The star formation and chemical evolution history of the Fornax dwarf spheroidal galaxy

Boer, T. J. L. de; Tolstoy, Eline; Hill, V.; Saha, Abhijit; Olszewski, Edward W.; Mateo, Mario; Starkenburg, Else; Battaglia, G.; Walker, Matthew G.

doi:10.1051/0004-6361/201219547

Cited by 153 publications

(169 citation statements)

References 71 publications

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“…For both Sculptor and Leo I the corresponding range is 1.0-6.0 × 10 6 M⊙. Observational estimates of stellar mass are ∼ 1.7-4.3 × 10 7 M⊙ for Fornax, ∼ 0.2 × 10 7 M⊙ for Sculptor and ∼ 0.5 × 10 7 M⊙ for Leo I (Wolf et al 2010;McConnachie 2012;de Boer et al 2012).…”

Section: Selecting Simulated Analogues Of Real Dsphsmentioning

confidence: 93%

Tidal features of classical Milky Way satellites in a Λ cold dark matter universe

Wang

Fattahi

Cooper

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We use the APOSTLE cosmological hydrodynamic simulations to examine the effects of tidal stripping on cold dark matter (CDM) subhaloes that host three of the most luminous Milky Way (MW) dwarf satellite galaxies: Fornax, Sculptor, and Leo I. We identify simulated satellites that match the observed spatial and kinematic distributions of stars in these galaxies, and track their evolution after infall. We find ∼ 30% of subhaloes hosting satellites with present-day stellar mass 10 6 -10 8 M ⊙ experience > 20% stellar mass loss after infall. Fornax analogues have earlier infall times compared to Sculptor and Leo I analogues. Star formation in Fornax analogues continues for ∼ 3-6 Gyr after infall, whereas Sculptor and Leo I analogues stop forming stars < 2-3 Gyr after infall. Fornax analogues typically show more significant stellar mass loss and exhibit stellar tidal tails, whereas Sculptor and Leo I analogues, which are more deeply embedded in their host DM haloes at infall, do not show substantial mass loss due to tides. When additionally comparing the orbital motion of the host subaloes to the measured proper motion of Fornax we find the matching more difficult; host subhaloes tend to have pericentres smaller than that measured ones for Fornax itself. From the kinematic and orbital data, we estimate that Fornax has lost 10 − 20% of its infall stellar mass. Our best estimate for the surface brightness of a stellar tidal stream associated with Fornax is Σ ∼ 32.6 mag arcsec −2 , which may be detectable with deep imaging surveys such as DES and LSST.

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Section: Selecting Simulated Analogues Of Real Dsphsmentioning

confidence: 93%

Tidal features of classical Milky Way satellites in a Λ cold dark matter universe

Wang

Fattahi

Cooper

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…LG dSphs (Tolstoy et al 2004;Battaglia et al 2006Battaglia et al , 2011de Boer et al 2012a;de Boer et al 2012b). Furthermore, recent wide field photometric studies have found signs of extra-tidal stars, suggesting that Carina likely experienced tidal encounters, which could be responsible for the episodic SFH (Battaglia et al 2012;McMonigal et al 2014).…”

Section: Introductionmentioning

confidence: 99%

The episodic star formation history of the Carina dwarf spheroidal galaxy

Boer

Tolstoy

Lemasle

et al. 2014

A&A

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We present deep photometry of the Carina dwarf spheroidal galaxy in the B and V filters from CTIO/MOSAIC out to and beyond the tidal radius of r ell ≈ 0.48 degrees. The accurately calibrated photometry is combined with spectroscopic metallicity distributions of red giant branch (RGB) stars to determine the detailed star formation and chemical evolution history of Carina. The star formation history (SFH) confirms the episodic formation history of Carina and quantifies the duration and strength of each episode in great detail as a function of radius from the centre. Two main episodes of star formation occurred at old (>8 Gyr) and intermediate (2−8 Gyr) ages, both enriching stars starting from low metallicities ([Fe/H] < −2 dex). By dividing the SFH into two components, we determine that 60 ± 9 percent of the total number of stars formed within the intermediate-age episode. Furthermore, within the tidal radius (0.48 degrees or 888 pc) a total mass in stars of 1.07 ± 0.08 × 10 6 M was formed, giving Carina a stellar mass-to-light ratio of 1.8 ± 0.8. By combining the detailed SFH with spectroscopic observations of RGB stars, we determined the detailed age-metallicity relation of each episode and the timescale of α-element evolution of Carina from individual stars. The oldest episode displays a tight age-metallicity relation during ≈6 Gyr with steadily declining α-element abundances and a possible α-element "knee" visible at [Fe/H] ≈ −2.5 dex. The intermediate-age sequence displays a more complex age-metallicity relation starting from low metallicity and a sequence in α-element abundances with a slope much steeper than observed in the old episode, starting from [Fe/H] = −1.8 dex and [Mg/Fe] ≈ 0.4 dex and declining to Mg-poor values ([Mg/Fe] ≤ −0.5 dex). This clearly indicates that the two episodes of star formation formed from gas with different abundance patterns, which is inconsistent with simple evolution in an isolated system.

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“…They are not currently forming stars and show prominent old stellar populations, but their star formation histories (SFHs) are not uniformly old (see the recent reviews of Tolstoy et al 2009;Weisz et al 2014). Indeed, dSphs show a wide variety of SFHs; from systems that essentially completed forming their stars ∼ 10 Gyr ago, like Cetus and Draco (Monelli et al 2010;Aparicio et al 2001) to others where star formation was sustained over a long time and ceased only as recently as 6 Gyr ago (e.g., Leo II, Dolphin 2002) or even < 1 Gyr ago (e.g., Fornax, Stetson et al 1998;Saviane et al 2000;Battaglia et al 2006;de Boer et al 2012, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Mergers and the outside-in formation of dwarf spheroidals

Benítez-Llambay¹,

Navarro²,

Abadi³

et al. 2015

Mon. Not. R. Astron. Soc.

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We use a cosmological simulation of the formation of the Local Group to explore the origin of age and metallicity gradients in dwarf spheroidal galaxies. We find that a number of simulated dwarfs form "outside-in", with an old, metal-poor population that surrounds a younger, more concentrated metal-rich component, reminiscent of dwarf spheroidals like Sculptor or Sextans. We focus on a few examples where stars form in two populations distinct in age in order to elucidate the origin of these gradients. The spatial distributions of the two components reflect their diverse origin; the old stellar component is assembled through mergers, but the young population forms largely in situ. The older component results from a first episode of star formation that begins early but is quickly shut off by the combined effects of stellar feedback and reionization. The younger component forms when a late accretion event adds gas and reignites star formation. The effect of mergers is to disperse the old stellar population, increasing their radius and decreasing their central density relative to the young population. We argue that dwarf-dwarf mergers offer a plausible scenario for the formation of systems with multiple distinct populations and, more generally, for the origin of age and metallicity gradients in dwarf spheroidals.

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The star formation and chemical evolution history of the Fornax dwarf spheroidal galaxy

Cited by 153 publications

References 71 publications

Tidal features of classical Milky Way satellites in a Λ cold dark matter universe

Tidal features of classical Milky Way satellites in a Λ cold dark matter universe

The episodic star formation history of the Carina dwarf spheroidal galaxy

Mergers and the outside-in formation of dwarf spheroidals

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