Currently there exist a variety of scalar field models that attempt to explain the late‐time acceleration of the Universe. This includes the standard canonical and non‐canonical scalar field models together with the recently proposed Galileon scalar field models. One can divide all these scalar field models into two broad categories, namely thawing and tracker classes. In this work we investigate the evidence for these models from presently available observational data using the Bayesian approach. We use the generalized Chaplygin gas (GCG) parametrization for the dark energy equation of state (EoS), as it exhibits both thawer‐ and tracker‐like behaviour for different values of the parameters. Subsequently we use Type Ia supernova (SnIa) measurements, recent measurements of the Hubble parameter at different redshifts (H(z)), measurements of the look‐back time at different redshifts (Lookback), measurements of the linear growth factor in large‐scale structure (GR) from various redshift surveys and finally measurement of the anisotropies in the cosmic microwave background radiation by WMAP‐7 observations. The analysis of data from SN+H(z)+Lookback does not favour either tracker or thawer classes. Inclusion of data from GR+WMAP‐7 favours the thawer class of models if one assumes the dark energy to be a smooth component. If we consider dark energy perturbations, however, both tracker and thawer types of models are equally favoured by the data.

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We investigate the prospect of constraining scalar field dark energy models using HI 21-cm intensity mapping surveys. We consider a wide class of coupled scalar field dark energy models whose predictions about the background cosmological evolution are different from the ΛCDM predictions by a few percent. We find that these models can be statistically distinguished from ΛCDM through their imprint on the 21-cm angular power spectrum. At the fiducial z = 1.5, corresponding to a radio interferometric observation of the post-reionization HI 21 cm observation at frequency 568MHz, these models can infact be distinguished from the ΛCDM model at SNR > 3σ level using a 10,000 hr radio observation distributed over 40 pointings of a SKA1-mid like radio-telescope. We also show that tracker models are more likely to be ruled out in comparison with ΛCDM than the thawer models. Future radio observations can be instrumental in obtaining tighter constraints on the parameter space of dark energy models and supplement the bounds obtained from background studies.

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