The role of cold gas

in the chemical evolution

of nearby galaxies

Tom Hughes Luca Cortese (Swinburne), Alessandro Boselli (LAM),

Guiseppe Gavazzi (Milan), Jonathan Davies (Cardiff), Veronique Buat (LAM)

The Role of Hydrogen in the Evolution of Galaxies

Kuching, 17th September 2014

Metals from stellar nucleosynthesis Expulsion of metals & unprocessed gas

Gas cools in the ISM, aided by dust Stars form in collapsing gas clouds

Dust forms in

cooling metal

rich gas

INT

ER

GA

LA

CT

IC

ME

DIU

M

The baryonic matter cycle

Lequeaux et al. 1979 Tremonti et al. 2004

•

•

Stellar mass – metallicity

>53,000 SDSS galaxies

Ma

ss

Metallicity

Stellar mass

Ox

yg

en

ab

un

da

nc

e

Some open questions

Da

ve

et

al.

20

11

Constant

No wind Slow

Conserved

• Shape

- galactic scale winds

- variable SF efficiency

- variable IMF

•

•

Some open questions

Mass Surface density

Concentration Inclination

Ha EW Colour

Tre

mo

nti

et

al.

20

04

• Shape

- galactic scale winds

- variable SF efficiency

- variable IMF

• Scatter

- most galaxy properties

do not correlate with

metallicity residuals

•

Some open questions

Mo

uh

cin

e e

t a

l. 2

00

7

• Shape

- galactic scale winds

- variable SF efficiency

- variable IMF

• Scatter

- most galaxy properties

do not correlate with

metallicity residuals

• Environment

- weak/strong dependence (see e.g. Cooper et al 2008)

- no statistical dependence

(see e.g. Ellison et al 2008)

Sk

illm

an

et

al.

19

96

Local density Local density

Hubble Type VCirc B magnitude

Role of gas content

Infer:

K-S Law (Tremonti et al. 2004),

HI Scaling relations (Zhang et al. 2009).

Sk

illm

an

et

al.

19

96

Predict: decreasing Z with increasing gas fraction μ: Z = y ln (1 / μ) (Edmunds 2001)

Observe:

in Virgo

.

Herschel Reference Survey

Sample selection criteria:

• 15 - 25 Mpc volume limit

• 2MASS KsTot ≤ 12 mag

• Galactic latitude > +55º

• Extinction AB < 0.2

Ancillary data is complete for:

• H, B & V photometry ~ stellar mass

• NUV GALEX imaging ~ SFR

• HI 21cm ~ HI gas mass

• Drift-scan spectra ~ metallicity

- magnitude- and volume-limited sample covering 323 nearby galaxies in a

range of environments, from isolated systems to Virgo cluster members

(Boselli et al. 2010).

Herschel Reference Survey

Sample selection criteria:

• 15 - 25 Mpc volume limit

• 2MASS KsTot ≤ 12 mag

• Galactic latitude > +55º

• Extinction AB < 0.2

Ancillary data is complete for:

• H, B & V photometry ~ stellar mass

• NUV GALEX imaging ~ SFR

• HI 21cm ~ HI gas mass

• Drift-scan spectra ~ metallicity

- magnitude- and volume-limited sample covering 323 nearby galaxies in a

range of environments, from isolated systems to Virgo cluster members

(Boselli et al. 2010).

Error-weighted mean oxygen abundance from combination of

strong-line metallicity calibrations and base conversions from

Kewley & Ellison (2008).

HI deficiency is:

the difference between the observed HI mass and that expected for an isolated galaxy of similar size and type.

Blue circles –

Galaxies with normal gas content

Red circles –

Gas deficient objects, i.e.

galaxies missing up to 70% of their gas compared to healthy isolated systems.

Log stellar mass Gas fraction

Oxygen a

bundance

Resid

ual abundance

(Gas-poor Gas-rich)

Scatter in M-Z relation

correlates with gas fraction.

Gas-deficient objects

typically more metal-rich.

Hu

gh

es

et

al.

20

13

Observed role of hydrogen

No significant environmental dependence,

consistent with Ellison et al. 2009 + Mouhcine et al. 2007

Log stellar mass Gas fraction

Oxygen a

bundance

Resid

ual abundance

Log stellar mass Log stellar mass

Hu

gh

es

et

al.

20

13

Effects of environment

Log stellar mass

Oxygen a

bundance

Resid

ual abundance

Log stellar mass Log stellar mass

HI-deficient select systems most perturbed by environment,

also consistent with Skillman et al. 1996, Gavazzi et al 2004.

Hu

gh

es

et

al.

20

13

Effects of environment

Hu

gh

es

et

al.

20

13

NGC 4254

metallicity profile (Skillman et al. 1996)

Ch

un

g e

t a

l, 2

00

7

Drift –scan spectroscopy only probes metallicity across observable HII regions…

Degeneracy only broken using IFU spectroscopy (e.g. SAMI, CALIFA, MaNGA)

An observational bias…?

• Does SFR govern scatter?

- a fundamental M-Z-SFR

(see e.g. Lara-Lopez et al. 2010,

Mannucci et al. 2010)

•

•

Log Mass

Oxygen a

bundance

Ma

nn

uc

ci

et

al.

20

10

Oxygen a

bundance

M-Z-SFR relation

• Does SFR govern scatter?

- a fundamental M-Z-SFR

(see e.g. Lara-Lopez et al. 2010,

Mannucci et al. 2010)

• CALIFA results

- correlation between SFR

and scatter only found when

simulating SDSS apertures (Sanzhez et al. 2013)

•

Log SFR

Log SFR Log μSFR

Resid

ual abundance

R

esid

ual abundance

Integrated HII regions

Simulated SDSS apertures

Sa

nc

he

z e

t a

l. 2

01

3

M-Z-SFR relation

• Does SFR govern scatter?

- a fundamental M-Z-SFR

(see e.g. Lara-Lopez et al. 2010,

Mannucci et al. 2010)

• CALIFA results

- correlation between SFR

and scatter only found when

simulating SDSS apertures (Sanzhez et al. 2013)

• Independent studies

- HI content drives scatter (see e.g. our work; Bothwell et al. 2013)

- SFR a proxy for gas content

(see e.g. Kahid et al. 2014)

Log SFR

Log SFR Log μSFR

Resid

ual abundance

R

esid

ual abundance

Integrated HII regions

Simulated SDSS apertures

Sa

nc

he

z e

t a

l. 2

01

3

M-Z-SFR relation

See Hughes, Cortese et al., 2013, A&A, 550, 115H

Boselli, Hughes et al., 2013, A&A, 550, 114B

• First time combined direct gas information with

metallicities from drift-scan optical spectroscopy

using new calibration techniques.

• Gas content related to scatter of M-Z relation,

environment of secondary importance.

• Future work must examine the spatially-resolved

observations to avoid potential aperture biases.

Summary