Stellar Astrophysics: Things That Are Too Hard for Keck

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Stellar Astrophysics: Things That Are Too Hard for Keck. Judy Cohen (Caltech)+ Evan Kirby, the 0Z team and Branimir Sesar Astronomy in the TMT Era Tokyo, Oct 2013. Four Problems. Gravitational settling in the Sun & solar modeling Extremely metal-poor stars: CNO
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Stellar Astrophysics: Things That Are Too Hard for KeckJudy Cohen (Caltech)+ Evan Kirby, the 0Z team and BranimirSesarAstronomy in the TMT EraTokyo, Oct 2013Four ProblemsGravitational settling in the Sun & solar modelingExtremely metal-poor stars: CNOChemical Evolution in Nearby GalaxiesThe total mass of the Milky Way + finding more ultra-faint galaxies – RR Lyr + HSC/SubaruM13 HB, grav settling, rad levitation Behr, Cohen +VrotvsTeff, M13 HB, vrot drops rapidly as Teff upBehr, Cohen, +, ~2000,big effect !Richard, Michaud et al predict diffusion in low Fe/H dwarfsSize of effect reduced in response to our and others early work.M92 CMD + HIRES sample, reaches MSTOM92 [Fe/H] vsTeff, upper RGB to MSTO, HIRESM92, same for Ti12, can’t achieve needed accuracy, spent > 4 HIRES/Keck nights on MSTO. HIRES with multiplex would be great !0Z project, 122 EMP/HES, [C(CH)/Fe] vs[Fe/H]Adding N and O
  • C from 4300 strong CH band. N,O not so easy
  • N from NH band, 3360 A
  • O from OH bands, 3200 A or near 1.6 microns
  • Weak lines, in regions hard to observe
  • Really need full set of CNO abundances for best understanding
  • 122EMP stars, HES 0Z, new class found: low-Ca stars Chemical Evolution of the Local Group, Kirby, Cohen + many, Deimos/Keck
  • 2850 RGB stars in 8 dSph MW satellites, most distant Leo I at 260 kpc
  • 108 stars in 7 Ultra-Faint MW satellites, most distant CVnII at 160 kpc
  • 629 in 7 Local Group isolated dIrr, most distant VV 124 at 1,400 kpc
  • Kirby et al Local Group SampleSculptor, 375 RGB stars, ~100/slitmask[Fe/H] distributions, 7 isolated dIrrMDF for 4 most luminous dSph<[Fe/H]> vs Luminosity. All Deimos.Now add in SDSS data, <[Fe/H]> vs M(star)Combined MDF for luminous dSph and dIrrCMD Segue 2 SDSS, not many stars bright enough ACS CMDs for nearby UF galaxies Brown et al 2013WTPC2/HST Leo T (415 kpc) Clementini et al 2013We are now at the limit of Keck
  • Can’t do ultra-faints better – very few bright giants and can’t reach more numerous MS
  • No group has had success in finding more UF, PanStars none so far, PTF not suitable for this
  • Kirby, Cohen + no more MW satellites left close enough for Deimos
  • RR Lyr: Total Mass of the Milky Way with dark matter, and finding more UF MW satellitesRR Lyrae can be found in the PTF to ~100 kpcA period + a rough Fe/H determines an accurate luminosity and distanceWe have found ~100 RR Lyr at 70 < D < 100 kpc excluding more than 100 in the known dSph, with vr can infer total mass of MW out to 100 kpc.Using RR Lyr as lamp-posts can we find the very low luminosity stellar systems/streams in which they presumably live ?Palomar Transient Factory RR LyraeStars (~900 RR Lyr 30 < R < 100 kpc)RR Lyrae stars between 70 and 100 kpcSe~~8 RR Lyrae Stars at ~85 kpc in 45 deg2RR Ly 70-100 kpc(~90 in Draco dSph)Histogram – distances of outer halo RR Lyr, excludes RR Lyr in known MW satellitesHow to get beyond 100 kpc – HSC !!
  • Find the RR Lyr using HSC wide survey
  • Get periods using Keck (cadence project)
  • Get vr + rough Fe/H using Keck
  • Use known RR Lyr distance + matched filter algorithm to search HSC multi-color catalog for main sequence stars in the underlying low luminosity stellar system or stream
  • HSC is the ONLY way to do this !!!
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