scholarly journals Near-Infrared Stellar Populations in the metal-poor, Dwarf irregular Galaxies Sextans A and Leo A

2018 ◽  
Vol 14 (S343) ◽  
pp. 429-430
Author(s):  
Olivia C. Jones ◽  
Matthew T. Maclay ◽  
Martha L. Boyer ◽  
Margaret Meixner ◽  
Iain McDonald
Keyword(s):  
Near Infrared ◽  
Infrared Camera ◽  
Stellar Populations ◽  
Asymptotic Giant Branch ◽  
Evolved Stars ◽  
Irregular Galaxies ◽  
Tentative Evidence ◽  
Period Variable ◽  
Red Giant ◽  
Dwarf Irregular Galaxies

AbstractWe present JHK observations of the metal-poor $$(\left[ {{\rm{Fe}}/{\rm{H}}} \right] < - 1.40)$$ dwarf-irregular galaxies, Leo A and Sextans A, obtained with the WIYN High-resolution Infrared Camera. Their near-IR stellar populations are characterized by using a combination of color-magnitude diagrams and by identifying long-period variable (LPV) stars. We detected red giant and asymptotic giant branch (AGB) stars, consistent with membership of the galaxy’s intermediate-age populations (2-8 Gyr old). We identify 32 dusty evolved stars in Leo A and 101 dusty stars in Sextans A, confirming that metal-poor stars can form substantial amounts of dust. We also find tentative evidence for oxygen-rich dust formation at low metallicity, contradicting previous models that suggest oxygen-rich dust production is inhibited in metal-poor environments. The majority of this dust is produced by a few very dusty evolved stars.

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 Near-infrared Stellar Populations in the Metal-poor, Dwarf Irregular Galaxies Sextans A and Leo A

2018 ◽  
Vol 854 (2) ◽  
pp. 117 ◽  
Author(s):  
Olivia C. Jones ◽  
Matthew T. Maclay ◽  
Martha L. Boyer ◽  
Margaret Meixner ◽  
Iain McDonald ◽  
...  
Keyword(s):  
Near Infrared ◽  
Stellar Populations ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

scholarly journals On the precision of full-spectrum fitting of simple stellar populations – I. Well-sampled populations

2020 ◽  
Vol 498 (2) ◽  
pp. 2814-2832
Author(s):  
Randa Asa’d ◽  
Paul Goudfrooij
Keyword(s):  
Random Noise ◽  
Star Clusters ◽  
Stellar Populations ◽  
Asymptotic Giant Branch ◽  
Full Spectrum ◽  
Red Giant ◽  
Set Up ◽  
Age Range ◽  
Spectrum Fitting ◽  
Giant Branch Stars

ABSTRACT We investigate the precision of the ages and metallicities of 21 000 mock simple stellar populations (SSPs) determined through full-spectrum fitting. The mock SSPs cover an age range of 6.8 &lt; log (age/yr) &lt; 10.2, for three wavelength ranges in the optical regime, using both Padova and MIST isochrone models. Random noise is added to the model spectra to achieve S/N ratios between 10 and 100 per wavelength pixel. We find that for S/N ≥ 50, this technique can yield ages of SSPs to an overall precision of ∆log (age/yr)∼01 for ages in the ranges 7.0 ≤ log (age/yr) ≤ 8.3 and 8.9 ≤ log (age/yr) ≤ 9.4. For the age ranges of 8.3 ≤ log (age/yr) ≤ 8.9 and log (age/yr) ≥ 9.5, which have significant flux contributions from asymptotic giant branch and red giant branch stars, respectively, the age uncertainty rises to about ±0.3 dex. The precision of age and metallicity estimation using this method depends significantly on the S/N and the wavelength range used in the fitting. We quantify the systematic differences in age predicted by the MIST and Padova isochrone models, due to their different assumptions about stellar physics in various important (i.e. luminous) phases of stellar evolution, which needs to be taken in consideration when comparing ages of star clusters obtained using these popular models. Knowing the strengths and limitations of this technique is crucial in interpreting the results obtained for real star clusters and for deciding the optimal instrument set-up before performing the observations.

scholarly journals Discovery of a nitrogen-enhanced mildly metal-poor binary system: Possible evidence for pollution from an extinct AGB star

2019 ◽  
Vol 631 ◽  
pp. A97 ◽  
Author(s):  
José G. Fernández-Trincado ◽  
Ronald Mennickent ◽  
Mauricio Cabezas ◽  
Olga Zamora ◽  
Sarah L. Martell ◽  
...  
Keyword(s):  
Binary System ◽  
Radial Velocity ◽  
Globular Clusters ◽  
Near Infrared ◽  
Asymptotic Giant Branch ◽  
Main Element ◽  
Large Variability ◽  
Asymptotic Giant Branch Star ◽  
Red Giant ◽  
Branch Star

We report the serendipitous discovery of a nitrogen-rich, mildly metal-poor ([Fe/H] = −1.08) giant star in a single-lined spectroscopic binary system found in the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) survey, Data Release 14 (DR14). Previous work has assumed that two percent of halo giants with unusual elemental abundances have been evaporated from globular clusters, but other origins for their abundance signatures, including binary mass transfer, must also be explored. We present the results of an abundance reanalysis of the APOGEE-2 high-resolution near-infrared spectrum of 2M12451043+1217401 with the Brussels Automatic Stellar Parameter (BACCHUS) automated spectral analysis code. We manually re-derive the main element families, namely light elements (C, N), elements (O, Mg, Si), the iron-peak element (Fe), s-process element (Ce), and light odd-Z element (Al). Our analysis confirms the N-rich nature of 2M12451043+1217401, which has a [N/Fe] ratio of +0.69, and shows that the abundances of C and Al are slightly discrepant from those of a typical mildly metal-poor red giant branch star, but exhibit Mg, Si, O and s-process abundances (Ce) of typical field stars. We also detect a particularly large variability in the radial velocity of this star over the period of the APOGEE-2 observations; the most likely orbit fit to the radial velocity data has a period of 730.89  ±  106.86 days, a velocity semi-amplitude of 9.92  ±  0.14 km s−1, and an eccentricity of ∼0.1276  ±  0.1174. These data support the hypothesis of a binary companion, which has probably been polluted by a now-extinct asymptotic giant branch star.

scholarly journals Deep near-infrared surface photometry and properties of Local Volume dwarf irregular galaxies

2014 ◽  
Vol 444 (4) ◽  
pp. 3052-3077 ◽  
Author(s):  
T. Young ◽  
H. Jerjen ◽  
Á. R. López-Sánchez ◽  
B. S. Koribalski
Keyword(s):  
Near Infrared ◽  
Surface Photometry ◽  
Local Volume ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

scholarly journals DEEP MIXING IN EVOLVED STARS. II. INTERPRETING Li ABUNDANCES IN RED GIANT BRANCH AND ASYMPTOTIC GIANT BRANCH STARS

2011 ◽  
Vol 741 (1) ◽  
pp. 26 ◽  
Author(s):  
S. Palmerini ◽  
S. Cristallo ◽  
M. Busso ◽  
C. Abia ◽  
S. Uttenthaler ◽  
...  
Keyword(s):  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Deep Mixing ◽  
Evolved Stars ◽  
Red Giant ◽  
Giant Branch Stars

Long term near infrared observation of very bright stars at Kagoshima University

2017 ◽  
Vol 12 (S330) ◽  
pp. 333-334
Author(s):  
Takairo Naagaya
Keyword(s):  
Near Infrared ◽  
Infrared Camera ◽  
Variable Stars ◽  
New Method ◽  
Infrared Observation ◽  
Long Period ◽  
The Status ◽  
Period Variable ◽  
K Band

AbstractWe are monitoring nearby long period variable stars (LPVs) in the near infrared K band to establish their precise Period-Luminosity relation. However, they are very bright in the near-infrared and it is difficult to observe them because they are easily saturated on the modern near-infrared camera. We developed a special ND filter, named Local Attenuation Filter (LAF), to observe very bright stars. Using LAF, we can observe not only the very bright targets without saturation but also reference stars in the same image. We can perform the accurate relative photometry for the bright stars. We present this new method to observe bright stars as well as the status of our monitoring of nearby LPVs.

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.

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