GEMS: Evolution and Impact of Bars over 8 Gyr

Shardha Jogee

University of Texas at Austin

Collaborators

- GEMS (H.W.-Rix, M. Barden, C. Peng, C Wolf, K. Meisenheimer, E. Bell, R. Somerville, …)- GOODS (B Mobasher, C. Conselice, T. Dahlen,…) -F. Barazza, I. Marinova, I. Shlosman, I. Berentzen

Hierarchical CDM models provide good paradigm for how DM evolves on large

scales (>few 100 kpc). But numerous challenges remain…..

• How to make present-day bulgeless galaxies?

• Substructure or missing satellite problem

• Angular momentum catastrophe

• No unique and robust predictions on internal structure of galaxies drivers of SF

Galaxy Evolution

Need empirical constraints

Star formation physics + feedback

Mechanisms redistributing angular momentun in baryonic and DM components (e.g., spontaneously and tidally induced bars, interactions, dynamical friction)

Relevance/Impact of Bars

Majority of present-day spirals host stellar bars

Bars resonantly exchange angular momentum with DM halo.

Bars are most efficient way to drive gas from disk into r<1 kpc in isolated galaxies in minor mergers and early stages of major mergers (Mihos & Hernquist 95; Hernquist & Mihos 96; Heller & Shlosman

94;Naab & Burkert 01)

Bars esp. important at z<1, where minor mergers become increasingly important w.r.t major mergers (dominate at z>2)

(Conselice 2003)

NGC 3351 (Jogee, Scoville, & Kenney 2005)

Bars increase central gas concentration, fuel central starbursts, build disky bulges

* Gas concentration larger in barred than unbarred galaxies (Sakamoto et al 1999; Sheth et al 2005)

* In central r<500 pc of nearby barred galaxies

Gas makes up 10 to 30% of dynamical mass

Gas densities reaches several 1000 Mo pc-2 SFR=3 to 15 Mo yr-1 disky, high v/, young “pseudo-bulges” being built

- Review by Kormendy and Kennicutt (2004)

- Case of NGC 3351Jogee, Scoville & Kenney 2005)

Q1 What fraction of disk galaxies are barred over the last 8 Gyr ?

Bars over the last 8 Gyr with GEMS

• Work with GEMS data in fixed rest-frame band out to z=1

Redshift Filter Rest-frame

0.25<z<=0.7 F606W V to B

0.7<z<=1.3 F850LP V to B

• Apply absolute mag cut to ensure completenes: -19.3 out to z=0.8, or -20.6 out to z~1

Use K-corrections based on local templates (Coleman et al 1980; Dahlen et al 04)

• Identify disk galaxies quantitatively: n<2.5 (also tested C <3.4; rest frame U-V =0.8-1.2)

• Identify and characterize bars using ellipse fits as a guide to the underlying stellar orbits.

-

From z=0

To z=0.6 (R) z=1 (B)

Strong (e>=0.4) bars can be reliably recovered

Weak bars and/or small a<1.0 kpc bars are often not detectable

• Artificially redshift local galaxies to assess what is detectable by z~1 with GEMS (Cosmological dimming, Loss in spatial resolution)

Bars and spirals in GEMS at z = 0.4-1.1 (Tback= 4.5 to 8 Gyr)

Result from ¼ GEMS : fraction of bright disks with strong (e >0.35) optically visible bars stays ~30% from present-day out to Tback of 2-6 and 6-8 Gyr . No drastic decline at z>0.7.

Redshift Tback Filter Rest- fstrong-optical

--------------------------------------------------------------------OSU sample z~0 B B ~30% 0.25<z<=0.7 2-6 Gyr F606W V to B fopt = 24-30 %

0.7<z<=1.1 6- 8 Gyr F850LP V to B fopt = 25-29% (cf 5%)

Earlier HDF studies WFPC2: dramatic decline at z> 0.7 in the fraction of disks w/ optically-visible bars

30% at z~0 to below 5% at z>0.7 (Abraham et al. 99)

NIC3: detected fraction =5%, but only large bars (1.4”=12 kpc) recovered (Sheth et al 2003)

Similar high optical fraction in Tadpole field (Elmegreen et al 2004) & COSMOS (Sheth et al. 2004)

45% of bars detected by ACS have a< 0.5”

(Jogee & GEMS collab. 2004, ApJ)

Results

~ 30% at z ~0 ~ 30% at z = 0.2-0.7 (Tback= 2-6 Gyr)

at z = 0.7-1.0 (Tback= 6-8 Gyr)

Obscured bars and the need for WFC3

fstrong-total total fraction of disks with strong bars (including obscured bars)

= fraction of disks strong bars visible at optical x correction for obscured bars

= fstrong-optical x Acorr

= 1.8 at z ~0 = unknown at z>0.7, but is likely >= 1.8 given higher SFR density

To measure obscured bars at z>0.5, need NIR camera w/ large fov and small PSF (<0.15”)

WFC3

Total fraction of bright disks with strong bars, including obscured barsat z> 0.7is similar or HIGHER than at z~0

Q2 What do bars imply re. the triaxiality of DM halos in z~1 disks

3-D simulations of barred disks embedded in live triaxial halos (by Berentzen & Shlosman)

The triaxial concentrated DM halo tends to rapidly destroy the bar Bars can only survive if the triaxiality & prolatenes of the DM halo is strongly diluted

Halo triaxiality increases: (b/a) of potential: 1.0 0.95Fraction of chaotic orbits (white) increases

Analytic Triaxial Potential (El-Zant & Shlosman 2002)

Live Triaxial Potential Berentzen et al 2006, ApJ

Results consistent with dissipative cosmological simulations of (DM halo +baryons) collapse of baryons into a disk ‘washes out ’ the triaxiality of the DM halo (Kazantzidis et al. 2004 ; Springel et al 2003; Dubinski 1994)

c/a and b/a rise from 0.4 to 0.9

Results consistent with measure shape of DM halo for the Milky Way shape~ spherical : c/a >0.7 (density) , b/a ~1 (Helmi 2004)

Observed large fraction of strong bars out to z~0.2-1.0 (Tback ~2-8 Gyr) suggests that DM halos of disks at z~0.2-1.0 have a low triaxiality with (b/a) > 0.9 (potential)

(Berentzen, Shlosman, & Jogee 2006)

Q3. Are bars long-lived?

• Competing scenarios on lifetime and evolution of bars

S1: Bars are long-lived with lifetimes >> 2 Gyr (for realistic CMC) (e.g., Martinez-Valpuesta & Shlosman 2004; Shen & Sellwood 2004; Debattista et al 2005)

S2: Bars dissolve in t< 2 Gyr due to L transferred to stars in bar from *large* gas inflows (e.g., Bournaud & Combes 2005)

• Empirical constraint 1 : optical fraction of strong bars~30% at 3 Tback= 0,2-6,6-8 Gyr

Simplest scenario consistent with this constraint = S1

S2 possible, but requires fine-tuning of destruction rate with formation rate.

Empirical constraint 2: structural properties (size, strengths) of bars at these epochs

Bars strength at z=0.2-0.7 versus z=0.7-1

Bars sizes at z=0.2-0.7 versus z=0.7-1.0

Bars sizes at z~0 from OSUBGS (Marinova et al 2006, in prep)

K-S tests on 2 redshift slices yield P=0.2 -0.5 = inconclusive w.r.t. evolution

To draw firm conclusions, must extend study from ¼ GEMS sample (2000 galaxies) to full GEMS sample (8500) add in z= 0 point for bars from OSUBG Survey (Marinova et al 2006, in prep) from SDSS (Barazza et al 2006, in prep)

(Marinova et al 2006, in prep)OSUBG, 180 x 3 images (BHK)B<12, MB = -18.5 to -23

Defining the z=0 point for bars with the OSUBG sample

(Barazza et al 2006, in prep) : SDSS, NYUVAC low redshift sample z~0.035 ; -18 to -21.5 ; 5000 galaxies

Defining the z=0 point for bars with SDSS

Summary

1) What fraction of disk galaxies are barred over the last 8 Gyr ?

The fraction of luminous disks with strong (e >0.35)

optically-visible bars remains ~ 30% from the present-day out to z~1 (Tback~8 Gyr)

(optically-visible + obscured) bars at z>0.7 is at least as high as at z~0

Summary: Bars over the last 8 Gyr

2) What do bars imply about the triaxiality of DM halos in disks at z~1? Abundance of strong bars at z~ 0.2-1.0 suggests DM halos have low triaxiality (b/a > 0.9)

3) Bar lifetimes? Simplest scenario consistent with data : bars are long-lived with lifetimes >> 2 Gyr

4) Upcoming attractions

- What % of SFR density out to z ~1 is bar-induced?

- Are bars building pseudo-bulges at z~0.2—1.0 would worsen problem of bulgeless galaxies

- Nail z=0 point for bars with SDSS

1. Small number statistics/cosmic variance : only 46 galaxies used by A99

2. Methodology

A99 used e at 85% of max SB rather than global max in e over PA plateau to identify bar may miss bar entirely

Why is our optical bar fraction different?

PSF for ACS vs WFPC2 vs NIC2 = 0.07”, 0.15”, >0.25”

4. Bandpass shift at z >=0.8 (WFPC2 F814W vs ACS F850LP)

5. Sensitivity to the red is higher for GEMS (F850LP+ACS) than (F814W+ WFPC2))

3. 45% of bars detected by ACS have a< 0.5” and require a small effective psf for detection.

(Jogee, Scoville, & Kenney 2005)

SF triggered when gas density exceeds a critical density (Jogee, Scoville, & Kenney 2005)

(Figs from Jogee, Scoville, & Kenney 2005)

Bars increase central gas concentration, fuel central starbursts, build disky bulges

* Gas concentration larger in barred than unbarred galaxies (Sakamoto et al 1999; Sheth et al 2005)

* In central r<500 pc of nearby barred galaxies

Gas makes up 10 to 30% of dynamical mass

Gas densities reaches several 1000 Mo pc-2 SFR=3 to 10 Mo yr-1 (Jogee, Scoville & Kenney 2005)

* In central r<500 pc of z~0 barred galaxies, see

disky, high v/, young “pseudo-bulge” being built Jogee, Scoville, & Kenney 2005; Review by Kormendy & Kennicutt 2004

Starbursts : AB > 0.35Early Types : AB > 0.35

Quantifying asymmetries/interaction strengths out to z=1

RF color vs Asymm on z~1 galaxies

(CAS code; Conselice et al 2000)

(Barazza, Jogee, et al 2006, in prep) sdss vs osu

Defining the z=0 point for bars with SDSS

Deprojection/Inclination bias in “e”

- Must deproject radial profile to derive intrinsic strength e and size a of bars - Will not change results statistically as no correlatoion between e vs i (for i<60)

B

Bar size vs ‘disk size’ at z >0.2

z = 0.2-1.3 (Tback = 1.5--9 Gyr ) (old sample)

- Ongoing: Apply to full sample, using scale length or effective radius of disk rather than a-max of disk

• Gas central concentration fcon in r<500 pc is larger in barred than unbarred spirals

fcon = [gas within 500 pc] / [gas within (R<R25)] (e.g., Sakamoto et al. 1999; Sheth et al. 05)

(Sakamoto et al 1999)

Bars and their impact in local galaxies

Fraction of galaxies with bars

- "Normal" (quiescent) : 61-68 %

- HII/Starburst : 82-85 % ;excess

- AGN : 61-68 % ; no excess

E12MGS (Hunt & Malkan 1999)

- 891 galaxies ; 116 Sy

- Bar + optical type from RC3

- Nuclear type from NED : Sy LINER HII normal

0=S0/a 1~Sab 3~Sbc 5~Scd 6=Sd

• Starburst/HII galaxies have a larger fraction of bars than quiescent galaxies

Bars and their impact in local galaxies

Sab Sa Sb Sbc Sc Scd Sd

<--------------------------------> < --------------------------------- --------------

z>>1: mergers build BH/bulges? Structural/secular evolution Nuclear cluster

SMBH—Bulge correlation No bulge

Bars may drive secular evolution along Hubble Sequence (Scd-Sb)

Secular building of ‘bulges’

- Bar-driven gas inflow CN disks (high V/), ‘pseudo-bulge’ - Bending instabilites in disk - Vertical ILRs in bars

( See Friedli & Benz 1993; Kormendy 1993; Kormendy & Kennicutt 2004, ARAA; Athanassoula 2005)

Bars and their impact in local galaxies

)

Do bars fuel AGN?

No/weak correlation between bars and Seyferts (Regan et al 1997; Knapen et al 2000; Laurikainen et al 2004)

Angular Momemtum Problem: Bar only drive gas to 100 pc scale where L is 104 too high to feed BH. Nuclear mechanism needed

Different lifetimes: Bars vs AGN

Sy and QSO cases may be very different

Seyferts: 10-2 Mo yr-1 over 108 yrs

few x 106 Mo = few % of CN gas

QSOs: 10-100 Mo yr-1 over 108 yrs

109-1010 Mo

Bars and their impact in local galaxies

Bars over the last 8 Gyr from GEMS

Largest area 2-filter imaging survey with HST (Rix et al. 2004)

Area : 30’x30’ = 120 x HDF = 78 x HUDF = 5 x GOODS-S

Filters : F606W (V) , F850LP (z) (26.8, 25.7 AB mag); 0.07”

Accurate redshifts from Combo-17 (Wolf et al. 2004)

z/(1+z) ] ~ 0.02 (R<24 Vega z=0.2-1.2)

X-ray, Radio, IR, optical coverage (CXO ATCA, VLA, Spitzer, ESO)

30’

UBVRI + 12 medium-width

GEMS: 9000 galaxies over z=0.2-1.1 (Tback~ 2-8 Gyr, Age =40% of present)

GEMS (Galaxy Evolution from Morphology and SEDS)

Example of galaxies over z=0.7-1.0 (Tback~ 6-8 Gyr)

• Work in a fixed rest-frame band out to z=1 to minimize bandpass shifting

Redshift Filter Rest-frame

0.25<z<=0.7 F606W V to B

0.7<z<=1.3 F850LP V to B

[0.7<z<1.3 F606W UV]

• Apply absolute magnitude cut to ensure completeness out to z~1

Use K-corrections based on local Scd templates (Coleman et al 1980; Dahlen et al 04)

Cut off at Mv < -19.3 : complete out to z~0.8. Gives range= -19.3 to -23.8 similar to OSUBG z~0 survey use to define z=0 bars

Cut off at Mv < -20.6 : complete out to z~1.0

Characterizing bars over the last 8 Gyr with GEMS

-

• Identify disk galaxies in a quantitative way: 3 methods

Optical Bar fraction = (No of barred disks /Total no of disks)

1) Single-component Sersic fit n< 2.5 (artificial simulation + visual inspection)

2) CAS concentration index C < 3. 4 (artificial simulation + visual inspection)

[ 3) Rest frame U-V = 0.8-1.2 (broadly separate spirals from red E/S0s) ]

Ellipse fits to identify and quantify bars out to z=1

1) Ellipse fits act as guide to underlying stellar orbit [automated, iterative] 85,000 fits (8500 galaxies ; up to 100 fits per galaxy) 2) Classify best fit: Inclined, Barred, Unbarred, etc Inclined: i>60 deg reject from sample Barred: [Bar: e rises to a global max > 0.25, plateau in PA] + [Disk: e drops by >= 0.1 + PA changes]

STARS

z=0.5

Class = barred = b

z=0.24, F850LP

Class: Primary bar (p1 or b1)

Record disk = (e0, a0) bar = (e1, a1)

NB: Short bar; Isophotal twist for spiral arms; Disk

Class = Unbarred = u

Class: unbarred (u) Record disk = (e0, a0)

NB: e1<0.25 z=0.66, F850LP

Class: unbarred (u) Record disk = (e0, a0)

Class = Inclined = i

Class: Inclined (i) (not p1)

Record disk = (e0, a0)

-

Later simulations: bars quite robust! Resonant interaction with live DM halo can strengthen bar (e.g., Athanassoula 2002; 2003)

With realistic CMCs and short timestep: bars hard to destroy (Shen & Sellwood 2004)

Bars long-lived over Hubble time (e.g., Martinez-Valpuesta & Shlosman 2004 + 2005 in prep)

Bar lifetime: What do simulations with (live) axisymm halos predict?

See talks by Athanassoula, Martinez, Bournaud time in Gyr

Early simulations: bars self-destroy from high central mass concentrations (CMCs) (e..g., Pfenniger & Norman 1990; Norman, Sellwood, and Hassan 1996)

Recurrent destruction/reformation of bars via gas accretion? Bar destroyed in few Gyr, not by CMCs, but by transfer of L from large amounts of gas inside CR to bars (Bournaud & Combes 2004)

If a bar is destroyed by CMC, disk left is dynamically hot and difficult to reformbars w/o cooling

What Next?

Ongoing Work

How do bar relate to host galaxy properties?

Compare SFR of barred vs unbarred galaxies at z=1 (jn progress)

- Do barred disks have excess SFR compared to unbarred ones?

change in rate of major merger (x) decline in gas accretion rate from minor merger decline in gas accretion rate from cosmological filaments changes in internal drivers of SF (e.g., bars which fuel CN starbursts)

- What drives factor of 10 decline in SFR density from z=1 to 0 >

Use 3.6 and 24 micron data for CDF-S (collaborative effort with Spitzer GTO team (G Rieke, P. Gonzalez, C. Papovich)

Starbursts : AB > 0.35Early Types : AB > 0.35

Quantifying asymmetries/interaction strengths out to z=1

(Jogee et al 2004)

RF color vs Asymm on z~1 galaxies

(CAS code; Conselice et al 2000)

• High AB (>0.3) Starbursts:55 %; Late: 20% Early: 12%

• K-S test on AB Starbursts vs Early type: 1e-10 Starbursts vs Late type : 3e-4

AR

Ab >0.30 : 55% of starbursts AR >0.30 : 40% of starburstsA significant % of optical starburst activity is tidally triggered.

Asymmetry in Starburst Galaxies

AB

AR

(Jogee et al 2003; Mobasher, Jogee et al 2003)

Early Types : AB > 0.35

Starbursts : AB > 0.35