Using classical cepheids to study the far side of the Milky Way disk
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Fecha
2020-08
Profesor/a Guía
Facultad/escuela
Idioma
en
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Editor
EDP Sciences
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Licencia CC
Atribution 4.0 International (CC BY 4.0)
Licencia CC
https://creativecommons.org/licenses/by/4.0/deed.es
Resumen
Context. Much of what we know about the Milky Way disk is based on studies of the solar vicinity. The structure, kinematics, and
chemical composition of the far side of the Galactic disk, beyond the bulge, are still to be revealed.
Aims. Classical Cepheids (CCs) are young and luminous standard candles. We aim to use a well-characterized sample of these variable
stars to study the present-time properties of the far side of the Galactic disk.
Methods. A sample of 45 Cepheid variable star candidates were selected from near-infrared time series photometry obtained by the
VVV survey. We characterized this sample using high quality near-infrared spectra obtained with VLT/X-shooter. The spectroscopic
data was used to derive radial velocities and iron abundances for all the sample Cepheids. This allowed us to separate the CCs, which
are metal rich and with kinematics consistent with the disk rotation, from type II Cepheids (T2Cs), which are more metal poor and
with different kinematics.
Results. We estimated individual distances and extinctions using VVV photometry and period-luminosity relations, reporting the
characterization of 30 CCs located on the far side of the Galactic disk, plus 8 T2Cs mainly located in the bulge region, of which 10
CCs and 4 T2Cs are new discoveries. The remaining seven stars are probably misclassified foreground ellipsoidal binaries. This is the
first sizeable sample of CCs in this distant region of our Galaxy that has been spectroscopically confirmed. We use their positions,
kinematics, and metallicities to confirm that the general properties of the far disk are similar to those of the well-studied disk on the
solar side of the Galaxy. In addition, we derive for the first time the radial metallicity gradient on the disk’s far side. Considering
all the CCs with RGC < 17 kpc, we measure a gradient with a slope of −0.062 dex kpc−1
and an intercept of +0.59 dex, which is in
agreement with previous determinations based on CCs on the near side of the disk.
Notas
Indexación: Scopus.
Palabras clave
Galaxy: Structure, Galaxy: Disk, Stars: Variables: Cepheids, Infrared: Stars
Citación
Astronomy and Astrophysics. Volume 640. 1 August 2020. Article number A92
DOI
DOI: 10.1051/0004-6361/202037575