Cosmic%20Voids,%20Void%20Galaxies,%20and%20Void%20AGN

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Cosmic Voids, Void Galaxies, and Void AGN

• Michael S. Vogeley
• Department of Physics
• Drexel University

KNAW colloquium Cosmic Voids December 12-15,
2006
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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
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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/rlt-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
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Initial Classification of Void vs. Wall Galaxies
If d3gt7h-1 Mpc, then
dr/rlt-0.6
7h-1 Mpc
7h-1 Mpc
Wall Galaxy
Void Galaxy
Then grow maximal spheres bounded by wall galaxies
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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
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Voids in the 2dFGRS
Red void centers Black wall galaxies 289
voids in total (zmax0.1) Largest void radius
19.85 Mpc Average(r gt 10) 12.4 /- 1.9
Mpc Similar to PSCz and UZC results
Hoyle Vogeley 2004, ApJ, 607, 751
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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.
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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
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SDSS DR5

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

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Voids in SDSS DR5
Parent galaxy sample rlt17.77, zlt0.107, area
5000 sq deg, 394,984 galaxies (after boundary
cuts) Volume-limited sample density field from
61,084 galaxies, Mlt-20.0 Results of
voidfinder 617 voids Rgt10 Mpc/h 40,635 void
galaxies rlt17.77 (10 of galaxies are in voids)
Hoyle, Pan, Vogeley et al. 2007
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Intersection of Voids with 10 h-1 Mpc Slices
Hoyle, Pan, Vogeley et al. 2007
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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)

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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
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Environmental Dependence Using Adaptive Smoothing
and Morphological Classification
Adaptive smoothing of volume-limited M sample
using spline kernel weighting of nearest Ns20
galaxies.
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Morphological classification
Choi Park, 2005, ApJ 635, L29
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Bright galaxies added Extinction, K-correction,
L-evolution corrected
Volume-limited samples
L
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Morphology-Luminosity-Local Density Relation
NS20 smoothing
NS200 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
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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
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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

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Size and environment

• Small monotonic dependence of size on local
  density for all galaxies except the brightest
  Es.
• 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?).

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Star formation rates (Ha)
Early
Late

• At fixed morphology (early vs. late) and
  luminosity, very small dependence of SFR on local
  density logW(Ha)1.466-0.046 log(1d) for
  M-18.9 galaxies, weaker for brighter galaxies

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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

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III. Active Galactic Nuclei in Voids
Constantin Vogeley 2006, ApJ 650,
727 Constantin, Hoyle, Vogeley 2007
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Finding AGN among SDSS galaxies
Seyferts
LINERs

• 20 of all galaxies are
• strong line-emitters
• 52 H II
• 20 (pure) LINERs
• 7 Transition objs
• 5 Seyferts

Transition objects
H II nuclei
(Constantin Vogeley 2006)
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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 IIs - 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 ltM
lt -20.2
MBH Seyferts lt MBHLINERs
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6-line AGN Classification
Constantin, Hoyle, Vogeley 2007 AGN in Void
Regions
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AGN in Voids Populations
(Constantin, Hoyle, Vogeley 2007)
AGN of all types exist in voids
Fraction in voids Fraction in walls
Seyferts 1.5 1.5
LINERs 2.0 4.1
Transition Objects 5.3 6.4
H IIs 32.8 20.8
Compare at fixed brightness

• No AGN in bright (LgtgtL) void galaxies
• Seyferts more frequent among Mr -20 mag void
  galaxies
• otherwise very similar AGN occurrence rate for
  Ss, Ls, and Ts (but not HIIs!)

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AGN in voids accretion activity
Seyferts
LINERs

• Accretion rates may be lower in void AGNlower
  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)
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AGN in voids local environment
as measured by nearest neighbor distance
In voids HIIs have the closest nn,
then Transition, Seyferts, while LINERs have the
farthest nn LINERs most
isolated In walls LINERs have closest nn HIs
have the farthest nn HIIs most
isolated
NN distance voids NN distance walls
LINERs 5.9 ?0.6 1.3 ?0.05
Seyferts 5.8 ?0.9 1.6 ?0.1
Transition Objects 4.8 ?0.4 1.8 ?0.05
H IIs 4.4 ?0.2 1.9 ?0.03
HIIs in poor groups? LINERs not driven by close
interactions
(Constantin, Hoyle, Vogeley 2007)
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Accretion rate, O I
Accretion rate, O III

• An AGN evolutionary sequence?
• I. HIIs - circumnuclear starburst, high
  accretion but obscured
• II. Seyferts - waning SF, brief breakout of
  accretion emission
• III. Transition objs - aging stellar pop,
  accretion weaker
• IV. LINERs - older stellar pop, minimal
  accretion, fuel exhausted

Stellar mass
BH mass
Obscuration
Stellar ages
Dist to 3rd neighbor
Dist to 1st neighbor
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Results on Void AGN

• All types of AGN are found in voids, though 50
  fewer LINERs and 50 more HIIs
• 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?

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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)