2016 Fiscal Year Annual Research Report
Measuring the growth history of galaxy outskirts
| Project/Area Number |
15K17603
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Bundy Kevin.A 東京大学, カブリ数物連携宇宙研究機構, 特任助教 (20624141)
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| Project Period (FY) |
2015-04-01 – 2017-03-31
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| Keywords | Spectral fitting / Stellar Gradients / AGN winds / Feedback |
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| Outline of Annual Research Achievements |
The purpose of this project was to test the 2-phase formation scenario for elliptical galaxies which states that their central cores are formed early while their outskirts build up through the accretion of "foreign stars" with time. Using the FIREFLY code, we have begun spectral fitting in order to determine stellar population properties such as age, metallicity, and alpha abundance.
As previously reported, an important discovery was made regarding the internal properties of galaxies with suppressed star formation. While the colors indicated these galaxies were "red and dead," their Ha gas profiles showed a surprising range of active behavior, hosting ionizing gas outflows at a suprisingly high rate. These "red geysers" may be a critical reason why star formation remains suppressed in these systems at late times. The resulting paper was published in Nature.
Additionally, we returned to the primary analysis of the stellar populations and investigated their dependence on the local environment in which the galaxy lives. Three papers have now been submitted describing the nature of gradients and the relatively minor impact that environment seems to play in shaping them.
Finally a workshop was held at Kavli IPMU to deeply discuss and compare different approaches for measuring stellar properties from the observed spectra. This workshop was highly successful and will result in improved methods for both this project, future analyses of MaNGA data, and for this subfield in general.
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