A DECam View of the Diffuse Dwarf Galaxy Crater II: Variable Stars. (arXiv:1912.00081v1 [astro-ph.GA])

A DECam View of the Diffuse Dwarf Galaxy Crater II: Variable Stars. (arXiv:1912.00081v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Vivas_A/0/1/0/all/0/1">A. Katherina Vivas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walker_A/0/1/0/all/0/1">Alistair R. Walker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martinez_Vazquez_C/0/1/0/all/0/1">Clara E. Mart&#xed;nez-V&#xe1;zquez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Monelli_M/0/1/0/all/0/1">Matteo Monelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bono_G/0/1/0/all/0/1">Giuseppe Bono</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dorta_A/0/1/0/all/0/1">Antonio Dorta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nidever_D/0/1/0/all/0/1">David L. Nidever</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fiorentino_G/0/1/0/all/0/1">Giuliana Fiorentino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gallart_C/0/1/0/all/0/1">Carme Gallart</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Andreuzzi_G/0/1/0/all/0/1">Gloria Andreuzzi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Braga_V/0/1/0/all/0/1">Vittorio F. Braga</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DallOra_M/0/1/0/all/0/1">Massimo Dall&#x27;Ora</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Olsen_K/0/1/0/all/0/1">Knut Olsen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stetson_P/0/1/0/all/0/1">Peter B. Stetson</a>

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
$(m-M)_0=20.333pm 0.004$ (stat) $pm 0.07$ (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 $153^circ$. 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.

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
$(m-M)_0=20.333pm 0.004$ (stat) $pm 0.07$ (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 $153^circ$. 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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