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The Unusual and Ubiquitous Population of Hα Emitters at z ∼ 4: Where are all the Mergers?

Shim, Hyunjin and Chary, Ranga-Ram and Dickinson, Mark and Lin, Lihwai and Spinrad, Hyron and Stern, Daniel and Yan, Chu-Hung (2013) The Unusual and Ubiquitous Population of Hα Emitters at z ∼ 4: Where are all the Mergers? In: Galaxy Mergers In An Evolving Universe. Astronomical Society of the Pacific Conference Series. No.477. Astronomical Society of the Pacific , San Francisco, CA, pp. 185-188. ISBN 9781583818381.

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We present the evidence that strong Hα emitters (HAEs) comprise more than 70 % of galaxies with spectroscopic redshifts of 3.8 < z < 5.0, from the clear flux excess observed in the Spitzer/IRAC 3.6-μm band. HAEs are strongly star-forming galaxies with star formation rate of 20–500 M☉yr^(–1), with unusually large Hα equivalent widths (EW) of > 350 Å. The rest-frame UV to optical morphologies for half of the HAEs do not show any signs of mergers or tidal interactions. The large Hα EW of HAEs despite their relatively old stellar population age suggests that HAEs are producing stars continuously at a constant rate, rather than through multiple bursts invoked by major mergers. The observed number density of HAEs is consistent with the predicted number of halos which have gas infall rate comparable to the observed star formation rate. Therefore, HAEs provide indirect evidence supporting that star formation mechanism other than mergers, such as cold gas accretion, is the dominant driver of star formation at z ∼ 4.

Item Type:Book Section
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URLURL TypeDescription
Chary, Ranga-Ram0000-0001-7583-0621
Dickinson, Mark0000-0001-5414-5131
Lin, Lihwai0000-0001-7218-7407
Stern, Daniel0000-0003-2686-9241
Additional Information:© 2013 Astronomical Society of the Pacific.
Group:Infrared Processing and Analysis Center (IPAC)
Series Name:Astronomical Society of the Pacific Conference Series
Issue or Number:477
Record Number:CaltechAUTHORS:20131204-135828690
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42833
Deposited By: Tony Diaz
Deposited On:11 Dec 2013 00:09
Last Modified:09 Mar 2020 13:19

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