| 1. |
- Fantin, Nicholas J., et al.
(författare)
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The Canada-France Imaging Survey : Reconstructing the Milky Way Star Formation History from Its White Dwarf Population
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 887:2
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Tidskriftsartikel (refereegranskat)abstract
- As the remnants of stars with initial masses less than or similar to 8M(circle dot), white dwarfs contain valuable information on the formation histories of stellar populations. In this paper, we use deep, high-quality, u-band photometry from the Canada-France Imaging Survey, griz photometry from Pan-STARRS1, as well as proper motions from Gaia DR2, to select 25,156 white dwarf candidates over similar to 4500 deg(2) using a reduced proper motion diagram. We develop a new white dwarf population synthesis code that returns mock observations of the Galactic field white dwarf population for a given star formation history, while simultaneously taking into account the geometry of the Milky Way (MW), survey parameters, and selection effects. We use this model to derive the star formation histories of the thin disk, thick disk, and stellar halo. Our results show that the MW disk began forming stars (11.3 +/- 0.5) Gyr ago, with a peak rate of (8.8 +/- 1.4) M-circle dot yr(-1) at (9.8 +/- 0.4) Gyr, before a slow decline to a constant rate until the present day-consistent with recent results suggesting a merging event with a satellite galaxy. Studying the residuals between the data and best-fit model shows evidence for a slight increase in star formation over the past 3 Gyr. We fit the local fraction of helium-atmosphere white dwarfs to be (21 +/- 3)%. Incorporating this methodology with data from future wide-field surveys such as the Large Synoptic Survey Telescope, Euclid, The Cosmological Advanced Survey Telescope for Optical and ultraviolet Research, and the Wide Field Infrared Survey Telescope should provide an unprecedented view into the formation of the MW at its earliest epoch through its white dwarfs.
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| 2. |
- Thomas, Guillaume F., et al.
(författare)
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The Hidden Past of M92 : Detection and Characterization of a Newly Formed 17 degrees Long Stellar Stream Using the Canada-France Imaging Survey
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 902:2
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Tidskriftsartikel (refereegranskat)abstract
- We present an analysis of the structure, kinematics, and orbit of a newly found stellar stream emanating from the globular cluster M92 (NGC 6341). This stream was discovered in an improved matched-filter map of the outer Galaxy, based on a color-color-magnitude diagram, created using photometry from the Canada-France Imaging Survey and the Pan-STARRS 1 3 pi survey. We find the stream to have a length of 17 degrees (2.5 kpc at the distance of M92), a width dispersion of 029(42 pc), and a stellar mass of [3.17 0.89] x 10(4)M(10% of the stellar mass of the current main body of M92). We examine the kinematics of main-sequence, red giant, and blue horizontal branch stars belonging to the stream and that have proper motion measurements from the second data release of Gaia.N-body simulations suggest that the stream was likely formed very recently (during the last similar to 500 Myr) forcing us to question the orbital origin of this ancient, metal-poor globular cluster.
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