Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published February 20, 2017 | public
Journal Article

The nature of the Lyman α emitter CR7: a persisting puzzle

Abstract

The peculiar emission properties of the z ∼ 6.6 Lyα emitter COSMOS redshift 7 (CR7) have been initially interpreted with the presence of either a direct collapse black hole (DCBH) or a substantial mass of Pop III stars. Instead, updated photometric observations by Bowler et al. seem to suggest that CR7 is a more standard system. Here, we confirm that the original DCBH hypothesis is consistent also with the new data. Using radiation-hydrodynamic simulations, we reproduce the new infrared photometry with two models involving a Compton-thick DCBH of mass ≈7 × 106 M⊙ accreting (a) metal-free (Z = 0) gas with column density NH = 8 × 1025 cm−2 or (b) low-metallicity gas (Z = 5 × 10−3 Z⊙) with NH = 3 × 1024 cm−2. The best-fitting model reproduces the photometric data to within 1σ. Such metals can be produced by weak star-forming activity occurring after the formation of the DCBH. The main contribution to the Spitzer/IRAC 3.6 μm photometric band in both models is due to He I/He II λλ4714, 4687 emission lines, while the contribution of [O III] λλ4959, 5007 emission lines, if present, is sub-dominant. Spectroscopic observations with JWST will be required to ultimately clarify the nature of CR7.

Additional Information

© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We thank Rebecca Bowler and Eli Visbal for their valuable comments. FP acknowledges the ADAP grant No. MA160009.

Additional details

Created:
August 19, 2023
Modified:
October 26, 2023