Tidal dwarf galaxies at intermediate redshifts |
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Authors: | Zhang-Zheng Wen Xian-Zhong Zheng Ying-He Zhao Yu Gao |
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Institution: | (1) Universitäts-Sternwarte, Geismarlandstraße 11, 37083 Göttingen, Germany;(2) Centre d'Etudes de Saclay, CNRS URA 2052 and CEA, DSM, DAPNIA, Service d'Astrophysique, 91191 Gif-sur-Yvette Cedex, France |
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Abstract: | We present the first attempt at measuring the production rate of tidal dwarf galaxies (TDGs) and estimating their contribution
to the overall dwarf population. Using HST/ACS deep imaging data from GOODS and GEMS surveys in conjunction with photometric
redshifts from COMBO-17 survey, we performed a morphological analysis for a sample of merging/interacting galaxies in the
Extended Chandra Deep Field South and identified tidal dwarf candidates in the rest-frame optical bands. We estimated a production
rate about 1.4×10−5 per Gyr per comoving volume for long-lived TDGs with stellar mass 3×108−9 M⊙ at 0.5<z<1.1. Together with galaxy merger rates and TDG survival rate from the literature, our results suggest that only a marginal
fraction (less than 10%) of dwarf galaxies in the local universe could be tidally-originated. TDGs in our sample are on average
bluer than their host galaxies in the optical. Stellar population modelling of optical to near-infrared spectral energy distributions
(SEDs) for two TDGs favors a burst component with age 400/200 Myr and stellar mass 40%/26% of the total, indicating that a
young stellar population newly formed in TDGs. This is consistent with the episodic star formation histories found for nearby
TDGs. |
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