A pilot survey of star-forming galaxies at z=6 with NOEMA.
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Date
2025
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Universidad de Concepción
Abstract
Presentamos observaciones del Northern Extended Millimeter Array (NOEMA) de cuatro galaxias luminosas en z ∼ 6, cuando el Universo tenía menos de ∼ 1 Gyr de antigüedad. Estas galaxias se detectan en la línea de estructura fina [CII] de 158 µm, y tres de ellas también muestran emisión continua de polvo subyacente. Las velocidades de la línea [CII] están desplazadas unos cientos de km s−1 con respecto a la emisión Lyα, lo que podría indicar la presencia de flujos de salida o una gran reserva de gas atómico circundante. A partir de la combinación del continuo de polvo y la emisión UV en el marco de referencia, estimamos que aproximadamente el 50 % de la formación estelar está oscurecida por el polvo, lo que concuerda con los valores encontrados en otras galaxias con formación estelar masiva en desplazamientos al rojo similares. Las relaciones de luminosidad [CII]-FIR de las galaxias detectadas por continuo son elevadas en comparación con las galaxias cercanas con luminosidades FIR similares. En un sistema, J163026+4315, la emisión de [CII] se resuelve espacialmente, lo que nos permite medir el tamaño de la fuente y el brillo superficial FIR (ΣFIR). Encontramos que la relación [CII]/FIR como función de ΣFIR en esta fuente sigue las tendencias observadas tanto en poblaciones de galaxias locales como de alto desplazamiento al rojo. Un análisis cinemático de la emisión [CII] resuelta proporciona pruebas provisionales de la existencia de un disco giratorio, aunque se necesitan datos con mayor resolución angular para confirmarlo. Estos resultados demuestran la capacidad de NOEMA para sondear las condiciones físicas y la estructura del medio interestelar en las galaxias durante los primeros mil millones de años de la historia cósmica.
We present observations from the Northern Extended Millimeter Array (NOEMA) of four luminous galaxies at z ∼ 6, when the Universe was less than ∼ 1 Gyr old. These galaxies are detected in the [CII] 158µm fine-structure line, and three also exhibit underlying dust continuum emission. The [CII] line velocities are offset by a few hundred kms−1 relative to the Lyα emission, possibly indicating the presence of outflows or a large reservoir of surrounding atomic gas. From the combination of dust continuum and rest-frame UV emission, we estimate that approximately 50% of the star formation is obscured by dust, consistent with values found in other massive star-forming galaxies at similar redshifts. The [CII] to-FIR luminosity ratios of the continuum-detected galaxies are elevated compared to nearby galaxies with similar FIR luminosities. In one system, J163026+4315, the [CII] emission is spatially resolved, allowing us to measure the source size and FIR surface brightness (ΣFIR). We find that the [CII]/FIR ratio as a function of ΣFIR in this source follows the trends observed in both local and high-redshift galaxy populations. A kinematic analysis of the resolved [CII] emission provides tentative evidence for a rotating disk, although higher angular resolution data are needed to confirm this. These results demonstrate the power of NOEMA to probe the physical conditions and structure of the interstellar medium in galaxies in the f irst billion years of cosmic history.
We present observations from the Northern Extended Millimeter Array (NOEMA) of four luminous galaxies at z ∼ 6, when the Universe was less than ∼ 1 Gyr old. These galaxies are detected in the [CII] 158µm fine-structure line, and three also exhibit underlying dust continuum emission. The [CII] line velocities are offset by a few hundred kms−1 relative to the Lyα emission, possibly indicating the presence of outflows or a large reservoir of surrounding atomic gas. From the combination of dust continuum and rest-frame UV emission, we estimate that approximately 50% of the star formation is obscured by dust, consistent with values found in other massive star-forming galaxies at similar redshifts. The [CII] to-FIR luminosity ratios of the continuum-detected galaxies are elevated compared to nearby galaxies with similar FIR luminosities. In one system, J163026+4315, the [CII] emission is spatially resolved, allowing us to measure the source size and FIR surface brightness (ΣFIR). We find that the [CII]/FIR ratio as a function of ΣFIR in this source follows the trends observed in both local and high-redshift galaxy populations. A kinematic analysis of the resolved [CII] emission provides tentative evidence for a rotating disk, although higher angular resolution data are needed to confirm this. These results demonstrate the power of NOEMA to probe the physical conditions and structure of the interstellar medium in galaxies in the f irst billion years of cosmic history.
Description
Tesis presentada para optar al grado de Magíster en Astronomía.
Keywords
Galaxies Evolution, Interstellar matter, Red shift