The VMC survey - XIV. First results on the look-back time star formation rate tomography of the Small Magellanic Cloud

Journal
Date Issued
2015
Author(s)
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Kerber, Leandro
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Cioni, Maria-Rosa L.
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Piatti, Andrés E.
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Bekki, Kenji
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BRESSAN, Alessandro
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de Grijs, Richard
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Emerson, Jim P.
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Groenewegen, Martin A. T.
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Ivanov, Valentin D.
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Subramanian, Smitha
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Tatton, Benjamin L.
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van Loon, Jacco Th.
DOI
Description
We thank the Cambridge Astronomy Survey Unit (CASU) and the Wide Field Astronomy Unit (WFAU) in Edinburgh for providing calibrated data products under the support of the Science and Technology Facility Council (STFC) in the UK. RdG acknowledges partial research support from the National Natural Science Foundation of China (NSFC) through grant 11373010. This work was partially supported by the Argentinian institutions CONICET and Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT). PM acknowledges the support from the ERC Consolidator Grant funding scheme ( project STARKEY , G.A. no. 615604).
Abstract
We analyse deep images from the VISTA survey of the Magellanic Clouds in the YJ{K_s} filters, covering 14 deg2 (10 tiles), split into 120 subregions, and comprising the main body and Wing of the Small Magellanic Cloud (SMC). We apply a colour-magnitude diagram reconstruction method that returns their best-fitting star formation rate SFR(t), age-metallicity relation (AMR), distance and mean reddening, together with 68 per cent confidence intervals. The distance data can be approximated by a plane tilted in the East-West direction with a mean inclination of 39°, although deviations of up to ±3 kpc suggest a distorted and warped disc. After assigning to every observed star a probability of belonging to a given age-metallicity interval, we build high-resolution population maps. These dramatically reveal the flocculent nature of the young star-forming regions and the nearly smooth features traced by older stellar generations. They document the formation of the SMC Wing at ages <0.2 Gyr and the peak of star formation in the SMC Bar at ̃40 Myr. We clearly detect periods of enhanced star formation at 1.5 and 5 Gyr. The former is possibly related to a new feature found in the AMR, which suggests ingestion of metal-poor gas at ages slightly larger than 1 Gyr. The latter constitutes a major period of stellar mass formation. We confirm that the SFR(t) was moderately low at even older ages.
Volume
449
Issue
1
Start page
639
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.449..639R
Rights
open.access
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