PHANGS-JWST first results: a combined HST and JWST analysis of the nuclear star cluster in NGC 628
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2023
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IOP Publishing
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Abstract
We combine archival Hubble Space Telescope and new James Webb Space Telescope imaging data covering the ultraviolet to mid-infrared regime to morphologically analyze the nuclear star cluster (NSC) of NGC 628, a granddesign spiral galaxy. The cluster is located in a 200 pc × 400 pc cavity lacking both dust and gas. We find roughly constant values for the effective radius (r_(eff) ∼ 5 pc) and ellipticity (∈ ∼ 0.05), while the Sérsic index (n) and position angle (PA) drop from n ∼ 3 to ∼2 and PA ∼ 130° to 90°, respectively. In the mid-infrared, r_(eff) ∼ 12 pc, ∈ ∼ 0.4, and n ∼ 1–1.5, with the same PA ∼ 90°. The NSC has a stellar mass of log_(10) (M^(nsc)_(*) / M_(ꙩ) = 7.06 0.31, as derived through B − V, confirmed when using multiwavelength data, and in agreement with the literature value. Fitting the spectral energy distribution (SED), excluding the mid-infrared data, yields a main stellar population age of (8 ± 3) Gyr with a metallicity of Z = 0.012 ± 0.006. There is no indication of any significant star formation over the last few gigayears. Whether gas and dust were dynamically kept out or evacuated from the central cavity remains unclear. The best fit suggests an excess of flux in the mid-infrared bands, with further indications that the center of the mid-infrared structure is displaced with respect to the optical center of the NSC. We discuss five potential scenarios, none of them fully explaining both the observed photometry and structure.
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© 2023. The Author(s). Artículo firmado por 32 autores. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555. These observations are associated with program 15654. This work is based on observations made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. The observations are associated with JWST program 02107. This research has made use of the Spanish Virtual Observatory (https://svo.cab.intacsic.es) project funded by MCIN/AEI/10.13039/ 501100011033/ through grant PID2020-112949GB-I00. N.H. and A.W.H.K. are fellows of the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD) and acknowledge their support. N.H. acknowledges support from Thomas Müller (HdA/MPIA) with generating part of Figure 1 and Katja Fahrion and Torsten Böker for useful discussions. A.T.B. and F.B. would like to acknowledge funding from the European Research Council (ERC) under the European Unionʼs Horizon 2020 research and innovation program (grant agreement No. 726384/Empire). E.J.W. acknowledges the funding provided by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 138713538—SFB 881 (“The Milky Way System,” subproject P1) T.G.W. and J.N. acknowledge funding from the European Research Council (ERC) under the European Unionʼs Horizon 2020 research and innovation program (grant agreement No. 694343). J.M.D.K. gratefully acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG (grant agreement No. 714907). COOL Research DAO is a Decentralized Autonomous Organization supporting research in astrophysics aimed at uncovering our cosmic origins. R.S.K. acknowledges funding from the European Research Council via the ERC Synergy Grant “ECOGAL” (project ID 855130), the Deutsche Forschungsgemeinschaft (DFG) via the Collaborative Research Center “The Milky Way System” (SFB 881—funding ID 138713538—subprojects A1, B1, B2 and B8), and the Heidelberg Cluster of Excellence (EXC 2181-390900948) “STRUCTURES,” funded by the German Excellence Strategy. R.S.K. also thanks the German Ministry for Economic Affairs and Climate Action for funding in the project “MAINN” (funding ID 50OO2206). E.R. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference No. RGPIN-2022-03499. M.B. acknowledges support from FONDECYT regular grant 1211000 and by ANID BASAL project FB210003. K.G. is supported by the Australian Research Council through the Discovery Early Career Researcher Award (DECRA) Fellowship DE220100766 funded by the Australian Government. K.G. is supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) through project No. CE170100013. F.N.-L. gratefully acknowledges the sponsorship provided by the Federal Ministry for Education and Research of Germany through the Alexander von Humboldt Foundation. P.S.B. acknowledges financial support from MCIN/AEI/10.13039/501100011033 under grant PID2019-107427GB-C31 A.K.L. gratefully acknowledges support by grants 1653300 and 2205628 from the National Science Foundation, award JWST-GO-02107.009-A, and a Humboldt Research Award from the Alexander von Humboldt Foundation. G.A.B. acknowledges the support from ANID Basal project FB210003.