Browsing by Author "Howk, J. Christopher"

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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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    The Giant Low Surface Brightness Galaxy Malin 1: New Constraints for Its Molecular Gas Mass from GBT/ARGUS Observations
    (2022) Galaz Lladser, Gaspar; Frayer, David T.; Blaña, Matías; Howk, J. Christopher; Puzia, Thomas; Johnston, Evelyn J.; Ordenes Briceño, Yasna; Church, Sarah; Gil, Santiago; Joachimi, Katerine; Mora, Marcelo
    We report on results from GBT/ARGUS 12CO(1-0) observations for the giant low surface brightness galaxy Malin 1, which allow us to determine an upper limit for its CO mass, and hence its molecular gas mass and molecular gas mass surface density ? H 2 . Although we performed very deep observations through 17 hr on-source integration time, reaching a noise level of ?0.2 mK (T A * ) with a corresponding extended source CO limit (3?) of 0.09 K km s?1, 19 times more sensitive than previous works, we do not detect the 12CO(1-0) emission line. However, the observations allow us to estimate an upper limit (3?) for the CO mass of about 7.4 × 109 M ? for the extended emission, and 1.4 × 108 M ? for the central part of the galaxy. With these figures we conclude that the molecular gas surface density is lower than 0.3 M ? pc?2, and the corresponding molecular to atomic gas mass ratio is lower than 0.13. The evidence suggests quite different physical conditions for the interstellar medium in Malin 1 compared to that of normal, high surface brightness spirals. This, in one way to another, keeps an usual molecular gas tracer as CO hidden from our observations, in spite of the diverse stellar and structural properties of Malin 1 observed by several authors since more than 30 yr.