The ALMA [C II] Resolved Ism in STar-forming gALaxies (CRISTAL) survey is a Cycle 8 ALMA Large Program that studies the cold- gas component of high-redshift galaxies. Its subarcsecond-resolution observations are key to distinguishing physical mechanisms that shaped galaxies during cosmic dawn. In this paper, we explore the morphology and kinematics of the cold gas, star-forming, and stellar components in the star-forming main-sequence galaxy CRISTAL-05/HZ3, at z = 5.54. Our analysis includes ALMA observations at a spatial resolution of 0.3″ (∼2 kpc) of the [C II] line. While CRISTAL-05 was previously classified as a single source, our observations reveal that the system is a close interacting pair that is surrounded by an extended component of carbon-enriched gas. This is imprinted in the disturbed elongated [C II] morphology and in the separation of the two components in the position-velocity diagram (∼100 km s−1 ). The central region is composed of two components, named C05-NW and C05-SE, and the former is the dominant component. A significant fraction of [C II] arises beyond the close pair up to 10 kpc, while the regions forming new massive stars and the stellar component seem compact (r[C II] ∼4 × rUV ), as traced by rest-frame UV and optical imaging obtained with the Hubble Space Telescope and the James Webb Space Telescope. Our kinematic model, constructed using the DYSMALpy software, yields a minor contribution of dark matter of C05-NW within a radius of ∼2 × Reff. Finally, we explore the resolved [C II] /far-IR ratios as a proxy for shock-heating produced by this merger. We argue that the extended [C II] emission is mainly caused by the merger of the galaxies, which could not be discerned with lower-resolution observations. Our work emphasizes the need for high-resolution observations to fully characterize the dynamic stages of infant galaxies and the physical mechanisms that drive the metal enrichment of the circumgalactic medium.
The ALMA-CRISTAL survey: Extended CII emission in an interacting galaxy system at z ∼ 5.5 / Posses, A.; Aravena, M.; Gonzalez-Lopez, J.; Forster Schreiber, N. M.; Liu, D.; Lee, L.; Solimano, M.; Diaz-Santos, T.; Assef, R. J.; Barcos-Munoz, L.; Bovino, S.; Bowler, R. A.; Calistro Rivera, G.; Da Cunha, E.; Davies, R. L.; Killi, M.; De Looze, I.; Ferrara, A.; Fisher, D. B.; Herrera-Camus, R.; Ikeda, R.; Lambert, T.; Li, J.; Lutz, D.; Mitsuhashi, I.; Palla, M.; Relano, M.; Spilker, J.; Naab, T.; Tadaki, K.; Telikova, K.; Ubler, H.; Van Der Giessen, S.; Villanueva, V.. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 699:(2025), pp. 1-25. [10.1051/0004-6361/202449843]
The ALMA-CRISTAL survey: Extended CII emission in an interacting galaxy system at z ∼ 5.5
Bovino, S.;Palla, M.;
2025
Abstract
The ALMA [C II] Resolved Ism in STar-forming gALaxies (CRISTAL) survey is a Cycle 8 ALMA Large Program that studies the cold- gas component of high-redshift galaxies. Its subarcsecond-resolution observations are key to distinguishing physical mechanisms that shaped galaxies during cosmic dawn. In this paper, we explore the morphology and kinematics of the cold gas, star-forming, and stellar components in the star-forming main-sequence galaxy CRISTAL-05/HZ3, at z = 5.54. Our analysis includes ALMA observations at a spatial resolution of 0.3″ (∼2 kpc) of the [C II] line. While CRISTAL-05 was previously classified as a single source, our observations reveal that the system is a close interacting pair that is surrounded by an extended component of carbon-enriched gas. This is imprinted in the disturbed elongated [C II] morphology and in the separation of the two components in the position-velocity diagram (∼100 km s−1 ). The central region is composed of two components, named C05-NW and C05-SE, and the former is the dominant component. A significant fraction of [C II] arises beyond the close pair up to 10 kpc, while the regions forming new massive stars and the stellar component seem compact (r[C II] ∼4 × rUV ), as traced by rest-frame UV and optical imaging obtained with the Hubble Space Telescope and the James Webb Space Telescope. Our kinematic model, constructed using the DYSMALpy software, yields a minor contribution of dark matter of C05-NW within a radius of ∼2 × Reff. Finally, we explore the resolved [C II] /far-IR ratios as a proxy for shock-heating produced by this merger. We argue that the extended [C II] emission is mainly caused by the merger of the galaxies, which could not be discerned with lower-resolution observations. Our work emphasizes the need for high-resolution observations to fully characterize the dynamic stages of infant galaxies and the physical mechanisms that drive the metal enrichment of the circumgalactic medium.| File | Dimensione | Formato | |
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