INT monitoring survey of Local Group dwarf galaxies: star formation history and chemical enrichment

The Local Group (LG) hosts many dwarf galaxies with diverse physical characteristics in terms of morphology, mass, star formation, and metallicity. To this end, LG can offer a unique site to tackle questions about the formation and evolution of galaxies by providing detailed information. While large telescopes are often the first choices for such studies, small telescope surveys that perform dedicated observations are still important, particularly in studying bright objects in the nearby universe. In this regard, we conducted a nine-epoch survey of 55 dwarf galaxies called the "Local Group dwarf galaxies survey" using the 2.5m Isaac Newton Telescope (INT) in the La Palma to identify Long-Period Variable (LPV) stars, namely Asymptotic Giant Branch (AGB) and Red Super Giant (RSG) stars. AGB stars formed at different times and studying their radial distribution and mass-loss rate can shed light on the structure formation in galaxies. To further investigate the evolutionary path of these galaxies, we construct their star formation history (SFH) using the LPV stars, which are at the final stages of their evolution and therefore experience brightness fluctuations on the timescales between hundred to thousand days. In this paper, we present some of the results of the Local Group dwarf galaxies survey.

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

The Astrophysical Journal ◽

10.3847/1538-4357/ac2d96 ◽

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.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308025131 ◽

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.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2903 ◽

2019 ◽

Vol 490 (4) ◽

pp. 5538-5550 ◽

Cited By ~ 3

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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The LCID Project: Star Formation History of Isolated, Local Group Dwarf Galaxies

EAS Publications Series ◽

10.1051/eas/1148006 ◽

2011 ◽

Vol 48 ◽

pp. 37-42 ◽

Cited By ~ 4

Author(s):

S.L. Hidalgo

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxies ◽

Star Formation History ◽

Formation History ◽

History Of

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Recovering the ages and metallicities of stars of a complex stellar population system

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309031895 ◽

2008 ◽

Vol 4 (S258) ◽

pp. 245-252

Author(s):

Sebastian L. Hidalgo ◽

Antonio Aparicio ◽

Carme Gallart

Keyword(s):

Star Formation ◽

Strong Interaction ◽

Stellar Population ◽

Local Group ◽

Dwarf Galaxies ◽

Star Formation History ◽

Host Galaxy ◽

Population System ◽

Formation History ◽

Magnitude Diagram

AbstractWe present a new method to solve for the star-formation history (SFH) of a complex stellar population system from the analysis of the color-magnitude diagram (CMD). The SFH is obtained in four steps: i) computing a synthetic CMD, ii) simulating observational effects, iii) parameterization and sampling of the synthetic and observed CMDs, and iv) solving and averaging the solutions. The consistency and stability of the method have been tested using a mock stellar population.The method has been used to solve the SFH of a set of six isolated Local Group dwarf galaxies observed with HST. The main goal is to probe the effects of cosmological processes, such as reionization in the early star formation, or the ability of SNe feedback to remove gas in small halos, in dwarf galaxies free from environmental effects due to the strong interaction with the host galaxy.

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