Home Research Current Publications Gallery Morphs Group


The HiZELS Survey

HiZELS was a panoramic extragalactic survey using the WFCAM instrument on the 3.8-m UK Infrared Telescope (UKIRT). The survey utilized a set of existing and custom-made narrow-band filters in the J, H and K-bands to detect emission line galaxies at z = 1-9 over ~10 square degrees of extragalactic sky in the UKIDSS DXS survey regions. Strong emission line galaxies include both strongly star-forming galaxies and systems where Active Galactic Nuclei (AGN) contribute signficant line emission. We employed the H2(S1) narrow-band filter to target H-alpha emitting galaxies at z=2.23, which are likely to be predominantly star-forming systems. In addition, in anticipation of this survey, we used funds from PPARC and the Royal Society to purchase specially designed narrow-band filters targeting the [OII] emission line at 3727A and the [OIII] line at 5007A, in galaxies at the same redshift as the H-alpha survey. Together these three sets of filters enabled us to investigate the [OII] 3727, [OIII] 5007 and H-alpha emission from galaxies at z=2.23 to distinguish star-forming systems from AGN, while the J- and H-band filters delivered identically-selected H-alpha samples at z=0.84 and 1.47 respectively. The comparisons between the luminosity function, the clustering and variation with environment of these H-alpha-selected samples across z=0.8-2.2 yielded unique constraints on the evolution of star-forming galaxies. More speculatively, the J-band filter is sensitive to Ly-alpha emission from galaxies at z=8.90 and the limits we placed on detections provided a constraint on the theoretical predictions.

HiZELS selected sources were subsequently used in a wide variety of studies. Most notably the wide-field coverage enabled us to select targets near bright stars, to use these as Adaptive Optics beacons to improve the spatial resolution of observations of these target galaxies. The large uniform sample also became the basis for various KMOS Guaranteed Time Projects on ESO's Very Large Telescope, including KROSS and KGES.

Emission-line surveys are a particularly powerful method for tracing the evolution of star formation (and to a lesser extent AGN activity) as a function of cosmic epoch. With the advent of large-format imaging cameras in the optical and more recently in the near-infrared, narrow-band filters are being increasingly exploited to undertake sensitive and unbiased surveys for emission-line objects lying in well-defined large volumes across the relevant redshift range (out to z~2.5), yielding thousands of sources. The main benefits of such surveys for studies of star formation are that the sources are identified on the strength of their emission line and thus crudely represent a star-formation rate-selected sample, and that they must lie in a narrow range in redshift. Hence, using a number of narrow-band filters it is possible to apply a single technique to target H-alpha emitters across a wide range of redshifts, yielding large and representative samples at each epoch and with a uniform selection function. Such samples are ideal for tracing the evolution in the star-formation rate density across the era of peak activity in galaxies.

It is not only the global average star formation rate which is important for our understanding of galaxy formation and evolution, but more crucially the nature and distribution of the star forming galaxies at high redshifts. Many results point towards the star formation in the most massive galaxies occurring earlier than that in lower mass galaxies - so-called down-sizing, although the epoch of star formation of the most massive galaxies is currently poorly constrained. At low redshift, the star formation rates of galaxies are also greatly influenced by the environment in which they reside with star formation strongly suppressed in dense environments. To what extent is it the build-up of galaxies into groups and clusters since z~1 that drives the decline in the cosmic star formation rate? This question can only be addressed by examining how the relationship between star-formation rate and environment evolves with redshift. Large H-alpha surveys over the redshift range z = 0-2 provide an uniquely powerful tool for measuring the growing influence of environment on star-forming galaxies, and constrain how the characteristic stellar mass of star forming galaxies changes with epoch. Such observations yield key tests of galaxy formation models, such as the GALFORM semi-analytic model developed in Durham. We demonstrate this with the figure which compares the clustering strength of emission-line selected galaxies predicted by two flavours of the GALFORM code (which differ in the way they handle merging and feedback) and which show significantly different clustering properties for these strongly star-forming galaxies at high redshifts.

HiZELS was roughly two orders of magnitude larger than previous near-infrared, narrow-band surveys. It detected several thousand H-alpha emitting galaxies at each of three redshifts (0.84, 1.47 and 2.23) spanning the likely peak in the star formation density of the Universe (Sobral et al. 2013). This was the first time that the luminosity function of star-forming galaxies has been accurately determined at these epochs in a robust and uniform manner, and pin-pointed the epoch when the star-formation density of the Universe peaked. The angular cross-correlation function of the star-forming galaxies, and its evolution with redshift, were determined with sufficient accuracy to place tight constraints upon models of galaxy formation. The survey also measured the growing influence of environment on star-forming galaxies, and variations in the characteristic mass of the most active galaxies.

HiZELS was allocated a total of 700 hours of time on UKIRT, of which 110 hours was used for a pilot study covering 1.5 square degrees in the COSMOS and UKIDSS/UDS fields. The original science case for the HiZELS survey is here.

The co-PIs HiZELS are Philip Best (IfA, Edinburgh) and Ian Smail (CEA, Durham), with much of the early work done by David Sobral, Jim Geach and a long list of others, including (but not limited to): John Stott, Alastair Edge, Mark Swinbank, Yuichi Matsuda, Jaron Kurk, Mark Casali, Rob Ivison, Gavin Dalton, Kristen Coppin, Michele Cirasuolo, Tim Garn, Carlton Baugh, Ryan Hickox, David Wake.

HiZELS-related publications, including those from spectroscopic and ALMA follow-up, with substantial Durham contributions are listed here:

45)  ``Resolving a dusty, star-forming SHiZELS galaxy at z=2.2 with HST, ALMA and SINFONI on kiloparsec scales'', Cochrane, R.K., Best, P.N., Smail, I., Ibar, E., Cheng, C., Swinbank, A.M., Molina, J., Sobral, D., Dudzeviciute, U., 2021, MNRAS, submitted. PDF version, Abstract.

44)  ``Dust, gas and metal content in star-forming galaxies at z~3.3 revealed with ALMA and near-IR spectroscopy'', Suzuki, T.L., Onodera, M., Kodama, T., Daddi, E., Hayashi, M., Koyama, Y., Shimakawa, R., Smail, I., Sobral, D., Tacchella, S., Tanaka, I., 2021, ApJ, in press. PDF version, Abstract.

43)  ``A spatially resolved view at ~kpc scale of the star-formation activity in normal SHiZELS galaxies at z=1.5 and 2.2'', Cheng, C., Ibar, E., Smail, I., Molina, J., Sobral, D., Escala, A., Best, P., Cochrane, R., Gillman, S., Swinbank, A.M., Ivison, R.J., Huang, J.-S., Hughes, T.M., Villard, E., Cirasuolo, M., 2020, MNRAS, 499, 5241-5256. PDF version, Abstract.

42)  ``VIS3COS II: Environment effects on [OII], H-delta, Dn4000 and their consequence for the star formation histories at z~0.8'', Paulino-Alfonso, A., Sobral, D., Darvish, B., Smail, I., Best, P., Stroe, A., Cairns, J., 2020, A&A, 633, 70-88. PDF version, Abstract.

41)  ``The kpc-scale gas kinematics in two star-forming galaxies at z~1.47 seen with ALMA and VLT-SINFONI'', Molina, J., Ibar, E., Smail, I., Swinbank, A.M., Villard, E., Escala, A., Sobral, D., Hughes, T.M., 2019, MNRAS, 487, 4856-4869. PDF version, Abstract.

40)  ``The dynamics and distribution of angular momentum in star-forming galaxies at z=0.8-3.3'', Gillman, S., Swinbank, A.M., Tiley, A., Harrison, C.M., Smail, I., Dudzevictiute, U., Sharples, R.M., Best, P.N., Bower, R.G., Cochrane, R., Fisher, D., Geach, J.E., Glazebrook, K., Ibar, E., Molina, J., Obreschkow, D., Schaller, M., Sobral, D., Sweet, S., Trayford, J., Theuns, T., 2019, MNRAS, 486, 175-194. PDF version, Abstract.

39)  ``The clustering of H-beta+[OIII] and [OII] emitters since z~5: dependencies with line luminosity and stellar mass'', Khostovan, A.A., Sobral, D., Mobasher, B., Best, P., Smail, I., Matthee, J., Darvish, B., Nayyeri, H., Hemmati, S., Stott, J.P., 2018, MNRAS, 478, 2999-3015. PDF version, Abstract.

38)  ``The nature of luminous Ly-alpha emitters at z ~ 2-3: maximal dust-poor starbursts and highly ionising AGN'', Sobral, D., Matthee, J., Darvish, B., Smail, I., Best, P.N., Alegra, L., Rottgering, H., Mobasher, B., Paulino-Afonso, A., Stroe, A., Oteo, I., 2018, MNRAS, 477, 2817-2840. PDF version, Abstract.

37)  ``The dependence of galaxy clustering on stellar mass, star-formation rate and redshift at z=0.8-2.2, with HiZELS'', Cochrane, R.K., Best, P.N., Sobral, D., Smail, I., Geach, J.E., Stott, J.P., Wake, D.A., 2018, MNRAS, 475, 3730-3745. PDF version, Abstract.

36)  ``The interstellar medium in [OIII]-selected star-forming galaxies at z~3.2'', Suzuki, T.L., Kodama, T., Onodera, M., Shimawaka, R., Hayashi, M., Tadaki, K.-I., Koyama, Y., Tanaka, I., Sobral, D., Smail, I., Best, P.N., Khostovan, A.A., Minowa, Y., Yamamoto, M., 2017, ApJ, 849, 39-54. PDF version, Abstract.

35)  ``Bootes-HiZELS: an optical to near-infrared survey of emission-line galaxies at z=0.4-4.7'', Matthee, J., Sobral, D., Best, P., Smail, I., Bian, F., Darvish, B., Rottgering, H., Fan, X., 2017, MNRAS, 471, 629-649. PDF version, Abstract.

34)  ``The H-alpha luminosity-dependent clustering of star-forming galaxies from z~0.8 to z~2.2 with HiZELS'', Cochrane, R.K., Best, P.N., Sobral, D., Smail, I., Wake, D.A., Stott, J.P., Geach, J.E., 2017, MNRAS, 469, 2913-2932. PDF version, Abstract.

33)  ``The CALYMHA survey: Lyman-alpha luminosity function and global escape fraction of Lyman-alpha photons at z=2.23'', Sobral, D., Matthee, J., Best, P.N., Stroe, A., Rottgering, H., Oteo, I., Morabito, L., Paulino-Afonso, A., Santos, S., Smail, I., 2017, MNRAS, 466, 1242-1258. PDF version, Abstract.

32)  ``SINFONI-HiZELS: The dynamics, merger rates and metallicity gradients of `typical' star-forming galaxies at z=0.8-2.2'', Molina, J., Ibar, E., Swinbank, A.M., Sobral, D., Best, P.N., Smail, I., Escala, A., Cirasuolo, M., 2017, MNRAS, 466, 892-905. PDF version, Abstract.

31)  ``Evolution of dust-obscured star formation and gas to z=2.2 from HiZELS'', Thomson, A.P., Simpson, J.M., Smail, I., Swinbank, A.M., Best, P.N., Sobral, D., Geach, J.E., Ibar, E., Johnson, H.L., 2017, ApJ, 838, 119-134.

30)  ``ALMACAL II: Extreme star-formation-rate densities in a pair of dusty starbursts at z=3.442 revealed by ALMA 20-milliarcsec resolution imaging'', Oteo, I., Zwaan, M.A., Ivison, R.J., Smail, I., Biggs, A.D., 2017, ApJ, 837, 182-190. PDF version, Abstract.

29)  ``The growth of typical star-forming galaxies and their supermassive black holes across cosmic time since z~2'', Calhau, J., Sobral, D., Stroe, A., Best, P., Smail, I., Lehmer, B., Harrison, C.M., Thomson, A., 2017, MNRAS, 464, 303-311. PDF version, Abstract.

28)  ``The nature of H-beta+[OIII] and [OII] emitters to z~5 with HiZELS: Stellar mass functions and the evolution of EWs'', Khostovan, A.A., Sobral, D., Mobasher, B., Smail, I., Darvish, B., Nayyeri, H., Hemmati, S., Stott, J.P., 2016, MNRAS, 463, 2363-2382. PDF version, Abstract.

27)  ``[OIII] emission line as a powerful tracer of star-forming galaxies at high redshifts: Comparison between H-alpha and [OIII] emitters at z~2 in HiZELS'', Suzuki, T.L., Kodama, T., Sobral, D., Khostovan, A.A., Hayashi, M., Shimakawa, R., Koyama, Y., Tadaki, K.-I., Tanaka, I., Minowa, Y., Yamamoto, M., Smail, I., Best, P.N., 2016, MNRAS, 462, 181-189. PDF version, Abstract.

26)  ``The CALYMHA survey: The Ly-alpha escape fraction and its dependence on galaxy properties at z=2.23'', Matthee, J., Sobral, D., Oteo, I., Best, P., Smail, I., Rottgering, H., Paulino-Afonso, A., 2016, MNRAS, 458, 449-467. PDF version, Abstract.

25)  ``The most luminous H-alpha emitters at z~0.8-2.23 from HizELS: Evolution of AGN and star-forming galaxies'', Sobral, D., Kohn, S.A., Best, P.N., Smail, I., Harrison, C.M., Stott, J., Calhau, J., Matthee, J. 2016, MNRAS, 457, 1739-1752. PDF version, Abstract.

24)  ``Evolution of the H-beta+[OIII] and [OII] luminosity functions and the [OII] star-formation history of the Universe up to z~5 from HiZELS'', Khostovan, A.A., Sobral, D., Mobasher, B., Best, P.N., Smail, I., Stott, J.P., Hemmati, S., Nayyeri, H., 2015, MNRAS, 452, 3948-3968. PDF version, Abstract.

23)  ``On the nature of H-alpha emitters at z~2 from the HiZELS survey: Physical properties and comparison with LAEs, BzKs and LBGs'', Oteo, I., Sobral, D., Ivison, R.J., Smail, I., Cepa, J., Best, P., Perez-Garcia, A.M., 2015, MNRAS, 452, 2018-2033. PDF version, Abstract.

22)  ``CF-HiZELS, a 10 deg^2 emission-line survey with spectroscopic follow-up: H-alpha, [OIII]+H-beta and [OII] luminosity functions at z=0.8, 1.4 and 2.2'', Sobral, D., Matthee, J., Best, P.N., Smail, I., Khostovan, A.A., Milvang-Jensen, B., Kim, J.-W., Stott, J., Calhau, J., Nayyeri, H., Mobasher, B., 2015, MNRAS, 451, 2303-2323. PDF version, Abstract.

21)  ``The relationship between the cosmic web and star formation activity in galaxies at z~1'', Darvish, B., Sobral, D., Mobasher, B., Scoville, N.Z., Best, P., Sales, L.V., Smail, I., 2014, ApJ, 796, 51-63. PDF version, Abstract.

20)  ``A relationship between specific star formation rate and metallicity gradient within z~1 galaxies from KMOS-HiZELS'', Stott, J.P., Sobral, D., Swinbank, A.M., Smail, I., Bower, R., Best, P.N., Sharples, R.M., Geach, J.E., Matthee, J., 2014, MNRAS, 443, 2695-2704. PDF version, Abstract.

19)  ``A 10 deg^2 Lyman-alpha survey at z=8.8 with spectroscopic follow-up: Strong constraints on the LF and implications for other surveys'', Matthee, J.J.A., Sobral, D., Swinbank, A.M., Smail, I., Best, P.N., Kim, J.-W., Franx, M., Milvang-Jensen, B., Fynbo, J., 2014, MNRAS, 440, 2375-2387. PDF version, Abstract.

18)  ``The evolution of the mass function of star-forming galaxies and the mass-dependent SFR function since z=2.23'', Sobral, D., Best, P.N., Smail, I., Mobasher, B., Stott, J.P., Nisbet, D., 2014, MNRAS, 437, 3516-3528. PDF version, Abstract.

17)  ``A fundamental metallicity relation for galaxies at z=0.84-1.47 from HiZELS'', Stott, J.P., Sobral, D., Bower, R.G., Smail, I., Best, P., Matsuda, Y., Hayashi, M., Geach, J., Kodama, T., 2013, MNRAS, 436, 1130-1141. Postscript version, PDF version, Abstract.

16)  ``The dynamics of z=0.8 Halpha-selected star-forming galaxies from KMOS/CF-HiZELS'', Sobral, D., Swinbank, A.M., Stott, J.P., Matthee, J., Bower, R.G., Smail, I., Best, P., Geach J.E., Sharples, R.M., 2013, ApJ, 779, 139-146. PDF version, Abstract.

15)  ``Herschel reveals the obscured star formation in HiZELS H-alpha emitters at z=1.47'', Ibar, E., Sobral, D., Best, P.N., Ivison, R.J., Smail, I., Arumugam, V., Berta, S., Bethermin, M., Bock, J., Cava, A., Conley, A., Farrah, D., Le Floc'h, E., Lutz, D., Magdis, G., Magnelli, B., Ikarashi, S., Khono, K., Marsden, G., Oliver, S.J., Page, M.J., Pozzi, F., Riguccini, L., Schulz, B., Seymour, N., Smith, A.J., Symeonidis, M., Wang, L., Wardlow, J., Zemcov, M., 2013, MNRAS, 434, 3218-3235. Postscript version, PDF version, Abstract.

14)  ``The merger rates and sizes of galaxies across the peak epoch of star formation from the HiZELS survey'', Stott, J.P., Sobral, D., Smail, I., Bower, R.G., Best, P.N., Geach, J.E., 2013, MNRAS, 430, 1158-1170. Postscript version, PDF version, Abstract.

13)  ``The nature of faint [OII] emitters at z=1.47 revealed by dual H-alpha/[OII] imaging from HiZELS'', Hayashi, M., Sobral, D., Best, P.N., Smail, I., Kodama, T., 2013, MNRAS, 430, 1042-1050. Postscript version, PDF version, Abstract.

12)  ``A large, multi-epoch H-alpha survey at z=2.23, 1.47, 0.84 & 0.40: the 11 Gyr evolution of star-forming galaxies from HiZELS'', Sobral, D., Smail, I., Best, P.N., Geach, J.E., Matsuda, Y., Stott, J.P., Cirasuolo, M., Kurk, J., 2013, MNRAS, 428, 1128-1146. Postscript version, PDF version, Abstract.

11)  ``The properties of the star-forming interstellar medium at z=0.84-2.23 from HiZELS: Star-formation and clump scaling laws in gas rich, turbulent disks'', Swinbank, A.M., Smail, I., Sobral, D., Best, P.N., Geach, J.E., Theuns, T., 2012, ApJ, 760, 130. Postscript version, PDF version, Abstract.

10)  ``The properties of the star-forming interstellar medium at z=0.84-2.23 from HiZELS: Mapping the internal dynamics and metallicity gradients in high-redshift disk galaxies'', Swinbank, A.M., Sobral, D., Smail, I., Geach, J.E., Best, P.N., McCarthy, I., Crain, R.A., Theuns, T., 2012, MNRAS, 426, 935-950. Postscript version, PDF version, Abstract.

9)  ``The clustering of H-alpha emitters at z=2.23 from HiZELS'', Geach, J.E., Sobral, D., Hickox, R.C., Wake, D.A., Smail, I., Best, P.N., Baugh, C.M., Stott, J.P., 2012, MNRAS, 426, 679-689. Postscript version, PDF version, Abstract.

8)  ``Star Formation at z=1.47 from HiZELS: An H-alpha+[OII] Double Blind Study'', Sobral, D., Best, P.N., Matsuda, Y., Smail, I., Geach, J.E., Cirasuolo, M., 2012, MNRAS, 420, 1926-1945. Postscript version, PDF version, Abstract.

7)  ``An H-alpha search for over-dense regions at z=2.23'', Matsuda, Y., Smail, I., Geach, J.E., Best, P.N., Sobral, D., Tanaka, I., Ohta, K., Kurk, J., Iwata, I., Bielby, R., Wardlow, J.L., Bower, R.G., Fanidakis, N., Ivison, R.J., Kodama, T., Yamada, T., Mawatari, K., Casali, M., 2011, MNRAS, 416, 2041-2059. Postscript version, PDF version, Abstract.

6)  ``The Dependence of Star Formation Activity on Environment and Stellar Mass at z~1 from the HiZELS-Halpha Survey'', Sobral, D., Best, P.N., Smail, I., Geach, J.E., Cirasuolo, M., Garn, T., Dalton, G., 2011, MNRAS, 411, 685-692. Postscript version, PDF version, Abstract.

5)  ``The clustering and evolution of H-alpha emitters at z~1 from HiZELS'', Sobral, D., Best, P.N., Geach, J.E., Smail, I., Cirasuolo, M., Garn, T., Dalton, G.D., Kurk, J., 2010, MNRAS, 404, 1551-1563. Postscript version, PDF version, Abstract.

4)  ``Obscured star formation at z=0.84 with HiZELS: The relationship between star formation rate and H-alpha or ultra-violet dust extinction'', Garn. T., Sobral, D., Best, P.N., Geach, J.E., Smail, I., Cirasuolo, M., Dalton, G.D., Dunlop, J.S., McLure, R.J., Farrah, D., 2010, MNRAS, 402, 2017-2030. Postscript version, PDF version, Abstract.

3)  ``Bright Ly-alpha Emitters at z~9: Constraints on the Luminosity Function from HiZELS'', Sobral, D., Best, P.N., Geach, J.E., Smail, I., Kurk, J., Cirasuolo, M., Casali, M., Ivison, R.J., Coppin, K., Dalton, G.B., 2009, MNRAS, 398, L68-L72. Postscript version, PDF version, Abstract.

2)  ``HiZELS: A High Redshift Survey of H-alpha Emitters. II: The Nature of Star-Forming Galaxies at z=0.84'', Sobral, D., Best, P.N., Geach, J.E., Smail, I., Kurk, J., Cirasuolo, M., Casali, M., Ivison, R.J., Coppin, K., Dalton, G.B., 2009, MNRAS, 398, 75-90. Postscript version, PDF version, Abstract.

1)  ``HiZELS: A High Redshift Survey of H-alpha Emitters. I: The Cosmic Star Formation Rate and Clustering at z=2.23'', Geach, J.E., Smail, I., Best, P., Kurk, J., Casali, M., Ivison, R.J., Coppin, K., 2008, MNRAS, 388, 1473-1486. Postscript version, PDF version, Abstract.