Publication Year 2019 Acceptance in OA@INAF 2020-12-17T18:49:30Z Title Stellar population astrophysics (SPA) with the TNG. GIANO-B spectroscopy of red supergiants in Alicante 7 and Alicante 10 Authors ORIGLIA, Livia; Dalessandro, Emanuele; SANNA, Nicoletta; Mucciarelli, A.; OLIVA, Ernesto; et al. DOI 10.1051/0004-6361/201936283 Handle http://hdl.handle.net/20.500.12386/28965 Journal ASTRONOMY & ASTROPHYSICS Number 629 A&A 629, A117 (2019) Astronomy https://doi.org/10.1051/0004-6361/201936283 & c ESO 2019 Astrophysics Stellar population astrophysics (SPA) with the TNG GIANO-B spectroscopy of red supergiants in Alicante 7 and Alicante 10? L. Origlia1, E. Dalessandro1, N. Sanna2, A. Mucciarelli3,1, E. Oliva2, G. Cescutti4, M. Rainer2, A. Bragaglia1, and G. Bono5,6 1 INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy e-mail: [email protected] 2 INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 3 Dipartimento di Fisica e Astronomia, Universitá degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy 4 INAF – Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34143 Trieste, Italy 5 Dipartimento di Fisica e Astronomia, Universitá degli Studi di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy 6 INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone, Italy Received 10 July 2019 / Accepted 12 August 2019 ABSTRACT Aims. The Scutum complex in the inner disk of the Galaxy hosts a number of young clusters and associations of red supergiant stars that are heavily obscured by dust extinction. These stars are important tracers of the recent star formation and chemical enrichment history in the inner Galaxy. Methods. Within the SPA Large Programme at the TNG, we secured GIANO-B high-resolution (R ' 50 000) YJHK spectra of 11 red supergiants toward the Alicante 7 and Alicante 10 associations near the RSGC3 cluster. Taking advantage of the full YJHK spectral coverage of GIANO in a single exposure, we were able to measure several hundreds of atomic and molecular lines that are suitable for chemical abundance determinations. We also measured a prominent diffuse interstellar band at λ1317.8 nm (vacuum). This provides an independent reddening estimate. Results. The radial velocities, Gaia proper motions, and extinction of seven red supergiants in Alicante 7 and three in Alicante 10 are consistent with them being members of the associations. One star toward Alicante 10 has kinematics and low extinction that are inconsistent with a membership. By means of spectral synthesis and line equivalent width measurements, we obtained chemical abundances for iron-peak, CNO, alpha, other light, and a few neutron-capture elements. We found average slightly subsolar iron abundances and solar-scaled [X/Fe] abundance patterns for most of the elements, consistent with a thin-disk chemistry. We found depletion of [C/Fe], enhancement of [N/Fe], and relatively low 12C=13C < 15, which is consistent with CN cycled material and possibly some additional mixing in their atmospheres. Key words. supergiants – stars: abundances – infrared: stars 1. Introduction light element abundances with the necessary high accuracy. These different elements are synthesized in stars and supernovae Stellar population astrophysics experiences a golden era because with different mass progenitors and are therefore released into of the Gaia mission and ongoing and near-future massive pho- the interstellar medium with different time delays with respect tometric, astrometric, and spectroscopic surveys that set the to the onset of the star formation event. observational framework for an exhaustive description of the structure of the Milky Way (MW) and its satellites. Optical and SPA Large Programme. The unique combination of the near-infrared (NIR) high-resolution (HR) spectroscopy is cru- High Accuracy Radial velocity Planet Searcher for the Northern cial to provide the complementary detailed chemical tagging emisphere (HARPS-N) and GIANO-B echelle spectrographs at of selected stellar populations, in order to constrain timescales the Telescopio Nazionale Galileo (TNG), which together cover and overall formation and chemical enrichment scenarios. Only almost the full optical and NIR range out to the K band, is ideal echelle spectra with simultaneous HR and wide spectral cov- to sample the luminous stellar populations of the MW thin disk erage might be able to allow measurements of the full set of over almost its entire extension, as seen from the Northern Hemi- iron-peak, CNO, alpha, neutron-capture, Li, Na, Al, and other sphere at a spectral resolution R ≥ 50 000. Thus, taking advan- ? tage of this HR capability, we proposed a Large Program called Based on observations made with the Italian Telescopio Nazionale the SPA (Stellar population astrophysics: detailed age-resolved Galileo (TNG) operated on the island of La Palma by the Fundación chemistry of the Milky Way disk; Program ID A37TAC_13, PI: Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de L. Origlia). Observing time has been granted starting from June Astrofisica de Canarias. This study is part of the Large Program titled 2018. The SPA Large Programme aims at obtaining high-quality SPA (Stellar population astrophysics: the detailed, age-resolved chem- spectra of more than 500 stars in the MW thin disk and associ- istry of the Milky Way disk; PI: L. Origlia), granted observing time with ated star clusters at different Galactocentric distances, including HARPS-N and GIANO-B echelle spectrographs at the TNG. the poorly explored inner disk. We will observe luminous giant Article published by EDP Sciences A117, page 1 of9 A&A 629, A117 (2019) and supergiant stars in young star clusters and associations, lumi- et al. 2009a) using NIRSPEC-Keck spectra at a resolution R ≈ nous Cepheid and Mira variables across the entire thin disk, and 17 000. They suggest slightly subsolar abundances. main-sequence (MS) and other evolved stars of open clusters in RSGs are very luminous NIR sources even in highly red- the solar neighborhood. dened environments, such as the inner Galaxy, and they can be The proposed observations will allow us to provide a detailed spectroscopically studied at HR even with 4 m class telescopes mapping of possible gradients, cosmic spreads, and other inho- when these are equipped with efficient echelle spectrographs. A mogeneities of individual abundances and abundance ratios. We few years ago, during the commissioning and science verifica- will also be able to answer a number of open questions regarding tion of GIANO (see, e.g., Oliva et al. 2012a,b, 2013; Origlia et al. disk formation, evolution, and chemical enrichment, and we will 2014), we therefore acquired HR (R ≈ 50 000) YJHK spectra of perform critical tests of stellar evolution and nucleosynthesis. a few RSGs in the RSGC2 and RSGC3 clusters. This will maximize the scientific return and the overall legacy In particular, we observed three RSGs in RSGC2 in July value for astrophysics. 2012 and five RSGs RSGC3 in October 2013. Detailed RVs and Based on this detailed chemical tagging and complementary chemical abundances of iron-peak, CNO, alpha, and a few other kinematic and evolutionary information from the Gaia mission metals have been published in Origlia et al.(2013, 2016). They and other surveys, we expect in particular to set the framework confirmed slightly subsolar iron and iron-peak elements, some for a comprehensive chemodynamical modeling of the disk for- depletion of carbon and enhancement of nitrogen, and approxi- mation and evolution. We hope to be able to distinguish radial mately solar-scale [X/Fe] abundance ratios for the other metals. migration from in situ formation scenarios (e.g., da Silva et al. Prompted by the results of these pilot projects, we decided to 2016, and references therein) and the overall chemical enrich- perform a more systematic investigation of the RSGs in the Scu- ment history. In addition, given the expected high quality of tum complex. As part of the SPA Large Program at the TNG, we the acquired spectra and the target properties, we will be able are observing a representative sample of luminous RSG stars, to perform the following stellar evolution tests and calibrations: candidate members of the young clusters and associations in (i) a first systematic investigation of the dependence of period- the Scutum complex, using the refurbished GIANO-B spectro- luminosity relations of variable stars on their detailed chemical graph. This first paper presents the derived RVs and chemical content, (ii) a probe of the poorly explored physics and nucle- abundances for RSG candidate members of the Alicante 7 and osynthesis of red supergiants (RSGs), and (iii) a probe of crucial Alicante 10 associations near the RSGC3 star cluster. stellar evolution parameters, such as convection, diffusion, mix- ing, rotation, and magnetic fields in MS and evolved stars for different stellar ages and evolutionary stages. 3. Observations and data reduction GIANO (Origlia et al. 2014) is the HR (R ' 50 000) YJHK (950–2450 nm) spectrometer of the TNG telescope. GIANO was 2. High-resolution spectroscopy in the Scutum designed to receive light directly from a dedicated focus of the complex TNG. The instrument was provisionally commissioned in 2012 and was used in the GIANO-A configuration. In this position, In the central region of the MW close to the base of the Scutum- the spectrometer was positioned on the rotating building and fed Crux arm and the tip of the long bar, at a distance of ≈3.5 kpc through a pair of fibers that were connected to another focal sta- from the Galactic center, lies a giant region of star formation tion (Tozzi et al. 2014). The spectrometer was eventually moved that is known as the Scutum complex.