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.

The Star Formation History of the Local Group Dwarf Galaxy Leo I

1999 ◽  
Vol 118 (5) ◽  
pp. 2245-2261 ◽  
Author(s):  
Carme Gallart ◽  
Wendy L. Freedman ◽  
Antonio Aparicio ◽  
Giampaolo Bertelli ◽  
Cesare Chiosi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Formation History ◽  
History Of

scholarly journals Comparative Morphology of the HST Color-Magnitude Diagram of the Nearby Blue Compact Dwarf Galaxy VII Zw 403 with that of Local Group Dwarfs

1999 ◽  
Vol 192 ◽  
pp. 464-468
Author(s):  
R.E. Schulte-Ladbeck ◽  
U. Hopp ◽  
M. M. Crone
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxy ◽  
Comparative Morphology ◽  
Star Formation History ◽  
Stellar Content ◽  
Halo Structure ◽  
Formation History ◽  
Magnitude Diagram ◽  
Blue Compact Dwarf Galaxy

There are no examples of Blue Compact Dwarf (BCD) galaxies known within the Local Group (LG). Multicolor HST/WFPC2 observations of the nearby BCD VII Zw 403 (= UGC 6456) now resolve single stars with the quality (in terms of limiting magnitude and completeness) previously achieved for LG dwarfs from the ground. We use the MI, V - I color-magnitude diagrams (CMDs) of several LG dwarfs as templates to assess the stellar content and star-formation history (SFH) of the BCD VII Zw 403. This is the first BCD for which a clear spatial segregation of the resolved stellar content into a “core-halo” structure is detected: active star formation is observed in the central region of VII Zw 403, while in “Baade's red sheet”, this young population is strikingly absent. If BCD halos are home to dominant ancient stellar populations, then the fossil record conflicts with delayed-format ion scenarios for dwarfs. We present a sketch of the SFH in the core and halo of VII Zw 403.

scholarly journals The Isaac Newton Telescope Monitoring Survey of Local Group Dwarf Galaxies. II. The Star-formation History of Andromeda I Derived from Long-period Variables

2021 ◽  
Vol 923 (2) ◽  
pp. 164
Author(s):  
Elham Saremi ◽  
Atefeh Javadi ◽  
Mahdieh Navabi ◽  
Jacco Th. van Loon ◽  
Habib G. Khosroshahi ◽  
...  
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Star Formation History ◽  
Isaac Newton ◽  
Long Period ◽  
Formation History ◽  
Monitoring Survey ◽  
Isaac Newton Telescope

Abstract An optical monitoring survey in the nearby dwarf galaxies was carried out with the 2.5 m Isaac Newton Telescope. 55 dwarf galaxies and four isolated globular clusters in the Local Group were observed with the Wide Field Camera. The main aims of this survey are to identify the most evolved asymptotic giant branch stars and red supergiants at the endpoint of their evolution based on their pulsational instability, use their distribution over luminosity to reconstruct the star-formation history (SFH), quantify the dust production and mass loss from modeling the multiwavelength spectral energy distributions, and relate this to luminosity and radius variations. In this second of a series of papers, we present the methodology used to estimate SFH based on long-period variable (LPV) stars and then derive it for Andromeda I (And I) dwarf galaxy as an example of the survey. Using our identified 59 LPV candidates within two half-light radii of And I and Padova stellar evolution models, we estimated the SFH of this galaxy. A major epoch of star formation occurred in And I peaking around 6.6 Gyr ago, reaching 0.0035 ± 0.0016 M ⊙ yr−1 and only slowly declining until 1–2 Gyr ago. The presence of some dusty LPVs in this galaxy corresponds to a slight increase in recent star formation peaking around 800 Myr ago. We evaluate a quenching time around 4 Gyr ago (z < 0.5), which makes And I a late-quenching dSph. A total stellar mass (16 ± 7) × 106 M ⊙ is calculated within two half-light radii of And I for a constant metallicity Z = 0.0007.

scholarly journals The ACS LCID project: accurate measurements of the full star formation history in low metallicity, isolated, Local Group dwarf galaxies

2008 ◽  
Vol 4 (S255) ◽  
pp. 392-396
Author(s):  
Matteo Monelli ◽  
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Star Formation History ◽  
Dominant Component ◽  
Formation History ◽  
Magnitude Diagram ◽  
Technical Issues ◽  
Low Metallicity

AbstractWe present here the latest results of the LCID project (Local Cosmology from Isolated Dwarfs), aimed at recovering the full star formation history (SFH) of six isolated dwarf galaxies of the Local Group (LG). Our method of analysis is based on the IAC-pop code, which derives the SFH of a resolved stellar system by comparing the observed and a model color-magnitude diagram (CMD). We summarize here basic technical issues and the main results concerning our sample of galaxies. We show that LeoA is the only object showing a clear delay in the onset of the major SF event, while all the other galaxies present a dominant component older than 10 Gyrs.

scholarly journals A quantitative demonstration that stellar feedback locally regulates galaxy growth

2020 ◽  
Vol 499 (1) ◽  
pp. 1172-1187
Author(s):  
Javier Zaragoza-Cardiel ◽  
Jacopo Fritz ◽  
Itziar Aretxaga ◽  
Yalia D Mayya ◽  
Daniel Rosa-González ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Stellar Mass ◽  
Stellar Structure ◽  
Star Formation History ◽  
Mass Loading ◽  
Density Profiles ◽  
Stellar Feedback ◽  
Formation History ◽  
Hydrodynamical Simulations

ABSTRACT We have applied stellar population synthesis to 500-pc-sized regions in a sample of 102 galaxy discs observed with the MUSE spectrograph. We derived the star formation history and analyse specifically the ‘recent’ ($20\,\rm {Myr}$) and ‘past’ ($570\,\rm {Myr}$) age bins. Using a star formation self-regulator model, we can derive local mass-loading factors, η for specific regions, and find that this factor depends on the local stellar mass surface density, Σ*, in agreement with the predictions form hydrodynamical simulations including supernova feedback. We integrate the local η–Σ* relation using the stellar mass surface density profiles from the Spitzer Survey of Stellar Structure in Galaxies (S4G) to derive global mass-loading factors, ηG, as a function of stellar mass, M*. The ηG–M* relation found is in very good agreement with hydrodynamical cosmological zoom-in galaxy simulations. The method developed here offers a powerful way of testing different implementations of stellar feedback, to check on how realistic are their predictions.

scholarly journals The Local Group Dwarf Galaxies. The Star Formation Histories derived using the Long Period Variable Stars

2018 ◽  
Vol 14 (S344) ◽  
pp. 125-129
Author(s):  
Elham Saremi ◽  
Atefeh Javadi ◽  
Jacco Th. van Loon ◽  
Habib Khosroshahi ◽  
Sara Rezaei kh ◽  
...  
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Stellar Populations ◽  
Variable Stars ◽  
Star Formation History ◽  
Long Period ◽  
Period Variable ◽  
Monitoring Survey

AbstractDwarf galaxies in the Local Group (LG) represent a distinct as well as diverse family of tracers of the earliest phases of galaxy assembly and the processing resulting from galactic harrassment. Their stellar populations can be resolved and used as probes of the evolution of their host galaxy. In this regard, we present the first reconstruction of the star formation history (SFH) of them using the most evolved AGB stars that are long period variable (LPV). LPV stars trace stellar populations as young as ∼ 30 Myr to as old as the oldest globular clusters. For the nearby, relatively massive and interacting gas-rich dwarf galaxies, the Magellanic Clouds, we found that the bulk of the stars formed ∼ 10 Gyr ago for the LMC, while the strongest episode of star formation in the SMC occurred a few Gyr later. A peak in star formation around 0.7 Gyr ago in both Clouds is likely linked to their recent interaction. The Andromeda satellite pair NGC147/185 show different histories; the main epoch of star formation for NGC 185 occurred 8.3 Gyr ago, followed by a much lower, but relatively constant star formation rate (SFR). In the case of NGC 147, the SFR peaked only 6.9 Gyr ago, staying intense until ∼ 3 Gyr ago. Star formation in the isolated gas-rich dwarf galaxy IC 1613 has proceeded at a steady rate over the past 5 Gyr, without any particular dominant epoch. Due to lack of sufficient data, we have conducted an optical monitoring survey at the Isaac Newton Telescope (INT) of 55 dwarf galaxies in the LG to reconstruct the SFH of them uniformly. The observations are made over ten epochs, spaced approximately three months apart, as the luminosity of LPV stars varies on timescales of months to years. The system of galactic satellites of the large Andromeda spiral galaxy (M31) forms one of the key targets of our monitoring survey. We present the first results in the And I dwarf galaxy, where we discovered 116 LPVs among over 10,000 stars.

scholarly journals Star Formation History in the Fornax Dwarf Galaxy from HST data

1999 ◽  
Vol 192 ◽  
pp. 174-178 ◽  
Author(s):  
G. Marconi ◽  
R. Buonanno ◽  
M. Castellani ◽  
C. E. Corsi ◽  
R. Zinn
Keyword(s):  
Star Formation ◽  
Globular Cluster ◽  
Main Sequence ◽  
Dwarf Galaxy ◽  
Hubble Space Telescope ◽  
Global Analysis ◽  
Stellar Populations ◽  
Star Formation History ◽  
A Value ◽  
Formation History

Using observations from the Hubble Space Telescope archive, color-magnitude diagrams have been constructed for globular Cluster 4 in the Fornax dSph galaxy and its surrounding field. These diagrams extend below the main-sequence turnoffs and have yielded measurements of the ages of the populations. In particular, from our analysis Cluster 4 shows [Fe/H] ≃ 2.0, a value significantly lower than that derived for the Fornax field ([Fe/H] ≃ −1.40). Putting our results in the frame of the findings of Buonanno et al. (1998) for the Fornax clusters 1, 2, 3 and 5, a global analysis of the properties of Fornax stellar populations has been performed.

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