A Low‐Latitude Halo Stream around the Milky Way

Yanny, B.; Newberg, Heidi Jo; Grebel, Eva K.; Kent, S.; Odenkirchen, M.; Rockosi, C. M.; Schlegel, David J.; SubbaRao, Mark; Brinkmann, J.; Fukugita, M.; Ivezić, Željko; Lamb, D. Q.; Schneider, Donald P.; York, Donald G.

doi:10.1086/374220

Cited by 414 publications

(468 citation statements)

References 45 publications

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“…The collection of stars now known as the 'Monoceros ring' has been interpreted as evidence for a warped disk 13 , or alternatively as the remnant of a dwarf galaxy cannibalized by the Milky Way 14 . It is perhaps curious that the Cepheids discussed above are at the distance from the Galactic centre that one would expect the Monoceros ring to be, if indeed it were a complete circular ring around the Galaxy.…”

Section: Cepheid Variables In the Flared Outer Disk Of Our Galaxymentioning

confidence: 99%

Cepheid variables in the flared outer disk of our galaxy

Feast

Menzies

Matsunaga

et al. 2014

Nature

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Flaring and warping of the disk of the Milky Way have been inferred from observations of atomic hydrogen 1,2 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 3 . With their wellcalibrated period-luminosity relationships, Cepheid stars are useful distance indicators 4 . 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 5 .

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Section: Cepheid Variables In the Flared Outer Disk Of Our Galaxymentioning

confidence: 99%

Cepheid variables in the flared outer disk of our galaxy

Feast

Menzies

Matsunaga

et al. 2014

Nature

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“…Ibata et al 2001), the Monoceros stream (e.g. Yanny et al 2003), the orphan stream (Belokurov et al 2006) and the anticenter stream (Grillmair 2006). The most prominent and the earliest discovered is the Magellanic stream A&A 511, A29 (2010) (Brüns et al 2005) that dynamical models suggest to be about 1.7 Gyr old (e.g.…”

Section: Introductionmentioning

confidence: 99%

Galaxy evolution in Local Group analogs

Marino

Bianchi

Rampazzo

et al. 2010

A&A

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Context. Understanding the astrophysical processes acting within galaxy groups and their effects on the evolution of the galaxy population is one of the crucial topics of modern cosmology, as almost 60% of galaxies in the Local Universe are found in groups. Aims. We aim at learning about galaxy evolution within nearby groups dominated by late-type galaxies, specifically by studying their ultraviolet-emitting stellar population. Methods. We imaged in the far (FUV, λ eff = 1539 Å) and near ultraviolet (NUV, λ eff = 2316 Å) with the Galaxy Evolution Explorer (GALEX) three nearby groups, namely LGG 93, LGG 127 and LGG 225. We obtained the UV galaxy surface photometry and, for LGG 225, the only group covered by the SDSS, the photometry in u, g, r, i, z bands. We discuss galaxy morphologies looking for interaction signatures and we analyze the spectral energy distribution of galaxies to infer their luminosity-weighted ages. The UV and optical photometry was also used to perform a luminosity-weighted kinematical and dynamical analysis of each group and to evaluate the stellar mass. Results. A few member galaxies in LGG 225 show a distorted UV morphology due to ongoing interactions. (FUV − NUV) colors suggest that spirals in LGG 93 and LGG 225 host stellar populations in their outskirts younger than that of M 31 and M 33 in the Local Group or with less extinction. The irregular interacting galaxy NGC 3447A has a significantly younger stellar population (a few Myr old) than the average of the other irregular galaxies in LGG 225 suggesting that the encounter triggered star formation. The early-type members of LGG 225, NGC 3457 and NGC 3522, have masses of the order of a few 10 9 M , comparable to the Local Group ellipticals. For the most massive spiral in LGG 225, we estimate a stellar mass of ≈4 × 10 10 M , comparable to M 33 in the Local Group. Ages of stellar populations range from a few to ≈7 Gyr for the galaxies in LGG 225. The kinematical and dynamical analysis indicates that LGG 127 and LGG 225 are in a pre-virial collapse phase, i.e. still undergoing dynamical relaxation, while LGG 93 is likely virialized. Both the photometric and the dynamical analyses suggest that LGG 225 is in a more active evolution phase than LGG 93 and LGG 127.

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“…Strong observational evidence in favor of at least some contribution of dSph systems to the halo was first provided by Ibata et al (1994) with the discovery that the Galaxy is currently capturing the Sagittarius (Sgr) system with its attendant globular clusters. More recent evidence (e.g., Yanny et al 2003;Martin et al 2004) indicates that the Galaxy may well be absorbing or has absorbed additional systems. In addition, the complicated history of gradual metal growth in !…”

Section: Introductionmentioning

confidence: 99%

"Sculptor-ing" the Galaxy? The Chemical Compositions of Red Giants in the Sculptor Dwarf Spheroidal Galaxy

et al. 2005

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We used high-resolution, high signal-to-noise ratio spectra obtained with the Very Large Telescope and the UVVisual Echelle Spectrograph to determine abundances of 17 elements in four red giants in the Sculptor (Scl ) dwarf spheroidal galaxy. Our ½Fe=H -values range from À2.10 to À0.97, confirming previous findings of a large metallicity spread. We combined our data with similar data for five Scl giants studied recently by Shetrone et al. to form one of the largest samples of high-resolution abundances yet obtained for a dwarf spheroidal galaxy, covering essentially the full known metallicity range in this galaxy. These properties allow us to establish trends of ½X=Fe with ½Fe=H for many elements X. The trends are significantly different from the trends seen in Galactic halo and globular cluster stars. This conclusion is evident for most of the elements from oxygen to manganese. We compare our Scl sample with the most similar Galactic counterparts and find substantial differences remain even with these stars. The many discrepancies in the relationships between ½X=Fe as seen in Scl compared with Galactic field stars indicate that our halo cannot be made up in bulk of stars similar to those presently seen in dwarf spheroidal galaxies like Scl, corroborating similar conclusions reached by Shetrone et al., Fulbright, and Tolstoy et al. These results have serious implications for the Searle-Zinn and hierarchical galaxy formation scenarios. We also find that the most metal-rich star in our sample is a heavy element-rich star. This star and the ½Ba=Eu trend we see indicate that asymptotic giant branch stars must have played an important role in the evolution of the s-process elements in Scl. A very high percentage of such heavy-element stars are now known in dwarf spheroidals compared with the halo, further mitigating against the formation of the halo from such objects.

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A Low‐Latitude Halo Stream around the Milky Way

Cited by 414 publications

References 45 publications

Cepheid variables in the flared outer disk of our galaxy

Cepheid variables in the flared outer disk of our galaxy

Galaxy evolution in Local Group analogs

"Sculptor-ing" the Galaxy? The Chemical Compositions of Red Giants in the Sculptor Dwarf Spheroidal Galaxy

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