Ebb & Flow: Molecular Gas and Star Formation in Nearby Spirals Michele Thornley Bucknell University/STSc. I To take away: With grateful thanks to: M. of wide-field surveys • Value. 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 millimeter interferometers • Promise of+CO studies with& SINGS collaborations • Promise of studying gas, dust and star formation with Spitzer STSc. I March 24, 2004
CO as an H 2 tracer (NGC 3627, BIMA SONG) n 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 Weib, Neininger, Huttemeister & Klein 2001 Boselli et al. 2002 Rosolowsky et al. 2003 Bolatto et al. 2003, Walter et al. 2003 STSc. I March 24, 2004
Molecular gas in the Milky Way Dame, Hartmann, & Thaddeus 2001 STSc. I March 24, 2004
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? STSc. I March 24, 2004
Transitions between molecular & atomic gas 10’ IC 342 5’ M 83 CO HI Crosthwaite & Turner (2001, 2002) Pressure dependent cloud formation: e. g. , Elmegreen 1993, Elmegreen & Parravano 1994, Elmegreen 1995, Sofue et al. 1995, Honma et al. 1995, Hidaka & Sofue 2002 STSc. I March 24, 2004
Local Group spirals Dame et al 1993 (~1. 7 kpc resolution) Loinard et al 1999 (200 pc resolution) M 31 Guelin 2000, Neininger et al 2001 (90 pc resolution) STSc. I March 24, 2004
M 31 Loinard et al 1999 Kinematics as constraints on bulge & disk distributions: fast rotating, triaxial bulge thick H 2 disk (or warping)? z 0~200 -500 pc Berman 2001, Berman & Loinard 2002 STSc. I March 24, 2004
Zooming in on M 31 clouds Neininger et al 1998, Neininger et al. 2001 (~3 -4 pc resolution) STSc. I March 24, 2004
Local Group spirals M 33 Engargiola et al. 2003 (50 pc resolution), Rosolowsky et al. 2003 (20 pc resolution) See also: Fukui et al. 2001, 2003 (LMC w/ NANTEN) STSc. I March 24, 2004
M 33 Galactic M 33 Engargiola et al. 2003, Rosolowsky et al. 2003 Kinematics and distribution provide constraints on cloud formation: cloud size, low angular momentum correlations in velocity gradients for separations < 500 pc STSc. I March 24, 2004
BIMA Survey of Nearby Galaxies (BIMA SONG) Regan et al. 2001, Helfer et al. 2003 (Das et al. 2003) STSc. I March 24, 2004
BIMA SONG Selection criteria: n n 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 n Average distance 12 Mpc (H 0=75 km s-1 Mpc-1) Unbarred Barred 10 Vsys < 2000 km sec-1 BT< 11 Sa-Sd i < 70 o (d>-20 o, D 25<70’) 5 number • • 0 n ab b bc c cd d (Hubble type) • Map out to R~5 kpc STSc. I March 24, 2004
10 (8) Central excess No central excess Number 8 6 (5) (3) 4 (27 of 44 galaxies) Sab/Sb Sbc Sc/Scd 15 (14) Number 12 Central excess No central excess (3) (2) 2 BIMA SONG Radial Profiles (6) 9 6 (6) (5) 3 Regan et al. 2001 Thornley et al. 2004 (in prep. ) (2) SA SAB/SB STSc. I March 24, 2004
Central concentrations n Central surface densities higher in barred spirals • Statistical support for barinduced inflow: • • n Sakamoto et al. 1999 Sheth et al. 2004 High Snuc 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 STSc. I March 24, 2004
H 2, HI, and the Schmidt law in SONG galaxies (from Elmegreen 1989) Wong & Blitz 2002 STSc. I March 24, 2004
Star Formation & Bars (CO) (Ha) Sheth et al. 2002 STSc. I March 24, 2004
Measuring streaming motions (NGC 5055) HI & Ha, (Thornley & Mundy 1997) BIMA SONG CO velocity residuals (Thornley et al. , 2004) STSc. I March 24, 2004
The future of millimeter studies CARMA (~2005) Cedar Flat CARMA on Cedar Flat (simulated) ALMA (~2008/2012) Chajnantor STSc. I March 24, 2004
Other tracers of gas and dust? (BIMA SONG) IRS/MIPS Dale & Helou 2002 IRAC MIPS STSc. I March 24, 2004
Spitzer Infrared Nearby Galaxies Survey (SINGS) n n PI: R. Kennicutt 75 nearby galaxies (d<30 Mpc) • Range of Hubble type, luminosity, IR/optical n Comprehensive database: • IRAC/MIPS broadband imaging (3. 6 -160 mm) • IRS/MIPS SED strips (14 -100 mm) • IRS spectral maps (5 -37 mm) • Nuclear & extranuclear • Lots of ancillary data! (optical/NIR, UV, CO, HI, …) SINGS website: http: //sings. stsci. edu STSc. I March 24, 2004
SINGS sample & plan IRAC MIPS SED IRS (low) IRS(S-high) IRS(L-high) Kennicutt et al. 2003, PASP, 115, 928 STSc. I March 24, 2004
NGC 7331 IRAC Regan et al. 2004 MIPS STSc. I March 24, 2004
The ring in NGC 7331 (Scaled) + ring * outside ring , total Regan et al. 2004 STSc. I March 24, 2004
Comparing gas, dust, and star formation gas Star formation ? ? STSc. I March 24, 2004
Spectroscopy with Spitzer Nucleus Short Low J. D. Smith et al. 2004 Long High STSc. I March 24, 2004
M 81: Early Release NASA/JPL-Caltech/R. Hurt (SSC/Caltech) http: //www. spitzer. caltech. edu STSc. I March 24, 2004
Summary n n n 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 H 2) • Star formation variations • Large- and small-scale kinematics STSc. I March 24, 2004
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