Silverman_2018_ApJ_868_75.pdf (2.79 MB)
Concurrent starbursts in molecular gas disks within a pair of colliding galaxies at z = 1.52
journal contribution
posted on 2023-06-09, 16:04 authored by J D Silverman, E Daddi, W Rujopakarn, A Renzini, C Mancini, F Bournaud, A Puglisi, G Rodighiero, D Liu, Mark Sargent, N Armioto, M Béthermin, J Frensch, C C Hayward, J Kartaltepe, D Kashino, A Koekemoer, G Magdis, H J McCracken, T Nagao, K Sheth, V Smolcic, F ValentinoWe 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 (850um) at a spatial resolution of 0.3" reveal two compact (r_1/2 ~ 1 kpc) and interacting molecular gas disks at a separation of 8.6 kpc thus indicative of an early stage in a merger. With a SFR of 991 Msun/yr, this starburst event should occur closer to final coalescence, as 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 (alpha_CO = M_gas/L'_CO(1-0)), 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 (t_depl=85 and 67 Myrs) 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.
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- Published
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- Published version
Journal
Astrophysical JournalISSN
0004-637XPublisher
American Astronomical SocietyExternal DOI
Issue
75Volume
868Page range
1-17Department affiliated with
- Physics and Astronomy Publications
Research groups affiliated with
- Astronomy Centre Publications
Full text available
- Yes
Peer reviewed?
- Yes
Legacy Posted Date
2018-11-28First Open Access (FOA) Date
2018-11-28First Compliant Deposit (FCD) Date
2018-11-27Usage metrics
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