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Zwicky Transient Facility and Globular Clusters: The Period-Luminosity and Period-Wesenheit Relations for Type II Cepheids

Ngeow, Chow-Choong and Bhardwaj, Anupam and Henderson, Jing-Yi and Graham, Matthew J. and Laher, Russ R. and Medford, Michael S. and Purdum, Josiah N. and Rusholme, Ben (2022) Zwicky Transient Facility and Globular Clusters: The Period-Luminosity and Period-Wesenheit Relations for Type II Cepheids. Astronomical Journal, 164 (4). Art. No. 154. ISSN 0004-6256. doi:10.3847/1538-3881/ac87a4.

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We present the first gri-band period–luminosity (PL) and period–Wesenheit (PW) relations for 37 Type II Cepheids (TIICs) located in 18 globular clusters based on photometric data from the Zwicky Transient Facility. We also updated BVIJHK-band absolute magnitudes for 58 TIICs in 24 globular clusters using the latest homogeneous distances to the globular clusters. The slopes of g/r/i- and B/V/I-band PL relations are found to be statistically consistent when using the same sample of distance and reddening. We employed the calibration of ri-band PL/PW relations in globular clusters to estimate a distance to M31 based on a sample of ∼270 TIICs from the PAndromeda project. The distance modulus to M31, obtained using calibrated ri-band PW relation, agrees well with the recent determination based on classical Cepheids. However, distance moduli derived using the calibrated r- and i-band PL relations are systematically smaller by ∼0.2 mag, suggesting there are possible additional systematic errors on the PL relations. Finally, we also derive the period–color (PC) relations and for the first time the period–Q-index (PQ) relations, where the Q-index is reddening free, for our sample of TIICs. The PC relations based on (r − i) and near-infrared colors and the PQ relations are found to be relatively independent of the pulsation periods.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ngeow, Chow-Choong0000-0001-8771-7554
Bhardwaj, Anupam0000-0001-6147-3360
Graham, Matthew J.0000-0002-3168-0139
Laher, Russ R.0000-0003-2451-5482
Medford, Michael S.0000-0002-7226-0659
Purdum, Josiah N.0000-0003-1227-3738
Rusholme, Ben0000-0001-7648-4142
Additional Information:We are thankful for the useful discussions and comments from an anonymous referee that improved the manuscript. We are thankful for funding from the Ministry of Science and Technology (Taiwan) under the contracts 107-2119-M-008-014-MY2, 107-2119-M-008-012, 108-2628-M-007-005-RSP, and 109-2112-M-008-014-MY3. A.B. acknowledges funding from the European Unions Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 886298. Based on observations obtained with the Samuel Oschin Telescope 48 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grant Nos. AST-1440341 and AST-2034437 and a collaboration including current partners Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. This research has made use of the SIMBAD database and the VizieR catalog access tool, operated at CDS, Strasbourg, France. This research made use of Astropy (, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013, 2018).
Group:Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Ministry of Science and Technology (Taipei)107-2119-M-008-014-MY2
Ministry of Science and Technology (Taipei)107-2119-M-008-012
Ministry of Science and Technology (Taipei)108-2628-M-007-005-RSP
Ministry of Science and Technology (Taipei)109-2112-M-008-014-MY3
Marie Curie Fellowship886298
ZTF partner institutionsUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20221003-756400000.9
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117203
Deposited By: Melissa Ray
Deposited On:04 Oct 2022 22:20
Last Modified:04 Oct 2022 22:20

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