The Fornax Dwarf Galaxy as a Remnant of Recent Dwarf-Dwarf Merging in the Local Group

Yozin, C.; Bekki, Kenji

doi:10.1088/2041-8205/756/1/l18

Cited by 47 publications

(58 citation statements)

References 41 publications

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“…The Fornax dwarf galaxy might have interacted violently with the Galaxy and even merged with other dwarf galaxies in the Galactic halo (e.g., Coleman et al 2005;Yozin & Bekki 2012;del Pino et al 2015). Therefore, it might have lost a large fraction of its initial dark matter and field stars through the past interaction and merging.…”

Section: The Mass Budget Problemmentioning

confidence: 99%

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Bekki¹

2017

Mon. Not. R. Astron. Soc.

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Most old globular clusters (GCs) in the Galaxy are observed to have internal chemical abundance spreads in light elements. We discuss a new GC formation scenario based on hierarchical star formation within fractal molecular clouds. In the new scenario, a cluster of bound and unbound star clusters ('star cluster complex', SCC) that have a power-law cluster mass function with a slope (β) of 2 is first formed from a massive gas clump developed in a dwarf galaxy. Such cluster complexes and β = 2 are observed and expected from hierarchical star formation. The most massive star cluster ('main cluster'), which is the progenitor of a GC, can accrete gas ejected from asymptotic giant branch (AGB) stars initially in the cluster and other low-mass clusters before the clusters are tidally stripped or destroyed to become field stars in the dwarf. The SCC is initially embedded in a giant gas hole created by numerous supernovae of the SCC so that cold gas outside the hole can be accreted onto the main cluster later. New stars formed from the accreted gas have chemical abundances that are different from those of the original SCC. Using hydrodynamical simulations of GC formation based on this scenario, we show that the main cluster with the initial mass as large as [2 − 5] × 10 5 M ⊙ can accrete more than 10 5 M ⊙ gas from AGB stars of the SCC. We suggest that merging of hierarchical star cluster complexes can play key roles in stellar halo formation around GCs and self-enrichment processes in the early phase of GC formation.

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Section: The Mass Budget Problemmentioning

confidence: 99%

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Bekki¹

2017

Mon. Not. R. Astron. Soc.

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“…Nichols et al 2012;Yozin & Bekki 2012). A model involving re-accretion of expelled gas proposed for the Carina dSph might also be invoked to explain the formation of Fornax (Pasetto et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Four and one more: The formation history and total mass of globular clusters in the Fornax dSph

Boer

Fraser

2016

A&A

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We have determined the detailed star formation history and total mass of the globular clusters in the Fornax dwarf spheroidal using archival HST WFPC2 data. Colour-magnitude diagrams were constructed in the F555W and F814W bands and corrected for the effect of Fornax field star contamination, after which we used the routine Talos to derive the quantitative star formation history as a function of age and metallicity. The star formation history of the Fornax globular clusters shows that Fornax 1, 2, 3, and 5 are all dominated by ancient (>10 Gyr) populations. Clusters Fornax 1, 2, and 3 display metallicities as low as [Fe/H] = −2.5, while Fornax 5 is slightly more metal-rich at [Fe/H] = −1.8, consistent with resolved and unresolved metallicity tracers. Conversely, Fornax 4 is dominated by a more metal-rich ([Fe/H] = −1.2) and younger population at 10 Gyr, inconsistent with the other clusters. A lack of stellar populations overlapping with the main body of Fornax argues against the nucleus cluster scenario for Fornax 4. The combined stellar mass in globular clusters as derived from the SFH is (9.57 ± 0.93) × 10 5 M , which corresponds to 2.5 ± 0.2 percent of the total stellar mass in Fornax. The mass of the four most metal-poor clusters can also be compared to the metal-poor Fornax field to yield a mass fraction of 19.6 ± 3.1 percent. Therefore, the SFH results provide separate supporting evidence for the unusually high mass fraction of the globular clusters compared to the Fornax field population.

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“…Given that dSphs are preferentially located near the massive spirals Milky Way (MW) and M31, various environmental mechanisms have been invoked to explain their origin (e.g., Einasto et al 1974;Faber & Lin 1983;Kroupa 1997;Mayer et al 2001aMayer et al , 2001bMayer et al , 2006Mayer et al , 2007Kravtsov et al 2004;D'Onghia et al 2009;Klimentowski et al 2009;Kazantzidis et al 2011Kazantzidis et al , 2013Pawlowski et al 2011;Yozin & Bekki 2012). 6 In this context, the "tidal stirring" model (Mayer et al 2001b) posits that gravitational and hydrodynamical interactions with MWsized hosts can transform rotationally supported dwarfs, resembling present-day dwarf irregulars (dIrrs), into systems with the kinematic and structural properties of dSphs.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Ram-pressure Stripping and Supernova Winds on the Tidal Stirring of Disky Dwarfs: Enhanced Transformation into Dwarf Spheroidals

Kazantzidis

Mayer

Callegari

et al. 2017

ApJL

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A conclusive model for the formation of dwarf spheroidal (dSph) galaxies still remains elusive. Owing to their proximity to the massive spirals Milky Way (MW) and M31, various environmental processes have been invoked to explain their origin. In this context, the tidal stirring model postulates that interactions with MW-sized hosts can transform rotationally supported dwarfs, resembling presentday dwarf irregular (dIrr) galaxies, into systems with the kinematic and structural properties of dSphs. Using N-body+SPH simulations, we investigate the dependence of this transformation mechanism on the gas fraction, f gas, in the disk of the progenitor dwarf. Our numerical experiments incorporate for the first time the combined effects of radiative cooling, ram-pressure stripping, star formation, supernova (SN) winds, and a cosmic UV background. For a given orbit inside the primary galaxy, rotationally supported dwarfs with gas fractions akin to those of observed dIrrs (f gas gsim 0.5), demonstrate a substantially enhanced likelihood and efficiency of transformation into dSphs relative to their collisionless (f gas = 0) counterparts. We argue that the combination of ram-pressure stripping and SN winds causes the gas-rich dwarfs to respond more impulsively to tides, augmenting their transformation. When f gas gsim 0.5, disky dwarfs on previously unfavorable low-eccentricity or large-pericenter orbits are still able to transform. On the widest orbits, the transformation is incomplete; the dwarfs retain significant rotational support, a relatively flat shape, and some gas, naturally resembling transition-type systems. We conclude that tidal stirring constitutes a prevalent evolutionary mechanism for shaping the structure of dwarf galaxies within the currently favored CDM cosmological paradigm. AbstractA conclusive model for the formation of dwarf spheroidal (dSph) galaxies still remains elusive. Owing to their proximity to the massive spirals Milky Way (MW) and M31, various environmental processes have been invoked to explain their origin. In this context, the tidal stirring model postulates that interactions with MW-sized hosts can transform rotationally supported dwarfs, resembling present-day dwarf irregular (dIrr) galaxies, into systems with the kinematic and structural properties of dSphs. Using N-body+SPH simulations, we investigate the dependence of this transformation mechanism on the gas fraction, f gas , in the disk of the progenitor dwarf. Our numerical experiments incorporate for the first time the combined effects of radiative cooling, ram-pressure stripping, star formation, supernova (SN) winds, and a cosmic UV background. For a given orbit inside the primary galaxy, rotationally supported dwarfs with gas fractions akin to those of observed dIrrs ( f gas 0.5), demonstrate a substantially enhanced likelihood and efficiency of transformation into dSphs relative to their collisionless ( f gas =0) counterparts. We argue that the combination of ram-pressure stripping and SN winds causes the gas-ric...

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The Fornax Dwarf Galaxy as a Remnant of Recent Dwarf-Dwarf Merging in the Local Group

Cited by 47 publications

References 41 publications

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Four and one more: The formation history and total mass of globular clusters in the Fornax dSph

The Effects of Ram-pressure Stripping and Supernova Winds on the Tidal Stirring of Disky Dwarfs: Enhanced Transformation into Dwarf Spheroidals

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