RR Lyrae Variables in the Crater II Dwarf Galaxy

Joo, Seok-Joo; Kyeong, Jaemann; Yang, Soung-Chul; Han, Sang-Il; Sung, Eon‐Chang; Kim, Dong-Won; Jeong, Hyunjin; Ree, Chang H.; Rey, Soo-Chang; Jerjen, Helmut; Kim, Hak-Sub; Cha, Sang-Monk; Lee, Yongseok

doi:10.3847/1538-4357/aac4a3

Cited by 16 publications

(22 citation statements)

References 146 publications

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“…We classified 130 periodic variables, of which 103 are RR Lyrae stars, 7 are anomalous Cepheids, 6 are dwarf Cepheids, and 14 are eclipsing binaries of different types. This means an increase of 36 periodic variables with respect to the findings by Joo et al (2018). Although the majority of the variable stars seem to be associated with Crater II based on their location in the CMD, there are some stars that most likely belong to the field foreground population.…”

Section: Variable Star Classificationmentioning

confidence: 74%

“…We recovered 94 out of 97 stars in Joo et al (2018). The three stars that were not recovered are V24, V79 and V96, which are all outside our footprint.…”

Section: Variable Star Classificationmentioning

confidence: 93%

“…In section § 4, we discuss the characteristics of the RR Lyrae stars identified in this work. We compare with the previous findings of Joo et al (2018) and Monelli et al (2018), discuss the Bailey Diagram, derive a robust distance to Crater II, and examine the spatial distribution and radial trends of the RR Lyrae stars within the galaxy. The population of anomalous Cepheids in Crater II is discussed in § 5.…”

Section: Introductionmentioning

confidence: 88%

“…The three stars that were not recovered are V24, V79 and V96, which are all outside our footprint. The last 2 are classified by Joo et al (2018) as field RR Lyrae stars of the type ab. V24 would be the only Crater II RR Lyrae star not in our data.…”

Section: Variable Star Classificationmentioning

confidence: 99%

“…V24 would be the only Crater II RR Lyrae star not in our data. We list all variables in Table 1 using the ID convention followed by Joo et al (2018) and Monelli et al (2018). Our periods and classification may differ from those in previous works for some stars.…”

Section: Variable Star Classificationmentioning

confidence: 99%

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A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

Vivas

Walker

Martı́nez-Vázquez

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Time series observations of a single dithered field centered on the diffuse dwarf satellite galaxy Crater II were obtained with the Dark Energy Camera (DECam) at the 4m Blanco Telescope at Cerro Tololo Inter-American Observatory, Chile, uniformly covering up to two half-light radii. Analysis of the g and i time series results in the identification and characterization of 130 periodic variable stars, including 98 RR Lyrae stars, 7 anomalous Cepheids, and 1 SX Phoenicis star belonging to the Crater II population, and 24 foreground variables of different types. Using the large number of ab-type RR Lyrae stars present in the galaxy, we obtained a distance modulus to Crater II of (m − M) 0 = 20.333 ± 0.004 (stat) ±0.07 (sys). The distribution of the RR Lyrae stars suggests an elliptical shape for Crater II, with an ellipticity of 0.24 and a position angle of 153 • . From the RR Lyrae stars we infer a small metallicity dispersion for the old population of Crater II of only 0.17 dex. There are hints that the most metal-poor stars in that narrow distribution have a wider distribution across the galaxy, while the slightly more metal rich part of the population is more centrally concentrated. Given the features in the color-magnitude diagram of Crater II, the anomalous Cepheids in this galaxy must have formed through a binary evolution channel of an old population.

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Section: Variable Star Classificationmentioning

confidence: 74%

“…We recovered 94 out of 97 stars in Joo et al (2018). The three stars that were not recovered are V24, V79 and V96, which are all outside our footprint.…”

Section: Variable Star Classificationmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 88%

Section: Variable Star Classificationmentioning

confidence: 99%

Section: Variable Star Classificationmentioning

confidence: 99%

See 3 more Smart Citations

A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

Vivas

Walker

Martı́nez-Vázquez

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Gaia DR2 proper motions of dwarf galaxies within 420 kpc

Fritz

Battaglia

Pawlowski

et al. 2018

A&A

308

415

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A proper understanding of the Milky Way (MW) dwarf galaxies in a cosmological context requires knowledge of their 3D velocities and orbits. However, proper motion (PM) measurements have generally been of limited accuracy and are available only for more massive dwarfs. We therefore present a new study of the kinematics of the MW dwarf galaxies. We use the Gaia DR2 for those dwarfs that have been spectroscopically observed in the literature. We derive systemic PMs for 39 galaxies and galaxy candidates out to 420 kpc, and generally find good consistency for the subset with measurements available from other studies. We derive the implied Galactocentric velocities, and calculate orbits in canonical MW halo potentials of low (0.8 × 10 12 M ) and high mass (1.6 × 10 12 M ). Comparison of the distributions of orbital apocenters and 3D velocities to the halo virial radius and escape velocity, respectively, suggests that the satellite kinematics are best explained in the high-mass halo. Tuc III, Crater II, and additional candidates have orbital pericenters small enough to imply significant tidal influences. Relevant to the missing satellite problem, the fact that fewer galaxies are observed to be near apocenter than near pericenter implies that there must be a population of distant dwarf galaxies yet to be discovered. Of the 39 dwarfs: 12 have orbital poles that do not align with the MW plane of satellites (given reasonable assumptions about its intrinsic thickness); 10 have insufficient PM accuracy to establish whether they align; and 17 satellites align, of which 11 are co-orbiting and (somewhat surprisingly, in view of prior knowledge) 6 are counter-orbiting. Group infall might have contributed to this, but no definitive association is found for the members of the Crater-Leo group.

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The mass of our Galaxy from satellite proper motions in the Gaia era

Fritz

Cintio

Battaglia

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We use Gaia DR2 systemic proper motions of 45 satellite galaxies to constrain the mass of the Milky Way using the scale free mass estimator of Watkins et al. (2010). We first determine the anisotropy parameter β, and the tracer satellites' radial density index γ to be β=−0.67 +0.45 −0.62 and γ = 2.11 ± 0.23. When we exclude possible former satellites of the Large Magellanic Cloud, the anisotropy changes to β=−0.21 +0.37 −0.51 . We find that the index of the Milky Way's gravitational potential α, which is dependent on the mass itself, is the parameter with the largest impact on the mass determination. Via comparison with cosmological simulations of Milky Way-like galaxies, we carried out a detailed analysis of the estimation of the observational uncertainties and their impact on the mass estimator. We found that the mass estimator is biased when applied naively to the satellites of simulated Milky Way halos. Correcting for this bias, we obtain for our Galaxy a mass of 0.58 +0.15 −0.14 × 10 12 M ⊙ within 64 kpc, as computed from the inner half of our observational sample, and 1.43 +0.35 −0.32 ×10 12 M ⊙ within 273 kpc, from the full sample; this latter value extrapolates to a virial mass of M vir =1.51 +0.45 −0.40 ×10 12 M ⊙ corresponding to a virial radius of R vir =308±29 kpc. This value of the Milky Way mass lies in-between other mass estimates reported in the literature, from various different methods.

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RR Lyrae Variables in the Crater II Dwarf Galaxy

Cited by 16 publications

References 146 publications

A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

Gaia DR2 proper motions of dwarf galaxies within 420 kpc

The mass of our Galaxy from satellite proper motions in the Gaia era

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