Abstract
Abstract With the increasing number of large stellar survey projects, the quality and quantity of excellent tracers for studying the Milky Way are rapidly growing, one of which is the classical Cepheids. Classical Cepheids are high-precision standard candles with very low typical uncertainties (<3%) available via the mid-infrared period–luminosity relation. About 3500 classical Cepheids identified from the Optical Gravitational Lensing Experiment, All-Sky Automated Survey for Supernova, Gaia, Wide-field Infrared Survey Explorer, and Zwicky Transient Facility survey data have been analyzed in this work, and their spatial distributions show a clear signature of Galactic warp. Two kinematical methods are adopted to measure the Galactic rotation curve (RC) in the Galactocentric distance range of . Gently declining RCs are derived by both the proper motion (PM) method and three-dimensional velocity vector (3DV) method. The largest sample of classical Cepheids with the most accurate 6D phase-space coordinates available to date are modeled in the 3DV method, and the resulting RC is found to decline at the relatively smaller gradient of (−1.33 ± 0.1) . Comparing to results from the PM method, a higher rotation velocity ((232.5 ± 0.83) ) is derived at the position of the Sun in the 3DV method. The virial mass and local dark matter density are estimated from the 3DV method, which is the more reliable method, and GeV, respectively.
Highlights
The mass distribution and dark matter density profiles of the Milky Way are not just key probes of its assembly history (e.g., Lake 1989; Read et al 2008; Deason, Belokurov & Sanders 2019), and provide crucial clues for the cosmological context of galaxy formation (e.g., Dubinski 1994; Ibata et al 2001; Lux et al 2012)
We collected our sample from several classical Cepheid catalogs as follows: the AllSky Automated Survey for Supernovae (ASAS-SN) Variable stars catalog (Shappee et al 2014; Jayasinghe et al 2018), the classical Cepheids sample by Skowron et al (2019a, b) basically from the Optical Gravitational Lensing Experiment (OGLE) (Udalski et al 2015; Udalski et al 2018), classical Cepheids from the European Space Agency (ESA) mission Gaia (Gaia Collaboration 2016, 2018; Ripepi et al 2019), and the classical Cepheids catalog by Chen et al(2019) from the Wide-field Infrared Survey Explorer (WISE) (Wright et al 2010)
We have analyzed 3483 classical Cepheids selected from thousands of classical Cepheids identified by several survey projects (e.g., OGLE, ASAS-SN, Gaia, WISE and Zwicky Transient Facility (ZTF)), and constructed the rotation velocity distribution of the Milky Way between the Galactocentric distance 4 kpc and 19 kpc by using two different methods
Summary
The mass distribution and dark matter density profiles of the Milky Way are not just key probes of its assembly history (e.g., Lake 1989; Read et al 2008; Deason, Belokurov & Sanders 2019), and provide crucial clues for the cosmological context of galaxy formation (e.g., Dubinski 1994; Ibata et al 2001; Lux et al 2012). Mroz et al (2019) tracked the RC from the 6D phase-space information of 773 classical Cepheids, and they found a relatively flat rotation curve They did not estimate mass distribution and dark matter content of the Milky Way. In this work, we have selected and analyzed about 3500 classical Cepheids which have precise distances and measured the Milky way rotation curve using the proper motion method (Gnacinski 2019) and 3D velocity vector method (Reid et al 2009).
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