Age-dating a Starburst:Age-dating a Starburst:Gemini/CIRPASS ObservationsGemini/CIRPASS Observations

of the Core of M83of the Core of M83

Age-dating a Starburst:Age-dating a Starburst:Gemini/CIRPASS ObservationsGemini/CIRPASS Observations

of the Core of M83of the Core of M83

Stuart Ryder & Robert Sharp Stuart Ryder & Robert Sharp AAOAAO

Johan Knapen Johan Knapen U. HertfordshireU. Hertfordshire

Lisa Mazzuca Lisa Mazzuca GSFCGSFC

Ian Parry Ian Parry U. CambridgeU. Cambridge

Circumnuclear Star FormationCircumnuclear Star FormationCircumnuclear Star FormationCircumnuclear Star Formation• Compact SF regions (“knots”) in ring/spiral < 1 kpc Compact SF regions (“knots”) in ring/spiral < 1 kpc

across.across.

• CSF most common in barred spirals.CSF most common in barred spirals.

• Bars “funnel” gas inwards, accumulates near Inner Bars “funnel” gas inwards, accumulates near Inner Lindblad Resonance (ILR): Lindblad Resonance (ILR): = = pp - - /2/2

• What triggers CSF?What triggers CSF?

– Critical gas density

– Spiral density wave

Random age spread

Age gradient

M83 (NGC 5236)M83 (NGC 5236)M83 (NGC 5236)M83 (NGC 5236)

AAT/IRIS2

HST/WFPC2F300WF547MF814W

Dyn/PhotCenter

50 pc

The HST ViewThe HST ViewThe HST ViewThe HST View

Harris et al. 2001, AJ, 122, 3046

Model: Starburst99Z=0.04, =2.35

Instantaneous Burst

AV=1old

young

Starburst Clock No. 1Starburst Clock No. 1Starburst Clock No. 1Starburst Clock No. 1• H recombination line (HH recombination line (H, Pa, Pa, Br, Br) equivalent widths.) equivalent widths.

• Leitherer et al. “Starburst 99” models:Leitherer et al. “Starburst 99” models:

Instantaneous Burst Continuous SFInstantaneous Burst Continuous SF

Starburst Clock No. 2Starburst Clock No. 2Starburst Clock No. 2Starburst Clock No. 2• CO band (2.29 CO band (2.29 m, 1.62 m, 1.62 m) spectroscopic index.m) spectroscopic index.

• Leitherer et al. “Starburst 99” models:Leitherer et al. “Starburst 99” models:

Instantaneous Burst Continuous SFInstantaneous Burst Continuous SF

The CIRPASS ViewThe CIRPASS ViewThe CIRPASS ViewThe CIRPASS View

The CIRPASS ViewThe CIRPASS ViewThe CIRPASS ViewThe CIRPASS View

Knot-by-knot analysisKnot-by-knot analysisKnot-by-knot analysisKnot-by-knot analysis

Region AnalysisRegion AnalysisRegion AnalysisRegion Analysis

Pa 1.28 m

Inside-out, or Outside-in?Inside-out, or Outside-in?Inside-out, or Outside-in?Inside-out, or Outside-in?

[Fe II] 1.64m

Sequential Triggering in M100Sequential Triggering in M100Sequential Triggering in M100Sequential Triggering in M100

SummarySummarySummarySummary• Photometry gives an incomplete/ambiguous age picture.Photometry gives an incomplete/ambiguous age picture.

• NIR IFU spectroscopy less biased by extinction and NIR IFU spectroscopy less biased by extinction and selection effects.selection effects.

• Multiple spectral line diagnostics help constrain Star Multiple spectral line diagnostics help constrain Star Formation Formation HistoryHistory..

• Clear azimuthal age gradients in M83 and M100 provide Clear azimuthal age gradients in M83 and M100 provide best evidence yet for sequential triggering via spiral best evidence yet for sequential triggering via spiral density wave-induced shock.density wave-induced shock.

• Ideal project for NIR MOS: GNIRS IFU will have Ideal project for NIR MOS: GNIRS IFU will have 3.33.3" " 4.8" FOV at 0.15" sampling, R=1700, full 4.8" FOV at 0.15" sampling, R=1700, full KK window includes Br window includes Br and CO (2,0) bands. and CO (2,0) bands.

“The cube is not enough”