相关论文: Carbon Stars and C/M Ratio in the WLM Dwarf Irregu…

The M33 galaxy is a nearby, relatively metal-poor, late-type spiral. Its proximity and almost face-on inclination means that it projects over a large area on the sky, making it an ideal candidate for wide-field CCD mosaic imaging.…

We investigate the star formation history and metallicity of the Local Group irregular dwarf galaxy WLM using wide-field JHK near-infrared imaging, spanning a region of approximately 1 sq. degree, obtained with WFCAM on UKIRT. JHK…

We present abundances of carbon and oxygen as well as abundance ratios 12C/13C for a sample of carbon stars in the LMC, SMC, Carina, Sculptor and Fornax dwarf galaxies. The overall metallicities in these dwarf galaxies are lower than in the…

The number ratio of carbon-rich to oxygen-rich asymptotic giant branch (AGB) stars (the so-called C/M ratio) is closely related to the evolution environment of the host galaxy. This work studies the C/M ratio in 14 galaxies within the Local…

We present the discovery of twelve metal-poor and distant pre-main sequence (PMS) candidates in the dwarf irregular galaxy Wolf-Lundmark-Melotte (WLM)~968 kpc away, at a present-day metallicity of [Fe/H] around $-$0.9. These candidates have…

[Abridged] The chemical composition of two stars in WLM has been determined from high quality UVES data obtained at the VLT UT2 (program 65.N-0375). The model atmospheres analysis shows that they have the same metallicity, [Fe/H] = -0.38…

We investigate the intermediate-age asymptotic giant branch stellar population of two Local Group dwarf irregular galaxies to characterize their carbon star population in near-infrared (IR). Our work is based on J and K-band SOFI near-IR…

Abundance analysis of carbon has been performed in a sample of 80 late F and early G type dwarf stars in the metallicity range -1.06 < [Fe/H] < 0.26 using the forbidden [C I] line at 8727 A. This line is presumably less sensitive to…

Using Spitzer IRAC and MIPS observations of the Large Magellanic Cloud, we have identified 13 objects that have extremely red mid-IR colors. Follow-up Spitzer IRS observations of seven of these sources reveal varying amounts of SiC and C2H2…

We explore the ratio (C/M) of carbon-rich to oxygen-rich thermally pulsing asymptotic giant branch(TP-AGB) stars in the disk of M31 using a combination of moderate-resolution optical spectroscopy from the Spectroscopic Landscape of…

Carbon stars (with atmospheric C/O$>1$) range widely in temperature and luminosity, from low mass dwarfs to asymptotic giant branch stars (AGB). The main sequence dwarf carbon (dC) stars have inherited carbon-rich material from an AGB…

We present spectroscopic data for 180 red giant branch stars in the isolated dwarf irregular galaxy WLM. Observations of the Calcium II triplet lines in spectra of RGB stars covering the entire galaxy were obtained with FORS2 at the VLT and…

We present new Hubble Space Telescope WFC3/IR medium-band photometry of the compact elliptical galaxy M32, chemically resolving its thermally pulsating asymptotic giant branch stars. We find 2829 M-type stars and 57 C stars. The carbon…

Wolf-Lundmark-Melotte (WLM) is a Local Group dwarf irregular (dIrr) galaxy with a metallicity 13% of solar. At 1 Mpc, the relative isolation of WLM provides a unique opportunity to investigate the internal mechanisms of star formation at…

Based on our prior accurate determination of fundamental parameters for 36 Galactic A-, F- and G-type supergiants and bright giants (luminosity classes I and II), we undertook a non-LTE analysis of the carbon abundance in their atmospheres.…

We investigate the stellar populations and molecular gas properties of a star-forming region within the dwarf irregular (dIrr) galaxy WLM. Low-metallicity dIrrs like WLM offer a valuable window into star formation in environments that are…

We report the discovery of broad Wolf-Rayet emission lines in the Multiple Mirror Telescope (MMT) spectrum of the NW component of I Zw 18, the lowest-metallicity blue compact dwarf (BCD) galaxy known. Two broad Wolf-Rayet (W-R) bumps at the…

As part of a reanalysis of galactic Asymptotic Giant Branch (AGB) stars at infrared (IR) wavelengths, we discuss a sample (357) of carbon stars for which mass loss rates, near-IR photometry and distance estimates exist. For 252 sources we…

We analyze resolved stellar near-infrared photometry of 21 HST fields in M31 to constrain the impact of metallicity on the formation of carbon stars. Observations of nearby galaxies show that the carbon stars are increasingly rare at higher…

We present 12CO J = 1-0 and J = 2-1 observations of the low metallicity (12 + log(O/H) = 7.74) Local Group dwarf irregular galaxy WLM made with the 15 m SEST and 14 m FCRAO telescopes. Despite the presence a number of HII regions, we find…