Rotation of Cosmic VoidsRotation of Cosmic Voids(Lee & Park 2006, ApJ in press, astro-ph/0606477)(Lee & Park 2006, ApJ in press, astro-ph/0606477)

Jounghun Lee & Deaseong ParkJounghun Lee & Deaseong Park

(Seoul National University)(Seoul National University)

OUTLINEOUTLINE

Origin and properties of voidsOrigin and properties of voids Questions about voids yet to be Questions about voids yet to be

answeredansweredA new nonparametric model for voidsA new nonparametric model for voids

key assumptionskey assumptionsanalytic predictionsanalytic predictionsnumerical testsnumerical tests

Discussion & conclusionDiscussion & conclusionOngoing & future worksOngoing & future works

Origin of Voids and ClustersOrigin of Voids and Clusters

Local extrema of the primordial density fieldLocal extrema of the primordial density field

x

x

Clusters

Voids

Properties of VoidsProperties of Voids Occupying 40% of the cosOccupying 40% of the cos

mic volume (Hoyle & Vogemic volume (Hoyle & Vogeley 2004)ley 2004)

Extremely underdense: Extremely underdense: VV ~ -0.9 ~ -0.9

Expanding fasterExpanding faster

Containing bluer galaxies Containing bluer galaxies with higher SFR (Hoyle et with higher SFR (Hoyle et al. 2005)al. 2005)

(2dFGRS, Hoyle et al. 2005)

Unresolved IssuesUnresolved Issues

Why are voids non-spherical ?Why are voids non-spherical ?Not intuitive due to the very fact that Not intuitive due to the very fact that

they have low-density and undergo they have low-density and undergo faster expansionfaster expansion

Why are void galaxies bluer with high Why are void galaxies bluer with high SFR?SFR?Not explained by the density-Not explained by the density-

morphology relation (Hoyle et al. 2005)morphology relation (Hoyle et al. 2005)

Clues from Previous WorksClues from Previous Works

Shandarin et al (2006, MNRAS, 367, 1629)Shandarin et al (2006, MNRAS, 367, 1629) Identifying voids using the excursion set approIdentifying voids using the excursion set appro

ach in high-resolution simulationsach in high-resolution simulations

Quantified the nonsphericity of voidsQuantified the nonsphericity of voids

Suggesting that voids undergo stronger tidal efSuggesting that voids undergo stronger tidal effectfect

Linear Tidal Torque TheoryLinear Tidal Torque Theory

Alignments between tAlignments between the spin axes and the ihe spin axes and the intermediate principal ntermediate principal axes of the local tidal axes of the local tidal tensorstensors Aspherical shapes of pAspherical shapes of p

rotohalosrotohalos Misalignments betweeMisalignments betwee

n the tidal and the inern the tidal and the inertia tensorstia tensors

A New TheoryA New Theory ClustersClusters form in the regions where the form in the regions where the

degree of alignmentdegree of alignment between between TT and and II is is strongeststrongest.. Less vulnerable to the tidal effectLess vulnerable to the tidal effect Low spin-generation efficiencyLow spin-generation efficiency

VoidsVoids form in the initial regions where the form in the initial regions where the degree of misalignmentdegree of misalignment between between TT and and II is is weakestweakest More vulnerable to the tidal effectMore vulnerable to the tidal effect High spin-generation efficiencyHigh spin-generation efficiency

Spin Generation EfficiencySpin Generation Efficiency

Tidal Effect on VoidsTidal Effect on Voids

Generating the rotation of matter that Generating the rotation of matter that make up voids around the center of mass.make up voids around the center of mass.

Inducing the strong alignments between Inducing the strong alignments between the void spin axis and the intermediate the void spin axis and the intermediate principal axis of local tidal tensorprincipal axis of local tidal tensor

Key Prediction IKey Prediction I

CorrelationsCorrelations between the spin axes between the spin axes of neighbor spinsof neighbor spins

Key Prediction IIKey Prediction II

Anti-correlationsAnti-correlations between the spin between the spin axes of voids and the directions to axes of voids and the directions to the nearest voidsthe nearest voids

Void Spin-Spin CorrelationsVoid Spin-Spin Correlations

Void Spin-Direction Void Spin-Direction CorrelationsCorrelations

Finding Voids from SimulationsFinding Voids from Simulations

The Millennium-Run Galaxy CThe Millennium-Run Galaxy Catalogatalog 2160216033 particles particles Linear size of 500 Mpc/h Linear size of 500 Mpc/h CDM CosmogonyCDM Cosmogony 8964936 galaxies at z=08964936 galaxies at z=0

The Void-Finder by Hoyle & VThe Void-Finder by Hoyle & Vogeley (2002, ApJ, 566, 64ogeley (2002, ApJ, 566, 641)1)

24037 voids with N24037 voids with Ngg > 30 > 30

Measuring Void SpinMeasuring Void Spin

Void Density DistributionVoid Density Distribution

Void Spin Parameter Void Spin Parameter DistributionDistribution

Analytic vs. Numerical IAnalytic vs. Numerical I

Analytic vs. Numerical IIAnalytic vs. Numerical II

DiscussionDiscussion

Strong tidal effect on voidsStrong tidal effect on voids Deviate void shapes from spherical symmetryDeviate void shapes from spherical symmetry

The less massive, the higher degree of triaxiality The less massive, the higher degree of triaxiality

Transfer high angular momentum to void galaxiTransfer high angular momentum to void galaxiesesBlock gas cooling Block gas cooling Delay star formation Delay star formation Explain the high SFR and bluer colors of void galaxiExplain the high SFR and bluer colors of void galaxi

es:es:

Summary and ConclusionSummary and Conclusion

Constructing a new theory for cosmic voidsConstructing a new theory for cosmic voids

Quantifying the tidal effect on the voidsQuantifying the tidal effect on the voids Void spin-spin correlationVoid spin-spin correlation Void spin-direction anti-correlationVoid spin-direction anti-correlation

Providing a quantitative physical explanations to tProviding a quantitative physical explanations to the observed properties of voidshe observed properties of voids

Providing a new insight to the large-scale matter Providing a new insight to the large-scale matter distribution in a cosmic webdistribution in a cosmic web