On the formation of star clusters in the merger NGC 6240

Pasquali, A.; Grijs, Richard de; Gallagher, J.

doi:10.1046/j.1365-8711.2003.06933.x

Cited by 29 publications

(44 citation statements)

References 78 publications

(119 reference statements)

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“…The immediate implication of a similar result for the NGC 6745 clusters would be that galaxy interactions indeed produce extremely massive star clusters, as also suggested by Maraston et al (2004) based on their analysis of NGC 7252-W3; see also Pasquali, de Grijs & Gallagher (2003) and Pollack, Max & Schneider (2007) for tentative indications that the more massive clusters in the galaxy merger NGC 6240 tend to form closer to the most intense interaction regions near the galaxy's double nucleus. This gives important insights into the still largely unknown star and star cluster formation processes in extreme environments.…”

Section: A "Super" Star Cluster Grown Old?supporting

confidence: 55%

The Long-term Survival Chances of Young Massive Star Clusters

Grijs

Parmentier

2007

Chin. J. Astron. Astrophys.

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We review the long-term survival chances of young massive star clusters (YMCs), hallmarks of intense starburst episodes often associated with violent galaxy interactions. We address the key question as to whether at least some of these YMCs can be considered protoglobular clusters (GCs), in which case these would be expected to evolve into counterparts of the ubiquitous old GCs believed to be among the oldest galactic building blocks. In the absence of significant external perturbations, the key factor determining a cluster's long-term survival chances is the shape of its stellar initial mass function (IMF). It is, however, not straightforward to assess the IMF shape in unresolved extragalactic YMCs. We discuss in detail the promise of using high-resolution spectroscopy to make progress towards this goal, as well as the numerous pitfalls associated with this approach. We also discuss the latest progress in worldwide efforts to better understand the evolution of entire cluster systems, the disruption processes they are affected by, and whether we can use recently gained insights to determine the nature of at least some of the YMCs observed in extragalactic starbursts as proto-GCs. We conclude that there is an increasing body of evidence that GC formation appears to be continuing until today; their long-term evolution crucially depends on their environmental conditions, however.

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Section: A "Super" Star Cluster Grown Old?supporting

confidence: 55%

The Long-term Survival Chances of Young Massive Star Clusters

Grijs

Parmentier

2007

Chin. J. Astron. Astrophys.

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“…To systematically estimate ages and extinctions for the clumps in Table 2, we used a χ 2 minimization calculation (e.g., Pasquali et al 2003) to determine the fit of the observed colors to that of the models: In this equation, N is the number of colors used in the analysis, obs i is the observed color, model i is the corresponding model color, and σ i is the uncertainty in the obs i color. A good fit is indicated by χ 2 < N. In these calculations, we did not include filters with non-detections.…”

Section: Agesmentioning

confidence: 99%

Stochastic “Beads on a String” in the Accretion Tail of Arp 285

Smith

Struck

Hancock

et al. 2008

The Astronomical Journal

101

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We present Spitzer infrared, Galaxy Evolution Explorer UV, and Sloan Digitized Sky Survey and Southeastern Association for Research in Astronomy optical images of the peculiar interacting galaxy pair Arp 285 (NGC 2856/4), and compare with a new numerical model of the interaction. We estimate the ages of clumps of star formation in these galaxies using population synthesis models, carefully considering the uncertainties on these ages. This system contains a striking example of "beads on a string": a series of star-formation complexes ∼1 kpc apart. These "beads" are found in a tail-like feature that is perpendicular to the disk of NGC 2856, which implies that it was formed from material accreted from the companion NGC 2854. The extreme blueness of the optical/UV colors and redness of the mid-infrared colors implies very young stellar ages (∼4-20 Myr) for these star-forming regions. Spectral decomposition of these "beads" shows excess emission above the modeled stellar continuum in the 3.6 µm and 4.5 µm bands, indicating either contributions from interstellar matter to these fluxes or a second older stellar population. These clumps have −12.0 < M B < −10.6, thus they are less luminous than most dwarf galaxies. Our model suggests that bridge material falling into the potential of the companion overshoots the companion. The gas then piles up at apogalacticon before falling back onto the companion, and star formation occurs in the pile-up. There was a time delay of ∼500 Myr between the point of closest approach between the two galaxies and the initiation of star formation in this feature. A luminous (M B ∼ −13.6) extended (FWHM ∼ 1.3 kpc) "bright spot" is visible at the northwestern edge of the NGC 2856 disk, with an intermediate stellar population (400-1500 Myr). Our model suggests that this feature is part of a expanding ripple-like "arc" created by an off-center ring-galaxy-like collision between the two disks.

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“…This may thus be an example of an SSC that does not remain bound over the lifetime of the interaction. Nevertheless, a number of SSCs in a variety of galaxies have properties that are promising examples of newly emerging galaxies and globular clusters (see Bastian et al 2005;Lisenfeld et al 2004;Braine et al 2001;Pasquali et al 2003;Gilbert et al 2000).…”

Section: Tidal Tail Stellar Cluster Massmentioning

confidence: 99%

Remarkable Disk and Off-Nuclear Starburst Activity in the Tadpole Galaxy as revealed by theSpitzer Space Telescope

Jarrett¹,

Polletta²,

Fournon³

et al. 2006

Astron J

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We present ground-based optical and Spitzer Space Telescope infrared imaging observations of the interacting galaxy UGC 10214, the Tadpole galaxy (z ¼ 0:0310), focusing on the star formation activity in the nuclear, disk, spiral arms, and tidal tail regions. The ground-based optical data set spans a wavelength range between 0.3 and 0.8 m, the near-IR data set spans 1-2.2 m, and the Spitzer IR data set spans 3-70 m. The major findings of this study are that the Tadpole is actively forming stars in the main disk outside of the nucleus and in the tidal plume, with an estimated mean star formation rate of $2-4 M yr À1 . The most prominent sites of mid-IR emission define a ''ring'' morphology that, combined with the overall morphology of the system, suggests the interaction may belong to the rare class of offcenter collisional ring systems that form both shock-induced rings of star formation and tidal plumes. In stark contrast to the disk star formation, the nuclear emission is solely powered by older stars, with little evidence for ongoing star formation at the center of the Tadpole. Extranuclear star formation accounts for >50% of the total star formation in the disk and spiral arms, featuring infrared-bright ''hot spots'' that exhibit strong polycyclic aromatic hydrocarbon (PAH) emission, the band strength of which is comparable to that of late-type star-forming disk galaxies. The tidal tail, which extends 2 0 ($75 kpc) into the intergalactic medium, is populated by supermassive star clusters, M $ 10 6 M , likely triggered by the galaxy-galaxy interaction that has distorted UGC 10214 into its current ''tadpole'' shape. The Tadpole is therefore an example of an off-nuclear or tidal-tail starburst, with several large sites of massive star formation in the disk and in the plume, including the most prominent Hubble Space Telescope-revealed cluster, J160616.85+552640.6. The clusters exhibit remarkable IR properties, including exceptionally strong 24 m emission relative to the underlying starlight, hot dust continuum, and PAH emission, with an estimated current star formation rate of $0.1-0.4 M yr À1 , representing >10% of the total star formation in the system. We estimate the mass of the largest cluster to be $ 1:4 1:6 ð Þ; 10 6 M based on the g 0 -band (0.5 m) and near-IR (2.2 m) integrated fluxes in combination with an assumed mass-to-light ratio appropriate to young clusters, or large enough to be classified as a nascent dwarf galaxy or globular cluster.

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On the formation of star clusters in the merger NGC 6240

Cited by 29 publications

References 78 publications

The Long-term Survival Chances of Young Massive Star Clusters

The Long-term Survival Chances of Young Massive Star Clusters

Stochastic “Beads on a String” in the Accretion Tail of Arp 285

Remarkable Disk and Off-Nuclear Starburst Activity in the Tadpole Galaxy as revealed by theSpitzer Space Telescope

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