Browsing by Author "Galaz Lladser, Gaspar"

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    The CHIMERA Survey: The first CO detection in Leo T, the lowest mass known galaxy still hosting cold molecular gas
    (2025) Villanueva, Vicente; Blaña Díaz, Matías; Bolatto, Alberto D.; Rubio, Mónica; Tarantino, Elizabeth; Herrera Camus, Rodrigo Ignacio; Burkert, Andreas; Vaz, Daniel; Read, Justin I.; Galaz Lladser, Gaspar; Muñoz, César; Calderón Espinoza, Diego Nicolas; Behrendt, Manuel; Carballo Bello, Julio A.; Gray, Emily; Fellhauer, Michael
    We report the first CO detection in Leo T, representing the most extreme observation of carbon monoxide molecules in the lowest stellar mass gas-rich dwarf galaxy (M⋆ ∼ 105 M⊙) known to date. We acquired and present new Atacama Compact Array (ACA) 12CO(J = 1–0) data within our CHIMERA Survey project for the central region of Leo T, a metal-poor ([M/H] ∼ ‑1.7) dwarf in the Milky Way (MW) outskirts. We identified three compact molecular clouds (< 13 pc) with estimated upper limit virial masses of Mmol ∼ 5 × 103 M⊙ each and a total of 1.4 ± 0.4 × 104 M⊙, corresponding to ∼3% of the total gas mass. We obtained CO-to-H2 conversion factors (αCO) as high as ∼ 155 M⊙(K km s‑1 pc2)‑1 and mean molecular gas surface densities of Σmol ∼ 9 M⊙ pc‑2 that are consistent with values found in dwarf galaxies with extremely low metal content. All CO clouds are shifted (∼60 pc) from the stellar population centers, and only one cloud appears within the densest HI region. Two clouds have velocity offsets with the HI of Δvlos ∼ + 13 km s‑1 being within twice the velocity dispersion (Δvlos/σHI, los ∼ 2) and probably bound. However, the northern cloud is faster (Δvlos ∼ + 57 km s‑1); our models with low halo masses (Mh ≲ 109 M⊙) result in unbound orbits, suggesting that this material is likely being expelled from the dwarf, providing evidence for molecular gas depletion. These properties reveal a perturbed dynamics intertwined with star formation processes in low-mass dwarf galaxies, supporting a scenario of episodic bursts until they are fully quenched by the MW environment....
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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.