The Ages and Masses of a Million Galactic-disk Main-sequence Turnoff and Subgiant Stars from the LAMOST Galactic Spectroscopic Surveys

Xiang, Maosheng; Liu, Xiaowei; Shi, Jianrong; Yuan, Haibo; Huang, Yang; Chen, Bingqiu; Wang, Chun; Tian, Zhijia; Wu, Yaqian; Yang, Y. G.; Zhang, Huawei; Huo, Zhi-Ying; Ren, Juanjuan

doi:10.3847/1538-4365/aa80e4

Cited by 83 publications

(109 citation statements)

References 96 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is an increased dominance of young stars in the outer disc at all |z| heights. This dominance of young stars in the outer Galaxy has been observed using APOGEE (Ness et al 2016) and LAMOST (Xiang et al 2017). It is likely related to the decreased relative contribution in the outer disc of the high-α sequence, which has been found to be generally older than the low-α sequence.…”

Section: Metallicity-age Relationmentioning

confidence: 60%

See 1 more Smart Citation

Spatial variations in the Milky Way disc metallicity–age relation

Feuillet

Frankel

Lind

et al. 2019

Monthly Notices of the Royal Astronomical Society

104

View full text Add to dashboard Cite

Stellar ages are a crucial component to studying the evolution of the Milky Way. Using Gaia DR2 distance estimates, it is now possible to estimate stellar ages for a larger volume of evolved stars through isochrone matching. This work presents [M/H]age and [α/M]-age relations derived for different spatial locations in the Milky Way disc. These relations are derived by hierarchically modelling the star formation history of stars within a given chemical abundance bin. For the first time, we directly observe that significant variation is apparent in the [M/H]-age relation as a function of both Galactocentric radius and distance from the disc mid-plane. The [M/H]-age relations support claims that radial migration has a significant effect in the plane of the disc. Using the [M/H] bin with the youngest mean age at each radial zone in the plane of the disc, the present-day metallicity gradient is measured to be −0.059 ± 0.010 dex kpc −1 , in agreement with Cepheids and young field stars. We find a vertically flared distribution of young stars in the outer disc, confirming predictions of models and previous observations. The mean age of the [M/H]-[α/M] distribution of the solar neighborhood suggests that the high-[M/H] stars are not an evolutionary extension of the low-α sequence. Our observational results are important constraints to Galactic simulations and models of chemical evolution.

show abstract

Section: Metallicity-age Relationmentioning

confidence: 60%

“…However, the change in the turnover feature with increasing |z|, could also be caused by a lack of young stars at high |z|. The 7 < R Gal < 9, 1 <|z|< 2 bin is dominated by the high-α sequence, which has been found to be uniformly old (see Figure 7 and Xiang et al 2017).…”

Section: Metallicity-age Relationmentioning

confidence: 95%

Spatial variations in the Milky Way disc metallicity–age relation

Feuillet

Frankel

Lind

et al. 2019

Monthly Notices of the Royal Astronomical Society

104

View full text Add to dashboard Cite

show abstract

“…It has also been suggested that the mismatch is also metallicity dependent (e.g. Xiang et al 2017a).…”

Section: Discussionmentioning

confidence: 99%

“…RAVE (Steinmetz et al 2006), SEGUE (Yanny et al 2009), LAMOST Zhao et al 2012), Gaia-ESO (Gilmore et al 2012), GALAH (De Silva et al 2015), APOGEE (Majewski et al 2017), and the Gaia Radial Velocity Spectrometer (Cropper et al 2018); as well as email: mxiang@mpia.de * Hubble fellow upcoming surveys such as SDSS-V (Kollmeier et al 2017), 4MOST (Feltzing et al 2018;de Jong et al 2019), and WEAVE (Dalton et al 2014). These spectroscopic surveys, combined with the astrometric and photometric information from the Gaia mission (Gaia Collaboration et al 2016Collaboration et al , 2018, make it possible for us to obtain precise and accurate information for millions of stars in phase space or orbit space, along with estimates of age, mass, metallicity, and abundances for many elements, providing unprecedented opportunities to unravel the assemblage and evolution history of our Galaxy (see e.g., Rix & Bovy 2013;Ting, Conroy & Goodman 2015;Xiang et al 2017aXiang et al , 2018Frankel et al 2018;Bland-Hawthorn et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Abundance Estimates for 16 Elements in 6 Million Stars from LAMOST DR5 Low-Resolution Spectra

Xiang¹,

Ting²,

Rix³

et al. 2019

ApJS

Self Cite

198

243

View full text Add to dashboard Cite

We present the determination of stellar parameters and individual elemental abundances for 6 million stars from ∼8 million low-resolution (R ∼ 1800) spectra from LAMOST DR5. This is based on a modeling approach that we dub T he Data-Driven P ayne (DD-P ayne), which inherits essential ingredients from both The Payne (Ting et al. 2019) and T he Cannon (Ness et al. 2015). It is a data-driven model that incorporates constraints from theoretical spectral models to ensure the derived abundance estimates are physically sensible. Stars in LAMOST DR5 that are in common with either GALAH DR2 or APOGEE DR14 are used to train a model that delivers stellar parameters (T eff , log g, V mic ) and abundances for 16 elements (C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, and Ba) when applied to LAMOST spectra. Cross-validation and repeat observations suggest that, for S/N pix ≥ 50, the typical internal abundance precision is 0.03-0.1 dex for the majority of these elements, with 0.2-0.3 dex for Cu and Ba, and the internal precision of T eff and log g is better than 30 K and 0.07 dex, respectively. Abundance systematics at the ∼0.1 dex level are present in these estimates, but are inherited from the high-resolution surveys' training labels. For some elements, GALAH provides more robust training labels, for others, APOGEE. We provide flags to guide the quality of the label determination and to identify binary/multiple stars in LAMOST DR5. The abundance catalogs are publicly accessible via http://dr5.lamost.org/doc/vac.

show abstract

“…This pattern is generally understood in terms of the existence of a chemical "thick disk" (Yoshii 1982;Gilmore & Reid 1983) that comprises largely old stars enhanced in the α elements, along with a younger chemical "thin disk" of roughly solar abundance (e.g. Chiappini et al 1997;Bensby et al 2003;Haywood et al 2013;Xiang et al 2017;Wu et al 2019).…”

mentioning

confidence: 99%

Milky Way analogues in MaNGA: multiparameter homogeneity and comparison to the Milky Way

Boardman

Zasowski

Seth

et al. 2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The Milky Way provides an ideal laboratory to test our understanding of galaxy evolution, owing to our ability to observe our Galaxy over fine scales. However, connecting the Galaxy to the wider galaxy population remains difficult, due to the challenges posed by our internal perspective and to the different observational techniques employed. Here, we present a sample of galaxies identified as Milky Way Analogs (MWAs) on the basis of their stellar masses and bulge-to-total ratios, observed as part of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. We analyse the galaxies in terms of their stellar kinematics and populations as well as their ionised gas contents. We find our sample to contain generally young stellar populations in their outskirts. However, we find a wide range of stellar ages in their central regions, and we detect central AGN-like or composite-like activity in roughly half of the sample galaxies, with the other half consisting of galaxies with central star-forming emission or emission consistent with old stars. We measure gradients in gas metallicity and stellar metallicity that are generally flatter in physical units than those measured for the Milky Way; however, we find far better agreement with the Milky Way when scaling gradients by galaxies' disc scale lengths. From this, we argue much of the discrepancy in metallicity gradients to be due to the relative compactness of the Milky Way, with differences in observing perspective also likely to be a factor.

show abstract

The Ages and Masses of a Million Galactic-disk Main-sequence Turnoff and Subgiant Stars from the LAMOST Galactic Spectroscopic Surveys

Cited by 83 publications

References 96 publications

Spatial variations in the Milky Way disc metallicity–age relation

Spatial variations in the Milky Way disc metallicity–age relation

Abundance Estimates for 16 Elements in 6 Million Stars from LAMOST DR5 Low-Resolution Spectra

Milky Way analogues in MaNGA: multiparameter homogeneity and comparison to the Milky Way

Contact Info

Product

Resources

About