gas in local galaxies and beyond with alma
DESCRIPTION
Gas in local galaxies and beyond with ALMA. Alberto D. Bolatto University of Maryland. How are galaxies put together?. red sequence. green valley. Salim et al. (2007), Kauffmann et al. (2003). NUV- r (SSFR). blue sequence. M r (stellar mass). - PowerPoint PPT PresentationTRANSCRIPT
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