Gas in local galaxies and beyond with ALMAAlberto D. BolattoUniversity of Maryland

How are galaxies put together?

Salim et al. (2007),Kauffmann et al. (2003)

• Two groups: red and dead, and blue and star-forming• Star formation activity is related to the presence (or absence) of gas• What are the relevant physical processes?

NUV-

r(S

SFR)

Mr (stellar mass)

green valley

red sequence

blue sequence

HI H2SFR

UV, X-rays, cosmic rays

mechanical feedback

metals, H, dust

accretion

n

turbulenceinstabilities

gravity

ther

mod

ynam

ics,

chem

istry

The importance of ALMA: star formation on galaxy scales

diffuse phase

dense phase

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

molecular gas

dust continuum

gas temperature

high resolution velocity field, shock tracers

many molecules

rotation, velocity dispersion

multiline excitation

high resolution velocity field

cooling transitions

magnetic fieldALM

Apolarization

HI H2SFR

UV, X-rays, cosmic rays

mechanical feedback

metals, H, dust

accretion

n

turbulence

gravity

ther

mod

ynam

ics,

chem

istry

diffuse phase

dense phase

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

ALMA

molecular gas

dust continuum

gas temperature

high resolution velocity field, shock tracers

many molecules

rotation, velocity dispersion

multiline excitation

high resolution velocity field

cooling transitions

instabilitiesmagnetic

fieldALMApolarization

The importance of ALMA: star formation on galaxy scales

The Star Formation Law

Kennicutt (1998)Global correlation

• Relation between gas (volume) density and star formation activity (Schmidt 1959)

Σ SFR α Σ (HI+2H2)1.4

Genzel et al. (2010)

NGC 4579

NGC 4254

NGC 3184

Molecular GasPeak CO intensityFrom HERACLES

Atomic GasVLA 21cm data THINGS +

new & archival

KinematicsHere from HI line

Also from COOld Stars

Near infrared intensityFrom SINGS and LVL

Recent Star FormationComposite of FUV (GALEX),

mid-IR (SINGS/LVL), and Hα (SINGS/LVL)

AHERACLES (A. Leroy)

CARMA STING (Survey Towards IR-bright Nearby Galaxies)

• BIMA SONG (Helfer, Wong, et al.)• OVRO MAIN (Baker, Jogee, et al.)• PdBI NUGA (Garcia-Burillos et al.)• CARMA-Nobeyama (Koda et al. )

Sample sizes of 10-40, with substantial overlap

Molecular gas to star formation

Bigiel et al. (2011)

Rahman et al. (in prep.)ALMA will allow us to substantially

improve sample sizes, reduce biases in galaxy types, and explore the low surface brightness regime

Molecular gas or dense gas?

• We know that star formation is, globally, better correlated with dense gas tracers in ULIRGs (Gao & Solomon 2004)• In MW GMCs, star formation happens in dense cores• Observations in nearby galaxies suggest the SFR-CO (3-2) is tighter than with CO (1-0)• Density or temperature effect?• Can we measure actual gas densities?

Wilson et al. (2009)

Why does molecular gas produce stars with constant efficiency?

Radius [parsecs]

Line

Wid

th [

km s

-1]

Milky WaySolomon+ 87

Local Group SpiralsM31 & M33

Dwarfs outside the Local GroupNGC 1569, 2976, 3077, 4214, 4449, 4605

Local Group dwarfsIC 10, LMC, NGC 185, NGC 205

SMCN83, LIRS36, LIRS49

Bolatto et al. (2008)

Bigiel et al. (2011)

OUTER DISK OF M33

Resolving GMCs in ULIRGs?• Using atmospheric phase correction CARMA can reach 0.15” resolution at 1.3 mm (2km baselines)

• That is 70 pc at 100 Mpc!!!

• GMCs are 20-50 pc in size for the MW. We are not that far from resolving them.

• ALMA will be able to pin down GMC properties across a range of galaxy typesArp 193: CO 2-1 at 0.15” (Zauderer et al., in

prep.)

Imaging feedback CO 1-0 wind in Mrk 231 (Feruglio et al. 2010)

M82 wind (Veilleux et al. 2005)

• Pollution of the ISM, galaxy mass function fall-off at large masses, solution to overcooling problem • There is molecular gas entrained in Galactic outflows, maybe enough to shut down SF• Low SB material. If it is optically thin, it will be brighter in the higher J transitions• AGN feeding: NUGA results

Walter et al. (2002); high-v CO

Panchromatic studies

Carilli et al. (2010)

SPIRE FTS spectrum of IC342

• Access to the full rotational ladder with good calibration and spatial resolution• Density, temperature, and column density• Access to some “optically thin” transition is key• Energy sources in the molecular ISM (dynamical heating, cosmic rays, e.g. Bradford et al. 2003)• Allows us to bypass Xco?• Needs to be spatially resolved

Chemistry: another handle on the conditions

Meier et al. (2008)

Meier et al. (2005)

IC342

• The distribution of chemical species produced under different conditions (PDRs, shocks, X-ray) illuminates the local conditions of the gas• Example: bar-driven shocks in IC 342

C+ the cosmic candle

• Detectable from ULIRGs to z~8 or more

• Here, sensitivity in 4 hours to e.g. [CII], [OI] & [NII] is shown

• Milky Way type galaxy detectable to z>3 in 24 hrs.

ALMA represents a new era in galaxy studies

Go beyond the “butterfly collecting” stage for nearby and high-z systems

Access to new windows with unprecedented sensitivity

For the first time we will be able to do astrophysics on representative samples