Luminous AGB stars in nearby galaxies

Tsalmantza, P.; Kontizas, E.; Cambrésy, L.; Genova, F.; Dapergolas, A.; Kontizas, M.

doi:10.1051/0004-6361:20053142

Cited by 12 publications

(12 citation statements)

References 32 publications

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“…7a. This number is close to that found by Tsalmantza et al (2006), though there is a slight difference due to the different selection criteria of stars used in our and their studies. For comparison, we plot in the figure the YSOs in the Taurus region (Luhman et al 2006) as well as the unreddened field stars (i.e., dwarfs and giants; Bessell & Brett 1988).…”

Section: Contamination By Agb Stars and Ysossupporting

confidence: 90%

“…These sources can cause a serious overestimation of the true color excess. In the LMC, there are a number of YSOs forming in GMCs (e.g., Fukui et al 2008), and AGB stars are known to be widely distributed (Tsalmantza et al 2006). These intrinsically red sources, however, occupy only a small fraction of the 2MASS point sources in the LMC, and they can be removed by setting an appropriate X 1 value (e.g., X 1 = 95%, see Sect.…”

Section: Methods and Model To Measure The Color Excessmentioning

confidence: 99%

“…These objects are known to have intrinsically red colors that could lead color-excess methods to overestimate extinction. Tsalmantza et al (2006) searched for AGB stars in nearby galaxies based on the 2MASS point source catalog, and they identified 7137 AGB star candidates in the LMC. Following Davidge (2003), they defined AGB stars as sources having colors H − K S > 0.4 mag and J − K S > 1.5 mag.…”

Section: Contamination By Agb Stars and Ysosmentioning

confidence: 99%

“…7). If we adopt the criteria of Tsalmantza et al (2006) to eliminate AGB stars from our sample to derive the extinction maps, most of the YSOs and reddened field stars -in addition to the AGBs -would be excluded, leading to an underestimation of the true A V . We therefore did not attempt to exclude AGB stars or YSOs based on their colors, but rather by setting X 1 in Eqs.…”

Section: Contamination By Agb Stars and Ysosmentioning

confidence: 99%

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Extinction and dust/gas ratio in LMC molecular clouds

Dobashi

Bernard

Hughes

et al. 2008

A&A

125

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Aims. The goal of this paper is to measure the dust content and distribution in the Large Magellanic Cloud (LMC) by comparing extinction maps produced in the near-infrared wavelengths and the spatial distribution of the neutral and molecular gas, as traced by H i and CO observations.Methods. In order to derive an extinction map of the LMC, we have developed a new method to measure the color excess of dark clouds, using the 2MASS all-sky survey. Classical methods to measure the color excess (including the NICE method) tend to underestimate the true color excess if the clouds are significantly contaminated by unreddened foreground stars, as is the case in the LMC. We propose a new method that uses the color of the X percentile reddest stars and which is robust against such contamination. Using this method, it is possible to infer the positions of dark clouds with respect to the star distribution by comparing the observed color excess as a function of the percentile used and that predicted by a model. Results. On the basis of the resulting extinction map, we perform a correlation analysis for a set of dark molecular clouds. Assuming similar infrared absorption properties for the dust in the neutral and molecular phases, we derive the absorption-to-column density ratio A V N H and the CO-to-H 2 conversion factor X CO . We show that A V N H increases from the outskirts of the LMC towards the 30 Dor star-forming region. This can be explained either by a systematic increase of the dust abundance, or by the presence of an additional gas component not traced by H i or CO, but strongly correlated to the H i distribution. If dust abundance is allowed to vary, the derived X CO factors for the selected regions are several times lower than those derived from a virial analysis of the CO data. This could indicate that molecular clouds in the LMC are not gravitationally bound, or that they are bounded by substantial external pressure. However, the X CO values derived from absorption can be reconciled with the virial results assuming a constant value for the dust abundance and the existence of an additional, unseen gas component. These results are in agreement with those derived for the LMC from diffuse far-infrared emission.

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Section: Contamination By Agb Stars and Ysossupporting

confidence: 90%

Section: Methods and Model To Measure The Color Excessmentioning

confidence: 99%

Section: Contamination By Agb Stars and Ysosmentioning

confidence: 99%

Section: Contamination By Agb Stars and Ysosmentioning

confidence: 99%

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Extinction and dust/gas ratio in LMC molecular clouds

Dobashi

Bernard

Hughes

et al. 2008

A&A

125

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“…Some investigators (e.g. Tsalmantza et al 2006) have focussed their attention on identifying carbon stars on the basis of the red J − K s tail (see Figs. 1, 4, 6 and 9 in Tsalmantza et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Keck spectroscopy and Spitzer space telescope analysis of the outer disk of the Triangulum spiral galaxy M 33

Block

Combes

Puerari

et al. 2007

A&A

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In an earlier study of the spiral galaxy M 33, we photometrically identified arcs or outer spiral arms of intermediate age (0.6−2 Gyr) carbon stars precisely at the commencement of the HI-warp. Stars in the arcs were unresolved, but were likely thermally-pulsing asymptotic giant branch carbon stars. Here we present Keck I spectroscopy of seven intrinsically bright and red target stars in the outer, northern arc in M 33. The target stars have estimated visual magnitudes as faint as V ∼ 25 m . Absorption bands of CN are seen in all seven spectra reported here, confirming their carbon star status. In addition, we present Keck II spectra of a small area 0.5 degree away from the centre of M 33; the target stars there are also identified as carbon stars. We also study the non-stellar PAH dust morphology of M 33 secured using IRAC on board the Spitzer Space Telescope. The Spitzer 8 µm image attests to a change of spiral phase at the start of the HI warp. The Keck spectra confirm that carbon stars may safely be identified on the basis of their red J − K s colours in the outer, low metallicity disk of M 33. We propose that the enhanced number of carbon stars in the outer arms are an indicator of recent star formation, fueled by gas accretion from the HI-warp reservoir.

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Virtual Observatory for stellar astronomy

Malkov

Zolotukhin

2013

Astron Nachr

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The principal idea of the Virtual Observatory is to achieve real transparency for astronomical data, similar to transparency for all the world's documents in the World Wide Web. In the Virtual Observatory, all the world's astronomical data is available from one's desktop. All archives understand the same query language, can be accessed through a uniform interface, and diverse data can be analyzed with the same tools. In particular, facilities of the Virtual Observatory allow users to make a fast and correct analysis of objects from various surveys. It yields multi‐photometry data on registered objects and makes it possible to determine stellar parameters. Methods of astronomical data analysis as well as their application to various areas of stellar astronomy are discussed in this paper. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Luminous AGB stars in nearby galaxies

Cited by 12 publications

References 32 publications

Extinction and dust/gas ratio in LMC molecular clouds

Extinction and dust/gas ratio in LMC molecular clouds

Keck spectroscopy and Spitzer space telescope analysis of the outer disk of the Triangulum spiral galaxy M 33

Virtual Observatory for stellar astronomy

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