Age-dating a Starburst: Gemini/CIRPASS Observations of the Core of M83 Stuart Ryder & Robert Sharp AAO Johan Knapen U. Hertfordshire Lisa Mazzuca GSFC Ian Parry U. Cambridge

Circumnuclear Star Formation Compact SF regions (“knots”) in ring/spiral < 1 kpc across.Compact SF regions (“knots”) in ring/spiral < 1 kpc across. CSF most common in barred spirals.CSF most common in barred spirals. Bars “funnel” gas inwards, accumulates near Inner Lindblad Resonance (ILR):  =  p -  /2Bars “funnel” gas inwards, accumulates near Inner Lindblad Resonance (ILR):  =  p -  /2 What triggers CSF?What triggers CSF? –Critical gas density –Spiral density wave  Random age spread  Age gradient

M83 (NGC 5236) AAT/IRIS2 HST/WFPC2 F300W F547M F814W Dyn/Phot Center 50 pc

The HST View Harris et al. 2001, AJ, 122, 3046 Model: Starburst99 Z=0.04,  =2.35 Instantaneous Burst A V =1 old young

Starburst Clock No. 1 H recombination line (H , Pa , Br  ) equivalent widths.H recombination line (H , Pa , Br  ) equivalent widths. Leitherer et al. “Starburst 99” models:Leitherer et al. “Starburst 99” models: Instantaneous Burst Continuous SF Instantaneous Burst Continuous SF

Starburst Clock No. 2 CO band (2.29  m, 1.62  m) spectroscopic index.CO band (2.29  m, 1.62  m) spectroscopic index. Leitherer et al. “Starburst 99” models:Leitherer et al. “Starburst 99” models: Instantaneous Burst Continuous SF Instantaneous Burst Continuous SF

The CIRPASS View

Knot-by-knot analysis

Region Analysis

Pa  1.28  m Inside-out, or Outside-in? [Fe II] 1.64  m

Sequential Triggering in M100

SummarySummary Photometry gives an incomplete/ambiguous age picture.Photometry gives an incomplete/ambiguous age picture. NIR IFU spectroscopy less biased by extinction and selection effects.NIR IFU spectroscopy less biased by extinction and selection effects. Multiple spectral line diagnostics help constrain Star Formation History.Multiple spectral line diagnostics help constrain Star Formation History. Clear azimuthal age gradients in M83 and M100 provide best evidence yet for sequential triggering via spiral density wave-induced shock.Clear azimuthal age gradients in M83 and M100 provide best evidence yet for sequential triggering via spiral density wave-induced shock. Ideal project for NIR MOS: GNIRS IFU will have 3.3"  4.8" FOV at 0.15" sampling, R=1700, full K window includes Br  and CO (2,0) bands.Ideal project for NIR MOS: GNIRS IFU will have 3.3"  4.8" FOV at 0.15" sampling, R=1700, full K window includes Br  and CO (2,0) bands. “The cube is not enough”