Dense gas kinematics in the massive G351.77 protocluster ALMA-IMF Large Program observations of N2H+.
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Date
2024
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Publisher
Universidad de Concepción
Abstract
El ALMA-IMF Large Program observó 15 protocúmulos masivos en la Bandas 3 y 6, capturando multiples lineas y emisiones de continuo. Aquí estudiamos el protocumulo filamentoso masivo G351.77, ubicado a una distancia de 2 kpc.
Trazamos la emisión del gas denso y la cinemática a través de la línea N2H+ (1-0) de 3 mm. Para recuperar la emisión, combinamos y reducimos los arreglos de 12m y 7m para luego fusionarlos con los datos de Total Power, obteniendo una imagen que captura la emisión de N2H+ sobre el protocúmulo a una resolución de 4 kUA. Modelamos el perfil de línea hiperfina de N2H+ con PySpecKit con dos componentes de velocidad, obteniendo el excitation temperature (Tex), optical depth ( ), centroid velocity (v), y line width ( (V )) para cada componente. En combinación con el optical depth y un mapa de columna de densidad de H2 derivado de los datos de 1.3 mm, medimos la abundancia relativa de N2H+ (1.66 ± 0.46) × 10−10. Estimamos una masa total de H2 1660 ± 458 M derivado de la emisión de N2H+ en el protocúmulo. Examinando los diagramas de posición-velocidad a pequeñas escalas, observamos claras señales de inflow asociados a los cores de la banda de 1.3 mm. En algunos casos, señales similares fueron observadas sin cores detectados, sugiriendo la existencia de cores por debajo del límite de detección de la banda de 1.3 mm. La señal más prominente, con forma de "V" (V-shape), tiene un promedio de mass inflow rate 4.08 × 10−4 M /yr y un promedio en timescale 20.92 kyr. Nuestro analisís revela que multiples componentes de velocidad impregnan el protocúmulo, lo que indica una compleja cinemática en el gas denso. El diagrama de posición-velocidad a grandes escalas muestra que el filamento que hospeda al protocúmulo es separado en 2 estructuras de velocidad, las cuales parecen estar rotando entre si, mientras fluyen hacia regiones más densas de N2H+. Además, sus timescales de acumulación de masa alcanzan 20 kyr.
The ALMA-IMF Large Program observed 15 massive protoclusters in Band 3 and 6, capturing multiple lines and continuum emission. Here we study the massive filamentary protocluster G351.77, located at a distance of 2 kpc. We trace the dense gas emission and kinematics via the N2H+ (1-0) 3 mm line. To recover the emission, we combine and reduce the 12m-array and 7m-array to then be feathered with Total Power data, obtaining an image that captures the N2H+ emission over the protocluster at 4 kAU resolution. We model the N2H+ hyperfine line profile with PySpecKit with two velocity components, obtaining the excitation temperature (Tex), optical depth ( ), centroid velocity (v), and line width ( (V )) for each component. In combination with the optical depth and an H2 column density map derived from the 1.3 mm data, we measure the N2H+ relative abundance (1.66 ± 0.46) × 10−10. We estimate a total H2 mass 1660 ± 458 M derived from the N2H+ emission in the protocluster. By examining the position-velocity diagrams at small scales, we observe clear inflow signatures associated with 1.3 mm band cores. In some cases, similar signatures were observed without detected cores, suggesting the existence of cores below the 1.3 mm band detection limit. The most prominent signature, shaped like a "V" (V-shape), has an average of mass inflow rate 4.08 × 10−4 M /yr and an average timescale 20.92 kyr. Our analysis reveals that multiple velocity components pervade the protocluster, indicating kinematic complexity in the dense gas. The large-scale position-velocity diagram shows that the filament hosting the protocluster is separated into 2 velocity structures, which appear to be rotating around each other, while they inflow towards denser N2H+ regions. Additionally, their mass buildup timescales that reach 20 kyr.
The ALMA-IMF Large Program observed 15 massive protoclusters in Band 3 and 6, capturing multiple lines and continuum emission. Here we study the massive filamentary protocluster G351.77, located at a distance of 2 kpc. We trace the dense gas emission and kinematics via the N2H+ (1-0) 3 mm line. To recover the emission, we combine and reduce the 12m-array and 7m-array to then be feathered with Total Power data, obtaining an image that captures the N2H+ emission over the protocluster at 4 kAU resolution. We model the N2H+ hyperfine line profile with PySpecKit with two velocity components, obtaining the excitation temperature (Tex), optical depth ( ), centroid velocity (v), and line width ( (V )) for each component. In combination with the optical depth and an H2 column density map derived from the 1.3 mm data, we measure the N2H+ relative abundance (1.66 ± 0.46) × 10−10. We estimate a total H2 mass 1660 ± 458 M derived from the N2H+ emission in the protocluster. By examining the position-velocity diagrams at small scales, we observe clear inflow signatures associated with 1.3 mm band cores. In some cases, similar signatures were observed without detected cores, suggesting the existence of cores below the 1.3 mm band detection limit. The most prominent signature, shaped like a "V" (V-shape), has an average of mass inflow rate 4.08 × 10−4 M /yr and an average timescale 20.92 kyr. Our analysis reveals that multiple velocity components pervade the protocluster, indicating kinematic complexity in the dense gas. The large-scale position-velocity diagram shows that the filament hosting the protocluster is separated into 2 velocity structures, which appear to be rotating around each other, while they inflow towards denser N2H+ regions. Additionally, their mass buildup timescales that reach 20 kyr.
Description
Tesis presentada para optar al grado de Magíster en Astronomía.
Keywords
Protocluster, Milky Way, Kinematics, Star formation