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Cosmic Voids, Void Galaxies, and Void AGN

Cosmic Voids, Void Galaxies, and Void AGN . Michael S. Vogeley Department of Physics Drexel University. KNAW colloquium “Cosmic Voids” December 12-15, 2006. I. Void Finding in Nearby Redshift Surveys Fiona Hoyle, Danny Pan

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Cosmic Voids, Void Galaxies, and Void AGN

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  1. Cosmic Voids, Void Galaxies, and Void AGN Michael S. Vogeley Department of Physics Drexel University KNAW colloquium “Cosmic Voids” December 12-15, 2006

  2. I. Void Finding in Nearby Redshift Surveys Fiona Hoyle, Danny Pan II. Morphology-Luminosity-Local Density Relation and Residual Effects at Low Density Changbom Park, Yun-Young Choi, J. R. Gott, Michael Blanton III. Active Galactic Nuclei in Voids Anca Constantin, Fiona Hoyle Thanks to NSF, NASA, Korea Institute for Advanced Study, Aspen Center for Physics, and KNAW

  3. The Void Finder Algorithm Goal: identify large voids that are dynamically distinct elements of large-scale structure = “bucket-shaped” voids with flat density profiles and sharp edges, dr/r<-0.8 Procedure: • Initial classification of galaxies as wall/void galaxies • Detection of empty cells • Growth of maximal spheres • Unification of overlapping voids • Calculation of void underdensity, profile Hoyle & Vogeley 2002, ApJ, 566, 641

  4. Initial Classification of Void vs. Wall Galaxies If d3>7h-1 Mpc, then dr/r<-0.6 7h-1 Mpc 7h-1 Mpc WallGalaxy Void Galaxy Then grow maximal spheres bounded by wall galaxies

  5. Voids in the PSCz Survey Yellow – voids Red – void centers Blue – wall galaxies Largest void = 17.85 Mpc/h Average (of rmin = 10 Mpc/h) = 12.4 +/- 1.7 Nearly identical results for UZC. Same voids found in IR-selected PSCz and optically-selected UZC. Hoyle & Vogeley 2002, ApJ, 566, 641

  6. Voids in the 2dFGRS Red – void centers Black – wall galaxies 289 voids in total (zmax=0.1) Largest void radius =19.85 Mpc Average(r > 10) =12.4 +/- 1.9 Mpc Similar to PSCz and UZC results Hoyle & Vogeley 2004, ApJ, 607, 751

  7. Void Size Distributions in 2dF No detected variation of size distributions between N and S or with redshift. WFMOS on Subaru 8m could detect evolution of voids and measure q0.

  8. Voids in Simulations • VoidFinder applied to “galaxies” in simulations • Radii of voids match sharp boundaries of voids seen in both galaxies and dark matter • Density within voids nearly constant, reaches mean at nearly twice void radius Benson, Hoyle, Torres, & Vogeley 2003, MNRAS 340, 160

  9. SDSS DR5 • Spectroscopy of 675,000 galaxies • Covers 5740 sq deg • Imaging of 8000 sq deg (imaging of NGC region now complete)

  10. Voids in SDSS DR5 Parent galaxy sample: r<17.77, z<0.107, area = 5000 sq deg, 394,984 galaxies (after boundary cuts) Volume-limited sample: density field from 61,084 galaxies, M<-20.0 Results of voidfinder: 617 voids R>10 Mpc/h 40,635 void galaxies r<17.77 (10% of galaxies are in voids) Hoyle, Pan, Vogeley et al. 2007

  11. Intersection of Voids with 10 h-1 Mpc Slices Hoyle, Pan, Vogeley et al. 2007

  12. Results on Void Finding • Void distributions of 2dFGRS, PSCz, UZC, and SDSS agree; void properties are robust • No detected evolution of void size with redshift in nearby universe • Voids are on average ~12 h-1 Mpc in radius, but largest void larger in larger surveys? • Filling factor 40% at density contrast dr/r = -0.9 • Density profiles plateau in center to dr/r = -0.95 • Voidfinder appears to detect dynamically distinct elements of large-scale structure (peaks in initial gravitational potential, outflows in velocity, sharp boundaries in density)

  13. II. The Morphology-Luminosity-Local Density Relation and Residual Environmental Effects Park, Choi, Vogeley, Gott, & Blanton 2007, ApJ, accepted, astro-ph/0611610 REMINDER: Earlier papers on photometric and spectroscopic properties of SDSS void galaxies found that void galaxies are fainter, bluer, more disk-like, and have higher specific star formation rates. See Rojas, Vogeley, & Hoyle 2004a, ApJ, 617, 50, and 2005, ApJ, 624, 571 Hoyle, Rojas, & Vogeley 2005, ApJ, 620, 618

  14. Environmental Dependence Using Adaptive Smoothing and Morphological Classification Adaptive smoothing of volume-limited M* sample using spline kernel weighting of nearest Ns=20 galaxies.

  15. Morphological classification Choi & Park, 2005, ApJ 635, L29

  16. Bright galaxies added Extinction, K-correction, L-evolution corrected Volume-limited samples L*

  17. Morphology-Luminosity-Local Density Relation NS=20 smoothing NS=200 smoothing Relation continues down to lowest densities both at ~5 & 12 h-1Mpc scales Steepening of Efrac(r) relation on larger scales for fainter galaxies

  18. Morphology-Luminosity-Local Density Relation At fixed L, morphology is a strong function of density At fixed density, morphology is a strong function of L

  19. Color-magnitude relations • Early type “red sequence” shifts blueward by 0.025 mag from high to low density • Late type “blue sequence” shifts blueward by 0.14 mag at low density

  20. Size and environment • Small monotonic dependence of size on local density for all galaxies except the brightest E’s. • Galaxies in voids are slightly smaller: M=-19.7 galaxies are 8% smaller at the lowest density, for both early and late types (but possible sky subtraction error?).

  21. Star formation rates (Ha) Early Late At fixed morphology (early vs. late) and luminosity, very small dependence of SFR on local density: log[W(Ha)]=1.466-0.046 log(1+d) for M=-18.9 galaxies, weaker for brighter galaxies

  22. Results on Environmental Dependence • Strong local density-morphology-luminosity relation. Environment matters down to very low density! • At fixed luminosity and morphology, other galaxy properties show only weak dependence on density • Residual effects at low density • Color-magnitude shifts blueward, particularly for late types • Sizes of galaxies are smaller • Star formation in late types is higher • Morphology-density relation steepens for faint galaxies (for smoothing ~12 h-1 Mpc

  23. III. Active Galactic Nuclei in Voids Constantin & Vogeley 2006, ApJ 650, 727 Constantin, Hoyle, & Vogeley 2007

  24. emission-line Finding AGN among SDSS galaxies Seyferts LINERs 20% of all galaxies are strong line-emitters 52% H II 20% (pure) LINERs 7% Transition obj’s 5% Seyferts Transition objects H II nuclei (Constantin & Vogeley 2006)

  25. AGN Clustering higher peaks in the density field are more clustered (Constantin & Vogeley 2006) • H IIs:s0= 5.7  0.2 h-1 Mpc • less clustered than galaxies • Seyferts:s0= 6.0  0.6 • less clustered than galaxies LINERs:s0= 7.3  0.6 • clustered like galaxies Seyferts&H II’s: - less massive Dark Matter halos LINERs: - more massive Dark Matter halos all galaxies: s0= 7.8  0.5 MDM halo ~ MBH (Ferraresse 2002, Baes et al. 2003) Absolute Magnitude limited samples, -21.6 <M < -20.2 MBHSeyferts < MBHLINERs

  26. 6-line AGN Classification Constantin, Hoyle, & Vogeley 2007 “AGN in Void Regions”

  27. fractions in voids in walls AGN in Voids: Populations (Constantin, Hoyle, & Vogeley 2007) AGN of all types exist in voids: Compare at fixed brightness • No AGN in bright (L>>L*) void galaxies • Seyferts more frequent among Mr ~ -20 mag void galaxies • otherwise very similar AGN occurrence rate for S’s, L’s, and T’s (but not HII’s!)

  28. Log L[O I]/4 Log L[O III]/4 in walls in voids AGN in voids: accretion activity Seyferts LINERs • Accretion rates may be lower in void AGN…lower fueling rate? • Void galaxies have higher SFR per unit mass(Rojas, Vogeley, Hoyle 2005) • Gas available for forming stars but not driven efficiently to nucleus? (Constantin, Hoyle, & Vogeley 2007)

  29. AGN in voids: local environment as measured by nearest neighbor distance In voids: HII’s have the closest nn, then Transition, Seyferts, while LINERs have the farthest nn LINERs most isolated In walls: LINERs have closest nn HI’s have the farthest nn HII’s most isolated HII’s in poor groups? LINERs not driven by close interactions (Constantin, Hoyle, & Vogeley 2007)

  30. Accretion rate, [O I] Accretion rate, [O III] An AGN evolutionary sequence? I. HII’s - circumnuclear starburst, high accretion but obscured II. Seyferts - waning SF, brief breakout of accretion emission III. Transition obj’s - aging stellar pop, accretion weaker IV. LINERs - older stellar pop, minimal accretion, fuel exhausted BH mass Stellar mass Obscuration Stellar ages Dist to 3rd neighbor Dist to 1st neighbor

  31. Results on Void AGN • All types of AGN are found in voids, though 50% fewer LINERs and 50% more HII’s • No AGN in the brightest void galaxies • Excess of Seyferts in ~L* void galaxies • Possible lower accretion rate in void AGN • Local environments (nearest neighbor) of AGN types are opposite in voids/walls • Are void AGN (and their hosts) at an earlier stage in an evolutionary sequence?

  32. Publications about nothing Methods for void finding VoidFinder (Hoyle & Vogeley 2002, 2004) Statistics of Voids Void Probability Function (Hoyle & Vogeley 2004) Properties of observed void galaxies Photometry (Rojas, Vogeley, Hoyle 2004) Spectroscopy (Rojas, Vogeley, Hoyle 2005) Luminosity Function (Hoyle, Rojas, Vogeley 2005) Mass function (Goldberg et al. 2005) Metallicity (Hao et al. 2007, in prep) AGN in voids (Constantin, Hoyle, & Vogeley 2007) Environmental dependence (Park, Choi, Vogeley, Gott, & Blanton 2007) Simulations of void galaxies N-body + Semi-Analytic Models (Benson et al. 2003) Specialized void simulations (Goldberg & Vogeley 2004)

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