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12 October 2007Space Telescope Science Institute Molecular Gas and Star Formation in Nearby Galaxies Jean Turner UCLA with: David S. Meier, Lucian Crosthwaite,

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Presentation on theme: "12 October 2007Space Telescope Science Institute Molecular Gas and Star Formation in Nearby Galaxies Jean Turner UCLA with: David S. Meier, Lucian Crosthwaite,"— Presentation transcript:

1 12 October 2007Space Telescope Science Institute Molecular Gas and Star Formation in Nearby Galaxies Jean Turner UCLA with: David S. Meier, Lucian Crosthwaite, Chao-Wei Tsai, Sara Beck, Robert Hurt, Alaina Henry

2 12 October 2007Space Telescope Science Institute Molecular gas and star formation in galaxies present and future I.CO, a tracer of star-forming gas in galaxies II.Gas & star formation in spiral and dwarf galaxies III.Beyond CO: chemical diagnostics and feedback IV.ALMA Molecular gas and star formation in galaxies present and future I.CO, a tracer of star-forming gas in galaxies II.Gas & star formation in spiral and dwarf galaxies III.Beyond CO: chemical diagnostics and feedback IV.ALMA

3 12 October 2007Space Telescope Science Institute CO is the tracer of molecular gas Why not H 2 ? Excitation: first excited level is 510K above ground, but first quadrupole transition is J=2 rotational level… You will see very warm (hundreds of K) gas, or fluorescent emission from H 2 You will NOT see thermal emission from typical GMCs (4-30K), nor absorption (Av > 3-5) CO is the tracer of molecular gas Why not H 2 ? Excitation: first excited level is 510K above ground, but first quadrupole transition is J=2 rotational level… You will see very warm (hundreds of K) gas, or fluorescent emission from H 2 You will NOT see thermal emission from typical GMCs (4-30K), nor absorption (Av > 3-5)

4 12 October 2007Space Telescope Science Institute CO is the tracer of molecular gas Why CO? Abundant, chemically stable, transitions accessible from the ground ( = 3mm, 1mm) Easily excited: first excited rotational (J=1) level 5.5K Easily thermalized: collisional excitation dominates at densities > a few hundred/cc (low dipole moment and high opacity) CO is the tracer of molecular gas Why CO? Abundant, chemically stable, transitions accessible from the ground ( = 3mm, 1mm) Easily excited: first excited rotational (J=1) level 5.5K Easily thermalized: collisional excitation dominates at densities > a few hundred/cc (low dipole moment and high opacity)

5 12 October 2007Space Telescope Science Institute CO is a tracer of molecular (H 2 ) mass X co = I CO /N H2 = 2 x cm -2 /K km/s, empirical  rays (CR+H) show X co is good to x2 in Galaxy Bloemen et al. 1986, Strong et al arises from observed size-linewidth relation for GMCs Larson 1980, Solomon et al can be understood in the context of virialized clouds CO is a tracer of molecular (H 2 ) mass X co = I CO /N H2 = 2 x cm -2 /K km/s, empirical  rays (CR+H) show X co is good to x2 in Galaxy Bloemen et al. 1986, Strong et al arises from observed size-linewidth relation for GMCs Larson 1980, Solomon et al can be understood in the context of virialized clouds

6 12 October 2007Space Telescope Science Institute Virialized clouds? Column density at which H => H 2 is the same as the column density of the critically-bound Bonner-Ebert sphere (i.e., “Jeans mass”) at inner disk pressures. Clouds in high P regions more likely to be H 2. Scoville & Sanders 1987, Elmegreen 1989, Elmegreen & Parravano 1996 Yet while clouds are bound they are not collapsing… otherwise SFR = 10 9 M sun /t ff >200 M sun /yr, observed is 3-4 M sun /yr Zuckerman & Palmer 1974, Z & Evans 1974, Goldreich & Kwan 1979 GMCs appear to be turbulently supported Norman & Silk 1980, McKee Virialized clouds? Column density at which H => H 2 is the same as the column density of the critically-bound Bonner-Ebert sphere (i.e., “Jeans mass”) at inner disk pressures. Clouds in high P regions more likely to be H 2. Scoville & Sanders 1987, Elmegreen 1989, Elmegreen & Parravano 1996 Yet while clouds are bound they are not collapsing… otherwise SFR = 10 9 M sun /t ff >200 M sun /yr, observed is 3-4 M sun /yr Zuckerman & Palmer 1974, Z & Evans 1974, Goldreich & Kwan 1979 GMCs appear to be turbulently supported Norman & Silk 1980, McKee

7 12 October 2007Space Telescope Science Institute CO is a tracer of molecular (H 2 ) mass X co = I CO /N H2 = 2 x cm -2 /K km/s I co = T b dv ~ T k  v X co gives a dynamical mass like Tully-Fisher relatively insensitive to metallicity (Maloney & Black 1988, Elmegreen 1989) CO is a tracer of molecular (H 2 ) mass X co = I CO /N H2 = 2 x cm -2 /K km/s I co = T b dv ~ T k  v X co gives a dynamical mass like Tully-Fisher relatively insensitive to metallicity (Maloney & Black 1988, Elmegreen 1989)

8 12 October 2007Space Telescope Science Institute II.Molecular gas and star formation in spirals and dwarfs big galaxies and small galaxies appear to form stars differently molecular observations: so far, anecdotal (small number statistics) galaxy colors & age-dependent features => SF depends on galaxy form Kauffmann et al. 2006, SDSS II.Molecular gas and star formation in spirals and dwarfs big galaxies and small galaxies appear to form stars differently molecular observations: so far, anecdotal (small number statistics) galaxy colors & age-dependent features => SF depends on galaxy form Kauffmann et al. 2006, SDSS

9 12 October 2007Space Telescope Science Institute IC 342 Red: HI Green: CO Blue: stars 1’ beam VLA HI / NRAO 12m CO / DSS Crosthwaite et al kpc

10 12 October 2007Space Telescope Science Institute IC 342 Red: HI Green: CO Blue: stars 1’ beam VLA HI / NRAO 12m CO / DSS Crosthwaite et al. 2001

11 12 October 2007Space Telescope Science Institute IC 342 Red: HI Green: CO Blue: stars 1’ beam VLA HI / NRAO 12m CO / DSS Crosthwaite et al Interarm CO CO arms become HI arms HI & CO correlated Tilanus & Allen

12 12 October 2007Space Telescope Science Institute M83 Red: HI Green: CO Blue: stars 1’ beam 6 kpc VLA HI / NRAO 12m CO / DSS Crosthwaite et al. 2002; HI: Tilanus & Allen 1993

13 12 October 2007Space Telescope Science Institute M83 M83 has a sharp “edge” where both HI and H 2 surface densities fall off at R ~ 6 kpc Red: HI Green: CO Blue: stars 1’ beam VLA HI / NRAO 12m CO / DSS Crosthwaite et al. 2002; HI: Tilanus & Allen 1993

14 12 October 2007Space Telescope Science Institute M83 Gas “Edge” Falls at  gas = 15 Msun/pc 2

15 12 October 2007Space Telescope Science Institute NGC 6946 VLA HI / NRAO 12m CO / DSS In NGC 6946  gas falls off gradually  SFR =  gas Schmidt law, n=1 as opposed to Kennicutt law, n=1.4 Crosthwaite & Turner 2007 also seen by Crosthwaite et al. 2002, Wong & Blitz 2003 Red: HI Green: CO Blue: stars 1’ beam

16 12 October 2007Space Telescope Science Institute Interferometric observations of CO: ~6” ( pc) BIMA SONG: Regan et al. 2001, Helfer et al. 2003

17 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam

18 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam

19 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam 13 kpc 800 pc 320 pc OVRO & BIMA: Meier & Turner 2007

20 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam 320 pc OVRO & BIMA: Meier & Turner 2007 CO: contours greyscale: 3mm continuum, symbols: VLA subarcsec

21 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam 320 pc OVRO & BIMA: Meier & Turner 2007 CO: contours greyscale: 3mm continuum, symbols: VLA subarcsec Large star clusters forming here

22 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam 320 pc OVRO & BIMA: Meier & Turner 2007 clouds tidally stretched along bar

23 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam 320 pc OVRO & BIMA: Meier & Turner 2007 clouds tidally stretched along bar Xco too high by x2-4 - overpredicts cloud masses

24 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam 320 pc clouds tidally stretched along bar OVRO & BIMA: Meier & Turner 2007

25 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam OVRO & BIMA, CO, 3” beam: Meier & Turner 2007 Big bar Little bar

26 12 October 2007Space Telescope Science Institute Interferometric CO: Maffei 2 3” beam OVRO & BIMA, CO, 3” beam: Meier & Turner 2007 “P-V” diagram: effective “slit” along major axis Star formation occurs at the x 1 -x 2 orbit intersections

27 12 October 2007Space Telescope Science Institute Star formation and molecular gas in spirals 1.CO-emitting gas is star-forming gas; CO disk same as optical disk, HI disk is much bigger 2.SF needs a trigger: spiral arms or, in galactic centers, x 1 -x 2 orbit intersections 3.Schmidt law dependence unclear, we find n=1 (  SFR ~  gas ) rather than Kennicutt law (n= 1.4) 4.X co overpredicts H 2 mass in tidally supported clouds in galactic centers Star formation and molecular gas in spirals 1.CO-emitting gas is star-forming gas; CO disk same as optical disk, HI disk is much bigger 2.SF needs a trigger: spiral arms or, in galactic centers, x 1 -x 2 orbit intersections 3.Schmidt law dependence unclear, we find n=1 (  SFR ~  gas ) rather than Kennicutt law (n= 1.4) 4.X co overpredicts H 2 mass in tidally supported clouds in galactic centers

28 12 October 2007Space Telescope Science Institute dwarf galaxies: NGC 5253 Calzetti et al Gorjian 1996 Looks like dE that has accreted gas Nelson & Caldwell 1989 Numerous bright young clusters, ages 3 to 50 Myr More IR clusters than optical STIS: field stars lack O stars of the clusters, consistent with cluster dissolution on 10 Myr timescales or or bimodel SF Calzetti et al. 1997, Tremonti et al Alonso-Herrero et al. 2004

29 12 October 2007Space Telescope Science Institute dwarf galaxies: NGC 5253 Meier, Turner, & Beck 2002 Calzetti et al Gorjian 1996 SF efficiency =M  /( M  + M gas ) =75%, on 200 pc scales In Galaxy, SFE~1-3% on GMC scales (SFE~30% on pc scales, ONC) Lada et al 1984 SFE 2 orders of magnitude higher than in Galaxy

30 12 October 2007Space Telescope Science Institute dwarf galaxies: NGC 5253 Meier et al E/VLA 7mm + NICMOS: Turner & Beck 2004 Calzetti et al Gorjian pc, 0.6” embedded IR cluster only really visible ~1.9-2 microns

31 12 October 2007Space Telescope Science Institute dwarf galaxies: NGC 5253 Meier et al Rodriguez-Rico et al E/VLA 7mm + NICMOS: Turner & Beck 2004 H53  Calzetti et al Gorjian pc, 0.6”

32 12 October 2007Space Telescope Science Institute image courtesy of NRAO/AUI HI: Yun, Ho, Lo 1994

33 12 October 2007Space Telescope Science Institute Star formation and molecular gas in dwarf galaxies 1.Star formation in dwarf galaxies may be driven by accretion from outside — could explain “burstiness” N5253: Meier et al. 2002, NGC 3077, Meier et al. 2003, Walter et al. 2004, He 2-10? Kobulnicky et al (rotation) 2.Is this mode of star formation fundamentally different wrt star formation efficiency (is it easier to form bound clusters in dwarfs?) 3.Role of magnetic fields? Star formation and molecular gas in dwarf galaxies 1.Star formation in dwarf galaxies may be driven by accretion from outside — could explain “burstiness” N5253: Meier et al. 2002, NGC 3077, Meier et al. 2003, Walter et al. 2004, He 2-10? Kobulnicky et al (rotation) 2.Is this mode of star formation fundamentally different wrt star formation efficiency (is it easier to form bound clusters in dwarfs?) 3.Role of magnetic fields?

34 12 October 2007Space Telescope Science Institute III. Beyond CO: chemical diagnostics & feedback

35 12 October 2007Space Telescope Science Institute NGC 253 2mm survey IRAM 30 m NGC 253 SURVEY (Martin et al.,2006) First unbiased line survey in a galaxy IRAM: dv ~ 9 km/s IRAM 2MASS - Jarrett CS CCH

36 12 October 2007Space Telescope Science Institute Imaging Chemistry in Galaxies: IC 342 Owens Valley mm Array N2H+N2H+ HNCHC 3 NC2HC2HC 34 S HNCO CH 3 OH central 300 pc 3mm lines: molecules have similar excitation differences are chemical contours: 13 CO, color = molecules Meier & Turner 2005

37 12 October 2007Space Telescope Science Institute Imaging Chemistry in Galaxies: IC 342 Owens Valley mm Array PC Axis 1: Density- weighted mean column density Meier & Turner 2005 N2H+N2H+ HNCHC 3 NC2HC2HC 34 S HNCO CH 3 OH

38 12 October 2007Space Telescope Science Institute Imaging Chemistry in Galaxies: IC 342 Owens Valley mm Array PC Axis 1: Density- weighted mean column density PC Axis 2: Shock tracers vs PDR molecules Meier & Turner 2005 N2H+N2H+ HNCHC 3 NC2HC2HC 34 S HNCO CH 3 OH

39 12 October 2007Space Telescope Science Institute Imaging Chemistry in Galaxies: IC 342 Owens Valley mm Array PC Axis 1: Density- weighted mean column density PC Axis 2: Shock tracers vs PDR molecules CO, N 2 H +, HNC, HCN; gas tracers C 2 H, C 34 S: PDR Methanol, HCNO: shocks Meier & Turner 2005 N2H+N2H+ HNCHC 3 NC2HC2HC 34 S HNCO CH 3 OH

40 12 October 2007Space Telescope Science Institute Beyond CO: chemical diagnostics & feedback 1.High resolution imaging (ALMA) reduces chemical complexity by isolating regions of common chemistry in galaxies 2.Studies of nearby galaxies suggest that there are classes of molecules, such as: Gas tracers: CO, N 2 H +, HCN, HNC Grain chemistry (shocks?) tracers: methanol, HNCO (spiral arms) PDR tracers: C 2 H (B stars rather than O?) Beyond CO: chemical diagnostics & feedback 1.High resolution imaging (ALMA) reduces chemical complexity by isolating regions of common chemistry in galaxies 2.Studies of nearby galaxies suggest that there are classes of molecules, such as: Gas tracers: CO, N 2 H +, HCN, HNC Grain chemistry (shocks?) tracers: methanol, HNCO (spiral arms) PDR tracers: C 2 H (B stars rather than O?)

41 12 October 2007Space Telescope Science Institute IV. ALMA “up to 64” (currently 50) x 12m antennas 12 x 7m antennas (ACA) EU (ESO), NA (NRAO, Canada), J (Japan, Taiwan) in the Atacama desert of Northern Chile, 16,400 ft heterodyne receivers from 0.3 to 9.6mm (  v <.05km/s) spatial resolution to 5 mas sensitivity: 7  Jy in 1 hr, continuum brightness 0.8mK

42 12 October 2007Space Telescope Science Institute ALMA Science Drivers 1.Detect CO in an L  galaxy at z = 3. 2.Resolve gas kinematics in protoplanetary disks at 150 AU. 3.Imaging comparable to HST.

43 12 October 2007Space Telescope Science Institute ALMA Site

44 12 October 2007Space Telescope Science Institute ALMA is near San Pedro de Atacama

45 12 October 2007Space Telescope Science Institute San Pedro de Atacama

46 12 October 2007Space Telescope Science Institute San Pedro de Atacama

47 12 October 2007Space Telescope Science Institute San Pedro de Atacama

48 12 October 2007Space Telescope Science Institute ALMA site

49 12 October 2007Space Telescope Science Institute

50 12 October 2007Space Telescope Science Institute ALMA buildings

51 12 October 2007Space Telescope Science Institute ALMA buildings

52 12 October 2007Space Telescope Science Institute ALMA buildings

53 12 October 2007Space Telescope Science Institute ALMA antennas - five in Chile already! 3 can bow Melco/Mitsubishi antennas, ALMA-J

54 12 October 2007Space Telescope Science Institute ALMA transporter: “Otto”

55 12 October 2007Space Telescope Science Institute ALMA timescales First interferometric observations 2008 Call for proposals 2009 Early science 2010 Full operations 2012

56 12 October 2007Space Telescope Science Institute Molecular gas and star formation in galaxies Current understanding CO gas is star-forming gas X co may give reliable masses in absence of other dynamical effects Star formation needs a trigger, not just gas: Spirals: related to spiral structure and bar orbits Dwarfs: accretion of intergalactic gas Bright futures (ALMA, CARMA, PdBI): CO and gas across the universe (z=10?) Modes & triggers of star formation (clusters, field stars) Gas-dominated galaxies? (gas ages) Extragalactic chemistry: chemical diagnostics of galaxy evolution Molecular gas and star formation in galaxies Current understanding CO gas is star-forming gas X co may give reliable masses in absence of other dynamical effects Star formation needs a trigger, not just gas: Spirals: related to spiral structure and bar orbits Dwarfs: accretion of intergalactic gas Bright futures (ALMA, CARMA, PdBI): CO and gas across the universe (z=10?) Modes & triggers of star formation (clusters, field stars) Gas-dominated galaxies? (gas ages) Extragalactic chemistry: chemical diagnostics of galaxy evolution


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