HiZELS:a high-redshift survey of Hα emitters - II. the nature of star-forming galaxies at z = 0.84

By D. Sobral, P. Best, James E. Geach, I. Smail, J. Kurk, M. Cirasuolo, M. Casali, R. Ivison, K. Coppin, G. B. D. I. Edinburgh and 5 more. 2009

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New results from a large survey of Hα emission-line galaxies at z = 0.84 using the Wide Field Camera on the United Kingdom Infrared Telescope and a custom narrow-band filter in the J band are presented as part of the High-z Emission Line Survey (HiZELS). The deep narrow-band images reach an effective flux limit of F Hα ∼ 10 -16 erg s -1 cm -2 in a comoving volume of 1.8 × 10 5 Mpc 3, resulting in the largest and deepest survey of its kind ever done at z ∼ 1. There are 1517 potential line emitters detected across ∼1.4 deg 2, of which 743 are selected as Hα emitters, based on their photometric and spectroscopic redshifts. These are then used to calculate the Hα luminosity function, which is well fitted by a Schechter function with L* = 10 42.26±0.05 erg s -1, φ* = 10 -1.92±0.10 Mpc -3 and α = -1.65 ± 0.15, and are used to estimate the volume average star formation rate (SFR) at z = 0.845, ρ SFR: 0.15 ± 0.01 M ⊙ yr -1 Mpc -3 (corrected for 15 per cent active galactic nucleus contamination and integrated down to 2.5 M ⊙ yr -1). These results robustly confirm a strong evolution of ρ SFR from the present day out to z ∼ 1 and then flattening to z ∼ 2 using a single star formation indicator: Hα luminosity. Out to z ∼ 1, both the characteristic luminosity and space density of the Hα emitters increase significantly; at higher redshifts, L* continues to increase, but φ* decreases. The z = 0.84 Hα emitters are mostly disc galaxies (82 ± 3 per cent), while 28 ± 4 per cent of the sample shows signs of merger activity; mergers account for ∼20 per cent of the total integrated ρ SFR at this redshift. Irregulars and mergers dominate the Hα luminosity function above L*, while discs are dominant at fainter luminosities. These results demonstrate that it is the evolution of 'normal' disc galaxies that drives the strong increase in the SFR density from the current epoch to z ∼ 1, although the continued strong evolution of L* beyond z = 1 suggests an increasing importance of merger activity at higher redshifts. © 2009 RAS.

Subfields: Astronomy and Astrophysics, Instrumentation

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LARGE AREA SURVEY FOR z = 7 GALAXIES IN SDF AND GOODS-N: IMPLICATIONS FOR GALAXY FORMATION AND COSMIC REIONIZATION (2009, unknown): “2008, 2009a,b; Oesch et al. 2009a,b; Castellano et al. 2009; McLure et al. 2009a,b; Bunker et al. 2009; Hickey et al. 2009; Henry et al. 2007, 2008, 2009; Bradley et al. 2008; Zheng et al. 2009; Sobral et al. 2009).”
A large Hα survey at z = 2.23, 1.47, 0.84 and 0.40: the 11 Gyr evolution of star-forming galaxies from HiZELS (2012, methodology): “HiZELS, the High-redshift(Z) Emission Line Survey2 (Geach et al. 2008; Sobral et al. 2009, 2012, hereafter S09 and S12) is a Campaign Project using the Wide Field CAMera (WFCAM) on the United Kingdom Infra-Red Telescope (UKIRT) and exploits specially-designed narrow-band filters in the J and H…”
The dependence of star formation activity on environment and stellar mass at z∼ 1 from the HiZELS-Hα survey (2010, background): “This has led to significant progress (e.g. Ly et al. 2007; Shioya et al. 2008; Geach et al. 2008; Sobral et al. 2009a; Garn et al. 2010; Sobral et al. 2010) taking advantage of large samples of typically hundreds of Hα emitters up to z = 2.23.”
On the evolution and environmental dependence of the star formation rate versus stellar mass relation since z ∼ 2 (2013, methodology): “The HiZELS Hα emitter samples are selected from the UDS and COSMOS fields (total∼2 deg2; see also Geach et al. 2008; 2012; Sobral et al. 2009; 2012; 2013) by widefield narrow-band imaging observations with NB921 on Subaru (z = 0.4), NBJ on UKIRT (z = 0.8), and the NBK /H2 filters on UKIRT/VLT (z =…”
Cosmic evolution of submillimeter galaxies and their contribution to stellar mass assembly (2009, unknown): “…Hα Hippelein et al. (2003) 0.100 0.100 0.0192 0.0042 0.0014 Hα Brinchmann et al. (2004) 0.010 0.010 0.0158 0.0033 0.0071 Hα Hanish et al. (2006) 0.840 0.030 0.1500 0.0200 0.0200 Hα Sobral et al. (2009) 2.230 0.150 0.1700 0.0900 0.1600 Hα Geach et al. (2008) 0.242 0.009 0.0180 0.0040 0.0070 Hα…”
Star formation at z=1.47 from HiZELS: an Hα+[O ii] double-blind study* (2011, methodology): “One of the potential NBH emitters flagged as a star is likely to be a cool T-dwarf (see Sobral et al. 2009a).”
STATISTICS OF 207 Lyα EMITTERS AT A REDSHIFT NEAR 7: CONSTRAINTS ON REIONIZATION AND GALAXY FORMATION MODELS (2010, background): “Moreover, beyond this epoch, only weak upper limits are placed on Lyα LF at z ≃ 8.8 (Willis & Courbin 2005; Cuby et al. 2007; Willis et al. 2008; Sobral et al. 2009; cf. Stark et al. 2007).”
ON THE STELLAR POPULATIONS AND EVOLUTION OF STAR-FORMING GALAXIES AT 6.3 < z ⩽ 8.6 (2009, background): “…observatories, but by choosing to search for Lyα emission at redshifts between strong atmospheric emission lines, a number of studies are underway which are expected to yield important results (e.g., Nilsson et al. 2007a; Hibon et al. 2009; Sobral et al. 2009, Tilvi et al. 2009 in prep).”
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 disc galaxies. (2012, unknown): “…panoramic (degree-scale) imaging with near-infrared narrow-band filters, to carry out the High-Z Emission Line Survey (HiZELS), targeting Hα emitting galaxies in four precise (δz = 0.03) redshift slices: z = 0.40, 0.84, 1.47 and 2.23 (Geach et al. 2008; Sobral et al. 2009, 2010, 2011, 2012a,b).”
On the origin of the galaxy star‐formation‐rate sequence: evolution and scatter (2009, background): “A number of studies have shown that the decline in the comoving cosmic SFR density from z 1 to the present is not due to a decline in the major merger rate (Bell et al. 2005; Melbourne, Koo & Le Floc’h 2005; Wolf et al. 2005; Lotz et al. 2008; Sobral et al. 2009).”