A Very Metal-poor RR Lyrae Star with a Disk Orbit Found in the Solar Neighborhood

Matsunaga, Noriyuki; Itane, Akinori; Hattori, Kohei; Crestani, Juliana; Braga, V. F.; Bono, G.; Taniguchi, Daisuke; Baba, Junichi; Maehara, Hiroyuki; Ukita, Nobuharu; Sakamoto, T.; Kobayashi, Naoto; Aoki, Tsutomu; Soyano, Takao; Tarusawa, K.; Sarugaku, Yuki; Mito, Hiroyuki; Sako, Shigeyuki; Doi, M.; Nakada, Y.; Izumi, Natsuko; Ita, Yoshifusa; Onozato, Hiroki; Jian, Mingjie; Kondo, Sohei; Yasui, Chikako; Tsujimoto, Takuji; Otsubo, Shogo; Ikeda, Yuji; Kawakita, Hideyo

doi:10.3847/1538-4357/ac3483

Cited by 4 publications

(2 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Combining these photometric data with the PLR, we determined the distance and the foreground extinction of each Cepheid. The same analysis, but for an RR Lyr variable with different PLR, was detailed in Matsunaga et al (2022). Then we checked that the obtained distances are consistent with the parallax-based distances obtained by Bailer-Jones et al (2021).…”

Section: Targetsmentioning

confidence: 76%

Metallicities of Classical Cepheids in the Inner Galactic Disk

Matsunaga,

Taniguchi,

Elgueta

et al. 2023

ApJ

Self Cite

View full text Add to dashboard Cite

Metallicity gradients refer to the sloped radial profiles of the metallicities of gas and stars and are commonly seen in disk galaxies. A well-defined metallicity gradient of the Galactic disk is observed particularly well with classical Cepheids, which are good stellar tracers thanks to their period–luminosity relation, allowing precise distance estimation and other advantages. However, the measurement of the inner-disk gradient has been impeded by the incompleteness of previous samples of Cepheids and the limitations of optical spectroscopy in observing highly reddened objects. Here we report the metallicities of 16 Cepheids measured with high-resolution spectra in the near-infrared YJ bands. These Cepheids are located at 3–5.6 kpc in Galactocentric distance, R GC, and reveal the metallicity gradient in this range for the first time. Their metallicities are mostly between 0.1 and 0.3 dex in [Fe/H] and more or less follow the extrapolation of the metallicity gradient found in the outer part, R GC > 6.5 kpc. The gradient in the inner disk may be shallower or even flat, but the small sample does not allow the determination of the slope precisely. More extensive spectroscopic observations would also be necessary for studying minor populations, if any, with higher or lower metallicities that were reported in previous literature. In addition, the 3D velocities of our inner-disk Cepheids show a kinematic pattern that indicates noncircular orbits caused by the Galactic bar, which is consistent with the patterns reported in recent studies on high-mass star-forming regions and red giant branch stars.

show abstract

Section: Targetsmentioning

confidence: 76%

Metallicities of Classical Cepheids in the Inner Galactic Disk

Matsunaga,

Taniguchi,

Elgueta

et al. 2023

ApJ

Self Cite

View full text Add to dashboard Cite

show abstract

“…The high throughput and resolution of WINERED have advanced the observational studies of various astronomical objects: metallicities and chemical abundances of various types of stars (D'Orazi et al 2018;Kondo et al 2019;Jian et al 2020;Fukue et al 2021;Taniguchi et al 2021;Matsunaga et al 2022Matsunaga et al , 2023, the diffuse interstellar bands and interstellar molecules (Hamano et al 2019(Hamano et al , 2022, young stellar objects (Yasui et al 2019), AGN (Mizumoto et al 2024), luminous blue variable stars (Mizumoto et al 2018), quasars (Sameshima et al 2020) and comets (Shinnaka et al 2017).…”

Section: Instrument Overviewmentioning

confidence: 99%

WARP: The Data Reduction Pipeline for the WINERED Spectrograph

Hamano,

Ikeda,

Otsubo

et al. 2024

PASP

Self Cite

View full text Add to dashboard Cite

We present a data reduction pipeline written in Python for data obtained with the near-infrared cross-dispersed echelle spectrograph, WINERED, which yields a 0.91–1.35 μm spectrum with the resolving power of R max ≡ λ / Δ λ = 28,000 or 70,000 depending on the observing mode. The pipeline was developed to efficiently extract the spectrum from the raw data with high quality. It comprises two modes: the calibration and the science mode. The calibration mode automatically produces the flat-fielding image, bad pixel map, echellogram distortion map and the dispersion solution from the set of the calibration data. Using calibration images and parameters, the science data of astronomical objects can be reduced automatically using the science mode. The science mode is also used for the real-time quick look at the data during observations. An example of the spectra reduced with WARP is presented. The effect of the highly inclined slit image on the spectral resolution is discussed.

show abstract

Discovery of the local counterpart of disc galaxies at z > 4: The oldest thin disc of the Milky Way usingGaia-RVS

Nepal,

Chiappini,

Queiroz

et al. 2024

A&A

View full text Add to dashboard Cite

JWST recently detected numerous disc galaxies at high redshifts, and there have been observations of cold disc galaxies at z > 4 with ALMA. In the Milky Way (MW), recent studies highlight the presence of metal-poor stars in cold-disc orbits, suggesting an ancient disc. This prompts two fundamental questions. The first refers to the time of formation of the MW disc, and the second to whether it originated as the thin disc or the larger velocity dispersion thick disc. We carried out a chrono-chemo-dynamical study of a large sample of stars with precise stellar parameters, focusing on the oldest stars in order to decipher the assembly history of the MW discs. We investigated a sample of 565\,606 stars with 6D phase space information and high-quality stellar parameters coming from the hybrid-CNN analysis of the Gaia -DR3 RVS stars. The sample contains 8\,500 stars with For a subset of sim 200\,000 main sequence turn-off (MSTO) and subgiant branch (SGB) stars, we computed distances and ages using the StarHorse code, with a mean precision of 1<!PCT!> and 12<!PCT!>, respectively. First, we confirm the existence of metal-poor stars in thin-disc orbits. The majority of these stars are predominantly old ($>$10 Gyr), with over 50<!PCT!> being older than 13 Gyr. Second, we report the discovery of the oldest thin disc of the Milky Way, which extends across a wide range of metallicities, from metal-poor to super-solar stars. The metal-poor stars in disc orbits manifest as a readily visible tail of the metallicity distribution. We calculate the vertical velocity dispersion ($ V_z $) for the high- thick disc, finding 35 pm 0.6 while the thin disc within the same age range has a $ V_z $ that is lower by 10 to 15 Our old thin disc $ V_z $ appears similar to those estimated for the high-z disc galaxies. Third, as a verification of StarHorse ages, we extend the Y/Mg chemical clock to the oldest ages and estimate a slope of $-$0.038\,$ dex $. Finally, we confirm our discovery of the old thin disc by showing that the `splash' population includes high- and low- populations that are both old, and extends to a wider range, reaching supersolar We find that about 6<!PCT!>\ to 10<!PCT!> of the old thin disc was heated to thick-disc orbits. The youngest `splashed' stars appear at 9 to 10 Gyr and may suggest a Gaia-Sausage/Enceladus (GSE) merger at this period. The Milky Way thin disc formed less than 1 billion years after the Big Bang and continuously built up in an inside-out manner ---this finding precedes the earlier estimates of the time at which the MW thin disc began to form (around 8-9 Gyr) by about 4-5 billion years. We find that the metal-poor stars in disc orbits reported by previous studies belong to this old thin disc. Considering a massive merger event such as the GSE, a splash is expected ---we find a portion of the old thin disc is heated to thick disc velocities and the splash extends to supersolar regimes.

show abstract

A Very Metal-poor RR Lyrae Star with a Disk Orbit Found in the Solar Neighborhood

Cited by 4 publications

References 73 publications

Metallicities of Classical Cepheids in the Inner Galactic Disk

Metallicities of Classical Cepheids in the Inner Galactic Disk

WARP: The Data Reduction Pipeline for the WINERED Spectrograph

Discovery of the local counterpart of disc galaxies at z > 4: The oldest thin disc of the Milky Way usingGaia-RVS

Contact Info

Product

Resources

About