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Most stars (and planets?) are born in intense radiation fields

Lee, Eve J. and Hopkins, Philip F. (2020) Most stars (and planets?) are born in intense radiation fields. Monthly Notices of the Royal Astronomical Society: Letters, 495 (1). L86-L91. ISSN 1745-3925. doi:10.1093/mnrasl/slaa050.

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Protostars and young stars are strongly spatially ‘clustered’ or ‘correlated’ within their natal giant molecular clouds. We demonstrate that such clustering leads to the conclusion that the incident bolometric radiative flux upon a random young star/disc is enhanced (relative to volume-averaged fluxes) by a factor that increases with the total stellar mass of the complex. Because the Galactic cloud mass function is top-heavy, the typical star in our Galaxy experienced a much stronger radiative environment than those forming in well-observed nearby (but relatively small) clouds, exceeding fluxes in the Orion Nebular Cluster by factors of ≳30. Heating of the circumstellar disc around a median young star is dominated by this external radiation beyond ∼50 au. And if discs are not well shielded by ambient dust, external ultraviolet irradiation can dominate over the host star down to sub-au scales. Another consequence of stellar clustering is an extremely broad Galaxy-wide distribution of incident flux (spanning >10 decades), with half the Galactic star formation in a substantial ‘tail’ towards even more intense background radiation. We also show that the strength of external irradiation is amplified superlinearly in high-density environments such as the Galactic Centre, starbursts, or high-redshift galaxies.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lee, Eve J.0000-0002-1228-9820
Hopkins, Philip F.0000-0003-3729-1684
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 March 5. Received 2020 March 3; in original form 2020 January 31. We thank Ruobing Dong and Stella Offner for useful feedback, Andrew Winter for interesting discussions, and the anonymous referee for their encouraging report. EJL was supported by the Sherman Fairchild Fellowship at Caltech. Support for PFH was provided by NSF Collaborative Research Grants 1715847 and 1911233, NSF CAREER grant 1455342, and NASA grants 80NSSC18K0562 and JPL 1589742.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
Subject Keywords:accretion, accretion discs, hydrodynamics, planets and satellites: formation, protoplanetary discs, stars: formation, stars: protostars
Issue or Number:1
Record Number:CaltechAUTHORS:20200625-112849542
Persistent URL:
Official Citation:Eve J Lee, Philip F Hopkins, Most stars (and planets?) are born in intense radiation fields, Monthly Notices of the Royal Astronomical Society: Letters, Volume 495, Issue 1, June 2020, Pages L86–L91,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104046
Deposited By: George Porter
Deposited On:26 Jun 2020 14:22
Last Modified:16 Nov 2021 18:27

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