scholarly journals THE ASYMPTOTIC GIANT BRANCH AND THE TIP OF THE RED GIANT BRANCH AS PROBES OF STAR FORMATION HISTORY: THE NEARBY DWARF IRREGULAR GALAXY KKH 98

2010 ◽  
Vol 712 (1) ◽  
pp. 469-483 ◽  
Author(s):  
J. Melbourne ◽  
B. Williams ◽  
J. Dalcanton ◽  
S. M. Ammons ◽  
C. Max ◽  
...  
Keyword(s):  
Star Formation ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Irregular Galaxy ◽  
Formation History ◽  
Red Giant

AGB and RGB stars in the dwarf irregular galaxy Leo A

2021 ◽  
Vol 647 ◽  
pp. A170
Author(s):  
Alina Leščinskaitė ◽  
Rima Stonkutė ◽  
Vladas Vansevičius
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Dwarf Galaxy ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Photometric Method ◽  
Agb Stars ◽  
Irregular Galaxy ◽  
Red Giant

Context. Leo A is a gas-rich dwarf irregular galaxy of low stellar mass located in the outskirts of the Local Group. It has an extended star formation history with stellar populations spanning a wide age range (∼0.01−10 Gyr). As Leo A is a well-isolated dwarf galaxy, it is a perfect target to study a galactic structure formed entirely by processes of self-induced star formation. Aims. Our aim is to study populations of the brightest asymptotic giant branch (AGB) stars and red giant branch (RGB) stars over the entire extent of the Leo A galaxy. Methods. We analysed populations of AGB and RGB stars in the Leo A galaxy using multicolour photometry data obtained with the Subaru Suprime-Cam (B, V, R, I, Hα) and HST ACS (F475W, F814W) cameras. In order to separate the Milky Way and Leo A populations of red stars, we developed a photometric method that enabled us to study the spatial distribution of AGB and RGB stars within the Leo A galaxy. Results. We found a previously unknown sequence of 26 peculiar RGB stars which probably have a strong CN band in their spectra (∼380−390 nm). This conclusion is supported by the infrared CN spectral features observed in four of these stars with available spectra from the literature. Additionally, we present a catalogue of 32 luminous AGB stars and 3 candidate AGB stars. Twelve AGB stars (three of them might have dusty envelopes) from this sample are newly identified; the remaining 20 AGB stars were already presented in the literature based on near-infrared observations. By splitting the RGB sequence into blue and red parts, we revealed different spatial distributions of the two subsets, with the former being more centrally concentrated than the latter. Cross-identification with spectroscopic data available in the literature suggests that the bulk of blue and red RGB stars are, on average, similar in metallicity; however, the red RGB stars might have an excess of metal-deficient stars of [Fe/H] < −1.8. We also found that the distributions of luminous AGB and blue RGB stars have nearly equal scale lengths (0.′87 ± 0.′06 and 0.′89 ± 0.′09, respectively), indicating that they could belong to the same generation. This conclusion is strengthened by the similarities of the cumulative distributions of AGB and blue RGB stars, both showing more centrally concentrated populations compared to red RGB stars. There is also a prominent decline in the ratio of AGB to RGB stars with an increasing radius. These results suggest that the star-forming disk of Leo A is shrinking, which is in agreement with the outside-in star formation scenario of dwarf galaxy evolution.

Variations in Star Formation History and the Red Giant Branch Tip

2004 ◽  
Vol 606 (2) ◽  
pp. 869-893 ◽  
Author(s):  
Michael K. Barker ◽  
Ata Sarajedini ◽  
Jason Harris
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Formation History ◽  
Red Giant

scholarly journals Recovering the Star Formation History of IC1613 Dwarf Galaxy Using Evolved Stars

2018 ◽  
Vol 14 (S344) ◽  
pp. 77-80
Author(s):  
Seyed Azim Hashemi ◽  
Atefeh Javadi ◽  
Jacco Th. van Loon
Keyword(s):  
Star Formation ◽  
Dwarf Galaxy ◽  
Stellar Populations ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Evolved Stars ◽  
Formation History ◽  
The Galaxy ◽  
Red Supergiants ◽  
Period Variable

AbstractDetermining the star formation history (SFH) is key to understand the formation and evolution of dwarf galaxies. Recovering the SFH in resolved galaxies is mostly based on deep colour–magnitude diagrams (CMDs), which trace the signatures of multiple evolutionary stages of their stellar populations. In distant and unresolved galaxies, the integrated light of the galaxy can be decomposed, albeit made difficult by an age–metallicity degeneracy. Another solution to determine the SFH of resolved galaxies is based on evolved stars; these luminous stars are the most accessible tracers of the underlying stellar populations and can trace the entire SFH. Here we present a novel method based on long period variable (LPV) evolved asymptotic giant branch (AGB) stars and red supergiants (RSGs). We applied this method to reconstruct the SFH for IC1613, an irregular dwarf galaxy at a distance of 750 kpc. Our results provide an independent confirmation that no major episode of star formation occurred in IC1613 over the past 5 Gyr.

scholarly journals Addendum: The Dwarf Irregular Galaxy Sextans A. II. Recent Star Formation History [Astron. J. [BF]114[/BF], 2527 (1997)]

1998 ◽  
Vol 115 (1) ◽  
pp. 152-153 ◽  
Author(s):  
Robbie C. Dohm-Palmer ◽  
Evan D. Skillman ◽  
A. Saha ◽  
E. Tolstoy ◽  
Mario Mateo ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Irregular Galaxy ◽  
Formation History

The Local Group Dwarf Irregular Galaxy NGC 6822.III. The Recent Star Formation History

1996 ◽  
Vol 112 ◽  
pp. 2596 ◽  
Author(s):  
C. Gallart ◽  
A. Aparicio ◽  
G. Bertelli ◽  
C. Chiosi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Star Formation History ◽  
Irregular Galaxy ◽  
Formation History ◽  
Ngc 6822

scholarly journals Cosmology with Nearby Dwarf Galaxies: The View from HST

1998 ◽  
Vol 11 (1) ◽  
pp. 127-130
Author(s):  
Eline Tolstoy
Keyword(s):  
Star Formation ◽  
Stellar Evolution ◽  
Direct Evidence ◽  
Global Scale ◽  
Star Formation History ◽  
Monte Carlo Techniques ◽  
Formation History ◽  
Magnitude Diagram ◽  
Red Giant ◽  
Sophisticated Analysis

Stellar Evolution theory is based upon well understood physics and provides clear predictions as to how a Colour-Magnitude Diagram (CMD) will change due to effects of age and metallicity. The theory has been tested by looking at nearby coeval star clusters. The power of applying CMD analysis to galaxies has been demonstrated in studies of the Carina dSph (Smecker-Hane et al. 1996). In Carina the observation of separate, distinct Main Sequence (MS) Turnoffs has forced us to believe that this small, nearby companion of our Galaxy has had a very complex star formation history. No similar direct evidence for “bursting” behaviour on a global scale has been seen indisputably in larger systems. Partly this is due to the greater distances of larger systems, but also to the complications in distinguishing old star formation events (> 1 Gyr old) in systems which are currently forming stars. Where we lack MS turnoffs we have to resort to statistical modeling of the CMD. This has been applied using a a number of different approaches, but all generally based on Monte-Carlo techniques (e.g. Tosi et al. 1992; Bertelli et al. 1992; Tolstoy &; Saha 1996). However, even using these more sophisticated analysis techniques, it is difficult to find unique solutions. This is mostly due to the age-metallicity degeneracy on the Red Giant Branch (RGB). The RGB is usually the most populated, easiest to observe phase of stellar evolution. The Carina CMD reveals the dangers of blindly interpreting the RGB, because from the RGB alone it is impossible to extract the information revealed by the MS Turnoffs.

CEPHEID VARIABLE STARS IN THE PEGASUS DWARF IRREGULAR GALAXY: CONSTRAINTS ON THE STAR FORMATION HISTORY

2009 ◽  
Vol 137 (3) ◽  
pp. 3619-3631 ◽  
Author(s):  
I. Meschin ◽  
C. Gallart ◽  
A. Aparicio ◽  
S. Cassisi ◽  
A. Rosenberg
Keyword(s):  
Star Formation ◽  
Variable Stars ◽  
Star Formation History ◽  
Irregular Galaxy ◽  
Formation History

Breaking the age–metallicity degeneracy: The metallicity distribution and star formation history of the Large Magellanic Cloud

2008 ◽  
Vol 4 (S256) ◽  
pp. 263-268 ◽  
Author(s):  
Andrew A. Cole ◽  
Aaron J. Grocholski ◽  
Doug Geisler ◽  
Ata Sarajedini ◽  
Verne V. Smith ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Large Magellanic Cloud ◽  
Star Formation History ◽  
Red Giants ◽  
Formation History ◽  
History Of ◽  
Red Giant ◽  
Metallicity Distribution ◽  
Modelling Process

AbstractWe have obtained metallicities from near-infrared calcium triplet spectroscopy for nearly a thousand red giants in 28 fields spanning a range of radial distances from the center of the bar to near the tidal radius. We have used these data to investigate the radius-metallicity and age-metallicity relations. A powerful application of these data is in conjunction with the analysis of deep HST color–magnitude diagrams (CMDs). Most of the power in determining a robust star-formation history from a CMD comes from the main-sequence turnoff and subgiant branches. The age-metallicity degeneracy that results is largely broken by the red giant branch color, but theoretical model RGB colors remain uncertain. By incorporating the observed metallicity distribution function into the modelling process, a star-formation history with massively increased precision and accuracy can be derived. We incorporate the observed metallicity distribution of the LMC bar into a maximum-likelihood analysis of the bar CMD, and present a new star formation history and age–metallicity relation for the bar. The bar is certainly younger than the disk as a whole, and the most reliable estimates of its age are in the 5–6 Gyr range, when the mean gas abundance of the LMC had already increased to [Fe/H] ≳ −0.6. There is no obvious metallicity gradient among the old stars in the LMC disk out to a distance of 8–10 kpc, but the bar is more metal-rich than the disk by ≈0.1–0.2 dex. This is likely to be the result of the bar's younger average age. In both disk and bar, 95% of the red giants are more metal-rich than [Fe/H] = −1.2.

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