Browsing by Author "Guzman, Viviana"

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    First Detection of Molecular Gas in the Giant Low Surface Brightness Galaxy Malin 1
    (2024) Galaz, Gaspar; Gonzalez-Lopez, Jorge; Guzman, Viviana; Messias, Hugo; Junais, Samuel; Boissier, Samuel; Epinat, Benoit; Weilbacher, Peter M.; Puzia, Thomas; Johnston, Evelyn J.; Amram, Philippe; Frayer, David; Blana, Matias; Howk, J. Christopher; Berg, Michelle; Bustos-Espinoza, Roy; Munoz-Mateos, Juan Carlos; Cortes, Paulo; Garcia-Appadoo, Diego; Joachimi, Katerine
    After over three decades of unsuccessful attempts, we report the first detection of molecular gas emission in Malin 1, the largest spiral galaxy observed to date, and one of the most iconic giant low surface brightness galaxies. Using Atacama Large Millimeter/submillimeter Array, we detect significant 12CO (J = 1-0) emission in the galaxy's central region and tentatively identify CO emission across three regions on the disk. These observations allow for a better estimate of the H2 mass and molecular gas mass surface density, both of which are remarkably low given the galaxy's scale. By integrating data on its H i mass, we derive a very low molecular-to-atomic gas mass ratio. Overall, our results highlight the minimal presence of molecular gas in Malin 1, contrasting sharply with its extensive, homogeneous atomic gas reservoir. For the first time, we position Malin 1 on the Kennicutt-Schmidt diagram, where it falls below the main sequence for normal spirals, consistent with previous upper limits but now with more accurate figures. These findings are crucial for constraining our understanding of star formation processes in environments characterized by extremely low molecular gas densities and for refining models of galaxy formation, thereby improving predictions concerning the formation, evolution, and distribution of these giant, elusive galaxies.
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    Gas kinematics around filamentary structures in the Orion B cloud
    (2023) Gaudel, Mathilde; Orkisz, Jan H.; Gerin, Maryvonne; Pety, Jerome; Roueff, Antoine; Marchal, Antoine; Levrier, Francois; Miville-Deschenes, Marc-Antoine; Goicoechea, Javier R.; Roueff, Evelyne; Le Petit, Franck; Magalhaes, Victor de Souza; Palud, Pierre; Santa-Maria, Miriam G.; Vono, Maxime; Bardeau, Sebastien; Bron, Emeric; Chainais, Pierre; Chanussot, Jocelyn; Gratier, Pierre; Guzman, Viviana; Hughes, Annie; Kainulainen, Jouni; Languignon, David; Le Bourlot, Jacques; Liszt, Harvey; Oberg, Karin; Peretto, Nicolas; Sievers, Albrecht; Tremblin, Pascal
    Context. Understanding the initial properties of star-forming material and how they affect the star formation process is key. From an observational point of view, the feedback from young high-mass stars on future star formation properties is still poorly constrained.Aims. In the framework of the IRAM 30m ORION-B large program, we obtained observations of the translucent (2 <= A(V) < 6 mag) and moderately dense gas (6 <= A(V) < 15 mag), which we used to analyze the kinematics over a field of 5 deg(2) around the filamentary structures.Methods. We used the Regularized Optimization for Hyper-Spectral Analysis (ROHSA) algorithm to decompose and de-noise the (CO)-O-18(1-0) and (CO)-C-13(1-0) signals by taking the spatial coherence of the emission into account. We produced gas column density and mean velocity maps to estimate the relative orientation of their spatial gradients.Results. We identified three cloud velocity layers at different systemic velocities and extracted the filaments in each velocity layer. The filaments are preferentially located in regions of low centroid velocity gradients. By comparing the relative orientation between the column density and velocity gradients of each layer from the ORION-B observations and synthetic observations from 3D kinematic toy models, we distinguish two types of behavior in the dynamics around filaments: (i) radial flows perpendicular to the filament axis that can be either inflows (increasing the filament mass) or outflows and (ii) longitudinal flows along the filament axis. The former case is seen in the Orion B data, while the latter is not identified. We have also identified asymmetrical flow patterns, usually associated with filaments located at the edge of an H II region.Conclusions. This is the first observational study to highlight feedback from H II regions on filament formation and, thus, on star formation in the Orion B cloud. This simple statistical method can be used for any molecular cloud to obtain coherent information on the kinematics.