scholarly journals Evolution of Interstellar Clouds in Local Group Dwarf Spheroidal Galaxies in the Context of Their Star Formation Histories

1999 ◽  
Vol 520 (2) ◽  
pp. 607-612 ◽  
Author(s):  
Hiroyuki Hirashita
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Interstellar Clouds ◽  
Dwarf Spheroidal Galaxies ◽  
Star Formation Histories ◽  
Spheroidal Galaxies

The spatial segregation impact on the star formation histories of nearby dwarf spheroidal galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 389-391
Author(s):  
Lidia Makarova ◽  
Dmitry Makarov
Keyword(s):  
Comparative Analysis ◽  
Star Formation ◽  
Middle Ages ◽  
Local Group ◽  
Stellar Populations ◽  
Spatial Segregation ◽  
Dwarf Spheroidal Galaxies ◽  
Zero Velocity ◽  
Star Formation Histories ◽  
Spheroidal Galaxies

AbstractUsing our HST/ACS observations of the recently found isolated dwarf spheroidal galaxies, we homogeneously measured their star formation histories (SFHs). We determined SF rate as a function of time, as well as age and metallicity of the stellar populations. All objects demonstrate complex SFH, with a significant portion of stars formed 10–13 Gyr ago. Nevertheless, stars of middle ages (1–8 Gyr) are presented. In order to understand how the SF parameters influence the evolution of dSphs, we also studied a sample of nearest dSphs in different environment: isolated (d < 2 Mpc); beyond the Local Group virial radius (but within the LG zero velocity sphere); and the satellites of M31 located within the virial zone (300 kpc). Using archival HST/ACS observations, we measured their SFHs. A comparative analysis of the parameters obtained give us a possibility to distinguish a possible effect of the spatial segregation on the dSphs evolution scenario.

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

2018 ◽  
Vol 616 ◽  
pp. A96 ◽  
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.

The Local Group Dwarf Spheroidal Galaxies: A Key to Building Blocks in the Universe

2005 ◽  
Vol 201 ◽  
pp. 469-470
Author(s):  
Hiroyuki. Hirashita ◽  
Naoyuki. Tamura ◽  
Tsutomu T. Takeuchi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Building Blocks ◽  
Star Formation History ◽  
High Mass ◽  
Dwarf Spheroidal Galaxies ◽  
The Hierarchical Structure ◽  
History Of ◽  
Low Mass ◽  
Spheroidal Galaxies

Recent studies have been revealing the properties of dwarf spheroidal galaxies (dSphs). Their low mass indicates that the dSphs may provide a clue to physical properties of the building blocks in the hierarchical structure formation. We select the Local Group dSphs as a sample. To obtain the information on the star formation history of dSphs, we investigate the relation between their metallicity and virial mass. According to our scenario, the star formation efficiency of the dSphs is low because of strong regulation. This is consistent with their high mass-to-light ratios. We also comment on the environmental effects on the dSphs.

scholarly journals Spatial segregation impact on star formation in nearby dwarf spheroidal galaxies

2021 ◽  
Vol 502 (2) ◽  
pp. 1623-1632
Author(s):  
L N Makarova ◽  
D I Makarov
Keyword(s):  
Comparative Analysis ◽  
Star Formation ◽  
Middle Ages ◽  
Local Group ◽  
Hubble Space Telescope ◽  
Spatial Segregation ◽  
Dwarf Spheroidal Galaxies ◽  
M 31 ◽  
Advanced Camera For Surveys ◽  
Star Formation Histories

ABSTRACT Using our Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) observations of the recently found isolated dwarf spheroidal (dSph) galaxies, we homogeneously measured their star formation histories (SFHs). We determined SF rate as a function of time, as well as age and metallicity of the stellar populations. All objects demonstrate complex SFH, with a significant portion of stars formed 10–13 Gyr ago. Nevertheless, stars of middle ages (1–8 Gyr) are presented. In order to understand how the SF parameters influence the evolution of dSphs, we also studied a sample of nearest dSphs in different environment: isolated (d &lt; 2 Mpc); beyond the Local Group (LG) virial radius (but within the LG zero-velocity sphere); and the satellites of M 31 located within the virial zone (300 kpc). Using archival HST/ACS observations, we measured their SFHs. A comparative analysis of the parameters obtained allow us to distinguish a possible effect of the spatial segregation on the dSphs evolution scenario.

scholarly journals Chemical evolution models for local group dwarf spheroidal galaxies: the evolution of Fe-peak elements

2009 ◽  
Vol 5 (S265) ◽  
pp. 245-246
Author(s):  
Gustavo A. Lanfranchi ◽  
Francesca Matteucci ◽  
Gabriele Cescutti
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Local Group ◽  
Formation Rate ◽  
Sharp Decrease ◽  
Dwarf Spheroidal Galaxies ◽  
Galactic Winds ◽  
Formation Efficiency ◽  
Chemical Evolution Model ◽  
Spheroidal Galaxies

AbstractThe evolution of Fe-peak elements of several Local Group Dwarf Spheroidal Galaxies are discussed based on the comparison between a chemical evolution model and obsevations. In our scenario, the evolution of these galaxies are mainly controlled by a low star formation efficiency coupled with very intense galactic winds. The low star formation rate gives rise to the observed low metallicities and to [alpha/Fe] and [s/Fe] ratios below solar, whereas the intense galactic winds are responsible for the sharp decrease observed in several abundance ratios. The shape of the stellar metallicity distributions are defined by both parameters and the observed data cannot be reproduced without evoking galactic winds. The same scenario applied to a standard model fits very well several Fe-peak elements, with different nucleosynthesis prescriptions for each set of elements.

scholarly journals Evolutionary Histories of Dwarf Galaxies in the Local Group

1999 ◽  
Vol 192 ◽  
pp. 17-38 ◽  
Author(s):  
Eva K. Grebel
Keyword(s):  
Star Formation ◽  
Common Property ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Absolute Magnitude ◽  
Morphological Type ◽  
Red Giants ◽  
Dwarf Spheroidal Galaxies ◽  
Central Surface ◽  
Star Formation Histories

The star formation histories of Local Group (LG) dwarf galaxies and more distant potential LG members are reviewed. Problems in defining the spatial extent of the LG and membership are briefly discussed. The morphological types found in the LG are presented, and it is suggested that we see continuous evolution from low-mass dwarf irregulars (dIrrs) to dwarf spheroidal galaxies (dSphs) in the LG.Star formation histories for LG dwarfs and nearby LG candidates are compiled using population boxes. No two dwarfs, irrespective of morphological type, show the same evolutionary history, and all vary widely in ages of their subpopulations and in their enrichment history. The lack of gas in dSphs and certain dwarf ellipticals (dEs) is puzzling, both with respect to their star formation histories and the expected mass loss from red giants, but a new photoionization scenario may reconcile these contradictions. Old populations, often spatially very extended, may be a common property of dwarf galaxies, though their fractions can be very small. Almost all types of dwarf galaxies studied in detail so far show spatial variations in ages and abundances such as radial age/metallicity gradients. The observed star formation histories impose constraints on merger and accretion scenarios.Properties of the Milky Way dwarf spheroidals are compared to the M31 dSphs and discussed in the framework of the ram pressure/tidal stripping scenario. It is demonstrated that the newly discovered LG dwarfs follow the same relationship for central surface brightness, mean metallicity, and absolute magnitude as the other LG dwarfs.

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