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Durham University

Department of Physics

Staff profile

Publication details for Professor Ian Smail

Chapman, S. C. Blain, A. W., Ivison, R. J. & Smail, I. R. (2003). A median redshift of 2.4 for galaxies bright at submillimetre wavelengths. Nature 422(6933): 695-698.

Author(s) from Durham


A significant fraction of the energy emitted in the early Universe came from very luminous galaxies that are largely hidden at optical wavelengths (because of interstellar dust grains); this energy now forms part of the cosmic background radiation at wavelengths near 1 mm (ref. 1). Some submillimetre (submm) galaxies have been resolved from the background radiation(2), but they have been difficult to study because of instrumental limitations(3). This has impeded the determination of their redshifts (z), which is a crucial element in understanding their nature and evolution(4). Here we report spectroscopic redshifts for ten submm galaxies that were identified using high-resolution radio observations(5-7). The median redshift for our sample is 2.4, with a quartile range of 1.9-2.8. This population therefore coexists with the peak activity of quasars, suggesting a close relationship between the growth of massive black holes and luminous dusty galaxies(8). The space density of submm galaxies at redshifts over 2 is about 1,000 times greater than that of similarly luminous galaxies in the present-day Universe, so they represent an important component of star formation at high redshifts.


1. Fixsen, D. J., Dwek, E., Mather, J. C., Bennett, C. L. & Shafer, R. A. The spectrum of the extragalactic
far-infrared background from the COBE FIRAS observations. Astrophys. J. 508, 123–128 (1998).
2. Smail, I., Ivison, R. J. & Blain, A.W. A deep submillimeter survey of lensing clusters: a new window on
galaxy formation and evolution. Astrophys. J. 490, L5–L8 (1997).
3. Smail, I., Ivison, R. J., Blain, A. W. & Kneib, J.-P. The nature of faint submillimetre-selected galaxies.
Mon. Not. R. Astron. Soc. 331, 495–520 (2002).
4. Blain, A.W., Smail, I., Ivison, R. J. & Kneib, J.-P. The history of star-formation in dusty galaxies. Mon.
Not. R. Astron. Soc. 302, 632–648 (1999).
5. Barger, A. J., Cowie, L. L. & Richards, E. A.Mapping the evolution of high-redshift dusty galaxies with
submillimeter observations of a radio-selected sample. Astron. J. 119, 2092–2109 (2000).
6. Chapman, S. C., Richards, E. A., Lewis, G. F., Wilson, G. & Barger, A. J. The nature of the bright
submillimeter galaxy population. Astrophys. J. 548, L147–L151 (2001).
7. Ivison, R. J. et al. Deep radio imaging of the SCUBA 8-mJy survey fields: submm source identifications
and redshift distribution. Mon. Not. R. Astron. Soc. 337, 1–25 (2002).
8. Boyle, B. J. et al. The 2dF QSO redshift survey—I. The optical luminosity function of quasi-stellar
objects. Mon. Not. R. Astron. Soc. 317, 1014–1022 (2000).
9. Cowie, L. L., Barger, A. J. & Kneib, J.-P. Faint submillimeter counts from deep 850 micron
observations of the lensing clusters A370, A851, and A2390. Astron. J. 123, 2197–2205 (2002).
10. Ivison, R. J. et al. A hyperluminous galaxy at z ˆ 2.8 found in a deep submillimetre survey. Mon. Not.
R. Astron. Soc. 298, 583–593 (1998).
11. Barger, A. J. et al. Redshift distribution of the faint submillimeter galaxy population. Astron. J. 117,
2656–2665 (1999).
12. Ivison, R. J. et al. The diversity of SCUBA-selected galaxies. Mon. Not. R. Astron. Soc. 315, 209–221
13. Richards, E. A. The nature of radio emission from distinct galaxies: The 1.4 GHz observations.
Astrophys. J. 533, 611–630 (2000).
14. Fomalont, E. B., Kellermann, K. I., Partridge, R. B., Windhorst, R. A. & Richards, E. A. The
microjansky sky at 8.4 GHz. Astron. J. 123, 2402–2416 (2002).
15. Barger, A. J. et al. Submillimetre-wavelength detection of dusty star-forming galaxies at high redshift.
Nature 394, 248–251 (1998).
16. Chapman, S. C. et al. The properties of microjansky radio sources in the HDF-N, SSA13, and
SSA22 fields. Astrophys. J. 585, 57–66 (2003).
17. Scott, S. E. et al. The SCUBA 8-mJy survey—I. Submillimetremaps, sources and number counts. Mon.
Not. R. Astron. Soc. 331, 817–837 (2002).
18. Chapman, S. C., Lewis, G. F., Scott, D., Borys, C. & Richards, E. A. Understanding the nature of the
optically faint radio sources and their connection to the submillimeter population. Astrophys. J. 570,
557–570 (2002).
19. Condon, J. Radio emission from ordinary galaxies. Annu. Rev. Astron. Astrophys. 30, 575–611
20. Barger, A. J. et al. X-ray, optical and infrared imaging and spectral properties of the 1-Ms Chandra
Deep Field North sources. Astron. J. 124, 1839–1885 (2002).
21. Steidel, C. C., Adelberger, K. L., Giavalisco, M., Dickinson, M. & Pettini, M. Lyman-break galaxies at
z . 4 and the evolution of the ultraviolet luminosity density at high redshift. Astrophys. J. 519, 1–17
22. Steidel, C. et al. The population of faint optically-selected AGN at z ,3. Astrophys. J. (in the press);
preprint available at (2002).
23. Blain, A.W., Smail, I., Ivison, R. J., Kneib, J.-P. & Frayer, D. T. Submillimeter galaxies. Phys. Rep. 369,
111–196 (2002); preprint available at (2002).
24. Kennicutt, R. C. Star formation in galaxies along the Hubble sequence. Annu. Rev. Astron. Astrophys.
36, 189–232 (1998).
25. Pettini, M. et al. The rest-frame optical spectra of Lyman-break galaxies: star formation, extinction,
abundances and kinematics. Astrophys. J. 554, 981–1000 (2001).
26. Chapman, S. C., Smail, I., Ivison, R. & Blain, A. The effect of lensing on the identification of SCUBA
galaxies. Mon. Not. R. Astron. Soc. 335, 17–21 (2002).
27. Sheinis, A. I. et al. ESI, a new Keck Observatory echellette spectrograph and imager. Publ. Astron. Soc.
Pacif. 114, 851–865 (2002).
28. Oke, J. B. et al. The Keck low-resolution imaging spectrometer. Publ. Astron. Soc. Pacif. 107, 375–385
29. Chapman, S. C., Helou, G., Lewis, G. F. & Dale, D. The bi-variate luminosity-colour distribution of
IRAS galaxies, and implications for the high redshift Universe. Astrophys. J. (in the press); preprint
available at (2002).
30. Smail, I. et al. A vigorous starburst in the SCUBA galaxy N2_850.4. Mon. Nat. R. Astron. Soc. (in the
press); preprint available at (2003).