Journal article
On the correlation between metallicity and the X-shaped morphology of the Milky Way bulge
Monthly notices of the Royal Astronomical Society, Vol.442(3), pp.2075-2080
08/11/2014
DOI: 10.1093/mnras/stu805
Abstract
We demonstrate that failure to properly account for stellar evolution can bias results in determinations of the spatial morphology of Galactic bulge stars, focusing on the question of whether or not the X-shape is more pronounced among the more metal-rich stars than among the metal-poor stars. We argue that this trend, a result recently claimed by three separate groups, may have been overestimated as it is relatively easier to detect a bimodality in the distance distribution function at higher metallicities. This is due to three factors. First, the intrinsic colour of red clump and red giant stars varies with metallicity, at the level d(V - I)(RC)/d[M/H] a parts per thousand 0.25 mag dex(-1), and thus the ratio of red clump to red giant stars within a spectroscopic sample will depend on the photometric selection of any investigation. Secondly, the duration of ascent of the red giant branch goes down and the red clump lifetime goes up as metallicity increases, which has the effect of increasing the ratio of red clump to red giant stars by as much as similar to 33 per cent over the range of the bulge metallicity distribution function. Finally, over the same metallicity interval, the effective number of red giant branch bump stars is predicted to increase by similar to 200 per cent, and their presence becomes degenerate with the observational parameters of the two red clumps, creating an illusory increase in signal to noise for a second peak in the distance modulus distribution.
Details
- Title: Subtitle
- On the correlation between metallicity and the X-shaped morphology of the Milky Way bulge
- Creators
- D. M. Nataf - Australian National UniversityS. Cassisi - National Institute for AstrophysicsE. Athanassoula - Aix-Marseille Université
- Resource Type
- Journal article
- Publication Details
- Monthly notices of the Royal Astronomical Society, Vol.442(3), pp.2075-2080
- Publisher
- Oxford Univ Press
- DOI
- 10.1093/mnras/stu805
- ISSN
- 0035-8711
- eISSN
- 1365-2966
- Number of pages
- 6
- Grant note
- prot. 2010LY5N2T / PRIN MIUR; Ministry of Education, Universities and Research (MIUR); Research Projects of National Relevance (PRIN) PITN-GA-2011-289313 / People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/under REA 2013 - x2013047098; 2014 - x2014047098 / GENCI - TGCC/CINES FL110100012 / Australian Research Council PRIN-INAF; Istituto Nazionale Astrofisica (INAF); Ministry of Education, Universities and Research (MIUR); Research Projects of National Relevance (PRIN) CNES (Centre National d'Etudes Spatiales - France); Centre National D'etudes Spatiales
- Language
- English
- Date published
- 08/11/2014
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701833902771
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