Publication: Molecular clouds in the Cosmic Snake normal star-forming galaxy 8 billion years ago
Loading...
Official URL
Full text at PDC
Publication Date
2019-12
Advisors (or tutors)
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
Nature Publishing Group
Abstract
The cold molecular gas in contemporary galaxies is structured in discrete cloud complexes. These giant molecular clouds (GMCs), with 10^(4) –10^(7) solar masses (M⊙) and radii of 5–100 parsecs, are the seeds of star formation1 . Highlighting the molecular gas structure at such small scales in distant galaxies is observationally challenging. Only a handful of molecular clouds were reported in two extreme submillimetre galaxies at high redshift(2-4) . Here we search for GMCs in a typical Milky Way progenitor at z=1.036. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we mapped the CO(4–3) emission of this gravitationally lensed galaxy at high resolution, reading down to 30 parsecs, which is comparable to the resolution of CO observations of nearby galaxies(5). We identify 17 molecular clouds, characterized by masses, surface densities and supersonic turbulence all of which are 10–100 times higher than present-day analogues. These properties question the universality of GMCs(6) and suggest that GMCs inherit their properties from ambient interstellar medium. The measured cloud gas masses are similar to the masses of stellar clumps seen in the galaxy in comparable numbers(7) . This corroborates the formation of molecular clouds by fragmentation of distant turbulent galactic gas disks(8,9), which then turn into stellar clumps ubiquitously observed in galaxies at ‘cosmic noon’ (ref. 10).
Description
© The Autors, 2019. Artículo firmado por 15 autores. The work of M.D.-Z., D.S., L.M. and A.C. was supported by the STARFORM Sinergia Project funded by the Swiss National Science Foundation. J.R. acknowledges support from the European Research Council starting grant 336736-CALENDS. W.R. is supported by the Thailand Research Fund/Office of the Higher Education Commission Grant Number MRG6280259 and Chulalongkorn University’s CUniverse. P.G.P.-G. acknowledges support from the Spanish Government grant AYA2015-63650-P. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2013.1.01330.S. 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 (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. We also used PdBI observations. PdBI is run by the Institut de Radioastronomie Millimétrique (IRAM, France), a partnership of the French CNRS, the German MPG and the Spanish IGN. Part of the analysis presented herein is also based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA). We thank E. Chapillon from the ALMA Regional Center node of IRAM for her help and training on the reduction of the ALMA data, V. Patricio for sharing the kinematic analysis of the [OII] emission of the Cosmic Snake galaxy and C. Georgy for the presentation of the VisIt 3D visualization tool.
UCM subjects
Unesco subjects
Keywords
Citation
1. Bolatto, A. D., Leroy, A. K., Rosolowsky, E., Walter,
F. & Blitz, L. The resolved properties of extragalactic
giant molecular clouds. Astrophys. J. 686, 948–965
(2008).
2. 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–L22 (2015).
3. Sharda, P., Federrath, C., da Cunha, E., Swinbank,
A. M. & Dye, S. Testing star formation laws in a
starburst galaxy at redshift 3 resolved with ALMA.
Mon. Not. R. Astron. Soc. 477, 4380–4390 (2018).
4. Tadaki, K. et al. The gravitationally unstable gas disk
of a starburst galaxy 12 billion years ago. Nature 560,
613–616 (2018).
5. Sun, J. et al. Cloud-scale molecular gas properties in
15 nearby galaxies. Astrophys. J. 860, 172–211 (2018).
6. Hughes, A. et al. A comparative study of giant
molecular clouds in M51, M33, and the Large
Magellanic Cloud. Astrophys. J. 779, 46–66 (2013).
7. Cava, A. et al. The nature of giant clumps in distant
galaxies probed by the anatomy of the Cosmic Snake.
Nat. Astron. 2, 76–82 (2018)
given molecular cloud by the hydrostatic pressure at the
disk midplane for a two-component disk of gas and stars45:
ÉYçn
Ñ = é
2 G Σ89: ;Σ89: +
%89:
%:n9Q:
Σ:n9Q:G cmlOK
where Σ89:, Σ:n9Q:, and %89:, %:n9Q: are the surface
densities and velocity dispersions of the gas and stars,
respectively. We considered the molecular gas phase as the
dominant phase of the neutral (atomic + molecular) gas in
this z≃1 galaxy. We derived surface densities from the
molecular gas and stellar masses contained within the
observed gas disk of 1.7kpc in galactocentric radius, and
assumed the velocity dispersions of gas and stars to be
comparable. We obtained the hydrostatic pressure of
~107.7 cm−3K in the Cosmic Snake galaxy.
Data availability
The ALMA raw data of the Cosmic Snake arc are available
through the ALMA archive under the project identification
2013.1.01330.S. The HST images of MACS J1206.2–0847
are part of the CLASH, available at
https://archive.stsci.edu/prepds/clash/. The data that
support the plots within this paper and other findings of
this study are available from the corresponding author
upon reasonable request.
Code availability
The reduction of the ALMA data was performed with the
CASA pipeline version 4.2.2, available at
https://almascience.eso.org/processing/science-pipeline.
The PdBI data were reduced using GILDAS software,
available at http://www.iram.fr/IRAMFR/GILDAS. The
lens model was obtained using Lenstool, publicly available
at https://projets.lam.fr/projects/lenstool/wiki. The spectral
energy distribution fitting was performed with a modified
version of the Hyperz code, available in its original form at
https://ascl.net/1108.010.
References
1. Bolatto, A. D., Leroy, A. K., Rosolowsky, E., Walter,
F. & Blitz, L. The resolved properties of extragalactic
giant molecular clouds. Astrophys. J. 686, 948–965
(2008).
2. 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–L22 (2015).
3. Sharda, P., Federrath, C., da Cunha, E., Swinbank,
A. M. & Dye, S. Testing star formation laws in a
starburst galaxy at redshift 3 resolved with ALMA.
Mon. Not. R. Astron. Soc. 477, 4380–4390 (2018).
4. Tadaki, K. et al. The gravitationally unstable gas disk
of a starburst galaxy 12 billion years ago. Nature 560,
613–616 (2018).
5. Sun, J. et al. Cloud-scale molecular gas properties in
15 nearby galaxies. Astrophys. J. 860, 172–211 (2018).
6. Hughes, A. et al. A comparative study of giant
molecular clouds in M51, M33, and the Large
Magellanic Cloud. Astrophys. J. 779, 46–66 (2013).
7. Cava, A. et al. The nature of giant clumps in distant
galaxies probed by the anatomy of the Cosmic Snake.
Nat. Astron. 2, 76–82 (2018).
10
8. Tamburello, V., Mayer, L., Shen, S. & Wadsley,
J. A lower fragmentation mass scale in high-redshift
galaxies and its implications on giant clumps: a
systematic numerical study. Mon. Not. R. Astron. Soc.
453, 2490–2514 (2015).
9. Mandelker, N. et al. Giant clumps in simulated
high-z galaxies: properties, evolution and dependence
on feedback. Mon. Not. R. Astron. Soc. 464, 635–665
(2017).
10. Guo, Y. et al. Clumpy galaxies in CANDELS. I.
The definition of UV clumps and the fraction of
clumpy galaxies at 0.5 < z < 3. Astrophys. J. 800, 39–60
(2015).
11. Behroozi, P. S., Wechsler, R. H. & Conroy, C. The
average star formation histories of galaxies in dark
matter halos from z = 0–8. Astrophys. J. 770, 57–93
(2013).
12. Rodighiero, G. et al. The lesser role of starbursts in star
formation at z = 2. Astrophys. J. 739, L40–L46 (2011).
13. Patrício, V. et al. Kinematics, turbulence, and star
formation of z ~ 1 strongly lensed galaxies seen with
MUSE. Mon. Not. R. Astron. Soc. 477, 18–44 (2018).
14. Wisnioski, E. et al. The KMOS3D survey: design, first
results, and the evolution of galaxy kinematics from
0.7 ≤ z ≤ 2.7. Astrophys. J. 799, 209–236 (2015).
15. Dekel, A. et al. Cold streams in early massive hot
haloes as the main mode of galaxy formation. Nature
457, 451–454 (2009).
16. Ebeling, H. et al. A spectacular giant arc in the massive
cluster lens MACS J1206.2-0847. Mon. Not. R. Astron.
Soc. 395, 1213–1224 (2009).
17. Heyer, M., Krawczyk, C., Duval, J. & Jackson, J. M.
Re-examining Larson’s scaling relationships in galactic
molecular clouds. Astrophys. J. 699, 1092–1103
(2009).
18. Donovan Meyer, J. et al. Resolved giant molecular
clouds in nearby spiral galaxies: insights from the
CANON CO(1–0) survey. Astrophys. J. 772, 107–123
(2013).
19. Colombo, D. et al. The PdBI Arcsecond Whirlpool
Survey (PAWS): environmental dependence of giant
molecular cloud properties in M51. Astrophys. J. 784,
3–35 (2014).
20. Corbelli, E. et al. From molecules to young stellar
clusters: the star formation cycle across the disk of
M33. Astron. Astrophys. 601, 146–164 (2017).
21. Larson, R. B. Turbulence and star formation in
molecular clouds. Mon. Not. R. Astron. Soc. 194,
809–826 (1981).
22. Wei, L. H., Keto, E. & Ho, L. C. Two populations of
molecular clouds in the Antennae galaxies. Astrophys.
J. 750, 136–154 (2012).
23. Leroy, A. K. et al. ALMA reveals the molecular
medium fueling the nearest nuclear starburst.
Astrophys. J. 801, 25–53 (2015).
24. Bolatto, A. D., Wolfire, M. & Leroy, A. K. The
CO-to-H2 conversion factor. Annu. Rev. Astron.
Astrophys. 51, 207–268 (2013).
25. McKee, C. F. & Ostriker, E. C. Theory of star
formation. Annu. Rev. Astron. Astrophys. 45, 565–687
(2007).
26. Brunt, C. M., Heyer, M. H. & Mac Low, M.-M.
Turbulent driving scales in molecular clouds. Astron.
Astrophys. 504, 883–890 (2009).
27. Evans, N. J. II et al. The Spitzer c2d legacy results:
star-formation rates and efficiencies; evolution and
lifetimes. Astrophys. J. Suppl. 181, 321–350 (2009).
28. Grudić, M. Y. et al. When feedback fails: the scaling
and saturation of star formation efficiency. Mon. Not.
R. Astron. Soc. 475, 3511–3528 (2018).
29. Kruijssen, J. M. D. et al. What controls star formation
in the central 500 pc of the Galaxy? Mon. Not. R.
Astron. Soc. 440, 3370–3391 (2014).
30. Renaud, F., Boily, C. M., Fleck, J.-J., Naab, T. &
Theis, Ch. Star cluster survival and compressive tides
in Antennae-like mergers. Mon. Not. R. Astron. Soc.
391, L98–L102 (2008).
31. Jullo, E. et al. A Bayesian approach to strong lensing
modelling of galaxy clusters. New J. Phys. 9, 447
(2007).
32. McMullin, J. P., Waters, B., Schiebel, D., Young, W.
& Golap, K. in Astronomical Data Analysis Software
and Systems XVI, Vol. 376 (eds. Shaw, R. A. et al.) 127
(Astronomical Society of the Pacific, 2007).
33. Daddi, E. et al. CO excitation of normal star-forming
galaxies out to z = 1.5 as regulated by the properties of
their interstellar medium. Astron. Astrophys. 577,
A46–A65 (2015).
34. Walter, F. et al. ALMA Spectroscopic Survey in the
Hubble Ultra Deep Field: survey description.
Astrophys. J. 833, 67–82 (2016).
35. Hodge, J. A. et al. Kiloparsec-scale dust disks in highredshift luminous submillimeter galaxies. Astrophys. J.
833, 103–118 (2016).
36. Solomon, P. M., Downes, D., Radford, S. J. E. &
Barrett, J. W. The molecular interstellar medium in
ultraluminous infrared galaxies. Astrophys. J. 478,
144–161 (1997).
37. Solomon, P. M., Rivolo, A. R., Barrett, J. & Yahil, A.
Mass, luminosity, and line width relations of Galactic
molecular clouds. Astrophys. J. 319, 730–741 (1987).
38. Postman, M. et al. The cluster lensing and supernova
survey with Hubble: an overview. Astrophys. J. Suppl.
Ser. 199, 25–47 (2012).
39. Schaerer, D. & de Barros, S. On the physical properties
of z ~ 6–8 galaxies. Astron. Astrophys. 515, A73–A88
(2010).
40. Schaerer, D., de Barros, S. & Sklias, P. Properties of
z ~ 3–6 Lyman break galaxies. I. Testing star formation
histories and the SFR–mass relation with ALMA and
near-IR spectroscopy. Astron. Astrophys. 549, A4–A24
(2013).
41. Sklias, P. et al. Star formation histories, extinction, and
dust properties of strongly lensed z ~ 1.5–3 starforming galaxies from the Herschel Lensing Survey.
Astron. Astrophys. 561, A149–A176 (2014).
42. Bruzual, G. & Charlot, S. Stellar population synthesis
at the resolution of 2003. Mon. Not. R. Astron. Soc.
344, 1000–1028 (2003).
43. Salpeter, E. E. The luminosity function and stellar
evolution. Astrophys. J. 121, 161–167 (1955).
44. Elmegreen, B. G. Theory of starbursts in nuclear rings.
Rev. Mex. Astron. Astrofis. Conf. Ser. 6, 165 (1997).
45. Elmegreen, B. G. Molecular cloud formation by
gravitational instabilities in a clumpy interstellar
medium. Astrophys. J. 344, 306–310 (1989).