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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
- Source :
- The Astrophysical Journal. 712:469-483
- Publication Year :
- 2010
- Publisher :
- American Astronomical Society, 2010.
-
Abstract
- We investigate the utility of the asymptotic giant branch (AGB) and the red giant branch (RGB) as probes of the star formation history (SFH) of the nearby (D=2.5 Mpc) dwarf irregular galaxy, KKH 98. Near-infrared (IR) Keck Laser Guide Star Adaptive Optics (AO) images resolve 592 IR bright stars reaching over 1 magnitude below the Tip of the Red Giant Branch. Significantly deeper optical (F475W and F814W) Hubble Space Telescope images of the same field contain over 2500 stars, reaching to the Red Clump and the Main Sequence turn-off for 0.5 Gyr old populations. Compared to the optical color magnitude diagram (CMD), the near-IR CMD shows significantly tighter AGB sequences, providing a good probe of the intermediate age (0.5 - 5 Gyr) populations. We match observed CMDs with stellar evolution models to recover the SFH of KKH 98. On average, the galaxy has experienced relatively constant low-level star formation (5 x 10^-4 Mo yr^-1) for much of cosmic time. Except for the youngest main sequence populations (age < 0.1 Gyr), which are typically fainter than the AO data flux limit, the SFH estimated from the the 592 IR bright stars is a reasonable match to that derived from the much larger optical data set. Differences between the optical and IR derived SFHs for 0.1 - 1 Gyr populations suggest that current stellar evolution models may be over-producing the AGB by as much as a factor of three in this galaxy. At the depth of the AO data, the IR luminous stars are not crowded. Therefore these techniques can potentially be used to determine the stellar populations of galaxies at significantly further distances.<br />15 pages, 14 figs, accepted for publication in ApJ
- Subjects :
- Physics
Cosmology and Nongalactic Astrophysics (astro-ph.CO)
010504 meteorology & atmospheric sciences
Star formation
FOS: Physical sciences
Astronomy and Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
Astrophysics
01 natural sciences
Galaxy
Red-giant branch
Space and Planetary Science
0103 physical sciences
Astrophysics::Solar and Stellar Astrophysics
Asymptotic giant branch
Astrophysics::Earth and Planetary Astrophysics
Irregular galaxy
010303 astronomy & astrophysics
Red clump
Stellar evolution
Astrophysics::Galaxy Astrophysics
Astrophysics - Cosmology and Nongalactic Astrophysics
0105 earth and related environmental sciences
Dwarf galaxy
Subjects
Details
- ISSN :
- 15384357 and 0004637X
- Volume :
- 712
- Database :
- OpenAIRE
- Journal :
- The Astrophysical Journal
- Accession number :
- edsair.doi.dedup.....406af3ac966b7454855ef9df7b019d32