Gas s In Inflo flow and nd Sec ecula ular r Evoluti lution n - - PowerPoint PPT Presentation

Gas s In Inflo flow and nd Sec ecula ular r Evoluti lution n in in Disk isk Gala laxie xies s

Michael Regan

Mergers of disks galaxies can form ellipticals

Dubinski 2005

The time of mergers is past.

Current and future galaxy evolution will be dominated by internal processes.

Gas loses angular momentum to the stars and flows inward Leads to gas in the center and the formation of a “pseudo-bulge” (Kormendy & Kennicutt 2004) Bars driven inflow is the fastest

Bar driven mass inflow affects galaxy evolution several different ways.

Providing fuel for nuclear starbursts and AGN(?)

(Shlosman, Frank, & Begelman 1989; Heller & Shlosman 1994)

Altering radial chemical gradients (Roy & Belley 1993; Friedli,

Benz, & Kennicutt 1994; Martin & Roy 1994)

Increasing the central mass concentration

Bar destruction (Friedli & Benz 1993; Norman, Sellwood, & Hasan 1996, Shein &

Sellwood 2004)

Bulge formation (Norman et al 1996)

A Pseudo-bulge is not a mini-elliptical but is really more like a disk.

A light profile that is less steep than a r ¼ law A high rotational velocity compared to an elliptical

How bar characteristics affect mass inflow (Regan & Teuben 2004) How and why nuclear rings form (Regan &Teuben 2003) Kinematic observations of gas flow in barred galaxies Central gas concentrations and pseudo-bulges

How bar characteristics affect mass inflow (Regan & Teuben 2004) How and why nuclear rings form (Regan &Teuben 2003) Kinematic observations of gas flow in barred galaxies Central gas concentrations and pseudo-bulges

We performed hydrodynamic modeling of gas flow in a barred potential. (Regan & Teuben

2003, 2004)

Cylindrical coordinate system

Cells range from 2x2pc at 100 pc radius to 100x100pc at 5 kpc.

Three free parameters were varied:

Central Mass Concentration [Bulge to Disk ratio](6 values) Bar Quadrupole Moment [Mass in the bar](5 values) Bar Axis Ratio (5 values)

Hydrodynamic simulation shows gas flow in a barred potential

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 1.5

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 2.5

Bar Axis Ratio = 2.5

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 3.5

Bar Axis Ratio = 3.5

Inflo Inflow rate rate to to 100pc 100pc radius radius Inflo Inflow rate rate to to inne inner r Kpc pc Bar Axis Ratio = 1.5 Centra entral Mass Mass Conce

• ncentra

ratio ion Bar ar Strengt Strength

Only when nuclear rings form is there significant inflow.

Regan & Teuben 2004

Inflo Inflow rate rate to to 100pc 100pc radius radius Inflo Inflow rate rate to to inne inner r Kpc pc Centra entral Mass Mass Conce

• ncentra

ratio ion Bar ar Strengt Strength

Only when nuclear rings form is there significant inflow.

Bar Axis Ratio = 2.5

Regan & Teuben 2004

Inflo Inflow rate rate to to 100pc 100pc radius radius Inflo Inflow rate rate to to inne inner r Kpc pc Centra entral Mass Mass Conce

• ncentra

ratio ion Bar ar Strengt Strength

Only when nuclear rings form is there significant inflow.

Bar Axis Ratio = 3.5

Regan & Teuben 2004

How bar characteristics affect mass inflow (Regan & Teuben 2004) How and why nuclear rings form (Regan & Teuben 2003) Kinematic observations of gas flow in barred galaxies Central gas concentrations and pseudo-bulges

Why do they form?

Trapped between the Inner Lindblad Resonances (ILRs) (Combes 1996;

Buta & Combes 1996)

Circular orbits are stable (Shlosman, Begleman, & Frank 1990) Remnant of nuclear starburst (Kenney, Carlstrom, & Young 1993)

Where do they form?

Peak of rotation curve Peak of W-k/2 curve (Piner, Stone, & Teuben 1995) At the Inner Inner Lindblad Resonance (IILR) when there are two or at the ILR if only one (Buta & Combes 1996)

There are many ideas that try to explain nuclear ring formation.

The epicyclic orbits are nearly circular orbits.

When the radial and angular frequencies are multiples you get a resonance.

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 1.5

ILRs are only weakly correlated with nuclear rings.

Regan & Teuben 2003

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 2.5

ILRs are only weakly correlated with nuclear rings.

Regan & Teuben 2003

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 3.5

ILRs are only weakly correlated with nuclear rings.

Regan & Teuben 2003

Bar Orbit Theory

X1 orbits form the backbone of the bar.

There are also perpendicular orbits(x2) that may be stable.

The perpendicular orbits (x2 Orbits) are related to nuclear rings.

Bar dust lanes and x2 orbit are strongly correlated (Athanassoula 1992)

Because nuclear rings and bar dust lanes are also strongly correlated expect to see x2 and nuclear ring correlation.

Each potential we found the existence and extent of x2 orbits.

Central Mass Concentration

Bar Strength

X2 orbits Bar Axis Ratio = 1.5

The nuclear ring forms at the largest x2 orbit.

Regan & Teuben 2003

Central Mass Concentration

Bar Strength

X2 orbits Bar Axis Ratio = 2.5

The nuclear ring forms at the largest x2 orbit.

Regan & Teuben 2003

Central Mass Concentration

Bar Strength

X2 orbits Bar Axis Ratio = 3.5

The nuclear ring forms at the largest x2 orbit.

Regan & Teuben 2003

Nuclear rings form due to the intersection of gas on x1-like and x2-like streamlines.

Gas cannot exist on both x1-like and x2-like streamlines in the same region Gas appears to favor the x2-like streamlines

Consistent with van Albada & Sanders (1982)

Gas prefers more circular orbit

X2 orbits have lower energy

Nuclear ring is not in equilibrium. It’s the orbits, stupid.

How bar characteristics affect mass inflow (Regan & Teuben 2004) How and why nuclear rings form (Regan & Teuben 2003) Kinematic observations of gas flow in barred galaxies Central gas concentrations and pseudo-bulges

When the gas is in circular orbits the “Spider” diagram is symmetrical.

Minor Axis Major Axis

The Ha gas in NGC 1530 is clearly not rotating in circular orbits.

Fabry-Perot observations of NGC 1530

Strong shock along dust lanes Isovelocity parallel in nuclear region Kink along spiral arms Kinematic major axis shifted

NGC 1530 I-band

Regan, Vogel & Teuben 1997

The hydrodynamic models are a good match to the observations.

Only Circular Motion Observed Velocities Hydro model velocity field

The molecular gas (CO) in NGC 1530 shows the fast jumps on the bar dust lanes.

Reynaud & Downs 1998

The CO in NGC 2903 shows strong velocity gradients.

Regan, Sheth & Vogel 1999 Regan, Sheth & Vogel 1999

The CO emission in NGC 3627 also shows this with gas at systemic on the major axis.

Regan, Sheth & Vogel 1999

How bar characteristics affect mass inflow (Regan & Teuben 2004) How and why nuclear rings form (Regan & Teuben 2003) Kinematic observations of gas flow in barred galaxies Central gas concentrations and pseudo-bulges

OVRO and BIMA SONG results showed evidence for a central excess of molecular gas. (Sakamoto et al

1999, Regan et al 2001, Sheth et al 2005) Regan et al 2001

CO maps suffer from many limitations that limit their usefulness in studying ISM radial profiles.

CO Interferometric maps have problems: limited FOV missing atomic gas surface brightness cutoff CO/H2

Spitzer Space Telescope

Spitzer Infrared Nearby Galaxies Survey (SINGS) Science Core

Characterize star formation in 75 nearby galaxies

IRAC on the Spitzer Space Telescope observes emission from both stars and dust.

Stellar photospheres

In M51 the Channel 1 (3.6 mm) emission looks like dust free stellar emission.

I-band

In M51 the Channel 1 (3.6 mm) emission looks like dust free stellar emission.

3.6mm

In M51 the dust extinction shows a similar morphology to the 8 mm emission.

I-3.6mm color map

In M51 the dust extinction shows a similar morphology to the 8 mm emission. 8mm

Spitzer IRAC 8mm emission provides a new probe of the ISM. 8 mm flux CO flux

Regan et al. 2006

Both NGC 3351 and NGC 3627 show central excesses in CO and 8mm.

Barred Barred 8mm Surface Brightness CO Surface Brightness CO – 8mm Surface Brightness

Regan et al. 2006

Only NGC 5055 does not show an excess in the 8mm emission.

Barred 8mm Surface Brightness CO Surface Brightness CO - 8mm Surface Brightness CO relatively brighter in the nucleus

Regan et al. 2006

Only NGC 6946 shows an excess in the central 8mm emission.

Barred 8mm Surface Brightness CO Surface Brightness CO – 8mm Surface Brightness

Regan et al. 2006

For each galaxy we measure two quantities.

The central gas concentration from 8mm SINGS images How bulge-like is the central light, Sersic index from 3.6 mm SINGS

High central concentrations of 8 micron PAH emission is strongly correlated with pseudobulges

Pseudobulges Classical bulges Central gas concentration

Fornax A NGC 1316

JWST will open a new era in PAH observations.

The future of millimeter astronomy is CARMA and ALMA.

The future of millimeter astronomy is CARMA and ALMA.

Conclusions

Only when nuclear rings form is there significant inflow. Nuclear rings form at the largest x2 orbit. It’s the orbits not the resonances Models agree with the observed gas kinematics. Observed central concentrations are correlated with pseudo-bulge light profiles.

X1 rings form at the largest non-looping x1

• rbit

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 1.5

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 2.0

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 2.5

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 3.0

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 3.5

Central Mass Concentration

Bar Strength

Bar Axis Ratio = 4.0

The Ring in NGC 6012 is an X1 ring

B-I I Band