HL Galaxy Metabolism

Galaxy Ontogeny : 23 Jun 2009

Spitzer LVL Luminosity- and Mass-Metallicity Relationsfor Star-Forming Dwarf Galaxies in the Local Volume

“Galaxy Metabolism”, Sydney - 23 June 2009

• Henry Lee (Gemini Observatory)

• Liese van Zee (Indiana University)

• Evan Skillman (University of Minnesota)

• Janice Lee (Carnegie Observatories)

• Rob Kennicutt (Cambridge University)

• and the LVL Team

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Pre-lunch themes

“Ingestion, digestion, excretion”

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Pre-lunch themes


• e.g., Heavens, Noeske, Hopkins :★ SFR density maximum at z ~ 1★ SFH of galaxies are mass-dependent (“downsizing”)

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Pre-lunch themes


• e.g., Heavens, Noeske, Hopkins :★ SFR density maximum at z ~ 1★ SFH of galaxies are mass-dependent (“downsizing”)

“A Nurturing Environment”

• Cole : “free-range, organic, pesticide-free (galaxies)...”

• e.g., Cooper :★ Some scatter in high-mass M-Z (SDSS T04) correlated with

local environment

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Why low-mass galaxies are important

• Most abundant galaxy-type : “building blocks” ?• Representative of conditions present in early universe ?• Detailed SFHs from CMDs and resolved stellar populations• Ongoing assembly in MW, M31 : stellar-streams, new dwarfs ...• Galactic archaeology : oldest, lowest-Z stars• ISM metallicity evolution tied to dust evolution• Possible candidate-hosts to distant gamma ray bursts

• e.g., Bland-Hawthorn, Karlsson, Cole, Guhathakurta, Zucker, Yeh, Lopez-Sanchez, Levesque, Muller, ...

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• Nearest dwarfs show great diversity in properties & SFH• Despite low-M, dwarfs sufficiently robust to form stars steadily

• Evolution a combination of low-SF + metals-loss ?• Can environment hasten the evolution of low-M galaxies?

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• Nearest dwarfs show great diversity in properties & SFH• Despite low-M, dwarfs sufficiently robust to form stars steadily

• Evolution a combination of low-SF + metals-loss ?• Can environment hasten the evolution of low-M galaxies?

Detailed studies of nearby dwarf galaxies help tie down a picture of galaxy evolution at low-M and at low-z.

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“Personal diets (& lunch with friends)”

• Processes associated with galaxy assembly

✴ Conversion of gas into stars ? Galactic winds ?✴ At given epoch, SFH & gas flows affect mass and metallicity

✴ Luminosity-metallicity (L-Z) commonly used as proxy for mass-metallicity (M-Z) ...

✴ L-Z stronger correlation than vs. Mdyn, vs MHI

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L-Z for Nearby Dwarf Galaxies

• Gas-rich galaxies : ✴ Lequeux et al. 1979✴ Skillman et al. 1989✴ Zaritsky et al. 1994✴ Richer & McCall 1995✴ Garnett 2002✴ HL et al. 2003✴ van Zee et al. 2006✴ HL et al. 2006

H. Lee et al. 2006 (N=27)

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L-Z & M-Z Relations

• Collections of galaxies at z > 1 :✴ e.g., Perez-Gonzalez et al. 2003;

Savaglio et al. 2005; Erb et al. 2006; Maiolino et al. 2008; Rodrigues et al. 2008; Hayashi et al. 2008; Perez-Montero et al. 2008; Lamareille et al. 2008; note also Monday’s talks ...

• Recent models :✴ e.g., Brooks et al. 2007; Cid

Fernandes et al. 2007; Davé & Oppenheimer 2007; De Rossi et al 2007; Köppen et al. 2007; Ellison et al. 2008; Erb 2008; Baldry et al. 2008; Bertone et al. 2008; Bovil & Ricotti 2008; Vale Asari et al. 2009; ...

Mannucci & Maiolino 2008

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Why 3.6, 4.5 µm

• Near-infrared : 1-5 µm✴ tracer of underlying stellar mass✴ minimize extinction by dust✴ minimize how light from recent SF affects L, Mstar/L✴ contributions by PAHs or hot dust not significant

(e.g., Jackson et al. 2006)

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Why 3.6, 4.5 µm

Galliano et al. 2005

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Why 3.6, 4.5 µm

1 µm 10 µm

stars

PAHs

VSGs BGs

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Why 3.6, 4.5 µm

1 µm 10 µm

stars

PAHs

VSGs BGs

3.6+

4.5µm

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Local Volume Legacy Survey : D < 11 Mpc (z < 0.003)

J. Lee et

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UGC 5829 (DDO 84); Dale et al. 2009

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UGC 8320 (DDO 168)Halpha3.6 µm24 µm

Dale et al. 2009

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The numbers, before plots

• B, J, H, K, [3.6], [4.5] luminosities : Dale et al. 2009✴ Stellar masses, using Bell & de Jong 2001✴ Different “combinations” for Mstar vary by ~0.2 dex

• ~50 dwarf irregular galaxies with reliable metallicities✴ [O III] 4363 measurements✴ Temperatures and direct measures of (O/H)

• M-Z, with M = Mstar commonly seen in models

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The numbers, before plots

• B, J, H, K, [3.6], [4.5] luminosities : Dale et al. 2009✴ Stellar masses, using Bell & de Jong 2001✴ Different “combinations” for Mstar vary by ~0.2 dex

• ~50 dwarf irregular galaxies with reliable metallicities✴ [O III] 4363 measurements✴ Temperatures and direct measures of (O/H)

• M-Z, with M = Mstar commonly seen in models

• Dekel & Silk (1986); Dekel & Woo (2003):✴ Z ∝ Ln, where n = 0.3 to 0.4✴ log Z ~ m log L, where m = 0.12 to 0.16

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L-Z relation, B

HL et al., in prep.

solar

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λ a b R σ

B -0.149 5.67 -0.80 0.15

J -0.147 5.44 -0.81 0.14

H -0.156 5.21 -0.77 0.16

K -0.152 5.24 -0.75 0.17

[3.6] -0.135 5.53 -0.85 0.14

[4.5] -0.132 5.36 -0.84 0.14

12+log(O/H) = a M! + b

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Observed M-Z : Mstar < 1010 Msun

HL et al., in prep.

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Observed M-Z : Mstar < 1010 Msun

HL et al., in prep.

Z ∝ Ln ∝ Mstarn, n = 0.3-0.4

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Metals loss (1)

Tremonti et al. 2004 Simple model for chemical evolution:

ZO = yO ln (1 + Mstar/Mgas)

yeff = ZO / ln (1 + Mstar/Mgas)

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Metals loss (1)

Tremonti et al. 2004HL et al, in prep.

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Metals loss (1)

Tremonti et al. 2004HL et al, in prep.

50% loss

90% loss

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mass-dependent SF efficiencycf. Baldry et al. 2008

Z = -y ln(μ) = -y ln(Mgas/Mb)

ε ≡ Mstar/Mb = 1 - Mgas/Mb

= 1 - exp(-Z/y)

ε = M/(M+M0) * (ε0-ε1)+ ε1

ε1 ~ 0.01-0.1ε0 ~ 0.8log(M0/Msun) ~ 109.6

Grazing (2)

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Consumibles• Spitzer Local Volume Legacy Survey :

✴ providing uniformity in galaxy L (and SF measures)✴ high-quality (O/H) from measured temperatures

• L-Z with N=50 : B, J, H, K, [3.6], [4.5] :✴ slope decreases a little with increasing wavelength✴ dispersion not significantly different from optical to NIR

• M-Z with Mstar derived at each wavelength✴ M-Z from B to [4.5] are indistinguishable✴ extending SDSS M-Z down to ~106.5 Mstar

• Mass-dependent SFE (“grazing”) & modest winds can account for L-Z, M-Z for dwarfs (Mstar < 1010 Msun)

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