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PI Total time #CoIs, team

ELT: A significant stepping-stone for improving the cosmic distances

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PI Total time #CoIs, team

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  1. ELT: A significant stepping-stone for improving the cosmic distances The main aim of this experiment is to improve cosmic distances using primary distance indicators (Classical Cepheids, tip of RGB). ELT will providethe unique opportunity to identify large samples of these objects in the Coma galaxy clusters. • PI • Total time • #CoIs, team Silvia Pedicelli 22h (ELT 42m) G. Bono (OAR); P. Francois (Observatoire de Paris-Meudon); M. Groenewegen (Katholieke Universiteit Leuven); C.D. Laney (South African Astronomical Observatory); B. Lemasle (Universitè de Picardie); M. Mottini (University of Washington); F. Primas (ESO); J. Pritchard (ESO);M. Romaniello (ESO).

  2. Scientific Rationale • Cepheids are one of the most important standard candles used for distance determination in the Universe. Pros: • Easy to recognise by their variability • Their evolutionary and pulsational properties are well-known • Are quite common in young stellar systems Cons: • time-series data • Bright but not enough ..... → ELT can solve these problems Immediate Objective • Run A: 4 images (I and K band) takes every 3 days (total 16 images in 4 nights) for two selected spiral galaxies of the Coma Cluster. • Run B: 2 images (K band) of selected Cepheds in spiral galaxy of Coma Cluster.

  3. ELT Justification Persson et al. (2004) • DMLMC = 18.48 ± 0.13 • DMCOMA = 34.64 ± 0.25 • In LMC → P = 10 → I ~ 14 • In COMA → P = 10 → I ~ 30 • In LMC → P = 10 → K ~ 13 • In COMA → P = 10 → K ~ 29 • DMCOMA – DMLMC ~ 16 Sebo & Rawson (2002)

  4. Legacy Value:These data will provide a pristine determination of the Hubble constant only based on primary distance indicators. They can also be used to calibrate secondary distance indicators (SNIa, GCLF, Tully-Fisher relation). Run MP Mode AO T. λ Pixel Notes A - Imaging LTAO 16h 0.8 µm 5 I & K B - Imaging LTAO 6h 2.2 µm 5 K band Run Target R.A. Dec. ToT Mag Notes A Coma 13h +28.5˚ 16h 30 S/N > 5 B Cepheids - - 6h 29 S/N > 3 DMCOMA = 34.64±0.25 dCOMA ~ 108 pc → α= 5 mas → r ~ 2 pc

  5. That’s all

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