Star Formation in Nearby Galaxies in the Era of JWSTDaniela Calzetti (UMass)Alison Crocker (UMass)Karin Sandstrom (MPIA)

STScI, Baltimore, MD, June 6th-8th, 2011

Let’s Define `Nearby’ Any galaxy within ~100 Mpc, not to exclude sufficiently `rare’

objects (e.g., Arp 220 at ~ 80 Mpc) I will use two typical distances: 5 Mpc and 100 Mpc, which

correspond to the `Local Volume’ and a little beyond the distance of the Coma Cluster.

For reference: NIRCAM PSF FWHM ~ 0.1” at 2 m and 0.2” at 4 m

Subtends spatial scales ~ 2.5-5 pc at 5 Mpc, the typical scale of star clusters;

Subtends spatial scales ~ 50-100 pc at 100 Mpc, the typical scale of HII regions;

MIRI PSF FWHM ~ 0.3” at 8 m and 0.9” at 24 m Subtends spatial scales ~ 7-21 pc at 5 Mpc, the typical scale of a

small Molecular Cloud; Subtends spatial scales ~ 140-440 pc at 100 Mpc, the size of the

star forming IR-bright center of the ULIRG Arp220

A Sense of Scale

Let’s not forget that ALMA (~0.4-3+ mm) will be operating at full antenna complement, with a maximum resolution of 0.015”

JWST/MIRI at 8 m (0.3”)

Spitzer/IRAC at 8 m (2”)Antennae Galaxies ~ 18 Mpc

JWST w.l.s in Nearby Galaxies -1 JWST w.l.s in Nearby Galaxies -1

(m) 1 10 100 1000

H P 8 m 24 m

NIRCam

70 m 160 mUV [OII]Direct stellar light Dust-processed light

Spitzer

LMT/50ALMA

Herschel

MIRI

JWST w.l.s in Nearby Galaxies -2 JWST w.l.s in Nearby Galaxies -2 NGC5194 – IRS/HR

NGC1482 - IRS Smith et al. 2007

Spitzer IRS: R ~50-100 & 600 (5-40 m)

JWST NIRSpec & MIRI: R~100, 1000, & 3000 (1-27 m)

Dale et al. 2009

JWST wins in both w.l. and angular resolution!Peeters 2010

ISO

ASTRO2010 Principal Questions of Relevance for Nearby Galaxies Investigations

What are the connections between luminous and dark matter? What is the fossil record of galaxy assembly and evolution from

the first stars to the present? How do stars and black holes form? How do baryons cycle in and out of galaxies and what do they

do while they are there? What are the flows of matter and energy in the circumgalactic

medium? What controls the mass-energy-chemical cycles within

galaxies? How do black holes work and influence their surroundings? What are the progenitors of Type Ia supernovae and how do

they explode?

1. How do Stars Form?

Log

S

FR

Log gas

Kennicutt et al. 2007

SFR ~ gasN

Bigiel et al. 2008

Kennicutt 1998

Mainly ushered by Spitzer (obscured SF) and mm maps

Lessons Learned (~past decade)1.The physics of the scaling laws of SF can be understood only at sub-galactic scales, MC scales:

slope~1 for universal gas-star conversion slope~1.5 if driven by gravitational instability slope~2 if driven by cloud-cloud collision

2.The correlation between star formation and gas becomes tighter as the gas density increases (progression: HI(?), CO(1-0), CO(3-2), HCN, etc.);

•Tracing the dust-obscured portion of star formation is essential at least as much as tracing the dust-free portion; however, SFR tracers, esp. dust-obscured ones, can be `tricky’: you risk tracing evolved stars!

•Core mass functions resembles stellar IMFs, with 30% SFE (Alves et al. 2007); a hint to the origin of the IMF?

Liu et al. 2011

What Do We Still Need to Learn?1. How is star formation related to molecular clouds (as opposed to

regions in galaxies)?2. How do MCs form, evolve, and on which timescales?3. How do we account for dust-enshrouded star formation? What is

the duration of this phase? How does it depend on local conditions (disk/nucleus/etc.) and global environment?

4. What is the hierarchy of scales for star formation? Is the dichotomy cluster/diffuse, IF there is a dichotomy, too simplistic?

5. Is the stellar IMF universal? Why? What are the conditions for variation, if any?

6. Can we constrain the stellar IMF(s) and their connection to the parental gas clouds well enough to develop a theory of star formation?

The synergy between JWST and ALMA is immense and will yield stronger results than the two facilities separately!

An evolutionary scenario for MCsFukui et al. 1999, Kawamura et al. 2009

In the LMC, MCs show at least three separate `signatures’ in their relation with H and young massive-star clusters:Type I: MC only;Type II: MC + HII regions;Type III: MC+HII regions+young massive-star clusters;Type IV(?): young clusters only.

Timescale ~ 30 Myr.

1. How general is this result? (e.g., Koda et

al. 2009 finds t~ 100 Myr in M51) 2. Are Type I truly star-less? (e.g., Indebeteouw et al. 2008); in contrast with MW, but similar to M33 (Engargiola 2003); Type I fraction increases with lower MC masses.

Truly star-less?

A JWST/ALMA Experiment

M83, face-on, 4.5 Mpc distance,O/H ~ solar (no CO/H2 conversion problems, see Leroy et al. 2011), 0.5”= 11 pc; WFC3/ERS 3-color picture

Ingredients:A solar-metallicity, face-on galaxy with a fully characterized star cluster population (HST, Chandar et al. 2010).

What to look for:a.Resolve MCs, obtain population (ALMA)b.Resolve dust-obscured star clusters (JWST; 8 m and/or >20 m)

Expected results:1.Timescale of dust-enshrouded SF;2.MCs lifetimes;3.Evolutionary sequence for MC/SF;4.SK-Law at cloud level;5.# 4 will inform models of SF.

2. How do black holes work and influence their surroundings?

MB

H

(km s-1)

Gultekin et al. 2009Somerville et al. 2008

log Mstar

1. Self-regulation of BH growth to create the M- relation2. QSO/AGN feedback to quench star formation

Both require efficient coupling between BH and its surroundings, but SF `quenching’ is harder to produce from simulations than BH self-regulation (the sphere of BH influence remains within 300 pc, no large-scale gas outflow, Jackson, Quataert et al. 2010)

Morphological Quenching of SF

Martig et al. 2009

As mergers transform rotation-supported disks into pressure-supported spheroids, the gas gets stabilized against fragmentation to bound clumps (less efficient SF).

No need to remove cold gas from galaxies.No need for extremely efficient coupling between the AGN and the surrounding galaxy.

Gas-Rich Early Type Galaxies

About 22% of ETGs, mostly lenticulars, contain molecular gas, up to ~a few x 109 Msun (Combes et al. 2007,

Crocker et al. 2011, Young et al. 2011)

They appear to have `normal’ star formation efficiency (Crocker et al. 2011) and a few have molecular outflows (e.g., Alatalo et al. 2011) = against Morphological Quenching?

B-V

MB

The Role of JWST

Similar to Spitzer 8 m PSF

Alatalo et al. 2011

NGC1266 (30 Mpc): CO disk (yellow contours) ~ 2” ~ 300 pc ~ 1 Spitzer PSF

The combination of JWST and ALMA will:1.Increase the sample size (larger distances) from the current 56/259 ETGs with CO emission;2.Separate dust-obscured star formation from AGN contributions at the ~ 50 pc scale.3.Obtain a full census of gas outflows, and their engine(s)

Provide the definite census of star formation in ETGs to test star formation quenching scenarios and the origin of the cold gas.

Star Formation-AGN Separation and Physics

Smith et al. 2007, Hunt et al. 2010

The MIRI IFU capabilities will be key for unraveling the differences in gas excitation and dust heating characteristics of star formation and AGNs.

AGN

Star-Forming

Low-Metallicity SF

Genzel et al. 1998; Dale et al. 2006, 2009

3. What controls the mass-energy-chemical cycles within galaxies?

A complex question that can be broken into many sub-questions, and is unlikely to have a single answer.A sub-question:

How are dust heaters (mostly stars) and emitters (dust components) related to each other?

Dust is highly democratic: it will accept heating from just about any star.Stars are highly undemocratic: given the chance, they will produce *and* destroy dust.

Anwer is fundamental for calibrating obscured SFR indicators and for understanding the dust-obscured phases of early galaxies!

The Rich (and Mysterious) Physics of PAHs

Peeters 2010

Draine & Li 2007

NIRSpec covers the critical 3.3 m band for small, neutral PAHs

NASA

PAH as MetallicityPAH as Metallicity

Engelbracht et al. 2008

Effect not due to PAH ionization or de-hydrogenation effects (Smith

et al. 2007). Could be deficit of PAHs of certain sizes (Smith et al. 2007,

Sandstrom et al. 2010, Hunt et al. 2010). Unsolved!

Profound changes in the ISM of galaxies with metallicity below 1/4 – 1/5 solar

Nature or Nurture?

Draine et al 2007

L8/

LT

IR

Nature or Nurture?Nature or Nurture?Nature=PAH production (Galliano et al. 2008, Dwek et al. 2008, Munoz-Mateos et al.

2009): delayed production of PAHs from AGB stars (1 Gyr) versus SNII dust components (10 Myr).

Nurture=PAH destruction (Cesarsky et al. 2000, Madden et al. 2006,Wu et al. 2006, Bendo et al. 2006, Berne’ et al. 2007, Smith et al. 2007,

Gordon et al. 2008, Engelbracht et al. 2008): PAHs destroyed in the harder ionization fields of low metallicity environments.

Ionization Index

Gordon et al. 2008

JWST angular and spectral resolution will be key for answering this question

JWST’s RoleJWST’s Role

H + 8 m contours (left) or UV contours (right)

NGC604 in M33 (Relano & Kennicutt 2009)

8 m emission depressed in correspondence of HII regions/UV-bright clusters *and* depleted in the diffuse ISM of the Magellanic Clouds, but bright in PDRs (Helou et al. 2004, Bendo et al. 2006, Sandstrom et al. 2010, Paradis et al. 2011)

JWST will resolve HII regions and PDRs in galaxies up to 5-10 Mpc distance across a large range of physical and chemical conditions.

ConclusionsConclusionsThere are critical questions on galaxy evolution that need the combination of nearby galaxies and JWST to be answered; a few have been explored here:

1.How do stars form? How is star formation related to the population of molecular clouds? This is an example of the exquisite synergy between JWST and ALMA.

2.How are black holes influencing their surroundings?

3.How is the physics of dust determined by the environmental conditions? How does this affect our ability to interpret the dust-enshrouded phases of galaxy evolution and measure SFRs at high redshift?