A NOVEL APPROACH TO CONSTRAIN THE MASS RATIO OF MINOR MERGERS IN ELLIPTICAL GALAXIES: APPLICATION TO NGC 4889, THE BRIGHTEST CLUSTER GALAXY IN COMA

Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space...

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Bibliographic Details
Published in:The Astrophysical journal 2013-08, Vol.773 (1), p.1-11
Main Authors: Gu, Meng, Ho, Luis C, Peng, Chien Y, Huang, Song
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BRIGHTNESS
COLOR
Coma
Construction
DECOMPOSITION
Elliptical galaxies
EVOLUTION
GALAXIES
GALAXY CLUSTERS
Galaxy mergers & collisions
Hubble Space Telescope
INTERACTIONS
LUMINOSITY
MASS
PHOTOMETRY
Progenitors (astrophysics)
SATELLITES
SPACE
STARS
SURFACES
TELESCOPES
TWO-DIMENSIONAL CALCULATIONS
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Summary:Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (M sub(I) approximately -18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of ~90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/773/1/34