Deep kiloparsec view of the molecular gas in a massive star-forming galaxy at cosmic noon.
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Date
2024
Journal Title
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Publisher
Universidad de Concepción
Abstract
Presentamos observaciones profundas (∼20 hr) y de alta resolución angular del Atacama Large Millimeter/submillimeter Array (ALMA) de las transiciones CO (4 − 3) y [CI] (1 − 0), junto con el continuo de polvo a 630 μm en BX610 –una galaxia masiva de secuencia principal en la época de máxima formación estelar cósmica (z = 2.21). Combinadas con observaciones profundas SINFONI del Very Large Telescope (VLT) de la línea Hα, estas observaciones permiten una caracterización detallada del gas molecular y de la actividad de formación estelar en escalas de kiloparsecs. Nuestro análisis revela que la excitación del gas molecular, trazada por la razón de luminosidad de línea L′CO (4−3) / L′[CI] (1−0), disminuye al aumentar el radio galactocéntrico. Mientras que las razones de luminosidad de línea en la periferia son similares a las que suelen encontrarse en galaxias de secuencia principal a z ∼ 1, las razones en las regiones centrales de BX610 son comparables a las observadas en starbursts locales. En el suroeste de BX610 también hay un clump gigante de formación estelar extra-nuclear que muestra una elevada actividad de formación estelar, abundancia de gas molecular y excitación de gas molecular. Además, la región central de BX610 es rica en gas molecular (Mmol/M⋆ ≈ 1), pero con el alto nivel actual de actividad de formación estelar, el gas molecular se agotará en ∼450 Myr. Esto, junto con la evidencia de un rápido inflow de gas molecular hacia el centro (Genzel et al., 2023), sugiere que BX610 puede estar experimentando una fase evolutiva a menudo denominada compactación húmeda, que se espera que conduzca al agotamiento del gas central y a la subsiguiente extinción de la actividad de formación estelar.
We present deep (∼20 hr), high-angular resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO (4 − 3) and [CI] (1 − 0) transitions, along with the rest-frame 630 μm dust continuum, in BX610—a massive, main-sequence galaxy at the peak epoch of cosmic star formation (z = 2.21). Combined with deep Very Large Telescope (VLT) SINFONI observations of the Hα line, these observations enable a detailed characterization of the molecular gas and star formation activity on kiloparsec scales. Our analysis reveals that the excitation of the molecular gas, as traced by the L′CO (4−3) / L′[CI] (1−0) line luminosity ratio, decreases with increasing galactocentric radius. While the line luminosity ratios in the outskirts are similar to those typically found in main-sequence galaxies at z ∼ 1, the ratios in the central regions of BX610 are comparable to those observed in local starbursts. There is also a giant extra-nuclear star-forming clump in the southwest of BX610 that exhibits high star formation activity, molecular gas abundance, and molecular gas excitation. Furthermore, the central region of BX610 is rich in molecular gas (Mmol/M⋆ ≈ 1), but at the current high level of star formation activity, the molecular gas will be exhausted in ∼450 Myr. This, along with evidence for rapid molecular gas inflow toward the center (Genzel et al., 2023), suggests that BX610 may be experiencing an evolutionary phase often referred to as wet compaction, which is expected to lead to central gas depletion and subsequent inside-out quenching of star formation activity.
We present deep (∼20 hr), high-angular resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO (4 − 3) and [CI] (1 − 0) transitions, along with the rest-frame 630 μm dust continuum, in BX610—a massive, main-sequence galaxy at the peak epoch of cosmic star formation (z = 2.21). Combined with deep Very Large Telescope (VLT) SINFONI observations of the Hα line, these observations enable a detailed characterization of the molecular gas and star formation activity on kiloparsec scales. Our analysis reveals that the excitation of the molecular gas, as traced by the L′CO (4−3) / L′[CI] (1−0) line luminosity ratio, decreases with increasing galactocentric radius. While the line luminosity ratios in the outskirts are similar to those typically found in main-sequence galaxies at z ∼ 1, the ratios in the central regions of BX610 are comparable to those observed in local starbursts. There is also a giant extra-nuclear star-forming clump in the southwest of BX610 that exhibits high star formation activity, molecular gas abundance, and molecular gas excitation. Furthermore, the central region of BX610 is rich in molecular gas (Mmol/M⋆ ≈ 1), but at the current high level of star formation activity, the molecular gas will be exhausted in ∼450 Myr. This, along with evidence for rapid molecular gas inflow toward the center (Genzel et al., 2023), suggests that BX610 may be experiencing an evolutionary phase often referred to as wet compaction, which is expected to lead to central gas depletion and subsequent inside-out quenching of star formation activity.
Description
Tesis presentada para optar al grado de Magíster en Astronomía
Keywords
Galaxias, Estrellas Formación