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MASS-TO-LIGHT FUNCTION: from Galaxies to Superclusters

This presentation explores the concept of the Mass-to-Light (M/L) function as crucial for understanding the distribution of matter in the universe. The study delves into the work of pioneers like Vera Rubin and Neta A. Bahcall, focusing on how M/L ratios vary across different scales, from galaxies to superclusters. By employing methods such as galaxy motion analysis, hot gas temperature measurement, and gravitational lensing, we assess the mass distribution and its implications for cosmological models. This examination highlights the richness of dark matter and its pervasive influence in the universe.

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MASS-TO-LIGHT FUNCTION: from Galaxies to Superclusters

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  1. MASS-TO-LIGHT FUNCTION: from Galaxies to Superclusters Celebrating Vera Rubin Neta A. Bahcall Princeton University

  2. “In a spiral galaxy, the ratio of dark-to-light matter is about a factor of ten. That's probably a good number for the ratio of our ignorance-to-knowledge. We're out of kindergarten, but only inabout third grade.”

  3. Vera’s Rotation Curves M/L Kaptyen (Local) 1920’s Zwicky (Clusters) 1930s Rubin (Galaxies) 1970s ( M/L ~ R )

  4. Mass-to-Light FunctionM/L(R) • How does M/L depend on scale? • How and where is the mass distributed? • How use it to weigh Universe? • <M/L>rep Luniv(Lo/Vol) = m(Mo/Vol) • Determine M, <M/L> of clusters, SCs, LSS  <M/L> rep [≈ 300h] •  m ~ 0.2 +-0.05

  5. Weighing Clusters 3 Basic Methods • Motion of galaxies[MR ~ v2R] Temperature of hot gas[MR~TR]  Gravitational lensing[MR]

  6. M/L(R) (Davis etal 1980) Ωm=1 Clusters Groups Galaxies

  7. Mass-to-Light Function (Bahcall, Lubin & Dorman ‘95; Bahcall and Fan ‘98) Ωm = 1.0 Ωm = 0.3 Ωm=0.25 1. M/L flattens on large-scales: M ~ L. End of Dark Matter. 2. Sp + E produce M/L of groups, clusters; Clusters: ~ no excess DM ! 3. Most of the DM is in huge halos around galaxies ( ~200-300 Kpc)

  8. Mass-to-Light Function (Bahcall, Lubin & Dorman ‘95; Bahcall and Fan ‘98) SDSS Ωm=0.2

  9. M/L(R) Function: simulations(Bahcall, Yu, etal ’01) Same shape as observed: FLAT on large-scales (M ~ L) Cluster M/L increases with Mcl. Explains M/L Groups to Clusters Anti-Bias of Rich Clusters: their M/LB larger than average (LB low)

  10. Cluster M/L versus T (or M) (Bahcall and Comerford ’02) M/L=(173+-29) Tkev0.30+-0.08 Data vs Sims Data vs Sims Due to mergers (lowers L at a fixed Mass)? Increase in E-fraction; Older systems (L fades)?

  11. Theory vs. Observations (Bahcall, Yu, et al ‘01) ------------- ----------

  12. SDSS Cluster Mass Profile: Weak Lensing 2x104 SDSS clusters, N=3 to 220. (Sheldon et al 2008) X = R200 NFW

  13. Cluster M/Li(R) Profile (SDSS, weak lensing2x104 clusters N= 3 to 220 (Sheldon etal 2008) Flat >~ 1Mpc M ~ L X=R(vir)

  14. Cluster (M/L)200 versus M200 M/L~M0.33+-0.02 M/L ~ M0.33+-0.02

  15. M/Li(r=22Mpc) vs. Mcl(SDSS; Sheldon etal ‘08) Ωm= 0.2 +- .03 Flat M/L on large scales; SAME for ALL clusters!

  16. M/L Function: Conclusions • M/L Function Flattens on Large Scales  M ~ L(reaching end of Dark-Matter) • Dark Matter located mostly in large galactic halos ~300s Kpc) Group/Clusters: made up of Sp+E; no significant additional DM • Cluster M/L increases slightly with M (mergers?) • Rich clusters M/LB is ‘Anti-biased’ (M/LB>mean) • Asymptotic Cluster M/Li(22Mpc) is same for ALL Groups and Clusters, 362+-54h ! • Mass-Density of Univers: m = 0.2 +- 0.04

  17. Improved Cluster Mass Tracer from SDSS(R.Reyes etal 2008) • Improved optical cluster mass tracer from SDSS, using weak-lensing calibration • Tested M200 versus N200 (richness), L200, LBCG, and combinations (avail in many surveys) • Best tracer (least scatter, highest Mcl): Combination of RichnessandLBCG: M ~ N1.2 LBCG0.7 M200 = (1.27+-0.08) (N200/20)1.20+-0.09 x [LBCG/<LBCG>(N200)]0.71+-0.14 • LBCGimportant second parameter. Consistent with merger picture: At fixed Mcl mergers produce Lower N and Brighter LBCG

  18. M200 vs. LBCG [at fixed N200] (Reyes etal ‘08) M200 = (1.27+-0.08) (N200/20)1.20+-0.09 x [LBCG/<LBCG>(N200)]0.71+-0.14

  19. Weighing the Universe  M/L Function m= 0.2 +- 0.04  Baryon Fraction 0.24 +- 0.04  Cluster Abundance 0.2 +- 0.05 and Evolution [8 =0.9 +- 0.1] • Supernovae Ia + Flat 0.25 +- 0.05 • CMB + LSS + h + Flat 0.24 +- 0.04  m ≈ 0.23 +- 0.05  4% Baryons + ~20% Dark Matter • Mass ~ Light

  20. “ The joy and fun of understanding the universe is what we bequeath to our grandchildren and their grandchildren. With over 90% of the matter in the universe still to play with, even the sky will not be the limit.” Vera C. Rubin

  21. Dedication to Women inScienceGreatWall, China 1986 (Margaret, Anna, Vera, Neta)

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