Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies

Abstract

Starburst galaxies at the peak of cosmic star formation1 are among the most extreme star-forming engines in the Universe, producing stars over about 100 million years (ref. 2). The star-formation rates of these galaxies, which exceed 100 solar masses per year, require large reservoirs of cold molecular gas3 to be delivered to their cores, despite strong feedback from stars or active galactic nuclei4,5. Consequently, starburst galaxies are ideal for studying the interplay between this feedback and the growth of a galaxy6. The methylidyne cation, CH+, is a most useful molecule for such studies because it cannot form in cold gas without suprathermal energy input, so its presence indicates dissipation of mechanical energy7,8,9 or strong ultraviolet irradiation10,11. Here we report the detection of CH+ (J = 1–0) emission and absorption lines in the spectra of six lensed starburst galaxies12,13,14,15 at redshifts near 2.5. This line has such a high critical density for excitation that it is emitted only in very dense gas, and is absorbed in low-density gas10. We find that the CH+ emission lines, which are broader than 1,000 kilometres per second, originate in dense shock waves powered by hot galactic winds. The CH+ absorption lines reveal highly turbulent reservoirs of cool (about 100 kelvin), low-density gas, extending far (more than 10 kiloparsecs) outside the starburst galaxies (which have radii of less than 1 kiloparsec). We show that the galactic winds sustain turbulence in the 10-kiloparsec-scale environments of the galaxies, processing these environments into multiphase, gravitationally bound reservoirs. However, the mass outflow rates are found to be insufficient to balance the star-formation rates. Another mass input is therefore required for these reservoirs, which could be provided by ongoing mergers16 or cold-stream accretion17,18. Our results suggest that galactic feedback, coupled jointly to turbulence and gravity, extends the starburst phase of a galaxy instead of quenching it.

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Figure 1: Rest-frame 360-μm continuum images of our lensed targets.
Figure 2: CH+ J = 1–0 spectra of our lensed targets.

References

  1. 1

    Madau, P. & Dickinson, M. Cosmic star-formation history. Annu. Rev. Astron. Astrophys. 52, 415–486 (2014)

  2. 2

    Tacconi, L. J. et al. Submillimeter galaxies at z ~ 2: evidence for major mergers and constraints on lifetimes, IMF and CO-to-H2 conversion factor. Astrophys. J. 680, 246–262 (2008)

  3. 3

    Carilli, C. L. & Walter, F. Cool gas in high-redshift galaxies. Annu. Rev. Astron. Astrophys. 51, 105–161 (2013)

  4. 4

    Veilleux, S., Cecil, G. & Bland-Hawthorn, J. Galactic winds. Annu. Rev. Astron. Astrophys. 43, 769–826 (2005)

  5. 5

    Förster Schreiber, N. M . et al. The SINS/zC-SINF survey of z ~ 2 galaxy kinematics: evidence for powerful active galactic nucleus-driven nuclear outflows in massive star-forming galaxies. Astrophys. J. 787, 38 (2014)

  6. 6

    Somerville, R. S. & Davé, R. Physical models of galaxy formation in a cosmological framework. Annu. Rev. Astron. Astrophys. 53, 51–113 (2015)

  7. 7

    Flower, D. & Pineau des Forêts, G. C-type shocks in the interstellar medium: profiles of CH+ and CH absorption lines. Mon. Not. R. Astron. Soc. 297, 1182–1188 (1998)

  8. 8

    Lesaffre, P. et al. Low-velocity shocks: signatures of turbulent dissipation in diffuse irradiated gas. Astron. Astrophys. 550, A106 (2013)

  9. 9

    Godard, B., & Falgarone, E. & Pineau des Forêts, G. Chemical probes of turbulence in the diffuse medium: the TDR model. Astron. Astrophys. 570, A27 (2014)

  10. 10

    Godard, B. & Cernicharo, J. A complete model of CH+ rotational excitation including radiative and chemical pumping processes. Astron. Astrophys. 550, A8 (2013)

  11. 11

    Falgarone, E. et al. Strong CH+J = 1–0 emission and absorption in DR21. Astron. Astrophys. 518, L118 (2010)

  12. 12

    Eales, S. et al. The Herschel ATLAS. Publ. Astron. Soc. Pac. 122, 499–515 (2010)

  13. 13

    Negrello, M. et al. The detection of a population of submillimeter-bright, strongly lensed galaxies. Science 330, 800–804 (2010)

  14. 14

    Bussmann, R. S. et al. Gravitational lens models based on submillimeter array imaging of Herschel-selected strongly lensed sub-millimeter galaxies at z > 1.5. Astrophys. J. 779, 25 (2013)

  15. 15

    Swinbank, A. M. et al. Intense star formation within resolved compact regions in a galaxy at z = 2.3. Nature 464, 733–736 (2010)

  16. 16

    Engel, H. et al. Most submillimeter galaxies are major mergers. Astrophys. J. 724, 233–243 (2010)

  17. 17

    Dekel, A. et al. Cold streams in early massive hot haloes as the main mode of galaxy formation. Nature 457, 451–454 (2009)

  18. 18

    Narayanan, D. et al. The formation of submillimetre-bright galaxies from gas infall over a billion years. Nature 525, 496–499 (2015)

  19. 19

    Schreiber, C. et al. The Herschel view of the dominant mode of galaxy growth from z = 4 to the present day. Astron. Astrophys. 575, A74 (2015)

  20. 20

    George, R. D. et al. Herschel reveals a molecular outflow in a z = 2.3 ULIRG. Mon. Not. R. Astron. Soc. 442, 1877–1883 (2014)

  21. 21

    Harris, A. I. et al. Blind detections of CO J = 1–0 in 11 H-ATLAS galaxies at z = 2.1–3.5 with the GBT/Zpectrometer. Astrophys. J. 752, 152 (2012)

  22. 22

    Lupu, R. E. et al. Measurements of CO redshifts with Z-Spec for lensed submillimeter galaxies discovered in the H-ATLAS survey. Astrophys. J. 757, 135 (2012)

  23. 23

    Omont, A. et al. H2O emission in high-z ultra-luminous infrared galaxies. Astron. Astrophys. 551, A115 (2013)

  24. 24

    Swinbank, A. M. et al. The interstellar medium in distant star-forming galaxies: turbulent pressure, fragmentation, and cloud scaling relations in a dense gas disk at z = 2.3. Astrophys. J. 742, 11 (2011)

  25. 25

    Negrello, M. et al. Herschel-ATLAS: deep HST/WFC3 imaging of strongly lensed submillimetre galaxies. Mon. Not. R. Astron. Soc. 440, 1999–2012 (2014)

  26. 26

    Hollenbach, D. & McKee, C. F. Molecule formation and infrared emission in fast interstellar shocks. III. Results for J shocks in molecular clouds. Astrophys. J. 342, 306–336 (1989)

  27. 27

    Appleton, P. N. et al. Shock-enhanced C+ emission and the detection of H2O from the Stephan’s Quintet group-wide shock using Herschel. Astrophys. J. 777, 66 (2013)

  28. 28

    Bouché, N. et al. The impact of cold gas accretion above a mass floor on galaxy scaling relations. Astrophys. J. 718, 1001–1018 (2010)

  29. 29

    Borisova, E. et al. Ubiquitous giant Lyα nebulae around the brightest quasars at z ~ 3.5 revealed with MUSE. Astrophys. J. 831, 39 (2016)

  30. 30

    Planck Collaboration. Planck 2013 results. XVI. Cosmological parameters. Astron. Astrophys. 571, A16 (2014)

  31. 31

    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, 1687–1702 (2011)

  32. 32

    Yang, C. et al. Submillimeter H2O and H2O+ emission in lensed ultra-luminous infrared galaxies at z ~ 2–4. Astron. Astrophys. 595, A80 (2016)

  33. 33

    Calanog, J. A. et al. Lens models of Herschel-selected galaxies from high-resolution near-IR observations. Astrophys. J. 797, 138 (2014)

  34. 34

    Douglas, A. E. & Herzberg, G. CH+ in interstellar space and in the laboratory. Astrophys. J. 94, 381 (1941)

  35. 35

    Falgarone, E. et al. CH+ (1–0) and 13CH+ (1–0) absorption lines in the direction of massive star-forming regions. Astron. Astrophys. 521, L15 (2010)

  36. 36

    Godard, B. et al. Comparative study of CH+ and SH+ absorption lines observed towards distant star-forming regions. Astron. Astrophys. 540, A87 (2012)

  37. 37

    Naylor, D. A. et al. First detection of the methylidyne cation (CH+) fundamental rotational line with the Herschel/SPIRE FTS. Astron. Astrophys. 518, L117 (2010)

  38. 38

    van der Werf, P. P. et al. Black hole accretion and star formation as drivers of gas excitation and chemistry in Markarian 231. Astron. Astrophys. 518, L42 (2010)

  39. 39

    Spinoglio, L. et al. Submillimeter line spectrum of the seyfert galaxy NGC 1068 from the Herschel-SPIRE Fourier transform spectrometer. Astrophys. J. 758, 108 (2012)

  40. 40

    Rangwala, N. et al. Observations of Arp 220 using Herschel-SPIRE: an unprecedented view of the molecular gas in an extreme star formation environment. Astrophys. J. 743, 94 (2011)

  41. 41

    Ritchey, A. M. et al. Diffuse atomic and molecular gas in the interstellar medium of M82 toward SN 2014. J. Astrophys. J. 799, 197 (2015)

  42. 42

    Hennebelle, P. & Falgarone, E. Turbulent molecular clouds. Astron. Astrophys. Rev. 20, 55–113 (2012)

  43. 43

    Kritsuk, A. G., Lee, C. T. & Norman, M. L. A supersonic turbulence origin of Larson’s laws. Mon. Not. R. Astron. Soc. 436, 3247–3261 (2013)

  44. 44

    Gerin, M. et al. [C II] absorption and emission in the diffuse interstellar medium across the Galactic plane. Astron. Astrophys. 573, A30 (2015)

  45. 45

    Bothwell, M. S. et al. Molecular gas as the driver of fundamental galactic relations. Mon. Not. R. Astron. Soc. 455, 1156–1170 (2016)

  46. 46

    Gonzalez-Alfonso, E., Smith, H. A., Fischer, J. & Cernicharo, J. The far-infrared spectrum of Arp 220. Astrophys. J. 613, 247–261 (2004)

  47. 47

    Martin, C. Mapping large-scale gaseous outflows in ultraluminous galaxies with Keck II ESI spectra: variations in outflow velocity with galactic mass. Astrophys. J. 621, 227–245 (2005)

  48. 48

    Ivison, R. J. et al. Tracing the molecular gas in distant submillimetre galaxies via CO(1–0) imaging with the Expanded Very Large Array. Mon. Not. R. Astron. Soc. 412, 1913–1925 (2011)

  49. 49

    Wisotzki, L. et al. Extended Lyman α haloes around individual high-redshift galaxies revealed by MUSE. Astron. Astrophys. 587, A98 (2016)

  50. 50

    Guillard, P. et al. Turbulent molecular gas and star formation in the shocked intergalactic medium of Stephan’s Quintet. Astrophys. J. 749, 158 (2012)

  51. 51

    Shull, J. M., Stevans, M. & Danforth, C. W. HST-COS observations of AGNs. I. Ultraviolet composite spectra of the ionizing continuum and emission lines. Astrophys. J. 752, 162 (2012)

  52. 52

    van der Tak, F. F. S. A computer program for fast non-LTE analysis of interstellar line spectra. Astron. Astrophys. 468, 627–635 (2007)

  53. 53

    Omont, A. et al. Observation of H2O in a strongly lensed Herschel-ATLAS source at z = 2.32011. Astron. Astrophys. 530, L3 (2011)

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Acknowledgements

ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. NRAO is a facility of the NSF operated under cooperative agreement by Associated Universities, Inc. R.J.I. acknowledges support from the ERC in the form of the Advanced Investigator Programme, 321302, COSMICISM. E.F. and B.G. acknowledge support from the national CNRS programme Physique et Chimie du Milieu Interstellaire (PCMI).

Author information

E.F., E.B., F.B. and D.E. conceived the initial scientific argument and wrote the ALMA proposal with B.G., M.A.Z., P.M.A., A.O. and R.S.B. M.A.Z. reduced the ALMA data. B.G. and E.F. analysed the spectra. B.G. provided the results of the shock models. R.J.I., I.O. and F.W. were invited to join the team at a later stage to provide the results of the lens models (I.O.) and to contribute to a year-long debate on the data interpretation. E.F. wrote the paper with contributions from all authors.

Correspondence to E. Falgarone.

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Extended data figures and tables

Extended Data Figure 1 Position–velocity diagrams of CH+emission and absorption along selected cuts across the sources.

The cuts are made along the east–west direction for G09v1.40, NAv1.56 and NAv1.144, along the long axis of the lensed images for the Eyelash, and along a northeast–southwest direction for SDP17b. CH+ emission appears in white (blue contours) and absorption in black (green contours). The first contour level and steps are 2σ. A velocity gradient is seen in the absorption of the Eyelash that is two times smaller than that detected in CO (ref. 24).

Extended Data Figure 2 CH+ emission and absorption overlaid on dust continuum emission for the Eyelash, SDP17b and G09v1.40.

The integrated emission (blue contours) and absorption (red contours) of the CH+ lines, with contour levels in steps of 2σ, are overlaid on continuum emission (grey scale). All of the images are lensed and so the differences between the distribution of dust continuum and CH+ line emission are affected by differential lensing.

Extended Data Figure 3

As in Extended Data Fig. 2, but for NAv1.56, NAv1.144 and SDP130. Only emission is detected for SDP130.

Extended Data Table 1 Additional properties of the lensed SMGs

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Falgarone, E., Zwaan, M., Godard, B. et al. Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies. Nature 548, 430–433 (2017). https://doi.org/10.1038/nature23298

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