Demographics of Local StarForming Galaxies and Starbursts M

Demographics of Local Star-Forming Galaxies and Starbursts M 82: Spitzer/CXO/HST

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 (11 HUGS) – 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 >3000 galaxies within 150 Mpc - integrated spectra (+IR, UV) for ~600 galaxies in same volume (Moustakas & Kennicutt 2006, 2007)

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

Spitzer Local Volume Legacy • UV/Ha/IR census of local volume • HST ANGST sample to 3. 5 Mpc • GALEX 11 HUGS sampel to 11 Mpc

The Starburst Bestiary GEHRs nuclear starbursts SSCs circumnuclear starbursts HII galaxies clumpy irregular galaxies ELGs Ly-a galaxies CNELGs E+A galaxies W-R galaxies K+A galaxies BCGs LBGs BCDs DRGs LIGs, LIRGs EROs ULIGs, ULIRGs SCUBA galaxies LUVGs, UVLGs extreme starbursts

Demographics of Star-Forming Galaxies Baseline: 11 Mpc Ha + Ultraviolet Survey (11 HUGS) - 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/kpc 2) – defined as SFR/p. R 2 SF – 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

11 HUGS/LVL Sample R = 100 pc 1 kpc 10 kpc

11 HUGS Sample + Ha. GS + Goldmine Virgo Sample (James et al. 2003; Gavazzi et al. 2003)

SFR* ~5 Mo/yr Gronwall 1998

LIGs, ULIGs (Dopita et al. , Soifer et al, Scoville et al) merger-driven inflows, starbursts

Martin 2005, Ap. J, 619, L 59

Mgas/t. Hubble Mgas/tdyn 1 O 5 V/3_Myr Meurer limit ” 5. 0 @ 4 c p M Sgas/t. Hubble Scrit

Lecture 4 Begins Here

Contributions to the global star formation budget IR-luminous: ~5 -8% circumnuclear: ~3 -4% BCGs, ELGs: ~5 -8% Total fraction ~10 -20%

108 109 1010 1011 Mo

11 MPC + BCGs (Gil de Paz et al. 2003)

Disk SF – Global Trends Kennicutt 1998, ARAA, 36, 189 Bendo et al. 2002, AJ, 124, 1380

Kennicutt, Tamblyn, Congdon 1994, Ap. J, 435, 22

Sandage 1986, A&A, 161, 89

Kennicutt 1998, ARAA, 36, 189

Bell, de Jong 2000, MNRAS, 312, 497

SFR increase reflects an increase in frequency of SF events, and a shift in the mass spectrum of single events

• Gas consumption – typical timescales for depletion ~few Gyr – stellar recycling of gas is significant factor!

Brinchmann et al. 2004, MNRAS, 351, 1151

blue sequence red sequence

Kauffmann et al. 2003, MNRAS, 341, 54

Lee & Kennicutt, in preparation

Disk SFRs: Main Results Kennicutt 1998, ARAA, 36, 189 Brinchmann et al. 2004, MNRAS, 351, 1151 • spectra best fitted with IMF ~ Salpeter for M* > 1 Mo • SF is ubiquitous when cold gas is present - <4% S-Irr non-detects in Ha, nearly all show trace SF in UV • average SFR/mass increases by 5 -10 x per type bin (S 0 - 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

Janice Lee, Ph. D thesis

Disk Star Formation Rates and Histories • evolutionary synthesis of integrated colors Tinsley 1968, Ap. J, 151, 547 Searle et al. 1973, Ap. J, 179, 427 Larson, Tinsley 1978, Ap. J, 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, Ap. J, 272, 54

Bruzual, Charlot 1993, Ap. J, 405, 538

starburst duty cycle in dwarf galaxies (Lee 2006)

see poster by Lee et al.

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 -8 x 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)

NGC 1512 (HST)

NGC 1512 (GALEX FUV/NUV)

Kormendy & Kennicutt 2004, ARAA, 42, 603 Sakamoto et al. 1999, Ap. J, 525, 691

M 82 NGC 3034

Lo et al. 1987, Ap. J, 312, 574

IR-luminous galaxies ELS limit normal galaxies Kennicutt 1998, ARAA, 36, 189

Circumnuclear Star Formation - Trends with Type ellipticals too? ! Yi et al. 2005, Ap. J, 619, L 111 Ho et al. 1997, Ap. J, 487, 595

Borne et al. 2000, Ap. J, 529, L 77

Contributions to the global star formation budget IR-luminous: ~5 -8% circumnuclear: ~3 -4% BCGs, ELGs: ~5 -8% Total fraction ~10 -20%

total IR-luminous starbursts L’Floch et al. 2005, Ap. J, 632, 169

The Star Formation Law starbursts normal galaxies Kennicutt 1998, Ap. J, 498, 541 Gao, Solomon 2004, Ap. J, 606, 271

Basic Observations • Galaxies exhibit an immense diversity in star formation properties, varying by >107 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

Scaling Laws starbursts normal galaxies Kennicutt 1998, Ap. J, 498, 541 Gao, Solomon 2004, Ap. J, 606, 271

Crothswaite et al. 2003

Martin & Kennicutt 2001, Ap. J, 555, 301

SFR surface density starburst galaxies normal galaxies HI+H 2 mass surface density

NGC 1291 Blue: Carnegie Atlas Sandage & Bedke 1994 Ha + R: SINGG survey Meurer et al. 2006

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?

“Schmidt law”: SFR vs gas density power law “Silk law”: SFR vs gas density/dynamical time

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?

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?

The Global Schmidt Law Revisited • analyze galaxies with spatiallymapped star formation (Ha, Pa, FIR), HI, and CO • enlarged, diversified samples – normal galaxy sample 3 x 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 W n i k or ! s s e r g pro

Kennicutt 1998, Ap. J, 498, 541

metal-poor dwarf galaxies

The Spatially Resolved Star Formation Law in M 51 Kennicutt et al. 2007, Ap. J, submitted FUV, Ha, 24 mm - 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, Ap. J, 633, 871

M 51: BIMA SONG Survey Helfer et al. 2003

NGC 6946– THINGS VLA HI Survey F. Walter et al.

Scoville et al. 2000, AJ, 122, 3017

GALEX FUV + NUV (1500/2500 A) IRAC 8. 0 mm Ha + R MIPS 24 mm

Local Schmidt Law in M 51 Kennicutt et al. 2006, in prep

Tentative Conclusions • The disk-averaged Schmidt law in galaxies is rooted in a local relationship that persists to scales of <500 pc • In M 51 the SF density is tightly coupled to the local H 2 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.

Extra Slides

Star Formation Rates and Histories • synthesis models mainly sensitive to ratio of main sequence to red giant stars --> ratio of current star formation rate (SFR) to average past rate (b = y 0/<y(t)>) • most sensitive measurements from spectral features that directly trace young population, combined with color constraints - UV continuum fluxes - nebular recombination lines (--> ionizing stellar continuum) - thermal dust emission (10 -200 mm) Kennicutt 1989, ARAA, 36, 189