Gas in local galaxies and beyond with ALMA

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27 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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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