Gas in local galaxies
and beyond with ALMA
Alberto D. Bolatto
University of Maryland
How are galaxies put together?
Salim
et al. (2007),
Kauffmann et al. (2003)
•
T
wo 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
(SSFR)
M
r
(stellar mass)
green valley
red sequence
blue sequence
H
I
H
2
SFR
UV, X
-
rays, cosmic rays
mechanical feedback
metals, H, dust
accretion
n
turbulence
instabilities
gravity
thermodynamics,
chemistry
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 field
ALMA
polarization
H
I
H
2
SFR
UV, X
-
rays, cosmic rays
mechanical feedback
metals, H, dust
accretion
n
turbulence
gravity
thermodynamics,
chemistry
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
instabilities
magnetic field
ALMA
polarization
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
(H
I
+2H
2
)
1.4
Genzel
et al.
(2010)
NGC 4579
NGC 4254
NGC 3184
Molecular Gas
Peak CO intensity
From HERACLES
Atomic Gas
VLA
21cm data THINGS +
new & archival
Kinematics
Here from HI line
Also
from
CO
Old Stars
Near infrared intensity
From SINGS and LVL
Recent Star Formation
Composite of
FUV
(GALEX)
,
mid
-
IR
(SINGS/LVL),
and
H
α
(SINGS/LVL)
A
HERACLES
(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
•
O
bservations 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 Width [km s
-
1
]
Milky Way
Solomon+ 87
Local Group Spirals
M31 & M33
Dwarfs outside the Local
Group
NGC 1569, 2976, 3077,
4214, 4449, 4605
Local Group dwarfs
IC 10, LMC, NGC 185,
NGC 205
SMC
N83, 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 types
Arp 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
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