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SMHASH: a new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor

Garofalo, Alessia and Scowcroft, Victoria and Clementini, Gisella and Johnston, Kathryn V. and Cohen, Judith G. and Freedman, Wendy L. and Madore, Barry F. and Majewski, Steven R. and Monson, Andrew J. and Neeley, Jillian R. and Grillmair, Carl J. and Hendel, David and Kallivayalil, Nitya and Marengo, Massimo and van der Marel, Roeland (2018) SMHASH: a new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor. Monthly Notices of the Royal Astronomical Society, 481 (1). pp. 578-595. ISSN 0035-8711. doi:10.1093/mnras/sty2222.

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We present a new distance estimation for the Milky Way dwarf spheroidal satellite Sculptor obtained from multi-epoch mid-infrared observations of RR Lyrae stars (RRLs). The 3.6 μm observations have been acquired with the Infrared Array Camera onboard the Spitzer Space Telescope as part of the SMHASH program. Mid-infrared light curves for 42 RRLs were obtained, from which we measured Sculptor’s distance modulus to be μ = 19.60 ± 0.02 (statistical) ± 0.04 (photometric) mag (with σ_(sys) = 0.09 mag), using the 3.6 μm empirical period–luminosity relations derived from the Galactic globular cluster M4, or μ = 19.57 ± 0.02 (statistical) ± 0.04 (photometric) mag (with σ_(sys) = 0.11 mag) using empirical relations in the same passband recently derived from the Large Magellanic Cloud globular cluster Reticulum. Both these measurements are in good agreement with values presented in previous works with Sculptor RRLs in optical bands, and are also consistent with recent near-infrared RR Lyrae results. Best agreement with the literature is found for the latter modulus which is equivalent to a distance of d = 82 ± 1 (statistical) ± 2 (photometric) kpc (with σ_(sys) = 4 kpc). Finally, using a subsample of RRLs with spectroscopic metallicities, we demonstrate that these distance estimates are not affected by metallicity effects.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Scowcroft, Victoria0000-0001-8829-4653
Johnston, Kathryn V.0000-0001-6244-6727
Cohen, Judith G.0000-0002-8039-4673
Freedman, Wendy L.0000-0003-3431-9135
Madore, Barry F.0000-0002-1576-1676
Majewski, Steven R.0000-0003-2025-3147
Monson, Andrew J.0000-0002-0048-2586
Grillmair, Carl J.0000-0003-4072-169X
Hendel, David0000-0002-7939-7607
Marengo, Massimo0000-0001-9910-9230
van der Marel, Roeland0000-0001-7827-7825
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 August 9. Received 2018 August 9; in original form 2018 May 31. Published: 16 August 2018. We thank an anonymous referee for comments and suggestions that helped to improve the manuscript. We thank Stijn Wuyts for his help with this manuscript. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration and data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Support to this study has been provided by PRIN-INAF2014, ‘EXCALIBUR’S’ (P.I. G. Clementini) and by Premiale 2015, ‘MITiC’ (P.I. B. Garilli). GC thanks the Carnegie Observatories visitor program for support as a science visitor. AG thanks Felice Cusano for useful discussions and Vincenzo Ripepi for help with the selection and preparation of the finding chart for the Spitzer observations of the RRL used in this study.
Group:Infrared Processing and Analysis Center (IPAC), Astronomy Department
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)PRIN-INAF 2014
Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR)Premiale 2015
Subject Keywords:techniques: photometric – stars: distances – stars: variables: RR Lyrae – galaxies: individual (Sculptor) – galaxies: dwarf, Milky Way
Issue or Number:1
Record Number:CaltechAUTHORS:20181130-091853410
Persistent URL:
Official Citation:Alessia Garofalo, Victoria Scowcroft, Gisella Clementini, Kathryn V Johnston, Judith G Cohen, Wendy L Freedman, Barry F Madore, Steven R Majewski, Andrew J Monson, Jillian R Neeley, Carl J Grillmair, David Hendel, Nitya Kallivayalil, Massimo Marengo, Roeland van der Marel; SMHASH: a new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor, Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 1, 21 November 2018, Pages 578–595,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91352
Deposited By: Tony Diaz
Deposited On:30 Nov 2018 17:38
Last Modified:16 Nov 2021 03:40

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