CLUSTER 77 IN NGC 4449: THE NUCLEUS OF A SATELLITE GALAXY BEING TRANSFORMED INTO A GLOBULAR CLUSTER?

Journal Article · Fri Jan 20 04:00:00 EST 2012 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/745/1/L1· OSTI ID:22047230

Annibali, F; Tosi, M ^[1]; Aloisi, A; Van der Marel, R P ^[2]; Martinez-Delgado, D ^[3]

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1. INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
3. Max-Planck-Institut fuer Astronomie, Konigstuhl, 17 D-69117 Heidelberg (Germany)

We report the discovery in our Hubble Space Telescope Advanced Camera for Surveys B, V, and I images of NGC 4449 of a globular cluster (GC) which appears associated with two tails of blue stars. The cluster is massive (M {approx} 1.7 Multiplication-Sign 10{sup 6} M{sub Sun }) and highly flattened ({epsilon} {approx} 0.24). From the color-magnitude diagrams of the resolved stars we infer active star formation in the tails over the past {approx}200 Myr. In a diagram of mean projected mass density inside r{sub e} versus total mass the cluster lies at the upper end of the GC distribution, where galaxy nuclei are. The northwest tail is associated with a concentration of H I and infrared (dust/polycyclic aromatic hydrocarbons) emission which appears as part of a much longer stream wrapping around the galaxy. These properties suggest that the cluster may be the nucleus of a former gas-rich satellite galaxy undergoing tidal disruption by NGC 4449. If so, the cluster is seen in an earlier phase compared to other suggested nuclei of disrupted galaxies such as {omega} Cen (Milky Way) and G1 (M31).

• OSTI ID: 22047230
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 745; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
CAMERAS
COLOR
COLOR MODEL
DENSITY
DIAGRAMS
GALAXY CLUSTERS
GALAXY NUCLEI
HYDROGEN 1
IMAGES
INFRARED RADIATION
INFRARED SPECTRA
MASS
MILKY WAY
SATELLITES
SPACE
STARS
TELESCOPES