AM-1 - A very distant globular cluster

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Journal titleThe Astrophysical Journal
Pages221228; # of pages: 8
Subjectabundance; globular clusters; stellar spectrophotometry; color-magnitude diagram; halos; hertzsprung-Russell diagram; horizontal branch stars; stellar color; stellar luminosity; stellar magnitude
AbstractDeep B and V frames have been obtained for Arp-Madore 1 (AM-1) using the Cerro Tololo 4 m telescope and prime focus CCD camera, confirming the nature of this object as a globular cluster. In particular, the resulting color-magnitude diagram shows a sharply defined red horizontal branch at apparent magnitude m(V) = 20.93 + or - 0.04. Adopting M(V)(HB) = 0.6 then yields a galactocentric distance of 118 kpc, an amount placing AM-1 as the most distant globular cluster yet identified which may still be associated with the Galaxy. From the color of the giant branch at the horizontal branch, Fe/H is estimated as -1.8 + or - 0.3, a value which lends support to previous arguments that the abundance gradient in the outer halo is weak. In stellar content AM-1 appears similar to the other low-luminosity members of the outer halo - the Palomar clusters and dwarf spheroidals.
Publication date
AffiliationNational Research Council Canada
Peer reviewedYes
NRC number23233
NPARC number21273617
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Record identifieree2e255f-90e1-4ff7-83d1-5acd5439c217
Record created2015-01-16
Record modified2016-05-09
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