Metallicities of Classical Cepheids in the Inner Galactic Disk
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 perio...
| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/aced93 |
| _version_ | 1797690496337838080 |
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| author | Noriyuki Matsunaga Daisuke Taniguchi Scarlet S. Elgueta Takuji Tsujimoto Junichi Baba Andrew McWilliam Shogo Otsubo Yuki Sarugaku Tomomi Takeuchi Haruki Katoh Satoshi Hamano Yuji Ikeda Hideyo Kawakita Charlie Hull Rogelio Albarracín Giuseppe Bono Valentina D’Orazi |
| author_facet | Noriyuki Matsunaga Daisuke Taniguchi Scarlet S. Elgueta Takuji Tsujimoto Junichi Baba Andrew McWilliam Shogo Otsubo Yuki Sarugaku Tomomi Takeuchi Haruki Katoh Satoshi Hamano Yuji Ikeda Hideyo Kawakita Charlie Hull Rogelio Albarracín Giuseppe Bono Valentina D’Orazi |
| author_sort | Noriyuki Matsunaga |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-03-12T02:01:25Z |
| format | Article |
| id | doaj.art-920880fa2faf46028611c25cf0c6fb10 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T02:01:25Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-920880fa2faf46028611c25cf0c6fb102023-09-07T15:59:37ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01954219810.3847/1538-4357/aced93Metallicities of Classical Cepheids in the Inner Galactic DiskNoriyuki Matsunaga0Daisuke Taniguchi1https://orcid.org/0000-0002-2861-4069Scarlet S. Elgueta2https://orcid.org/0000-0001-5642-2569Takuji Tsujimoto3https://orcid.org/0000-0002-9397-3658Junichi Baba4https://orcid.org/0000-0002-2154-8740Andrew McWilliam5Shogo Otsubo6Yuki Sarugaku7Tomomi Takeuchi8Haruki Katoh9Satoshi Hamano10https://orcid.org/0000-0002-6505-3395Yuji Ikeda11https://orcid.org/0000-0003-2380-8582Hideyo Kawakita12https://orcid.org/0000-0003-2011-9159Charlie Hull13Rogelio Albarracín14Giuseppe Bono15https://orcid.org/0000-0002-4896-8841Valentina D’Orazi16https://orcid.org/0000-0002-2662-3762Department of Astronomy, School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan ; matsunaga@astron.s.u-tokyo.ac.jp; Laboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanInstituto de Estudios Astrofísicos, Universidad Diego Portales , Av. Ejército Libertador 441, Santiago, Chile; Instituto de Astrofísica, Pontificia Universidad Católica de Chile , Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile; Millenium Nucleus ERIS, Instituto de Estudios Astrofísicos, Universidad Diego Portales , Av. Ejército Libertador 441, Santiago, Chile; Millennium Institute of Astrophysics , Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, ChileNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanAmanogawa Galaxy Astronomy Research Center, Graduate School of Science and Engineering, Kagoshima University , 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, JapanObservatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USALaboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanLaboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanLaboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanLaboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanLaboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan; Photocoding, 460-102 Iwakura-Nakamachi, Sakyo-ku, Kyoto 606-0025, JapanLaboratory of Infrared High-resolution spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan; Department of Astrophysics and Atmospheric Sciences, Faculty of Science, Kyoto Sangyo University , Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, JapanObservatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USAInstituto de Astrofísica, Pontificia Universidad Católica de Chile , Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile; Millenium Nucleus ERIS, Instituto de Estudios Astrofísicos, Universidad Diego Portales , Av. Ejército Libertador 441, Santiago, Chile; Millennium Institute of Astrophysics , Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, ChileDipartimento di Fisica, Universita di Roma Tor Vergata , via della Ricerca Scientifica 1, I-00133 Roma, Italy; INAF Osservatorio Astronomico di Roma , via Frascati 33, I-00078 Monte Porzio Catone, ItalyDipartimento di Fisica, Universita di Roma Tor Vergata , via della Ricerca Scientifica 1, I-00133 Roma, Italy; INAF Osservatorio Astronomico di Padova , Vicolo dell’Osservatorio 5, I-35122 Padova, ItalyMetallicity 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.https://doi.org/10.3847/1538-4357/aced93Cepheid variable starsMetallicityMilky Way diskYoung disk Cepheid variable starsInfrared spectroscopy |
| spellingShingle | Noriyuki Matsunaga Daisuke Taniguchi Scarlet S. Elgueta Takuji Tsujimoto Junichi Baba Andrew McWilliam Shogo Otsubo Yuki Sarugaku Tomomi Takeuchi Haruki Katoh Satoshi Hamano Yuji Ikeda Hideyo Kawakita Charlie Hull Rogelio Albarracín Giuseppe Bono Valentina D’Orazi Metallicities of Classical Cepheids in the Inner Galactic Disk The Astrophysical Journal Cepheid variable stars Metallicity Milky Way disk Young disk Cepheid variable stars Infrared spectroscopy |
| title | Metallicities of Classical Cepheids in the Inner Galactic Disk |
| title_full | Metallicities of Classical Cepheids in the Inner Galactic Disk |
| title_fullStr | Metallicities of Classical Cepheids in the Inner Galactic Disk |
| title_full_unstemmed | Metallicities of Classical Cepheids in the Inner Galactic Disk |
| title_short | Metallicities of Classical Cepheids in the Inner Galactic Disk |
| title_sort | metallicities of classical cepheids in the inner galactic disk |
| topic | Cepheid variable stars Metallicity Milky Way disk Young disk Cepheid variable stars Infrared spectroscopy |
| url | https://doi.org/10.3847/1538-4357/aced93 |
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