Transcript Evolution of disk galaxies

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
Galaxy Evolution
Hierarchical LCDM 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
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)
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/s, young “pseudo-bulges” being built
- Review by Kormendy and Kennicutt (2004)
- Case of NGC 3351
Jogee, Scoville & Kenney 2005)
NGC 3351 (Jogee, Scoville, & Kenney 2005)
Bars over the last 8 Gyr with GEMS
Q1 What fraction of disk galaxies are barred over the last 8 Gyr ?
•
Work with GEMS data in fixed rest-frame band out to z=1
Redshift
0.25<z<=0.7
0.7<z<=1.3
Filter Rest-frame
F606W
V to B
F850LP V to B
• Apply absolute mag cut to ensure completenes:
Use K-corrections based on local templates
• Identify disk galaxies quantitatively:
• Identify and
characterize
bars using
ellipse fits as
a guide to the
underlying
stellar orbits.
-19.3 out to z=0.8, or -20.6 out to z~1
(Coleman et al 1980; Dahlen et al 04)
n<2.5 (also tested C <3.4; rest frame U-V =0.8-1.2)
• Artificially redshift local galaxies to assess what is detectable by z~1 with GEMS
(Cosmological dimming, Loss in spatial resolution)
-
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
Bars and spirals in GEMS at z = 0.4-1.1 (Tback= 4.5 to 8 Gyr)
Results
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)
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-l 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%)
(Jogee & GEMS collab. 2004, ApJ)
45% of bars detected by ACS have a< 0.5”
Similar high optical fraction in Tadpole field
(Elmegreen et al 2004) & COSMOS (Sheth et al. 2004)
Obscured bars and the need for WFC3
To measure obscured bars at z>0.5, need NIR camera w/ large fov and small PSF (<0.15”)  WFC3
fstrong-total total fraction of disks with strong bars (including obscured bars)
= fraction of disks strong bars visible at optical l x correction for obscured bars
= fstrong-optical x Acorr
~ 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)
= 1.8 at z ~0
= unknown at z>0.7, but is
likely >= 1.8 given higher
SFR density
Total fraction of bright disks with strong bars, including obscured bars
at 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
Live Triaxial Potential
Analytic Triaxial Potential (El-Zant & Shlosman 2002)
Halo triaxiality increases: (b/a) of potential: 1.0  0.95
Fraction of chaotic orbits (white) increases
Berentzen et al 2006, ApJ
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)
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)
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)
Defining the z=0 point for bars with the OSUBG sample
(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 SDSS
(Barazza et al 2006, in prep) : SDSS, NYUVAC low redshift sample
z~0.035 ; -18 to -21.5 ; 5000 galaxies
Summary
Summary: Bars over the last 8 Gyr
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
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
Why is our optical bar fraction different?
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
3. 45% of bars detected by ACS have a< 0.5” and
require a small effective psf for detection.
 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))
(Jogee, Scoville, & Kenney 2005)
SF triggered when gas density
exceeds a critical density
(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/s, young “pseudo-bulge” being built
Jogee, Scoville, & Kenney 2005; Review by Kormendy & Kennicutt 2004
(Figs from Jogee, Scoville, & Kenney 2005)
Quantifying asymmetries/interaction strengths out to z=1
RF color vs Asymm
on z~1 galaxies
(CAS code; Conselice et al 2000)
Early Types : AB > 0.35
Starbursts : AB > 0.35
Defining the z=0 point for bars with SDSS
(Barazza, Jogee, et al 2006, in prep)
sdss vs osu
Deprojection/Inclination bias in “e”
B
- 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)
Bar size vs ‘disk size’ at z >0.2
- Ongoing: Apply to full sample,
using scale length or effective
radius of disk rather than a-max
of disk
z = 0.2-1.3 (Tback = 1.5--9 Gyr ) (old sample)
Bars and their impact in local galaxies
(Sakamoto et al 1999)
• Gas central concentration fcon in r<500 pc is larger in barred than unbarred spirals
fcon = [Sgas
within 500 pc] / [Sgas within (R<R25)]
(e.g., Sakamoto et al. 1999; Sheth et al. 05)
Bars and their impact in local galaxies
• Starburst/HII galaxies have a larger fraction of bars than quiescent galaxies
E12MGS (Hunt & Malkan 1999)
- 891 galaxies ; 116 Sy
- Bar + optical type from RC3
- Nuclear type from NED : Sy LINER HII normal
Fraction of galaxies with bars
- "Normal" (quiescent) : 61-68 %
- HII/Starburst
: 82-85 % ;excess
- AGN
: 61-68 % ; no excess
0=S0/a 1~Sab 3~Sbc 5~Scd 6=Sd
Bars and their impact in local galaxies
Bars may drive secular evolution along Hubble Sequence (Scd-Sb)
Sab Sa
<-------------------------------->
z>>1: mergers build BH/bulges?
SMBH—Bulge correlation
Sb
Sbc Sc Scd
Sd
< ---------------------------------
--------------
Structural/secular evolution
Nuclear cluster
No bulge
Secular building of ‘bulges’
- Bar-driven gas inflow
CN disks (high V/s), ‘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 over the last 8 Gyr from GEMS
GEMS (Galaxy Evolution from Morphology and SEDS)
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)
 [dz/(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)
Example of galaxies over z=0.7-1.0 (Tback~ 6-8 Gyr)
Characterizing bars over the last 8 Gyr with GEMS
•
Work in a fixed rest-frame band out to z=1 to minimize bandpass shifting
Redshift
0.25<z<=0.7
0.7<z<=1.3
[0.7<z<1.3
Filter Rest-frame
F606W
V to B
F850LP V to B
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
• 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
[ 3) Rest frame U-V = 0.8-1.2
(artificial simulation + visual inspection)
(broadly separate spirals from red E/S0s) ]
Ellipse fits to identify and quantify bars out to z=1
STARS
z=0.5
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]
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
z=0.66, F850LP
Class: unbarred (u)
Record disk = (e0, a0)
NB: e1<0.25
Class: unbarred (u)
Record disk = (e0, a0)
Class = Inclined = i
Class: Inclined (i) (not p1)
Record disk = (e0, a0)
Bar lifetime: What do simulations with (live) axisymm halos predict?
Early simulations: bars self-destroy from high central mass concentrations (CMCs)
(e..g., Pfenniger & Norman 1990; Norman, Sellwood, and Hassan 1996)
-
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)
If a bar is destroyed by CMC, disk left
is dynamically hot and difficult to reform
bars w/o cooling
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)
 See talks by Athanassoula, Martinez, Bournaud
time in Gyr
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?
- What drives factor of 10 decline in SFR density from z=1 to 0 >
 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)
Use 3.6 and 24 micron data for CDF-S (collaborative effort with Spitzer GTO team
(G Rieke, P. Gonzalez, C. Papovich)
Quantifying asymmetries/interaction strengths out to z=1
RF color vs Asymm
on z~1 galaxies
(Jogee et al 2004)
(CAS code; Conselice et al 2000)
Early Types : AB > 0.35
Starbursts : AB > 0.35
Asymmetry in Starburst Galaxies
AB
• 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
(Jogee et al 2003; Mobasher, Jogee et al 2003)
AR
AR
Ab >0.30 : 55% of starbursts
AR >0.30 : 40% of starbursts
A significant % of optical starburst activity is
tidally triggered.
Early Types : AB > 0.35
Starbursts : AB > 0.35