Observing supermassive dark stars with James Webb Space Telescope

We study the capability of theJames Webb Space Telescope (JWST) to detect supermassive dark stars (SMDSs). If the first stars are powered by dark matter (DM) heating in triaxial DM haloes, they may grow to be very large (>106 M-circle dot) and very bright (>109 L circle dot). These SMDSs would be visible in deep imaging with JWST and even Hubble Space Telescope (HST). We use sensitivity limits from previous HST surveys to place bounds on the numbers of SMDSs that may be detected in future JWST imaging surveys. We showed that SMDS in the mass range 106-107 M circle dot are bright enough to be detected in all the wavelength bands of the NIRCam on JWST (but not in the less sensitive MIRI camera at higher wavelengths). If SMDSs exist at z similar to 10, 12 and 14, they will be detectable as J-, H- or K-band dropouts, respectively. With a total survey area of 150 arcmin2 (assuming a multiyear deep parallel survey with JWST), we find that typically the number of 106 M circle dot SMDSs found as H- or K-band dropouts is similar to 105fSMDS, where the fraction of early DM haloes hosting DS is likely to be small, fSMDS << 1. If the SMDS survive down to z= 10 where HST bounds apply, then the observable number of SMDSs as H- or K-band dropouts with JWST is similar to 130. While individual SMDS are bright enough to be detected by JWST, standard Population III stars (without DM annihilation) are not, and would only be detected in first galaxies with total stellar masses of 106108 M circle dot. Differentiating first galaxies at z > 10 from SMDSs would be possible with spectroscopy: the SMDS (which are too cool produce significant nebular emission) will have only absorption lines, while the galaxies are likely to produce emission lines as well. Of particular interest would be the He ii emission lines at m as well as Ha lines which would be signatures of early galaxies rather than SMDSs. The detection of SMDSs with JWST would not only provide alternative evidence for weakly interacting massive particles, but also provide a possible pathway for the formation of massive (104106 M circle dot) seeds for the formation of supermassive black holes that power quasi-stellar objects at z= 6.