STScI March 24, 2004 Ebb & Flow: Molecular Gas and Star Formation in Nearby Spirals Michele Thornley Bucknell University/STScI With grateful thanks to:

STScI March 24, 2004

Ebb & Flow: Molecular Gas and Star Formation

in Nearby Spirals

Michele ThornleyBucknell University/STScI

With grateful thanks to:M. Regan, D. Calzetti, M. Meyer, M. Mutchler, R. Kennicutt,

S.Vogel, T. Wong, T. Helfer, K. Sheth, C. Spohn-Larkins, R. Magee + the BIMA SONG & SINGS collaborations

To take away:

•Value of wide-field surveys

•Promise of CO studies with millimeter interferometers

•Promise of studying gas, dust and star formation with Spitzer


CO as an H2 tracer

Open question: dependence of “X-factor” on metallicity, temperature, e.g. (an extremely abbreviated list…) • Maloney & Black 1988• Wilson 1995; Arimoto et al. 1996; Israel 1997• Regan 2000• Dame, Hartman, & Thaddeus 2001• Wei, Neininger, Huttemeister & Klein 2001• Boselli et al. 2002• Rosolowsky et al. 2003• Bolatto et al. 2003, Walter et al. 2003

(NGC 3627, BIMA SONG)

CO J =1-0 B-I B-K I -K J -KCO J =1-0CO J =1-0 B-IB-I B-KB-K I -KI -K J -KJ -K


Molecular gas in the Milky Way

Dame, Hartmann, & Thaddeus 2001


Questions to ask:

•Interaction of molecular and atomic gas?

•Distribution & population of molecular clouds?

•Dependence of star formation on large-scale dynamics?

•Variation between galaxies?


Transitions between molecular & atomic gas

Crosthwaite & Turner (2001, 2002)

CO

HI

IC 342 M8310’ 5’

Pressure dependent cloud formation: e.g., Elmegreen 1993, Elmegreen & Parravano 1994, Elmegreen 1995, Sofue et al. 1995, Honma et al. 1995, Hidaka & Sofue 2002


Local Group spirals

Dame et al 1993 (~1.7kpc resolution)

M31M31

Guelin 2000, Neininger et al 2001

(90 pc resolution)

Loinard et al 1999 (200 pc resolution)


M31

Loinard et al 1999

Berman 2001, Berman & Loinard 2002Kinematics as constraints on bulge & disk distributions:fast rotating, triaxial bulge

thick H2 disk (or warping)?

z0~200-

500pc


Zooming in on M31 clouds

Neininger et al 1998, Neininger et al. 2001

(~3-4 pc resolution)


Local Group spirals

Engargiola et al. 2003 (50 pc resolution), Rosolowsky et al. 2003 (20 pc resolution)

M33M33

See also: Fukui et al. 2001, 2003 (LMC w/ NANTEN)


M33

Kinematics and distribution provide constraints on cloud formation:cloud size, low angular momentumcorrelations in velocity gradients for separations < 500 pc

Engargiola et al. 2003, Rosolowsky et al. 2003

GalacticM33


BIMA Survey of Nearby Galaxies (BIMA SONG)Regan et al. 2001, Helfer et al.

2003

(Das et al. 2003)


BIMA SONG

Selection criteria:• Vsys < 2000 km sec-1

• BT< 11

• Sa-Sd

• i < 70o (>-20o,D25<70’)

93% of the sample detected Chosen 44 spirals include:

• 29 bars (SAB+SB) • 20 emission-line (Seyfert, LINER)• 19 grand-design spirals • 17 HII nuclei

Average distance 12 Mpc (H0=75 km s-1 Mpc-1)• Map out to R~5 kpc

ab b bc c cd d

(Hubble type)0

510

nu

mb

er

UnbarredBarred


2

4

6

8

10

Sab/Sb Sbc Sc/Scd

Central excessNo central excess

(5)

(2)(3) (3)

(8)

(6)

Num

ber

12

15

3

6

9

SA SAB/SB

Central excessNo central excess

(5) (6)

(14)

(2)N

umbe

r

BIMA SONG Radial Profiles

Regan et al. 2001

Thornley et al. 2004 (in prep.)

(27 of 44 galaxies)


Central concentrations

Central surface densities higher in barred spirals• Statistical support for bar-

induced inflow:• Sakamoto et al. 1999• Sheth et al. 2004

High nuc correlated with large surface mass density• Perhaps bar not necessary

for centrally peaked gas• Sofue et al.2003• (Thornley et al. 2004)

Sakamoto et al. 1999


H2,HI, and the Schmidt law in SONG galaxies

Wong & Blitz 2002

(from Elmegreen 1989)


Star Formation & Bars

Sheth et al. 2002

(CO)

(H)


Measuring streaming motions(NGC 5055)

BIMA SONG CO velocity residuals (Thornley et al., 2004)

HI & H, (Thornley & Mundy 1997)


The future of millimeter studies

CARMA (~2005)

Cedar Flat CARMA on Cedar Flat (simulated)

ALMA (~2008/2012)

Chajnantor


Other tracers of gas and dust?CO J =1-0 B-I B-K I -K J -KCO J =1-0CO J =1-0 B-IB-I B-KB-K I -KI -K J -KJ -K

(BIMA SONG)

Dale & Helou 2002

IRACMIPS

IRS/MIPS


Spitzer Infrared Nearby Galaxies Survey (SINGS)

PI: R. Kennicutt 75 nearby galaxies (d<30 Mpc)

• Range of Hubble type, luminosity, IR/optical Comprehensive database:

• IRAC/MIPS broadband imaging (3.6-160 m)

• IRS/MIPS SED strips (14-100 m)

• IRS spectral maps (5-37 m)• Nuclear & extranuclear

• Lots of ancillary data! (optical/NIR, UV, CO, HI,…)

SINGS website: http://sings.stsci.edu


SINGS sample & plan

Kennicutt et al. 2003, PASP, 115, 928

IRAC

MIPS

MIPS SED

IRS (low)

IRS(S-high)

IRS(L-high)


IRAC

MIPS

NGC 7331

Regan et al. 2004


The ring in NGC 7331

Regan et al. 2004

+ ring* outside ring total

(Scale

d)


Comparing gas, dust, and star formation

gas gasStar formation

? ?


Spectroscopy with Spitzer

Nucleus

Short Low

Long HighJ.D. Smith et al. 2004


M81: Early Release

http://www.spitzer.caltech.edu

NASA/JPL-Caltech/R. Hurt (SSC/Caltech)


Summary

High spatial and spectral resolution observations of molecular gas in galaxies are becoming increasingly common.

We are now able to examine the relationship of gas, dust, stars, and galactic structure over a range of galaxy types.

We can address a wide variety of questions in a quantitative way:• Cloud formation (e.g., turbulence, HI H2)

• Star formation variations• Large- and small-scale kinematics

Documents

STScI March 24, 2004 Ebb & Flow: Molecular Gas and Star Formation in Nearby Spirals Michele Thornley Bucknell University/STScI With grateful thanks to: