Metallicity: A Smoking Gun for Gas Flows in Mergers

Lisa Kewley - [email protected]

Lisa Kewley U. Hawaii

Margaret Geller (SAO), Betsy Barton (UC Irvine)


MotivationMotivation

Metallicity diagnosticsMetallicity diagnostics

Luminosity-Metallicity RelationLuminosity-Metallicity Relation

Central Star FormationCentral Star Formation

Blue BulgesBlue Bulges

Merger ModelsMerger Models

Conclusions & Future WorkConclusions & Future Work

SummarySummary


Effect of mergers

on metallicity?unknown

Predicted gas flows?elusive

Fabbiano et al. (2004)

MotivationMotivationFeSiMg


502 galaxies from the CfA redshift catalog (v > 2300 km/s, v < 1035 km/s, D < 77 h-1 Mpc)

Nuclear spectra for ~200 galaxies in pairs (Barton et al. 2000)

Galaxy PairsGalaxy Pairs

198 galaxies from the CfA redshift catalog

full range in Hubble type & Magnitudes in CfA survey (Jansen et al. 2000) http://cfa-www.harvard.edu/~jansen/nfgs/nfgssample.html

Field GalaxiesField Galaxies


Kewley & Dopita (2002, ApJS, 142, 35)

“R23”

Metallicity DiagnosticsMetallicity Diagnostics

Also: Pagel (1979), McCall et al. (1985), ...,Also: Pagel (1979), McCall et al. (1985), ...,Skillman et al. (1989), McGaugh (1991),...,Skillman et al. (1989), McGaugh (1991),...,Zaritsky et al. (1994), Charlot (2001), ...Zaritsky et al. (1994), Charlot (2001), ...



Kewley, Geller, & Barton (2005, AJ, 131, 2004)

Luminosity-metallicity Relation

1. shifts for close pairs



Luminosity Effect?Luminosity Effect?

close pairs

wwide pairs

NFGScz < 2300 km/s

Need 1-2 Mag rise




close pairs

wwide pairs

NFGScz < 2300 km/s

No shift in upperbound : MB

Negative shift in right bound: metallicity




R-Band Luminosity-metallicity Relation

1. still shifts for close pairs






metallicity effect?gas infall?


Central Burst Strength, SCentral Burst Strength, SRR(t)(t)

Barton, Geller & Kenyon (2003):

Stellar population synthesis models + colors + EWsassuming 2 populations (old & young)

SR(t) = current fraction of R-band light from young burst


Central Central Burst Burst

StrengthStrength

Barton, Geller & Kenyon (2003)






2. correlated with central burst strength








Blue BulgesBlue Bulges

Kannappan et al. (2003): “blue bulge parameter”

(B-R) = (B-R)outer - (B-R)inner

where (B-R)outer = (B-R) at 75% light radius

(B-R)inner = (B-R) at 1/2 light radius







3. correlated with blue bulges

Blue Bulges


Metallicity GradientMetallicity Gradient

Kewley, Geller, & Barton (2005, AJ, submitted)

Keck LRIS Spectroscopy


Metallicity GradientMetallicity Gradient


Keck LRIS Spectroscopy

See also:Li Hsin Chien’sPoster


Merger ScenarioMerger Scenario

Images Courtesy Chris Mihos








Evidence for Gas Infall


Metallicity GradientsMetallicity Gradients


Metallicity GradientsMetallicity Gradients

M101

Kennicutt, Bresolin & Garnett (2003)



Iono et al. (2004): Simulations predict:

1. Gas inflow rate ~ 7 Mo/yr 2. Gas flows within 1st 100 Myr but before disk merger

.



Iono et al. (2004): Simulations predict:

1. Gas inflow rate ~ 7 Mo/yr 2. Gas flow within 100 Myr but before disk merger

.



Assuming:1. Gas inflow rate ~ 7 Mo/yr2. Normal Spiral Metallicity gradient

.

How much infalling gas is required?



Assuming:1. Gas inflow rate ~ 7 Mo/yr2. Normal Spiral Metallicity gradient

.

How much central dilution is required? 50-60%

Merger models predict: 60% infall



Assuming:1. Gas inflow rate ~ 7 Mo/yr2. Normal Spiral Metallicity gradient 3. Central Gas Mass 108 - 109 Mo ave v. high

.

How long will it take to infall?

.



Assuming:1. Gas inflow rate ~ 7 Mo/yr2. Normal Spiral Metallicity gradient 3. Central Gas Mass 108 - 109 Mo

.

How long will it take to infall? 9x106 - 9x107 years

Merger models predict: within 1x108 years

.


New Theoretical ModelsNew Theoretical Models

Josefa Perez et al. (2006, astro-ph/0605131)

Chemical evolution model (Scannappieco et al. 2005)

CDM model (GADGET-2; Springel & Hernquist 2003)

Lower mean central (O/H) in pairs from inflows

+


Close galaxy pairs have lower than field Close galaxy pairs have lower than field central metallicitiescentral metallicities

““Smoking gun” Smoking gun” for gas infall during merger?for gas infall during merger?

Central metallicity correlates with: Central metallicity correlates with:

central burst strengthcentral burst strength blue bulgesblue bulges

Timescale consistent with current Timescale consistent with current merger simulationsmerger simulations

ConclusionsConclusions


Keck LRIS spectra of matched pair membersKeck LRIS spectra of matched pair members

Merger simulations of metallicity gradientsMerger simulations of metallicity gradients

Future DirectionsFuture Directions


Starburst99-Mappings On-LineStarburst99-Mappings On-LineL. Kewley & C. LeithererL. Kewley & C. Leitherer

Interactive web form to run modelsInteractive web form to run models

Pre-run model gridsPre-run model grids

Starburst99-Mappings Interface: http://www.stsci.edu/science/starburst99/

Mappings Interface: http://www.ifa.hawaii.edu/~kewley/Mappings


Effect of mergers

on metallicityis unknown

Fabbiano et al. (2004)

MotivationMotivationFeSiMg


Metallicity Diagnostic ComparisonsMetallicity Diagnostic Comparisons

Kewley & Ellison (2005)


Metallicity: Metallicity: Strong lines vs Auroral LinesStrong lines vs Auroral Lines

Garnett, Kennicutt, Bresolin


Classification Classification SchemeScheme








Evidence for Gas Infall

1’


Kobulnicky & Kewley (2004, ApJ, 617,240)

GOODS Survey: 0.3 < z< 1 GOODS Survey: 0.3 < z< 1


Metallicity - [NII]/HaMetallicity - [NII]/Ha

Pettini & Pagel (2004)


Metallicity DiagnosticsMetallicity Diagnostics

1.1. TheoreticalTheoretical - photoionization models - photoionization models e.g., McGaugh (1991), Kewley & Dopita (2002), e.g., McGaugh (1991), Kewley & Dopita (2002),

Tremonti et al. (2004)Tremonti et al. (2004)

2.2. EmpiricalEmpirical - fit to T - fit to Tee metallicities metallicities e.g., Pilyugin (2000), Pettini & Pagel (2004)e.g., Pilyugin (2000), Pettini & Pagel (2004)

CombinationCombination - fit to T - fit to Tee method + method + theoretical metallicitiestheoretical metallicities e.g., Denicolo, Terlevich & Terlevich (2002)e.g., Denicolo, Terlevich & Terlevich (2002)


Metallicity - [OIII]/Hb,[NII]/HaMetallicity - [OIII]/Hb,[NII]/Ha

Pettini & Pagel (2004)


Metallicity Metallicity Diagnostic Diagnostic

ComparisonsComparisons

Kewley & Ellison (2005, in prep)


Metallicity: Metallicity: Strong lines vs Auroral LinesStrong lines vs Auroral Lines

Garnett, Kennicutt, Bresolin


Kobulnicky & Kewley (2004, ApJ, 617, 240)

GOODS Survey: 0.3 < z< 1 GOODS Survey: 0.3 < z< 1


Auroral Line SaturationAuroral Line Saturation

Stasinska (2002,2005)

Documents

Metallicity: A Smoking Gun for Gas Flows in Mergers