Cepheid variables in the flared outer disk of our galaxy

By M. Feast, J. Menzies, N. Matsunaga, P. Whitelock. 2014

60 citations recorded by the source corpus.

Flaring and warping of the disk of the Milky Way have been inferred from observations of atomic hydrogen but stars associated with flaring have not hitherto been reported. In the area beyond the Galactic centre the stars are largely hidden from view by dust, and the kinematic distances of the gas cannot be estimated. Thirty-two possible Cepheid stars (young pulsating variable stars) in the direction of the Galactic bulge were recently identified. With their well-calibrated period–luminosity relationships, Cepheid stars are useful distance indicators. When observations of these stars are made in two colours, so that their distance and reddening can be determined simultaneously, the problems of dust obscuration are minimized. Here we report that five of the candidates are classical Cepheid stars. These five stars are distributed from approximately one to two kiloparsecs above and below the plane of the Galaxy, at radial distances of about 13 to 22 kiloparsecs from the centre. The presence of these relatively young (less than 130 million years old) stars so far from the Galactic plane is puzzling, unless they are in the flared outer disk. If so, they may be associated with the outer molecular arm.

Subfields: Astronomy and Astrophysics, Instrumentation

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In Astronomy and Astrophysics

1. I. Minchev
2. Jo Bovy
3. Hans-Walter Rix
4. M. Martig
5. C. Chiappini
6. S. Majewski
7. David W. Hogg
8. J. Holtzman

In Instrumentation

1. I. Minchev
2. M. Martig
3. C. Chiappini
4. Jo Bovy
5. Hans-Walter Rix
6. S. Majewski
7. David W. Hogg
8. D. Nidever

Citations in the corpus

• Yule-Simpson’s paradox in Galactic Archaeology (2019, background): “Flaring in Milky Way stellar populations of limited age range has been found by Kalberla et al. (2014) (Red Clump), Feast et al. (2014) (Cepheids), Carraro et al. (2015) (young clusters) and in LAMOST (Wan et al. 2017; Wang et al. 2018; Xiang et al. 2018) and APOGEE (Mackereth et al. 2017) mono-age…”
• The vertical metallicity gradients of mono-age stellar populations in the Milky Way with the RAVE and Gaia data (2017, background): “Flaring star-forming regions have been observed previously in the Milky Way in the distribution of the HI and molecular gas (e.g. Scoville et al. 1993; Nakanishi & Sofue 2016), and young stellar populations traced by Cepheids (Feast et al. 2014).”
• DOES THE STELLAR DISTRIBUTION FLARE? A COMPARISON OF STELLAR SCALE HEIGHTS WITH LAB H i DATA (2014, methodology): “A similar ansatz was implicitly used by Feast et al. (2014) to prepare their Figure 1.”
• The age–metallicity structure of the Milky Way disc using APOGEE (2017, background): “A flare in the gas disk of the Milky Way, associated with the stellar component, is also observed in numerous studies (e.g. Feast et al. 2014; Kalberla et al. 2014; Lozinskaya & Karadashev 1963), suggesting a formation of the disk with structural parameters similar to its progenitor gas disk.”
• The Lives of Stars: Insights from the TGAS–RAVE–LAMOST Data Set (2018, background): “Evidence of formation mechanisms can be seen indirectly in the form of the Galactic warp (Djorgovski & Sosin 1989, Schönrich & Dehnen 2017) and flare (Kent et al. 1991, Feast et al. 2014), which could be caused either by accretion or by internal disk instabilities.”
• Mapping the Milky Way with LAMOST– III. Complicated spatial structure in the outer disc (2018, result): “…disc truncates at around 14– 15 kpc (Reylé et al. 2009; Minniti et al. 2011), but is consistent with Carraro et al. (2010, 2017), Carraro (2015), and Feast et al. (2014) that the disc may extend to larger radius than ∼ 20 kpc. Fitting with a radial exponential profile, Paper I obtained that the…”
• The influence of Sagittarius and the Large Magellanic Cloud on the stellar disc of the Milky Way Galaxy (2017, background): “Finally, in the direction of the Galactic Centre (l ∼ 0◦), Feast et al. (2014) have identified Cepheids at R ∼ 15–22 kpc which lie above and below the mid-plane at absolute heights of |Z| ∼ 2 kpc suggesting that they could be part of the flared disc, or possibly, as we shall see, a result of…”