitzeridentified young stellar object distributions to compare the dense gas distribution to the current star formation activity.Fil: Mundy, Lee G.. University of Maryland; Estados UnidosFil: Storm, Shaye. University of Maryland; Estados UnidosFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Lee, Katherine. University of Illinois; Estados UnidosFil: Looney, Leslie. University of Illinois; Estados UnidosFil: Teuben, Peter J.. University of Maryland; Estados UnidosFil: Rosolowsky, Erik. University of Alberta; CanadáFil: Shirley, Yancy L.. University of Arizona; Estados UnidosFil: Arce, Hector G.. Yale University; Estados UnidosFil: Plunkett, Adele. Yale University; Estados UnidosFil: Isella, Andrea. Caltech; Estados Unidos223th meeting of the American Astronomical SocietyWashingtonEstados UnidosAmerican Astronomical Societ

Dendrogram Analysis of Large-Area CARMA Images in Perseus: the Dense Gas in NGC 1333, Barnard 1, and L1451

We present spectral line maps of the dense gas across 400 square arcminutes of the Perseus Molecular Cloud, focused on NGC 1333, Barnard 1, and L1451. We constructed these maps as part of the CARMA Large Area Star-formation Survey (CLASSy), which is a CARMA key project that connects star forming cores to their natal cloud environment. This is achieved by leveraging CARMA's high angular resolution, imaging capability, and high efficiency at mosaicing large areas of the sky. CLASSy maps capture the structure and kinematics of N2H+, HCN, and HCO+ J=1-0 emission from thousand AU to parsec scales in three evolutionarily distinct regions of Perseus (in addition to two regions in Serpens). We show results from a non-binary dendrogram analysis of the Perseus N2H+ emission, which answers questions about the turbulent properties of the dense gas across evolutionary stages and across the range of size scales probed by CLASSy. There is a flat relation between mean internal turbulence and structure size for the dense gas in NGC 1333 and Barnard 1, but the magnitude of internal turbulence increases with nearby protostellar activity; the dense gas in the B1 main core and NGC 1333, which have active young stars, are characterized by mostly transonic to supersonic turbulence, while the filaments and clumps southwest of the B1 main core, which have no active young stars, have mostly subsonic turbulence. We have recently completed the observations of L1451, and results for that region will be revealed at the meeting. Released CLASSy data products can be found on our project website.Fil: Storm, Shaye. University of Maryland; Estados UnidosFil: Mundy, Lee G.. University of Maryland; Estados UnidosFil: Teuben, Peter J.. University of Maryland; Estados UnidosFil: Lee, Katherine. University of Maryland; Estados UnidosFil: Looney, Leslie. University of Illinois at Urbana; Estados UnidosFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Rosolowsky, Erik. University of Alberta; CanadáFil: Arce, Hector G.. University of Yale; Estados UnidosFil: Shirley, Yancy L.. University of Arizona; Estados UnidosFil: Segura Cox, Dominique. University of Illinois; Estados UnidosFil: Isella, Andrea. Caltech; Estados UnidosFil: CLASSy Collaboration. No especifíca;223rd American Astronomical Society MeetingWashingtonEstados UnidosAmerican Astronomical Societ

Spiral Density Waves in a Young Protoplanetary Disk

Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane. These millimeter-wave observations also reveal an emission gap closer to the star than the spiral arms. We argue that the observed spirals trace shocks of spiral density waves in the midplane of this young disk.Comment: This is our own version of the manuscript, the definitive version was published in Science (DOI: 10.1126/science.aaf8296) on September 30, 2016. Posted to the arxiv for non-commercial us

Kinematics and Temperature Structures of Filaments in Serpens Main and Serpens South

We present a study of filaments in Serpens Main and Serpens South cluster regions based on N2H+(1-0) observations from the CARMA Large Area Star-formation Survey (CLASSy) and dust continuum images from the Herschel Space Observatory. Serpens Main and Serpens South are active star formation regions with prominent filamentary structures; however, the role of the filaments in the cluster formation is unclear. This study of filament structure and kinematics with high-angular resolution data (7 arcsecs), particularly in revealing possible infall signatures, provides physical insight to this question. Using the Herschel data, we estimate the temperature in and along filaments for comparison with their gas kinematics, spatial distribution, and N2H+(1-0) emission, to better understand their role in current star formation activities.Fil: Lee, Katherine. University of Maryland; Estados UnidosFil: Mundy, Lee G.. University of Maryland; Estados UnidosFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Storm, Shaye. University of Maryland; Estados UnidosFil: Looney, Leslie. University of Illinois at Urbana- Champaign; Estados UnidosFil: Segura Cox, Dominique. University of Maryland; Estados UnidosFil: Teuben, Peter J.. University of Maryland; Estados UnidosFil: Rosolowsky, Erik. University of Alberta; CanadáFil: Arce, Hector G.. Yale University; Estados UnidosFil: Shirley, Yancy L.. University of Arizona; Estados UnidosFil: Plunkett, Adele. Yale University; Estados UnidosFil: Isella, Andrea. Caltech; Estados UnidosFil: Tobin, John J.. National Radio Astronomy Observatory; Estados Unidos223th meeting of the American Astronomical SocietyWashingtonEstados UnidosAmerican Astronomical Societ