Demographics of Local StarForming Galaxies and Starbursts

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Demographics of Local Star-Forming Galaxies and
Starbursts
M82 Spitzer/CXO/HST
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Primary Datasets

• Spitzer Infrared Nearby Galaxies Survey (SINGS)
• resolved UV ? radio mapping of 75 galaxies
• selection maximize diversity in type, mass,
  IR/optical
• 11 Mpc Ha/Ultraviolet Survey (11HUGS)
• resolved Ha, UV imaging, integrated/resolved IR
  of 400 galaxies
• selection volume-complete within 11 Mpc
  (S-Irr)
• Survey for Ionization in Neutral-Gas Galaxies
  (SINGG)
• resolved Ha, UV imaging, integrated/resolved IR
  of 500 galaxies
• selection HI-complete in 3 redshift slices
• Integrated Measurements
• Ha flux catalogue (IR, UV) for gt3000 galaxies
  within 150 Mpc
• - integrated spectra (IR, UV) for 600 galaxies
  in same volume (Moustakas Kennicutt 2006, 2007)

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Thanks to S. Akiyama, J. Lee, C. Tremonti,
J. Moustakas, C. Tremonti (Arizona), J.
Funes (Vatican), S. Sakai (UCLA), L. van Zee
(Indiana) The SINGS Team RCK,
D. Calzetti, L. Armus, G. Bendo, C. Bot,
J. Cannon, D. Dale, B. Draine, C. Engelbracht, K.
Gordon, G. Helou, D. Hollenbach, T.
Jarrett, S. Kendall, L. Kewley, C. Leitherer, A.
Li, S. Malhotra, M. Meyer, E. Murphy, M.
Regan, G. Rieke, M. Rieke, H. Roussel, K.
Sheth, JD Smith, M. Thornley, F. Walter
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Spitzer Local Volume Legacy

• UV/Ha/IR census of local volume
• HST ANGST sample to 3.5 Mpc
• GALEX 11HUGS sampel to 11 Mpc

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The Starburst Bestiary
nuclear starbursts circumnuclear
starbursts clumpy irregular galaxies Ly-a
galaxies EA galaxies KA galaxies LBGs DRGs EROs
SCUBA galaxies extreme starbursts

• GEHRs
• SSCs
• HII galaxies
• ELGs
• CNELGs
• W-R galaxies
• BCGs
• BCDs
• LIGs, LIRGs
• ULIGs, ULIRGs
• LUVGs, UVLGs

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Demographics of Star-Forming Galaxies
Baseline 11 Mpc Ha Ultraviolet Survey
(11HUGS) - all known galaxies w/gas within
11 Mpc Ursa Major cluster - companion
GALEX Legacy survey coming Quantify SF
properties in terms of 3 observables

• absolute SFR (Mo/yr)
• from Ha corrected for NII, dust
• SFR density, intensity (Mo/yr/kpc2)
• defined as SFR/pR2SF
• correlates strongly with gas density, SF
  timescale
• normalized SFR/mass birthrate parameter b
• ratio of present SFR to average past SFR
• defined here globally integrated over galaxy
• primary evolutionary variable along Hubble
  sequence

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11HUGS/LVL Sample
R 100 pc
1 kpc
10 kpc
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11HUGS Sample HaGS Goldmine Virgo Sample
(James et al. 2003 Gavazzi et al. 2003)
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SFR 5 Mo/yr
Gronwall 1998
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LIGs, ULIGs (Dopita et al., Soifer et al,
Scoville et al)
merger-driven inflows, starbursts
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Martin 2005, ApJ, 619, L59
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Mgas/tHubble
Mgas/tdyn
1 O5V/3_Myr
Meurer limit
0.5 _at_ 4 Mpc
Sgas/tHubble
Scrit
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Lecture 4 Begins Here
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Contributions to the global star formation budget
IR-luminous 5-8 circumnuclear
3-4 BCGs, ELGs 5-8
Total fraction 10-20
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1010
1011 Mo
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11MPC BCGs (Gil de Paz et al. 2003)
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Disk SF Global Trends
Kennicutt 1998, ARAA, 36, 189
Bendo et al. 2002, AJ, 124, 1380
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Kennicutt, Tamblyn, Congdon 1994, ApJ, 435, 22
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Sandage 1986, AA, 161, 89
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Kennicutt 1998, ARAA, 36, 189
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Bell, de Jong 2000, MNRAS, 312, 497
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SFR increase reflects an increase in frequency of
SF events, and a shift in the mass spectrum of
single events
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• Gas consumption
• typical timescales for depletion few Gyr
• stellar recycling of gas is significant factor!

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Brinchmann et al. 2004, MNRAS, 351, 1151
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blue sequence red sequence
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Kauffmann et al. 2003, MNRAS, 341, 54
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Lee Kennicutt, in preparation
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Disk SFRs Main Results
Kennicutt 1998, ARAA, 36, 189 Brinchmann et al.
2004, MNRAS, 351, 1151

• spectra best fitted with IMF Salpeter for M gt
  1 Mo
• SF is ubiquitous when cold gas is present
• - lt4 S-Irr non-detects in Ha, nearly all show
  trace SF in UV
• average SFR/mass increases by 5-10x per type bin
  (S0 - Sa - Sb, etc)
• proportional changes in disk SF history with type
• - changes in frequency and characteristic mass
  of SF events
• large residual variation in SFR within a given
  type
• most variation in disk SFR vs B/D ratio
• more strongly correlated with mean gas density
• temporal SFR variations (bursts)
• strong bimodality seen in SFR/mass vs galaxy mass
• extension to dwarfs shows evidence for third mode
  
• radial gradients in disk age and metallicity

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Janice Lee, PhD thesis
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Disk Star Formation Rates and Histories

• evolutionary synthesis of integrated colors
• Tinsley 1968, ApJ, 151, 547
• Searle et al. 1973, ApJ, 179, 427
• Larson, Tinsley 1978, ApJ, 219, 46
• results
• disk colors consistent with sequence of constant
  age, IMF, Z, and variable SF history y(t)
• best fit for Salpeter IMF
• spectra fit with similar model sequence

Kennicutt 1983, ApJ, 272, 54
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Bruzual, Charlot 1993, ApJ, 405, 538
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starburst duty cycle in dwarf galaxies (Lee 2006)
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see poster by Lee et al.
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Application to Starburst Duty Cycles

• bursts produce 20-40 of present-day SF in dwarfs
• fraction of bursting dwarfs in same sample is
  5-10

• the galaxies are bursting 5-10 of the time
• average burst amplitude is 4-8x the
  background SFR

• typical burst durations are 10-100 Myr
• (e.g., Gallagher, Harris, Calzetti,
  Zaritsky, Hunter)
• - a typical burst lasts for 0.1-1 of
  Hubble time

• a typical galaxy bursts 10-20 times over a
  Hubble time, each time producing a few percent of
  its stars (every 500-1000 Myr)

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NGC 1512 (HST)
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NGC 1512 (GALEX FUV/NUV)
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Sakamoto et al. 1999, ApJ, 525, 691
Kormendy Kennicutt 2004, ARAA, 42, 603
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M82 NGC 3034
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Lo et al. 1987, ApJ, 312, 574
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IR-luminous galaxies
ELS limit
normal galaxies
Kennicutt 1998, ARAA, 36, 189
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Circumnuclear Star Formation - Trends with Type
ellipticals too?! Yi et al. 2005, ApJ, 619, L111
Ho et al. 1997, ApJ, 487, 595
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Borne et al. 2000, ApJ, 529, L77
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Contributions to the global star formation budget
IR-luminous 5-8 circumnuclear
3-4 BCGs, ELGs 5-8
Total fraction 10-20
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total
IR-luminous starbursts
LFloch et al. 2005, ApJ, 632, 169
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The Star Formation Law
starbursts
normal galaxies
Kennicutt 1998, ApJ, 498, 541
Gao, Solomon 2004, ApJ, 606, 271
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Basic Observations

• Galaxies exhibit an immense diversity in star
  formation properties, varying by gt107 in absolute
  SFR, SFR/mass and SFR/area.
• Over this range the SFR/area is correlated with
  gas surface density, following a truncated
  Schmidt power law with index N 1.4 -0.1
• the correlation of with dense gas (e.g., HCN) is
  roughly linear
• The Schmidt law shows a turnover below a
  threshold surface density that varies between
  galaxies.
• in gas-rich, actively star-forming galaxies this
  transition is seen as a radial transition in the
  SFR/area
• some gas-poor disks reside in the threshold
  regime at all radii

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Scaling Laws
starbursts
normal galaxies
Kennicutt 1998, ApJ, 498, 541
Gao, Solomon 2004, ApJ, 606, 271
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Crothswaite et al. 2003
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Martin Kennicutt 2001, ApJ, 555, 301
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starburst galaxies
SFR surface density
normal galaxies
HIH2 mass surface density
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NGC 1291
Blue Carnegie Atlas Sandage Bedke 1994
Ha R SINGG survey Meurer et al. 2006
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Questions Schmidt Law

• Is the Schmidt law correlation really this good?
• do all galaxies follow the same Schmidt law?
• is the scatter driven by a second parameter?
• Is the global Schmidt law the result of a more
  fundamental underlying SF scaling law?
• over what range of physical scales is the law
  valid?
• Is the SFR correlated more strongly with the
  total (atomic molecular) surface density or
  with the molecular surface density alone?
• What is the physical origin of the relation?

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Schmidt law SFR vs gas density power law
Silk law SFR vs gas
density/dynamical time
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Questions

• Is the correlation really this good?
• do all galaxies follow the same Schmidt law?
• is the scatter driven by a second parameter?
• Is the Schmidt law the result of a more
  fundamental underlying SF scaling law?
• over what range of physical scales is the law
  valid?
• Is the SFR correlated more strongly with the
  total (atomic molecular) surface density or
  with the molecular surface density alone?
• What is the physical origin of the relation?

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Questions Thresholds

• Do the observed Ha edges of galaxies trace
  proportional changes in the SFR/area?
• Does the SFR in the sub-threshold regime follow a
  (modified) Schmidt law? Or is it triggered
  entirely by local compression events?
• What is the physical nature of the threshold?

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The Global Schmidt Law Revisited

• analyze galaxies with spatially-mapped star
  formation (Ha, Pa, FIR), HI, and CO
• enlarged, diversified samples
• normal galaxy sample 3x larger
• larger ranges in gas and SFR densities
• large subsamples of circumnuclear starbursts,
  low-metallicity galaxies incorporated
• densities averaged within active SF regions
• explicit corrections for NII, extinction
• point-by-point analysis of SINGS BIMA SONG
  galaxies

Work in progress!
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Kennicutt 1998, ApJ, 498, 541
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metal-poor dwarf galaxies
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The Spatially Resolved Star Formation Law in M51
Kennicutt et al. 2007, ApJ, submitted
FUV, Ha, 24mm
- Use spatially-resolved measures of CO, HI,
and SFR to characterize SFR vs gas surface
density relation on a point-by-point basis -
Use combinations of Ha Pa and Ha 24 mm
emission to correct for extinction in SFR
measurements - Probe scales from 300 - 1850 pc
(IR/HII regions to unbiased sampling of the
disk)
Calzetti et al. 2005, ApJ, 633, 871
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M51 BIMA SONG Survey Helfer et al. 2003
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NGC 6946 THINGS VLA HI Survey F. Walter et al.
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Scoville et al. 2000, AJ, 122, 3017
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GALEX FUV NUV (1500/2500 A)
Ha R
IRAC 8.0 mm
MIPS 24 mm
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Local Schmidt Law in M51
Kennicutt et al. 2006, in prep
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Tentative Conclusions

• The disk-averaged Schmidt law in galaxies is
  rooted in a local relationship that persists to
  scales of lt500 pc
• In M51 the SF density is tightly coupled to the
  local H2 surface density, and not with HI density
• A kinematic star formation law does not seem to
  extend as well to local scales
• The disk-averaged SF law is confirmed with
  more/better observations. Some metal-poor
  galaxies lie systematically above the mean
  relation.

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Extra Slides
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Star Formation Rates and Histories

• synthesis models mainly sensitive to ratio of
  main sequence to red giant stars --gt ratio of
  current star formation rate (SFR) to average past
  rate (b y0/lty(t)gt)

• most sensitive measurements from spectral
  features that directly trace young population,
  combined with color constraints
• - UV continuum fluxes
• - nebular recombination lines (--gt ionizing
  stellar continuum)
• - thermal dust emission (10-200 mm)

Kennicutt 1989, ARAA, 36, 189
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Michigan Spectral Catalog Vols 1-3
Kron 1982, Vistas Astron, 26, 37
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Kennicutt 1992, ApJS, 79, 255
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30 Doradus
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Sbc, Sc, Scd, Sd
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S0/a, Sa, Sab, Sb
bar-driven inflows, circumnuclear starbursts
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Sdm, Sm, Im, I0 BCGs (Gil de Paz et al. 2003)
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NGC 1365 (HST)
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NGC 3885 Sa
NGC 7690 Sab
NGC 986 SBb
NGC 3177 Sb
NGC 5806 Sb
NGC 4030 Sbc
Examples of pseudobulges Kormendy
Kennicutt 2004, ARAA, 42, 603
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Example completeness of z0 prism surveys
(UCM)
Early results suggest that prism surveys miss
40-55 of local SF