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

2019 ◽  
Vol 489 (4) ◽  
pp. 4574-4588 ◽  
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.

scholarly journals Orbits versus Star Formation Histories: A Progress Report

1999 ◽  
Vol 192 ◽  
pp. 447-450 ◽  
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.

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.

scholarly journals Substructure in Dwarf Galaxies

2004 ◽  
Vol 21 (4) ◽  
pp. 379-381
Author(s):  
Matthew Coleman
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Large Scale ◽  
Stellar Population ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Tidal Interaction ◽  
Kinematic Evolution ◽  
Dark Material ◽  
Star Formation Histories

AbstractRecent years have seen a series of large-scale photometric surveys with the aim of detecting substructure in nearby dwarf galaxies. Some of these objects display a varying distribution of each stellar population, reflecting their star formation histories. Also, dwarf galaxies are dominated by dark matter, therefore luminous substructure may represent a perturbation in the underlying dark material. Substructure can also be the effect of tidal interaction, such as the disruption of the Sagittarius dSph by the Milky Way. Therefore, substructure in dwarf galaxies manifests the stellar, structural, and kinematic evolution of these objects.

scholarly journals Be it therefore resolved: cosmological simulations of dwarf galaxies with 30 solar mass resolution

2019 ◽  
Vol 490 (3) ◽  
pp. 4447-4463 ◽  
Author(s):  
Coral Wheeler ◽  
Philip F Hopkins ◽  
Andrew B Pace ◽  
Shea Garrison-Kimmel ◽  
Michael Boylan-Kolchin ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Stellar Rotation ◽  
Solar Mass ◽  
Dynamical Mass ◽  
Low Mass ◽  
Star Formation Histories ◽  
First Time

ABSTRACT We study a suite of extremely high-resolution cosmological Feedback in Realistic Environments simulations of dwarf galaxies ($M_{\rm halo} \lesssim 10^{10}\rm \, M_{\odot }$), run to z = 0 with $30\, \mathrm{M}_{\odot }$ resolution, sufficient (for the first time) to resolve the internal structure of individual supernovae remnants within the cooling radius. Every halo with $M_{\rm halo} \gtrsim 10^{8.6}\, \mathrm{M}_{\odot }$ is populated by a resolved stellar galaxy, suggesting very low-mass dwarfs may be ubiquitous in the field. Our ultra-faint dwarfs (UFDs; $M_{\ast }\lt 10^{5}\, \mathrm{M}_{\odot }$) have their star formation (SF) truncated early (z ≳ 2), likely by reionization, while classical dwarfs ($M_{\ast }\gt 10^{5}\, \mathrm{M}_{\odot }$) continue forming stars to z < 0.5. The systems have bursty star formation histories, forming most of their stars in periods of elevated SF strongly clustered in both space and time. This allows our dwarf with M*/Mhalo > 10−4 to form a dark matter core ${\gt}200\rm \, pc$, while lower mass UFDs exhibit cusps down to ${\lesssim}100\rm \, pc$, as expected from energetic arguments. Our dwarfs with $M_{\ast }\gt 10^{4}\, \mathrm{M}_{\odot }$ have half-mass radii (R1/2) in agreement with Local Group (LG) dwarfs (dynamical mass versus R1/2 and stellar rotation also resemble observations). The lowest mass UFDs are below surface brightness limits of current surveys but are potentially visible in next-generation surveys (e.g. LSST). The stellar metallicities are lower than in LG dwarfs; this may reflect pre-enrichment of the LG by the massive hosts or Pop-III stars. Consistency with lower resolution studies implies that our simulations are numerically robust (for a given physical model).

Local Group Dwarf Galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 29-37
Author(s):  
Andrew A. Cole
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Cosmic Time ◽  
Star Formation History ◽  
Gas Content ◽  
Cosmological Context ◽  
Low Mass ◽  
Formation And Evolution ◽  
Star Formation Histories

AbstractLocal Group dwarf galaxies are a unique astrophysical laboratory because they are the only objects in which we can reliably and precisely characterize the star formation histories of low-mass galaxies going back to the epoch of reionization. There are of order 100 known galaxies less massive than the Small Magellanic Cloud within ~1 Megaparsec of the Milky Way, with a vide variety of star formation history, gas content, and mass to light ratios. In this overview the current understanding of the formation and evolution of low-mass galaxies across cosmic time will be presented, and the possibility of drawing links between the properties of individual systems and the broader Local Group and cosmological context will be discussed. Local Group dwarfs will remain a uniquely powerful testbed to constrain the properties of dark matter and to evaluate the performance of simulations for the foreseeable future.

scholarly journals The cumulative star formation histories of dwarf galaxies with TNG50. I: environment-driven diversity and connection to quenching

2021 ◽  
Vol 508 (2) ◽  
pp. 1652-1674 ◽  
Author(s):  
Gandhali D Joshi ◽  
Annalisa Pillepich ◽  
Dylan Nelson ◽  
Elad Zinger ◽  
Federico Marinacci ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Control Sample ◽  
Stellar Mass ◽  
Key Factors ◽  
Star Forming ◽  
Theoretical Predictions ◽  
Mass Assembly ◽  
Star Formation Histories ◽  
Vast Range

ABSTRACT We present the cumulative star formation histories (SFHs) of >15 000 dwarf galaxies ($M_{\rm *}=10^{7-10}\, {\rm M}_{\odot }$) simulated with the TNG50 run of the IllustrisTNG suite across a vast range of environments. The key factors that determine the dwarfs’ SFHs are their central/satellite status and stellar mass, with centrals and more massive dwarfs assembling their stellar mass at later times, on average, compared to satellites and lower mass dwarfs. Satellites (in hosts of mass $M_{\rm 200c, host}=10^{12-14.3}\, {\rm M}_{\odot }$) assembled 90 per cent of their stellar mass ${\sim}7.0_{-5.5}^{+3.3}$ Gyr ago, on average and within the 10th to 90th percentiles, while the centrals did so only ${\sim}1.0_{-0.5}^{+4.0}$ Gyr ago. TNG50 predicts a large diversity in SFHs, so that individual dwarfs can have significantly different cumulative SFHs compared to the stacked median SFHs. Satellite dwarfs with the highest stellar mass to host cluster mass ratios have the latest stellar mass assembly. Conversely, satellites at fixed stellar and host halo mass found closer to the cluster centre or accreted at earlier times show significantly earlier stellar mass assembly. These trends and the shapes of the SFHs themselves are a manifestation of the varying proportions within a given subsample of quenched versus star-forming galaxies, which exhibit markedly distinct SFH shapes. Finally, satellite dwarfs in the most massive hosts have higher SFRs at early times, well before accretion into their z = 0 host, compared to a control sample of centrals mass-matched at the time of accretion. This is the result of the satellites being preprocessed in smaller hosts prior to accretion. Our findings are useful theoretical predictions for comparison to future resolved stellar population observations.

scholarly journals THE STAR FORMATION HISTORIES OF LOCAL GROUP DWARF GALAXIES. I.HUBBLE SPACE TELESCOPE/WIDE FIELD PLANETARY CAMERA 2 OBSERVATIONS

2014 ◽  
Vol 789 (2) ◽  
pp. 147 ◽  
Author(s):  
Daniel R. Weisz ◽  
Andrew E. Dolphin ◽  
Evan D. Skillman ◽  
Jon Holtzman ◽  
Karoline M. Gilbert ◽  
...  
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Wide Field ◽  
Space Telescope ◽  
Star Formation Histories

scholarly journals Star formation at the edge of the Local Group: a rising star formation history in the isolated galaxy WLM

2019 ◽  
Vol 490 (4) ◽  
pp. 5538-5550 ◽  
Author(s):  
Saundra M Albers ◽  
Daniel R Weisz ◽  
Andrew A Cole ◽  
Andrew E Dolphin ◽  
Evan D Skillman ◽  
...  
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Hubble Space Telescope ◽  
Optimal Path ◽  
Stellar Mass ◽  
Star Formation History ◽  
Stellar Feedback ◽  
Formation History

ABSTRACT We present the star formation history (SFH) of the isolated (D ∼ 970 kpc) Local Group dwarf galaxy Wolf–Lundmark–Melotte (WLM) measured from colour–magnitude diagrams (CMDs) constructed from deep Hubble Space Telescope imaging. Our observations include a central ($0.5 \, r_h$) and outer field ($0.7 \, r_h$) that reach below the oldest main-sequence turn-off. WLM has no early dominant episode of star formation: 20 per cent of its stellar mass formed by ∼12.5 Gyr ago ($z$ ∼ 5). It also has an SFR that rises to the present with 50 per cent of the stellar mass within the most recent 5 Gyr ($z$ < 0.7). There is evidence of a strong age gradient: the mean age of the outer field is 5 Gyr older than the inner field despite being only 0.4 kpc apart. Some models suggest such steep gradients are associated with strong stellar feedback and dark-matter core creation. The SFHs of real isolated dwarf galaxies and those from the Feedback in Realistic Environment suite are in good agreement for M⋆($z$ = 0) ∼ 107–109M⊙, but in worse agreement at lower masses ($M_{\star }(z=0) \sim 10^5\!-\!10^7 \, \mathrm{M}_{\odot }$). These differences may be explainable by systematics in the models (e.g. reionization model) and/or observations (HST field placement). We suggest that a coordinated effort to get deep CMDs between HST/JWST (crowded central fields) and WFIRST (wide-area halo coverage) is the optimal path for measuring global SFHs of isolated dwarf galaxies.

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