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

Pacucci, Fabio and Pallottini, Andrea and Ferrara, Andrea and Gallerani, Simona (2017) The nature of the Lyman α emitter CR7: a persisting puzzle. Monthly Notices of the Royal Astronomical Society: Letters, 468 (1). L77-L81. ISSN 1745-3925. doi:10.1093/mnrasl/slx029.

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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.

Item Type:Article
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URLURL TypeDescription Paper
Pacucci, Fabio0000-0001-9879-7780
Ferrara, Andrea0000-0002-9400-7312
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.
Group:SPLASH, COSMOS, Infrared Processing and Analysis Center (IPAC)
Issue or Number:1
Record Number:CaltechAUTHORS:20170626-150842064
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78576
Deposited By: Joy Painter
Deposited On:27 Jun 2017 20:15
Last Modified:15 Nov 2021 17:41

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