Abstract
Galaxies in the early Universe that are bright at submillimetre wavelengths (submillimetre-bright galaxies) are forming stars at a rate roughly 1,000 times higher than the Milky Way. A large fraction of the new stars form in the central kiloparsec of the galaxy1,2,3, a region that is comparable in size to the massive, quiescent galaxies found at the peak of cosmic star-formation history4 and the cores of present-day giant elliptical galaxies. The physical and kinematic properties inside these compact starburst cores are poorly understood because probing them at relevant spatial scales requires extremely high angular resolution. Here we report observations with a linear resolution of 550 parsecs of gas and dust in an unlensed, submillimetre-bright galaxy at a redshift of zā=ā4.3, when the Universe was less than two billion years old. We resolve the spatial and kinematic structure of the molecular gas inside the heavily dust-obscured core and show that the underlying gas disk is clumpy and rotationally supported (that is, its rotation velocity is larger than the velocity dispersion). Our analysis of the molecular gas mass per unit area suggests that the starburst disk is gravitationally unstable, which implies that the self-gravity of the gas is stronger than the differential rotation of the disk and the internal pressure due to stellar-radiation feedback. As a result of the gravitational instability in the disk, the molecular gas would be consumed by star formation on a timescale of 100 million years, which is comparable to gas depletion times in merging starburst galaxies5.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 /Ā 30Ā days
cancel any time
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Swinbank, A. M. et al. Intense star formation within resolved compact regions in a galaxy at z = 2.3. Nature 464, 733ā736 (2010).
Ikarashi, S. et al. Compact starbursts in z ~ 3ā6 submillimeter galaxies revealed by ALMA. Astrophys. J. 810, 133 (2015).
Simpson, J. M. et al. The SCUBA-2 cosmology legacy survey: ALMA resolves the rest-frame far-infrared emission of sub-millimeter galaxies. Astrophys. J. 799, 81 (2015).
van Dokkum, P. et al. Forming compact massive galaxies. Astrophys. J. 813, 23 (2015).
Kennicutt, R. C. Jr. The global Schmidt law in star-forming galaxies. Astrophys. J. 498, 541ā552 (1998).
Hughes, D. H. et al. High-redshift star formation in the Hubble Deep Field revealed by a submillimetre-wavelength survey. Nature 394, 241ā247 (1998).
Barger, A. J. et al. Submillimetre-wavelength detection of dusty star-forming galaxies at high redshift. Nature 394, 248ā251 (1998).
Chapman, S. C. et al. A redshift survey of the submillimeter galaxy population. Astrophys. J. 622, 772ā796 (2005).
Bothwell, M. S. et al. A survey of molecular gas in luminous sub-millimetre galaxies. Mon. Not. R. Astron. Soc. 429, 3047ā3067 (2013).
Ivison, R. J. et al. Herschel-ATLAS: a binary HyLIRG pinpointing a cluster of starbursting protoellipticals. Astrophys. J. 772, 137 (2013).
Tacconi, L. J. et al. Submillimeter galaxies at z ~ 2: evidence for major mergers and constraints on lifetimes, IMF, and CO-H2 conversion factor. Astrophys. J. 680, 246ā262 (2008).
Hodge, J. A. et al. Evidence for a clumpy, rotating gas disk in a submillimeter galaxy at z = 4. Astrophys. J. 760, 11 (2012).
Iono, D. et al. Clumpy and extended starbursts in the brightest unlensed submillimeter galaxies. Astrophys. J. 829, L10 (2016).
Tadaki, K.-i. et al. Bulge-forming galaxies with an extended rotating disk at z ~ 2. Astrophys. J. 834, 135 (2017).
Swinbank, A. M. et al. ALMA resolves the properties of star-forming regions in a dense gas disk at z ~ 3. Astrophys. J. 806, L17 (2015).
Sharda, P. et al. Testing star formation laws in a starburst galaxy at redshift 3 resolved with ALMA. Mon. Not. R. Astron. Soc. 477, 4380ā4390 (2018).
Bolatto, A. D. et al. The resolved properties of extragalactic giant molecular clouds. Astrophys. J. 686, 948ā965 (2008).
Cappellari, M. Structure and kinematics of early-type galaxies from integral field spectroscopy. Annu. Rev. Astron. Astrophys. 54, 597ā665 (2016).
Veale, M. et al. The MASSIVE survey ā V. Spatially resolved stellar angular momentum, velocity dispersion, and higher moments of the 41 most massive local early-type galaxies. Mon. Not. R. Astron. Soc. 464, 356ā384 (2017).
Naab, T. et al. The ATLAS3D project ā XXV. Two-dimensional kinematic analysis of simulated galaxies and the cosmological origin of fast and slow rotators. Mon. Not. R. Astron. Soc. 444, 3357ā3387 (2014).
Genzel, R. et al. The Sins survey of z ~ 2 galaxy kinematics: properties of the giant star-forming clumps. Astrophys. J. 733, 101 (2011).
Bournaud, F. et al. The long lives of giant clumps and the birth of outflows in gas-rich galaxies at high-redshift. Astrophys. J. 780, 57ā75 (2014).
Mandelker, N. et al. The population of giant clumps in simulated high-z galaxies: in situ and ex situ migration and survival. Mon. Not. R. Astron. Soc. 443, 3675ā3702 (2014).
Genzel, R. et al. The SINS/zC-SINF survey of z ~ 2 galaxy kinematics: evidence for gravitational quenching. Astrophys. J. 785, 75 (2014).
Thompson, T. et al. Radiation pressure-supported starburst disks and active galactic nucleus fueling. Astrophys. J. 630, 167ā185 (2005).
Cacciato, M. et al. Evolution of violent gravitational disc instability in galaxies: late stabilization by transition from gas to stellar dominance. Mon. Not. R. Astron. Soc. 421, 818ā831 (2012).
Tacconi, L. J. et al. Phibss: molecular gas content and scaling relations in z ~ 1ā3 massive, main-sequence star-forming galaxies. Astrophys. J. 768, 74 (2013).
Narayanan, D. et al. The star-forming molecular gas in high-redshift submillimetre galaxies. Mon. Not. R. Astron. Soc. 400, 1919ā1935 (2009).
Ueda, J. et al. Cold molecular gas in merger remnants. I. Formation of molecular gas disks. Astrophys. J. Suppl. Ser. 214, 1 (2014).
Dekel, A. et al. Cold streams in early massive hot haloes as the main mode of galaxy formation. Nature 457, 451ā454 (2009).
Scott, K. B. et al. AzTEC millimetre survey of the COSMOS field ā I. Data reduction and source catalogue. Mon. Not. R. Astron. Soc. 385, 2225ā2238 (2008).
Yun, M. S. et al. Early science with the Large Millimeter Telescope: CO and [CĀ ii] emission in the zĀ =Ā 4.3 AzTEC J095942.9+022938 (COSMOS AzTEC-1). Mon. Not. R. Astron. Soc. 454, 3485ā3499 (2015).
Toft, S. et al. Submillimeter galaxies as progenitors of compact quiescent galaxies. Astrophys. J. 782, 68 (2014).
Chabrier, G. The galactic disk mass function: reconciliation of the Hubble Space Telescope and nearby determinations. Astrophys. J. 586, L133āL136 (2003).
McMullin, J. P., Waters, B., Schiebel, D., Young, W. & Golap, K. CASA architecture and applications. ASP Conf. Ser. 376, 127ā130 (2007).
SmolÄiÄ, V. et al. The redshift and nature of AzTEC/COSMOS 1: a starburst galaxy at z = 4.6. Astrophys. J. 731, L27 (2011).
Laigle, C. et al. The COSMOS2015 catalog: exploring the 1Ā <Ā zĀ <Ā 6 universe with half a million galaxies. Astrophys. J. Suppl. Ser. 24, 224 (2016).
Roseboom, I. G. et al. The Herschel multi-tiered extragalactic survey: SPIRE-mm photometric redshifts. Mon. Not. R. Astron. Soc. 419, 2758ā2773 (2012).
Oliver, S. J. et al. The Herschel multi-tiered extragalactic survey: HerMES. Mon. Not. R. Astron. Soc. 424, 1614ā1635 (2012).
SmolÄiÄ, V. et al. The VLA-COSMOS 3 GHz large project: continuum data and source catalog release. Astron. Astrophys. 602, A1 (2017).
da Cunha, E., Charlot, S. & Elbaz, D. A simple model to interpret the ultraviolet, optical and infrared emission from galaxies. Mon. Not. R. Astron. Soc. 388, 1595ā1617 (2008).
da Cunha, E. et al. An ALMA survey of sub-millimeter galaxies in the extended Chandra deep field south: physical properties derived from ultraviolet-to-radio modeling. Astrophys. J. 806, 110 (2015).
Bruzual, G. & Charlot, S. Stellar population synthesis at the resolution of 2003. Mon. Not. R. Astron. Soc. 344, 1000ā1028 (2003).
Papadopoulos, P. P., Thi, W.-F. & Viti, S. CĀ i lines as tracers of molecular gas, and their prospects at high redshifts. Mon. Not. R. Astron. Soc. 351, 147ā160 (2004).
WeiĆ, A. et al. Gas and dust in the Cloverleaf quasar at redshift 2.5. Astron. Astrophys. 409, L41āL45 (2003).
WeiĆ, A. et al. Atomic carbon at redshift ~2.5. Astron. Astrophys. 429, L25āL28 (2005).
Danielson, A. L. R. et al. The properties of the interstellar medium within a star-forming galaxy at z = 2.3. Mon. Not. R. Astron. Soc. 410, 1687ā1702 (2011).
Bothwell, M. S. et al. ALMA observations of atomic carbon in z ~ 4 dusty star-forming galaxies. Mon. Not. R. Astron. Soc. 466, 2825ā2841 (2017).
White, G. J. et al. CO and CĀ i maps of the starburst galaxy M 82. Astron. Astrophys. 284, L23āL26 (1994).
Wilson, C. et al. Luminous infrared galaxies with the submillimeter array. I. Survey overview and the central gas to dust ratio. Astrophys. J. Suppl. Ser. 178, 189ā224 (2008).
Bolatto, A. D., Wolfire, M. & Leroy, A. K. The CO-to-H2 conversion factor. Annu. Rev. Astron. Astrophys. 51, 207ā268 (2013).
Downes, D. & Solomon, P. M. Rotating nuclear rings and extreme starbursts in ultraluminous galaxies. Astrophys. J. 507, 615ā654 (1998).
Carilli, C. L. & Walter, F. Cool gas in high-redshift galaxies. Annu. Rev. Astron. Astrophys. 51, 105ā161 (2013).
Bournaud, F. et al. Modeling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies. Astron. Astrophys. 575, A56 (2015).
Bouche, N. et al. GalPak3D: a Bayesian parametric tool for extracting morphokinematics of galaxies from 3D data. Astrophys. J. 150, 92 (2015).
Toomre, A. On the gravitational stability of a disk of stars. Astrophys. J. 139, 1217ā1238 (1964).
Wang, B. et al. Gravitational instability and disk star formation. Astrophys. J. 427, 759ā769 (1994).
Binney, J. & Tremaine, S. Galactic Dynamics 2nd edn, 494ā496 (Princeton Univ. Press, Princeton, 2008).
Romeo, A. B. & Wiegert, J. The effective stability parameter for two-component galactic discs: is \({Q}^{-1}\approx {Q}_{{\rm{stars}}}^{-1}+{Q}_{{\rm{gas}}}^{-1}\)? Mon. Not. R. Astron. Soc. 416, 1191ā1196 (2011).
Acknowledgements
We thank J. Baba for discussions about a gravitational instability in SMGs. This work was supported by JSPS KAKENHI JP17J04449. We thank the ALMA staff and in particular the EA-ARC staff for their support. This research has made use of data from ALMA and HerMES project (http://hermes.sussex.ac.uk/). ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. HerMES is a Herschel Key Programme utilizing Guaranteed Time from the SPIRE instrument team, ESAC scientists and a mission scientist. Data analysis was in part carried out on the common-use data analysis computer system at the Astronomy Data Center (ADC) of the National Astronomical Observatory of Japan.
Reviewer information
Nature thanks F. Bournaud and the other anonymous reviewer(s) for their contribution to the peer review of this work.
Author information
Authors and Affiliations
Contributions
K.T. led the project and reduced the ALMA data. K.T. and D.I. wrote the manuscript. M.S.Y. reduced the Large Millimeter Telescope data and edited the final manuscript. Other authors contributed to the interpretation and commented on the ALMA proposal and the paper.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisherās note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data figures and tables
Extended Data Fig. 1 Galaxy-integrated CO (4ā3), CO (1ā0) and C i (2ā1) spectra of AzTEC-1.
The CO (4ā3) spectrum is extracted using an 0.8ā³-diameter aperture in the natural-weighted map cube. The CĀ i (1ā0) and CĀ i (2ā1) spectra are extracted from the peak positions in map cubes with 1.7ā³āĆā1.1ā³ and 0.8ā³āĆā0.7ā³ resolution, respectively. Yellow shaded regions show the velocity range vā=āā315Ā kmĀ sā1 to vā=ā+315Ā kmĀ sā1, in which the velocity-integrated line fluxes are measured.
Extended Data Fig. 3 CO spectra along the kinematic major axis.
Spectra are extracted at a position angle of PAā=āā64Ā°. The spatial offset x from the galactic centre is shown at the upper left of each panel. Red lines indicate the spectra of the best-fitting dynamical model produced by GalPaK3D.
Extended Data Fig. 4 Full MCMC chain for 20,000 iterations.
Red solid lines and black dashed lines indicate the median and 95% confidence interval of the last 60% of the MCMC chain.
Rights and permissions
About this article
Cite this article
Tadaki, K., Iono, D., Yun, M.S. et al. The gravitationally unstable gas disk of a starburst galaxy 12 billion years ago. Nature 560, 613ā616 (2018). https://doi.org/10.1038/s41586-018-0443-1
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41586-018-0443-1
This article is cited by
-
Molecular clouds in the Cosmic Snake normal star-forming galaxy 8 billion years ago
Nature Astronomy (2019)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.
