Concurrent Starbursts in Molecular Gas Disks within a Pair of Colliding Galaxies at z = 1.52

We report on the discovery of a merger-driven starburst at z = 1.52, PACS-787, based on high signal-to-noise ALMA observations. CO(5-4) and continuum emission (850 m) at a spatial resolution of 0 3 reveal two compact (r1/2 ∼ 1 kpc) and interacting molecular gas disks at a separation of 8.6 kpc, indi...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2018-11, Vol.868 (1), p.75
Main Authors: Silverman, J. D., Daddi, E., Rujopakarn, W., Renzini, A., Mancini, C., Bournaud, F., Puglisi, A., Rodighiero, G., Liu, D., Sargent, M., Arimoto, N., Béthermin, M., Fensch, J., Hayward, C. C., Kartaltepe, J., Kashino, D., Koekemoer, A., Magdis, G., McCracken, H. J., Nagao, T., Sheth, K., Smol i, V., Valentino, F.
Format: Article
Language:English
Subjects:
Accretion disks
Angular momentum
Astrophysics
Calibration
Coalescence
Coalescing
Continuum radiation
Cosmology and Extra-Galactic Astrophysics
Depletion
Emission
Galactic Astrophysics
Galactic evolution
Galaxies
galaxies: high-redshift
galaxies: ISM
galaxies: star formation
galaxies: starburst
Galaxy mergers & collisions
Inclination
Luminosity
Molecular gases
Red shift
Rotating disks
Sciences of the Universe
Spatial resolution
Star & galaxy formation
Star formation
Stars & galaxies
Velocity distribution
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Summary:We report on the discovery of a merger-driven starburst at z = 1.52, PACS-787, based on high signal-to-noise ALMA observations. CO(5-4) and continuum emission (850 m) at a spatial resolution of 0 3 reveal two compact (r1/2 ∼ 1 kpc) and interacting molecular gas disks at a separation of 8.6 kpc, indicative of an early stage in a merger. With an SFR of 991 M yr−1, this starburst event should occur closer to final coalescence, as is usually seen in hydrodynamical simulations. From the CO size, inclination, and velocity profile for both disks, the dynamical mass is calculated through a novel method that incorporates a calibration using simulations of galaxy mergers. Based on the dynamical mass, we measure (1) the molecular gas mass, independent from the CO luminosity, (2) the ratio of the total gas mass and the CO(1-0) luminosity ( ), and (3) the gas-to-dust ratio, with the latter two being lower than typically assumed. We find that the high star formation triggered in both galaxies is caused by a set of optimal conditions: a high gas mass/fraction, a short depletion time (τdepl = 85 and 67 Myr) to convert gas into stars, and the interaction of likely counter-rotating molecular disks that may accelerate the loss of angular momentum. The state of interaction is further established by the detection of diffuse CO and continuum emission, tidal debris that bridges the two nuclei and is associated with stellar emission seen by HST/WFC3. This observation demonstrates the power of ALMA to study the dynamics of galaxy mergers at high redshift.
ISSN:0004-637X
2041-8205
1538-4357
2041-8213
DOI:10.3847/1538-4357/aae64b