Blue horizontal-branch stars in the Sagittarius dwarf spheroidal galaxy

Lorenzo Monaco, Michele Bellazzini, Francesco R. Ferraro, Elena Pancino

Resultado de la investigación: Article

31 Citas (Scopus)

Resumen

We report on the discovery of a blue horizontal-branch (BHB) population belonging to the Sagittarius dwarf spheroidal galaxy. The sequence is clearly identified in the (V, V-I) color-magnitude diagram obtained for about 500,000 stars in the region of the globular cluster M54. The BHB morphology is similar to the analogous sequence in M54, but it is unambiguously associated with Sgr since (1) it is detected well outside the main body of the cluster, up to more than five tidal radii from the cluster center and (2) the BHB stars follow the radial distribution of the other stellar populations of Sgr. This finding finally demonstrates that the Sgr galaxy hosts a significant (of the order of ∼10%) old and metal-poor stellar population ([Fe/H] ≲-1.3; age ≳ 10 Gyr), similar to that of its oldest clusters (M54, Ter 8). We also show that the Sgr BHB sequence found here is the counterpart of the analogous feature observed by Newberg et al. in the Sgr stream, in a field more than 80° away from the center of the galaxy.

Idioma originalEnglish
PublicaciónAstrophysical Journal
Volumen597
N.º1 II
DOI
EstadoPublished - 1 nov 2003

Huella dactilar

horizontal branch stars
blue stars
dwarf galaxies
diagram
metal
galaxies
color-magnitude diagram
globular clusters
radial distribution
stars
radii
metals
distribution

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Monaco, Lorenzo ; Bellazzini, Michele ; Ferraro, Francesco R. ; Pancino, Elena. / Blue horizontal-branch stars in the Sagittarius dwarf spheroidal galaxy. En: Astrophysical Journal. 2003 ; Vol. 597, N.º 1 II.
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abstract = "We report on the discovery of a blue horizontal-branch (BHB) population belonging to the Sagittarius dwarf spheroidal galaxy. The sequence is clearly identified in the (V, V-I) color-magnitude diagram obtained for about 500,000 stars in the region of the globular cluster M54. The BHB morphology is similar to the analogous sequence in M54, but it is unambiguously associated with Sgr since (1) it is detected well outside the main body of the cluster, up to more than five tidal radii from the cluster center and (2) the BHB stars follow the radial distribution of the other stellar populations of Sgr. This finding finally demonstrates that the Sgr galaxy hosts a significant (of the order of ∼10{\%}) old and metal-poor stellar population ([Fe/H] ≲-1.3; age ≳ 10 Gyr), similar to that of its oldest clusters (M54, Ter 8). We also show that the Sgr BHB sequence found here is the counterpart of the analogous feature observed by Newberg et al. in the Sgr stream, in a field more than 80° away from the center of the galaxy.",
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Blue horizontal-branch stars in the Sagittarius dwarf spheroidal galaxy. / Monaco, Lorenzo; Bellazzini, Michele; Ferraro, Francesco R.; Pancino, Elena.

En: Astrophysical Journal, Vol. 597, N.º 1 II, 01.11.2003.

Resultado de la investigación: Article

TY - JOUR

T1 - Blue horizontal-branch stars in the Sagittarius dwarf spheroidal galaxy

AU - Monaco, Lorenzo

AU - Bellazzini, Michele

AU - Ferraro, Francesco R.

AU - Pancino, Elena

PY - 2003/11/1

Y1 - 2003/11/1

N2 - We report on the discovery of a blue horizontal-branch (BHB) population belonging to the Sagittarius dwarf spheroidal galaxy. The sequence is clearly identified in the (V, V-I) color-magnitude diagram obtained for about 500,000 stars in the region of the globular cluster M54. The BHB morphology is similar to the analogous sequence in M54, but it is unambiguously associated with Sgr since (1) it is detected well outside the main body of the cluster, up to more than five tidal radii from the cluster center and (2) the BHB stars follow the radial distribution of the other stellar populations of Sgr. This finding finally demonstrates that the Sgr galaxy hosts a significant (of the order of ∼10%) old and metal-poor stellar population ([Fe/H] ≲-1.3; age ≳ 10 Gyr), similar to that of its oldest clusters (M54, Ter 8). We also show that the Sgr BHB sequence found here is the counterpart of the analogous feature observed by Newberg et al. in the Sgr stream, in a field more than 80° away from the center of the galaxy.

AB - We report on the discovery of a blue horizontal-branch (BHB) population belonging to the Sagittarius dwarf spheroidal galaxy. The sequence is clearly identified in the (V, V-I) color-magnitude diagram obtained for about 500,000 stars in the region of the globular cluster M54. The BHB morphology is similar to the analogous sequence in M54, but it is unambiguously associated with Sgr since (1) it is detected well outside the main body of the cluster, up to more than five tidal radii from the cluster center and (2) the BHB stars follow the radial distribution of the other stellar populations of Sgr. This finding finally demonstrates that the Sgr galaxy hosts a significant (of the order of ∼10%) old and metal-poor stellar population ([Fe/H] ≲-1.3; age ≳ 10 Gyr), similar to that of its oldest clusters (M54, Ter 8). We also show that the Sgr BHB sequence found here is the counterpart of the analogous feature observed by Newberg et al. in the Sgr stream, in a field more than 80° away from the center of the galaxy.

KW - Branch

KW - Galaxies: Individual (Sagittarius)

KW - Globular clusters: Individual (M54)

KW - Stars: Horizontal

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