Françoise CombesObservatoire de ParisMay 10, 2012

Effects of Gas Flows at Low Redshift

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Outline

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1- Gas accretion and secular evolution: bars

2- Evolution of disk size, radial migration, inflow/outflow

3- Dilution of metallicity

4- Thick disks

5- Cooling flows: inflow/outflow again

6- AGN fueling

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1- Gas accretion: essential to secular evolution

Importance of gas accretion all along the evolution, to avoidtoo many spheroids, and replenish disks

Gas accretionSecularevolution

Bar-bulge cycle

1-3:1

Multiple minor

4-10:1

Major merger

Time (Myr)

Bar

Str

engt

h

Bars formation anddestruction

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Self-regulated cycle:Bar produces gas inflow, and Gas inflow destroys the bar

2% of gas infall is enough to transform a bar in a lens(Friedli 1994, Berentzen et al 1998, Bournaud & Combes 02, 04)

Effect of gas inflow

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Replenish the disk, destabilises itGenerate Star Formation, and bar/spiral at the same timeGravity torques as a consequenceGas inflow rapidly to the center inside corotationBulge et Black hole growth

In simulations, the SFR and Q-parameter adjust so that theinflow rate roughly equals the SFR

Bar torques: inflow and outflow, not easy to measure (indirect)

Accretion by intermittence

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If no continuous accretionGas is stalled at OLRThe bar remains strong(early-types)

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Warps and polar rings from cosmic gas accretion

Brook et al 2008

Model NGC 4650AAlignment through torques disk/halo, warps in the outer parts

Roskar et al 2008

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Mastropietro et al 2012

Gas accretion

May mimickmergers

Gas accretion may explain -- asymmetries, lopsidedness-- clumpiness-- maintained SFR

Transient Ring formation

9Mastropietro et al 2012

The ring may disappearIf the accretion continues

Hoag object (HST)

2- Disk size evolution

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Bars and spirals re-distribute angular-momentum Stars

Gas

SFR

Age

Roskar et al 2008

L

L

Radial migrationSellwood & Binney 2002

Bar+spiral: radial migrations

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Overlap of resonances

Minchev et al 2010

Size evolution with redshift

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102 SF galaxies at z=1.5-3 , about half the radius of local galaxiesNagy et al 2011, z=2-3 Weinzirl et al 2011

re ~(1+z)-

=1.4 Nagy et al 2011=1.3 van Dokkum et al 2010=1.1 Mosleh et al 2011

Stellar radii at a given mass are ~half lower, at z=2-3

Minor mergers to increase galaxy radius?

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Newman et al 2011

Candels: search for companions around quiescent red galaxies ~15%

Possible if e < 1Gyr (e merging time)

But possible only for z=1,At z=2 other processes arerequired

Size evolution with bars/spirals

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Minchev et al (2012)

Secular evolution can triple in 3 Gyrs the effective size of disks

Thickening evolution

15---- Cororation ______ OLR

While radially extending, stellar disks are thickening

Effect of in plane gas accretion

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Minchev et al (2012)

Type II or III disks

5Mo/yr accretion rate

No big effect in old stars

3- Metallicity dilution

pericentermerger

Gas flows due to gravity torques during an interactionFresh gas, low-Z in the center (also Rupke et al 2010)

Amplitude 0.2-0.3 dex in agreement with observations(Kewley et al. 2006, Rupke et al. 2008) 17

Dilution due to flybys

Dilution seen in fly-bys also, Montuori et al 2010

Duration < 500 Myr elements enrichment during this phaseMay help to date the event

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B

Enrichment in /Fe, speed of star formation cycles19

Fundamental metallicity relation

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Requires slow gas infall, chemical time-scale long wrt dynamicalMannuci et al 2010

4- Thick disk formation

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Several scenarios at play:In addition to accretion and disruption of satellites, or disk heating due to minor merger

Radial migration, via resonant scattering

Loebman et al 2011

Radial migration: abundances & Vrot

22Loebman et al 2011

5- Gas flow in coolcore clusters

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Salomé et al 2006

Perseus A , Fabian et al 2003

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Cold CO in filaments

Salome et al 2008

Velocity much lower than free-fall

Here also, inflow and outflow coexist

The molecular gas coming from previous cooling is dragged out by the AGN feedback

The bubbles create inhomogeneities and further cooling

The cooled gas fuels the AGN

Numerical simulations (Revaz, Combes, Salome 2007)

25Log Temperature (150kpc) Log density (25x50kpc)

Buoyant bubbles, compressionand cooling at the surfaces+Cold gas dragged upwards

OI, CII with Herschel

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Same morphology +Same spectrabetween CO(2-1) and OI

Same gas, cooling throughdifferent phases?

No rotation, but inflows

Edge et al 2010Mittal et al 2010

6- AGN fueling Disk instabilities: Bars within bars, m=2 Lopsidedness, m=1, warps, bending

But alsoClumps, turbulent viscosity, dyn. friction

Feedback, outflows (SF, AGN)

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Bar gravity torques

Torque map for NGC 3627 (Casasola et al 2011)

Action on the gas: sign of the torques, depending on the phase shift between gas and stellar potential

Torques computed from the red image, on the gas distribution

The gas transfers AM to the stars Weakens or destroys the bar

Small-scale accretion

Hopkins et al 2011

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Simulations of gas accretion onto a central BH thick disks (~10pc)Zoomed simulation: cascade of m=2, m=1, + clumps and turbulence

When fgas large1022-1025 cm-2

Clump unstableWarps, twistsBendingThick disks

Dynamicalfriction of GMCIf M= 106Mot~80Myr (r/100pc)2

varies in 1/M

Gas is piling up in the center: up to f=90%

Inflow rate, stochastic

Hopkins & Quataert 2010

30Development of a bar

2nd resimulation 1st resimulation

Episodic accretion

31Dasyra & Combes 2011, 2012

4C12.50 SFR ~400-1000 Mo/yrOutflow ~130 Mo/yr

6 out of 300systems searchedshow H2 outflows

Feedback in nuclei: H2 & CO

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Statistics -- Time-scales10-100pc fueling

Only ~35% of negative torques in the center, scale 1"~50-100pc6 out of 16 galaxies (NUGA sample, cf Garcia-Burillo et al)N1961, N2782, N3147, N3368, N3627, N3718, N4321, N4569,N4579, N4736, N4826, N5248, N5953, N6574, N6951, N7217

Rest of the times, positive torques, maintain the gas in a ring

Short fueling phases, a few 107 yrs, due to feedback?Rare to see binary AGN, not fueled at the same timeDifficult to identify the driver: bars have weaken then

Star formation fueled by the torques, always associated to AGNactivity, but longer time-scales

35% showing gas accretion

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Galaxies with embedded bars, or bars/ovalsThe inner structure takes over the negative torque of the barbeyond the ILR

Galaxies with no ILR, and only one primary bar(case of NGC 3627)

65% showing no central gas accretion

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Galaxies with embedded bars, or bars/ovalsBut the gas is still stalled at an ILR ring (cf N6951, N4321..)

Galaxies with no contrasted feature towards the centerAlmost axisymmetric, without torques(case of NGC 7217, N5953..)

CONCLUSION

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Importance of gas accretion in secular evolution to replenish disks

Size of disks: non-axisymmetries redistribute matterExponential disks + radial migration, disks can triple in size

Metallicity dilution due to gas accretion, together with interactions

Warps and polar rings, when non-aligned accretion

Thick disk formation: mergers, or secular evolution?

Gas accretion in cool core clusters: inflow/outflow bubbling

Fueling of AGN: intermittent, triggered by non-axisymmetries