Luminous Infrared Galaxies with the Submillimeter Array: Probing the Extremes of Star Formation

1
Luminous Infrared Galaxies with the Submillimeter
Array Probing the Extremes of Star Formation
Mrk273
UGC5101

• Christine Wilson
• McMaster University
• November 2008

2
Luminous Infrared Galaxies with the Submillimeter
Array

• Chris Wilson (McMaster PI)
• Glen Petitpas, Alison Peck, Melanie Krips, TJ Cox
  (CfA)
• Paul Ho, Satoki Matsushita (ASIAA)
• Brad Warren, Jen Golding, Adam Atkinson
  (McMaster)
• Lee Armus (IPAC), Andrew Baker (Maryland),
  Daisuke Iono (NAOJ), Mika Juvela (Helsinki),
  Chris Mihos (Case Western), Ylva Pihlstrom (UNM),
  Min Yun (U.Mass)
• And thanks to all the SMA observers in 2005-2007
  who took data for this project!
• Wilson et al., 2008, ApJS, 178, 189
• Iono, Wilson, et al., 2008, ApJ, submitted

3
Luminous Infrared Galaxies with the Submillimeter
Array

• What are Luminous Infrared Galaxies?
• An SMA Legacy Project Gas Morphology and
  Dynamics in U/LIRGs
• Gas-to-dust ratio in central kpc
• Comparison to high-redshift submillimeter
  galaxies
• Future work, NGLS, and ALMA

4
What are Luminous Infrared Galaxies?

• Major population of galaxies discovered by IRAS
  (Houck et al. 1984, 1985 Aaronson Olszewski
  1984)
• High infrared to blue luminosity ratio (e.g. 80
  for Arp 220) (Soifer et al. 1984)
• Define
• Luminous infrared galaxies (LIRGs)
• LFIR gt 1011 Lo
• Ultraluminous infrared galaxies (ULIRGs)
• LFIR gt 1012 Lo

5
Spectral Energy Distribution
Figure from Galliano 2004
6
U/LIRG luminosity function

• For Lbolgt1011 Lo infrared galaxies are the
  dominant population in the local universe
• For Lbolgt1012 Lo infrared galaxies exceed the
  space density of quasars
• (Soifer et al. 1987)

Figure from Sanders Mirabel 1996
7
ULIRGS are galaxy mergers
Sanders et al. 1988
Scoville et al. 2000

• All galaxies with LFIR gt 5x1011 Lo are
  interacting or close pairs (Sanders et al. 1987)

8
Molecular Gas in ULIRGs
Arp 220 (Sakamoto et al. 1999)

• Large masses of molecular gas within Rlt2 kpc
• Broad line widths imply large dynamical masses
• Rotation curves can be quite complex

9
Luminosity Source Starburst or AGN?

• 70-80 predominantly starbursts
• 20-30 predominantly AGN

Genzel et al. 1998
10
Dusty galaxies at high redshift ULIRGs on
steroids?
Tacconi et al. 2006
Ivison et al. 2000

• Cosmologically significant population of very
  luminous dusty galaxies discovered at submm
  wavelengths
• For zgt0.5, 5 mJy at 850 ?m implies L gt 8x1012 Lo

11
Luminous Infrared Galaxies with the Submillimeter
Array

• What are Luminous Infrared Galaxies?
• An SMA Legacy Project Gas Morphology and
  Dynamics in U/LIRGs
• Gas-to-dust ratio in central kpc
• Comparison to high-redshift submillimeter
  galaxies
• Future work, NGLS, and ALMA

12
Gas Morphology and Dynamics in Luminous Infrared
Galaxies An SMA Legacy Project

• Representative sample of 12 luminous and
  ultraluminous infrared galaxies
• DL lt 200 Mpc
• log(LFIR) gt 11.4
• All with previous interferometric observations in
  the CO J1-0 line

13
The Submillimeter Array

• 8 x 6m antennas, maximum baseline 500 m
• Dual frequency operation at 230, 345, 690 GHz
• 2 GHz bandwidth 2000 km/s at 345 GHz
• Angular resolution of our survey is 1-4 (CO 3-2
  and 880 micron continuum)

The Submillimeter Array is a joint project
between the Smithsonian Astrophysical
Observatory and the Academia Sinica Institute of
Astronomy and Astrophysics and is funded by the
Smithsonian Institution and the Academia Sinica.
14
The Nearby Luminous Infrared Galaxy Sample
15
Science Goals of the Survey

• Determine the distributions, kinematics, and
  physical conditions of dense molecular gas in
  U/LIRGs
• Determine the spatial distribution of dust in
  U/LIRGs
• Constrain the origin of nuclear OH megamasers
• Determine how the gas properties change as the
  interaction progresses
• Compare the properties of the dense gas in local
  ULIRGs with the high-redshift submillimeter
  sources

16
Centrally compact CO 3-2 emission
I105652448
Mrk231
Mrk273
UGC5101
Arp55
(HST images of Arp55 and I105652448 from
Evans, Vavilkin, et al., 2009, in prep.)
17
Velocity Fields within Rlt1 kpc
Mrk231
I105652448
Mrk273
UGC5101
Arp55(NE)
Arp55(SW)
18
Velocity dispersions within Rlt1 kpc
19
But some systems are very extended

• CO emission in VV114 shows three peaks spaced
  over 4 kpc (10)
• 5 out of 14 galaxies in our sample show two or
  more components

20
Molecular gas in merging galaxies
21
Luminous Infrared Galaxies with the Submillimeter
Array

• What are Luminous Infrared Galaxies?
• An SMA Legacy Project Gas Morphology and
  Dynamics in U/LIRGs
• Gas-to-dust ratio in central kpc
• Comparison to high-redshift submillimeter
  galaxies
• Future work, NGLS, and ALMA

22
850 ?m continuum overlaid on CO3-2
Mrk273
I105652448
Mrk231
Contours are 2,3,4 X 5 mJy/beam Field of view
4x4. All sources detected at 4 sigma or better.
UGC5101
Arp55(NE)
23
The Gas to Dust Mass Ratio

• Mdust assumes ? 0.9 cm2/g and Tdust from
  modified blackbody fit to global data from 60 to
  800 ?m (cf. Klaas et al. 2001)
• M(H2) 0.8 L(CO1-0) (Downes Solomon 1998)
  assume CO3-2/1-00.5 (our data)
• Calculate gas to dust ratio in central beam only
  (CO much more sensitive than continuum per unit
  mass)
• Average gas/dust ratio 120 /- 30
• Standard deviation 110 significant scatter

24
Peak H2 surface density correlates with LFIR/MH2
(Scoville et al. 1991)
25
Peak H2 surface density correlates with LFIR/MH2
(Scoville et al. 1991)
26
With more uniform spatial resolution, correlation
disappears
Log(LFIR/MH2) (Lo/Mo)
Log(?H2) (Mo pc-2)
27
Do see a correlation of peak H2 surface density
with LFIR
Log(?H2)
Log(LFIR)
28
Implications for star formation

• No obvious correlation of star formation
  efficiency (LFIR/MH2) with peak H2 surface
  density
• Possible correlation of star formation rate with
  peak H2 surface density
• Suggests increased star formation rate/AGN
  activity in U/LIRGs is due to increased
  availability of fuel in central kiloparsec

29
Extremely high central gas surface densities

• Peak gas surface densities range from 103 to 104
  Mo/pc2 inside 0.5-1.2 kpc2 area
• AV70-700 mag
• Average volume density at peak range from nH
  20 to 300 cm-3
• Estimated as (gas surface density) / (beam
  radius)
• Average density is comparable to a GMC, but
  volume is 103-106 times larger
• 1 kpc versus 10-100 pc

30
Luminous Infrared Galaxies with the Submillimeter
Array

• What are Luminous Infrared Galaxies?
• An SMA Legacy Project Gas Morphology and
  Dynamics in U/LIRGs
• Gas-to-dust ratio in central kpc
• Comparison to high-redshift submillimeter
  galaxies
• Future work, NGLS, and ALMA

31
High-redshift comparison sample

• Select high-redshift objects with high resolution
  observations in CO(3-2) line
• 12 submillimeter galaxies (SMGs) from z2.2-3.1
  (one at z1.3)
• 9 quasars from z2.3-2.8 (one at z6.4)
• 2 Lyman Break Galaxies (LBGs) at z2.7-3.1
• References for CO data
• SMGs Genzel et al. 2003, Downes Solomon 2003,
  Sheth et al. 2004, Greve et al. 2005, Tacconi et
  al. 2006, Iono et al. 2006
• Quasars Downes et al. 1995, Barvainis et al.
  1998, Guilloteau et al. 1999, Weiss et al. 2003,
  Walter et al. 2004, Beelin et al. 2004, Hainline
  et al. 2004, Solomon van den Bout 2005
• LBGS Baker et al. 2004, Coppin et al. 2007

32
CO(3-2) traces dense star forming gas

• Slope (0.92/-0.03) is similar to HCN (Gao
  Solomon 2004) and significantly steeper than
  CO(1-0) (Yao et al. 2003)

33
Relation between gas surface density and
far-infrared luminosity

• Gas surface densities in Mo/pc2
• 1400 350 U/LIRGs
• 2290 890 SMGs
• 4280 600 quasars
• Surface density correlates with far-infrared
  luminosity
• LCO(3-2) to M(H2) using M(H2)0.8LCO(3-2)
• assumes CO3-2/1-01
• Note surface densities are not corrected for
  inclination

34
Linewidths (FWHM) in four samples of galaxies

• Average linewidths (FWHM, km/s)
• 180 10 local galaxies
• 360 30 U/LIRGs
• 610 90 SMGs
• 310 50 quasars
• U/LIRG and quasar distributions similar (but no
  inclination corrections yet)

35
SMGs larger diameters and line widths
36
Star-forming galaxies at z2 (Bouché et al. 2007)

• SMGs have larger linewidths and are more compact
  than rest-frame optical and UV selected samples
  at z2
• Our work confirms local compact U/LIRGs fall in
  a similar part of the diagram to SMGs

37
Luminous Infrared Galaxies with the Submillimeter
Array

• What are Luminous Infrared Galaxies?
• An SMA Legacy Project Gas Morphology and
  Dynamics in U/LIRGs
• Gas-to-dust ratio in central kpc
• Comparison to high-redshift submillimeter
  galaxies
• Future work, NGLS, and ALMA

38
Further analysis of survey data

• Combine continuum fluxes with spectra from
  Spitzer to determine dust temperature, mass,
  fraction of large and small grains

Galliano et al. 2003
39
Further analysis (continued)

• Combine CO 3-2, 2-1, and 1-0, and 13CO 2-1, to
  determine the physical properties of the
  molecular gas

SMA data Petitpas et al. 2006 Spitzer image
Wang et al. 2004
40
Further analysis (cont.)

• Compare morphology and kinematics to numerical
  simulations to constrain merger age and establish
  a merger sequence
• Correlate changes in gas physical properties with
  merger stage
• Feed results on physical properties back into
  models to improve gas physics

Narayanan et al. 2006
41
The JCMT Nearby Galaxies Legacy Survey
NGC 4631
42
Star formation and gas depletion in 4 Virgo
spirals
NGC 4321 (M100)
NGC 4254 (M99)
(Wilson et al. 2008, ApJ, submitted)
NGC 4579 (M58)
NGC 4569 (M90)
43
Star formation rates 24 ?m H?
SFR recipe from Calzetti et al. 2007
All images are on same colour scale
44
Gas depletion time 1/SFE
NGC4254 0.7 Gyr
NGC4321 1.1 Gyr
NGC4569
Quite uniform gas depletion times when CO J3-2
used to trace mass of molecular gas
tgas Mmol/SFR
1.1 Gyr
45
Star formation laws in galaxies
(Warren, Wilson, et al., in prep)
NGC 3627
46
Star Formation Thresholds

• Schmidt-Kennicutt law applies above a critical
  gas surface density.
• What determines the gas surface density
  threshold?
• Q parameter - Kennicutt (1989), Martin
  Kennicutt (2001), based on Toomre (1964) disk
  stability model.

47
1/Q Plots HI only (top) and CO 3-2 only
(bottom)?
NGC 0628 NGC 3521 NGC 3627
48
NGC 3627
NH gt 5.6 x 1020 cm-2 1/Q gt ?
0.63 (Schayne 2004)
(Kennicutt 1989)
49
The Future The Atacama Large Millimeter Array

• Array of 50 x 12m radio telescopes in Chile
• Six receivers from 3 mm to 0.4 mm
• Angular resolution from 1 to 0.02 at 1.3 mm
• Velocity resolution up to 0.01 km/s and bandwidth
  up to 10,000 km/s
• sensitivity 0.4 mJy (5 sigma, 1.3 mm) in 1
  minute!
• ALMA construction completed by end of 2012
• First science from ALMA by 2011 !!

50
ALMA antennas in Chile
51
How to carry a 12 meter telescope
52
Technical Building at theArray Operations Site
53
ALMA Band 3 (100 GHz)
being built at Herzberg Institute of
Astrophysics in Victoria B.C.
Lens
Feed Horn
OMT
Pol0 2SB Mixer Assembly
Pol1 2SB Mixer Assembly
ALMA Requirement
IF Amplifiers and Isolators
4 K Stage
15 K Stage
300 K Vacuum Flange
80 K Stage
ALMA Requirement
54
Conclusions

• A large survey of warm dense molecular gas in
  nearby luminous infrared galaxies shows
• Gas to dust mass ratio very similar to Galaxy
• Very high central gas surface densities and
  volume densities
• Star formation rate (not efficiency) correlates
  with central gas surface density

• LCO(3-2) and LFIR correlated over 5 orders of
  magnitude
• CO(3-2) traces dusty star formation activity
• Star formation efficiency constant to within a
  factor of two

UGC5101
New, sensitive telescopes promise a bright future
for studying extreme star formation in galaxies!
55
The end
56
Massive Star Clusters in Arp 220
(HST ACS image)
Wilson et al 2006
57
Conclusions

• LCO(3-2) and LFIR correlated over 5 orders of
  magnitude
• CO(3-2) traces dusty star formation activity
• Star formation efficiency constant to within a
  factor of two

• Molecular gas disks in local U/LIRGs are more
  compact than SMGs and SMGs have broader line
  widths
• SMGs most similar to intermediate-stage mergers?
• broad lines due to violent mergers deep in
  massive halo potential
• Future Work
• Spatially and velocity resolved physical
  conditions in gas
• Comparison with merger simulations

58
ALMA Mass Function of Super-Giant Molecular
Complexes
SGMC mass function in the Antennae
Wilson et al. 2003
ALMA will let us study molecular clouds and
complexes in galaxies out to 200 Mpc - can
reach masses as small as 5x106 Mo at 200 Mpc
in just one hour (3 sigma)
59
The Nearby Luminous Infrared Galaxy Sample

• DS98 Downes Solomon 1998
• C compact configuration (2.1 at 330 GHz, 3.2
  at 220 GHz)
• E extended configuration (0.8 at 330 GHz, 1.3
  at 220 GHz)
• Spectral resolution 10-40 km/s

60
The Nearby Galaxies Legacy Survey Physical
Processes in Galaxies in the Local Universe

• Relative mass and physical properties of
  different dust components (Galliano et al. 2003)
• How reliable are integrated measurements of
  physical conditions in galaxies?
• Molecular gas and the gas-to-dust ratio
  (Neininger et al. 1996)
• Effect of galaxy morphology on the ISM
• Effect of dense cluster environments (Kenney
  Young 1989)
• Effect of metallicity on the ISM (Madden et al.
  2006)
• The local submillimetre luminosity function
  (Dunne et al. 2000)

61
Sample selection process

• Distances between 2 and 25 Mpc
• Declination gt -25 degrees
• Galactic latitudes b gt 25 degrees
• HI flux gt 3 Jy km/s
• Result 1150 galaxies!
• So increase HI flux limit to 6 Jy km/s and apply
  random sampling (for field galaxies (72) and
  Virgo spirals (36))
• Also observe all SINGS galaxies (with HI flux gt 3
  Jy km/s etc.)

62
Broader implications and environmental effects

• Gas depletion times (1/SFE) vary more when CO
  J1-0 used to trace M(H2)
• implies CO J3-2 is better tracer of dense gas
  involved in active star formation
• NGC4321 high SFR in nucleus balanced by high gas
  content
• NGC 4569 gradient in CO J3-2/1-0 line ratio
• Less warm/dense gas in southern half of galaxy
• effect of interaction with ICM? (i.e. Kenney et
  al. 2008)
• NGC4579 high SFR in nucleus likely due to AGN

63
Some (small) Virgo galaxies
NGC 4651
NGC 4298
NGC 4383
NGC 4647
64
CO J3-2/1-0 line ratios PnT
NGC4254
NGC4321
NGC4569
Whiter colours Higher line ratios Higher T
and/or n
65
The Galaxies

• NGC 0628 Face-on spiral, least luminous, fairly
  isolated, moderate SF, HI dominates gas content
  and is very extended.
• NGC 3521 Highly inclined, just outside group,
  moderate SF, highest HI mass.
• NGC 3627 Moderately inclined, very active, most
  luminous, distinctive barred spiral structure,
  interacting with neighbours, gas is dominated by
  H2.

66
CO 3-2 in NGC 0628
67
CO 3-2 in NGC 3521
68
2D Threshold Maps from CO HI

• Based on de Blok Walter (2006).
• Hydrogen gas surface density from our CO 3-2 plus
  THINGS HI (Walter et al., 2008)?
• HI rotation curve gives us ?.
• Sound speed assumed to be 4 km s-1.
• Where 1/Q gt a gas should be unstable. Assume a
  0.63 Kennicutt (1989).
• Compare to constant density n(H) 5.623 x 1020
  atoms cm-2 (Schayne 2004).

69
NGC 0628
70
NGC 0628
71
NGC 3521
72
NGC 3521
73
NGC 3627