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  1. OA@INAF
  2. PRODOTTI RICERCA INAF
  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
  4. 1.01 Articoli in rivista
Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/23388
Title: Variable Stars and Stellar Populations in Andromeda XXI. II. Another Merged Galaxy Satellite of M31?
Authors: CUSANO, FELICE 
GAROFALO, Alessia 
CLEMENTINI, Gisella 
Cignoni, Michele
FEDERICI, Luciana
MARCONI, Marcella 
MUSELLA, ILARIA 
RIPEPI, Vincenzo 
SPEZIALI, Roberto 
Sani, Eleonora
MERIGHI, Roberto 
Issue Date: 2015
Journal: THE ASTROPHYSICAL JOURNAL 
Number: 806
Issue: 2
First Page: 200
Abstract: B and V time-series photometry of the M31 dwarf spheroidal satellite Andromeda XXI (And XXI) was obtained with the Large Binocular Cameras at the Large Binocular Telescope. We have identified 50 variables in And XXI, of which 41 are RR Lyrae stars (37 fundamental-mode—RRab, and 4 first-overtone-RRc, pulsators) and 9 are Anomalous Cepheids (ACs). The average period of the RRab stars (< {P}<SUB>{ab</SUB>}> =0.64 days) and the period-amplitude diagram place And XXI in the class of Oosterhoff II—Oosterhoff-Intermediate objects. From the average luminosity of the RR Lyrae stars we derived the galaxy distance modulus of (m - M)<SUB>0</SUB> = 24.40 ± 0.17 mag, which is smaller than previous literature estimates, although still consistent with them within 1σ. The galaxy color-magnitude diagram shows evidence for the presence of three different stellar generations in And XXI: (1) an old (̃12 Gyr) and metal-poor ([Fe/H] = -1.7 dex) component traced by the RR Lyrae stars; (2) a slightly younger (10-6 Gyr) and more metal-rich ([Fe/H] = -1.5 dex) component populating the red horizontal branch, and (3) an intermediate age (̃1 Gyr) component with the same metallicity that produced the ACs. Finally, we provide hints that And XXI could be the result of a minor merging event between two dwarf galaxies. <P />Based on data collected with the LBC at the LBT.
Acknowledgments: We warmly thank P. Montegriffo for the development and maintenance of the GRATIS software, G. Battaglia for providing the software to compute And XXI’s density maps, and A. Veropalumbo for software assistance. Financial support for this research was provided by PRIN INAF 2010 (PI: G. Clementini) and by Premiale LBT 2013. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia. We acknowledge the support from the LBT-Italian Coordination Facility for the execution of observations, data distribution, and reduction. Facility: LBT
URI: http://hdl.handle.net/20.500.12386/23388
URL: https://iopscience.iop.org/article/10.1088/0004-637X/806/2/200
ISSN: 0004-637X
DOI: 10.1088/0004-637X/806/2/200
Bibcode ADS: 2015ApJ...806..200C
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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