http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
LSST: From Science Drivers to Reference Design and Anticipated Data Products
Ivezić,, x17d,eljko,Kahn, Steven M.,Tyson, J. Anthony,Abel, Bob,Acosta, Emily,Allsman, Robyn,Alonso, David,AlSayyad, Yusra,Anderson, Scott F.,Andrew, John,P. Angel, James Roger,Angeli, George Z American Astronomical Society 2019 The Astrophysical journal Vol.873 No.2
Lee, Young Sun,Beers, Timothy C.,An, Deokkeun,Ivezić,, x17d,eljko,Just, Andreas,Rockosi, Constance M.,Morrison, Heather L.,Johnson, Jennifer A.,Schö,nrich, Ralph,Bird, Jonathan,Yanny, Brian IOP Publishing 2011 The Astrophysical journal Vol.738 No.2
<P>We employ measurements of the [alpha/Fe] ratio derived from low-resolution (R similar to 2000) spectra of 17,277 G-type dwarfs from the SEGUE survey to separate them into likely thin-and thick-disk subsamples. Both subsamples exhibit strong gradients of orbital rotational velocity with metallicity, of opposite signs, -20 to -30 km s(-1) dex(-1) for the thin-disk and + 40 to + 50 km s(-1) dex(-1) for the thick-disk population. The rotational velocity is uncorrelated with Galactocentric distance for the thin-disk subsample and exhibits a small trend for the thick-disk subsample. The rotational velocity decreases with distance from the plane for both disk components, with similar slopes (-9.0 +/- 1.0 km s(-1) kpc(-1)). Thick-disk stars exhibit a strong trend of orbital eccentricity with metallicity (about -0.2 dex(-1)), while the eccentricity does not change with metallicity for the thin-disk subsample. The eccentricity is almost independent of Galactocentric radius for the thin-disk population, while a marginal gradient of the eccentricity with radius exists for the thick-disk population. Both subsamples possess similar positive gradients of eccentricity with distance from the Galactic plane. The shapes of the eccentricity distributions for the thin-and thick-disk populations are independent of distance from the plane, and include no significant numbers of stars with eccentricity above 0.6. Among several contemporary models of disk evolution that we consider, radial migration appears to have played an important role in the evolution of the thin-disk population, but possibly less so for the thick disk, relative to the gas-rich merger or disk heating scenarios. We emphasize that more physically realistic models and simulations need to be constructed in order to carry out the detailed quantitative comparisons that our new data enable.</P>
THE STELLAR METALLICITY DISTRIBUTION FUNCTION OF THE GALACTIC HALO FROM SDSS PHOTOMETRY
An, Deokkeun,Beers, Timothy C.,Johnson, Jennifer A.,Pinsonneault, Marc H.,Lee, Young Sun,Bovy, Jo,Ivezić,, x17d,eljko,Carollo, Daniela,Newby, Matthew IOP Publishing 2013 The Astrophysical journal Vol.763 No.1
<P>We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of several star clusters and validated by comparisons with medium-resolution spectroscopic values over a wide range of metal abundance. We estimate distances and metallicities for individual main-sequence stars in the multiply scanned SDSS Stripe 82, at heliocentric distances in the range 5-8 kpc and |b| > 35 degrees, and find that the in situ photometric metallicity distribution has a shape that matches that of the kinematically selected local halo stars from Ryan & Norris. We also examine independent kinematic information from proper-motion measurements for high Galactic latitude stars in our sample. We find that stars with retrograde rotation in the rest frame of the Galaxy are generally more metal poor than those exhibiting prograde rotation, which is consistent with earlier arguments by Carollo et al. that the halo system comprises at least two spatially overlapping components with differing metallicity, kinematics, and spatial distributions. The observed photometric metallicity distribution and that of Ryan & Norris can be described by a simple chemical evolution model by Hartwick (or by a single Gaussian distribution); however, the suggestive metallicity-kinematic correlation contradicts the basic assumption in this model that the Milky Way halo consists primarily of a single stellar population. When the observed metallicity distribution is deconvolved using two Gaussian components with peaks at [Fe/H] approximate to -1.7 and -2.3, the metal-poor component accounts for approximate to 20%-35% of the entire halo population in this distance range.</P>