The chemical connection between damped Lyman-α systems and Local Group dwarf galaxies

Abundances of the volatile elements S and Zn have now been measured in around 80 individual stars in the Sculptor dwarf spheroidal galaxy, covering the metallicity range − 2.4 ≤ [Fe/H] ≤−0.9. These two elements are of particular interest as they are not depleted onto dust in gas, and their ratio, [S/Zn], has thus commonly been used as a proxy for [α/Fe] in Damped Lyman-α systems (DLAs). The S abundances in Sculptor are similar to other α-elements in this galaxy, consistent with S being mainly created in core-collapse supernovae, but also having some contribution from type Ia supernovae. However, our results show that Zn and Fe do not trace all the same nucleosynthetic production channels. In particular, (contrary to Fe) Zn is not significantly produced by type Ia supernovae. Thus, [S/Zn] cannot be reliably used as a proxy for [α/Fe]. We propose [O/S] as a function of [S/H] as a possible alternative. At higher metallicities, the values of [S/Zn] measured in DLAs are inconsistent with those in local dwarf galaxies, and are more compatible with the Milky Way disk. Low-metallicity DLAs are, however, consistent with the most metal-poor stars in Local Group dwarf spheroidal galaxies. Assuming that the dust depletions of S and Zn are negligible, our comparison indicates that the star formation histories of DLAs are on average different from both the Milky Way and the Sculptor dwarf spheroidal galaxy.

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Pushing back the limits: detailed properties of dwarf galaxies in a ΛCDM universe

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832669 ◽

2018 ◽

Vol 616 ◽

pp. A96 ◽

Cited By ~ 26

Author(s):

Yves Revaz ◽

Pascale Jablonka

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxies ◽

Mass Scale ◽

Dwarf Spheroidal Galaxies ◽

The Galaxy ◽

Dynamical Simulations ◽

Ursa Minor ◽

Stellar Properties ◽

Star Formation Histories

We present the results of a set of high-resolution chemo-dynamical simulations of dwarf galaxies in a ΛCDM cosmology. Out of an original (3.4 Mpc/h)3 cosmological box, a sample of 27 systems are re-simulated from z = 70 to z = 0 using a zoom-in technique. Gas and stellar properties are confronted to the observations in the greatest details: in addition to the galaxy global properties, we investigated the model galaxy velocity dispersion profiles, half-light radii, star formation histories, stellar metallicity distributions, and [Mg/Fe] abundance ratios. The formation and sustainability of the metallicity gradients and kinematically distinct stellar populations are also tackled. We show how the properties of six Local Group dwarf galaxies, NGC 6622, Andromeda II, Sculptor, Sextans, Ursa Minor and Draco are reproduced, and how they pertain to three main galaxy build-up modes. Our results indicate that the interaction with a massive central galaxy could be needed for a handful of Local Group dwarf spheroidal galaxies only, the vast majority of the systems and their variety of star formation histories arising naturally from a ΛCDM framework. We find that models fitting well the local Group dwarf galaxies are embedded in dark haloes of mass between 5 × 108 to a few 109 M⊙, without any missing satellite problem. We confirm the failure of the abundance matching approach at the mass scale of dwarf galaxies. Some of the observed faint however gas-rich galaxies with residual star formation, such as Leo T and Leo P, remain challenging. They point out the need of a better understanding of the UV-background heating.

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COLOR DISPERSION AND MILKY-WAY-LIKE REDDENING AMONG TYPE Ia SUPERNOVAE

The Astrophysical Journal ◽

10.1088/0004-637x/780/1/37 ◽

2013 ◽

Vol 780 (1) ◽

pp. 37 ◽

Cited By ~ 63

Author(s):

Daniel M. Scolnic ◽

Adam G. Riess ◽

Ryan J. Foley ◽

Armin Rest ◽

Steven A. Rodney ◽

...

Keyword(s):

Milky Way ◽

Type Ia Supernovae ◽

Type Ia ◽

Ia Supernovae

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Determining the motion of the local group using type IA supernovae light curve shapes

The Astrophysical Journal ◽

10.1086/187897 ◽

1995 ◽

Vol 445 ◽

pp. L91 ◽

Cited By ~ 70

Author(s):

Adam G. Riess ◽

William H. Press ◽

Robert P. Kirshner

Keyword(s):

Light Curve ◽

Local Group ◽

Type Ia Supernovae ◽

Type Ia ◽

Ia Supernovae

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Delay Time Distributions of Type Ia Supernovae from Galaxy and Cosmic Star Formation Histories

The Astrophysical Journal ◽

10.3847/1538-4357/ab6a97 ◽

2020 ◽

Vol 890 (2) ◽

pp. 140 ◽

Cited By ~ 4

Author(s):

Louis-Gregory Strolger ◽

Steven A. Rodney ◽

Camilla Pacifici ◽

Gautham Narayan ◽

Or Graur

Keyword(s):

Star Formation ◽

Delay Time ◽

Type Ia Supernovae ◽

Type Ia ◽

Ia Supernovae ◽

Star Formation Histories

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Orbits versus Star Formation Histories: A Progress Report

Symposium - International Astronomical Union ◽

10.1017/s0074180900204488 ◽

1999 ◽

Vol 192 ◽

pp. 447-450 ◽

Cited By ~ 9

Author(s):

Eva K. Grebel ◽

Tsafrir Kolatt ◽

Wolfgang Brandner

Keyword(s):

Star Formation ◽

Milky Way ◽

Statistical Approach ◽

Local Group ◽

Dwarf Galaxies ◽

Progress Report ◽

Polar Plane ◽

Preliminary Results ◽

Star Formation Histories

Milky Way dwarf companions and satellites of distant spirals seem to show a preference for polar orbits. We suggest that five out of six M31 dwarf spheroidal companions as well as two dwarf irregulars may also be located near a polar plane.We briefly discuss preliminary results from a statistical approach to study correlations between star formation histories and orbits of Local Group dwarf galaxies, such as a possible correlation between star formation episodes and galaxy separations.

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The formation of the Milky Way halo and its dwarf satellites; a NLTE-1D abundance analysis

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731582 ◽

2017 ◽

Vol 608 ◽

pp. A89 ◽

Cited By ~ 20

Author(s):

L. Mashonkina ◽

P. Jablonka ◽

T. Sitnova ◽

Yu. Pakhomov ◽

P. North

Keyword(s):

Milky Way ◽

Dwarf Galaxy ◽

Chemical Species ◽

Dwarf Spheroidal Galaxies ◽

Massive Galaxies ◽

Type Ia ◽

Ursa Minor ◽

R Process ◽

Ia Supernovae ◽

Process Elements

We present the non-local thermodynamic equilibrium (NLTE) abundances of up to 10 chemical species in a sample of 59 very metal-poor (VMP, −4 ≤ [Fe/H] ≾−2) stars in seven dwarf spheroidal galaxies (dSphs) and in the Milky Way (MW) halo. Our results are based on high-resolution spectroscopic datasets and homogeneous and accurate atmospheric parameters determined in Paper I. We show that once the NLTE effects are properly taken into account, all massive galaxies in our sample, that is, the MW halo and the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax, reveal a similar plateau at [α/Fe] ≃ 0.3 for each of the α-process elements: Mg, Ca, and Ti. We put on a firm ground the evidence for a decline in α/Fe with increasing metallicity in the Boötes I ultra-faint dwarf galaxy (UFD), that is most probably due to the ejecta of type Ia supernovae. For Na/Fe, Na/Mg, and Al/Mg, the MW halo and all dSphs reveal indistinguishable trends with metallicity, suggesting that the processes of Na and Al synthesis are identical in all systems, independent of their mass. The dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the classical dSphs, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr. We show that Sr in the massive galaxies is well correlated with Mg suggesting a strong link to massive stars and that its origin is essentially independent of Ba, for most of the [Ba/H] range. Our three UFDs, that is Boötes I, UMa II, and Leo IV, are depleted in Sr and Ba relative to Fe and Mg, with very similar ratios of [Sr/Mg] ≃−1.3 and [Ba/Mg] ≃−1 on the entire range of their Mg abundances. The subsolar Sr/Ba ratios of Boötes I and UMa II indicate a common r-process origin of their neutron-capture elements. Sculptor remains the classical dSph, in which the evidence for inhomogeneous mixing in the early evolution stage, at [Fe/H] <−2, is the strongest.

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Type Ia Supernovae in a Hierarchical Galaxy Formation Model: The Milky Way

The Astrophysical Journal ◽

10.1086/503180 ◽

2006 ◽

Vol 643 (2) ◽

pp. 863-880 ◽

Cited By ~ 12

Author(s):

Masahiro Nagashima ◽

Takashi Okamoto

Keyword(s):

Galaxy Formation ◽

Milky Way ◽

Type Ia Supernovae ◽

Formation Model ◽

Type Ia ◽

Ia Supernovae

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Star formation histories of dwarf galaxies in the FIRE simulations: dependence on mass and Local Group environment

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2507 ◽

2019 ◽

Vol 489 (4) ◽

pp. 4574-4588 ◽

Cited By ~ 17

Author(s):

Shea Garrison-Kimmel ◽

Andrew Wetzel ◽

Philip F Hopkins ◽

Robyn Sanderson ◽

Kareem El-Badry ◽

...

Keyword(s):

Star Formation ◽

Milky Way ◽

Local Group ◽

Dwarf Galaxies ◽

Near Field ◽

Stellar Mass ◽

Group Environment ◽

Zoom In ◽

The Individual ◽

Star Formation Histories

ABSTRACT We study star formation histories (SFHs) of 500 dwarf galaxies (stellar mass $M_\ast =10^5\!-\!10^9\, \rm {M}_\odot$) from FIRE-2 cosmological zoom-in simulations. We compare dwarfs around individual Milky Way (MW)-mass galaxies, dwarfs in Local Group (LG)-like environments, and true field (i.e. isolated) dwarf galaxies. We reproduce observed trends wherein higher mass dwarfs quench later (if at all), regardless of environment. We also identify differences between the environments, both in terms of ‘satellite versus central’ and ‘LG versus individual MW versus isolated dwarf central.’ Around the individual MW-mass hosts, we recover the result expected from environmental quenching: central galaxies in the ‘near field’ have more extended SFHs than their satellite counterparts, with the former more closely resemble isolated (true field) dwarfs (though near-field centrals are still somewhat earlier forming). However, this difference is muted in the LG-like environments, where both near-field centrals and satellites have similar SFHs, which resemble satellites of single MW-mass hosts. This distinction is strongest for M* = 106–$10^7\, \rm {M}_\odot$ but exists at other masses. Our results suggest that the paired halo nature of the LG may regulate star formation in dwarf galaxies even beyond the virial radii of the MW and Andromeda. Caution is needed when comparing zoom-in simulations targeting isolated dwarf galaxies against observed dwarf galaxies in the LG.

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